GB2329443A

GB2329443A - Automatic clutch or transmission control method which compensates for errors

Info

Publication number: GB2329443A
Application number: GB9812139A
Authority: GB
Inventors: Jochen Stinus
Original assignee: LuK Getriebe Systeme GmbH
Current assignee: LuK Getriebe Systeme GmbH
Priority date: 1997-06-13
Filing date: 1998-06-08
Publication date: 1999-03-24
Anticipated expiration: 2018-06-08
Also published as: DE19823762A1; FR2764663A1; BR9802375A; GB2329443B; FR2764663B1; GB9812139D0

Abstract

An automatic clutch or transmission control method compensates for an absence of an input signal/s or a faulty input signal/s by using other input signal/s to calculate a relevant control signal. For example, if prop/cardan-shaft sensor 52 is faulty then a gear input speed can be calculated from a mean value of the speeds of rear wheels 12 divided by an overall transmission ratio through differential 10 and a relevant gear in gearbox 6. The input signal/s are supplied from various sensor, eg gearbox input/output speed senors 28, 52 etc, to a control device, eg micro processor 44. which calculates the control signals that operate clutch actuator 46. Control devices 18, 42 and 44 may be connected by a data BUS line (eg CAN-BUS) 54 for mutual data exchange. Instead of or in addition to the BUS line 54 the control devices 18, 42, 44 may be connected through individual data lines, eg line 56.

Description

2329443 - 1 Method for controlling a clutch and/or an automated

transmission The invention relates to a method according to the 5 preamble of the main claim.

The use of automated clutches has increased considerably in recent times. They are linked with a considerable improvement in comfort and additionally lead to reduced fuel consumption since the most favourable fuel-saving gear is used more frequently owing to the reduced effort incurred in changing gear. In connection with automated shift gears automated clutches lead to the comfort of a conventional automatic vehicle without the associated disadvantages relating to increased fuel consumption which those vehicles fitted with conventional automatic gearboxes frequently have compared with comparable manualshift vehicles.

The control of automated clutches as well as of manual shift gearboxes should be designed so that the driver feels hardly any change when engaging or changing gear, more particularly feels no jolts. To this end a number of input signals are required which describe relevant operating values of the drive train and are converted by a control unit into control signals for the relevant actors. Faulty or lacking control signals can lead to serious faults which lead to an uncomfortable gear change right down to a breakdown of the vehicle.

The object of the invention is to improve the operation of the automated clutch and/or gearbox, more particularly shif t gear, in the drive train of a motor vehicle with regard to the functional reliability so that even with errors in the detection of input signals supplied to the associated control device a safe and as far as possible comfortable continuation of driving is possible.

This is achieved with the features of the main claim.

According to the invention the redundancy of the signal detection which exists in modern motor vehicles owing to the number of electronic controls is thus used by drawing on other input signals in the event of a fault in one input signal to produce the control signal which can no longer be produced as a result of the faulty input signal. This can indeed be linked with a reduced quality of the relevant control signal; but the quality is however generally such that the comfort is only slightly impaired. A breakdown is ruled out in each case.

The sub-claims are based on advantageous ways of implementing the method according to the invention.

The invention further relates to a method for compensating errors in the detect ion/process ing of input signals or in the case of calculating control signals from input signals for a control device for controlling a clutch and/or a transmission in the drive train of a motor vehicle wherein a number of input signals are supplied to the control device directly from sensors attached to the inputs and/or through a BUS data line system and from the or each input signals control signals are calculated for controlling actors wherein in the event of the absence of an input signal or with a faulty input signal the or each relevant control signal is/are calculated from one or more other input signals.

The invention will now be explained in detail by way of example with reference to the drawing in which the single f igure shows the drive train of a motor vehicle with a 3 block circuit diagram of the electronic control of a motor vehicle.

An engine 2 formed as an internal combustion engine is connected by a clutch 4 to a gearbox 4 which drives the back wheels 12 of the motor vehicle through a Cardan shaft 8 and a differential 10.

