GB2252177A

GB2252177A - Fault checking in an engine control regulating system

Info

Publication number: GB2252177A
Application number: GB9124862A
Authority: GB
Inventors: Wolf Wessel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1990-12-01
Filing date: 1991-11-22
Publication date: 1992-07-29
Anticipated expiration: 2011-11-22
Also published as: FR2669964B1; FR2669964A1; JPH04269354A; DE4038337C2; GB9124862D0; JP3415858B2; GB2252177B; DE4038337A1

Description

1 1 2252177 FAULT CHECKING IN AN ENGINE CONTROL OR REGULATING SYSTEM The

present invention relates to a system for control and/or regulation of an internal combustion engine.

In DE-OS 36 21 937 there is disclosed a system for the control and/or regulation of an internal combustion engine which comprises at least one measuring device for the detection of an operating parameter of the engine and/or of a vehicle equipped with the engine, in dependence on which the engine is controlled and/or regulated. This parameter can be the setting of a performance-determining element and/or of an operating element actuable by the vehicle driver. Recognition of faulty functioning of the measuring device takes place by comparison of delivered signal values, which represent the parameter, with preset limit values.

Difficulties arise if the sensor used for the detection of the parameter has in its signal range a part range characterised by impaired or incomplete signal transmission or generation. Such problems arise as a result of, for example, contamination. In the case of potentiometers, regions with poor conductivity may form on the resistance track in sections of its range of movement as a consequence of wear. This is particularly the case at the points of reversal. Such contamination leads to a large transfer resistance between the resistance track and the wiper pick-up and thus to a false parameter signal value. In known monitoring systems this will cause a fault report and lead to the failure of the system equipped with the measuring device.

Monitoring equipment for an electronically controlled throttle flap in a motor vehicle is disclosed in DE-OS 35 10 173, wherein a measuring device,. which in one of the examples consists of a setting transmitter potentiometer and a monitoring potentiometer, is connected with the accelerator pedal. The signal value supplied by the setting transmitter potentiometer is compared in a logic unit with the values ascertained from the signal of the monitoring potentiometer. The function of the equipment is checked by reference to the signal magnitude of the setting transmitter potentiometer through comparison with the signal values of the monitoring potentiometer. disadvantages.

There is thus a need for a system which may ensure operational reliability but with improved availability of the system.

According to the present invention there is provided a system for at least one of control and regulation of an internal combustion engine in dependence on signal values indicative of an operating parameter of the engine or of a vehicle equipped with the engine, the system including detecting means for detecting the parameter and providing the signal values and means for checking the signal values for faulty functioning of the detecting means, wherein no checking is carried out in at least one predetermined range of the values.

An advantage of a system embodying the invention is to be seen in the use of a checking method which performs no checking in partial ranges. These partial ranges may be characterised by an impaired and/or incomplete signal transmission or signal generation, for example due to a transfer resistance, which may be increased as a result of abrasion, between a resistance track and an associated wiper pick-up. It is thereby made possible to recognise actual faulty functioning of the detecting means Thi s procedure also exhibits the afore-mentioned 1 while avoiding unnecessary switching-off of the entire system due to incorrect identification of faulty functioning.

An embodiment of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a block schematic diagram of an electronic Diesel regulating system; Fig. 2 is a diagram showing fault checking and non-checking ranges of signals provided by sensors in the system; and Fig. 3 is a flow diagram illustrating steps in checking of such signals to detect faulty functioning of the sensors.

Referring now to the drawing there is shown in Fig. 1 a regulating system for an internal combustion engine (not shown) of a vehicle, the engine installation including a performance setting element 10, for example a regulating rod for control of the quantity of fuel fed to the engine or a throttle f",ap for influencing air feed to the engine. An operating element actuable by the vehicle driver, namely an accelerator pedal, is denoted by 20 and is mechanically connected with sensors 30 and 40. The sensors 30 and 40 supply signals to measuring equipment 50 for the respective operating parameters. The equipment 50 is part of a control unit 100, which is preferably constructed as a computer. It can, however, also be realised by means of discrete circuits.

The control unit 100 also receives signals from a sensor 70, which indicates the position of the element 10. The sensor 70 can, with advantage, be designed as a double sensor similar to the sensors 30 and 40. In this case, measuring equipment 55, which is constructed in correspondence with the equipment 50, detects the relevant operating parameter. Further sensors 80 (only one of which is shown) detect operating magnitudes, for example engine speed. In dependence on the signal values representing the operating parameters of the engine and/or of the motor vehicle, as well as the signal values of the further sensors 80, the control unit 100 computes signals for the control and/or regulation of the engine. These serve for, in particular, influencing the element 10.

