GB2386932A

GB2386932A - Method of controlling engine torque during a gear shift

Info

Publication number: GB2386932A
Application number: GB0207280A
Authority: GB
Inventors: Fred Roar Hemmingsen
Original assignee: LuK Lamellen und Kupplungsbau Beteiligungs KG; LuK Lamellen und Kupplungsbau GmbH
Current assignee: Schaeffler Buehl Verwaltungs GmbH; LuK Lamellen und Kupplungsbau GmbH
Priority date: 2002-03-28
Filing date: 2002-03-28
Publication date: 2003-10-01
Also published as: DE10311885A1; GB0207280D0; ITMI20030613A1; FR2837889B1; FR2837889A1; WO2003082623A1; AU2003222725A1; DE10391105D2

Abstract

A method of controlling engine 10 torque during a gear shift comprises applying a load generated by an electric machine 100, eg a starter/alternator to the engine, so that torque transmitted through a clutch 14 is matched to the torque transmitted by the clutch 14, thereby avoiding engine flare. To provide a smooth take up of drive, the torque applied to the engine 10 by the starter/alternator 100 is varied in accordance with the difference between the engine speed and the speed of the clutch 14 driven plate or, for example, an input shaft of a transmission 12. The starter/alternator 100 is controlled by a closed loop feedback circuit which varies a field winding current of the starter/alternator 100. Gears 104, 106 may be used to connect the starter/alternator 100 to a crankshaft 102 of the engine 10, alternatively a belt or chain (114, fig 2b) may be employed. In another embodiment a rotor (202) of the starter/alternator 100 is mounted directly on a drive shaft (204) and it may be a hybrid electrical drive.

Description

VEHICLE TRANSMISSION SYSTEMS

The present invention relates to vehicle transmission systems and in particular to transmission systems, automated transmission systems or automated gear shift 5 systems having an automatically controlled friction clutch and a combined starter/alterhator or similar electric machine connected directly to the engine.

With automated transmission systems having a multi-ratio gearbox coupled to an engine by means of a friction clutch, for example as disclosed in GB2088007; lo GB2079888; GB2130329; GB2229244; GB2225821; GB2225822; GB2211577; GB2233053; GB2250075; GB2265958; GB2245036;

GB2292593; GB2292594; GB2299643; GB2296046; GB2301408;

GB2316454; GB2324584; GB2338528; GB2339249; GB2354297;

GB2353835; GB2354296; GB2356438; GB0105186.1; GB0026423.4;

15 GB0025848.3; GB0025847.5; GB0029454.6; GB0025000.1; GB0024999.5;

GB0026178.4; GB0027640.2; GB0028310.1; GB0031624.0; GB01 03312.5;

GB0109222.0, whose content is expressly incorporated in the disclosure

content of the present application; in order to avoid engine flare as the clutch is disengaged for a gear shift, it is necessary to control the clutch torque so that it 20 follows the engine torque. Conventionally, the engine torque is controlled by means of the engine management control system or by means of the throttle, where this is motorized. The response time from the engine on a torque request is typically of the order of 100 to 200 ms. As a consequence there will be a delay of 100 to 200 ms from the driver initiating the gear shift until there is any 25 notable change in the engine or clutch torque. This delay will be perceived by the driver as a slow shift.

When an electrical machine such as combined starter/alternator is connected directly to the engine, it is possible to quickly and accurately control engine o torque available for transmission by the clutch by varying the torque applied by the electrical machine, by appropriate adjustment of the field winding current of

the machine. As a consequence the delay in clutch disengagement may be significantly reduced, engine flare being controlled by means of the torque applied by the electrical machine. Furthermore, the electrical machine may be used to synchronize the engine speed with the gearbox input shaft speed, after 5 the clutch has been disengaged and also to control engine torque re-build after a new gear has been engaged.