The load of the engine 2 is controlled through a throttle lever 14 whose position is detected by a sensor 16 whose output is connected to the input of a control device 18. The control device 18 is connected to further sensors such as a sensor 20 for example for detecting the position of a load control member 22 of the engine 2, a sensor 24 for the coolant temperature, a sensor 26 for the suction pipe pressure. a sensor 28 for the speed of a flywheel disc or crankshaft of the engine 2 etc. From the input signals an output signal is derived in the control unit 18 to control the actor 30 which determines the position of the load control member 22.

The brake unit of the vehicle has a brake pedal 32 whose position is detected by a sensor 34. The brake pedal 32 directly controls a brake unit 36 which is connected to the wheel brake cylinders 38 of all four wheels. The speed of the wheels is detected by the sensors 40 whose output signal like the output signal of a sensor 34 for detecting the position of the brake pedal 32 is supplied to a control device 42 which prevents a locking of a wheel for example.

In order to control the clutch 4 and the shift gear 6 a further control device 44 is provided which controls actors 46, 48 and 50 for operating the clutch 4 for a shift process and for a selection process inside the 4 r, gearbox 6. As input signals the positions of each actor or component parts operated by the actor are sent to the control device 44 by means of corresponding sensors (not shown). Furthermore the control device 44 is connected to a sensor 52 which detects the speed of the Cardan shaft 8.

The three control devices 18, 42 and 44 are known in structure per se and contain a micro processor with associated ROM and RAM. The control devices 18, 42 and 44 are connected by a data BUS line (e.g. CAN-BUS) 54 for mutual data exchange. Instead of or in addition to the BUS line 54 the control devices can be connected through individual data lines (e.g. the chain- dotted line 56) between the control device 18 and the control device 44 with which input signals or output signals of the control devices can be supplied individually to inputs or outputs of the two control devices, for example the speed signal of the sensor 28 which is used also by the control device 44.

The construction and method of operation of the assembly described is known per se and is therefore not shown in further detail. In addition to the control devices described further control devices can be provided for example a control device with which the driving stability of the motor vehicle is regulated in addition to the ABS function. The clutch 4 and gearbox 6 need not automatically be controlled by means of the control device 44. The gearbox 6 can also be formed as a conventional manual shift gearbox with a shift lever for changing gear.

For a satisfactory control of the clutch 4 and gearbox 6 it is necessary to provide the control device with, as input signals, the input speed of the gearbox (detected by the sensor 28), the output speed of the gearbox (detected - 5 by the sensor 52), the engaged gear (detected by the gearbox sensors - not shown), the position of the clutch (detected by the sensor not shown - for example within the actor 46), the engine torque (detected by a torque sensor not shown - for example on the Cardan shaft 8), the position of the throttle lever 14, a kick-down operation (full throttle) of the throttle lever 14 (detected by means of a switch - not shown) as well as the idling operation of the engine (detected by the actor 30).

As can be seen from the drawing, a part of these signals is detected by sensors which are not directly connected to the control device 44 since the signals of the associated sensors are also required by the other control devices. Thus the sensors 20, 16 and 28 are connected for example directly to the engine control device 18.

By means of the BUS line 54 or the data line 56 it is reached that the output signals of the sensors can be evaluated by several control devices. Thus sensors are spared and t he cabling expense in the vehicle is reduced. In the BUS line the signals of the sensors, if they are fed in, are provided with address name so that they can be retrieved in targeted manner.

The control device 44 is only then in a position to control or regulate the operation of the clutch 4 and gearbox 6 satisfactorily if it receives all the input signals required. Sources of error as a result of which the control device 44 does not receive all the input signals may be:

a A sensor or its connection line may be defective; A fault exists in a control device to which a required signal is supplied so that the signal is not passed on by the control device; A fault exists in the BUS system which controls the BUS line 4 or the line itself.

