GB2237660A

GB2237660A - A controller for an injection pump of an internal combustion engine

Info

Publication number: GB2237660A
Application number: GB9018755A
Authority: GB
Inventors: Frank Thoma; Christoph Burckhardt
Original assignee: Daimler Benz AG; Mercedes Benz AG
Current assignee: Daimler Benz AG
Priority date: 1989-08-31
Filing date: 1990-08-28
Publication date: 1991-05-08
Anticipated expiration: 2010-08-28
Also published as: FR2651277A1; IT9048181A1; GB9018755D0; IT9048181A0; GB2237660B; DE3928833A1; DE3928833C2; IT1241517B; FR2651277B1

Abstract

A control system for an injection pump of an internal combustion engine has a basic mechanical arrangement 4, 5, 6, 11 which operates a control rod 7 of the pump in dependence on throttle pedal 3 position and engine speed 11. An electronic arrangement 8-10 and 12-16 is superimposed on the mechanical arrangement to refine the control action. It acts in dependence on engine parameters 14 such as speed, load and temperature and in dependence on ambient parameters 15 such as air pressure and temperature and may be optimised for exhaust emissions etc. The electronic system acts always to reduce the amount of fuel supplied below the level determined by the mechanical system alone. In the event of a failure of the electronic system, the mechanical system retains sufficient movement to provide power for emergency operation. <IMAGE>

Description

1 A controller for an injection DunD of an internal combustion engine The

invention relates to a controller for an injection pump of an aircompressing internal combustion engine driving a vehicle, having a mechanical basic controller, which predetermines a group of quantity curves, a load signal acting via a control spring on a controller linkage, which controller linkage is adapted to actuate a quantity control element of the injection pump and a force formed as a function of the engine rotation speed acting counter to the adjustment movement, brought about by the load signal, of the controller linkage, an adjusting element for injection quantity correction of the fuel quantity, set by the mechanical controller, in the direction of quantity reduction, said adjusting element comprising an electrical servomotor which is actuated by an electrical control device which, in operation, processes internal combustion engine parameters and ambient parameters.

German Offenlegungsschrift 3,430,797 discloses a controller for fuel injection pumps of internal combustion engines, in which a predetermined load signal acts via a control spring on one arm of a two-armed lever of a controller linkage, as a result of which a quantity control element of an injection pump is adjusted in accordance with the preset load value, a force formed as a function of the engine speed acting counter to the swivelling of the lever brought about by the load signal. Arranged on the second arm of the two-armed lever is an adjusting element which swivels the lever as a function of the correction values supplied by an electrical control device and formed from internal combustion engine parameters and ambient parameters, and in this way brings about the correction of the injection quantity, for example _in the form of an injected rininxir unt fnr thp purpose of avoiding s"oking 2 or f or matching to the f uel amount, which drops with rising engine speed.

In this way, the basic group of curves of the mechanical controller is optimized taking into account various criteria by applying correction values calculated in the electrical control device, without intervening in the basic functions of the mechanical controller.

In the event of a failure of the electrical system, it is provided that the lever should be placed by the effect of a spring force in a position in which the delivery rate of the injection pump can be set to zero. A disadvantage of this controller is that, in the event of a failure of the control electronics in its active state and thus in a state which reduces the delivery rate i.e. with the adjusting element activated and, in this position, blocked, the delivery rate may, in certain circumstances, be so low due to the reduced correction that the injected fuel quantity is no longer sufficient to operate the internal combustion engine, for example under load.

The present invention seeks to construct a controller for an injection pump in such a way that, in the event of failure of the control electronics, a reliable emergency operation of a vehicle is guaranteed with extensive maintenance of the optimizing function of the injection quantity.

