GB2043169A - Combustion mixture regulating apparatus for IC engines - Google Patents

Abstract

The composition of mixture supplied to an internal combustion engine is controlled by an exhaust gas recirculation valve (9) (9), a device (18) for metering the injected fuel flow rate and a device (42) for measuring the induction air flow rate. From the air flow rate, a value is derived for the required fuel flow rate and, when a deviation arises between the actual fuel flow rate and the desired fuel flow rate, a control signal in the form of a control pressure is produced, corresponding to which the exhaust gas recirculation flow rate is modified. The control pressure is compared in a second comparator apparatus (56) with a set value to control an exhaust gas recirculation valve (11) and is compared in a third comparator apparatus (61) with a set value, by which a correction element acting upon a flow adjustment element (63) of the fuel metering device (18) can be actuated. The actuation is carried out by an auxiliary energy source, the effect of which is controlled by the comparator apparatuses. <IMAGE>

Description

SPECIFICATION Combustion mixture regulating apparatus The present invention relates to an apparatus for regulating the combustion mixture introduced into an internal combustion engine.

According to the present invention there is provided an apparatus for regulating the air fuel ratio of the combustion mixture to be introduced into an internal combustion engine, comprising means to provide a first control parameter which is variable in accordance with the difference between the actual fuel flow into the engine and a fuel flow corresponding to the actual air flow, means to provide a second control parameter in accordance with a difference between the first control signal and a predetermined parameter, and regulating means actuable in response to the second control parameter to regulate the quantity of exhaust gas recycled into the engine.

Embodiments of the present invention will now be more particularly described by way of example and with reference to the accompanying drawings in which: Figure 1 shows an embodiment of the present invention Figure 2 shows an embodiment of a second comparator comprising a spherical closure element, and Figure 3 shows an embodiment in which a second and a third comparator comprise a common valve plunger, which is displaceable by control pressure against a restoring force.

In the embodiment shown in Fig. 1 a schematically illustrated internal combustion engine 1 comprises an induction duct 2 and an exhaust manifold 3. At the inlet end the induction duct 2 is provided with an air filter 5, followed by a profiled diffusor 6 diverging in the direction of flow. Downstream of the diffuser 6, an exhaust gas recycling duct 7 leading from the exhaust gas manifold 3 enters the induction duct, a pneumatically actuated exhaust gas recycling valve 9 being disposed in this recycling duct.This valve comprises a throttling element 11 in the form of a disc valve, the shaft end of which is connected to an actuator diaphragm 1 3 of a first actuating apparatus 1 4. The actuator diapheragm is subjected on one side to atmospheric air and on the other side encloses a working chamber 1 5 in the housing of the actuating apparatus and is loaded from this side by the prestressing force of a spring 1 6 in the direction of closure of the throttling element 11.

The internal combustion engine is supplied with fuel by a fuel metering device in the form of a fuel injection pump 1 8. This may, as illustrated, be a series injection pump of known construction, or a distributer injection pump. The injection pump is supplied with fuel by a fuel delivery pump 1 9 from a fuel storage tank 20 via a fuel supply line 21. A fuel filter 22 is connected immediately downstream of the fuel delivery pump 19, and a pressure regulating valve 24 is provided in parallel with the fuel delivery pump in a recycling line to the fuel storage tank. With this regulating valve a desired, constant fuel delivery pressure can be maintained which, however, can be influenced when necessary in accordance with selected operating parameters such as atmospheric pressure or temperature.

The fuel supply line 21 leads through a first pressure chamber 25 of a differential pressure valve 26 to a guide bore 27 for a control plunger 30, provided with an annular groove 29 and serving as a throttle element in the fuel supply line. Depending upon the position of the control plunger 30, one of the boundary edges of the annular groove 29 exposes a greater or lesser metering cross-section 31 or passage cross-section of the fuel supply line 21 leading into the guide bore 27 in the region of the annular groove 29.Downstream of the metering cross-section, the fuel supply line leads out of the guide bore 27 and through a second pressure chamber 32 of the differential pressure valve to the fuel injection pump 1 8. The displacement capability of the control plunger 30 with respect to the reemergence of the fuel supply line 21 is so designed that this supply line is permanently in communication with the annular groove 29 and with the annular space formed between this groove and the guide bore 27.