It will now be explained with reference to examples how by dividing up the calculations developing in the control device 44 into different blocks it is possible to compensate errors arising in the detection of input signals, wherein a compensation of faults of a sensor or the absence of data such as measuring signals of a sensor can be achieved by replacing the faulty signal through the use of a signal which is available:

a) GEAR INPUT SPEED If the sensor 52 is faulty then the gear input speed be calculated from the mean value of the speeds of rear wheels, such as the driven wheels, divided by overall transmission ratio through the differential 10 the relevant gear of the gearbox 6. If the signals calculating the gear input speed are also lacking in way then instead of the mean value of the speed of driven wheels it is possible to use the mean value of sneeds of the nondriven wheels (the sianals are fed can the the and for this the the f rom the control device 42 into the BUS line 4) If these values are also lacking then it is possible to use a signal supplied to the tachometer of the vehicle (not shown) and from these to calculate the gear input speed.

Whether an input signal is faulty each time can be determined by plausibility tests in the control device 44; for example at least when the clutch is closed the gear input speed determined by the sensor 52 must be in a 7 plausible ratio, fixed by the engaged gear, with the engine speed and/or gear output speed which is determined by the sensor 28 or another sensor.

The gear input speed is equal to a for example mean wheel speed divided by the product of the actual gear transmission ratio and the differential transmission ratio.

nGetebe nrad-gemittelt/ (iget idiff) The mean wheel speed is equal to the average of two wheel speeds wherein weighting factors can also be used for the relevant wheel speeds.

nrad-gemitteft:-- (n,ad_l+ n,d-2) 12 or generally n rad_gemittelt n rad-i Ii for all wheel speeds used of the wheels i.

By way of example the following formula can be used for calculating the gear input speed:

v fahp--eug ngetriebeeingang = z rdy?zaniisch i getriche i differential wherein the gear input speed is equal to the quotient of (30 vehicle speed) and (n times the dynamic wheel diameter times the gear transmission ratio times the differential transmission ratio).

- 8 b) ENGINE TORQUE If there is no information on the engine torque in the BUS line 4 then the engine torque can be determined from the engine characteristic field which contains the engine torque in dependence on the position of the load control member 22 and the engine speed (sensor 28) recorded. In another embodiment the engine torque can be determined f rom a characteristic field in which the intake pressure or the throttle valve position or the injection time point and the engine speed are recorded wherein the engine torque is determined as a function of the intake pressure and/or the throttle valve position and/or the injection time point and the engine speed.

c) POSITION OF THE THROTTLE LEVER, PEDAL SUCH AS ACCELERATOR If the sensor 16 for detecting the accelerator pedal position has failed then as replacement value it is possible to use the output signal of the sensor 20, such as throttle valve position sensor which at least in the stationary state exists in the relation to the position of the accelerator pedal 14 provided by a characteristic line. An inverse or inverted engine characteristic field where the throttle valve position and engine speed are recorded can likewise be used in order to determine the throttle valve position from the actual engine torque and engine speed.

d) KICK DOWN SWITCH If the kick-down switch 80 on the accelerator pedal 14 supplies no signal then as replacement valve it is possible to use the output signal of the sensor 16 which detects the operation of the accelerator pedal and the operation path of the accelerator pedal. The signal of the sensor 16 can on exceeding a predefinable threshold value be evaluated as the kick-down operation.

e) IDLING SWITCH If there is no information in the activation of the idling switch possible to use as replacement output signal of the sensor 34 signal of the sensor 20 wherein certain position can be evaluated idling switch is a control device 44 on the (not shown) then it is value the value of the or value of the output each understepping of a as idling operation. An switch which detects that an accelerator pedal activation does not exist. This sensor is thus coupled to the accelerator pedal and indicates whether the accelerator pedal is activated or not.

From the existing examples it was explained how in the absence of a normally directly measured signal as input signal of the control device 44 output signals of other sensors can be accessed which are supplied to other control devices and are sent from these control devices through the BUS line 54 or can be accessed on other data lines 56. The examples can be expanded in many ways.

It is advantageous if wheel speed signals of at least two wheels are processed into one mean or processed signal by the control unit. It is advantageous if wheel speed signals of at least one wheel are processed by the control unit. By processing is also meant averaging, filtering or smoothing or converting, such as scaling, signals which are detected by way of example as a function of the time.

- 10 The present invention relates further to the earlier application DE 19 709 417 whose contents belong expressly to the disclosure of the present application.

