EP2602471B1 - Internal combustion engine with a fuel supply system - Google Patents

Internal combustion engine with a fuel supply system Download PDF

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Publication number
EP2602471B1
EP2602471B1 EP12008129.4A EP12008129A EP2602471B1 EP 2602471 B1 EP2602471 B1 EP 2602471B1 EP 12008129 A EP12008129 A EP 12008129A EP 2602471 B1 EP2602471 B1 EP 2602471B1
Authority
EP
European Patent Office
Prior art keywords
pressure
internal combustion
combustion engine
fuel
damping
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
EP12008129.4A
Other languages
German (de)
French (fr)
Other versions
EP2602471A3 (en
EP2602471A2 (en
Inventor
Wolfgang Layher
Christopher Tost
Martin Rieber
Arno Kinnen
Michael Dietenberger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Andreas Stihl AG and Co KG
Original Assignee
Andreas Stihl AG and Co KG
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Application filed by Andreas Stihl AG and Co KG filed Critical Andreas Stihl AG and Co KG
Publication of EP2602471A2 publication Critical patent/EP2602471A2/en
Publication of EP2602471A3 publication Critical patent/EP2602471A3/en
Application granted granted Critical
Publication of EP2602471B1 publication Critical patent/EP2602471B1/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M69/00—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel
    • F02M69/46—Details, component parts or accessories not provided for in, or of interest apart from, the apparatus covered by groups F02M69/02 - F02M69/44
    • F02M69/54—Arrangement of fuel pressure regulators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/0011—Constructional details; Manufacturing or assembly of elements of fuel systems; Materials therefor
    • F02M37/0023—Valves in the fuel supply and return system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M1/00—Carburettors with means for facilitating engine's starting or its idling below operational temperatures
    • F02M1/16—Other means for enriching fuel-air mixture during starting; Priming cups; using different fuels for starting and normal operation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/0047—Layout or arrangement of systems for feeding fuel
    • F02M37/007—Layout or arrangement of systems for feeding fuel characterised by its use in vehicles, in stationary plants or in small engines, e.g. hand held tools
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/04—Feeding by means of driven pumps
    • F02M37/16—Feeding by means of driven pumps characterised by provision of personally-, e.g. manually-, operated pumps