The sensors 30 and 40 detect, as already mentioned, the setting of the associated element 20. In a particularly simple embodiment, the sensor 30 is a potentiometer and the sensor 40 a switch. Two different signals states are present at the output of this switch in dependence on the setting of the element. Thus, the switch can be arranged so that it is closed when the engine is idling and open when the engine is at full load. In this case, a high voltage is present at the output of the sensor 40 in idling and a low voltage outside idling. It is, however, equally possible for the switch to be arranged so that a low voltage is present at the output of the sensor 40 in idling and a high voltage outside idling.

In a further embodiment, both sensors 30 and 40 are constructed as potentiometers, preferably as double potentiometers. In this case, the mechanical connection is coupled with the movable wiper taps of the potentiometer and the signal value is picked up at the wiper taps.

The mechanical connection of the sensors has the effect that a change in setting of the associated element 20 leads to a corresponding change in the signal value of both sensors so that each sensor on its own generates a signal value representing the setting of the element 20. This is the c case in particular when both sensors are constructed as potentiometers.

Similarly, the sensor 70 which indicates the setting of the setting element 10 is usually constructed as a potentiometer or as a double potentiometer with two conductor tracks.

The operation of the system according to Fig 1 is as follows. The measuring equipment 50 supplies signal values, which indicate the setting of the operating element 20, to the control unit 10. If the unit 100 is a computer, the analog signals of the sensors 30 and 40 are converted by way of analog-to-digital converters into digital values which the computer 100 then processes.

The computer computes a setting signal for the element 10 in dependence on the signal value indicative of the setting of the element 20 and possibly on further signal values, such as an engine speed signal value. The computation takes place in dependence on the output signal of the sensor 30 and the sensor 40 serves merely for functional monitoring of the sensor 30.

However, it is also possible that a mean value or a minimum value of the signal magnitudes generated by the sensors 30 and 40 is used for regulation of the setting of the element 10. In that case, at least one of the signal values of one of the sensors serves for the monitoring of the function of the other sensor or sensors. If the sensor 40 is realised as switch, then this sensor serves predominantly for generation of a signal which indicates idling. Moreover, the functional capability of the two sensors 30 and 40 can be checked by comparison of the two output signals. The same is also true for the sensor 70.

Apart from the functions of the control unit 100 as described above, further functions are normally performed by this, for example determination of injection instant, ignition instant, metering and/or idling regulation.

Fig 2 illustrates signal value characteristics of the sensors 30 and 40 discussed with reference to Fig. 1. The solid line shows the output signal UPWG of the sensor 30, exemplified in the following as a potentiometer, in dependence on the angular setting WFP of the accelerator pedal. The output signal of the sensor 40, exemplified in the following as an idling switch, is illustrated in chain-dotted lines. The idling switch is closed below an angle W1 and opened above an angle W2.

This is one possible form of operation of the switch. It is, however, also feasible for the switch to be open below the angle W1 and closed above the angle W2. The switching state of the switch i s not defined in the region between the angle W1 and the angle W2, which means that the switch can assume other either state in this angular region. The switch setting in that case depends on whenever the switch was previously closed or previously open.

Six value ranges for the output signal UPWG of the. potentiometer can be distinguished. The value range 1 denotes a voltage which does not arise in normal operation. The value range 2 indicates a voltage range in which the signal transmission or the signal detection can be faulty and corresponds to a range which results when the potentiometer is disposed in the proximity of its lower point of reversal. The value range 3 characterises a range in which the isling switch is usually closed. The value range 4 again indicates a range in which the switch position of the switch is not defined. The switch is usually open in the value range 5.

1 The value range 6 is the range in which the signal transmission or the signal detection can be faulty because the potentiometer is disposed in the proximity of its second point of reversal.

The known forms of fault checking equipment recognise merely whether the output signal is in the range 1, 2 or 3 and the idling switch is closed at the same time or whether the accelerator pedal value transmitter is in the range 5 and the idling switch is open. In such systems, the case can arise that the signal detection is faulty particularly for small or large angles. This leads to the conductor track being interrupted for large or small angles of the accelerator pedal value transmitter, and a very small voltage, which is in the value range 1, is present at the output of the sensor.

Faults are usually recognised if the output signal of the sensor 30 is in the value range 1. This has the consequence that an emergency operation is initiated. Since contaminations frequently occur at very large and very small angles of the potentiometer after an extended period of use of the engine, this case is quite common and has the consequence that there is increasing recognition of fault states even though no fault is actually present.

