GB2213961A

GB2213961A - Adjusting position-report signal

Info

Publication number: GB2213961A
Application number: GB8827620A
Authority: GB
Inventors: Manfred Henning
Original assignee: Pierburg GmbH
Current assignee: Pierburg GmbH
Priority date: 1987-12-16
Filing date: 1988-11-25
Publication date: 1989-08-23
Anticipated expiration: 2008-11-25
Also published as: DE3742592A1; FR2624967A1; IT8848567A0; IT1224570B; ES2010846A6; GB8827620D0; GB2213961B; DE3742592C2; FR2624967B1

Description

11 1 A PROCESS FOR ADJUSTING A REPORTED-BACK SIGNAL REPRESENTING THE

POSITION OF A DEVIC 12- 2 13 9 6 1 The invention relates to a process for adjusting, by means of a signal- processor, a reported-back signal representing the position of a controller whose position is determined by a positioner.

A device for performing a process of this kind is already known from the publication by the firm Fa. Bosch: "Technische Unterrichtung - Motor Elektronik" (Technical Information - Engine Electronics) VDI - V, 1/1 DE (7.83), page 33. The device described there is a carburettor whose throttle valve (the controller) is opened to varying degrees by a pneumatic throttle-positioner, in so far as this is not already done by a human operator of the engine. The throttle-positioner is controlled by an electronic computer which responds to signals from an engine-idling switch, from a potentiometer responsive to throttle-valve position and from a futher potentiometer responsive to the setting of the throttlepositioner, as well as to other engine-operating parameters.

During its manufacture the carburettor is adjusted by the following method: First, the throttle-positioner is set to a position in which it delivers a specified reporte,d-back electronic signal. With the throttlepositioner held fast at this setting, the throttle valve is mechanically adjusted in position, usually by means of an adjustment screw, to produce a specified rate of flow of air through the intake passage of the carburettor.

When this has been done, the setting of the throttle-positioner, or the value of its reported-back signal, accurately represents the resulting throttle-valve position.

But it has been found that unless the potentiometer on the throttle valve of each individual example of the carburettor is adjusted individually, the reported-back signal delivered by the throttle varies from example to example in carburettors of the same construction.

2 From the German Patent Specification DE-OS 33 12 027 it is known to adjust the electronic signal-transmitter which delivers the reported-back signal representing throttle position so that when the throttle is in its "zero" position its reported-back signal has a specified value. This is intended to make individual adjustment of each example of the carburettor unnecessary.

And from the US-PS 46 37 361 a process is known for measuring throttle position without any necessity for mechanical adjustment of the potentiometer which delivers the reported-back signal representing throttle position. The carburettor is operated and the most-closed position of the throttle valve repeatedly observed and used to define the "throttle closed" position.

This known process makes it possible to compensate abrasion of the actuating mechanism for the throttle valve, and abrasion of the potentiometer.

In both these proposals adjustment of the signal transmitter takes place only at a specified "zero" position of the throttle valve which, under certain circumstances, is never reached, or only after lengthy operation of the carburettor.

Ilie intention in the invention is therefore to provide a process of the kind mentioned at the beginning but in which deviations in the reportedback throttle-angle signals from individual examples of the carburettor are rapidly corrected without mechanical adjustment being required.

The process of the invention is based on the following reasoning:

When the throttle positioner opens the throttle valve, in each individual example of the carburettor, the reported-back signal delivered by the potentiometer responsive to throttle position increases in value with the reported-back signal delivered by the potentiometer responsive to the setting of the throttle-positioner. This is illustrated in the graph of Figure 2, in which the reported-back throttle angle cc is measured on the ordinate, for different examples of the carburettor, against the reportedback t -IF I 'I i.

1 3 setting a of the throttle-positioner, measured on the abscissa of the graph. In Figure 2 it will be seen that at the adjustment point where the reported-back setting SE of the throttle-positioner is held steady for adjustment purposes, the a-lines (reported-back throttle angle) for the different examples of the carburettor come closest together, although their slopes can vary widely.

