GB2201265A

GB2201265A - Controlling idling speed in internal combustion engines

Info

Publication number: GB2201265A
Application number: GB08802479A
Authority: GB
Inventors: Manfred Henning
Original assignee: Pierburg GmbH
Current assignee: Pierburg GmbH
Priority date: 1987-02-17
Filing date: 1988-02-04
Publication date: 1988-08-24
Anticipated expiration: 2008-02-04
Also published as: DE3704941A1; GB8802479D0; DE3704941C2; IT1219797B; FR2610991A1; IT8847532A0; GB2201265B; FR2610991B1; ES2005980A6

Abstract

In an arrangement in which derived and actual engine speeds are compared at 12 and any error is input to a positioner 14 to control a throttle valve actuator 8 to set the idle position of a throttle valve 4, a switch 9 detects whether a throttle valve lever 6 is bearing against the actuator. During idling the switch is closed and there is feedback of the actual position of the throttle valve from a potentiometer. However when the switch is open, a stored value of throttle valve position is transmitted to the valve positioner 14 instead. <IMAGE>

Description

PROCESS AND DEVICE FOR CONTROLLING IDLING SPEED IN INTERNAL COMBUSTION ENGINES The invention relates to a process for controlling the idling speed of an internal combustion engine by comparing desired engine speed with existing engine speed and transmitting the difference to an idling-speed cylinder-charge controller for producing a signal representing the desired throttle opening in the throttle-valve system which controls the intake of air or combustible mixture by the engine, the desired throttle position being transmitted to the throttle position of a throttle actuator acting on the throttle-valve system.

A device for controlling the idling speed of an internal combustion engine is already known from the July 1983 technical publication of Robert Bosch GmbH -"Technische Unterrichtung - Motor-Elektronik" - VDI - V 1/1 DE (7.83, page 33). What is described there is a carburettor whose throttle valve is advanced in the opening direction by a pneumatic throttle actuator, unless it has already been opened voluntarily by the operator of the engine. The pneumatic throttle actuator is activated by a command signal from an electronic control device which itself receives signals from an idling switch, a potentiometer responding to throttle position and a further potentiometer responding to the position of the pneumatic throttle actuator, as well as signals representing various engine-operating parameters such as engine speed.In this known device, the carburettor therefore has two potentiometers. Starting from there, the intention in the present invention is to provide a process and a device in which at least one of the potentiometers is omitted.

The problem is solved, in regard to the process, by the characteristics claimed in Claim 1 and, in regard to the device, by the characteristics claimed in Claim 5.

Further advantageous characteristics of the invention are described in the subsidiary claims.

Broadly stated.the invention provides a simplified process for controlling idling speed, which is characterised in that in the presence of an idling signal, a signal representing the existing throttle opening is transmitted to the throttle-valve positioner, whereas in the absence of an idling signal, a signal representing a stored throttle opening is transmitted to the throttle-valve positioner.

The invention provides a simplified process for controlling idling speed, and a device for performing the process. The device of the invention can be applied to the throttle valve of any kind of mixture-forming system for controlling the flow of air or of combustible mixture reaching the engine, for the purpose of controlling idling speed1 only one potentiometer and one idling switch being used.

The invention will now be described in greater detail with the help of the example represented in the drawing, in which: Figure 1 is a block circuit illustrating the method of functioning of the invention.

Figure 2 is a signal-flow diagram with building blocks.

Figure 3 is an algorithm based on Figure 2, in the form of a flow diagram.

Figure 4 is an algorithm for the positioner.

The block circuit of Figure 1 illustrates the method of functioning of an idling speed controller for an internal combustion engine 1, with a throttle-valve system 2 for controlling the flow of intake air, or intake mixture, in a carburettor or fuel-injection system, which is not shown in the drawing. The throttle-valve system 2 comprises a throttle valve 4 installed in the induction passage 3 and a throttle-valve lever 6 fixed to the throttle-valve shaft 5. The lever 6 is pulled towards a throttle-valve actuator 8 by a tension spring 7, which acts to close the throttle valve 4. The actuator 8 thrusts the lever 6 towards the throttle-open position, except when the operator of the engine has already opened the throttle valve 4.When the operator of the engine allows the throttle valve 4 to move towards its closed position the lever 6, rotating anti-clockwise, as represented in the drawing, makes contact with the actuator 8. This closes an idling switch 9, delivering a signal to the electronic control system shown in the frame 10 in Figure 1. The electronic control system 10 also receives signals from a potentiometer 11 fixed to the throttle-valve shaft 5, as well as other signals from a system of sensors responding to engine speed and the like. The electronic control system 10 contains, among other things, a memory fr storing desired engine speed.In the operation of the process the desired engine speed is compared in a comparator 12 with the existing engine speed, the difference being fed as a correction signal to a cylinder-charge controller 13, which controls the mass of fuel charged to each cylinder of the engine during each suction stroke of the piston. The cylinder-charge controller 13 produces a signal representing the desired throttle opening (a dye)' transmitting this to a throttle-valve positioner 14. The cylinder-charge controller 13 and the throttle-valve positioner 14 can be of any construction, for example P-I-D controller parts can be used.