According to one aspect of the present invention, a method of controlling engine torque during a gear shift of a motor vehicle having a transmission system, an to automated transmission system or an automated gear shift system in which a multi-ratio gearbox is coupled to an engine by means of a friction clutch; and an electrical machine drivingly connected to the engine; said method comprising controlling the torque applied to the engine by the electrical machine, in order to control engine torque during a gear shift.

According to a preferred embodiment of the invention, a method of controlling engine torque during a gear shift comprises, upon initiation of a gear shift sending a torque request signal to the engine management control system; initiating a release of the clutch in a controlled manner and varying the torque 20 applied to the engine by the electrical machine in order to control engine flare.

According to a further embodiment of the invention, after disengagement of the clutch the torque applied to the engine by the electrical machine is varied to synchronize the engine speed with the clutch driven plate speed corresponding 25 to the target gear.

The torque applied to the engine by the electrical machine may be controlled by adjusting the field winding current to the machine. This is preferably achieved

by means of a closed loop feedback circuit.

According to a further aspect of the invention the torque applied to the engine by the electrical machine may be further controlled in order to control the engine torque during torque build-up as the clutch is reengaged after selection of a new gear. The invention is now described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates diagramatically an automated transmission system in lo accordance with the present invention.

Figures 2a to 2c illustrate diagramatically alternative arrangements for the drive line of the transmission system illustrated in Fig. 1; Figure 3 is a plot showing engine torque and speed and clutch torque and driven plate speed for a typical clutch showing the effect of disengaging the clutch independently of the engine torque; Figure 4 is a plot showing engine torque and speed and clutch torque and driven 20 plate speed for a typical clutch illustrating control of torque using conventional techniques; and Figure 5 is a plot showing engine torque and speed and clutch torque and driven plate speed illustrating control of torque using a combined starter/alternator in 25 accordance with the present invention.

Figure 1 of the accompanying drawings shows an engine 10 with a starter and associated starter circuit 1 Oa which is coupled through the main drive friction clutch 14 to a multi-speed synchromeshed lay shaft-type gearbox 12, via a 30 gearbox input shaft 15. Fuel is supplied to the engine by a throttle 16 which

includes a throttle valve 18, operated by accelerator pedal 19. The invention is equally applicable to electronic or mechanical fuel injection petrol or diesel engine. s The clutch 14 is actuated by a release fork 20 which is operated by a hydraulic slave cylinder 22, under the control of a clutch actuator control means 38.

A gear selector lever 24 operates in a gate 50 having two limbs 51 and 52 joined by a cross track 53 extending between the end of limb 52 and 0 intermediate of the ends of limb 51. The gate 50 defines five positions; "R" at the end of limb 52; "N" intermediate of the ends of the cross track 53; "S" at the junction of limb 51 with the cross track 53; and " + " and i_ at the extremities of limb 51. In limb 51 the lever 24 is biased to the central "S" position. The "N" position of the selector lever 24 corresponds to neutral; "R" is corresponds to selection of reverse gear; "S" corresponds to selection of a forward drive mode; momentary movement of the lever to the " + " position provides a command to cause the gearbox to shift up one gear ratio; and momentary movement of the gear lever 24 to the "-" position provides a command to cause the gearbox to shift down one gear ratio.

The positions of the lever 24 are sensed by a series of sensors, for example micro switches or optical sensors, positioned around the gate 50. Signals from the sensors are fed to an electronic control unit 36. An output from the control unit 36 controls a gear engaging mechanism 25, which engages the gear ratios as of the gearbox 12, in accordance with movement of the selector lever 24 by the vehicle operator.

In addition to signals from the gear selector lever 24, the control unit 36 receives signals from:

sensor 1 9a indicative of the degree of depression of the accelerator pedal 1 9; sensor 30 indicative of the degree of opening of the throttle control valve 18; 5 sensor 26 indicative of the engine speed; sensor 42 indicative of the speed of the clutch driven plate; and sensor 34 indicative of the clutch slave cylinder position.

The control unit 36 utilises the signals from these sensors to control actuation of to the clutch 14 during take-up from rest and gear changes, for example as described in patent specifications EP0038113, EP0043660, EP0059035,

EP01 01220 and W092/1 3208 whose content is expressly incorporated in the disclosure content of the present application.

