GB2252849A

GB2252849A - Fault-checking in regulating means for setting elements

Info

Publication number: GB2252849A
Application number: GB9201574A
Authority: GB
Inventors: Ulrich Gerstung; Klaus Bleuel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1991-02-08
Filing date: 1992-01-24
Publication date: 1992-08-19
Anticipated expiration: 2012-01-24
Also published as: GB2252849B; JPH04321745A; GB9201574D0; DE4103839A1

Abstract

Regulating means, particularly for the induction system of an internal combustion engine, comprises a regulating loop with a regulator (2) to which the difference between a target value (Wsoll) and an actual value (Wist) is fed as a regulating magnitude and which drives at least two setting elements (5, 6), each of which covers only a part of the entire regulating range. A monitoring circuit determines the particular regulating range part in which at least one of the target value and the actual value is situated and tests whether the output value (RA) of the regulator (2) is situated in a regulator output value range associated with this regulating range part. The setting elements (5, 6) may be associated respectively with a throttle flap and a turbocharger waste gate. Alternatively, the setting elements (5, 6) may be associated with electromagnetic valves of a fuel injection pump. <IMAGE>

Description

FAULT-CHECKING IN REGULATING MEANS FOR SETTING ELEMENTS 2 2 5) 2 _s; n_

The present invention relates to regulating means for, and to a method for regulating setting ele ments for, for example, influencing induction by an internal combustion engine and has particular reference to fault checking in such regulating means or method.

Equipment for exhaust has return feed in an internal combustion engine is disclosed in DE-05 32 33 290. The engine can be, in particular, a compression-ignition engine, thus a diesel engine.

The equipment includes a valve in a return feed duct, the setting of which is determinable by way of the drive of two electromagnetic valve windings. Also provided is a control device which, starting from operational parameter magnitudes forms a drive signal for the two valve windings. The control device has a proportional -i ntegraldifferential regulation function with limitations, wherein the exhaust gas feed valve is drivable in three-point operation by way of both valve windings.

In regulating loops of this kind, faulty operational states can arise when, for example, one of the setting members is defective and remains in its setting. ' It is then possible that the other setting member will compensate for the faulty setting of the first setting member, so that the fault is not apparent due to the fact that no permanent regulating deviation has arisen. Monitoring to detect a permanent regulation deviation is thusnot sufficient for recognition of faults of that kind.

According to a first aspect of- the present invention there is provided regulating means for setting elements, the regulating means comprising a regulator to provide a regulating signal value in dependence on the difference between a target value and an actual value, a plurality of setting element drives each responsive to the regulating signal value in a respective part of a regulating range, and monitoring means to determine in which part of the regulating range at least one of the target value and the actual value is situated and to ascertain whether the regulating signal value is situated in a range thereof associated with the determined part of the regulating range.

In a preferred embodiment, the regulating means is a circuit arrangement in form of a regulating loop with a regulator to which the difference between the target value and the actual value is fed as regulating magnitude and which drives at least two setting elements, each of which covers only a part of the entire regulating range, wherein the setting elements are connected to a path. The circuit arrangement includes monitoring means which determines the regulating range portion in which the target value and/or the actual value is or are situated and tests whether the output value of the regulator is situated in a regulation output value range associated with this regulating range portion. Each setting element is associated with a particular regulating range part, which means that, for example in the case of two setting elements, one setting element can cover a regulating range part adjoined by a further regulating range part covered by the other setting element, optionally with the interposition of an overlapping zone. Preferably, the setting W elements both operate in such an, overlapping zone, which for preference is very small if indeed it is present at all. If, for example, the regulating loop is in a state associated with the first regulating range part, which means that the first setting element is active, then the output value of the regulator in the fault-free state would if plausible consist of a magnitude lying within a regulator output value range associated with this regulating range part. If this is not the case, the regulating range part concerned does not correspond with the presently valid regulator output value range and thus a fault is present. By this means it is possible to recognise faults which, for example, do not have the consequence of a permanent regulating deviation due to compensation for the function of the faulty setting element by the other faulty setting element.

In a development, it is provided that the monitoring circuit issues a fault report when no plausibility is ascertained between the present regulating range part and the valid regulator output value range in which the output value of the regulator is situated. Preferably, also, it is provided that the fault report is issued only when the fault state is present for longer than a fault time which is presettable for the monitoring circuit. It is thus possible to bridge over transitional states. The fault report is then issued only when no plausible state in the regulating loop arises notwithstanding a presettable weighting time or fault time.

According to a second aspect of the invention there is provided a method of regulating setting elements by way of a regulating loop, comprising the steps of providing a regulating signal value in dependence on the difference between a target value and an actual value, applying the regulating signal value to a plurality of setting element drivers each responsive to the regulating signal value in a respective part of a regulating range, and monitoring the values to determine in which part of the regulating range at least one of the target value and the actual value is situated and to ascertain whether the regulating signal value is situated in a range thereof associated with the determined part of the regulating range.

As in the case of the circuit arrangement, the utilisation of the target value of the actual value is possible for the method, since the target value corresponds t the actual value in the regulated-out state. It is, of course possible to use both the target value and the actual value.

An embodiment of the regulating means and example of the method of the present invention will now be more particularly described with reference to the accompanying drawings, the single figure of which is a block schematic block diagram of a regulating circuit in the form of a regulating loop.

