GB2216596A

GB2216596A - Air intake throttle control for fuel-injection engine

Info

Publication number: GB2216596A
Application number: GB8806135A
Authority: GB
Inventors: Alexander Robertson
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-03-15
Filing date: 1988-03-15
Publication date: 1989-10-11
Anticipated expiration: 2008-03-15
Also published as: GB2216596B; GB8806135D0

Abstract

A diaphragm actuator 13 controls the throttle valve 11 in response to at least the pressures upstream and downstream of the valve. The fuel injection pump lever (5, Fig.3) may be linked to an atmospheric air bleed control needle valve (31) which influence the actuator 13 or direct to the valve 11 (Fig. 4). The actuator air bleed needle valve (36, Fig. 5) may be positioned in response to an electronic control unit (38) with intake pressure, throttle pedal, pump lever, throttle valve, coolant temperature, air temperature and engine speed inputs. <IMAGE>

Description

',CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINES" Description The present invention relates to a control device for internal combustion (I.C.) engines, and more specifically relates to an air flow control for I.C.

engines of the diesel or fuel injection type.

Diesel (or compression ignition) engines are provided with a fuel pump delivery metered quantities of diesel fuel to fuel injectors on each of the engine cylinders, while air flows to the cylinders via an air induction system during an air induction stroke, and each fuel injector injects the fuel into its respective cylinder during a compression stroke whereupon the fuel is ignited by high-temperature compression effect (compression ratios of 20:1 may be present) to provide a power stroke. Finally, exhaust gases are discharged via an exhaust manifold by virtue of an engine exhaust stroke.

Increased power is obtained by increasing the quantity of each individual fuel injection into the engine by appropriate setting of the fuel pump. Petrol-fuel injection engines operate somewhat similarly, the fuel (petrol) again being injected to the cylinder during the compression stroke, but in this case relatively lower compression ratios (eg less than 10:1) require to be used due to the chemical nature of the petrol fuel so that spark ignition effect is employed for ignition of the air/fuel mixture. Hereinafter both the above types of I.C. engines are referred to as fuel injection type I.C.

engines.

It is the main object of the present invention to improve the efficiency of fuel-injection type I.C.engines (especially diesel engines) by controlling the air flow into the engine.

According to the present invention air flow control apparatus for use in a fuel-injection type I.C. engine comprises air duct means for inclusion in the air induction system of the engine, air flow control means in said duct means, and acutator means operatively connected to said air flow control means to set said control means dependent on selected operating conditions or parameters present in the engine. Preferably the actuator means sets the control means dependent on pressure conditions in the air duct means (or in the air induction system generally), and preferably the actuator means comprises a chamber-housed diaphragm device. The air flow control means preferably comprises a movable throttle-plate.

The present invention is also a fuel-injection type I.C. engine fitted with the aforesaid air flow control apparatus.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings wherein: Fig. 1 shows a schematic pictoral view of a diesel engine suitable for use with the present invention; Fig. 2 shows a schematic side view of an air flow control for the air induction system of a diesel engine, in accordance with one embodiment of the present invention; Fig. 3 shows a similar view of an air flow control according to a second embodiment; Fig. 4a shows an air flow control according to a third embodiment with Figs 4b and 4c showing operational modes of the Fig. 4a control; and while Fig Sa shows yet a further embodiment; Fig. 6 shows a graph of specific fuel consumption against air/fuel ratio in a diesel engine.

Referring to Fig. 1, a diesel engine 1 is of four cylinder in-line form (although all other cylinder numbers and configurations are possible) and includes a fuel pump 2 deliver ing metered quantities of diesel fuel to fuel injectors 3a b c d via fuel lines 4a - 4d, each of the injectors 3a - 3d being associated with a respective cylinder of the engine 1. The pump 2 has a pivoting fuel delivery control lever 5 which is connected by a throttle cable 5a to a foot operated throttle pedal (not shown in Fig.l) whereby the lever 5 can be moved from a "closed" position C to a fully "open" position 0 (shown dashed) for zero to maximum fuel delivery rates. Suitable timing means (not shown) are provided to enable correct timing of fuel injection into the cylinders from the injectors 3a - 3d.

