EP0928378A1

EP0928378A1 - Automatic clutch

Info

Publication number: EP0928378A1
Application number: EP97944731A
Authority: EP
Inventors: Franz Kosik; Thomas Grass
Original assignee: DaimlerChrysler AG
Current assignee: Daimler AG
Priority date: 1996-09-25
Filing date: 1997-09-18
Publication date: 1999-07-14
Also published as: BR9711546A; US6047800A; DE19639291C1; WO1998013619A1

Abstract

The invention concerns an automatic clutch in a motor vehicle drive train. An automatic control device constantly determines values for the travel of an adjusting unit actuating the clutch and associated values of the moment transmitted by the clutch in order to establish whether the travel available is sufficient to reach a threshold value of the transmitted coupling moment. A warning signal is optionally emitted.

Description

Automatically controlled clutch

he invention relates to an automatically controlled clutch in the drive train of a motor vehicle, with a clutch actuating motorized actuator which is controlled by a sensor system which monitors the actuating path of the actuator and other predetermined parameters and generates a wear signal when the clutch is excessively loose t has changed operating behavior.

In motor vehicles with conventional internal combustion engines, a transmission is arranged in the drive train in order to be able to change the transmission ratio between the speed of the vehicle engine and the speed of the drive wheels in accordance with the respective driving speed and load on the vehicle. In conventional transmissions switched by the driver, the flow of power between the engine and drive wheels must be interrupted by opening a clutch while changing a gear.

It is generally known to use automatically controlled clutches for this, i.e. the clutch is automatically opened when changing a gear stage and then closed again.

In addition, the clutch is automatically controlled when the vehicle starts off. As soon as one is suitable for starting Nete speed step is inserted, the clutch can be automatically closed weakly, for example, such that a low torque is transmitted, which is sufficient to slowly crawl the vehicle to put in motion. As soon as the engine power and the engine speed are increased by actuating an accelerator pedal or another power control element, the clutch is automatically controlled in the sense of an increase in the transmissible torque. In simple terms, the clutch is then increasingly closed.

These known automatic clutches work in the manner of friction clutches, the frictional engagement of which is controlled by the associated actuator of the clutch.

The friction linings of such clutches are subject to unavoidable wear. The consequence of this is that the maximum torque that can be transmitted by the clutch falls below the torque that can be generated by the engine and the clutch can consequently “slip” comparatively frequently. The heat of friction generated in this way can destroy the clutch.

In the case of a clutch actuated by the driver, the state of wear can often be recognized by the pedal travel or the actuating force or in some other way by the “actuation feeling”.

In the case of an automatically controlled clutch, it is generally known to monitor parameters correlated with the clutch wear.

In a clutch of the type specified at the beginning of DE 30 43 348 A1, the gripping point of the clutch is reached Detection of the operating behavior of an electric servomotor of the clutch detected. A characteristic change in the electric drive current of the electric motor occurs at the gripping point. The actual gripping point position of the clutch determined in this way is communicated to a setpoint generator provided as part of the clutch control, which specifies the setpoint positions of the electric motor in the clutch control as a function of parameters. This enables the setpoint generator to adapt the setpoint signals given to the actual state. As soon as excessive grip point migration is detected, a wear signal is generated.

It is known from DE 36 01 708 A1 to calculate the instantaneous friction power for monitoring the frictional power of a friction clutch and for monitoring the friction lining wear from the moment currently transmitted by the clutch and the difference between the input-side and the output-side speed of the clutch to determine the average friction power of the clutch process. After each start of driving operation, the average frictional power values of the clutch processes that follow after starting are summed up and, after taking into account standard values for cooling, compared with a maximum permissible friction power value predetermined for the clutch. If a maximum permissible friction power value is exceeded, a warning signal for thermal overload of the clutch is triggered. By monitoring the slip of the clutch in the state of thermal overload, a criterion for inadmissibly high wear of the clutch friction linings can be obtained. The object of the invention is to provide an automatically controlled clutch with an exact wear indicator.

This object is achieved in that the sensor system comprises at least one signaling device, the signals of which represent a torque transmitted by the clutch or allow to determine that sensors are present, the signals of which indicate whether the clutch is working with slip, the at Slipping value of the transmitted torque of the clutch is assigned to the respective value of the actuating path of the actuating unit as a torque that can be transmitted by the clutch and is stored together with the latter value, and that a warning signal is generated when the maximum achievable clutch when the actuating path is exhausted. moment falls below a threshold.