According to the present invention there is provided a controller for a fuel injection pump of an internal combustion engine for a vehicle, having a mechanical basic controller, which predetermines a group of quantity curves, a load signal acting via a control spring on a controller linkage, which controller linkage is adapted to actuate a quantity control element of the injection pump and a force formed as a function of the engine rotation speed acting counter to the adjustment movement, brought about by the load signal, of the controller linkage, an adjusting element for injection quantity correction of the fuel quantity, set by the npchanical coni-roll-ri, in the 1 3 direction of quantity reduction, said adjusting element comprising an electrical servomotor which is actuated by an electrical control device which, in operation, processes internal combustion engine parameters and ambient parameters, wherein the group of quantity curves of the mechanical controller is limited in the case of maximum loading by the maximum full-load quantity requirement, the maximum admissible limit speed and the idling quantity requirement and the maximum amount of the injection quantity correction is of such a magnitude that, in the event of failure of the adjusting element in the activated state, the power required for emergency operation is available.

Preferably, the amount of the injection quantity correction is inversely proportional to the angular acceleration of the internal combustion engine. The injection quantity correction may be responsive to the engine speed irregularity of the internal combustion engine, and/or the injection quantity correction for the idling quantity requirement may be dependent on the cooling water temperature. In this case, the injection quantity correction for the idling quantity requirement may be dependent on the engine speed. The injection quantity correction for the matching to the group of curves may be engine speed-dependent and/or load- dependent. The injection quantity correction may be dependent on the slip values and acceleration values of the wheels of the vehicle and the injection quantity correction for the limit speed of the internal combustion engine may be transmission-dependent.

A known mechanical controller for an injection pump, for example an idling and final engine speed controller or a variable-speed governor, provides, as a function of the engine speed, a basic group of curves for the injection amount of an air-compressing internal combustion engine. This basic group of curves is limited by the maximum fullload quantity requirement of the internal combustion engine. the TnaXiniir admissible limit speed and the idling 4 quantity requirement designed for maximum loading, i.e. f or cold engine and switched-on loads. Via an adjusting element actuated by an electrical control device, the injection quantity set by the mechanical controller is reduced as a function of internal combustion engine parameters and ambient parameters in such a way that an optimization of the injection amount for every operating point of the internal combustion engine occurs. The maximum correction amount, calculated by the control device, for the injection quantity reduction is in this case calculated to be, at most, of such a magnitude that, in the event of failure of the adjusting element in the activated state - and consequently in the state which reduces the injection quantity - an injection quantity which is still sufficient for the emergency operation of the vehicle even with increased load is available.

An embodiment of the invention is described below by way of example with reference to the drawing, in which:

Figure 1 shows diagrammatically the design of an injection pump of an internal combustion engine with controller, Figure 2 shows a group of injection quantity curves according to the invention.

Figure 1 shows in a diagrammatic manner a known injection pump 1 of an air-compressing internal combustion engine (not shown). The fuel line connections which lead to the individual cylinders of the internal combustion engine are designated by 2. Via a pedal displacement sensor 3, the driver predetermines a reference load signal which acts on the control linkage 4, 5 and, by means of the design of the control spring 6, brings about a characteristic displacement of the control rod 7 as quantity control element, and thus a change of the injection quantity. The actual value of the position of the control rod 7 is detected with the aid of a control rod displacement sensor 8 and, for control purposes, is compared with the reference position provided by the pedal displacerent sensor 3 vie a 1 line 9 to a control device 10. In a known manner, the controller is provided with a centrifugal force measuring device 11 which brings about a force, formed as a function of the engine speed, counter to the adjusting movement, brought about via the accelerator pedal by means of an adjusting linkage/Bowden cable, of the controller linkage 4, 5. An adjusting element 13, which operates counter to the force of a spring 12 and acts on the controller linkage 5, is connected to the controller of the injection pump and when activated it displaces the control rod 7 in the direction of a reduction of the injected fuel quantity. The actuation of the adjusting element 13 occurs via the control device 10 already mentioned above, which detects and evaluates a multiplicity of operating parameters 14 (for example engine speed, load signal, cooling water temperature, etc.) and ambient parameters 15 (for example external air pressure, air temperature etc.) via sensors (not represented). The evaluation occurs in such a way that in the control device 10 a correction quantity is determined which, via the adjusting element 13, brings about a reduction of the fuel quantity, predetermined by the mechanical controller, by means of a displacement of the control rod 7 in the direction of quantity reduction. In this way, it is possible to apply to every point in the group of fuel quantity/engine speed curves predetermined by the mechanical controller a correction value which is dependent on the aforesaid parameters and allows an optimized setting of the internal combustion engine in respect of, for example, smoking, limiting, bucking and the like. For the purpose of actuating the adjusting element 13, the control device 10 also has a driver stage 16 which conditions and amplifies the correction signal. In the event of a failure of the control electronics, for example due to power failure, no correction values can be calculated and actuation of the adjusting element 13 thus also fails. The internal combustion engine can in this case continue to be operated via tne group of - non-optimized - 1 6 curves provided by the mechanical controller. The maximum amount calculated by the control device 10 for the injection quantity correction is of such a magnitude that, in the event of a failure of the adjusting element 13 in its activated state, i.e. with reduced injection quantity, an amount of power required for emergency operation is available to the internal combustion engine. The power must in this case be so high that emergency operation is guaranteed even with increased load, for example inclines or switched-on loads.