In addition, a plausibility interrogation between the setting of the idling switch and the output signal of the acceleration pedal value transmitter takes place in the known system. For large angles of the transmitter, the idling switch must be open. For small angles, which means small output signals, the idling switch must be closed. This means that the idling switch must be closed in the ranges 2 and 3 and open in the ranges 5 and 6. In the range 4, the switch can assume either setting.

A The range 1 is excluded, since the output signal of the pedal value transmitter cannot assume this range.

If a plausibility interrogation takes place when the pedal value transmitter is in the range 7 and an interruption in the conductor track occurs in this case, then the switch is opened and the output signal of the transmitter indicates a low voltage. Implausibility, thus a fault, would be recognised in this case. In fact, no fault is present, since the idling switch is open and the pedal value transmitter has a large angle. An emergency travel operation would be intiated although no fault is present.

A similary problem arises if a further potentiometer is used in place of the idling switch and has a similary output characteristic to the idling switch. Such a potentiometer has a high voltage for small angles and a low voltage for large angles in correspondence with the output signal of the switch, as shown in chain-dotted lines in Fig 2.

If deposits ari,e in the course of operation with such a potentiometer, then a small voltage is present at the output of the second potentiometer, although a large voltage ought to be present according to its setting. If a plausibility interrogation is performed, a fault is recognised even though the pedal value transmitter is fully capable of function. An emergency travel operation is not necessary in this case. In the known systems, emergency cases thus arise very frequently, although critical operational states are not actually present. This leads to an increased failure rate of the system.

In order to avoid thus, the procedure illustrated in Fig 3 is followed. The setting of the potentiometer is detected in a first step -Q 300. An interrogating unit 310 recognises in which range the output signal is disposed. If the output signal of the potentiometer has a value which lies in the range 1, 2, 4 or 7, no fault checking takes place and the testing programme ends at unit 340. If, on the other hand, the interrogating unit 310 recognises that the output signal of the potentiometer is in one of the ranges 3, 5 or 6, then a fault checking takes place in the interrogating unit 320.

A particularly simple embodiment provides that the interrogating unit 310 checks merely whether the output signal of the potentiometer is disposed by a certain threshold belows its maximum value or by a certain threshold above its minimum value. This means that the potentiometer is situated in the proximity of one of its points of reversal. If this is the case, no fault checking takes place. The threshold usually lies at 10% of the maximum value of the output signal.

This occurs particularly advantageously if a plausibility test of the output signal for the potentiometer 30 with the output signal of the idling switch 40 is performed. If the interrogating unit 320 recognises that the output signal of the potentiometer is implausible relative to that of the idling switch, a fault report is delivered at unit 330. Thi s fault report can initiate an indication which informs the driver about the fault that has arisen. It can, however, provide for emergency vehicle travel operation to be initiated at once. It is particularly advantageous if both measures are to be performed. If no fault state is recognised, the subprogramme ends at the unit 340.

The described system is not restricted to monitoring of the accelerator pedal value transmitter. The described method is applicable to all types of equipment for the detection of an operational characteristic magnitude, in which, for example, two sensors test each other for faults that are present. In particular, it is also applicable to the sensor 70 which indicates a setting of the performance-determining element.

Claims

1. A system for at least one of control and regulation of an internal combustion engine in dependence on signal values indicative of an operating parameter of the engine or of a vehicle equipped with the engine, the system including detecting means for detecting the parameter and providing the signal values and means for checking the signal values for faulty functioning of the detecting means, wherein no checking is carried out in at least one predetermined range of the values.

2. A system as claimed in claim 1, wherein the parameter represents at least one of the setting of a setting element influencing engine output and the setting of a driveractuable control element for the engine.

3. A system as claimed in claim 1 or claim 2, wherein the system is arranged to form the signals into the ranges and the means for checking is operable to carry out checking in one range and no checking in the other range.

4. A system as claimed in any one of the preceding claims, wherein the detecting means comprises at least one of a sensor and a switch.

5. A system as claimed in claim 4, wherein the detecting means comprises a sensor, the sensor being a potentiometer j

6. A system as cl aimed in claim 5, wherein a respective such predetermined range is associated with the region of each point of reversal of the potentiometer.

7. A system as claimed in claim 5, wherein no fault checking is carried out when the potentiometer is disposed in the proximity of its points of reversal.

8. A system as claimed in any one of the preceding claims, wherein the or at least one such predetermined range is determined by incomplete or impaired detection of the parameter by the detecting means.

9. A system as claimed in any one of claims 1 to 7, wherein the or at least one such predetermined range is determined by incomplete or impaired signal transmission by the detecting means.

10. A system substantially as hereinbefore described with reference to the accompanying drawings.

11. An internal combustion engine equipped with a system as claimed in any one of the preceding claims.

1 Q