US3730155A

US3730155A - Fuel injection apparatus for spark plug-ignited internal combustion engines

Info

Publication number: US3730155A
Application number: US00212955A
Authority: US
Inventors: H Knapp
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1971-01-11
Filing date: 1971-12-28
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01
Also published as: FR2122141A6; ES398729A2; SU513641A3; SE365024B; JPS5440694B1; BR7200128D0; CS157136B4; GB1363739A; DE2100935A1; DE2100935B2; IT1003022B

Abstract

In a fuel injection apparatus the air-fuel ratio is controlled by an air sensor which is deflected against a return force by the intake air and which, as a function of the extent of its deflection, controls the output of a fuel metering valve. To ensure a leaner fuel mixture subsequent to a cold engine start, there is provided a first temperature-dependent control element which is responsive to the water coolant temperature and, upon the increase of the latter, causes an increase in the bias of a spring augmenting, in turn, said return force to bring about a leaner fuel mixture and a second temperature-dependent control element which is responsive to a separate heater means and which, for a very short period subsequent to the starting of the cold engine, hinders said first temperature-dependent control element to increase said bias.

Description

United States Patent [191 Knapp [54] FUEL INJECTION APPARATUS FOR SPARK PLUG-IGNITED INTERNAL COMBUSTION ENGINES [75] Inventor: Heinrich Knapp, 725 Leonberg-silberberg, Germany [73] Assignee: Robert Bosch GmbH, Stuttgart, Germany 22 Filed: Dec. 28, 1971 21 Appl. No.: 212,955

[30] Foreign Application Priority Data 56] References Cited UNITED sTATEsi ATEN'Ts Eckert et al. ..l23/l 19 R [451 May 1,1973

Primary Examiner-Wendell E. Burns Att0rneyEdwin E. Greigg [5 7] ABSTRACT In a fuel injection apparatus the air-fuel ratio is controlled by an air sensor which is deflected against a return force by the intake air and which, as a function of the extent of its deflection, controls the output of a fuel metering valve. To ensure a leaner fuel mixture subsequent to a cold engine start, there is provided a first temperature-dependent control element which is responsive to the water coolant temperature and, upon the increase of the latter, causes an increase in the bias of a spring augmenting, in turn, said return force to bring about a leaner fuel mixture and a second temperature-dependent control element which is responsive to a separate heater means and which, for a very short period subsequent to the starting of the cold engine, hinders said first temperature-dependent control element to increase said bias.

5 Claims, 2 Drawing Figures Patented May 1, 1973 I 3,730,155

2 Sheets-Sheet 1 Patented May 1, 1973 2 Sheets-Sheet 2 kc/cm Fig.2

FUEL INJECTION APPARATUS FOR SPARK PLUG- .IGNITEI) INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION This invention relates to a fuel injection apparatus associated with a spark plug-ignited internal combustion engine which operates on fuel continuously injected into the air intake tube. In the latter there are serially arranged an air sensor and an arbitrarily operable butterfly valve. Theair sensor is displaceable by the air flow against a constant return force to an extent proportionate to the throughgoing air quantities. The air sensor displaces the fuel rack of a fuel quantity distributor valve disposed in the fuel line for the metering of fuel quantities in proportion to the throughgoingair quantities. The aforenoted return force is derived from the pressure of a liquid which is supplied continuously and under constant pressure through a pressure conduit and which affects a control plunger operatively connected to the air sensor. The pressure of said liquid is variable by a pressure control valve which is, in turn, responsive to at least one engine variable. Besides the pressure control valve there is provided a temperatureresponsive control element operating a closing member disposed in a bypass channel which circumvents the butterfly valve. Said bypass is closed after the normal operational temperatures of the internal combustion engine are reached.