The first pressure chamber 25 of the differential pressure valve 26 is separated by a diaphragm 33 from the second pressure chamber 32. In the latter chamber, a compression spring 34 biasing the diaphragm 33 in its adjustment direction is disposed. Into the first pressure chamber 21 a control line 35 projects in the manner of a stub pipe such that its outlet opening 36 is parallel with the diaphragm surface and the actuator diaphragm 33 and outlet opening 36 together constitute a valve. Thus, depending upon the deflection of the diaphragm 33, the outlet opening 36 of the control line 35 is opened or closed to a greater or lesser extent. The position of the diaphragm determines the quantity of fuel flowing out there.

The pressure chamber 38 enclosed by the control plunger 30 in the guide bore 27 formed as a blind hole is permanently connected via fixed throttle 39 to the fuel supply line 21 upstream of the metering cross-section 31. In the embodiment shown in Fig. 1 a connecting duct 40 is provided for this purpose between guide bore 27 and first pressure chamber 25. In this manner a regulated, substantially constant fuel pressure acts on the control plunger 30, causing the control plunger 30 to be pressed onto a pivot arm 41. The pivot arm 41 is journalled at one end with low friction, and at the other end extends into the region of the air diffusor 6 there is attached a baffle disc 42 disposed transversely of the air flow direction.This baffle disc is deflected by the pressure of the airstream or the differential pressure acting on the disc in opposition to the substantially constant force produced by the fuel pressure and transmitted from the control plunger 30.

With the assistance of the profiling of the diffusor 6, it is possible to achieve the result that different adjustment travels of the disc are required for the continuous increasing of the free annular area between the baffle disc 42 and the diffuser wall, when the pressure difference on the disc remains constant. It is likewise possible, for example by a slit-shaped form of the metering cross-section 31, to achieve the result that the metering crosssection changes linearly with the adjustment travel of the control plunger 30, which is adjusted in accordance with the deflection of the baffle disc 42.By the profiling of the diffusor 6, with the restoring force maintained constant and with a constant pressure drop at the metering cross-section 31 set by the differential pressure valve 26, it is possible to obtain in different operating ranges an appropriate ratio of airflow towards the internal combustion engine to the fuel flow which is supplied to the fuel injection pump.

When the differential pressure at the metering cross-section 31 changes, a correction is carried out by the device now to be described.

The control line 35 leads for this purpose into a working chamber 43 of a pressure fluid-operated actuating motor 44. Furthermore, a relief line 37 leads from the control pressure line 35 back to the fuel storage tank 20, a discharge throttle 45 being disposed between them, at which the control pressure existing in the control pressure line 35 and in the working chamber 43 builds up. Depending upon the deflection of the diaphragm 33, this control pressure is modified.

The actuating motor 44 comprises as an actuating element, a diaphragm 46, which encloses the working chamber 43 and is loaded on its opposite side by a compression spring 47. A closure element of a three-way valve is connected to the diaphragm 46. The closure element comprises a valve plunger 49, which is slidable in a sealed manner in a bore 50 in accordance with the adjustment movement of the diaphragm 46. A first annular groove 51 and a second annular groove 52 are disposed on the valve plunger 49. In a central position of the valve plunger 49, the annular space formed between the first annular groove 51 and the bore 50 is in communication with a pipe 48 leading to the surrounding atmosphere.At this position of the plunger 49, the annular space formed between the second annular groove 52 and the bore 50 is in communication via an actuating medium supply line 53 with an actuating medium source 54. This source comprises in the embodiment illustrated, a vacuum tank which is evacuated, for instance, by a vacuum pump 55.

A further connecting line 57, extending from the bore 50, is closed in the aforementioned central position by the piston portion 58 between the first and second annular grooves. The connecting line 57 leads to the working chamber 1 5 of the first actuating device 14.