The invention is based on the general idea of regularly recording the torque actually transmitted by the clutch and the actuating path of the actuating unit and determining therefrom the value of the maximum torque that can be transmitted by the clutch when the actuating path available for the actuating unit is exhausted or whether a predetermined threshold value of the transmissible torque is exceeded when the travel range is exhausted. Here, the fact is used that the torque M _κ transmitted by the clutch in each case can easily be determined from the respective engine torque M _M as well as the moment of inertia of the engine J _M given by the design of the engine and the temporal change in speed of the engine dω / dt as follows : M _κ = M _M - J _M dω / dt. Since modern engines of motor vehicles are provided with an automatic engine control, which continuously records the torque generated by the engine or analogous quantities as well as the engine speed, the engine-side parameters necessary for the determination of the torque actually transmitted by the clutch are always available. If the actuating path of the actuating unit is now also detected, it can be continuously determined which torque is transmitted or can be transmitted in the respective position. This offers the possibility of generating a warning signal as soon as the "travel reserve" is no longer sufficient.

According to the invention, it is constantly checked whether the clutch slips or not. For this purpose, the input speed on the clutch (this speed is specified by the engine speed) can be compared with the output speed on the clutch (this speed can be determined from the speed of the drive wheels and the gear ratio of the respective gear stage). As soon as the clutch slips, the torque transmitted by the clutch is assigned to the respective travel of the actuating unit as a transferable torque. The values assigned to one another are stored and continuously adapted so that a characteristic curve or a corresponding characteristic value table is available which reproduce the torque which can be transmitted by the clutch as a function of the actuating path of the actuating unit.

Otherwise, with regard to preferred features of the invention, the claims and the following explanation of the Referring to the drawing, particularly advantageous embodiments are described.

It shows

Fig. 1 is a schematic representation of a drive train of a motor vehicle and the components essential for clutch control and

Fig. 2 is a schematic representation of a hydraulically operated clutch.

1 is an internal combustion engine 1 via an automatically operated clutch 2 and a transmission 3, the gears or gears of which are changed by manual actuation of a shift lever 4, and a drive shaft 5, e.g. a propeller shaft, drivingly connected to drive wheels 6 of a motor vehicle, which is not shown in any more detail.

The clutch 2 is actuated automatically by means of a motorized actuator 7, for the control of which a sensor system is provided for monitoring various parameters of the driving operation.

This sensor system comprises a sensor arrangement 8, which is assigned to the transmission 3 or the shift lever 4 and detects its positions and / or movements and thus knows the respectively selected gear or gear.

The position of an organ serving to control the power of the engine 1 is registered by a sensor 9, for example a throttle valve 10 of the air intake system of the engine 1. Furthermore, the sensor system includes a displacement sensor 11, which is assigned to the actuating unit 7 and detects its position and thus a parameter which is analogous to the magnitude of the torque that can be transmitted by the automatic clutch 2.

The control circuit 12 also communicates with an engine control 13, which among other things has the task of keeping the engine speed largely independent of the load on the engine at a minimum speed, for example the idling speed. This engine controller 13 also generates signals that represent the respective speed of the engine 1 and / or the torque generated by the engine 1.

Otherwise, the control circuit 12 communicates with speed sensors 14, which are assigned to the vehicle wheels.

Based on the exchange of information with the engine controller 13, the control circuit 12 can determine the torque actually transmitted by the clutch 2. At the same time, the control circuit 12 knows the position of the actuating unit 7. In addition, the control circuit 12 can, on the basis of the signals from the engine control 13, which also reproduce the speed of the engine 1, and the signals from the speed sensor 14 in conjunction with the signals coming from the sensor arrangement 8, which indicate the inserted gear stage and thus the respective gear ratio, determine whether the clutch 2 "slips", ie whether the speeds of the input side and the output side of the clutch 2 differ. If this is the case, the respective position of the Actuating unit 7, each of which is transmitted by clutch 2 assigned torque, because in the case of a sliding clutch 2, the torque actually transmitted by the clutch 2 corresponds to the torque that can be transmitted in the assigned position of the actuating unit 7.

On the other hand, if the clutch 2 does not drag, i.e. If the input-side speed on clutch 2 matches the output-side speed on clutch 2, the torque transmitted by clutch 2 is only the minimum value of the torque that can be transmitted at the respective position of actuator 7.