In a fuel injection apparatus of the aforenoted type the difficulty is encountered that the enriching of the fuel-air mixture for the warm-up operation has to be substantially greater immediately after starting the engine than it is necessary for the subsequent engine run after a certain period. Thus, assuming for example an engine start at 20 C, the fuel mixture, by the time the engine runs at C of coolant water temperature, is enriched approximately twice the extent necessary to keep the engine running immediately after starting and to ensure optimally clean exhaust gases at 0 C of coolant water temperature. The reason is the increase in fuel condensation at the cold cylinder walls which are pre-warmed by virtue of the several ignitions, whereas the coolant temperature still remains practically the same. An apparatus of the aforenoted type isdescribed inPublished German Application (DOS) 1,960,144.

I OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide an improved fuel injection apparatus wherein the fuel enriching for the warm-up run is improved in such a manner that for a very short period immediately subsequent to the starting of the-engine, there is effected the usual fuel enriching whereupon, in a temperaturedependent manner, the extent of the enriching is gradually decreased to assume a value which ensures an optimal exhaust gas composition.

Briefly stated,.according to the invention, in addition to the aforenoted temperature-responsive control element which is disposed in said bypass and which varies the bias ofa spring associated with said pressure control valve, there is provided an additional, second temperature-dependent control element which, during and for a shortperiod immediately subsequent to the starting of the engine, exerts a force opposing that of said spring.

The invention will be better understood, as well as further objects and advantages become more apparent, from the ensuing detailed specification of a preferred, although exemplary, embodiment taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal, in part schematic, sectional view of a fuel injection apparatus according to the invention and FIG. 2 is a diagram illustrating the control pressure of the pressurized liquidas a function of temperature.

DESCRIPTION OF THE EMBODIMENT Turning now to FIG. 1, there is shown a fuel injection apparatus in which the intake air flows from an air filter l to one ormore engine cylinders (not shown) through an air intake tube which comprises a portion 3 in which there is disposed an air sensor 4, a hose connection 5 and an intake tube portion 6 in which there is arranged an arbitrarily operable butterfly valve 7. The air sensor 4 is formed as a disc which is oriented normal to the direction of air flow and which is movable in the intake tube portion 3 as a substantially linear function of the air quantities flowing through the air intake tube. In case of a constant return force applied to the air sensor 4, as well as a constant air pressure prevailing upstream of the air sensor 4, the pressure between the air sensor 4 and the butterfly valve 7 remains substantially constant. The air sensor 4 directly controls a metering and fuel distributor valve 8. The motion of the air sensor 4 is transmitted to the control plunger 12 of the fuel metering valve 8 by means of a nose portion 11 of a lever 10 which is affixed to the air sensor plate 4 and which is pivotable with low friction about a shaft 9. The radial terminal face 13 of the control plunger 12 is exposed to pressurized liquid which serves as the return force for the air sensor 4.

The supply of fuel is effected by a fuel pump 16 which is driven by an electromotor 17 and which draws fuel from a fuel tank 36 forcing it through a conduit 18 to the fuel metering valve 8. From the conduit 18 the fuel is admitted to a channel 19 disposed in a housing of the fuelmetering valve 8. The channel 19 merges into an annular groove 20 from which there extend ports 21 to a cylinder 22 in which the control plunger 12 is reciprocably disposed. In the latter there is provided, by virtue of two spaced lands, an annular circumferential groove 23 which is in continuous communication with the ports 21. Dependent upon the position of the control plunger 12 the annular groove 23 overlaps to a greater or lesser extent control slots 24 through which the fuel may flow from the annular groove .23 into channels 25 which, in turn, lead to the individual fuel injection valves (not shown) disposed in the air intake tube of the internal combustion engine. One part of the fuel flows from the annular groove 20 into a channel 26 and is admitted to an annular groove 27 wherefrom it flows through ports 28 into a conduit 29. The latter is in communication through a damping throttle 30 with the pressure chamber 31 (forming part of the cylinder 22) in which there is disposed the radial work face 13 of the control plunger 12.