As shown in Figure 3, at the adjustment point the reported-back setting SE of the throttle-positioner can be made to indicate the same reported- back angle a of the throttle valve, for all the examples of the carburettor, by raising this, for each example, to the highest intersection point B. When that has been done the reported-back setting SE of the throttle-positioner, at the instant of adjustment, indicates exactly the same reported-back throttle angle a' in all the examples of the carburettor.

As shown in Figure 4, the envelope containing the bundle of a'-lines is now limited below by the lowest adjusted (x'-line and above by the highest. Within this envelope the throttle valve can be actuated by the throttle-positioner. Above the highest adjusted cc'-line the throttle valve is actuated only be the human operator.

On the basis of this reasoning the problem is solved by the invention which consists of a process for adjusting, by means of a signal-processor, the reported-back position signal (a) of a controller actuated by a positioner, the process comprising the following steps:

a) the positioner is set to give a specified reported-back position signal (S E); b) with the positioner held fast at this setting the controller is adjusted mechanically to a specified control position (a); c) the reported-back position signal (a) of the controller is detected; and 4 d) this signal is transmitted to the signal-processor, together with the setting signal (S) reported back by the positioner, and in which during subsequent operation of the controller, at each setting of the positioner reported back by a setting signal (S) the signal ((x) reported back by the controller is increased by adding an adjustment value (a T) to produce an adjusted signal ((x') determined by a lower envelope line (Ku), lifting the (cc) signal to a value equal to or greater than the value on the envelope line (Ku) corresponding to this reported-back signal (S) of the positioner.

Further advantageous developments of the process of the invention are described in the subsidiary claims.

The advantages attainable by the invention will become clear from the following description based on the drawing.

The drawing shows:

Figure 1 is a block-circuit for illustrating the process of the invention.

Figwes 2 to 5 are graphs.

Figure 1 is a block-circuit illustrating the method of functioning of a device for regulating the idling speed of an internal combustion engine 1. The engine has a system (a carburettor or fuel-injector), which is not shown in the drawing, for forming combustible mixture, and a throttle (the controller) 2 for controlling the flow of air or mixture entering the engine. For thi s purpose a throttle valve 4, fixed to a shaft 5, pivots in the intake channel 3 of the engine 1. The shaft 5 is rotated by a throttle lever 6. As shown in Figure 1, anticlockwise rotation of the throttle lever 6, under the influence of a tension spring 7, tending to close the throttle, is limited by a throttle-positioner 8.

I- v L 1 1 Clockwise rotation of the throttle lever 6, for opening the throttle, can be done freely by the human operator. Thus the throttle-positioner 8 determines the most-closed position of the throttle during idling of the engine.

The throttle-positioner 8 has a potentiometer 9 for reporting its setting back to an electronic control computer 11, indicated by chain lines in Figure 1, and the throttle 2 has a potentiometer 10 for reporting the position of the throttle valve 4 back to a signal-processor 12 in the electronic control computer 11.

The electronic control computer 11 contains, among other things, a memory in which are stored intended engine-idling speeds derived from a predetennined engine-operating programme. During idling of the engine the electronic control computer 11 compares, at each instant, existing engine speed with the intended engine speed, transmitting the difference to a regulator 13 for adjustment of the charge of combustible mixture fed, during each suction stroke of the piston, to each cylinder of the engine. The regulator 13 forms a signal representing the intended opening angle ((x-SoH) for the throttle valve 4, transmitting this signal to a further regulator 14 for actuating the throttle-positioner 8. The first 13 and second 14 regulators can be of any construction, for example PID regulator parts can be used.

In the graph of Figure 2 the quantity S on the abscissa represents the setting of the throttle-positioner 8 reported back by the potentiometer 9 to the electronic control computer 11. The ordinate measures the resulting throttle-valve angle a reported back by the potentiometer 10 to the signal processor 12. The bundle of lines shown in Figure 2 illustrates the scatter in the reported-back throttle-valve angles cc with varying reported-back settings S of the throttle-positioner 8, in different examples of carburettors of the same construction, as described in the Bosch technical ailicle mentioned above.