The above described device operates as follows: If, starting from a steady operating state of the internal combustion engine, a flow adjustment device 63 of the fuel injection pump 1 8 is adjusted via an actuating lever 60 towards increased fuel flow, then more fuel must be supplied accordingly to the injection pump via the fuel supply line 21. With an initially constant setting of the control plunger 30 this leads, however, to a pressure drop in the second pressure chamber 32 of the differential pressure valve 26. This differential pressure valve serves as a first comparator apparatus, by which the quantity of fuel actually supplied to the internal combustion engine is compared with a set-point fuel flow which is derived from the inducted fresh air flow rate.

This is done by adjusting the control plunger 30 and the corresponding change to the metering cross-section 31. With a constant pressure drop at the metering cross-section 31, the set-point fuel flow is thereby determined.

If the actual fuel flow taken from the fuel injection pump differs from this set-point fuel flow, then the aforementioned reduction in the pressure in the second pressure chamber 32 and a change in the differential pressure set at the metering cross-section 31 occurs.

This change causes an adjustment of the diaphragm 33, in the present case against the force of the spring 34, and leads to an increase in the size of the aperture 36. By the now increased fuel flow discharge rate here, which represents the result of the comparison and the deviation from the set-point, the control pressure in the control pressure line 35 and in the operating chamber 43 of the actuating motor 44 increases under the influence of the fixed discharge throttle 45. The diaphragm 46 of the motor 44 is now adjusted against the force of the spring 47 and the valve plunger 49 is displaced from its neutral central position. The connecting line 57 thus comes into communication with the first annular groove 51 and via this groove with the atmosphere. The working chamber 1 5 of the first actuating apparatus 14 is vented, so that the throttling element 11 is moved under the action of the spring 1 6 in the closure direction. Thus the magnitude of the recycled exhaust gas flow rates is reduced or entirely interrupted. The reduced proportion of exhaust gas to the total volume inducted by the internal combustion engine is now replaced by fresh air. As a result of the initially increased vacuum obtaining downstream of the baffle disc 42 this baffle disc is deflected until an equilibrium of forces again exists at the baffle disc. The control plunger 30 is accordingly displaced and the fuel metering cross-section 31 increased until once again the pressure drop set by the differential pressure valve 26 is again reached at this crosssection.

The above described control operation takes place in the opposite direction when a reduction in the fuel injection occurs. The actuating motor 44 in conjunction with the valve plunger 49 and the spring 47 constitutes a second comparator apparatus 56. In this apparatus, the control pressure building up in the control line 35 is compared with a setpoint which is defined from the spring characteristic of the compression spring 47 in conjunction with the association of the piston component 58 with the inlet opening to the connecting line 57 in the bore 50. With this comparator appratus, the exact zero point of the exhaust gas recycling can be determined.

Intermediate positions of the throttling element can also be maintained, in that the piston component 58 closes the connecting line 57 and a partial vacuum is retained in the working chamber 1 5 as a mixed pressure of the atmospheric pressure and the vacuum obtaining in the actuating medium pressure source. A high working pressure can with advantage be used in this embodiment for rapidly actuating the throotling element 11 and thus increasing the control speed. The construction of the second comparator apparatus permits a rapid control result with even a slight stroke of the diaphragm 46. The described device may comprise, for example, plastics injection mouldings, and is very simple to construct. The method of functioning is influenced to only a very slight extent by friction.For bringing high actuating pressures into action, only slight fuel pressures are necessary in the control pressure line 35. A reliable separation of the control pressure circuit and the fuel circuit from the environment is obtained by the diaphragm 46. The fuel is furthermore not subjected to the temperatures existing at an exhaust gas recycling valve, as it is in known constructions of exhaust gas recycling control devices.

