GB2253440A

GB2253440A - Ignition control circuit for the prevention of engine speed oscillations during load changes

Info

Publication number: GB2253440A
Application number: GB9202905A
Authority: GB
Inventors: Ernst Wild; Klemens Grieser
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1991-03-06
Filing date: 1992-02-12
Publication date: 1992-09-09
Anticipated expiration: 2012-02-12
Also published as: JPH04318282A; GB9202905D0; DE4107115A1; GB2253440B; JP3334903B2; DE4107115C2

Abstract

The engine speed is stabilised by identifying sudden changes in engine torque which would cause speed oscillations and changing the ignition timing to reduce these torque fluctuations. Measurements of engine speed, n, engine temperature, Tmot and engine load, tL, provide two families of characteristics 2, 5, (pre-determined by running the engine on a test bed and producing torque curves as a function of the above variables), to produce estimated values for the internal engine torque Mi and the frictional torque Mr, to produce an estimate of the effective torque Me by means of the subtraction circuit 4. This estimated torque value is passed through a low pass filter 12 to obtain a steady state value for the engine torque, Mesoll and the result is subtracted from the original estimated torque value, Me, to isolate any sudden changes in torque, AM, which is used as a measure of the torque change required to stabilise engine speed fluctuations. A division circuit 16 divides DELTA M by Me to produce a value of the relative torque change, AMrel to which further torque reductions DELTA M'rel may be added (e.g. for transmission control or drive slip control {ASR control}). This result is passed into a further low pass circuit 20 which is switchable to prevent sudden positive torque jumps. A further family of characteristics 23, having inputs of n and tL, produces a value for the ignition angle adjustment required. <IMAGE>

Description

2:15 ', ---4 4 ri - 1 Circuit arrangement f or the prevention of

rotationalspeed oscillations State of the art The invention relates to a circuit arrangement for the prevention of rotational- speed oscillations after load changes in internal-combustion engines of vehicles by variation of the ignition angle.

It is known to carry out a variation of the ignition angle in internalcombustion engines in order to prevent rotational- speed oscillations after load changes. This action on the ignition angle takes place during the restart after deceleration cut-off, during acceleration or during the opening of an idling contact.

The invention is concerned with the abovementioned problem; it shows a possibility which can be afforded in a simple and cost-effective way and by which rotational-speed oscillations are effectively prevented.

The advantages of the invention The advantage of the circuit arrangement according to the invention, having the features mentioned in the main claim, is that a limitation of the torque change by means of action on the ignition angle for the purpose of preventing rotational- speed oscillations, especially after load jumps, is carried out, so that the current torque trend (effective torque) of the vehicle drive is evaluated by means of a low-pass circuit and is subtracted from the current torque trend by means of a circuit unit, the output value of the circuit unit, which It corresponds to a torque to be reduced, serving for adjusting the ignition angle. The current torque trend (effective torque) can be determined by simple means. Furthermore, the low-pass circuit required is a very simple electrical network, thereby affording a costeffective solution. The low- pass circuit preferably has a PTI element.

According to a development of the invention, the value corresponding to the torque to be reduced is divided, by means of a division circuit, by the value corresponding to the associated effective torque in order to form a relative torque reduction. This relative torque -eduction corresponds to an ignition-angle variation. This ignition-angle variation leads to an adjustment of the ignition angle in the "retarded" direction.

It is advantageous, furthermore, if the value for the effective torque is simulated from a value of the internal torque and a value of the frictional torque. To provide the torque trend, therefore, it is merely necessary to determine the values for the internal torque and for the frictional torque. To form the value for the internal torque, there is preferably a first family of characteristics, to which the rotational speed of the internal-combustion engine and a load signal of the internalcombustion engine are fed as input quantities. To f orm the value of the f rictional torque, there is a second f amily of characteristics, to which the rotational speed of the internal-combustion engine and the engine or coolant temperature are f ed as input quantities. By means of a subtraction circuit, to which the value f or the internal torque and the value for the frictional-torque are fed as input quantities, the value of the effective torque is determined by subtracting the frictional torque from the internal torque.