According to the invention a memory block 15 is interposed in a conductor path 16 in the electronic control system 10 between the potentiometer 11 and the throttle-valve positioner 14. The memory block 15 also receives- signals over a branch conductor 17 from the idling switch 9 of the throttle-valve actuator 8.

When the idling switch 9 is closed, the existing throttle-valve opening is transmitted as a potentiometer value over the memory block 15 to the throttle-valve positioner 14, which uses it-to form a signal, derived from the cylinder-charge signal for the desired throttle opening, for activating the throttle-valve actuator 8. Up to this point the control of throttle-valve position follows the prior art, except for the derivation of the existing throttle-valve position from the potentiometer 11 fixed to the throttle-valve shaft.

On the other hand, when the idling switch 9 is open, the operator of the engine having opened the throttle himself, there is no idling- signal in the memory block 15 and in the parallel throttle-valve positioner 14. This interrupts the conductor path 16 in the memory block 15 by the opening of a switch 18 (Figure 2) in dependence on the idling. switch 9. Interposed between the switch 18 and the throttle-valve positioner 14 is a further memory 19 which can be a capacitor 20, as shown in Figure 2, or a memory of the control device in which a digital value is stored. The memory 19 stores the throttle-valve opening (a ex 6tored) which existed before the opening of the idling switch 9. This -signal (a ex st ed) is now applied to the throttle-valve positioner 14 instead of the existing throttle opening signal (a ex and, from this, the throttle-valve positioner 14 forms the signal for activating the throttle-valve actuator 8.

Figure 2 shows, in a frame 15, an idealised circuit for the memory block 15 of a signal-flow diagram, with the conductor path 16, the capacitor 20, 22 for amplifying and digitalising the signals, as well as a blocking diode 23 in parallel with the switch 18. The blocking diode 23 lowers the value stored in. the capacitor 20 down to a new existing throttle opening value on the potentiometer 11. This point will be taken up again in the following description of the method of functioning of the device.

Referring now to Figure 3, this represents, for the digitally constructed electronic control system 10, the sub-routine of an algorithm based on the block circuit of Figure 1. The steps of an algorithm are represented by numbers, but numbers in sequence are skipped over where appropriate.

-START - In Step 1 the old existing throttle opening (vex stored) is replaced by a newly measured throttle opening (a ex which is stored.

- In Step 2 a new existing throttle opening (a e ) is measured.

- In Step 3 it is enquired whether the- idling switch 9 is closed. If the answer is YES, then: - In Step 4, just as in Step i, the old existing throttle opening is replaced by a new one. If the answer is NO, then: - In Step 5 it is enquired whether the new existing throttle opening is smaller than the stored existing throttle opening. If the answer is YES, then: - In Step 6, just as in Steps 1 and 4, the stored existing throttle opening is replaced by the new one. If the answer is NO, then: - In Step 7 the stored existing throttle opening is retained.

END After Steps 4, 6 or 7 the sub-routine is terminated and then re-started.

Figure 4 shows d sequence diagram for a sub-routine for the algorithm of the positioner, and here again the steps are numbered.

START - In Step 1 it is enquired whether the idling switch 9 is closed. If the answer is YES, then: - In Step 2 the throttle positioner is adjusted. - If the answer is NO, then: - In Step 3 it is enquired whether the existing throttle opening (a ex) is less than the desired throttle opening (a de) - In Step 4 the command is given to advance the throttle-valve actuator 8. If the answer is NO, then: - In Step 5 the command is given to immobilise the throttle-valve actuator 8. This is followed by the command of Step 4, if necessary modified by the command: "at reduced speed".

END After Steps 2, 4 or 5 the sub-routine is terminated and then re-started.

Method of functioning Let it be assumed, as a first case, that the engine is idling with idling switch 9 closed, i.e. the operator of the engine has not opened the throttle to bring the lever 6 out of contact with the plunger of the throttle-valve actuator 8. The potentiometer 11 mounted on the throttle-valve shaft 5 emits a signal representing the existing position ( ex) of the throttle valve. After amplification, if necessary, and digitalising, if desired, this signal (a ex is stored in the memory 19.20 (Figure 2) as the value ((a ex and transmitted to the throttle-valve positioner 14.The cylinder-charge controller 13 forms a from the difference between a stored desired engine speed and a stored existing engine speed, a signal representing the desired throttle openings (#due) From this signal the throttle-valve positioner 14 forms a signal which activates the throttle-valve actuator 8.