With the device shown in Fig. 1, the recycled exhaust gas flow rate is regulated in such a manner that a minimum excess air for combustion remains. It is, however, possible when the induction duct or induction filter become dirty or where the exhaust gas recycling valve is not tight, that although the throttling element in the exhaust gas recycling line is situated completely in its closed position, the inducted air flow is not sufficient for complete combustion of the metered fuel flow. In this case, an auxiliary device may be provided, which is shown in broken lines in Fig. 1. This additional device comprises a third comparator apparatus 6 1 which is constructed in a similar manner to the second comparator apparatus 56. A control pressure line 35' leads from the control pressure line 35 to the third comparator apparatus.Furthermore, a second actuating medium feed line 53' branches from the actuating medium source 54 and leads to a first annular groove 51' of the third comparator apparatus. A second annular groove 52' is connected to atmosphere. In an analogous manner to the second comparator apparatus 56, a connecting line 57' leads to a working chamber 62 of a second actuating apparatus 64 which is essentially of the same construction as the first actuating apparatus 1 4. A spring-loaded actuating diaphragm 65 of this actuating apparatus is connected via a rod 66 to the flow adjustment element 63 of the fuel injection pump in such a manner that, when a vacuum occurs in the working chamber 62 and the resultant deflection of the actuating diaphragm 65 occurs in opposition to the force of the spring, the flow adjustment element 63 is adjusted towards reduced fuel injection flow.The flow adjustment element 63 is resiliently coupled via the regulator to the adjusting lever 60, so that independent movement is possible.

The third comparator apparatus 61 is so arranged that it is not until after the exhaust gas recycling valve 9 is closed, as the pressure rises in the line 35, that the connection between the actuating medium feed line 53' and the connecting line 57' is made via the first annular groove 51' and with the assistance of the second actuating apparatus 64 the position of the flow adjustment element is corrected.If therefore, even after the exhaust gas recycling valve has closed, the injected fuel flow rate is too large by comparison with the inducted air flow, then the control pressure in the control pressure line 35' rises further in the above described manner, so that from a specific point, which is determined by the restoring force of the spring in the third comparator apparatus 61 and the position of the first annular groove 51' relative to the inlet of the connecting line 57', the second actuating apparatus 64 is subjected to pressurized medium, in order to reduce the fuel injection rate until a desired fuel-air ratio is achieved.

By changing the spring force in the comparator apparatuses as a function of the valve plunger stroke, a different fuel/air ratio (air number A) can be applied at full load from that at part load, where the exhaust gas recycling valve can be held in a partly opened position when the connecting line 57 is closed.

Fig. 2 shows another embodiment of the second comparator apparatus 56 of third com parator apparatus 61. An actuating motor 68 is provided, which comprises an actuating diaphragm 69 tightly enclosing a working chamber 70 in a housing 71 of the actuating motor. On the opposite side, the actuating diaphragm is loaded by a compression spring 73. The control pressure line 35 or 35' re spectively leads into the working chamber 70.

A three-way valve 74 is connected to the actuating motor, as also in the second com parator apparatus 56 and third comparator apparatus 61. The three-way valve comprises a valve body which is split into two parts, the one part 75 being firmly connected to the housing 71 of the actuating motor. Together with the other part 77 of the valve body a cavity 76 is enclosed, in which there is dis posed, as a valve closure member, a ball 79 fixed to a shaft 78. The shaft 78 projects into the surrounding atmosphere through a connecting bore 80, in the valve body portion 75, of the cavity 76 and is firmly attached at its end to the actuating diaphragm 69. The inlet of the connecting bore 80 into the cavity 76 is formed as a valve seating 81, to which the ball 79 acts as a valve closure member.

The actuating medium feed line 53 and 53' respectively leads into the cavity coaxially to the connecting bore 80 and on the opposite side. This inlet also acts as a valve seating 82, to which the ball 79 is adapted. In addition, the connecting line 57 and 57' respectively leads unclosably out of the cavity-76 to the corresponding actuator apparatus.

This embodiment has the advantage that adjustment of the valve closure member is not influenced by any friction. Freezing up at low temperatures or difficulties in operation are not to be expected in this embodiment. The device is simple to construct and can advantageously also comprise plastics injection moulded components.

The embodiment shown in Fig. 3 illustrates a construction, in which the second and third comparator apparatus have been combined into one common apparatus. The forming of the control pressure is carried out in the same manner as in the embodiment shown in Fig. 1 and does not need to be explained here.