Air is delivered to the cylinders by an air induction system comprising air manifold 6 while exhaust gases are discharged via exhaust manifold 7.

In accordance with the present invention, an air flow control unit is provided for the air induction system of the engine 1 and Fig. 2 shows a first (basic) inventive embodiment of this control unit. Thus, referring to Fig.

2, the air flow control unit comprises an air duct 10 in which there is pivotally mounted an air throttling plate 11. A flexible diaphragm 12 is housed in a housing 13 mounted on the duct 10 and the diaphragm 12 is operatively connected to the plate 11 by means of a connecting rod device 14 and a bellcrank 15. The device 14 comprises a spindle 16 attached to the diaphragm 12 and extending into a casing 17 pivotally connected at the bottom end to the bellcrank 15, a spring 18 being located between the spindle 16 and the casing 17 whereby the rod device 14 embodies an override spring (or damping) effect.

Further, the lower end of the housing 13 below the diaphragm is fluidly connected to the upstream side of the throttling plate 11 by means of a conduit 19 while the upper end of the housing 13 above the diaphragm is connected to the downstream side of the throttling plate 11 by means of a conduit 21 and a suitably sized orifice (or restriction) element 22. Further, for a naturally (normal) aspirated engine said casing upper end is additionally connected to said upstream side by a conduit 23 and sized orifice 24. A diaphragm return spring 25 is present in the dashpot upper end while a stop screw 26 acts on an arm of the bellcrank to limit the minimum open position of the place 11. A screw 26a limits the maximum opening of the plate 11.

Where the engine 1 is of the blower or turbo-charged type rather than naturally aspirated the conduit 23 should be connected to atmosphere via a suitably sized orifice element 27 rather than to the upstream side of the duct 10 since in this case the upstream side will of course be at above atmospheric pressure. A connection via orifice 27 rather than via orifice 24 can also be used for a naturally aspirated engine. Additionally for a naturally aspirated engine the connection to the lower end of the casing 13 could be via an inlet 19a on the casing

directly from atmosphere rather via inlet 19 from duct 10. Conveniently the air flow control unit can be fitted to the engine 1 by attaching the duct 10 to an inlet of the air manifold 6 as shown - suitable connecting flanges will be present to enable this fitting.

Further, desired air treatment devices such as an air cleaner can be joined to the outer end of the fitted duct 10. The air flow control could also be located at the inlet side of the air cleaner.

The position of the diaphragm 12 (and also the setting of the plate 11) depends on the pressure differential across the diaphragm 11 ie on pressures P1 and P2.

The throttling plate 11 creates a depression (P3) in the duct 10, and with increased engine speed and power output the pressure P3 at the plate downstream side reduces so causing the diaphragm 12 to move outwardly and so cause the plate 11 to move to a more open postion. Pressure P2 is dependent on pressures P1 and P3 and the component dependent of pressure P 1 will limit the maximum degree of outward movement of the diaphragm 12.

The air flow control shown in Fig. 3 is similar to that of Fig. 2 and like parts carry like reference numerals. However in this case the "atmospheric" pressure component of pressure P2 is delivered via an atmospheric needle-controlled orifice 30 the needle 31 of which is connected to the fuel pump lever 5 so that the orifice 30 has a maximum opening at the engine idle position (shown dashed) and minimum opening et the engine full power position (full line). The arrangement is therefore such that the value of the relative depression is controlled by varying the opening (dimension) of the orifice 30 as a function of the engine throttle/pump (injection) lever volume position.

In Fig. 4a, an air flow control is shown similar to that of Fig. 2 but additionally in this case the throttling plate 11 is connected to the fuel pump lever 5 by a mechanical connection 32 for example in the form of a cable link. However as will be appreciated the override spring device 14 provides a differential affect between the movements of the spindle 16 and the cable link 32.