A group of injection quantity curves of an internal combustion engine is represented in the second figure. In this case, the injected fuel quantity Q is plotted against the engine speed n. The basic group of curves realized by means of the mechanical controller is drawn in continuous lines. This basic group of curves is limited on the one hand by the maximum full-load quantity requirement of the internal combustion engine, which is realized as a simple straight line 17, and on the other hand by the limiting characteristic line 18, which corresponds to the maximum admissible limit speed of the internal combustion engine. The idling quantity represented by the line 19 is selected in such a way that the internal combustion engine can be operated in idling mode in the cold state and in the case of maximum loading by loads. In addition, a known start amount increase 20 is shown in -this group of curves. Starting from this basic group of curves 17, 18, 19, 20, the control device determines correction values which are dependent on the internal combustion engine parameters and ambient parameters and optimize the injection quantity, and by which the values specified in the basic group of curves are reduced with the aid of the abovenentioned adjusting element. If the control device fails for example as a result of interruption of the power supply, the injection quantities correction brought about by the adjusting element is forcibly eliminated again and the internal combustion engine is operatea with tha non-opt-'s-mized e 7 injection quantities of the basic group of curves. However, if the control fails in the activated state of the adjusting element, for example due to a shorted end stage in the abovementioned driver or due to a short-circuit to earth, the internal combustion engine must then be operated with the reduced injection quantity. For emergency operation, this means that this reduced injection quantity must be adequately dimensioned to be certain of operating a vehicle, for example even on inclines and with increased loading. The correction quantity determined by the control device is consequently always dimensioned in such a way that an emergency operation is possible even with the injection quantity reduced by the correction value. In Figure 2, an injection quantity which is reduced - starting from the full-load quantity 17 - on the basis of various parameters - is drawn in broken lines 21. As shown here, the correction can also give rise to a new final limiting characteristic line 22. The idling characteristic line 19 is also displaced to an idling characteristic line 23 with reduced fuel requirement, for example with rising cooling water temperature or as a function of the engine speed n of the internal combustion engine. Starting from an arbitrarily assumed partial load characteristic line 24 which is represented here by a dot- dash line, the injection quantity is also reduced in an analogous manner to that described above, by a correction quantity dependent on the parameter, which is indicated by the line 25. The line 25 of a corrected partial load injection quantity shows that matching can occur by means of the selection of the correction values as a function of the engine speed n, as could only be realized with purely mechanical controllers used previously with the aid of special applications of springs.