Through the conduit 29 the fuel serving as pressurized liquid is admitted to a first pressure control valve 32 which is formed as a flat seat valve including a diaphragm 33 and a stationary valve seat 34. The fuel flowing through the control valve 32 is returned in a depressurized condition into the fuel tank 36 through a return conduit 35. The diaphragm 33 is loaded by a spring 37, the bias of which is changed as a function of operational variables of the internal combustion engine. For this purpose there is provided a three-dimensional cam 38 which is rotatable as a unit with the arbitrarily adjustable butterfly valve 7 and which may be axially displaced as a function of the vacuum prevailing downstream of the butterfly valve 7 in the suction tube. The three-dimensional cam 38 is axially slidably held on the shaft 39 which is integral with the butterfly valve 7. The rotary motion of the shaft 39 is transmitted by means of a pin 40 to the three-dimensional cam 38 which, at one frontal face, is rotatably secured to a diaphragm 41 bounding a vacuum chamber 42. The latter is in communication by means of a conduit 43 with the air intake tube at a location downstream of the butterfly valve 7. If the vacuum is of a sufiiciently large value, the three-dimensional cam 38 is axially displaced by the diaphragm 41 against the force of a return spring 44 disposed in the vacuum chamber 42. A follower pin 45 scans the surface of the three-dimensional cam 38 and through a spring seat disc 46, controls the bias of the spring 37 to affect the pressure of the pressurized liquid serving as the resetting force for the air sensor 4.

From the conduit 29 there extends a conduit 50 which is connected to a second pressure control valve 53 from which there extends a return conduit 55 to the fuel tank 36. The pressure of the pressurized liquid serving as a return force for the air sensor 4 may be controlled as a function of temperature by means of the second pressure control valve 53. The latter is formed as a flat seat valve having a stationary valve seat 57 and a diaphragm 58 which is loaded by a spring 59 in the closing direction of the valve 53.

The chamber 60 accommodating the spring 59 forms one part of a bypass conduit 61, 62 circumventing the butterfly valve 7 in the suction tube. For the sake of clarity the bypass conduit itself is not shown in FIG. 1, only its connections with the suction tube portion 6 and with the pressure control valve 53 are indicated. In chamber 60 there is disposed a plunger piston 64 which controls the flow passage section of the bypass conduit 61, 62 and which also serves as a spring seat disc for the spring 59.

The displacement of the piston plunger 64 is effected by a first temperature-dependent control element (heat expandable regulator) 63 which, when the internal combustion engine is cold, compresses the spring 59 to a lesser extent and opens the bypass 61, 62 to a greater extent than in case of a warm engine. In this manner, under cold engine conditions more pressurized liquid flows through the valve 57, 58 and thus the pressure of the fuel working as a return force is smaller. Consequently, the injected fuelquantities are relatively increased with respect to the air quantities to obtain a richer mixture.

That terminus of the spring 59 which is remote from the control plunger 64 engages a spring seat disc 65 which exerts a force on the diaphragm 58 through an intermediate member 66. The spring seat disc 65 has at its side remote from the spring 59 an opening 67 into which there extends one end of a bimetal spring 68. The other end of the latter is surrounded by a heater element 69 which, together with the bimetallic spring 68, forms a second temperature-dependent control element 68, 69. In the shown position, prior to the operation of the internal combustion engine, a rivet 70 attached to the bimetal spring 68 is in engagement with the spring seat disc 65.

OPERATION OF THE FUEL INJECTION APPARATUS When the internal combustion engine is running, the pump 16 driven by the electromotor 17, draws fuel from the fuel tank 36 and forces the same through the conduit 18 to the fuel metering valve 8. Simultaneously, the engine draws air through the air intake tube 3, 5, 6, as a result of which the air sensor 4 is deflected in a clockwise direction (as viewed in FIG. 1) from its position of rest.

In response to the deflection of the air sensor 4 the lever 10, with its integral nose 11, displaces the control plunger 12 to the left, thus opening the control slots 24 to a greater extent. Thus, the fuel quantity passing through the metering slots 24 and admitted to the fuel injection valves (not shown) corresponds to the setting magnitude of the air sensor 4. From the annular groove 23 of the control plunger 12, one part of the fuel is admitted through the channel 26 into the pressure chamber 31 where it affects the frontal radial face 13 of the control plunger 12. Other parts of the fuel flow from the channel 26 through the conduit 29 to the first pressure control valve 32 and through a conduit 50 to the second pressure control valve 53.

