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Title:
DEVICE FOR DETECTING AND CORRECTING FAULTY DISCONFORMITY BETWEEN DESIRED AND ACTUAL POSITIONS OF A SERVO CONTROLLED REGULATING MEMBER
Document Type and Number:
WIPO Patent Application WO/1990/006434
Kind Code:
A1
Abstract:
Device for detecting and correcting faulty disconformity between desired and actual positions of a servo controlled regulating member, particularly a butterfly valve (11) in the intake manifold system (12) of an internal combustion engine in a motor vehicle, has a microcomputer which detects a decrease in an actual position signal from a sensor (14, 15) responsive to the position of the butterfly valve in the absence of a decrease in a desired position signal from a sensor (19, 20) responsive to the position of an accelerator pedal (21), and controls actuating signals to the servo motor (13) in response to such detected decrease to cause the servo motor to move the butterfly valve (11) into the correct position smoothly and gradually whereby to avoid uncalled for increase in engine output following a temporary interruption of operation of the servo motor.

Inventors:
Riehemann, Thomas
Application Number:
PCT/EP1988/001082
Publication Date:
June 14, 1990
Filing Date:
November 29, 1988
Export Citation:
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Assignee:
ROBERT BOSCH GMBH RIEHEMANN, Thomas.
International Classes:
F02D41/22; F02D9/02; F02D11/10; F02D45/00; (IPC1-7): F02D41/22
Foreign References:
EP0121938A1
EP0121937A1
EP0114401B1
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Claims:
CLAIMS
1. Device for detecting and correcting f ulty disconformity between desired and actual positions of a servo controlled regulating member, in particular a butterfly valve in the intake manifold system of an internal combustion engine in a motor vehicle, which butterfly valve is actuated by a servo motor in response to a desired position signal from a sensor responsive to the position of a driver actuated accelerator pedal and an actual position feedback signal from a sensor responsive to the position of the butterfly valve, characterised in that a microcomputer detects a decrease in the actual position signal in the absence of a decrease in the desired position signal and controls actuating signals to the servo motor in response to such detected decrease to cause the servo motor to move the regulating member smoothly arid gradually into the actual position corresponding to the desired position signal.
2. Device according to claim 1, in which both the sensors are potentiometers and provide analog desired and actual position signals respectively, which signals are converted to digital signals in the micropcomputer.
3. Device according to cla'im lor 2, in which the microcomputer also responds to the desired position signal reducing to an engine idling position value without corresponding decrease in the actual position signal, and indicates such condition as a fault condition designated 'regulating member jammed' .
4. Device as claimed in claim 1, 2 or 3, in which the microcomputer also responds to the actual position signal reducing to an engine idling or nominally closed position value whilst the desired position signal increase, and indicates such condition ~as a fault condition designated 'regulating member open' .
Description:
DESCRIPTION DEVICE FOR DETECTING AND CORRECTING FAULTY DISCONFORMITΪ BETWEEN DESIRED AND ACTUAL POSITIONS OF A SERVO CONTROLLED

REGULATING MEMBER

STATE OF THE ART. The present invention concerns a device for detecting and correcting faulty disconformity between desired and actual positions of a servo controlled regulating member particularly a butterfly valve in an internal combustion engine in a motor vehicle in accordance with the precharacterizing clause of claim 1.

In the electric control of an internal combustion engine in a motor vehicle it is common for a butterfly valve in the intake manifold system of the internal combustion engine to be actuated by a servo motor in response to a command signal derived from the position of the accelerator pedal. Potentiometers associated with the accelerator pedal and with the butterfly valve provide respectively a desired value signal and an actual value feedback signal, and actuating signals for the servo motor arise from comparison of these signals. Since for reasons of safety the butterfly valve is resiliently biassed towards its engine idling or nominally " closed position, any interruption in the operation of the servo motorduring normal operation of the internal combustion- engine will result in the butterfly valve moving towards its engine idling or closed position with a consequent reduction in engine output power. When this loss of power is detected by the

driver, the driver's immediate reaction is to depress the accelerator pedal fur-ther. Should the interruption be of only short duration as for example in the case of a loose connection in the electrical circuit of the servo motor, as soon as the servo motor is in operation again it will rapidly advance the butterfly valve to a new position corresponding to the new position of the accelerator pedal and thereby an unnecessary increase in engine output will take place beyond that originally desired by the driver and such uncalled for increase in engine output power could well be a source of danger particularly as the driver may have been taken by s-urprise.