Figure 3 shows the reported-back a lines of Figure 2 shifted in position to give adjusted oc'-lines, which all intersect at a highest point B, which corresponds to a specified reported-back setting S E of the throttle-positioner 8.

6 Figure 4 represents the envelope containing the bundle of adjusted a'lines shown in Figure 3.

In Figure 5 the envelope lines of Figure 4 are shown slightly separated from each other to allow for manufacturing tolerances. The envelope is lirnited below by a lower envelope line Ku and above by an upper envelope line Ko. The envelope of Figure 5 encloses all the adjusted a'-lines derived by adjusting the reported-back a signals from the throttle valve 4.

The process of the invention will now be described with the help of Figures 2 to 5.

In the first step of the process the throttle-positioner 8 is adjusted to deliver a specified reported-back signal S E and, with the throttlepositioner 8 held fast at this setting, the throttle 2 (the controller) is adjusted to produce a specified throughput of air in the intake passage of the carburettor.

The signal-processor 12 therefore now receives the specified setting signal S E Of the throttle positioner 8, reported back by the potentiometer 9, and the corresponding a-angle signal from the throttle valve 4, reported back by the potentiometer 10.

The signal-processor 12 contains at least one memory specifying, at least, the lower envelope line Ku derived from the scattering of adjusted cc'lines for different examples of carburettors of the same construction, as illustrated in Figure 3.

In the operation of each example of the carburettor, if the throttle angle cc reported back by the potentiometer 10, anywhere over the whole range of reported-back S settings of the throttle-positioner 8, falls below the lower envelope line Ku of Figure 5, the signal-processor 12 adjusts the reported-back a signal to the adjusted value 9 cc.

The adjustment is made by adding an adjustment value a T' which in practice is always applied in the positive direction.

ZL 1, -9 I Figure 5 shows the reported-back aline Ki (before adjustment) produced by the circuit of Figure 1 for a particular example of the carburettor, and which can correspond to any one of the reported-back a-lines shown in Figure 2.

When the engine is subsequently started from cold the throttle-positioner 8 is set to give a high reported-back S signal, towards the right of Figure 5, to hold the throttle fairly wide open for a high idling speed. Under these circumstances the reported-back (x-sic,,nal, on the KI line in Figure 5, is above the lower envelope line Ku and the signal-processor 12 applies no adjustment.

But with warn-fing-up of the engine the throttle-positioner 8 retracts, rotating the throttle valve 4 towards its closed position, until the reported-back throttle angle a intersects the lower envelope line Ku.

Then the signal-processor 12, by step-wise additions of the adjustment value aT, increases the reported-back cc-angle to the adjusted value cc', the amount of adjustment reaching its maximum at the point B. After that, the maximal adjustment is maintained permanently, all through the operation of this example of the carburettor, the reported-back a-angle being converted constantly to the adjusted angle a' through all subsequent movements of the throttle-positioner 8. The line KI. has been permanently lifted, in this example of the carburettor, to the adjusted line shown at KT in Figure 5.

By the process of the invention adjusted values cc' are formed whose characteristic lines, in all examples of the carburettor, pass through the point B of the lower envelope line Ku. This provides much better correlation between the setting S of the throttle-positioner 8 and the opening angle a of the throttle valve 4. Engine-idling speed is more accurately maintained resulting, among other things, in reduced fuel consumption.

A further and surprising advantage of the invention is that it now becomes possible to determine with precision whether the controller (the throttle) is being actuated by the positioner 8 or by some other agent, in particular, in this case, by the human operator of the engine.

8 From Figure 5 it will be seen that when a' is above the upper envelope line Ko the throttle 2 is not being actuated by the positioner 8 but by another agent, for example by the human operator of the engine. On the other hand, when a' is below the lower envelope line Ku no other agent, other than the positioner 8, can be actuating the throttle 2. In the region between the two envelope lines Ko and Ku it is not possible to determine what agent is actuating the throttle 2. But it is usually assumed that the positioner 8 is the actuating agent.

