GB2160337A

GB2160337A - Method of determining whether or not a throttle mechanism of an internal combustion engine is bearing against a throttle valve actuator

Info

Publication number: GB2160337A
Application number: GB08514393A
Authority: GB
Inventors: Wolfgang Misch; Adolf Freytag
Original assignee: Pierburg GmbH; Robert Bosch GmbH
Current assignee: Pierburg GmbH; Robert Bosch GmbH
Priority date: 1984-06-13
Filing date: 1985-06-07
Publication date: 1985-12-18
Also published as: IT1182756B; FR2566048A1; MY8700339A; IT8548199A0; GB8514393D0; DE3421897A1; GB2160337B

Abstract

A method of determining whether or not a main throttle mechanism of an internal combustion engine is bearing against an electro-pneumatic or electric motor-driven throttle valve actuator which acts as a stop on the mechanism in the throttle closing direction, comprises carrying out test operations at specific time intervals by loading the throttle valve actuator with control signal pulses S2, directed in the opening direction of the main throttle valve mechanism, which pulses lead to an adjustment of the position of a stop rod 5 of the actuator only when the throttle valve mechanism is not bearing against the actuator, whereas when the throttle valve mechanism 7 is bearing against the rod 5 of the actuator no position adjustment takes place. The reaction of the actuator to each such signal is sensed and is evaluated as an indication of whether or not there is bearing. Suitable threshold values of the signals and reaction may be provided, and if necessary these can be made adjustable as a function of operating parameters of the engine or external operating parameters. <IMAGE>

Description

SPECIFICATION Method of determining whether or not a throttle mechanism of an internal combustion engine is bearing against a throttle valve actuator This invention relates to a method of determining whether or not a main throttle mechanism of an internal combustion engine, the mechanism being biassed by a spring in a throttle closure direction, is bearing against a throttle valve actuator which acts as a stop in the mechanism in the closure direction and which has a stop position which is adjustable by control signals as a function of operating parameters.

It is known, in order to establish whether the main throttle mechanism is in an idling position in which it bears against the throttle valve actuator, to provide an electromechanical contact indicator at a plunger of the actuator which plunger comes into engagement with the main throttle mechanism. Such a contact indicator or switch is highly subject to error, since it is subjected to large forces and frequently is attacked by the atmosphere existing at its location.

The object of the present invention therefore is to provide a method as initially described in which a contact indicator or switch in the engagement region between the main throttle mechanism and throttle valve actuator can be dispensed with.

To this end, according to this invention, in a method as initially described, the bearing or lack of bearing is interrogated by test operations in which the throttle valve actuator is subjected to control signal pulses which tend to adjust the actuator to move the stop position in the opening direction of the main throttle mechanism, which pulses lead to an adjustment of the stop position when the throttle valve mechanism is not bearing against the actuator and, when the throttle mechanism is bearing against the actuator do not cause any position adjustment of the throttle valve actuator, and the reaction of the actuator in both cases is evaluated to provide an indication of whether or not there is bearing of the throttle mechanism against the actuator.

In the idling condition, that is with the accelerator pedal of the throttle mechanism released, the throttle valve mechanism bears against the throttle valve actuator, whereas at part load or full load of the engine, that is with the pedal depressed, the mechanism is moved away from the throttle valve actuator.

Thus, in the idling condition, when a stop position adjustment occurs of the throttle valve actuator in the opening direction of the throttle valve mechanism, fairly large resistances must be overcome. The invention is thus based on the idea of evaluating differences in these resistances by the said method, so that a definite indication whether or not there is bearing at any instant can be provided. As soon as a stop position adjustment occurs as a reaction of the actuator when the control signal pulses are applied, this means that the throttle valve mechanism has moved away from the throttle valve actuator, whereas if there is no stop position adjustment, the idling condition is present. This method is extremely simple, since it requires only a suitable pulse loading of components which may already be present and an evaluation of the reaction of the actuator to these pulses.

According to a further feature of the invention, it is preferred, in conjunction with an electro-pneumatic diaphragm box throttle valve actuator, which is subject to spring bias in the throttle opening direction, and having a vacuum chamber and a variable-volume working pressure chamber and a vent valve and vacuum valve connected thereto, to open and close the vent valve and vacuum valve alternately by control signal pulses such that, on the basis thereof, the movement-pressure hysteresis of the system is reliably bridged in the case where the throttle valve mechanism is not bearing against the actuator with the result that there is a stop position adjustment and is reliably not bridged in the case where there is bearing of the throttle valve mechanism so that there is no stop position adjustment.The system as a whole, which is effective when the throttle valve mechanism is bearing against the throttle valve actuator, has a larger movement-pressure hysteresis than the throttle valve actuator which alone is effective at part or full load of the engine when the throttle mechanism is not bearing against the actuator. Consequently, the system as a whole during idling requires, for achieving stop position adjustments, larger pressure fluctuations than the throttle valve actuator requires during part or full load operation. Thus the bearing condition can be established in a simple manner by sensing pressure fluctuations in the throttle valve actuator.