To obtain the two abovementioned families of characteristics, various operating states of the internal-combustion engine are tested on an engine test stand. The characteristic values for the first family of characteristics are obtained by measurements on the 1 engine test stand for the acceleration mode according to the relation 14.0as = Mi - M'.

The characteristic values of the second f amily of characteristics are obtained by measurements on the engine test stand for the deceleration mode according to the relation 1.eas = Mr (since Mi = 0) is advantageous, moreover, if the relative torque reduction is controlled by means of a linearisation circuit.

According to a development of the invention, the output of the linearisation circuit can be connected to a third family of characteristics, to which the speed of the internal-combustion engine and the load signal are fed as influencing quantities and at the output of which the ignition-angle adjustment value is available f or torque reduction.

Finally, it is advantageous if, in order to take into account further torque reductions, especially a torque reduction of the transmission control unit for the internal-combustion engine and/or the ASR control unit (ASR = drive-slip control), these are added to the relative torque reduction by means of an addition circuit. As a result, therefore, not only is there an ignition-angle adjustment to prevent rotational-speed oscillations of the internal-combustion engine, but further units (such as for example, the transmission control unit and/or the ASR control unit) also lead to an ignition-angle adjustment in the "retarded" direction, in order to bring about a torque reduction of the internalcombustion engine.

it Drawing The invention is explained in more detail below by means of the figure. This shows ablock diagram of the circuit arrangement for the prevention of rotationalspeed oscillations of the internal-combustion engine.

Description of the exemplary embodiment

The f igure shows a circuit arrangement 1 which has a first family of characteristics 2. The rotational speed n of an internal-combustion engine (not shown) of a vehicle is fed as an input quantity to the f amily of characteristics 2. Furthermore, the first family of characteristics 2 receives a load signal tL of the internal-combustion engine as a further input quantity. Available at the output 3 of the first family of characteristics 2 is an internal torque Mi which is f ed, with a positive sign, to a subtraction circuit 4 as an input quantity.

The circuit arrangement 1 possesses, furthermore, a second family of characteristics 5 which likewise receives as input quantities the rotational speed n of the internal-combustion engine and the engine or coolingwater temperature T.t of the internal-combustion engine. Available at the output 6 of the second family of characteristics 5 is a frictional torque M, which is applied with a negative sign to the input of the subtraction circuit 4.

The output 7 of the subtraction circuit 4, at which an effective torque M. is provided, is connected to a branch point 8. The branch point 8 is connected with a positive sign to one input 9 of a circuit unit 10. The circuit unit 10 is designed as a subtraction circuit. Furthermore, the branch point 8 is connected to the input 11 of a low-pass circuit 12, the low pass of the low-pass circuit 12 preferably being designed as a PT, element. The output 13 of the low-pass circuit 12 leads with negative sign to a further input 14 of the circuit unit 10. A torque to be reduced AM is available at output 15 of the circuit unit 10.

The torque to be reduced AM is fed as a f irst input quantity and the effective torque M. as a second input quantity to a division circuit 16. For this, the division circuit 16 is connected to the output 15 of the circuit unit and to the branch point 8. The division circuit 16 divides the torque to be reduced AM by the associated effective torque M,. The result is available at an output 17 as a relative torque reduction AM..,..

The relative torque reduction AM,,3. is fed as an input quantity to an addition circuit 18 which receives as a further input quantity further torque reductions AM'..,. The further torque reductions can be, in particular, a torque reduction of a transmission control unit of the internal-combustion engine and/or of an ASR control unit (ASR = driveslip control).

At the output 19 of the addition circuit.18 is a signal which is fed as an input quantity to a low-pass circuit 20. The time constant of the lowpass circuit 20 is switchable, so that a torque pull-back suddenly required is executed without delay, but the sudden cancellation of the torque pull-back required is filtered with a higher time constant. This prevents a sudden torque jump in the positive direction. The output 21 of the low-pass circuit 20 is connected to the input 22 of a third family of characteristics 23, which weights the corresponding signal with a loadand rotational speeddependent factor and which converts it into an ignitionangle adjustment value Aaz. Emitted at the 'output 24 of the third family of characteristics 23 is the ignitionangle adjustment value Aa., by means of which an adjustment of the ignition angle is carried out, with the result that the torque of the internal-combustion engine is corrected accordingly (in the positive or the negative direction).