Nevertheless, under certain circumstances this assumption cannot be made and it becomes necessary, for good control of the behaviour of the engine, to determine whether the throttle 2 is being actuated by the controller 8 or by another agent, such as the human operator of the engine. This can be done, for the region between the two envelope lines, by comparing the two reported-back signals S and a with each other in regard to direction of change, the ratio between the two changes and the applied adjustment. If the adjusted KT throttle line is stored in a memory and subsequently re-called, then in the region above the KT line actuation by the positioner 8 is excluded.

This makes it possible to adjust the idling position of the throttle without needing to use an idling switch, as has hitherto been conventional.

The process of the invention can, of course, be operated by adjusting the reported-back S signal, rather than the reported-back a signal, without leaving the frame of the invention.

The invention further embraces apparatus for carrying out the process above described. And it embraces a carburettor or an air-fuel supply system for a vehicle and which includes a controller actuated by a positioner, the reported back position signal of the controller having been adjusted by the process as above described.

P.

1 9

Claims

1. A process for adjusting, by means of a signal-processor, the reportedback position signal ((x) of a controller actuated by a positioner, the process comprising the following steps:

a) the positioner is set to give a specified reported-back position signal (S E); b) with the positioner held fast at this setting the controller is adjusted mechanically to a specified control position (a); c) the reported-back position signal (a) of the controller is detected; and d) this signal is transmitted to the signal-processor, together with the setting signal (S) reported back by the positioner, and in which during subsequent operation of the controller, at each setting of the positioner reported back by a setting signal (5) the signal (a) reported back by the controller is increased by adding an adjustment value (a T) to produce an adjusted signal ((x') determined by a lower envelope line (Ku), lifting the (a) signal to a value equal to or greater than the value on the envelope line (Ku) corresponding to this reported-back signal (S) of the positioner.

2. A process as claimed in Claim 1, and in which the addition is always made in the positive direction.

3. A process as claimed in Claims 1 or 2, and in which the highest adjustment value (aT) reached during operation of the controller is retained.

4. A process as claimed in Claims 1, 2 or 3, and in which after the point (S E) reported back by the positioner in step (a) of the process, the lower envelope line (Ku) has a lesser upwards slope towards higher (S) values.

5. A process as claimed in Claims 3 or 4, and in which the adjustment value (aT) is greatest at the reported-back signal (S E) of the positioner.

6. A process as claimed in Claim 5, and in which after use the highest adjustment value (aT) has been reached, the adjusted (a') line (KT) limits the range of adjustment of the controller by the positioner.

7. A process as claimed in Claim 5, and in which a specified upper envelope line (Ko) limits the region in which adjusted (cc') lines (KT) for different examples of the controller can occur after reaching the greatest adjustment value (a T), and where the controller can be adjusted by the positioner.

8. A process as claimed in Claims 6 or 7, and in which above the region limited by the (KT) and (Ko) lines for the adjusted value (cc'), which is the sum of (a) and (aT), it is assumed for operational purposes that the controller cannot be altered in its position by the positioner.

9. A process as claimed in Claim 7, and in which in the region between the upper and lower envelope lines (Ko) and (Ku), a decision is made, for operational purposes, on whether the controller is being actuated by the positioner, or not, by comparing the varying signals (S) and ((x) in regard to direction of change, the ratio between the changes and the signal adjustment.

10. A process for adjusting, by means of a signal-processor, the reportedback position signal (a) of a controller actuated by a positioner, according to any one or more of the preceding claims and substantially as hereinbefore described with reference to the accompanying drawings.

11. Apparatus for carrying out the process defined in any one or more of claims 1 to 9 and substantially as hereinbefore described with reference to the accompanying drawings.

1 1 I.

1 11

12. A carburettor or an air-fuel supply system for a vehicle and which includes a controller actuated by a positioner, the reported back position signal of the controller having been adjusted by the process as defined in any one or more of the preceding claims.

Published 1988 at The Patent Office. State House. 66'? 1 High Holborn, London WC 1R 4TP Further copies may be obtained from The Patent office, Sales Branch, St Mary Cray. Orpington, Kent BRZ 3RD Printed by Multiplex techniques ltd, St Mary Cray, Kent Con. 1,87