As can be seen from the illustrated characteristic lines, the correction values for each individual operating point of the internal combustion engine can be randomly selecteO, provided that they lie in a region wbicb 8 guarantees an emergency operation. In particular, the correction of the injection quantity can also be used to achieve other objects not directly specific to the internal combustion engine. Thus, it is conceivable that the amount of correction of the injection quantity is selected to be inversely dependent on the angular acceleration of the internal combustion engine, as a result of which the known bucking of a vehicle can be prevented. It is also conceivable to match the injection quantity correction in an adaptive control process to the engine speed irregularity of the internal combustion engine, in order in this way to achieve smoother running of the internal combustion engine. A further correction possibility is to use the slip values measured at the wheels of the vehicle to reduce the torque by means of the injection quantity correction and thus to realize an effective slip control system. If the injection quantity correction is carried out as a function of the transmission step selected in the gearbox of the vehicle, the limit speed of the internal combustion engine can be selected to be different for each transmission ratio. An advantage of this transmissiondependent injection quantity correction consists in the fact that in a higher transmission step a relatively lower limit speed can be realized in order not to overload the internal combustion engine in continuous operation, without it being necessary to dispense with turning off the internal combustion engine in the lower transmission steps and thus with good acceleration values of the vehicle.

Of course, yet other possibilities of exerting influence, which go beyond the examples given here, are conceivable for the injection quantity correction.

The advantage of the invention therefore consists in carrying out an optimization, which is known from electronic controllers and not realizable with a purely mechanical controller, of the injection quantities, determined from a basic group of curves, as a function of internal combustion parameters and anibient paraweters for 9 various application purposes, without it being necessary to dispense with the emergency running properties of a mechanical controller.

1

Claims

Claims

A controller for a fuel injection pump of an internal combustion engine for a vehicle, having a mechanical basic controller, which predetermines a group of quantity curves, a load signal acting via a control spring on a controller linkage, which controller linkage is adapted to actuate a quantity control element of the injection pump and a force f ormed as a function of the engine rotation speed acting counter to the adjustment movement, brought about by the load signal, of the controller linkage, an adjusting element for injection quantity correction of the fuel quantity, set by the mechanical controller, in the direction of quantity reduction, said adjusting element comprising an electrical servomotor which is actuated by an electrical control device which, in operation, processes internal combustion engine parameters and ambient parameters, wherein the group of quantity curves of the mechanical controller is limited in the case of maximum loading by the maximum full-load quantity requirement. the maximum admissible limit speed and the idling quantity requirement and the maximum amount of the injection quantity correction is of such a magnitude that, in the event of failure of the adjusting element in the activated state, the power required for emergency operation is available.
2. A controller f or an injection pump according to Claim 1, wherein the amount of the injection quantity correction is inversely proportional to the angular acceleration of the internal combustion engine.
3. A controller for an injection pump according to Claim 1 or 2, wherein the injection quantity correction is responsive to the engine speed irregularity of the internal combustion engine.

c 11
4. A controller for an injection pump according to any one of Claims 1 to 3, wherein the injection quantity correction for the idling quantity requirement is dependent on the cooling water temperature.,
5. A controller for an injection pump according to Claim 4, wherein the injection quantity correction for the idling quantity requirement is dependent on the engine speed.
6. A controller for an injection pump according to any one of Claims 1 to 5, wherein the injection quantity correction for the matching to the group of curves is engine speed-dependent and/or load-dependent.
7. A controller for an injection pump according to any one of Claims 1 to 6, wherein the injection quantity correction is dependent on the slip values and acceleration values of the wheels of the vehicle.
8. A controller for an injection pump according to any one of Claims 1 to 6, wherein the injection quantity correction for the limit speed of the internal combustion engine is transmission-dependent.
9. A controller for an injection pump of an internal combustion engine for a vehicle, substantially as described herein, with reference to, and as illustrated in, the accompanying drawing.

Published 1991 atIbe Patent Office. State House. 66/71 High Holborn. L4DTidonWCIR 47P. Further copies inay be obtained from Sales Branch, Unit 6, Nine Mile Pbint. Cwnificlinfach, Cross Keys, Newport. NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray. Kent.