Definitions

  • the invention relates to an internal combustion engine with a fuel supply device of the type specified in the preamble of claim 1.
  • a fuel pump for a two-stroke engine is known, which is followed by a pressure damper.
  • the pressure damper has a spring-loaded membrane.
  • the fuel-remote side of the damping membrane is acted upon by atmospheric pressure.
  • the position of the damping diaphragm depends on the fuel pressure. Especially at low fuel pressures, which are in the order of the atmospheric pressure, fluctuations in the fuel pressure can lead to very large deflections on the damping diaphragm, so that the damping diaphragm operates at a considerable distance from its central position. A sufficient damping of pressure fluctuations can not be guaranteed by sure.
  • From the EP 0 280 923 A2 shows a fuel system for a fuel injection multi-cylinder engine.
  • the injectors are supplied with fuel via a common fuel pipe.
  • the fuel pipe is connected via a fuel line to a fuel tank in which a pressure regulator is arranged.
  • the invention has for its object to provide an internal combustion engine with a fuel supply device of the generic type, which ensures a uniform fuel supply to the engine even at low fuel pressures.
  • the fuel supply device has a pressure regulator, which regulates the pressure of the pumped from the fuel pump to the injection valve fuel.
  • Pressure regulators are basically known in fuel systems.
  • the adjustment of the reference pressures means to choose the two reference pressures so that any pressure differences between the reference pressures in the system are taken into account, in particular compensated.
  • the first reference pressure and the second reference pressure advantageously change to the same extent, so that a pressure difference between the reference pressures remains the same and can be compensated.
  • the compensation of a pressure difference between the reference pressures can for example be done mechanically by appropriate interpretation of the stiffness of the membranes or corresponding spring preload.
  • the first and the second reference pressure can also be selected so that the two reference pressures change in operation in different ways.
  • the reference pressures are coordinated so that the uneven change is negligibly small, so does not affect the function, or that the unequal changes in the reference pressures are known and can be compensated, for example by electronic compensation.
  • By adjusting the reference pressures can be ensured in a very simple manner that the damping membrane works in normal operation in a central position and thus pressure fluctuations during operation can be well damped.
  • the coordination of the reference pressures of pressure regulator and pressure damper on each other is particularly advantageous in fuel systems that work with very low fuel pressure.
  • the fuel pressure is in the order of the ambient pressure.
  • the fuel pressure may be, for example, in the range of 0 to 2 bar, in particular in the range of 0 to 500 mbar above the ambient pressure.
  • the diaphragm of the pressure damper is designed very soft, so that even at low pressure fluctuations, a deflection of the membrane can be done.
  • the first reference pressure is equal to the second reference pressure.
  • a compensation of pressure differences of the reference pressures can be omitted.
  • the reference pressure may also be the pressure of the clean room of an air filter of the internal combustion engine.
  • Another pressure may be useful as a reference pressure.
  • the damping chamber is advantageously arranged in the flow path of the fuel from the fuel pump to the injection valve. Due to the permanent flow through the damping chamber, the accumulation of gas bubbles can be largely avoided. It may also be advantageous to arrange the damping chamber in the flow path of the fuel from the injection valve to a fuel tank of the fuel supply device. Via the flow connection of the injection valve with the fuel tank, uninjected fuel delivered to the injection valve is conveyed back to the fuel tank. Even with an arrangement of the damping chamber downstream of the injection valve, a permanent flow through the damping chamber is achieved.
  • the injection valve is arranged in a holder fixed to the internal combustion engine.
  • the holder is advantageously made of a heat-insulating material such as plastic, so that the heat transfer to the injection valve is low and so the formation of vapor bubbles can be prevented. This is particularly advantageous for reheating the internal combustion engine with the engine off. When the internal combustion engine is switched off, the cylinder of the engine is still hot, but no more cooling air is conveyed, so that the heat from the cylinder can heat the adjacent components. Due to the formation of the holder made of plastic is the Heat input into the injection valve is reduced.
  • the holder advantageously has a housing, wherein the damping chamber of the pressure damper is limited by the housing of the holder.
  • the pressure damper is integrated in particular in the housing of the holder.
  • the number of components to be mounted on the internal combustion engine can be kept low.
  • the integration of the pressure damper in the housing of the holder can also be realized in a simple way, a very small distance between the pressure damper and the injection valve.
  • the holder is arranged on a crankcase of the internal combustion engine and has an outlet channel for fuel, which opens into the crankcase interior.
  • the rear space of the pressure damper is advantageously connected via an opening with the reference pressure, in particular with the environment, which is covered air-permeable by a cover.
  • the cover prevents contamination of the opening. This is particularly useful when the internal combustion engine is used in a working device, in particular in a hand-held implement, which is exposed during operation dirt loads.
  • the cover is advantageously water-repellent. This is particularly provided when the internal combustion engine is used in an environment in which water is used, such as when used in a water-based cut-off machine.
  • the cover is advantageously a sintered metal screen. Such a metal mesh is permeable to air, but acts water repellent, so that it is avoided that water or other liquids can get into the rear space of the pressure damper.
  • the sintered metal screen also has a sufficiently high mechanical stability.
  • the free passage area of the cover is comparatively large, so that even with contamination of the cover still a passage of air from the environment is possible.
  • the pressure equalization through the cover can be done slowly, since only longer-term pressure changes, such as those caused by the heating of the air in the rear space, must be compensated.
  • the free passage area of the cover is advantageously at least approximately 2 times the area of the damping diaphragm which is acted upon by the reference pressure.
  • the damping chamber leads advantageously a connecting channel to the injection valve, wherein the length of the connecting channel from the damping chamber to the injection valve is very low.
  • the length of the connecting channel is advantageously at most 5 times the diameter of the connecting channel. Due to the comparatively short relative to the diameter of the connecting channel between the injection valve and pressure damper arranged liquid column is kept very low.
  • the injector must open and close very quickly. When closing the valve, a pressure wave is created in the fuel supply line and the fuel comes to a stop. If the valve reopens shortly thereafter, the entire fuel column must be accelerated again. It has been found that this acceleration takes too long for the short operating times customary in operation in high-speed internal combustion engines, so that a sufficient amount of fuel can not be supplied.
  • the arrangement of the pressure damper immediately upstream of the injection valve and the very short design of the connecting channel the amount of fuel to be accelerated can be kept very low, so that a sufficient fuel supply can be ensured during operation.
  • the damping diaphragm of the pressure damper is loaded by a spring in the direction of the damping chamber.
  • the spring defines the working area of the pressure damper.
  • the bias of the spring is particularly adjustable so that manufacturing tolerances can be easily compensated and an accurate adjustment of the pressure range in which the membrane works, is possible.
  • the spring also helps to accelerate the fuel column in the connection channel.
  • the pressure damper in the rear space and in the damping chamber has at least one stop for fixing an end position of the damping diaphragm.
  • the damping membrane advantageously has an outer edge. A small size can be achieved if the outer edge of the damping membrane is located in an imaginary plane, with an angle of less than 30 ° with a longitudinal central axis of the injection valve includes.
  • the imaginary plane extends approximately parallel to the longitudinal central axis of the injection valve.
  • the fuel pump has a pump housing.
  • the pressure regulator is advantageously arranged in a conventional diaphragm carburetor.
  • the pressure regulator has a control diaphragm, which limits a control chamber, wherein an inlet valve is arranged at the inlet into the control chamber, which is opened or closed depending on the position of the control diaphragm.
  • a rear space is advantageously formed, which is acted upon by the reference pressure.
  • the fuel pump advantageously has a pump diaphragm, which is acted upon by the fluctuating pressure of the crankcase interior.
  • Fig. 1 shows as an exemplary embodiment of a working device, in particular for a hand-held, portable working device, a power cutter 1.
  • the internal combustion engine with fuel supply device according to the invention can also be provided for other tools such as chainsaws, brushcutters, blowers or the like.
  • the cut-off machine 1 has a housing 2, on which a forwardly projecting arm 3 is fixed. At the free end of the boom 3, a cutting disc 4 is rotatably mounted, which is driven in rotation by a combustion engine 12 arranged in the housing 2. The cutting disk 4 is covered over more than half of its circumference by a protective cover 5.
  • the housing 2 comprises a hood 8, on which an upper handle 6 is formed. At the upper handle 6, a throttle lever 10 and a throttle lock 11 are pivotally mounted. At the rear of the housing 2 facing away from the cutting disk 4, an air filter cover 9 is fixed. At the blade 4 facing side of the housing 2, the housing 2 is overlapped by a handle tube 7.
  • the abrasive grinder 1 has feet 13 with which the grinder 1 can be placed on the floor or other support surface.
  • Fig. 2 shows the internal combustion engine 12 in detail.
  • the internal combustion engine 12 is a two-stroke engine. However, the engine 12 may also be a compound lubricated four-stroke engine.
  • the internal combustion engine 12 has a crankcase 14, on which further housing parts are formed.
  • the crankcase 14 defines a crankcase interior 31, in which a crankshaft 80 is rotatably mounted about a rotation axis 15.
  • the crankshaft 80 is connected via an unillustrated connecting rod with a in Fig. 2 connected piston 21 shown connected in dashed lines.
  • the piston 21 is reciprocally mounted in a cylinder 16 and controls an inlet 17, which opens in the region of the top dead center of the piston 21 into the crankcase interior 31.
  • the piston 21 defines a combustion chamber 22 formed in the cylinder 16.
  • the crankcase interior 31 is in the range of in Fig. 2 shown bottom dead center of the piston 21 via one or more transfer ports 19 connected to the combustion chamber 22.
  • the overflow channels 19 open with overflow windows 20 into the combustion chamber 22.
  • an overflow channel 19 can be divided into a plurality of branches, which open into the combustion chamber 22 with separate overflow windows 20, as in FIG Fig. 2 is shown.
  • From the combustion chamber 22 leads, an outlet 18, which is also slit-controlled by the piston 21 and at the in Fig. 2 shown position of the piston 21 is open at bottom dead center.
  • the internal combustion engine 12 For supplying combustion air, the internal combustion engine 12 has an intake passage 30, which is guided through a throttle housing 27.
  • a throttle element in the embodiment, a throttle valve 28, arranged on which the throttle lever 10 acts.
  • an injection valve is provided which in Fig. 2 not shown.
  • the injection valve is arranged in a receptacle 25 of a holder 24 on the crankcase 14.
  • the holder 24 at the in Fig. 1 shown usual Abstellposition arranged on a flat surface immediately below the throttle body 27 and fixed to the crankcase 14.
  • the holder 24 has an outlet channel 71 for fuel, which opens into the crankcase interior 31.
  • Adjacent to the holder 24, a mounting opening 23 is formed on the crankcase 14, which serves for mounting a pressure-temperature sensor and which is arranged in the parking position below the holder 24.
  • combustion air is sucked through the intake passage 30 into the crankcase interior 31 in the region of top dead center of the piston 21.
  • the injection valve supplies fuel into the crankcase interior 31.
  • the fuel / air mixture flows from the crankcase interior 31 via the or the overflow channels 19 and the overflow 20 in the combustion chamber 22 a.
  • the mixture is compressed in the combustion chamber 22 and ignited in the region of top dead center of the piston 21 by a spark plug, not shown.
  • the piston 21 is accelerated in the direction of the crankcase 14.
  • the exhaust gases escape from the combustion chamber 22 and fresh mixture from the crankcase interior 31 flows via the transfer port or passages 19 into the combustion chamber 22.
  • the piston 21 moves in the cylinder 16 in the direction of a cylinder longitudinal axis 29.
  • the cylinder longitudinal axis 29 is in the in Fig. 1 shown usual parking position of the cutting grinder 1 approximately perpendicular or slightly inclined to the vertical rake.
  • Fig. 3 shows the fuel supply device of the internal combustion engine 12 in detail.
  • the grinder 1 has a fuel tank 32 into which a suction head 33 protrudes.
  • the fuel supply device has a fuel pump 34 which has a pump chamber 38 bounded by a pump diaphragm 39.
  • fuel is sucked from the fuel tank 32 via the suction head 33 via a suction valve 37, which is designed as a check valve.
  • the fuel is conveyed via a downstream of the pump chamber 31 arranged pressure valve 41, which is also designed as a check valve, in a fuel chamber 52.
  • the pump diaphragm 39 is acted upon on its side facing away from the pump chamber 38 via an impulse line 40 with the fluctuating pressure of the crankcase interior 31.
  • the fuel pump 34 is arranged in a pump housing 51, in which a pressure regulator 35 is arranged.
  • the pressure regulator 35 is disposed downstream of the fuel pump 34.
  • the pressure regulator 35 has a control diaphragm 44, which separates a control chamber 43 from a rear chamber 47.
  • the control chamber 43 is connected via an inlet valve 42 to the fuel chamber 52 of the fuel pump 34.
  • the inlet valve 42 is of a Inlet needle formed, which is arranged on a lever 45.
  • the second end of the lever 45 is connected to the control diaphragm 44.
  • the inlet valve 42 opens and closes.
  • the control diaphragm 44 is loaded by a spring 46 in the direction of the control chamber.
  • the spring 46 is designed as a compression spring and arranged in the rear space 47.
  • the rear chamber 47 is acted upon via an opening 48 with a reference pressure, which is the ambient pressure in the embodiment.
  • a fuel strainer 49 is arranged, through which the fuel flows from the control chamber 43 into a fuel line 50.
  • the pressure damper 36 has a damping diaphragm 54, which separates a damping chamber 53 from a rear space 56.
  • the fuel from the fuel line 50 flows through the damping chamber 53.
  • the damping diaphragm 54 is acted upon by a spring 55 in the direction of the damping chamber 53.
  • the spring 55 is designed as a compression spring and arranged in the rear space 56.
  • the rear space 56 is acted upon via an opening 57 with the same reference pressure as the pressure regulator 35, in the embodiment with the ambient pressure.
  • the fuel reaches the injection valve 26.
  • the injection valve 26 supplies the fuel into the crankcase interior 31.
  • Fig. 4 shows the structural arrangement of the holder 24 and the pressure damper 36 on the circumference of the crankcase 14 in an obliquely cut, perspective view.
  • the holder 24 and the pressure damper 36 are in the direction of the axis of rotation 15 of the crankshaft side by side.
  • the holder 24 is adjacent to a starter housing 82, in which the starting device for the internal combustion engine 12 is arranged.
  • the starter housing 82 are also a centrifugal clutch and a Pulley arranged to drive the drive belt of the cutting disc 4.
  • the pressure damper 36 is adjacent to a Lüfterradgephinuse 81, in which rotates the fan of the engine and promotes cooling air.
  • a pressure range of the Lüfterradgepuruses 81 is via a channel 83, the in Fig. 4 is shown only schematically, connected to a cooling housing 84, in which the holder 24 and the pressure damper 36 are arranged. Via the channel 83, the holder 24 with the injection valve 26 and the pressure damper 36 is actively cooled.
  • Fig. 5 shows the design of the holder 24 in detail.
  • the holder 24 has a housing 59, which comprises a first housing part 60 and a second housing part 61.
  • a first fuel nozzle 63 in which the fuel line 50 is formed
  • a second fuel nozzle 64 in which the return line 58 is formed fixed.
  • a connecting channel 73 leads to the injection valve 26.
  • the connecting channel 73 opens at an annular space 85 on the circumference of the injection valve 26.
  • the annular space is connected via an in Fig. 7 shown inlet opening 72 connected to the interior of the injection valve 26.
  • the fuel leaves the injection valve 26 via the in Fig. 5 shown fuel port 70, which opens into the outlet channel 71.
  • the fuel opening 70 is opened and closed by the injection valve 26.
  • the rear space 56 is formed in the second housing part 61.
  • the region arranged immediately adjacent to the damping membrane 54 is connected to a region 86 of the damping chamber 53 via one or more connecting openings 62.
  • the area 86 has the opening 57 to the environment.
  • the opening 57 is covered by a cover 67, which is permeable to air and in particular water-repellent or impermeable to water.
  • the cover 67 is advantageously a sintered metal mesh.
  • the spring 55 is supported on a plug 65 which is held in a holder 66, for example screwed or pressed into this.
  • the position of the plug 65 in the holder 66 may be in the manufacture of the pressure damper 36 are changed.
  • the bias of the spring 55 and thus the position of the damping diaphragm 54 at the desired fuel pressure is adjustable.
  • the free passage area a of the cover 67 is significantly larger than the acted upon in the back space 56 surface of the damping diaphragm 54.
  • the free passage area a is advantageously at least twice, in particular at least 3 times to 10 times the directly pressurized with the reference pressure surface b of the damping diaphragm 54th Even with partial soiling of the cover 67, it is ensured that the ambient pressure is applied to the damping membrane 54.
  • the cover 67 the pressure between the environment and the rear space 56 can compensate. The pressure compensation can take place slowly, especially in the case of heavy contamination of the cover 67.
  • the damping diaphragm 54 is held on a retaining sleeve 69.
  • the area of the damping membrane 54 that is covered by the holding bushing 69 does not count towards the applied area b.
  • Fig. 7 shows the fixation of the damping membrane 54 in detail.
  • the damping membrane 54 has an inner edge 75 which is held between the retaining sleeve 69 and a retaining pin 68 pressed in from the opposite side.
  • the retaining pin 68 has a retaining edge 77 which presses the inner edge 75 of the damping membrane 54 against an edge of the retaining sleeve 69 and fixed so.
  • the outer edge 76 of the damping membrane 54 is clamped between the two housing parts 60 and 61 and lies in an imaginary plane 91.
  • the imaginary plane 91 extends parallel to a longitudinal central axis 92 of the injection valve 26.
  • the imaginary plane 91 closes with the longitudinal central axis 92 of the injection valve 26 at an angle which is less than about 30 °.
  • the retaining sleeve 69 has a support surface 74, on which one end of the spring 55 formed as a compression spring rests. The retaining sleeve 69 protrudes into the interior of the spring 55 and forms a guide for the spring 55. At its other end, the spring 55 is supported on the plug 65.
  • the connecting channel 73 is formed very short. As Fig. 7 shows, the connecting channel 73 has a length 1, which is only slightly larger than the diameter d of the connecting channel 73. The length 1 is advantageously at most 5 times the diameter d of the connecting channel 73. The length 1 is significantly less than the diameter of the damping diaphragm 54. The length 1 is measured from the exit from the damping chamber 53 until it enters the annular space 85.
  • Fig. 7 the damping membrane 54 is arranged in a first end position. In this end position of the retaining pin 68 is located on a arranged in the damping chamber 53 stop 78. This position of the damping diaphragm 54 results when the fuel in the damping chamber 53 is depressurized or no fuel is arranged in the damping chamber 53.
  • Fig. 8 the damping membrane 54 is shown in its central position. In this position, the damping diaphragm 54 is advantageously in operation.
  • the retaining pin 68 has a distance from the stop 78.
  • a stop 79 is formed, to which the support surface 74 at the in Fig. 8 shown center position also has a distance.
  • the operating pressure may be, for example, about 100 mbar overpressure relative to the ambient pressure.
  • Fig. 9 shows the damping membrane 54 in its other end position. In this position, the support surface 74 abuts the stop 79. This situation arises when the pressure of the fuel in the damping chamber 53 is too high and is for example about 130 mbar. By the stops 78 and 79 an excessive deflection of the damping membrane 54 is avoided. Good fuel damping is at the in Fig. 8 shown center position of the damping diaphragm 54 given. To ensure that the damping diaphragm 54 operates in its center position during operation, it is provided that in the rear space 56 of the pressure damper 36 and in the rear space 47 of the pressure regulator 35, the same reference pressure prevails. In the exemplary embodiment, this is the ambient pressure.
  • the reference pressure may also be another pressure, for example the pressure in the clean room of an air filter of the internal combustion engine 12.
  • the pressure regulator 35 and the pressure damper 36 operate with the same reference pressure, a vote of pressure regulator 35 and pressure damper 36 is given in a simple manner. Even with very low fuel pressures at which the spring 55 is designed very weak in the pressure damper 36, it can be ensured that the damping diaphragm 54 operates in operation in its central position and can dampen the resulting pressure fluctuations well.
  • Fig. 10 shows an embodiment of the crankcase 14 of a cutting grinder 1.
  • the same reference numerals as in the preceding figures indicate corresponding components.
  • the rear space 56 of the pressure damper 36 is not acted upon by the ambient pressure, but with the pressure in the Lüfterradgephase 81.
  • the opening 57 is connected via a channel 89, which is guided in the embodiment in a funnel 90, with a connection opening 88 in the Lüfterradgephase 81.
  • the connection opening 88 is arranged in the exemplary embodiment in an overpressure region of the fan wheel housing 81, so that the reference pressure of the pressure damper 36 during operation of the internal combustion engine 12 is higher than the ambient pressure.
  • connection opening 88 can also be arranged in a negative pressure region of the fan wheel housing 81.
  • the reference pressure of in Fig. 10 Pressure regulator 35, not shown, is the ambient pressure as shown in the first embodiment, so that the reference pressures of pressure regulator 35 and pressure damper 36 are different.
  • the different reference pressures of pressure regulator 35 and pressure damper 36 are compensated.
  • the spring 55 of the pressure damper 36 can be designed to be correspondingly weak or completely eliminated.
  • a compensation by a corresponding bias of the damping diaphragm 54 of the pressure damper 36 done. It may also be provided to neglect the differences in the reference pressures.
  • an electronic compensation of the difference of the reference pressures may be provided.
  • a digital pressure transducer which measures one or both reference pressures and electronically compensates for any differences in pressure.
  • an actuator may be provided which acts on the pressure damper according to the measured pressure differences and thus compensates the pressure differences. This can be done for example by mechanical adjustment of a contact surface of the spring 55. As a result, the bias of the spring 55 and thus the rest position of the damping diaphragm 53 is changed. Thus, pressure differences between the reference pressures can be compensated.
  • FIG. 11 shown embodiment of the fuel supply device of the cutting machine 1 ( Fig. 1 ).
  • the pressure in the return line 58 substantially corresponds to the pressure in the fuel line 50, in particular when the injection valve 26 is closed This will cause the in Fig. 11 embodiment shown achieves the same pressure damping as in the Fig. 3 shown embodiment.
  • the damping chamber 53 of the pressure damper 36 flows through the fuel, so that the formation of vapor bubbles is avoided.
  • the structure of the fuel supply from Fig. 11 corresponds - except for the arrangement of the pressure damper 36 - the structure of in Fig. 3 shown embodiment.
  • Like reference numerals denote corresponding elements.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fuel-Injection Apparatus (AREA)
  • High-Pressure Fuel Injection Pump Control (AREA)

Description

Die Erfindung betrifft einen Verbrennungsmotor mit einer Kraftstoffzuführeinrichtung der im Oberbegriff des Anspruchs 1 angegebenen Gattung.The invention relates to an internal combustion engine with a fuel supply device of the type specified in the preamble of claim 1.