Instead of the second and third comparator apparatuses, a control plunger 84 is provided, which is displaceable inside a closed cylinder 85. Between a first end face 86 of the cylinder and the opposite end face of the control plunger a compression spring 87 is mounted.

A chamber 97 enclosed there in the cylinder 85 is permanently connected via a bore 88 to atmosphere. Between the opposite second end face 89 of the cylinder and the other end face of the control plunger 34, a working chamber 90 is enclosed in a seated manner, into which the control pressure line 35 leads.

The control plunger 84 comprises three external annular grooves, of which the two outermost annular grooves, the outer annular groove 91 and outer annular groove 92, are in communication with an axial blind bore 93 provided in the control plunger 84 and lead ing into the chamber 97. A rib 95 disposed between a central external annular groove 94 and the first annular groove 91 and a rib 96 disposed between the central annular groove 94 and the second external annular groove 92 have a width which is at least equal to the diameter of an actuating medium feed line 53 leading into the cylinder 85 or that of the connecting lines 57 and 57' respectively lead ing from the cylinder 85 to the first actuator apparatus 1 4 and second actuator apparatus 64.

The device operates as follows: In an operation of the internal combustion engine, in which the inducted air and the injected fuel flow are in the desired ratio to each other, the control plunger 84 is situated in the central position illustrated. The actuating medium feed line 53 is now in communication with the central annular groove 94.

The connecting line 57', which leads to the second actuator apparatus 64 which operates the flow adjustment element of the injection pump, is connected via the second annular groove 92, the blind bore 93 and the bore 88 to atmosphere. The working chamber of the second actuator apparatus 64 is thus vented, so that the rod 66 is lifted off the flow adjustment element under the action of the restoring spring and exerts no influence, even in the full-load position of the flow adjustment element. The connecting line 57, which leads to the working chamber of the first actuator apparatus 14, is closed by the first rib 95 in the central position of the control plunger 84.

If a change now occurs in the control pressure in the control pressure line 35, then, for example, the control plunger 84 is displaced towards the left as the pressure increases against the force of the spring 87. As a result the connecting line 57 comes into communication with the first annular groove 91, so that atmospheric pressure can pass via the blind bore 93 into the working chamber 1 5 of the first actuator apparatus 14. Consequently, the compression spring 1 6 can relax and causes the throttling element 11 to move in the closure direction.

The above described operation corresponds to a state, in which too little fresh air reaches the internal combustion engine. If the fresh air proportion is still too low, even after the exhaust gas recycling valve 9 has closed, then the pressure in the control pressure line 35 rises further. Corresponding to this higher pressure, the control plunger 84 is displaced further towards the left against the force of the spring 87, until the connecting line 57' comes into communication with the central annular groove 94. From this instant onwards, the vacuum can penetrate from the vacuum storage vessel 54 into the working chamber 62 of the second actuator apparatus 64. The actuating diaphragm 65 is now adjusted against the force of the spring and the rod 66 is brought into contact with the flow adjustment element 63.Under the action of the vacuum, the flow adjustment element is then displaced until the injected fuel flow has become so small that the control pressure forming in the control pressure line 35 has again decreased.

If a downward regulation of the fuel injection rate is no longer necessary, then the control pressure falls in such a manner that the control plunger 84 is displaced towards the right as far as the illustrated position or, if necessary, still further, so that the connecting line 57' is entirely closed by the control plunger and the connecting line 57 comes into communication with the central annular groove 94. In this position, the vacuum can reach the working chamber 1 5 of the first actuator apparatus 1 4 and thereby cause opening of the exhaust recycling valve. When an admissible exhaust gas recycling rate has been reached, at which the desired fuel-air ratio is still maintained, the control pressure in the control pressure line will again increase until the control plunger has reached the illustrated starting position.The exhaust gas recycling valve can then be held in a halfopen position. In this position, and also in the position in which the connecting line 57 is in communication with the annular groove 94, the connecting line 57' is in communication with the second external annular groove 92, so that a downward regulation of the fuel injection rate no longer takes place. In the same manner to the exhaust gas recycling valve, the second actuator apparatus can, in the opposite extreme, be fixed in an intermediate position.