The patent claims filed with the application are proposed wordings without prejudice for obtaining wider patent protection. The applicant retains the right to claim further features disclosed up until now only in the description and/or drawings.

References used in the sub-claims refer to further designs of the subject of the main claim through the features of each relevant sub-claim; they are not to be regarded as dispensing with obtaining an independent subject protection for the features of the sub-claims referred to.

The subjects of these sub-claims however also form independent inventions which have a design independent of the subjects of the preceding claims.

The invention is also not restricted to the embodiments of the description. Rather numerous amendments and modifications are possible within the scope of the invention, particularly those variations, elements and combinations and/or materials which are inventive for example through combination or modification of individual features or elements or process steps contained in the drawings and described in connection with the general description and embodiments and claims and which through combinable features lead to a new subject or to new process steps or sequence of process steps insofar as these refer to manufacturing, test and work processes.

Claims

1. Method for compensating errors in the detect ion/process ing of input signals for a control device for controlling a clutch and/or a transmission in the drive train of a motor vehicle, wherein a number of input signals are supplied to the control device directly from sensors attached to the inputs and/or through a BUS data line system and from the or each input signal(s), control signals are calculated for controlling the actors, characterised in that in the absence of an input signal or with a faulty input signal the or the relevant control signal is/are calculated from one or more other input signals.

2. Method according to claim 1 characterised in that in the event of a faulty or lacking wheel speed signal of the driven wheels a wheel speed signal of the non-driven wheels is used.

3. Method according to claim 1 characterised in that in the event of a faulty or lacking wheel speed signal of the non-driven wheels a wheel speed signal of the driven wheels is used.

4. Method according to claim 1 characterised in that in the event of a faulty or lacking gear output speed signal at least one wheel speed signal or signal of several wheel speed signals of the non-driven or driven wheels is used.

5. Method according to claim 1 characterised in that with a faulty or lacking gear input speed signal at least one wheel speed signal of a driven or non-driven wheel and the steering angle inclusion is used.

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6. Method according to claim 1 characterised in that in the event of a faulty or lacking wheel speed signal of the non-driven wheels each one wheel speed signal of the driven wheels and one wheel speed signal of the non-driven 5 wheels is used.

7. Method according to claim 1 characterised in that in the event of a faulty or lacking gear input or gear output speed signal each one wheel speed signal of the driven wheels and one wheel speed signal of the nondriven wheels is used.

8. Method according to claim 1 characterised in that in the event of a faulty or lacking wheel speed signal a signal corresponding to the vehicle speed, such as a tachometer signal, is used.

9. Method according to at least one of the preceding claims characterised in that in the event of a faulty or lacking engine torque signal a signal corresponding to the engine torque is determined from the engine characteristic field containing the position of a load control member and/or injection time point and/or intake pressure and the speed of the engine.

10. Method according to one of the preceding claims, characterised in that in the event of a faulty or lacking throttle lever signal a signal corresponding to the position of a load control member is used.

11. Method according to one of the preceding claims characterised in that in the event of a faulty or lacking throttle lever signal an inverse or inverted engine torque characteristic field with engine torque and engine speed 13 and throttle valve position is used in order to determine the signal representing the throttle lever position.

12. Method according to at least one of claims 1 to 11 characterised in that a faulty or lacking kick-down signal is replaced by a throttle lever signal which indicates that the throttle lever is operated beyond a predetermined boundary value.

13. Method according to at least one of claims 1 to 11 characterised in that a faulty or lacking kick-down signal is replaced by a throttle lever signal which indicates that the deflection of the throttle lever was changed by a predefinable amount.

14. Method according to at least one of the claims 1 to 14 characterised in that a faulty or lacking idling switch signal is replaced by a throttle lever signal which indicates that the throttle lever is operated by less than a threshold value.

15. Device for controlling an operation of an automated clutch in the drive train of a motor vehicle wherein control processes are carried out, more particularly 25 according to the preceding claims.

16. Method for controlling a clutch characterised by its special method of action and design according to the present application documents.

17. Method for controlling a clutch substantially as herein described with reference to the accompanying drawings.

14 -

18. Device for controlling the operation of an automatic clutch, substantially as herein described with reference to the accompanying drawings.