The direct coupling of the air sensor 4 with the control plunger 12 results in a constant ratio between the air quantities and the fuel quantities insofar as the' The measuring magnitudes for load and rpm of an internal combustion engine are the angular position of the butterfly valve and the vacuum in the air intake tube. Consequently, the return force is expediently varied as a function of these two magnitudes. Such variation is brought about by the change in the bias of the spring 37 of the pressure control valve 32 by shifting the spring seat disc 46. The latter shift, in turn, is effected by the rotary and axial motions of the threedimensional cam 38 executed, respectively, in response to the angular position of the butterfly valve 7 and the pressure in the suction tube. If for example, in a full load condition the butterfly valve 7 is in a position in which the suction tube is fully open, then a highest output, that is, a relatively rich air-fuel mixture is desired. Since the bias of the spring 37 of the first pressure control valve 32 determines the pressure of the fuel which affects the radial face 13 of the control plunger 12, the return force affecting the air sensor 4 has to be somewhat reduced to permit the control plunger 12 to be shifted into a position in which the control slots 24 are opened to a greater extent and, accordingly, larger fuel quantities can be injected. Conversely, under partial load conditions, by virtue of a relatively higher pressure exerted on the radial face 13 of the control plunger 12, there is obtained a relatively smaller deflection of the air sensor 4 and, as a result, the air-fuel mixture will be leaner.

When the vehicle with which the internal combustion engine is associated coasts in gear, the threedimensional cam 38, because of the substantial vacuum in the air intake tube, is displaced against the force of the spring 44 so that the spring 37 of the first pressure control valve 32 will be biased to a greater extent. In this manner the return force exerted on the air sensor 4 is increased so that despite the slight air leakage quantities that may flow through the closed butterfly valve 7, there will be no deflection of the air sensor 4 and thus no fuel quantities will be injected.

If first the effect of the second temperature-dependent controlelement 68, 69 is disregarded, in case of a cold engine there is obtained an enriching of the airfuel ratio, since the heat-expandable regulator 63 of the second pressure control valve 53 causes the pressure of the fuel serving as a return force to be decreased in the chamber 31. In this operational condition the plunger piston 64 displaced by the heat-expandable regulator 63 maintains the bypass conduit 61, 62 open. In this manner, the greater engine friction at the cold start of the engine is compensated by a correspondingly higher mixture flow rate.

The first temperature-dependent control element 63 which responds to the coolant water temperature, effects a leaner fuel mixture (by compressing the spring 59 and thus increasing the fuel pressure at the radial work face 13 of the control plunger 12) only with a substantial delay. Since, however, already a few moments following the starting of the engine the cylinder walls, because of the preceding ignitions, have been prewarmed and thus a fuel condensation caused by the previously cold cylinder walls occurs to a decreasing degree, it is expedient to simultaneously reduce the enrichment of the air-fuel mixture to such an extent that a clean run of the engine is ensured. According to the invention, such a decrease in the fuel enriching is ensured by causing the second temperature-dependent control element 68, 69 to work against the spring 59 for a short period immediately after, starting of the internal combustion engine. The heater 69 is energized by, eg closing its electrical circuit simultaneously with turning on the engine ignition.