The dashed line shows the link 32 in the maximum opening position. Further the vehicle throttle pedal 33 includes a limiter device 33A for limiting the movement of the fuel control lever 5: the pump lever maximum stroke is therefore limited by the selected position of the vehicle throttle pedal 33. Referring to Figs. 4b and 4c, the override spring device 14 enables the plate 11 to have a suitable setting for an accelerating mode (Fig. 4b) ie pedal 33 severely depressed but for substantially the same setting to be present for a cruising mode (Fig. 4c) with the pedal 33 relaxed.

The air flow control of Fig. 5 has similarity to that of Fig. 3 and again the pressure P2 is controlled by a needle-controlled atmospheric orifice element 35. The needle 36 of the element 35 is positioned by a solenoid 37 which receives operating signals G from an electronic control unit 38 via a line 39. Various selected parameter input signals are fed into the unit 38, and these signals can for example be generated by:a) a vacuum/pressure module sensor 40 delivering a signal dependent on the depression in the duct 10.

b) a solenoid control valve 41 giving a signal dependent on the pump lever setting; c) an air temperature sensor 43; d) a potentiometer 44 signaling the position of the plate 11; e) 8 potentiometer 45, indicating throttle pedal (lever) setting; f) coolant temperature sensor 46; and g) an engine R.P.M/TDC/phase sensor 47.

The angular potentiometer 44 can be fitted to the throttle plate shaft. The unit 38 processes the various input signals to generate an output signal G for the solenoid 37 and it is preferable that the solenoid 37 varies the effective induction relative depression P2 at the same instant as adjusting the pump lever 5 (for example by means of connection 48) via a DC or stepper motor dependent on the speed and load requirements.

Further, by including appropriate adjustments the air flow control of the present invention could be used to facilitate an I C engine running as a multi-fuel engine (eg dieselpetrol): in this case for Fig. 5 switching circuit 50 would be present for switching from one fuel operating mode to the other. The control will enable operation at the higher compression ratios for the petrol mode.

Until now a diesel engine consumed its air at atmospheric pressure (naturally aspirated) and controlled its power output by the quantity of fuel injected which is basically controlled by the vehicle accelerator pedal (33).

ie Low fuel flow : Low power High fuel flow : High power Since the air flow consumed per induction stroke is a constant, then the Air Fuel Ratio (AFR) must vary AM Flow as the power. AFR = Fuel Flow ie Low fuel flow : High AFR High fuel flow : Low AFR In practice at idle AFR = 100 to 1 In practice at Wide Open Throttle (WOT) = 17 to 1.

The WOT AFR Value is normally controlled by the "Smoke Level" and not by the maximum possible power.

For any particular Load and Speed, the curve of Specific Fuel Consumption (SFC) is as shown in Fig. 6. As can be seen in Fig. 6 the best S.F.C. is in the range A-B of the AFR while beyond C there will be excessive engine smoking. A high percentage of the increase in S.F.C. with increasing AFR can be attributed to the inability of good flame propagation in a lean mixture.

The above described air flow control units of the present invention serve to return the AFR towards the area of minimum specific value by limiting the maximum AFR value under all speed and load ranges through control of the quantity of air consumed.

The invention gives the following advantages :1. Improvement in fuel economy through programmed/ specified relative depressions giving AFR range.

2. Reduction in mechanical/combustion noise level through effective lower compression ratio and rate of pressure rise, through lower quantity of inducted mass air.

3. Reduction in level of vibration as a result of lower quantity of mass air.

4. Lower idle speed and fuel requirements over the engine operative range.

5. Improved accelaration and throttle pedal response.

6. Easier starting at lower temperature.

The induction depression can be utilised to operate servo brakes direct, thus saving the cost of a vacuum pump (and the power absorbed).

The rate of deceleration is reduced due to lower pumping losses, with magnifold pressures, saving fuel.

The lower pumping loss contributes to noise reduction/vibration reduction/lower noise/lower engine stress.

The lower induction manifold pressure can be utilised as a motivating force for introducing Exhaust Gas Recirculation (EGR) into the air induction system to reduce the level of NOX (Nitried Oxides) required by law for emission control. This system can accept higher levels of EGR than normal due to lower levels of AFR being utilised per power stroke.