Advantages of the Invention. The device in accordance with the characterising clause of claim 1 overcomes these disadvantages and avoids the attendant risks.

Any interruption in the normal operation of the servo motor during normal operation of the internal ' combustion engine can be detected from the actual value signal decreasing towards a value corresponding to its engine idling or nominally closed position when the desired value signal remains constant or increases, that is to say without any corresponding decrease in the desired value signal. When the servo motor is again in operation it does not move the butterfly valve immediately and rapidly into the position corresponding to the desired value signal, which may of course be greater than the value obtaining prior to the interruption of opera┬▒ion of the- servo motor if the driver has depressed the accelerator pedal further, such as would give rise to a sudden rapid increase in

engine output power, but is moved to such position smoothly and gradually. Should the interruption of operation of the servo motor be of very short duration, for example less than one second, there may have been no immediate response on the part of the driver, but should the duration of the interruption have been longer the driver may well have made an instinctive correction and the gradual and smooth movement of the butterfly valve to its original or to a new position will provide the driver with an opportunity to reverse or correct his previous instinctive action and thereby avoid any dangerous and undesired sudden increase in engine output.

The features of claims 3 and - provide useful detection of faulty operating conditions.

Drawings . The invention will be further described by way of example with reference to the accompanying drawings in which Fig. 1 i ' s a schematic illustration of a device for . detecting and correcting faulty disconformity between desired and actual positions of a servo controlled regulating member according to one embodiment of the invention, Fig. 2 is a graphical illustration of conditions that can arise in the operation of the device of Fig. 1 , and Fig. 3 is a flow diagram illustrating the function of the microcomputer in the device of Fig. 1.

Referring first to Fig. 1, a butterfly valve (11 , ) in the intake manifold system (12) of an internal combustion engine (not illustrated) is actuated by a servo motor (13) and a sensor (1 ) in the form of a potentiomete (15) provides a

feedback signal on line 16 to a microcomputer (17), which also receives on line 18 a desired value signal from a potentiometer (19) which forms a sensor (20) responsive to the position of an accelerator pedal (21). The butterfly valve (11) is resiliently biased into its engine idling or nominally clo'sed position for reasons of safety and constitutes a regulating member actuated by the servo motor (13) in response to command signals derived from depression of the accelerator pedal (21).

In normal operation, when the accelerator pedal is actuated, a desired value signal on line 18 is compared with an actual value signal on line 16 and appropriate actuating signals are sent to the servo motor (13) until the position of the butterfly valve (11) is such that the actual value feedback signal on line 16 corresponds to the desired value signal. Changes in the desired value signal are followed rapidly by movement of the butterfly valve (11) though there will of course be a slight time lag before the butterfly valve (11) actually reaches the desired position. Such normal operation is illustrated graphically by way of example at the left hand side of Fig. 2 in which the horizontal axis represents time and the vertical axis represents desired and actual value signals in voltage. The symbol V^ denotes the desired v ' alue signal whilst the symbol V A denotes the actual value signal. Upon initial depression of the accelerator pedal (21) the desired value signal can rise to VD1 at time T1- and the actual value signal rise to a corresponding value VA1 with a slight time lag. After remaining constant at VD1 until time

T2 the desired value may rise further to VD2 at time T3 , remain constant until time T and then descend to VD3 at time T5 and the actual value signal will follow suit to VA2 at just after time T3. dropping to VA3 at just after time T5. During this normal operation the slight disconformity which may exist at times between the desired value signal VD and the actual value signal VA is of no consequence and is within normal operational tolerance .