Referring now to the drawing, there is show a circuit arrangement 1 which has the form of a regulating loop and comprises a regulator 2, preferably a proportional-integral regulator. The output value RA of the regulator 2 is fed to a first driving circuit 3 and to a second driving circuit 4. The output vale a, of the circuit 3 is fed to a first setting element 5 and the output value a 2 of the second circuit 4 to a second setting element 6. The output val ue b 1 of the ffrst settingmember 5 is applied to a first input 7, and the output val ue b 2 of the second setting member 6 to a second input 8, of a path 9, at the output 10 of which an actual value W IST is issued. This actual value is fed with a negative sign to a summation point 11, which receives a target value Wsoll with positive sign as further input magnitude. Delivered at the output 12 of the summation point 11 is a regulation difference AW, which is fed as an input magnitude to the regulator 2.

In practice, the circuit arrangement illustrated in the drawing can be a regulating system for an internal combustion engine, preferably a turbocharged diesel engine. For example, regulating loops are used for regulation of start of fuel conveying of the injection pump with two electromagnetic valves in an EDC (electronic diesel control). Such loops are also used for regulation of a charger and of a throttle flap. The regulator in that case always operates on two setting elements, for example one associated with the charger and one associated with normal aspiration. Each setting element in that case covers only a part of the entire regulating range.

In the following description, the regulation of forced induction and atmospheric induction in an internal combustion engine will be referred to by way of example. The regulator 2 in that case controls the setting of the waste gate of a turbocharger andof.athrottle flap in the engine induction duct. The arrangement is such that regulation of the turbocharger waste gate takes place when the induction duct pressure P2 'S greater than the atmospheric pressure P atm and regulation of the' throttle flap takes place when the I induction duct pressure P2 'S smaller,than Patm In the drawing, the waste gate regulation is provided by the first driving circuit 3 and the first setting member 5 and the throttle flap regulation by the second driving circuit 4 and the second setting member 6. The driving circuits 3 and 4 can each have a drive characteristic curve or a drive characteristic field. The waste gate regulation is effective for regulator output values RA greater than a limit value x and the throttle flap regulation is effective for output values RA smaller than a limit value y. The two setting elements 5 and 6 operate in the range between the limit values x and y. The point of inflection of the characteristic curve, which is illustrated in the drawing,of the driving circuits 3 and 4 - is denoted by c. It lies in the region between the limit values x and y.

It is also possible to provide a circuit in which the throttle flap control is in series with the waste gate control.

In the case of only small power demand, the throttle flap is disposed in a more or less closed setting and the turbocharger does not operate. The induction duct pressure P2 is then smaller than the atmospheric. pressure p atm Conversely, in the case of a high power requirement, the throttle flap is opened as far as possible and the turbocharger operates, in which case the induction duct pressure P2 is greater than the atmospheric pressure p atm If, for example, the setting element 5 becomes stuck in a setting in which the turbocharger supplies full charging pressure and if the power demand for the engine is now reduced, then the turbocharger, due to the fault, remains in the state which it supplies full charging pressure; in the fault-free state, of course, the charging pressure would be lowered. However, a throttling of the pressurised charge fed to the engine can take place through resetting of the throttle flap, thus by way of the setting element 6 so that a permanent regulating deviation is not detected even though such is actually present. With a circuit embodying the invention, however this fault state shall nevertheless be found and reported.

In the drawing, the atmospheric pressure p atm corresponds to the inflection point c. The first setting element 5 (waste gate) operates in the value range above the limit value x and the second setting element 6 (throttle flap) operates in the value range below the limit value y. In the circuit exemplifying the invention, the regulator output RA is monito red for plausibility relative to the actual val ue W ist and/or the target value W so]]' A fault is recognised when the output value RA is greater than x and P2 and i s less than p atm or when the output value RA is less than y and P2 is greater than Patm The induction duct pressure P2 can be either the preset induction duct pressure (target value Wsol 1 or the instantaneous induction duct pressure (actual value W ist), Preferably, however, a fault report is issued only when a detected implausible state is present for no longer than a presettable fault time.

Claims

1. Regulating means for setting elements, the regulating means comprising a regulator to provide a regulating signal value in dependence on the difference between a target value and an actual value, a plurality of setting element drivers each responsive to the regulating signal value in a respective part of a regulatidg range, and monitoring means to determine in which part of the regulating range at least one of the target value and the actual value is situated and to ascertain whether the regulating signal value is situated in a range thereof associated with the determined part of the regulating range.

2. Regulating means as claimed in claim 1, the monitoring means being arranged to issue a fault report in the absence of an ascertained plausible correlation of the determined part of the regulating range and the regulating signal value range in which the instantaneous signal value is situated.

3. Regulating means as claimed in claim 2, the monitoring means being arranged to issue a fault report only when the correlation absence has continued for longer than a presettable period of time.

4. Regulating means as claimed in any one of the preceding claims, wherein the setting elements comprise setters influencing induction by an internal combustion engine.

5. Regulating means as claimed in any one of the precedin'g claims and substantially as hereinbefore described with reference to the accompanying drawing.

6. An internal combustion engine equipped with regulating means as 5 claimed in claim 4.

7. An engine as claimed in claim 6, the engine being a turbocharged compression-ignition engine.

8. A method of regulating setting elements by way of a regulating loop, comprising the steps of providing a regulating signal value in dependence on the difference between a target value and an actual value, applying the regulating signal value to a plurality of setting element drivers each responsive to the regulating signal value in a respective part of a regulating range, and monitoring the values to determine in which part of the regulating range at least one of the target value and the actual value is situated and to ascertain whether the regulating signal value is situated in a range thereof associated with the determined part of the regulating range.

9. A method as claimed in claim 8 and substantially as hereinbefore described with reference to the accompanying drawing.