But if one assumes, as a second case, that the idling switch 9 is open, because the operator has opened the throttle of the engine to bring the lever 6 out to contact with the plunger of the throttle-valve actuator 8, then the device functions- differently. In this case, the throttle valve positioner 14 receives, instead of a new existing throttle opening signal (v ex) , a stored-value signal (ex stored and used this to enquire whether: a) the existing stored throttle opening (apex stored is less than the desired throttle opening, (add) in which case the plunger of the throttle-valve actuator 8 is advanced, or: b) the existing stored throttle opening (apex stored is the same or greater than the desired thrott-le opening, (code)' in which case the plunger of the throttle-valve actuator 8 remai-ns immobilised.

It should be observed that circuit branching in the electronic control system 10 can be arranged in such a way that the throttle-valve positioner 14 remains uninfluenced by either of the circumstances described under a) and b) above. In particular, if the idling switch 9 is open but, due to a malfunction, the plunger of the throttle-valve actuator 8 cannot follow the throttle-valve lever 6, then the fact that ex stored) is less than (ade) as described under a) above, causes the plunger of the throttle-valve actuator 8 to advance till it strikes the lever 6, closing the idling switch 9. This makes the existing throttle opening (a ex) coincide with the desired throttle opening (a de) in the throttle-valve positioner 14.

The throttle-valve actuator 8 can be pneumatically, hydraulically or electrically powered.

Claims

1. A process for controlling the idling speed of an internal combustion engine by comparing desired engine speed with existing engine speed and transmitting the difference to an idling-speed cylinder-charge controller for producing a signal representing the desired throttle opening in the throttle-valve system which controls the intake of air or combustible mixture by the engine, the desired throttle position being transmitted to the throttle position of a throttle actuator acting on the throttle-valve system, characterised in that in the presence of an idling signal, a signal representing the existing throttle opening (a ex) is transmitted to the throttle-valve positioner (14) whereas in the absence of an idling signal, a signal representing a stored throttle opening (a ex stored is transmitted to the throttle-valve positioner (14).

2. A process as claimed in Claim 1, characterised in that when the desired throttle opening (a de) is greater than the stored throttle opening (a ex stored) the throttle-valve positioner (14) sends a command signal to the throttle-valve actuator 8 is commanding it to open the throttle valve.

3. A process as claimed in Claim 2, characterised in that the command signal sent to the throttle-valve actuator 8 is time-delayed.

4. A process as claimed in Claims 1, 2 or 3, characterised in that when the existing throttle opening (a ex) is less than the stored throttle opening (a ex stored)' the stored value is reduced to the ex stored smaller existing value before transmission to the throttle-valve positioner 14.

5. A device for performing the process of Claim 1, with a throttle-valve system for controlling the intake of air or combustible mixture by the engine; and with a throttle-valve actuator which adjusts the throttle-valve system to give a certain minimal throttle-valve opening; the throttle-valve actuator responding to signals from a throttle-valve positioner which, in turn, responds to signals from a -cylinder-charge controller, which itself forms the desired idling speed from the difference between the desired and the existing values, characterised in that when an idling switch 9 signals that the throttle-valve system 2 is set for engine idling, a signal representing the existing throttle opening (a ex is applied to the throttle-valve positioner (14) as a potentiometer value: the device including a memory (19) which stores the latest potentiometer value before a voluntary opening of the throttle valve opens the idling switch 9 and transmits the stored value to the throttle-valve positioner 14.

6. A device as claimed in Claim 5, characterised in that when the cylinder-charge controller 13 indicates that the existing throttle opening (a ex) is greater than the stored value (a ex Stored32 the throttle-valve positioner (14) prepares a command signal for commanding the throttle-valve actuator 8 to open the throttle.

7. A device as claimed in Claims 5 or 6, characterised in that when the existing throttle opening (a ex is less than the stored value (a ex stored' the stored value ex stored is reduced to the smaller existing value.

8. A device as claimed in Claims 5, 6 or 7, characterised in that the memory (19) consists of a capacitor (20), a circuit or a memory of an electronic control system (10).

9. A device as claimed in Claims 7 or 8. characterised in that the stored value is reduced to the smaller existing value by a blocking diode (23) connected in parallel to the idling switch (9).

10. A device as claimed in one of the Claims 5 to 9, characterised in that means are provided for introducing a time-delay into the output signal delivered by the throttle-valve positioner (14) to the throttle-valve actuator (8).

11. A device according to claim 5, and substantially as hereinbefore described with reference to the accompanying drawings.

12. A process according to claim 1, and substantially as hereinbefore described with reference to the accompanying drawings.