If the operation of the servo motor (13) is interrupted, the butterfly valve (11) will move towards its engine idling or nominally closed position. This is illustrated in the centre part of Fig. 2 where it will be observed that the desired value signal is taken for example as remaining constant at VD*. from time T6 to time ' T9 whilst at time T6 the actual value signal VA is at VA . but at time T7 the operation of the servo motor (13) is interrupted and as the butterfly (11 ) moves towards its engine idling or nominally closed position the actual value signal decreases and reaches the value VA5 at time T8. If it is assumed that at this time T8 the operation of the servo motor (13) s restored under normal operating conditions the servo motor (13) would immediately and rapidly move the butterfly valve (11) on to a position such that the actual value signal would be increased rapidly back to VA and this would have the effect of producing a sudden increase in engine output following a relatively slow decrease in engine output; moreover if such decrease in engine

output were detected by the driver his immediate instinctive reaction would have been to have depressed the accelerator pedal further and these conditions would have given rise to a rapid surge of engine output to a value higher than desired by the driver. The device of the present invention avoids this difficulty since the microcomputer (17) operates in such a way that the actuating signals to the servo motor (13) are only such as to move the butterfly valve into the relevant position smoothly and gradually at time T9 as indicated graphically in Fig. 2.

Malfunctioning of the butterfly valve (11) under the control of the servo motor (13) may well take the form of the actual value signal and desired value signals moving in opposite directions for example the driver might depress the accelerator pedal to produce an increasing desired value signal whilst the butterfly valve moved in the opposite direction and produced a decreasing actual position signal. This can also be detected and is illustrated at the right hand side in Fig. 2. At time T10 the desired value signal VD increases from VD4 to VD5 at time T11 whilst the actual value signal VA decreases from VA4 at time T10 to a lower value at T11 as a result, it is assumed, of interruption of operation of the servo motor (13) which becomes operative once more at time T11. Then the servo motor (13) does not immediately and rapidly move the butterfly valve (11) into the position corresponding to the desired value signal VD5 but does so smoothly and gradually such that the

actual value signal VA reaches the corresponding value VA5 at time T12.

The manner in which the microcomputer (17) operates can be described with reference to the flow chart of Fig. 3- The * desired value and actual value signals are converted from analogue to digital form at (21) for further processing and the digital signals VA and VD are compared at (22). If, within a time window dependent upon the regulating time of the servo motor (13) and the butterfly valve (11), they coincide then the error bits corresponding to the fault butterfly valve jammed and butterfly valve open are erased at (23), though it will be appreciated that in normal operating conditions these error bits will not have been set, and the main program continues normally. If, however, the values do not coincide an interrogation is performed at ( 2 -\ ) as to whether the desired and actual values are changing in opposite directions. If this should be the case the subprogram for fault assignment is commenced and an interrogation is performed at (25) to determine whether the desired value VD is decreasing towards the engine idling or no load position and the butterfly valve, and thereby the actual value signal VA, cannot follow, or whether the butterfly valve is moving towards the engine idling or nominally closed position, and thereby the actual value signal VA is decreasing towards its corresponding ' value , though the desired value signal VD is remaining constan or is increasing. In the former case it will be apparent that the'"^_

butterfly valve has jammed in the reversed direction and the corresponding error bit is set at (26) whereas in the latter case it will be apparent that there is an interruption in the operation of the servo motor (13) and this fault is indicated, by the setting of the error bit designated butterfly valve open at (27). Referring back to (24), if the desired and actual values are not moving in opposite directions there can be two reasons for this; firstly they are moving in the same direction but the actual value signal has not yet caught up with the desired value signal owing to the regulating time of the servo motor and butterfly valve; or secondly in the case of an interruption in the operation of the servo motor (13) and butterfly valve (11) , the butterfly valve has already reached its engine idling or nominally closed position. This second condition can be detected since in the event of an interruption of operation of the servo motor for the team the error bit designated butterfly valve open will have been set at (27). This is interrogated at (29) and if set the servo motor (13) is actuated at (30) such as to bring the actual value signal VA up to the value of the desired value signal of VD provided that the interruption in the operation of the servo motor (13) has terminated and that operation has been restored.