Turning now to FIG. 2 there is shown the fuel pressure exerted on the control plunger 12 as a function of the coolant water temperature as controlled by the second pressure control valve 53. In a device for the warm-up run of the engine without the second temperature-dependent control element 68, 69, the spring 59 should be designed according to the pressure characteristic curve a. According to the invention, however, the spring 59 is designed to correspond to the pressure characteristic curve b. The cold bimetal spring 68 works against the spring 59 at the moment of starting in such a manner that the curve a is obtained for the engine run after starting. The heat output of the heater element 69 is determined in advance in such a manner that, dependent upon the starting temperature, the bimetal spring 68 is, after a correspondingly short time, bent away from the spring seat disc 65. Consequently, after this occurrence the spring seat disc 65 and thus the diaphragm 58 are loaded only by the spring 59. The transition from the curve a to the curve b occurs, dependent upon the temperature at the starting, along one of the curves c. At normal operating temperatures of the coolant water, the spring 59 remains biased to a constant extent according to the curve d.

That which is claimed is: i

1. In a fuel injection apparatus serving a spark plugignited internal combustion engine operating on fuel continuously injected into the air intake tube thereof, said apparatus being of the type that has (a) an arbitrarily operable butterfly valve disposed in said air intake tube, (b) an air sensor disposed in said air intake tube spaced from said butterfly valve, said air sensor being displaceable by and as a function of the air quantities passing through said air intake tube, (0) a fuel quantity distributor valve for metering the fuel quantities to be injected, (d) means connecting said air sensor with said fuel quantity distributor valve to effect metering of said fuel as a function of the deflection of said air sensor, (e) means supplying a return force affecting said air sensor in opposition to the force exerted thereon by the flow of intake air, said means supplying said return force includes a control plunger operatively connected to said air sensor and cylinder means accommodating said control plunger and containing liquid under pressure exerting said return force on said control plunger, the improvement comprising A. a pressure control valve hydraulically connected to said cylinder means for varying the pressure of said liquid in said cylinder means, said pressure control valve including a spring the bias of which affecting said pressure in said cylinder means,

B. a first temperature-responsive control element sensing the engine temperature and causing an increase in the bias of said spring as the engine temperature increases,

C. a second temperature-responsive control element opposing, when unheated, the operation of said first temperature-responsive control element, and

D. a separate heater means operatively coupled to said second temperature-responsive control element for heating the same causing discontinuance of its opposing effect on said first temperatureresponsive control element.

2. An improvement as defined in claim 1, including means to energize said separate heater means immediately after starting said engine.

3. An improvement as defined in claim 1, said second temperature-responsive control element being formed as a bimetal spring being in engagement, when unheated, with said first-named spring and bending away therefrom when heated.

4. An improvement as defined in claim 1, said pressure control valve being hydraulically connected to said cylinder means downstream thereof.

5. An improvement as defined in claim 1, including A. a bypass channel circumventing said butterfly valve and B. means connected to said spring for varying the flow passage section of said bypass channel simultaneously with the variation of the bias of said spring.

Claims

1. In a fuel injection apparatus serving a spark plug-ignited internal combustion engine operating on fuel continuously injected into the air intake tube thereof, said apparatus being of the type that has (a) an arbitrarily operable butterfly valve disposed in said air intake tube, (b) an air sensor disposed in said air intake tube spaced from said butterfly valve, said air sensor being displaceable by and as a function of the air quantities passing through said air intake tube, (c) a fuel quantity distributor valve for metering the fuel quantities to be injected, (d) means connecting said air sensor with said fuel quantity distributor valve to effect metering of said fuel as a function of the deflection of said air sensor, (e) means supplying a return force affecting said air sensor in opposition to the force exerted thereon by the flow of intake air, said means supplying said return force includes a control plunger operatively connected to said air sensor and cylinder means accommodating said control plunger and containing liquid under pressure exerting said return force on said control plunger, the improvement comprising A. a pressure control valve hydraulically connected to said cylinder means for varying the pressure of said liquid in said cylinder means, said pressure control valve including a spring the bias of which affecting said pressure in said cylinder means, B. a first temperature-responsive control element sensing the engine temperature and causing an increase in the bias of said spring as the engine temperature increases, C. a second temperature-responsive control element opposing, when unheated, the operation of said first temperatureresponsive control element, and D. a separate heater means operatively coupled to said second temperature-responsive control element for heating the same causing discontinuance of its opposing effect on said first temperature-responsive control element.