Aus der DE 42 23 756 A1 ist eine Kraftstoffpumpe für einen Zweitaktmotor bekannt, der ein Druckdämpfer nachgeschaltet ist. Der Druckdämpfer besitzt eine federbeaufschlagte Membran. Die dem Kraftstoff abgewandte Seite der Dämpfungsmembran ist mit Atmosphärendruck beaufschlagt. Die Lage der Dämpfungsmembran ist abhängig vom Kraftstoffdruck. Vor allem bei niedrigen Kraftstoffdrücken, die in der Größenordnung des Atmosphärendrucks liegen, können Schwankungen des Kraftstoffdrucks zu sehr großen Auslenkungen an der Dämpfungsmembran führen, so dass die Dämpfungsmembran mit deutlichem Abstand von ihrer Mittellage arbeitet. Eine ausreichende Dämpfung von Druckschwankungen kann dadurch nicht sicher gewährleistet werden.From the DE 42 23 756 A1 is a fuel pump for a two-stroke engine is known, which is followed by a pressure damper. The pressure damper has a spring-loaded membrane. The fuel-remote side of the damping membrane is acted upon by atmospheric pressure. The position of the damping diaphragm depends on the fuel pressure. Especially at low fuel pressures, which are in the order of the atmospheric pressure, fluctuations in the fuel pressure can lead to very large deflections on the damping diaphragm, so that the damping diaphragm operates at a considerable distance from its central position. A sufficient damping of pressure fluctuations can not be guaranteed by sure.

Aus der EP 0 280 923 A2 geht ein Kraftstoffsystem für einen mit Kraftstoffeinspritzung arbeitenden Mehrzylindermotor hervor. Die Einspritzventile werden über ein gemeinsames Kraftstoffrohr mit Kraftstoff versorgt. Das Kraftstoffrohr ist über eine Kraftstoffleitung mit einem Kraftstofftank verbunden, in der ein Druckregler angeordnet ist.From the EP 0 280 923 A2 shows a fuel system for a fuel injection multi-cylinder engine. The injectors are supplied with fuel via a common fuel pipe. The fuel pipe is connected via a fuel line to a fuel tank in which a pressure regulator is arranged.

Der Erfindung liegt die Aufgabe zugrunde, einen Verbrennungsmotor mit einer Kraftstoffzuführeinrichtung der gattungsgemäßen Art zu schaffen, der eine gleichmäßige Kraftstoffzufuhr zum Verbrennungsmotor auch bei geringen Kraftstoffdrücken gewährleistet.The invention has for its object to provide an internal combustion engine with a fuel supply device of the generic type, which ensures a uniform fuel supply to the engine even at low fuel pressures.

Diese Aufgabe wird durch einen Verbrennungsmotor mit einer Kraftstoffzuführeinrichtung mit den Merkmalen des Anspruchs 1 gelöst.This object is achieved by an internal combustion engine with a fuel supply device having the features of claim 1.

Es ist vorgesehen, dass die Kraftstoffzuführeinrichtung einen Druckregler besitzt, der den Druck des von der Kraftstoffpumpe zum Einspritzventil geförderten Kraftstoffs regelt.It is provided that the fuel supply device has a pressure regulator, which regulates the pressure of the pumped from the fuel pump to the injection valve fuel.

Druckregler sind in Kraftstoffsystemen grundsätzlich bekannt. Um eine übermäßige Auslenkung der Dämpfungsmembran im Betrieb zu vermeiden, ist nun vorgesehen, den ersten Referenzdruck, mit dem der Rückraum des Druckdämpfers beaufschlagt ist, auf den zweiten Referenzdruck für den Druckregler abzustimmen. Die Abstimmung der Referenzdrücke bedeutet dabei, die beiden Referenzdrücke so zu wählen, dass eventuelle Druckunterschiede zwischen den Referenzdrücken im System berücksichtigt, insbesondere kompensiert werden. Dabei ändern sich der erste Referenzdruck und der zweite Referenzdruck im Betrieb vorteilhaft im gleichen Maße, so dass ein Druckunterschied zwischen den Referenzdrücken gleich bleibt und kompensiert werden kann. Die Kompensation eines Druckunterschieds zwischen den Referenzdrücken kann beispielsweise mechanisch durch entsprechende Auslegung der Steifigkeit der Membranen oder entsprechende Federvorspannung erfolgen. Auch eine elektronische Kompensation, beispielsweise durch eine Steuereinrichtung des Arbeitsgeräts kann vorgesehen sein. Der erste und der zweite Referenzdruck können auch so gewählt sein, dass die beiden Referenzdrücke sich im Betrieb auf unterschiedliche Weise ändern. Die Referenzdrücke sind dabei jedoch so aufeinander abgestimmt, dass die ungleichmäßige Änderung vernachlässigbar klein ist, die Funktion also nicht beeinträchtigt, oder dass die ungleichen Änderungen der Referenzdrücke bekannt sind und kompensiert werden können, beispielsweise durch elektronische Kompensation. Durch die Abstimmung der Referenzdrücke kann auf sehr einfache Weise sichergestellt werden, dass die Dämpfungsmembran im üblichen Betrieb in einer Mittellage arbeitet und dadurch Druckschwankungen im Betrieb gut gedämpft werden können.Pressure regulators are basically known in fuel systems. In order to avoid excessive deflection of the damping diaphragm during operation, it is now provided to match the first reference pressure, which is applied to the rear space of the pressure damper, to the second reference pressure for the pressure regulator. The adjustment of the reference pressures means to choose the two reference pressures so that any pressure differences between the reference pressures in the system are taken into account, in particular compensated. During operation, the first reference pressure and the second reference pressure advantageously change to the same extent, so that a pressure difference between the reference pressures remains the same and can be compensated. The compensation of a pressure difference between the reference pressures can for example be done mechanically by appropriate interpretation of the stiffness of the membranes or corresponding spring preload. An electronic compensation, for example by a control device of the working device can be provided. The first and the second reference pressure can also be selected so that the two reference pressures change in operation in different ways. However, the reference pressures are coordinated so that the uneven change is negligibly small, so does not affect the function, or that the unequal changes in the reference pressures are known and can be compensated, for example by electronic compensation. By adjusting the reference pressures can be ensured in a very simple manner that the damping membrane works in normal operation in a central position and thus pressure fluctuations during operation can be well damped.

Die Abstimmung der Referenzdrücke von Druckregler und Druckdämpfer aufeinander ist insbesondere bei Kraftstoffsystemen vorteilhaft, die mit sehr geringem Kraftstoffdruck arbeiten. Insbesondere liegt der Kraftstoffdruck in der Größenordnung des Umgebungsdrucks. Der Kraftstoffdruck kann beispielsweise im Bereich von 0 bis 2 bar, insbesondere im Bereich von 0 bis 500 mbar über dem Umgebungsdruck liegen. Bei einem so geringen Überdruck des Kraftstoffs ist die Membran des Druckdämpfers sehr weich ausgelegt, damit bereits bei geringen Druckschwankungen eine Auslenkung der Membran erfolgen kann. Bereits eine geringe Erhöhung oder Verringerung des Drucks im Rückraum des Druckdämpfers gegenüber dem Kraftstoffdruck ohne Kompensation der relativen Druckänderung kann dazu führen, dass die Dämpfungsmembran in eine Endlage gedrückt wird und aufgrund des erhöhten Gegendrucks keine Auslenkung der Dämpfungsmembran bei Druckschwankungen des Kraftstoffdrucks und damit keine Dämpfung der Druckschwankungen mehr möglich ist. Dies wird dadurch, dass der Referenzdruck der Kraftstoffpumpe auf den Referenzdruck des Druckdämpfers abgestimmt ist, vermieden.The coordination of the reference pressures of pressure regulator and pressure damper on each other is particularly advantageous in fuel systems that work with very low fuel pressure. In particular, the fuel pressure is in the order of the ambient pressure. The fuel pressure may be, for example, in the range of 0 to 2 bar, in particular in the range of 0 to 500 mbar above the ambient pressure. At such a low overpressure of the fuel, the diaphragm of the pressure damper is designed very soft, so that even at low pressure fluctuations, a deflection of the membrane can be done. Already a small increase or decrease in the pressure in the rear space of the pressure damper compared to the fuel pressure without compensation of the relative pressure change can cause the damping diaphragm is pressed into an end position and due to the increased back pressure no deflection of the damping diaphragm in pressure fluctuations of the fuel pressure and thus no damping of pressure fluctuations is possible. This is avoided by the fact that the reference pressure of the fuel pump is adjusted to the reference pressure of the pressure damper.

Vorteilhaft ist der erste Referenzdruck gleich dem zweiten Referenzdruck. Eine Kompensation von Druckunterschieden der Referenzdrücke kann dadurch entfallen. Es sind keine zusätzlichen Maßnahmen zur Abstimmung der Referenzdrücke aufeinander notwendig. Eine besonders einfache Gestaltung ergibt sich, wenn der erste Referenzdruck und der zweite Referenzdruck der Umgebungsdruck sind. Der Referenzdruck kann jedoch auch der Druck des Reinraums eines Luftfilters des Verbrennungsmotors sein. Auch ein anderer Druck kann als Referenzdruck zweckmäßig sein. Der Dämpfungsraum ist vorteilhaft im Strömungsweg des Kraftstoffs von der Kraftstoffpumpe zum Einspritzventil angeordnet. Durch das permanente Durchströmen des Dämpfungsraums kann das Ansammeln von Gasblasen weitgehend vermieden werden. Es kann auch vorteilhaft sein, den Dämpfungsraum im Strömungsweg des Kraftstoffs von dem Einspritzventil zu einem Kraftstofftank der Kraftstoffzuführeinrichtung anzuordnen. Über die Strömungsverbindung des Einspritzventils mit dem Kraftstofftank wird zum Einspritzventil geförderter, nicht eingespritzter Kraftstoff zurück zum Kraftstofftank gefördert. Auch bei einer Anordnung des Dämpfungsraums stromab des Einspritzventils wird eine permanente Durchströmung des Dämpfungsraums erreicht.Advantageously, the first reference pressure is equal to the second reference pressure. A compensation of pressure differences of the reference pressures can be omitted. There are no additional measures necessary to match the reference pressures to each other. A particularly simple design results when the first reference pressure and the second reference pressure are the ambient pressure. However, the reference pressure may also be the pressure of the clean room of an air filter of the internal combustion engine. Another pressure may be useful as a reference pressure. The damping chamber is advantageously arranged in the flow path of the fuel from the fuel pump to the injection valve. Due to the permanent flow through the damping chamber, the accumulation of gas bubbles can be largely avoided. It may also be advantageous to arrange the damping chamber in the flow path of the fuel from the injection valve to a fuel tank of the fuel supply device. Via the flow connection of the injection valve with the fuel tank, uninjected fuel delivered to the injection valve is conveyed back to the fuel tank. Even with an arrangement of the damping chamber downstream of the injection valve, a permanent flow through the damping chamber is achieved.