When an electro-pneumatic throttle valve actuator of this type includes as is known, a position feedback indicator, it is furthermore preferred to determine the system reaction at this indicator. preferably, a threshold value is provided for the stop position adjustment. In this way, the position feedback indicator, which is in any case provided for control, regulation or indication purposes, can also be used for determining the test-dependent system reaction. By inputting a suitable threshold value it is possible, for example, to differentiate between a position adjustment to be determined and error signals due to vibrations.

When an electric motor-driven throttle valve actuator is used, it is preferred to determine the system reaction by evaluating the motor starting or operating current and/or the voltage across the motor, and/or the time elapsing between the start of the control signal pulses and the start of the stop position adjustment. On account of the larger mechanical resistance when the throttle valve mechanism is bearing against the actuator, there is a larger starting current for the electric motor than when the throttle valve mechanism is not bearing against the actuator during part or full load operation of the engine. Furthermore, there is a larger time delay to the start of the stop position adjustment in this operating condition. These differences can also easily be determined and utilized for ascertaining whether or not the throttle mechanism is bearing against the actuator.When an electric motor-driven throttle valve actuator is used having a stop position indicator associated with the main throttle mechanism, such as a potentiometer on the main throttle, it is preferred to determine the time delay by evaluating signals from the position indicator. This indicator can thus be used simultaneously for several purposes and no separate means are reqired for determining the stop position adjustment.

A further preferred feature of the invention consists in that threshold values are provided for the starting or operating current and/or the motor voltage and/or the time delay. As a consequence it is possible, as a function of any influencing variables, to distinguish cclearly between the operating states when the throttle valve mechanism is and is not bearing against the actuator.

According to a further feature, it is preferred to make the length and/or magnitude of the control signal pulses and/or the threshold values dependent upon external influencing variables, such as temperature and operating voltage. This makes possible an adaptive readjustment and adaptation according to demand in dependence upon variable external influencing values. For example, it will be advantageous, in the case of an increase in operating voltage in conjunction with an electric motor-driven throttle valve actuator, to reduce the length and/or magnitude of the control signal pulses and/or to increase the current threshold value. Opposite conditions obtain in the case of a temperature increase.

Instead, or additionally, it is also possible for the length and/or magnitude of the control signal pulses and/or the threshold values to be made dependent upon the operating state of the throttle valve actuator at any instant. It is thereby, for example, possible to provide a change in the relevant variables as a function of the deflection of the throttle valve actuator at any instant, in order thereby to compensate dependencies inherent in the system, such as a dependence of the movementpressure hysteresis of an electro-pneumatic throttle valve actuator upon its deflection which in turn depends on the stop position.

To ensure trouble-free operation, it may furthermore be advantageous, before commissioning and also repeatedly, for the length and/or the magnitude of the control signal pulses and/or the threshold values to be reduced, in calibration, from larger values in such a way that when the throttle valve mechanism is bearing against the actuator, a system reaction just fails to occur.

An especially favourable feature of the invention consists in that, only when a system reaction consequent upon a movement of the main throttle mechanism in fhe opening direction on the basis of the control signal pulses, is a control signal pulse application compensating this movement then effected. The compensating pulse application thus takes place only if a stop position adjustment has previously occurred, which is the case for part or full load engine operating conditions with the throttle valve mechanism not bearing against the actuator.When, by contrast, in the idling state on account of the greater mechanical loading on the actuator no position adjustment takes place, the compensating control signal pulse application should be omitted, in order that the throttle valve actuator shall not be moved back step by step in the closure direction of the throttle valve mechanism every time a test operation takes place.

Also the test operations are preferably repeated at specific time intervals, such as at 20 millisecond intervals. This provides assurance that an indication about the bearing condition is virtually continuously provided and that simultaneously a continuous readiness for operation of the throttle valve actuator for possible adjustment operations exists.