The term elative Depression used above covers systems which function with a turbo or blower (instead of naturally aspirated) in which case there is in fact no depression but simply a drop in pressure.

The present invention is equally effective with turbo or blower charged engines.

The size of engine, the invention can be applied to is not limited.

The internal dimensions of the unit are decided by the size and maximum RPM of the engine and number of cylinder per unit and relative depression range.

The relative depression varies with percentage of power output and the limits may be for example 250mm maximum at idle and 38mm maximum at Wide open throttle (WOT).

The values in between being decided by a balance of performance fuel and economy.

The significant feature of the above described air flow control units of the present invention is that there is automatic feed back of the throttle plate control signal.

The improvement in flame propogation through reduced AFR and reduction in pumping losses far exceeds the reduction in Thermal efficiency with lower effective compression pressure resulting in the improvements claimed.

The invention may also be used with petrol fuel injection engines.

In a petrol injection engine fitted with a conventional throttle, the throttle will be located downstream of the air flow control unit. As is present practice the petrol injector system would be of electronic controlled form (ie a crankshaft driven fuel pump would not be present with electronic fuel injection) and the fuel quantities injected could be controlled from the elec tronic control unit operator of Fig. 5.

Claims

CLAIMS:

1. Air flow control apparatus for use in a fuel-injection type I.C.

engine comprising air duct means for inclusion in the air induction system of the engine, air flow control means in said duct means, and actuator means operatively connected to said air flow control means to set said control means dependent on selected operating conditions or parameters present in the engine.

2. Air-flow control apparatus as claimed in claim 1, wherein the actuator means sets the control means dependent on pressure conditions in the air duct means or in the air induction system generally.

3. Air-flow control apparatus as claimed in claim 1 or 2, wherein the actuator means comprises a chamber-housed diaphragm device.

4. Air-flow control apparatus as claimed in any one of the preceding claims, wherein the air flow control means comprises a movable throttleplate

5. Air-flow control apparatus as claimed in claim 3, wherein the outer side of the diaphragm of the device is connected to the downstream side of the air-flow control device while the inner side of the diaphragm is connected to the upstream side of the air-flow control device or to atmosphere.

6. Air-flow control apparatus as claimed in any one of the preceding claims wherein the actuator means includes a connecting rod device comprising first and second connecting rods with spring means between said connecting rods to permit relative overtravel movements between said connecting rods.

7. Air flow-control apparatus as claimed in claim 3 or 5, wherein an air-throttle or bleed device is provided influencing pressure conditions in the outer side of the diaphragm.

8. Air-flow control apparatus as claimed in claim 7, wherein said airthrottle device is operatively connected to a controller of the fuel supply system of the engine whereby the throttle device is set dependent on the fuel supply rate.

9. Air-flow control device according to any one of the preceding claims, wherein a connecting link links the actuator means to a controller of the fuel supply means of the engine.

10. Air-flow control apparatus as claimed in claim 7, wherein an electronic control unit is provided receiving input signals representing selected operating parameters of the engine, said control unit assessing said input signals to generate a control signal which is passed to said air-throttle or bleed device for setting of the bleed device.

11. Air low control apparatus as claimed in claim 10, wherein said selected operating parameters are chosen from any of (a) pressure downstream of air flow control means (b) induction air temperature (c) fuel supply rate (d) engine temperature, (e) engine speed and (f) position of air-flow control means.

12. Air-flow control apparatus as claimed in claim 10, wherein means are provided associated with said electronic control unit which means are suitable to enable the engine to operate on different types of fuel.

13. Air-flow control apparatus as claimed in claim 12, wherein said means includes a switching circuit.

14. Air-flow control apparatus substantially as hereinbefore described with reference to and as illustrated in any one of Figs. 2, 3, 4a/b/c, or Fig. 5 of the accompanying drawings.

15. A fuel-injection type I.C. engine including air low control apparatus as claimed in any one of the preceding claims.