To obtain the characteristic values of the first family of characteristics 2 and the second family of characteristics 5, the internal-combustion engine is tested on an engine test stand.

Measurements to determine measurement values IA:Deax in the acceleration mode of the internal-combustion engine are first carried out. By this is meant the operating mode with the accelerator pedal depressed, that is to say with fuel being supplied. The relation Mmeas Mi - Mr is applicable.

Subsequently, measurements are made in the deceleration mode of the internal-combustion engine, the relation 14.eas = Mr being applicable, since the internal torque Mi assumes the value "zero". The desired characteristic values can be determined therefrom and filed in the two families of characteristics 2 and 5.

The circuit arrangement according to the invention functions in a clearly understandable way. It is based on a simple application and can be obtained by simple action on an already existing transmission control (torque reduction during the shift operation) and/or a drive-slip control.

It is possible, furthermore, to have an indication or an output of the instantaneously produced torque of the internal-combustion engine.

Claims

Claims

Circuit arrangement for the prevention of rotational-speed oscillations after load changes in internal-combustion engines of vehicles by variation of the ignition angle, characterised in that the current torque trend (effective torque = M.) of the vehicle drive is evaluated by means of a low-pass circuit (12) and is subtracted from the current torque trend by means of a circuit unit (10), and in that the output value of the circuit unit (10), which corresponds to a torque to be reduced (AM), serves for adjusting the ignition angle.
2. Circuit arrangement according to Claim 1, characterised in that the value corresponding to the torque to be reduced (AM) is divided, by means of a division circuit (16), by the value corresponding to the associated effective torque (MJ, in order to form a relative torque reduction (AM,., ).
3. Circuit arrangement according to one of the preceding claims, characterised in that the value for the effective torque (MJ is simulated from a value of the internal torque (Mi) and from a value of the frictional torque (M,).
4. Circuit arrangement according to one of the preceding claims, characterised in that, to f orm the value of the internal torque (Mi), the rotational speed (n) of the internal-combustion engine and a load signal (tL) are fed to a first family of characteristics (2).
5. Circuit arrangement according to one of the preceding claims, characterised in that, to form the value of the frictional torque (Mr), the rotational speed a 8 - (n) of the internal-combustion engine and the engine or cooling-water temperature (T.t) are f ed to a second family of characteristics (5).
6. Circuit arrangement according to one of the preceding claims, characterised in that the characteris tie values of the first family of characteristics (2) are determined by measurements on an engine test stand for the acceleration mode according to the relation 14.5 M, - M. and in that characteristic values of the second family of characteristics (5) for the deceleration mode are determined according to the relation Yim,,,, = M, (since ^. = 0), and these values are filed accordingly in the family of characteristics (2, 5).
7. Circuit arrangement according to one of the preceding claims, characterised by a subtraction circuit (4), to which the value f or the internal torque (M.) and the value f or the f rictional torque (M,) are f ed as input quantities and at the output (7) of which the value for the associated effective torque (MJ is provided.
8. Circuit arrangement according to one of the preceding claims, characterised in that the relative torque reduction (AM,,J is controlled by means of a lowpass circuit (20).
9. Circuit arrangement according to one of the preceding claims, characterised in that the output (21) of the low-pass circuit (20. 21) is connected to a third family of characteristics (23), to which the rotational speed (n) of the internal-combustion engine and the load signal (tL) are fed as influencing quantities, and in that the ignition- angle adjustment value (Aaz) is available at its output (24).
10. Circuit arrangement according to one of the preceding claims, characterised in that,, to take into account further torque reductions (AW,,J, especially a torque reduction of the transmission control unit of the internal -combustion engine and/or of the ASR control unit (ASR = drive-slip control). these are added to the 1 relative torque reduct lon (AM,,j by means of an addition circuit (18).
11. A circuit arrangement substantially as herein described with reference to the accompanying drawing-.