Some examples of methods in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a diagrammatic overall view of an electro-pneumatic throttle valve actuator and a throttle valve mechanism associated therewith, the operational effect of which on the throttle valve actuator is to be determined by the method of this invention; Figure 2 is a block diagram showing the principle of signal processing in the system of Figure 1; Figure 3 is a diagrammatic overall view of an electric motor-driven throttle valve actuator and a throttle valve mechanism, the operational effect of which on the throttle valve actuator is to be ascertained by the method of this invention; and Figure 4 is a diagram showing the principle of the motor control and signal processing in the apparatus of Figure 3.

According to Figure 1, an electro-pneumatic throttle valve actuator 1 is constructed in the form of a diaphragm box and has a movable diaphragm 2, which separates a chamber 3, which is vented to atmosphere via an opening B, from a working pressure chamber 4. The diaphragm 2 has an outwardly guided diaphragm rod 5, which is biassed by a compression spring 6 in a direction to increase the volume of the working pressure chamber 4. A throttle valve mechanism 7 has an accelerator pedal linkage, not further referenced, and is biassed by a tension spring 8 in a direction which causes it to press against the diaphragm rod 5.

The throttle valve actuator 1 has a solenoid valve 9, controllable by means of a first electrical signal S1, and a solenoid valve 10, controllable by a second electrical signal S2.

The two solenoid valves lead into the working pressure chamber and are subject, at their inlet sides, to vacuum Pu and atmospheric pressure PA respectively. A plunger 11, which follows the diaphragm movement, carries at one end a slider-like pick-up 12, which make contact with an energized resistor (potentiometer) 1 3 with a slide track 1 4 at a position dependent upon the actual position of the diaphragm 2. From the slide track 14, a third electrical signal S3, dependent upon the actual position of the diaphragm 2, is obtained.

According to Figure 2, the signals S1 and S2 are generated by a control circuit 15, to which on the input side at least one control signal B1 for the individual adjustment operations, at each test operation at least one interrogation signal B2 and, optionally also, further operating parameter signals B3 are supplied. It then depends upon the input signals whether the signals S1 or S2 are generated with a length of time appropriate for a desired adjustment operation of the actuator or as short signal pulses singly or alternately for test operations.The third or actual position signal S3 is supplied to an evaluating circuit 16, in order to establish therefrom the lack or presence of a system reaction and to generate or not to generate at the output side a fourth signal S4, which indicates whether or not the throttle valve mechanism is bearing on the rod 5 of the throttle valve actuator. The evaluator circuit 1 6 may have a signal threshold value for the position adjustment, which moreover may be adaptively readjusted by operating parameters of the engine and/or external influences.

The example of Figure 3 includes an electric motor-driven throttle valve actuator, upon which the already mentioned throttle valve mechanism 7 can act. The throttle valve actuator has an electric motor 17, which is connected by a pinion and rack 1 9 to a throttle valve stop 18, which is linearly movable in guides 20.

As shown in Figure 3 the throttle valve mechanism 7 is conected via a drive link 22 to a crank pin 23 of a pivotal main throttle valve 21, indicated in outline. If the throttle valve linkage 7 is actuated by means of the accelerator pedal, a corresponding opening or closing of the main throttle 21 valve thus takes place. There may be associated with this main throttle valve a throttle valve potentiometer 24, from which a signal S8 indicating the position of the main throttle valve is derived According to Figure 4, the electric motor 7 is energized via its terminals a, b and a current determining element 25 from a battery 26, the current supply being via a switching assembly 27, 28 in the one path of flow of the current in one direction and via a switching assembly 29, 30 in another path of flow in the opposite direction.The two switching assemblies are controlled by signals S5, S6 respectively, which in principle have the same effect as the signals S1, S2 respectively in Figures 1 and 2 and, according to Figure 4, are generated by a control circuit 31, corresponding to the control circuit 1 5 of Figure 1, as a function of the already named input signals. A signal S7 obtained from the current determining element 25 and/or the signal S8 from Figure 3 are supplied to an evaluator circuit 32, corresponding to the evaluator circuit 16, from which a signal S9, corresponding to the signal S4 of Figure 2, is generated if the throttle valve mechanism 7 is bearing against the rod 18.

A standard adjustment of the electric motordriven throttle valve actuator 1 8 can be carried out by the signal S5 or S6 respectively being generated for the required length of time, in order that the electric motor 1 7 can rotate sufficiently far in one direction or the other. If, by contrast, a test operation for the bearing condition is necessary, the electric motor 1 7 only needs to be loaded with short control signal pulses to cause it to rotate in a direction to open the throttle valve mechanism 7 (or in alternate directions), in order to establish by sensing the signal S7 and/or the signal S8 the reaction of the system.In the case of signal S7. it is assumed that the starting or operating current of the electric motor when the throttle valve mechanism 7 is in contact with the rod 1 8 is greater than at part or full load. In the case of signal S8, it is assumed that the time delay to the start of a position adjustment of the main throttle 21 is greater, when the throttle valve mechanism 7 is in contact, than at part or full load. Instead of signal S7, the motor voltage at the electric motor 1 7 can. if desired, be measured.