Vorteilhaft ist das Einspritzventil in einem am Verbrennungsmotor festgelegten Halter angeordnet. Der Halter ist vorteilhaft aus einem wärmeisolierenden Material wie beispielsweise Kunststoff gefertigt, so dass die Wärmeübertragung an das Einspritzventil gering ist und so die Bildung von Dampfblasen verhindert werden kann. Dies ist insbesondere für das Nachheizen des Verbrennungsmotors bei ausgeschaltetem Motor vorteilhaft. Bei ausgeschaltetem Verbrennungsmotor ist der Zylinder des Motors noch heiß, es wird jedoch keine Kühlluft mehr gefördert, so dass die Wärme aus dem Zylinder die angrenzenden Bauteile aufheizen kann. Durch die Ausbildung des Halters aus Kunststoff wird der Wärmeeintrag in das Einspritzventil verringert. Der Halter besitzt vorteilhaft ein Gehäuse, wobei der Dämpfungsraum des Druckdämpfers von dem Gehäuse des Halters begrenzt ist. Der Druckdämpfer ist insbesondere in das Gehäuse des Halters integriert. Dadurch kann die Anzahl der am Verbrennungsmotor zu montierenden Bauteile gering gehalten werden. Durch die Integration des Druckdämpfers in das Gehäuse des Halters kann außerdem auf einfache Weise ein sehr geringer Abstand zwischen dem Druckdämpfer und dem Einspritzventil realisiert werden. Vorteilhaft ist der Halter an einem Kurbelgehäuse des Verbrennungsmotors angeordnet und besitzt einen Austrittskanal für Kraftstoff, der in den Kurbelgehäuseinnenraum mündet.Advantageously, the injection valve is arranged in a holder fixed to the internal combustion engine. The holder is advantageously made of a heat-insulating material such as plastic, so that the heat transfer to the injection valve is low and so the formation of vapor bubbles can be prevented. This is particularly advantageous for reheating the internal combustion engine with the engine off. When the internal combustion engine is switched off, the cylinder of the engine is still hot, but no more cooling air is conveyed, so that the heat from the cylinder can heat the adjacent components. Due to the formation of the holder made of plastic is the Heat input into the injection valve is reduced. The holder advantageously has a housing, wherein the damping chamber of the pressure damper is limited by the housing of the holder. The pressure damper is integrated in particular in the housing of the holder. As a result, the number of components to be mounted on the internal combustion engine can be kept low. The integration of the pressure damper in the housing of the holder can also be realized in a simple way, a very small distance between the pressure damper and the injection valve. Advantageously, the holder is arranged on a crankcase of the internal combustion engine and has an outlet channel for fuel, which opens into the crankcase interior.

Der Rückraum des Druckdämpfers ist vorteilhaft über eine Öffnung mit dem Referenzdruck, insbesondere mit der Umgebung verbunden, die von einer Abdeckung luftdurchlässig abgedeckt ist. Die Abdeckung verhindert ein Verschmutzen der Öffnung. Dies ist insbesondere dann sinnvoll, wenn der Verbrennungsmotor in einem Arbeitsgerät, insbesondere in einem handgeführten Arbeitsgerät eingesetzt wird, das im Betrieb Schmutzbelastungen ausgesetzt ist. Die Abdeckung ist vorteilhaft wasserabweisend. Dies ist insbesondere dann vorgesehen, wenn der Verbrennungsmotor in einem Umfeld eingesetzt wird, in dem mit Wasser gearbeitet wird, wie beispielsweise beim Einsatz in einem mit Wasser arbeitenden Trennschleifer. Die Abdeckung ist vorteilhaft ein gesintertes Metallsieb. Ein solches Metallsieb ist für Luft durchlässig, wirkt jedoch wasserabweisend, so dass vermieden ist, dass Wasser oder andere Flüssigkeiten in den Rückraum des Druckdämpfers gelangen können. Das gesinterte Metallsieb besitzt außerdem eine ausreichend hohe mechanische Stabilität. Vorteilhaft ist die freie Durchtrittsfläche der Abdeckung vergleichsweise groß, so dass selbst bei Verschmutzung der Abdeckung noch ein Durchtritt von Luft aus der Umgebung möglich ist. Der Druckausgleich durch die Abdeckung kann dabei langsam erfolgen, da nur längerfristige Druckänderungen, wie sie beispielsweise aufgrund der Erwärmung der Luft im Rückraum entstehen, ausgeglichen werden müssen. Die freie Durchtrittsfläche der Abdeckung beträgt vorteilhaft mindestens etwa das 2fache der mit dem Referenzdruck beaufschlagten Fläche der Dämpfungsmembran.The rear space of the pressure damper is advantageously connected via an opening with the reference pressure, in particular with the environment, which is covered air-permeable by a cover. The cover prevents contamination of the opening. This is particularly useful when the internal combustion engine is used in a working device, in particular in a hand-held implement, which is exposed during operation dirt loads. The cover is advantageously water-repellent. This is particularly provided when the internal combustion engine is used in an environment in which water is used, such as when used in a water-based cut-off machine. The cover is advantageously a sintered metal screen. Such a metal mesh is permeable to air, but acts water repellent, so that it is avoided that water or other liquids can get into the rear space of the pressure damper. The sintered metal screen also has a sufficiently high mechanical stability. Advantageously, the free passage area of the cover is comparatively large, so that even with contamination of the cover still a passage of air from the environment is possible. The pressure equalization through the cover can be done slowly, since only longer-term pressure changes, such as those caused by the heating of the air in the rear space, must be compensated. The free passage area of the cover is advantageously at least approximately 2 times the area of the damping diaphragm which is acted upon by the reference pressure.

Von dem Dämpfungsraum führt vorteilhaft ein Verbindungskanal zum Einspritzventil, wobei die Länge des Verbindungskanals vom Dämpfungsraum bis zum Einspritzventil sehr gering ist. Die Länge des Verbindungskanals beträgt vorteilhaft höchstens das 5fache des Durchmessers des Verbindungskanals. Durch die bezogen auf den Durchmesser vergleichsweise kurze Ausbildung des Verbindungskanals wird die zwischen Einspritzventil und Druckdämpfer angeordnete Flüssigkeitssäule sehr gering gehalten. Im Betrieb muss das Einspritzventil sehr schnell öffnen und schließen. Beim Schließen des Ventils entsteht in der Kraftstoffzuleitung eine Druckwelle, und der Kraftstoff kommt zum Stehen. Wenn das Ventil bereits kurz darauf wieder öffnet, muss die gesamte Kraftstoffsäule erneut beschleunigt werden. Es hat sich gezeigt, dass diese Beschleunigung bei den im Betrieb bei schnelllaufenden Verbrennungsmotoren üblichen kurzen Schaltzeiten zu lange dauert, so dass keine ausreichende Kraftstoffmenge zugeführt werden kann. Durch die Anordnung des Druckdämpfers unmittelbar stromauf des Einspritzventils und die sehr kurze Ausbildung des Verbindungskanals kann die zu beschleunigende Kraftstoffmenge sehr gering gehalten werden, so dass eine ausreichende Kraftstoffzufuhr im Betrieb gewährleistet werden kann.Of the damping chamber leads advantageously a connecting channel to the injection valve, wherein the length of the connecting channel from the damping chamber to the injection valve is very low. The length of the connecting channel is advantageously at most 5 times the diameter of the connecting channel. Due to the comparatively short relative to the diameter of the connecting channel between the injection valve and pressure damper arranged liquid column is kept very low. During operation, the injector must open and close very quickly. When closing the valve, a pressure wave is created in the fuel supply line and the fuel comes to a stop. If the valve reopens shortly thereafter, the entire fuel column must be accelerated again. It has been found that this acceleration takes too long for the short operating times customary in operation in high-speed internal combustion engines, so that a sufficient amount of fuel can not be supplied. The arrangement of the pressure damper immediately upstream of the injection valve and the very short design of the connecting channel, the amount of fuel to be accelerated can be kept very low, so that a sufficient fuel supply can be ensured during operation.

Vorteilhaft ist die Dämpfungsmembran des Druckdämpfers von einer Feder in Richtung auf den Dämpfungsraum belastet. Die Feder gibt den Arbeitsbereich des Druckdämpfers vor. Die Vorspannung der Feder ist insbesondere einstellbar, so dass Fertigungstoleranzen einfach ausgeglichen werden können und eine genaue Einstellung des Druckbereichs, in dem die Membran arbeitet, möglich ist. Durch die Feder wird außerdem das Beschleunigen der Kraftstoffsäule im Verbindungskanal unterstützt.Advantageously, the damping diaphragm of the pressure damper is loaded by a spring in the direction of the damping chamber. The spring defines the working area of the pressure damper. The bias of the spring is particularly adjustable so that manufacturing tolerances can be easily compensated and an accurate adjustment of the pressure range in which the membrane works, is possible. The spring also helps to accelerate the fuel column in the connection channel.

Um ein übermäßiges Auslenken der Dämpfungsmembran zu vermeiden, ist vorgesehen, dass der Druckdämpfer im Rückraum und im Dämpfungsraum jeweils mindestens einen Anschlag zur Festlegung einer Endstellung der Dämpfungsmembran besitzt. Die Dämpfungsmembran besitzt vorteilhaft einen äußeren Rand. Eine geringe Baugröße kann erreicht werden, wenn der äußere Rand der Dämpfungsmembran in einer gedachten Ebene liegt, die mit einer Längsmittelachse des Einspritzventils einen Winkel von weniger als 30° einschließt. Vorteilhaft verläuft die gedachte Ebene etwa parallel zur Längsmittelachse des Einspritzventils.In order to avoid excessive deflection of the damping diaphragm, it is provided that the pressure damper in the rear space and in the damping chamber has at least one stop for fixing an end position of the damping diaphragm. The damping membrane advantageously has an outer edge. A small size can be achieved if the outer edge of the damping membrane is located in an imaginary plane, with an angle of less than 30 ° with a longitudinal central axis of the injection valve includes. Advantageously, the imaginary plane extends approximately parallel to the longitudinal central axis of the injection valve.

Vorteilhaft besitzt die Kraftstoffpumpe ein Pumpengehäuse. In dem Pumpengehäuse der Kraftstoffpumpe ist vorteilhaft auch der Druckregler angeordnet. Dadurch ergibt sich ein kompakter Aufbau. Der Druckregler ist vorteilhaft entsprechend einem Druckregler in einem üblichen Membranvergaser aufgebaut. Der Druckregler besitzt eine Regelmembran, die eine Regelkammer begrenzt, wobei am Einlass in die Regelkammer ein Einlassventil angeordnet ist, das in Abhängigkeit der Stellung der Regelmembran geöffnet oder geschlossen wird. An der der Regelkammer abgewandten Seite der Regelmembran ist vorteilhaft ein Rückraum ausgebildet, der mit dem Referenzdruck beaufschlagt ist. Die Kraftstoffpumpe besitzt vorteilhaft eine Pumpenmembran, die mit dem schwankenden Druck des Kurbelgehäuseinnenraums beaufschlagt ist.Advantageously, the fuel pump has a pump housing. In the pump housing of the fuel pump and the pressure regulator is advantageously arranged. This results in a compact design. The pressure regulator is advantageously constructed according to a pressure regulator in a conventional diaphragm carburetor. The pressure regulator has a control diaphragm, which limits a control chamber, wherein an inlet valve is arranged at the inlet into the control chamber, which is opened or closed depending on the position of the control diaphragm. On the side facing away from the control chamber of the control membrane, a rear space is advantageously formed, which is acted upon by the reference pressure. The fuel pump advantageously has a pump diaphragm, which is acted upon by the fluctuating pressure of the crankcase interior.

Ausführungsbeispiele der Erfindung werden im Folgenden anhand der Zeichnung erläutert. Es zeigen:

Fig. 1
eine schematische Darstellung eines Trennschleifers,
Fig. 2
einen Schnitt durch den Verbrennungsmotor des Trennschleifers aus Fig. 1,
Fig. 3
eine schematische Darstellung der Kraftstoffzuführeinrichtung des Verbrennungsmotors,
Fig. 4
einen Schnitt durch das Kurbelgehäuse des Trennschleifers und einen daran angeordneten Halter für das Einspritzventil,
Fig. 5
einen Schnitt durch den Halter,
Fig. 6
eine schematische Darstellung der Flächen von Abdeckung und Regelmembran in Richtung des Pfeils VI in Fig. 5,
Fig. 7
eine vergrößerte Schnittdarstellung des Druckdämpfers, wenn kein Kraftstoffdruck anliegt,
Fig. 8
einen Schnitt durch den Druckdämpfer im Betrieb,
Fig. 9
einen Schnitt durch den Druckdämpfer bei zu hohem Kraftstoffdruck,
Fig. 10
einen Schnitt durch das Kurbelgehäuse eines Ausführungsbeispiels des Trennschleifers und einen daran angeordneten Halter für das Einspritzventil,
Fig. 11
eine schematische Darstellung eines Ausführungsbeispiels der Kraftstoffzuführeinrichtung des Verbrennungsmotors.
Embodiments of the invention are explained below with reference to the drawing. Show it:
Fig. 1
a schematic representation of a cutting grinder,
Fig. 2
a section through the internal combustion engine of the cutting machine Fig. 1 .
Fig. 3
a schematic representation of the fuel supply of the internal combustion engine,
Fig. 4
a section through the crankcase of the cutting grinder and a holder arranged thereon for the injection valve,
Fig. 5
a section through the holder,
Fig. 6
a schematic representation of the surfaces of the cover and control diaphragm in the direction of arrow VI in Fig. 5 .
Fig. 7
an enlarged sectional view of the pressure damper, when no fuel pressure is applied,
Fig. 8
a section through the pressure damper in operation,
Fig. 9
a section through the pressure damper at too high fuel pressure,
Fig. 10
a section through the crankcase of an embodiment of the abrasive cutter and a holder arranged thereon for the injection valve,
Fig. 11
a schematic representation of an embodiment of the fuel supply of the internal combustion engine.

Fig. 1 zeigt als Ausführungsbeispiel für ein Arbeitsgerät, insbesondere für ein handgeführtes, tragbares Arbeitsgerät, einen Trennschleifer 1. Der erfindungsgemäße Verbrennungsmotor mit Kraftstoffzuführeinrichtung kann jedoch auch für andere Arbeitsgeräte wie beispielsweise Motorsägen, Freischneider, Blasgeräte oder dgl. vorgesehen sein. Fig. 1 shows as an exemplary embodiment of a working device, in particular for a hand-held, portable working device, a power cutter 1. The internal combustion engine with fuel supply device according to the invention, however, can also be provided for other tools such as chainsaws, brushcutters, blowers or the like.

Der Trennschleifer 1 besitzt ein Gehäuse 2, an dem ein nach vorne ragender Ausleger 3 fixiert ist. Am freien Ende des Auslegers 3 ist eine Trennscheibe 4 drehbar gelagert, die von einem im Gehäuse 2 angeordneten Verbrennungsmotor 12 rotierend angetrieben ist. Die Trennscheibe 4 ist über mehr als die Hälfe ihres Umfangs von einer Schutzhaube 5 abgedeckt. Das Gehäuse 2 umfasst eine Haube 8, an der ein oberer Handgriff 6 ausgebildet ist. Am oberen Handgriff 6 sind ein Gashebel 10 und eine Gashebelsperre 11 schwenkbar gelagert. An der der Trennscheibe 4 abgewandten Rückseite des Gehäuses 2 ist ein Luftfilterdeckel 9 festgelegt. An der der Trennscheibe 4 zugewandten Seite des Gehäuses 2 ist das Gehäuse 2 von einem Griffrohr 7 übergriffen. Der Trennschleifer 1 besitzt Standfüße 13, mit denen der Trennschleifer 1 auf dem Boden oder einer anderen Auflagefläche abgestellt werden kann.The cut-off machine 1 has a housing 2, on which a forwardly projecting arm 3 is fixed. At the free end of the boom 3, a cutting disc 4 is rotatably mounted, which is driven in rotation by a combustion engine 12 arranged in the housing 2. The cutting disk 4 is covered over more than half of its circumference by a protective cover 5. The housing 2 comprises a hood 8, on which an upper handle 6 is formed. At the upper handle 6, a throttle lever 10 and a throttle lock 11 are pivotally mounted. At the rear of the housing 2 facing away from the cutting disk 4, an air filter cover 9 is fixed. At the blade 4 facing side of the housing 2, the housing 2 is overlapped by a handle tube 7. The abrasive grinder 1 has feet 13 with which the grinder 1 can be placed on the floor or other support surface.

Fig. 2 zeigt den Verbrennungsmotor 12 im Einzelnen. Der Verbrennungsmotor 12 ist ein Zweitaktmotor. Der Verbrennungsmotor 12 kann jedoch auch ein gemischgeschmierter Viertaktmotor sein. Der Verbrennungsmotor 12 besitzt ein Kurbelgehäuse 14, an dem weitere Gehäuseteile angeformt sind. Das Kurbelgehäuse 14 begrenzt einen Kurbelgehäuseinnenraum 31, in dem eine Kurbelwelle 80 um eine Drehachse 15 drehbar gelagert ist. Die Kurbelwelle 80 ist über ein nicht gezeigtes Pleuel mit einem in Fig. 2 gestrichelt gezeigten Kolben 21 verbunden. Der Kolben 21 ist in einem Zylinder 16 hin- und hergehend gelagert und steuert einen Einlass 17, der im Bereich des oberen Totpunkts des Kolbens 21 in den Kurbelgehäuseinnenraum 31 mündet. Der Kolben 21 begrenzt einen im Zylinder 16 ausgebildeten Brennraum 22. Der Kurbelgehäuseinnenraum 31 ist im Bereich des in Fig. 2 gezeigten unteren Totpunkts des Kolbens 21 über einen oder mehrere Überströmkanäle 19 mit dem Brennraum 22 verbunden. Die Überströmkanäle 19 münden mit Überströmfenstern 20 in den Brennraum 22. Dabei kann sich ein Überströmkanal 19 in mehrere Äste aufteilen, die mit getrennten Überströmfenstern 20 in den Brennraum 22 münden, wie in Fig. 2 gezeigt ist. Aus dem Brennraum 22 führt, ein Auslass 18, der ebenfalls vom Kolben 21 schlitzgesteuert ist und der bei der in Fig. 2 gezeigten Stellung des Kolbens 21 im unteren Totpunkt geöffnet ist. Fig. 2 shows the internal combustion engine 12 in detail. The internal combustion engine 12 is a two-stroke engine. However, the engine 12 may also be a compound lubricated four-stroke engine. The internal combustion engine 12 has a crankcase 14, on which further housing parts are formed. The crankcase 14 defines a crankcase interior 31, in which a crankshaft 80 is rotatably mounted about a rotation axis 15. The crankshaft 80 is connected via an unillustrated connecting rod with a in Fig. 2 connected piston 21 shown connected in dashed lines. The piston 21 is reciprocally mounted in a cylinder 16 and controls an inlet 17, which opens in the region of the top dead center of the piston 21 into the crankcase interior 31. The piston 21 defines a combustion chamber 22 formed in the cylinder 16. The crankcase interior 31 is in the range of in Fig. 2 shown bottom dead center of the piston 21 via one or more transfer ports 19 connected to the combustion chamber 22. The overflow channels 19 open with overflow windows 20 into the combustion chamber 22. In this case, an overflow channel 19 can be divided into a plurality of branches, which open into the combustion chamber 22 with separate overflow windows 20, as in FIG Fig. 2 is shown. From the combustion chamber 22 leads, an outlet 18, which is also slit-controlled by the piston 21 and at the in Fig. 2 shown position of the piston 21 is open at bottom dead center.

Zur Zufuhr von Verbrennungsluft besitzt der Verbrennungsmotor 12 einen Ansaugkanal 30, der durch ein Drosselgehäuse 27 geführt ist. Im Drosselgehäuse 27 ist ein Drosselelement, im Ausführungsbeispiel eine Drosselklappe 28, angeordnet, auf die der Gashebel 10 wirkt. Zur Zufuhr von Kraftstoff ist ein Einspritzventil vorgesehen, das in Fig. 2 nicht gezeigt ist. Das Einspritzventil ist in einer Aufnahme 25 eines Halters 24 am Kurbelgehäuse 14 angeordnet. Wie Fig. 2 zeigt, ist der Halter 24 bei der in Fig. 1 gezeigten üblichen Abstellposition auf einer ebenen Unterlage unmittelbar unterhalb des Drosselgehäuses 27 angeordnet und am Kurbelgehäuse 14 fixiert. Der Halter 24 besitzt einen Austrittskanal 71 für Kraftstoff, der in den Kurbelgehäuseinnenraum 31 mündet. Benachbart zum Halter 24 ist eine Montageöffnung 23 am Kurbelgehäuse 14 ausgebildet, die zur Montage eines Druck-Temperatur-Sensors dient und die in Abstellposition unterhalb des Halters 24 angeordnet ist.For supplying combustion air, the internal combustion engine 12 has an intake passage 30, which is guided through a throttle housing 27. In the throttle housing 27, a throttle element, in the embodiment, a throttle valve 28, arranged on which the throttle lever 10 acts. For supplying fuel, an injection valve is provided which in Fig. 2 not shown. The injection valve is arranged in a receptacle 25 of a holder 24 on the crankcase 14. As Fig. 2 shows, the holder 24 at the in Fig. 1 shown usual Abstellposition arranged on a flat surface immediately below the throttle body 27 and fixed to the crankcase 14. The holder 24 has an outlet channel 71 for fuel, which opens into the crankcase interior 31. Adjacent to the holder 24, a mounting opening 23 is formed on the crankcase 14, which serves for mounting a pressure-temperature sensor and which is arranged in the parking position below the holder 24.

Im Betrieb wird im Bereich des oberen Totpunkts des Kolbens 21 Verbrennungsluft durch den Ansaugkanal 30 in den Kurbelgehäuseinnenraum 31 angesaugt. Das Einspritzventil führt Kraftstoff in den Kurbelgehäuseinnenraum 31 zu. Im Bereich des unteren Totpunkts des Kolbens 21 strömt das Kraftstoff/Luft-Gemisch aus dem Kurbelgehäuseinnenraum 31 über den oder die Überströmkanäle 19 und die Überströmfenster 20 in den Brennraum 22 ein. Beim Aufwärtshub des Kolbens 21 wird das Gemisch im Brennraum 22 verdichtet und im Bereich des oberen Totpunkts des Kolbens 21 von einer nicht gezeigten Zündkerze gezündet. Der Kolben 21 wird in Richtung auf das Kurbelgehäuse 14 beschleunigt. Sobald der Auslass 18 vom Kolben 21 geöffnet wird, entweichen die Abgase aus dem Brennraum 22 und frisches Gemisch aus dem Kurbelgehäuseinnenraum 31 strömt über den oder die Überströmkanäle 19 in den Brennraum 22 nach. Der Kolben 21 bewegt sich im Zylinder 16 in Richtung einer Zylinderlängsachse 29. Die Zylinderlängsachse 29 ist in der in Fig. 1 gezeigten üblichen Abstellposition des Trennschleifers 1 annähernd senkrecht oder geringfügig zur Senkrechen geneigt angeordnet.During operation, combustion air is sucked through the intake passage 30 into the crankcase interior 31 in the region of top dead center of the piston 21. The injection valve supplies fuel into the crankcase interior 31. In the region of the bottom dead center of the piston 21, the fuel / air mixture flows from the crankcase interior 31 via the or the overflow channels 19 and the overflow 20 in the combustion chamber 22 a. During the upward stroke of the piston 21, the mixture is compressed in the combustion chamber 22 and ignited in the region of top dead center of the piston 21 by a spark plug, not shown. The piston 21 is accelerated in the direction of the crankcase 14. As soon as the outlet 18 is opened by the piston 21, the exhaust gases escape from the combustion chamber 22 and fresh mixture from the crankcase interior 31 flows via the transfer port or passages 19 into the combustion chamber 22. The piston 21 moves in the cylinder 16 in the direction of a cylinder longitudinal axis 29. The cylinder longitudinal axis 29 is in the in Fig. 1 shown usual parking position of the cutting grinder 1 approximately perpendicular or slightly inclined to the vertical rake.

Fig. 3 zeigt die Kraftstoffzuführeinrichtung des Verbrennungsmotors 12 im Einzelnen. Der Trennschleifer 1 besitzt einen Kraftstofftank 32, in den ein Saugkopf 33 ragt. Die Kraftstoffzuführeinrichtung besitzt eine Kraftstoffpumpe 34, die einen von einer Pumpenmembran 39 begrenzten Pumpenraum 38 besitzt. In den Pumpenraum 38 wird über ein Ansaugventil 37, das als Rückschlagventil ausgebildet ist, Kraftstoff aus dem Kraftstofftank 32 über den Saugkopf 33 angesaugt. Der Kraftstoff wird über ein stromab des Pumpenraums 31 angeordnetes Druckventil 41, das ebenfalls als Rückschlagventil ausgebildet ist, in einen Kraftstoffraum 52 gefördert. Die Pumpenmembran 39 ist an ihrer dem Pumpenraum 38 abgewandten Seite über eine Impulsleitung 40 mit dem schwankenden Druck des Kurbelgehäuseinnenraums 31 beaufschlagt. Fig. 3 shows the fuel supply device of the internal combustion engine 12 in detail. The grinder 1 has a fuel tank 32 into which a suction head 33 protrudes. The fuel supply device has a fuel pump 34 which has a pump chamber 38 bounded by a pump diaphragm 39. In the pump chamber 38, fuel is sucked from the fuel tank 32 via the suction head 33 via a suction valve 37, which is designed as a check valve. The fuel is conveyed via a downstream of the pump chamber 31 arranged pressure valve 41, which is also designed as a check valve, in a fuel chamber 52. The pump diaphragm 39 is acted upon on its side facing away from the pump chamber 38 via an impulse line 40 with the fluctuating pressure of the crankcase interior 31.

Die Kraftstoffpumpe 34 ist in einem Pumpengehäuse 51 angeordnet, in dem auch ein Druckregler 35 angeordnet ist. Der Druckregler 35 ist stromab der Kraftstoffpumpe 34 angeordnet. Der Druckregler 35 besitzt eine Regelmembran 44, die eine Regelkammer 43 von einem Rückraum 47 trennt. Die Regelkammer 43 ist über ein Einlassventil 42 mit dem Kraftstoffraum 52 der Kraftstoffpumpe 34 verbunden. Das Einlassventil 42 wird von einer Einlassnadel gebildet, die an einem Hebel 45 angeordnet ist. Das zweite Ende des Hebels 45 ist mit der Regelmembran 44 verbunden. In Abhängigkeit der Stellung der Regelmembran 44 öffnet und schließt das Einlassventil 42. Die Regelmembran 44 ist von einer Feder 46 in Richtung auf die Regelkammer belastet. Im Ausführungsbeispiel ist die Feder 46 als Druckfeder ausgebildet und im Rückraum 47 angeordnet. Der Rückraum 47 ist über eine Öffnung 48 mit einem Referenzdruck beaufschlagt, der im Ausführungsbeispiel der Umgebungsdruck ist. Am Auslass aus der Regelkammer 43 ist ein Kraftstoffsieb 49 angeordnet, durch das der Kraftstoff aus der Regelkammer 43 in eine Kraftstoffleitung 50 strömt.The fuel pump 34 is arranged in a pump housing 51, in which a pressure regulator 35 is arranged. The pressure regulator 35 is disposed downstream of the fuel pump 34. The pressure regulator 35 has a control diaphragm 44, which separates a control chamber 43 from a rear chamber 47. The control chamber 43 is connected via an inlet valve 42 to the fuel chamber 52 of the fuel pump 34. The inlet valve 42 is of a Inlet needle formed, which is arranged on a lever 45. The second end of the lever 45 is connected to the control diaphragm 44. Depending on the position of the control diaphragm 44, the inlet valve 42 opens and closes. The control diaphragm 44 is loaded by a spring 46 in the direction of the control chamber. In the exemplary embodiment, the spring 46 is designed as a compression spring and arranged in the rear space 47. The rear chamber 47 is acted upon via an opening 48 with a reference pressure, which is the ambient pressure in the embodiment. At the outlet from the control chamber 43, a fuel strainer 49 is arranged, through which the fuel flows from the control chamber 43 into a fuel line 50.

Über die Kraftstoffleitung 50 strömt der Kraftstoff in einen Druckdämpfer 36, der unmittelbar benachbart zum in Fig. 3 schematisch gezeigten Einspritzventil 26 angeordnet ist. Der Druckdämpfer 36 besitzt eine Dämpfungsmembran 54, die einen Dämpfungsraum 53 von einem Rückraum 56 trennt. Der Kraftstoff aus der Kraftstoffleitung 50 strömt durch den Dämpfungsraum 53. Die Dämpfungsmembran 54 ist von einer Feder 55 in Richtung auf den Dämpfungsraum 53 beaufschlagt. Im Ausführungsbeispiel ist die Feder 55 als Druckfeder ausgebildet und im Rückraum 56 angeordnet. Der Rückraum 56 ist über eine Öffnung 57 mit dem gleichen Referenzdruck wie der Druckregler 35, im Ausführungsbeispiel mit dem Umgebungsdruck, beaufschlagt.Via the fuel line 50, the fuel flows into a pressure damper 36, which is immediately adjacent to in Fig. 3 is schematically shown injection valve 26 is arranged. The pressure damper 36 has a damping diaphragm 54, which separates a damping chamber 53 from a rear space 56. The fuel from the fuel line 50 flows through the damping chamber 53. The damping diaphragm 54 is acted upon by a spring 55 in the direction of the damping chamber 53. In the exemplary embodiment, the spring 55 is designed as a compression spring and arranged in the rear space 56. The rear space 56 is acted upon via an opening 57 with the same reference pressure as the pressure regulator 35, in the embodiment with the ambient pressure.

Vom Dämpfungsraum 53 gelangt der Kraftstoff zum Einspritzventil 26. Das Einspritzventil 26 führt den Kraftstoff in den Kurbelgehäuseinnenraum 31 zu. Kraftstoff, der nicht in den Kurbelgehäuseinnenraum 31 zugeführt wird, gelangt über eine Rückleitung 58 zurück in den Kraftstofftank 32.From the damping chamber 53, the fuel reaches the injection valve 26. The injection valve 26 supplies the fuel into the crankcase interior 31. Fuel, which is not supplied into the crankcase interior 31, passes via a return line 58 back into the fuel tank 32nd

Fig. 4 zeigt die konstruktive Anordnung des Halters 24 und des Druckdämpfers 36 am Umfang des Kurbelgehäuses 14 in einer schräg geschnittenen, perspektivischen Darstellung. Wie Fig. 4 zeigt, liegen der Halter 24 und der Druckdämpfer 36 in Richtung der Drehachse 15 der Kurbelwelle nebeneinander. Der Halter 24 liegt dabei benachbart zu einem Startergehäuse 82, in dem die Starteinrichtung für den Verbrennungsmotor 12 angeordnet ist. In dem Startergehäuse 82 sind auch eine Fliehkraftkupplung sowie eine Riemenscheibe zum Antrieb des Antriebsriemens der Trennscheibe 4 angeordnet. Der Druckdämpfer 36 liegt benachbart zu einem Lüfterradgehäuse 81, in dem das Lüfterrad des Verbrennungsmotors rotiert und Kühlluft fördert. Ein Druckbereich des Lüfterradgehäuses 81 ist über einen Kanal 83, der in Fig. 4 nur schematisch gezeigt ist, mit einem Kühlgehäuse 84 verbunden, in dem der Halter 24 und der Druckdämpfer 36 angeordnet sind. Über den Kanal 83 wird der Halter 24 mit dem Einspritzventil 26 und dem Druckdämpfer 36 aktiv gekühlt. Fig. 4 shows the structural arrangement of the holder 24 and the pressure damper 36 on the circumference of the crankcase 14 in an obliquely cut, perspective view. As Fig. 4 shows, the holder 24 and the pressure damper 36 are in the direction of the axis of rotation 15 of the crankshaft side by side. The holder 24 is adjacent to a starter housing 82, in which the starting device for the internal combustion engine 12 is arranged. In the starter housing 82 are also a centrifugal clutch and a Pulley arranged to drive the drive belt of the cutting disc 4. The pressure damper 36 is adjacent to a Lüfterradgehäuse 81, in which rotates the fan of the engine and promotes cooling air. A pressure range of the Lüfterradgehäuses 81 is via a channel 83, the in Fig. 4 is shown only schematically, connected to a cooling housing 84, in which the holder 24 and the pressure damper 36 are arranged. Via the channel 83, the holder 24 with the injection valve 26 and the pressure damper 36 is actively cooled.

Fig. 5 zeigt die Gestaltung des Halters 24 im Einzelnen. Der Halter 24 besitzt ein Gehäuse 59, das ein erstes Gehäuseteil 60 und ein zweites Gehäuseteil 61 umfasst. Am ersten Gehäuseteil 60 sind ein erster Kraftstoffstutzen 63, in dem die Kraftstoffleitung 50 ausgebildet ist, sowie ein zweiter Kraftstoffstutzen 64, in dem die Rückleitung 58 ausgebildet ist, fixiert. Wie Fig. 5 zeigt, mündet die Kraftstoffleitung 50 in einem radial außen liegenden Bereich in den Dämpfungsraum 53. Aus dem Dämpfungsraum 53 führt ein Verbindungskanal 73 zum Einspritzventil 26. Der Verbindungskanal 73 mündet an einem Ringraum 85 am Umfang des Einspritzventils 26. Der Ringraum ist über eine in Fig. 7 gezeigte Eintrittsöffnung 72 mit dem Inneren des Einspritzventils 26 verbunden. Der Kraftstoff verlässt das Einspritzventil 26 über die in Fig. 5 gezeigte Kraftstofföffnung 70, die in den Austrittskanal 71 mündet. Die Kraftstofföffnung 70 wird vom Einspritzventil 26 geöffnet und geschlossen. Fig. 5 shows the design of the holder 24 in detail. The holder 24 has a housing 59, which comprises a first housing part 60 and a second housing part 61. On the first housing part 60, a first fuel nozzle 63, in which the fuel line 50 is formed, and a second fuel nozzle 64, in which the return line 58 is formed fixed. As Fig. 5 From the damping chamber 53, a connecting channel 73 leads to the injection valve 26. The connecting channel 73 opens at an annular space 85 on the circumference of the injection valve 26. The annular space is connected via an in Fig. 7 shown inlet opening 72 connected to the interior of the injection valve 26. The fuel leaves the injection valve 26 via the in Fig. 5 shown fuel port 70, which opens into the outlet channel 71. The fuel opening 70 is opened and closed by the injection valve 26.

Wie Fig. 5 zeigt, ist der Rückraum 56 im zweiten Gehäuseteil 61 ausgebildet. Der unmittelbar benachbart zur Dämpfungsmembran 54 angeordnete Bereich ist über eine oder mehrere Verbindungsöffnungen 62 mit einem Bereich 86 des Dämpfungsraums 53 verbunden. Der Bereich 86 besitzt die Öffnung 57 zur Umgebung. Die Öffnung 57 ist von einer Abdeckung 67 abgedeckt, die luftdurchlässig und insbesondere wasserabweisend oder wasserundurchlässig ausgebildet ist. Die Abdeckung 67 ist vorteilhaft ein gesintertes Metallsieb. Wie Fig. 5 auch zeigt, stützt sich die Feder 55 an einem Stopfen 65 ab, der in einer Halterung 66 gehalten, beispielsweise in diese einschraubt oder eingepresst ist. Die Position des Stopfens 65 in der Halterung 66 kann bei der Herstellung des Druckdämpfers 36 verändert werden. Dadurch ist die Vorspannung der Feder 55 und damit die Lage der Dämpfungsmembran 54 bei dem gewünschten Kraftstoffdruck einstellbar.As Fig. 5 shows, the rear space 56 is formed in the second housing part 61. The region arranged immediately adjacent to the damping membrane 54 is connected to a region 86 of the damping chamber 53 via one or more connecting openings 62. The area 86 has the opening 57 to the environment. The opening 57 is covered by a cover 67, which is permeable to air and in particular water-repellent or impermeable to water. The cover 67 is advantageously a sintered metal mesh. As Fig. 5 also shows, the spring 55 is supported on a plug 65 which is held in a holder 66, for example screwed or pressed into this. The position of the plug 65 in the holder 66 may be in the manufacture of the pressure damper 36 are changed. As a result, the bias of the spring 55 and thus the position of the damping diaphragm 54 at the desired fuel pressure is adjustable.

Wie die schematische Darstellung in Fig. 6 zeigt, ist die freie Durchtrittsfläche a der Abdeckung 67 deutlich größer als die im Rückraum 56 beaufschlagte Fläche der Dämpfungsmembran 54. Die freie Durchtrittsfläche a beträgt vorteilhaft mindestens das 2fache, insbesondere mindestens das 3fache bis 10fache der mit dem Referenzdruck direkt beaufschlagten Fläche b der Dämpfungsmembran 54. Auch bei teilweiser Verschmutzung der Abdeckung 67 ist so sichergestellt, dass der Umgebungsdruck an der Dämpfungsmembran 54 anliegt. Durch die Abdeckung 67 kann sich der Druck zwischen der Umgebung und dem Rückraum 56 ausgleichen. Der Druckausgleich kann dabei insbesondere bei starker Verschmutzung der Abdeckung 67 langsam stattfinden. Durch die Abdeckung 67 muss lediglich ein Ausgleich langsamer Änderungen des Druckniveaus im Rückraum 56, beispielsweise durch die Erwärmung des Druckdämpfers 36 im Betrieb des Verbrennungsmotors 12 und die damit einhergehende Vergrößerung des Volumens der Luft im Rückraum 56, stattfinden.Like the schematic representation in Fig. 6 shows, the free passage area a of the cover 67 is significantly larger than the acted upon in the back space 56 surface of the damping diaphragm 54. The free passage area a is advantageously at least twice, in particular at least 3 times to 10 times the directly pressurized with the reference pressure surface b of the damping diaphragm 54th Even with partial soiling of the cover 67, it is ensured that the ambient pressure is applied to the damping membrane 54. Through the cover 67, the pressure between the environment and the rear space 56 can compensate. The pressure compensation can take place slowly, especially in the case of heavy contamination of the cover 67. Through the cover 67, only a compensation of slow changes in the pressure level in the rear space 56, for example, by the heating of the pressure damper 36 during operation of the internal combustion engine 12 and the concomitant increase in the volume of air in the rear space 56, take place.

Wie die Figuren 5 und 7 zeigen, ist die Dämpfungsmembran 54 an einer Haltebuchse 69 gehalten. Die Fläche der Dämpfungsmembran 54, die von der Haltebuchse 69 abgedeckt ist, zählt nicht zur beaufschlagten Fläche b.As the FIGS. 5 and 7 show, the damping diaphragm 54 is held on a retaining sleeve 69. The area of the damping membrane 54 that is covered by the holding bushing 69 does not count towards the applied area b.

Fig. 7 zeigt die Fixierung der Dämpfungsmembran 54 im Einzelnen. Die Dämpfungsmembran 54 besitzt einen inneren Rand 75, der zwischen der Haltebuchse 69 und einem von der gegenüberliegenden Seite eingepressten Haltezapfen 68 gehalten ist. Der Haltezapfen 68 besitzt einen Halterand 77, der den inneren Rand 75 der Dämpfungsmembran 54 gegen einen Rand der Haltebuchse 69 drückt und so fixiert. Der äußere Rand 76 der Dämpfungsmembran 54 ist zwischen den beiden Gehäuseteilen 60 und 61 geklemmt gehalten und liegt in einer gedachten Ebene 91. Im Ausführungsbeispiel verläuft die gedachte Ebene 91 parallel zu einer Längsmittelachse 92 des Einspritzventils 26. Vorteilhaft schließt die gedachte Ebene 91 mit der Längsmittelachse 92 des Einspritzventils 26 einen Winkel ein, der kleiner als etwa 30° ist. Wie Fig. 7 auch zeigt, besitzt die Haltebuchse 69 eine Abstützfläche 74, an der ein Ende der als Druckfeder ausgebildeten Feder 55 anliegt. Die Haltebuchse 69 ragt ins Innere der Feder 55 und bildet eine Führung für die Feder 55. An ihrem anderen Ende stützt sich die Feder 55 am Stopfen 65 ab. Fig. 7 shows the fixation of the damping membrane 54 in detail. The damping membrane 54 has an inner edge 75 which is held between the retaining sleeve 69 and a retaining pin 68 pressed in from the opposite side. The retaining pin 68 has a retaining edge 77 which presses the inner edge 75 of the damping membrane 54 against an edge of the retaining sleeve 69 and fixed so. The outer edge 76 of the damping membrane 54 is clamped between the two housing parts 60 and 61 and lies in an imaginary plane 91. In the exemplary embodiment, the imaginary plane 91 extends parallel to a longitudinal central axis 92 of the injection valve 26. Advantageously, the imaginary plane 91 closes with the longitudinal central axis 92 of the injection valve 26 at an angle which is less than about 30 °. As Fig. 7 also shows, the retaining sleeve 69 has a support surface 74, on which one end of the spring 55 formed as a compression spring rests. The retaining sleeve 69 protrudes into the interior of the spring 55 and forms a guide for the spring 55. At its other end, the spring 55 is supported on the plug 65.

Der Verbindungskanal 73 ist sehr kurz ausgebildet. Wie Fig. 7 zeigt, besitzt der Verbindungskanal 73 eine Länge 1, die nur geringfügig größer als der Durchmesser d des Verbindungskanals 73 ist. Die Länge 1 beträgt vorteilhaft höchstens das 5fache des Durchmessers d des Verbindungskanals 73. Die Länge 1 beträgt deutlich weniger als der Durchmesser der Dämpfungsmembran 54. Die Länge 1 ist dabei vom Austritt aus dem Dämpfungsraum 53 bis zum Eintritt in den Ringraum 85 gemessen.The connecting channel 73 is formed very short. As Fig. 7 shows, the connecting channel 73 has a length 1, which is only slightly larger than the diameter d of the connecting channel 73. The length 1 is advantageously at most 5 times the diameter d of the connecting channel 73. The length 1 is significantly less than the diameter of the damping diaphragm 54. The length 1 is measured from the exit from the damping chamber 53 until it enters the annular space 85.

In Fig. 7 ist die Dämpfungsmembran 54 in einer ersten Endlage angeordnet. In dieser Endlage liegt der Haltezapfen 68 an einem im Dämpfungsraum 53 angeordneten Anschlag 78 an. Diese Lage der Dämpfungsmembran 54 ergibt sich, wenn der Kraftstoff im Dämpfungsraum 53 drucklos ist oder kein Kraftstoff im Dämpfungsraum 53 angeordnet ist.In Fig. 7 the damping membrane 54 is arranged in a first end position. In this end position of the retaining pin 68 is located on a arranged in the damping chamber 53 stop 78. This position of the damping diaphragm 54 results when the fuel in the damping chamber 53 is depressurized or no fuel is arranged in the damping chamber 53.

In Fig. 8 ist die Dämpfungsmembran 54 in ihrer Mittellage gezeigt. In dieser Lage befindet sich die Dämpfungsmembran 54 vorteilhaft im Betrieb. Der Haltezapfen 68 besitzt einen Abstand zum Anschlag 78. An der Halterung 66 ist ein Anschlag 79 ausgebildet, zu dem die Abstützfläche 74 bei der in Fig. 8 gezeigten Mittellage ebenfalls einen Abstand besitzt. Der Betriebsdruck kann beispielsweise etwa 100 mbar Überdruck gegenüber dem Umgebungsdruck betragen.In Fig. 8 the damping membrane 54 is shown in its central position. In this position, the damping diaphragm 54 is advantageously in operation. The retaining pin 68 has a distance from the stop 78. On the holder 66, a stop 79 is formed, to which the support surface 74 at the in Fig. 8 shown center position also has a distance. The operating pressure may be, for example, about 100 mbar overpressure relative to the ambient pressure.

Fig. 9 zeigt die Dämpfungsmembran 54 in ihrer anderen Endlage. In dieser Lage liegt die Abstützfläche 74 am Anschlag 79 an. Diese Lage ergibt sich, wenn der Druck des Kraftstoffs im Dämpfungsraum 53 zu hoch ist und beispielsweise etwa 130 mbar beträgt. Durch die Anschläge 78 und 79 wird ein übermäßiges Auslenken der Dämpfungsmembran 54 vermieden. Eine gute Kraftstoffdämpfung ist bei der in Fig. 8 gezeigten Mittellage der Dämpfungsmembran 54 gegeben. Um sicherzustellen, dass die Dämpfungsmembran 54 im Betrieb in ihrer Mittellage arbeitet, ist vorgesehen, dass im Rückraum 56 des Druckdämpfers 36 und im Rückraum 47 des Druckreglers 35 der gleiche Referenzdruck herrscht. Im Ausführungsbeispiel ist dies der Umgebungsdruck. Der Referenzdruck kann jedoch auch ein anderer Druck, beispielweise der Druck im Reinraum eines Luftfilters des Verbrennungsmotors 12 sein. Dadurch, dass der Druckregler 35 und der Druckdämpfer 36 mit dem gleichen Referenzdruck arbeiten, ist auf einfache Weise eine Abstimmung von Druckregler 35 und Druckdämpfer 36 gegeben. Auch bei sehr geringen Kraftstoffdrücken, bei denen die Feder 55 im Druckdämpfer 36 sehr schwach ausgelegt ist, kann dadurch sichergestellt werden, dass die Dämpfungsmembran 54 im Betrieb in ihrer Mittellage arbeitet und so die entstehenden Druckschwankungen gut dämpfen kann. Fig. 9 shows the damping membrane 54 in its other end position. In this position, the support surface 74 abuts the stop 79. This situation arises when the pressure of the fuel in the damping chamber 53 is too high and is for example about 130 mbar. By the stops 78 and 79 an excessive deflection of the damping membrane 54 is avoided. Good fuel damping is at the in Fig. 8 shown center position of the damping diaphragm 54 given. To ensure that the damping diaphragm 54 operates in its center position during operation, it is provided that in the rear space 56 of the pressure damper 36 and in the rear space 47 of the pressure regulator 35, the same reference pressure prevails. In the exemplary embodiment, this is the ambient pressure. However, the reference pressure may also be another pressure, for example the pressure in the clean room of an air filter of the internal combustion engine 12. The fact that the pressure regulator 35 and the pressure damper 36 operate with the same reference pressure, a vote of pressure regulator 35 and pressure damper 36 is given in a simple manner. Even with very low fuel pressures at which the spring 55 is designed very weak in the pressure damper 36, it can be ensured that the damping diaphragm 54 operates in operation in its central position and can dampen the resulting pressure fluctuations well.

Fig. 10 zeigt ein Ausführungsbeispiel des Kurbelgehäuses 14 eines Trennschleifers 1. Gleiche Bezugszeichen wie in den vorangegangenen Figuren bezeichnen dabei entsprechende Bauteile. Bei dem gezeigten Ausführungsbeispiel ist der Rückraum 56 des Druckdämpfers 36 nicht mit dem Umgebungsdruck, sondern mit dem Druck im Lüfterradgehäuse 81 beaufschlagt. Die Öffnung 57 ist über einen Kanal 89, der im Ausführungsbeispiel in einem Trichter 90 geführt ist, mit einer Verbindungsöffnung 88 im Lüfterradgehäuse 81 verbunden. Die Verbindungsöffnung 88 ist im Ausführungsbeispiel in einem Überdruckbereich des Lüfterradgehäuses 81 angeordnet, so dass der Referenzdruck des Druckdämpfers 36 im Betrieb des Verbrennungsmotors 12 höher als der Umgebungsdruck ist. Die Verbindungsöffnung 88 kann jedoch auch in einem Unterdruckbereich des Lüfterradgehäuses 81 angeordnet sein. Der Referenzdruck des in Fig. 10 nicht gezeigten Druckreglers 35 ist wie im ersten Ausführungsbeispiel gezeigt der Umgebungsdruck, so dass die Referenzdrücke von Druckregler 35 und Druckdämpfer 36 unterschiedlich sind. Fig. 10 shows an embodiment of the crankcase 14 of a cutting grinder 1. The same reference numerals as in the preceding figures indicate corresponding components. In the embodiment shown, the rear space 56 of the pressure damper 36 is not acted upon by the ambient pressure, but with the pressure in the Lüfterradgehäuse 81. The opening 57 is connected via a channel 89, which is guided in the embodiment in a funnel 90, with a connection opening 88 in the Lüfterradgehäuse 81. The connection opening 88 is arranged in the exemplary embodiment in an overpressure region of the fan wheel housing 81, so that the reference pressure of the pressure damper 36 during operation of the internal combustion engine 12 is higher than the ambient pressure. However, the connection opening 88 can also be arranged in a negative pressure region of the fan wheel housing 81. The reference pressure of in Fig. 10 Pressure regulator 35, not shown, is the ambient pressure as shown in the first embodiment, so that the reference pressures of pressure regulator 35 and pressure damper 36 are different.

Die unterschiedlichen Referenzdrücke von Druckregler 35 und Druckdämpfer 36 werden kompensiert. Hierzu kann die Feder 55 des Druckdämpfers 36 entsprechend schwach ausgelegt sein oder ganz entfallen. Alternativ oder zusätzlich kann eine Kompensation durch eine entsprechende Vorspannung der Dämpfungsmembran 54 des Druckdämpfers 36 erfolgen. Es kann auch vorgesehen sein, die Unterschiede der Referenzdrücke zu vernachlässigen. Alternativ kann auch eine elektronische Kompensation der Differenz der Referenzdrücke vorgesehen sein.The different reference pressures of pressure regulator 35 and pressure damper 36 are compensated. For this purpose, the spring 55 of the pressure damper 36 can be designed to be correspondingly weak or completely eliminated. Alternatively or additionally, a compensation by a corresponding bias of the damping diaphragm 54 of the pressure damper 36 done. It may also be provided to neglect the differences in the reference pressures. Alternatively, an electronic compensation of the difference of the reference pressures may be provided.

In einer alternativen Gestaltung ist ein digitaler Druckaufnehmer vorgesehen, der einen oder beide Referenzdrücke misst und auftretende Druckunterschiede elektronisch kompensiert. Zusätzlich kann ein Aktor vorgesehen sein, der entsprechend der gemessenen Druckunterschiede auf den Druckdämpfer einwirkt und die Druckunterschiede so kompensiert. Dies kann beispielsweise durch mechanische Verstellung einer Anlagefläche der Feder 55 erfolgen. Dadurch wird die Vorspannung der Feder 55 und damit die Ruhelage der Dämpfungsmembran 53 verändert. So können Druckunterschiede zwischen den Referenzdrücken kompensiert werden.In an alternative embodiment, a digital pressure transducer is provided which measures one or both reference pressures and electronically compensates for any differences in pressure. In addition, an actuator may be provided which acts on the pressure damper according to the measured pressure differences and thus compensates the pressure differences. This can be done for example by mechanical adjustment of a contact surface of the spring 55. As a result, the bias of the spring 55 and thus the rest position of the damping diaphragm 53 is changed. Thus, pressure differences between the reference pressures can be compensated.

Bei dem in Fig. 11 gezeigten Ausführungsbeispiel der Kraftstoffzuführeinrichtung des Trennschleifers 1 (Fig. 1) ist der Druckdämpfer 36 nicht in der vom Druckregler 35 zum Einspritzventil 26 führenden Kraftstoffleitung 50 angeordnet, sondern stromab des Einspritzventils 26 in der Rückleitung 58. Der Druck in der Rückleitung 58 entspricht im Wesentlichen dem Druck in der Kraftstoffleitung 50, insbesondere bei geschlossenem Einspritzventil 26. Dadurch wird bei dem in Fig. 11 gezeigten Ausführungsbeispiel die gleiche Druckdämpfung erreicht wie bei dem in Fig. 3 gezeigten Ausführungsbeispiel. Auch bei dem in Fig. 11 gezeigten Ausführungsbeispiel ist der Dämpfungsraum 53 des Druckdämpfers 36 vom Kraftstoff durchströmt, so dass die Bildung von Dampfblasen vermieden ist. Der Aufbau der Kraftstoffzuführeinrichtung aus Fig. 11 entspricht - bis auf die Anordnung des Druckdämpfers 36 - dem Aufbau des in Fig. 3 gezeigten Ausführungbeispiels. Gleiche Bezugszeichen kennzeichnen einander entsprechende Elemente.At the in Fig. 11 shown embodiment of the fuel supply device of the cutting machine 1 ( Fig. 1 The pressure in the return line 58 substantially corresponds to the pressure in the fuel line 50, in particular when the injection valve 26 is closed This will cause the in Fig. 11 embodiment shown achieves the same pressure damping as in the Fig. 3 shown embodiment. Also at the in Fig. 11 the embodiment shown, the damping chamber 53 of the pressure damper 36 flows through the fuel, so that the formation of vapor bubbles is avoided. The structure of the fuel supply from Fig. 11 corresponds - except for the arrangement of the pressure damper 36 - the structure of in Fig. 3 shown embodiment. Like reference numerals denote corresponding elements.

Claims (15)

  1. Internal combustion engine with a fuel supply device, wherein the fuel supply device comprises a fuel pump (34), a pressure damper (36) and an injector (26), wherein the pressure damper (36) has a damping diaphragm (54) which separates a damping chamber (53) from a back chamber (56), wherein a first reference pressure is applied to the back chamber (56) of pressure damper (36), and wherein the fuel supply device has a pressure regulator (33),
    characterised in that the pressure regulator (33) controls the pressure of the fuel delivered by the fuel pump (34) to the injector (26) on the basis of a second reference pressure of the pressure regulator (33), and in that the first reference pressure and the second reference pressure are matched to each other.
  2. Internal combustion engine according to claim 1,
    characterised in that the first reference pressure is equal to the second reference pressure, the first reference pressure and the second reference pressure being ambient pressure in particular.
  3. Internal combustion engine according to claim 1 or 2,
    characterised in that the damping chamber (53) is located in the flow path of the fuel from the fuel pump (34) to the injector (26).
  4. Internal combustion engine according to any of claims 1 to 3,
    characterised in that the damping chamber (53) is located in the flow path of the fuel from the injector (26) to a fuel tank (32) of the fuel supply device.
  5. Internal combustion engine according to any of claims 1 to 4,
    characterised in that the injector (26) is located on a holder (24) fixed to the internal combustion engine (12).
  6. Internal combustion engine according to claim 5,
    characterised in that the holder (24) has a housing (59), the damping chamber (53) of the pressure damper (36) being bounded by the housing (59) of the holder (24).
  7. Internal combustion engine according to claim 5 or 6,
    characterised in that the holder (24) is located on a crankcase (14) of the internal combustion engine (12) and has an outlet passage (71) for fuel which terminates into the crankcase interior (31).
  8. Internal combustion engine according to any of claims 1 to 7,
    characterised in that the first reference pressure is applied to the back chamber (56) of the pressure damper (36) via an opening (57), which is covered by a cover (67) in an air-permeable manner, the cover (67) being a sintered metal sieve in particular.
  9. Internal combustion engine according to any of claims 1 to 8,
    characterised in that a connecting passage (73) leads from the damping chamber (53) to a receptacle (25) for the injector (26), the length (1) of the connecting passage (73) from the damping chamber (53) to the receptacle (25) being a maximum of 5 times the diameter (d) of the connecting passage (73).
  10. Internal combustion engine according to any of claims 1 to 9,
    characterised in that the damping diaphragm (54) of the pressure damper (36) is loaded towards the damping chamber (53) by a spring (55), the preload of the spring (55) being adjustable.
  11. Internal combustion engine according to any of claims 1 to 10,
    characterised in that the pressure damper (36) has in the back chamber (56) and in the damping chamber (53) a stop (78, 79) each for determining an end position of the damping diaphragm (54).
  12. Internal combustion engine according to any of claims 1 to 11,
    characterised in that the damping diaphragm (54) has an outer edge (76) lying in an imaginary plane (91), which encloses an angle of less than approximately 30 degrees with a longitudinal central axis (92) of the injector (26).
  13. Internal combustion engine according to any of claims 1 to 12,
    characterised in that the fuel pump (34) has a pump housing (51), in which the pressure regulator (35) is located.
  14. Internal combustion engine according to any of claims 1 to 13,
    characterised in that the pressure regulator (35) has a regulating diaphragm (44) bounding a regulating chamber (43), wherein an inlet valve (42) which is opened or closed as a function of the position of the regulating diaphragm (44) is located at the inlet into the regulating chamber (43), and in that a back chamber (47) to which the second reference pressure is advantageously applied is formed on the side of the regulating diaphragm (44) which is remote from the regulating chamber (43) in particular.
  15. Internal combustion engine according to any of claims 1 to 14,
    characterised in that the internal combustion engine has a crankcase (14), and in that the fuel pump (34) has a pump diaphragm (39), to which the fluctuating pressure of the crankcase interior (31) is applied.
EP12008129.4A 2011-12-07 2012-12-05 Internal combustion engine with a fuel supply system Active EP2602471B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE102011120468A DE102011120468A1 (en) 2011-12-07 2011-12-07 Internal combustion engine with fuel supply device

Publications (3)

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EP2602471A2 EP2602471A2 (en) 2013-06-12
EP2602471A3 EP2602471A3 (en) 2014-12-17
EP2602471B1 true EP2602471B1 (en) 2017-03-08

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US (1) US20130146028A1 (en)
EP (1) EP2602471B1 (en)
JP (1) JP2013119861A (en)
CN (1) CN103174571A (en)
DE (1) DE102011120468A1 (en)

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Also Published As

Publication number Publication date
EP2602471A3 (en) 2014-12-17
US20130146028A1 (en) 2013-06-13
CN103174571A (en) 2013-06-26
DE102011120468A1 (en) 2013-06-13
EP2602471A2 (en) 2013-06-12
JP2013119861A (en) 2013-06-17

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