By means of a by-pass line 98, which directly connects the connecting line 57' to the actuating medium feed line 53, and which contains a cut-off valve 99, it is possible to reduce the fuel injection rate to zero.

With the described device it is possible, by suitably forming the characteristic of the compression spring 87 in conjunction with the control pressure to be achieved in the control pressure line 35 and according to the association of the connecting line 57 and 57' and the actuating medium feed line 53 with respect to the position of the control plunger 84, to create set-points from which exhaust gas recycling is possible, or from which reduction in the fuel injection rate is necessary. The described control may also be realised by electrical methods, whereby for example the control pressure is converted into a corresponding electrical variable which is compared by means of comparator apparatuses with corresponding set-points. When the set-points are exceeded or not reached, electromechanical actuating elements are correspondingly controlled. The control variable emitted by the first comparator apparatus may be in the form of an electrical variable with known means, to be described in more detail here. In the embodiment described here, the energy sources already available in internal combustion engines in the form of fuel pressure or vacuum are used in an advantageous manner for carrying out the desired control function. The actuating mechanisms can be very simply constructed and possess high operating reliability.

Claims (11)

1. An apparatus for regulating the air/fuel ratio of the combustion mixture to be introduced into an internal combustion engine, comprising means to provide a first control parameter which is variable in accordance with a difference between the actual fuel flow into the engine and a fuel flow corresponding to the actual air flow, means to provide a second control-parameter in accordance with a difference between the first control parameter and a predetermined parameter, and regulating means actuable in response to the second control parameter to regulate the flow of exhaust gas recycled into the engine.

2. An apparatus as claimed in claim 1, comprising a duct which is provided with a throttle and an outlet, the outlet being communicable with a constant pressure source and being regulable in accordance with a difference between the actual fuel flow into the engine and a fuel flow corresponding to the actual air flow to vary the first control parameter as a control pressure.

3. An apparatus as claimed in either claim 1 or claim 2, comprising means to provide a third control parameter in accordance with a difference between the first control parameter and a further predetermined parameter, and further regulating means actuable in response to the third control parameter to vary the quantity of fuel introduced into the engine.

4. An apparatus as claimed in claim 1, wherein the means for providing the second control parameter comprises an actuating member operable by pressurized fluid to displace against a resilient restoring force an element of a three-way valve to a first position or a second position thereof to cause actuation of the regulating means by the second control parameter in the form of an actuating medium or relieving means respectively.

5. An apparatus as claimed in claim 3, wherein the means for providing the third control parameter comprises an actuating member operable by pressurized fluid to displace against a resilient restoring force an element of a three-way valve to a first position or a second position thereof to cause actua tion of the regulating means by the third control parameter in the form of an actuating medium or relieving means respectively.

6. An apparatus as claimed in either claim 4 or claim 5, wherein the displaceable element comprises a slide valve element.

7. An apparatus as claimed in either claim 4 or claim 5, comprising a duct for the actuating medium and a duct for the relieving means, each duct having a respective aperture formed as a valve seat, the displaceable element being movable from a position between the valve seat, to close either the one or the other of the apertures.

8. An apparatus as claimed in claim 6, wherein the means for providing the second control parameter and the means for providing the third control parameter together comprise an integral double three-way valve, the displaceable element being displaceable against the resilient restoring force by the first control parameter in the form of a control pressure.

9. An apparatus as claimed in any one of claims 4 to 8, wherein the restoring force is provided by spring means having a rate variable in dependence on engine parameters.

1 0. An apparatus as claimed in any one of the preceding claims, wherein the regulating means comprises a valve to regulate the quantity of exhaust gases recycled into the engine.

11. An apparatus substantially as hereinbefore described with reference to and as illustrated by Fig. 1 of the accompanying drawings.

1 2. An apparatus as claimed in claim 11 modified substantially as herinbefore described with reference to and as illustrated by Fig. 2 of the accompanying drawings.

1 3. An apparatus as claimed in claim 11 modified substantially as hereinbefore described with reference to and as illustrated by Fig. 3 of the accompanying drawings.