As a result, the control circuit 12 can thus continuously determine and store values that are assigned to one another between the actuating stroke of the actuating unit 7 and the torque that can be transmitted by the clutch 2, and extrapolate therefrom whether the available actuating path of the actuating unit 7 is sufficient to achieve a threshold value for the transmissible torque of the clutch 2 .

If this is not the case, a warning signal is generated or saved so that it can be queried.

In addition, the value of the maximum torque that can still be transmitted by the clutch 2 can also be determined and stored in such a way that it can be queried, so that information about the state of the clutch 2 is always available, for example during inspections of the vehicle.

The engine 1 (not shown in FIG. 2) (cf. FIG. 1) carries on an output part of its crankshaft a flywheel 16 which is non-rotatably connected to the crankshaft and which is firmly attached to it a substantially bell-shaped, ring-like clutch housing 17 is connected. E ne input shaft 18 of the transmission 3 is arranged coaxially with the flywheel 16. A drive plate 19 of the clutch 2 is connected in a rotationally fixed manner to this input shaft. This drive plate 19 is axially resilient, such that friction linings 20, de are arranged on the outer circumference of the drive plate 19 on its two end faces, can be pressed axially against the flywheel 16. On the clutch housing 17, a plate spring 22 is held by means of bearing rings 21, the concave side of which faces the flywheel 16. On the outer circumference, the plate spring 22 carries an annular pressure plate 23, which - seen in the axial view - completely covers the friction linings 20 of the driving disk 19 radially. On the inner circumference, the plate spring 22 is rotatably supported on a release bearing 24 which is axially displaceably rotatably supported on the input shaft 18.

The release bearing 24 is gripped by a release fork 25 which forms a lever which is movable about a pivot axis perpendicular to the axis of the input shaft 18. The release fork 25 is actuated by means of a hydraulic slave cylinder 26, which communicates via a hydraulic line 27 with a hydraulic master cylinder 28, the piston of which can be moved by an electric motor 29 in the example shown. This electric motor 29 forms, together with the slave cylinder 26, the hydraulic line 27 and the master cylinder 28, the actuator 7 of FIG. 1 and is actuated by the control circuit 12 of FIG. 1.

The coupling 2 shown works as follows: The plate spring 22 tries to push the release bearing 24 into an end position to the right and to push the pressure plate 23 in FIG. 2 to the left such that the driving plate 19 with its friction linings 20 axially between the facing end faces of the flywheel 16 and the pressure plate 23 pinched and a very high frictional connection between the flywheel 16 and pressure plate 23 on the one hand and the drive plate 19 or the friction linings 20 on the other hand is achieved. If the release bearing 24 is displaced in the direction of the flywheel 16, since the piston of the master cylinder 28 is inserted into the master cylinder 28 by means of the electric motor 29, the aforementioned positive connection is initially increasingly reduced. When the release bearing 24 is shifted further to the left, the driving disk 19 with its friction linings 20 is then released axially between the flywheel 16 and the pressure plate 23, ie the clutch 2 is opened completely.

The displacement sensor 11 of FIG. 1 can be assigned to the release fork 25, so that the signals from the displacement sensor 11 represent the position of the release fork or the release bearing 24.

Claims

claims

1. Automatically controlled clutch in the drive train of a motor vehicle, with a clutch actuated motorized actuator, which is controlled by a sensor system that monitors the actuating path of the actuator and other predetermined parameters and generates a wear signal when the clutch has an excessively changed operating behavior characterized in that the sensor system comprises at least one signal transmitter device (9, 13, 14), the signals of which reproduce a torque transmitted by the clutch (2) or permit the determination that sensors (9, 14) are present, the Reproduce signals as to whether the clutch (2) works with slip, the value of the transmitted torque of the clutch occurring during slip being assigned to the respective value of the actuating path of the actuating unit (7) as a torque which can be transmitted by the clutch and stored together with the latter value, and that a warning signal is generated if this occurs at out the maximum achievable transferable clutch torque falls below a threshold value.

2. Coupling according to claim 1, characterized in that a dependency between the clutch torque and the travel of the actuator (7) reflecting characteristic curve or table of values is continuously adapted.

3. Coupling according to claim 1 or 2, characterized in that the actuating unit (7) is at least briefly brought into its end position for the closed coupling (2) in normal driving conditions to determine a remaining travel.

4. Coupling according to one of claims 1 to 3, characterized in that from the mutually assigned values of the actuating stroke of the actuating unit (7) and the transmissible torque of the clutch (2) a value for the maximum transmissible torque of the clutch is determined or extrapolated and - in particular for Inspections of the vehicle - can be queried.