Is In addition to the above mentioned sensors, control unit 36 also receives signals from a vehicle speed sensor 57, ignition switch 54 and brake switch 56 associated with the main braking system, for example the footbrake 58 of the vehicle. 20 A buzzer 55 is connected to the control unit 36 to warn/indicate to the vehicle operator as certain operating conditions occur. In addition or in place of the buzzer 55 a flashing warning light or other indicating means may be used. A gear indicator 60 is also provided to indicate the gear ratio selected.

:5 As illustrated in Fig. 2a, a combined starter/alternator 100 may be drivingly connected to the crankshaft 102 of the engine 10, between the engine 10 and clutch 14. The combined starter/alternator 100 may be drivingly connected to the crankshaft in any suitable manner, for example a gear 104 on the combined starter/alternator 100 engaging a gear ring 106 on the flywheel of the engine

10. Alternatively, a belt or chain drive may be used to connect the combined starter/alternator 100 to the crankshaft 102.

In the embodiment illustrated in Fig. 2b, a combined starter/alternator 100 is 5 drivingly connected to the crankshaft 102 of the engine 10, but at the end thereof opposite the clutch 14. A pulley 1 10 on the combined starter/alternator is drivingly connected to a pulley 1 12 on the crank shaft 102 by a belt 1 14.

In the embodiment illustrated in Fig. 2c, a rotor 202 of a combined starter 0 alternator 200, is mounted directly on a drive shaft 204 connecting the engine 10 to the clutch 14. A stator 206 of the combined starter/alternator 200 surrounds the rotor 202 and is fixed to a nonrotational housing of the transmission. 5 As illustrated in Fig. 3, when the vehicle is moving along steadily with the clutch engaged, the clutch torque illustrated by line 300 will be in excess of the engine torque illustrated by line 302. Upon initiation of a gear change at time to, the control unit 36 will request a reduction in engine torque illustrated by line 304.

This may be achieved by means of the engine management control system or 20 direct control of the throttle 19, where this is motorized.

There is however a time delay ot of 100 to 200 ms in the engine 10 responding to the request for reduction in torque. If consequently the clutch 14 is disengaged upon initiation of the gear change then the clutch torque will fall 25 significantly below the engine torque, as illustrated in Fig. 3. This will cause the engine speed illustrated by line 306 to increase rapidly resulting in engine flare.

In order to avoid engine flare, hitherto upon initiation of a gear change, the clutch torque has been reduced to the engine torque, disengagement of the so clutch then being controlled, so that the clutch torque follows the engine torque,

as illustrated in Fig. 4. As a result, there will be a time delay ot of 100 to 200 ms from the driver initiating the gear change, until any perceptible change is experienced, this being perceived by the driver to be a slow shift.

5 In accordance with the present invention, upon initiation of a gearshift at time to, control unit 36 requests a reduction in engine torque and at the same time commences disengagement of the clutch 14 in controlled manner. In addition, the control unit 36 controls the torque applied to the engine 10 by the combined starter/generator 100, 200, to bring the available engine torque down to the o clutch torque as illustrated in Fig. 5. The torque applied to the engine 10 by the combined starter/generator 100,200 as illustrated by line 308, may be controlled rapidly, by variation of the field winding current of the combined

starter/generator 100,200. The time delay at in engagement of the clutch 14 may consequently be significantly reduced, providing a faster shift.

Preferably the torque applied by the combined starter/alternator 100,200 may be controlled by a closed loop feedback circuit, the difference between the engine speed and clutch driven plate speed as illustrated by line 310 being monitored and the field winding current being increased or decreased, depending on the

20 difference.

The engine speed may also be controlled by means of the controlled starter/alternator 100,200 in similar manner to that described above, when the clutch 14 is disengaged, in order to synchronize the engine speed to the clutch :5 driven plate speed corresponding to the target gear.

Moreover, upon re-engagement of the clutch when the target gear has been selected, the torque re-build is controlled by means of the clutch 14 in order to provide a smooth take-up. The engine torque is controlled in order to reduce the so selected speed to zero and at the same time ensure that the engine speed and

gearbox input shaft speed have the same acceleration when slip speed is zero.

Because of time lags this is done using an open loop control system. The combined starter/alternator 100,200 may again be used to compensate for errors in engine torque control and to reduce deviations that the open loop 5 control strategy cannot predict.

While the invention has been described with reference to a semi-automated motor vehicle transmission system, it will be appreciated that the invention is applicable to any vehicle transmission system or automated gear shift system 0 including an automatically controlled friction clutch 14. Moreover instead of the combined starter/generator any suitable electrical machine, for example a hybrid electric drive, may be used to control engine torque.

The patent claims submitted with the application are proposed formulations without prejudice to the achievement of further patent protection. The applicant reserves the right to submit claims for further combinations of characteristics, previously only disclosed in the description and/or drawings.

References back used in sub-claims refer to the further development of the to subject of the main claim by the characteristics of the respective sub-claim; they are not to be understood as a waiver with regard to achieving independent item protection for the combination of characteristics in the related sub-claims.

Since the subject of the sub-claims can form separate and independent 25 inventions with reference to the prior art on the priority date, the applicant

reserves the right to make them the subject of independent claims or of division declarations. Furthermore, they may also contain independent inventions which demonstrate a design which is independent of one of the objects of the preceding sub-claims.

The embodiments are not to be considered a restriction of the invention. Rather, a wide range of amendments and modifications is possible within the scope of the current disclosure, especially those variations, elements and combinations

and/or materials which, for example, the expert can learn by combining s individual ones together with those in the general description and embodiments

in addition to characteristics and/or elements or process stages described in the claims and contained in the drawings with the aim of solving a task thus leading to a new object or new process stages or sequences of process stages via combinable characteristics, even where they concern manufacturing, testing and

Claims

r ! > _ CLAIMS

1. A method of controlling engine torque during a gear shift of a motor vehicle having a transmission system, an automated transmission system or an 5 automated gear shift system in which a multi-ratio gearbox is coupled to an engine by means of a friction clutch; and an electrical machine drivingly connected to the engine; said method comprising controlling the torque applied to the engine by the electrical machine, in order to control engine torque during a gear shift.

2. A method according to claim 1 in which, upon initiation of a gear shift; a torque request signal is generated to control the torque produced by the engine; disengagement of the clutch in controlled manner is initiated; and 5 the torque applied to the engine by the electrical machine is controlled in order to match the torque available for transmission through the clutch to the torque transmitted by the clutch, thereby avoiding engine flare.

3. A method according to claim 1 in which, during a gear shift, when the 20 clutch is disengaged, the torque applied to the engine by the electrical machine is varied to synchronize the engine speed with the speed of a driven plate of the clutch corresponding to the target gear.

4. A method according to claim 1 in which, as the clutch is re-engaged after 25 selection of a new gear, the torque applied to the engine by the electrical machine is varied in order to control the engine torque available for transmission through the clutch, in order to achieve a smooth take up of drive.

5. A method according to any one of claims 2 to 4 in which the torque 30 applied to the engine by the electrical machine is varied in accordance with the

difference between the engine speed and the speed of a driven plate of the clutch, an input shaft of the gearbox or some other driven component of the transmission. 5

6. A method according to claim 5 in which the torque applied to the engine by the electrical machine is controlled by means of a closed loop feedback circuit which monitors engine speed and the speed of a driven plate of the clutch, an input shaft of the gearbox or some other driven component of the transmission.

o

7. A method according to any one of claims 1 to 6 in which the torque applied to the engine by the electrical machine is controlled by varying the field

winding current of the electrical machine.

8. A method according to any one of the preceding claims in which the 15 electrical machine is a combined starter/alternator or a hybrid electrical drive.

9. A method substantially as described herein, with reference to and as shown in figures 1 to 5 of the accompanying drawings.