In the apparatus according to Figure 3 it is also possible to provide in the evaluator circuit 32 suitable threshold values and adaptively to readjust these if necessary as a function of operating parameters or external influencing variables.

If no throttle valve potentiometer 24 is present. either a purely electrical evaluation can be carried out or the system reaction at the throttle valve actuator itself must be determined, for example by means of a position potentiometer provided there.

The embodiment illustrated and described represent only examples for such systems, with which the method of this invention can be carried out. In this connection it is always assumed as a starting point that test operations are carried out repeatedly by means of single control signal pulses and that conclusions are drawn from the particular system reaction about the effect of the throttle valve mechanism against the throttle valve actuator that is whether or not it is bearing against the actuator rod.

Claims

1. A method of determining whether or not a main throttle mechanism of an internal engine, the mechanism being biassed by a spring in a throttle closure direction, is bearing against a throttle valve actuator which acts as a stop on the mechanism in the closure direction, the stop position of the actuator being adjustable by control signals as a function of operating parameters, wherein the bearing or lack of bearing is interrogated by test operations in which the throttle valve actuator is subjected to control signal pulses which tend to adjust the actuator to move the stop position in the opening direction of the main throttle mechanism, which pulses lead to an adjustment of the stop position when the throttle valve mechanism is not bearing against the actuator and, when the throttle mechanism is bearing against the actuator do not cause any position adjustment of the throttle valve actuator, and the reaction of the actuator in both cases is evaluated to provide an indication of whether or not there is bearing of the throttle mechanism against the actuator.

2. A method according to Claim 1, in which the actuator is of the electro-pneumatic diaphragm type and is subject to spring bias of its stop position in the throttle opening direction, the actuator having a variable-volume working suction chamber and having atmospheric venting and vacuum valves connected thereto, wherein the venting and vacuum valves are alternately opened and closed by control signal pulses such that, on the basis thereof, the movement-pressure hysteresis of the actuator, when the throttle valve mechanism is not bearing against it is bridged with the result that there is a stop position adjustment and when the throttle valve mechanism is bearing against the actuator, it is not bridged and there is no stop position adjustment, but only an indication that there is bearing of the throttle mechanism.

3. A method according to Claim 2 in which the actuator is electro-pneumatic with a position feedback indicator, wherein the reaction of the actuator upon the application of a control signal pulse is detected at the position feedback indicator.

4. A method according to Claim 2 or Claim 3, in which a threshold value is provided for the stop position adjustment.

5. A method according to Claim 1, in which the actuator is electric motor-driven, wherein the reaction of the actuator is determined by evaluating the motor starting or operating current and/or the voltage across the motor and/or the time delay elapsing between the start of the control signal pulses and the start of the adjustment of the stop position.

6. A method according to Claim 5, in which the throttle valve actuator has a position indicator associated with the main throttle mechanism, e.g. a potentiometer on the main throttle, wherein the time delay is determined by evaluating the signals from the position indicator.

7. A method according to Claim 5, in which threshold values for the motor starting or operating current and/or the motor voltage and/or the time delay are provided.

8. A method according to any one of Claims 1 to 7, in which the length and/or magnitude of the control signal pulses and/or the threshold values are made dependent upon external influencing variables, such as temperature and operating voltage.

9. A method according to any one of Claims 1 to 8, in which the length and/or magnitude of the control signal pulses and/or the threshold values are made dependent upon the current operating state of the throttle valve actuator.

10. A method according to any one of Claims 1 to 9, in which calibration of the reaction of the actuator, the length and/or the magnitude of the control signal pulses and/or the threshold values are reduced, starting from larger values, in such a way that, when the throttle valve mechanism is bearing against the actuator, the reaction of the actuator is such that movement of the stop position just fails to take place.

11. A method according to any one of Claims 1 to 10, in which only when, on the basis of the control signal pulses, a reaction of the actuator to move the stop position occurs in the opening direction of the main throttle, a control signal pulse application is then effected compensating this movement.

1 2. A method according to any one of Claims 1 to 11, in which the testing operations are repeated at specific time intervals.

1 3. A method according to Claim 12, in which the time intervals are 20 milliseconds.

14. A method according to Claim 1, substantially as described with reference to Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings.