HK1069425A - Method and device for adapting clutch torque - Google Patents

Description

Method and device for adapting the torque of a clutch

The invention relates to a method and a device for adapting a relationship between a torque transmittable by a clutch and a control variable for controlling a clutch actuating device, which is stored in an electronic control unit, the clutch being included in an automated motor vehicle drive train having a torque detection device arranged between the clutch and a transmission with a continuously variable transmission ratio for generating an output from which the torque transmittable by the clutch can be calculated.

Automated motor vehicle transmissions, in particular with continuously variable transmissions, such as conical-pulley-wrap-contact transmissions, are becoming increasingly interesting because of the comfort and reduction in fuel consumption achievable therewith.

Fig. 1 shows a block diagram of such a drive train.

The internal combustion engine 2 is connected via a clutch 4 to a first conical disk pair SS1 of a conical-disk-wrap contact transmission 6. A wrap-around contact 8 is looped between the first cone pair SS1 and the second cone pair SS2 of the cone-wrap-around contact transmission 6. The transmission ratio between the input shaft 10 and the output shaft 12 of the conical-disc-surrounding-contact transmission 6, which is transmitted via the surrounding contact 8, is changed by a reverse change in the distance between the conical discs of the respective conical-disc pair. A torque detection device 14 is arranged between the clutch 4 and the cone pulley pair SS1, which detects the torque transmitted by the clutch 4 and generates a hydraulic pressure P in the hydraulic outlet line 16_MFThe hydraulic pressure is related to the torque acting on the clutch output shaft 9.

Such a torque detection device 14 is described, for example, in the "requirements for a pressing system" on pages 161 to 174 of the proceedings of the sixth technical commission of Luk (1998), and comprises a component connected in a rotationally fixed manner to the output shaft of the clutch 4 and a component connected in a rotationally fixed manner to the input shaft 10, which components are formed by profiles and rolling bodies arranged between the profiles, in such a way that, as the torque increases, the distance between the profiles or components changes and thus the size of the outlet acted on by the pressure medium changes, so that the hydraulic line 16 branching off upstream of the outlet has a pressure P which increases as the torque transmitted by the clutch 4 increases_MF。

The pressure P_MFIs directly fed to the cone pair SS1 and SS2, whereby itA torque-dependent contact force is generated with which the conical disk pairs bear against the wraparound contact 8.

In order to adjust the conical-pulley-surrounding contact-element transmission, an adjusting device 20 is provided, which additionally acts on the conical pulley pair with an adjusting pressure pv in such a way that the transmission ratio of the transmission can be adjusted.

For actuating the clutch 4, an actuating device 22, which is operated, for example, hydraulically, is provided.

For controlling the system, an electronic control device with a microprocessor and associated memory is provided, the input 26 of which is connected to sensors for detecting drive train-related operating parameters, such as engine speed, position of the load control element, position of the running pedal, speed of the individual axles, and pressure P is detected by sensor 28_MF(ii) a Its output 27 controls various actuators, such as the adjusting device 20, the operating device 22, the load adjusting mechanism of the internal combustion engine.

Torque-dependent pressure P generated by torque sensing device 14 and by the same_MFThe advantages obtained are: the contact pressure between the conical disk and the wraparound contact element is accordingly adapted to the torque which is instantaneously present at the clutch output shaft, and thus an excessive contact pressure which occurs in systems with electronic contact pressure devices due to inaccuracies in the torque detection is avoided.

Given a coefficient of friction between the conical disk surface and the wrap-around contact piece, the minimum pressing force F required to avoid slipping increases approximately linearly with the torque T, with the pressing force requirement increasing with increasing transmission ratio (underdrive). For reasons of reliability, for example to compensate for fluctuations in the coefficient of friction, the actual pressing force is greater than the minimum pressing force, as a result of which slipping is reliably avoided. On the other hand, the pressing force cannot be unnecessarily large, since unnecessarily high forces would lead to wear and energy losses of the hydraulic system.

By providing a pressure P proportional to torque_MFAnd thereby provide torque correctionThe torque detection device 14 of the specific contact pressure force can therefore only be reached at the transmission ratio i_varAn unnecessarily large pressing force is obtained when the reduction is made.

This is illustrated in fig. 2.

Curve I gives the torque T at maximum allowable₁The minimum pressing force required in the case of (2). As can be seen, this minimum pressing force varies with the transmission ratio i of the transmission 6_varDecreases (the gear ratio is changed from the deceleration drive to the acceleration drive). Its output pressure P_MFThe torque detection device 14, which is only torque-dependent, must be designed such that the maximum permissible torque T is reached₁Under the condition of pressure P_MFThe pressing force F generated is 25% above the minimum required pressing force at the maximum possible transmission ratio of the transmission (for example, approximately 2.5). Because of P_MFAnd a speed change ratio i_varIndependently of P_MFA horizontal straight line A is obtained₁It represents P_MFAnd i_varThe relationship (2) of (c).

Curves II and a2 show a similar relationship for the torque T2, which torque T2 corresponds to 25% of the maximum permissible torque.

In order to change the gear ratio i_varIn order to better adapt the required amount of the pressing force, which can be increased to be unnecessarily high when the pressing force is reduced, it is known to design the torque detection device in two stages, i.e. for example in the transmission ratio i_varSwitching pressure P when 1_MFA constant of proportionality related to the torque so as to obtain an attenuated pressing force and thus a smaller pressing force B₁. In this way, it is possible to work with less force and correspondingly less energy consumption of the hydraulic system.

Pressure P_MFRelation with torque at a certain speed ratio i_varThe switching in time can be effected, for example, in that: at a certain position of the movable plate of the bevel disk pair SS1 (in the example shown, a position corresponding to transmission ratio 1), the torque detection device includesThe area of the portion loaded by the pressure increases jumpinedly.

An important prerequisite for a perfect and comfortable operation of the drive train is a precise control of the clutch 4. In particular, at start-up and also at gear shifting, for "exciting" operation which is free of jerks and which is satisfactory for sport-type driving, the clutch must be controllable in such a way that the torque transmitted by the clutch is precisely matched to a given torque which is dependent on the operating parameters of the drive train. For this purpose, a characteristic curve is stored in the control device 24, which characteristic curve assigns a setpoint value for the torque that can be transmitted by the clutch 4 for each value of the control variable, such as current or voltage, supplied to the actuating device.

Due to changes in wear or other parameters, the actual value, which is set by the control variable corresponding to the setpoint value, changes when the operating device 22 is controlled, or wear or changes in the clutch 4 will cause a difference between the setpoint torque and the actually occurring clutch torque, whereby the clutch torque or the relationship between the control variable and the clutch torque must be adapted or updated. As described in DE 19951946 a1, this is achieved in that: the pressure P at the output of the torque detection device 14 is determined according to the following relationship_MFTo calculate the instantaneous actual torque T transmitted by the clutch 4₁：

T₁＝c×P_MF

Where c is a parameter which, in the case of a single-stage torque detection device, has a constant value over the entire transmission ratio range of the transmission, and in the case of a two-stage torque detection device has two values, between which a changeover takes place at a predetermined transmission ratio. Since this parameter remains constant over a large transmission ratio range both in the case of a single-stage and in the case of a two-stage torque detection device, it is not necessary to know the exact transmission ratio in the adaptation method. But only to ensure that the transmission ratio is within a certain range.

The clutch torque can be adapted in a simple manner in that the control is carried outIn the device 24, according to the pressure P detected by the sensor 28 and delivered to the control device_MFThe torque actually transmitted by the clutch 4 is calculated from the relation and compared with a given torque of the clutch stored in the control device 24 and according to which the operating device 22 is controlled. If the torque T is transmitted instantaneously and is continuously detected by the torque detecting device 14₁With a given torque T adjusted by the operating means 22_SIf there is a deviation from each other, the relationship between the control variable and the predetermined torque is corrected in such a way that the two torques match or approach each other. It will be appreciated that such an adaptation is only possible in certain operating states, for example in the case of slipping of the clutch 4, since the torque which can be transmitted by the clutch and is controlled by the operating device 22 only then corresponds to the torque actually transmitted and detected by the torque detection device 14.

A torque detection device developed further, for example, a hydraulic stepless torque sensor is configured as follows: illustrating the torque T transmitted instantaneously₁And pressure P_MFParameter c of the relationship between_varApproximately continuously, so that the grading curve AB according to fig. 2 transitions into a curve which is approximately 25% above the required minimum pressing force curve in terms of pressing force. In the case of such a torque detection device of stepped design, the adaptation of the clutch torque can no longer be achieved in a simple manner, since the relation T₁＝c×P_MFAnd where c is constant or approximately constant, is no longer valid over a large transmission ratio range (2-step torque sensor), or continuous transmission ratio dependencies must now be taken into account. Since one of the components of the clutch torque adaptation is the stationary state of the motor vehicle, the transmission ratio of the continuously variable transmission cannot be known at such operating points (in which the transmission ratio is determined from the wheel speeds), and therefore a proportionality constant relating to the transmission ratio cannot be calculated. For this reason, in the proposed method, a geometrically unique transmission ratio is advantageously set before or during the adaptation, so that the proportionality constant can be calculated from the transmission ratio which cannot be calculated under certain conditions but is still geometrically present.

The object of the invention is to provide a method and a device for adapting the torque of a clutch, by means of which method or device a torque is detected and a pressure P is generated_MFThe adaptation can be realized in the torque detection device in which the relation therebetween is steplessly changed.

This object is achieved by a method for adapting a relationship between a torque transmittable by a clutch and a control variable for controlling a clutch actuating device, which is stored in an electronic control unit, the clutch being arranged in an automated motor vehicle drive train having a torque detection device arranged between the clutch and a transmission with a continuously variable transmission ratio for generating an output variable related to the detected torque and the instantaneous transmission ratio, in which method the torque transmitted by the clutch is calculated from the instantaneous transmission ratio and the value of the output variable, and in which method the transmitted torque is allocated to the control variable as an updated transmittable torque in an operating state of the clutch in which the transmittable clutch torque is the same as the transmitted clutch torque.

The method according to the invention proceeds from the relation T₁＝c(i_var)×P_MFWherein the parameter c is related to the transmission ratio of the transmission and follows the transmission ratio i of the transmission or continuously variable transmission, e.g. in the sense of the relationship shown in fig. 2_varThe reduction in the required minimum pressing force is increased in such a way that a good fit is achieved which retains a sufficient reliability distance, for example 25%, for the required minimum pressing force.

Since the instantaneous transmission ratio of the transmission is known during adaptation in the method according to the invention, the output variable of the torque detection device, such as the current, the hydraulic pressure or another physical variable, can be used according to the relationship T₁＝c(i_var)×P_MF(wherein P is_MFRepresenting the output) to calculate the torque instantaneously transmitted by the clutch. When the clutch 4 is in a state in which the torque transmitted by it is related to the control variable of the input operating device 22, e.g. the current, by a single value or is brought into such a state by a change in the currentA given torque T to be adjusted, e.g. in the case of a slip condition_SIs related to the detected actual torque T₁The comparison and, if there is a deviation, a corresponding correction of the parameters stored in the control device 24 are carried out, whereby the relationship between the control variable and the set torque is adapted. For example, whether the clutch is in a slipping state can be determined as follows: the engine responds with a change in rotational speed at a constant position of the engine load adjusting mechanism when the control amount delivered to the operating device 22 is changed. The slip state of the clutch can also be calculated from the difference in rotational speed between the engine rotational speed and the rotational speed of the clutch output shaft, wherein the necessary sensors for detecting the respective rotational speeds are usually present in continuously variable transmissions.

The above-described adaptation cannot of course be used in all operating states of the drive train, for example when driving with the maximum possible torque, since the clutch cannot be disengaged at this time.

Advantageously, the transmission ratio when adapting is the maximum possible transmission ratio of the transmission, since this maximum possible transmission ratio is a known quantity in the sense of the control device (24). The transmission is set to the maximum possible transmission ratio in different states, for example after a slow braking of the motor vehicle until an approximately standstill or a slow braking at a generally low speed. For the adjustment of the transmission ratio, it is necessary to identify the respective limit transmission ratio in the deceleration and acceleration drives. These quantities can be obtained by corresponding learning methods. The maximum possible transmission ratio (UD limit) of the transmission is assumed to be known for this reason, so that this state of the transmission can be reliably recognized.

It is advantageous to adapt the transmission to a stationary or creeping vehicle, in which the transmission is in its maximum possible transmission ratio state.

The transmission with continuously variable transmission ratio adjustment can be of different design, for example in the form of a friction-wheel transmission. When the transmission is a conical-disk-wrap-contact transmission, it is advantageous to ensure the shortest possible transmission ratio in that the conical disk pair (SS2) on the output side is loaded with increased pressure before or during the fitting process in order to press the wrap-contact. This ensures that the transmission does not leave its maximum possible transmission ratio.

Another possibility for ensuring that the transmission is in its maximum possible transmission ratio state is: in a transmission control unit, which may be a component of the control device 24, for example, a transmission setpoint value is initiated before and during adaptation, which corresponds to a transmission ratio that is greater than the maximum possible transmission ratio. This makes it possible to reliably adjust the transmission to its final stop position before the fitting and to retain it in this final stop position during the fitting.

A further possibility for ensuring that the transmission is in its maximum possible transmission ratio state when fitted is that: an increased given input speed of the transmission is updated before and during the adaptation, so that the transmission is adjusted to the maximum possible transmission ratio range and is held there in the sense of a transmission ratio adjustment.

If the output signal of the torque detection device is a pressure of the hydraulic medium (as in the example described), a monitoring device can advantageously be provided, by means of which adaptation to the pressure of the hydraulic medium having a torque-independent effect can be avoided. The monitoring device can advantageously be included in the control device and can additionally include a correction device, by means of which torque-independent components of the pressure of the hydraulic medium can be corrected, so that a correct adaptation can be achieved.

The above-described embodiment of the method according to the invention is advantageous because the pressure P of the hydraulic medium at the output of the torque detection device_MFUnder certain operating conditions, this may be influenced by the return pressure occurring in components of the hydraulic system downstream of the torque detection device. A mathematical model of the return pressure can be implemented in the control device 24 so that the pressure P is equal to the pressure_MFThe return pressure may be taken into account when calculating the transmission torque. Only when the pressure P is_MFNot determined by the return pressure, but permitted by the pressure P_MFCalculating the actual torque T₁。

In the case of a transmission ratio different from the maximum possible transmission ratio, the adaptation can advantageously be carried out only if this transmission ratio can be calculated currently.

When the output signal is a hydraulic medium pressure, the adaptation is advantageously carried out when the transmission ratio of the transmission differs from the maximum possible transmission ratio only if the hydraulic medium pressure measured at a large clutch opening is lower than the value measured when the clutch is set at a given clutch torque. This ensures that: only when the pressure P considered for the calculation is being matched_MFAdaptation can only be carried out without or with only a small influence of the reflux pressure (rueckstaudrugk).

An apparatus for adapting the transmission torque of a clutch in an automated motor vehicle drive train, which drive train has a drive motor which is connected via the clutch to a transmission with a continuously variable transmission ratio, and a torque detection device for detecting an input torque of the transmission, which torque detection device produces output variables which are dependent on the torque and on the transmission ratio of the transmission, solves the problem associated with this, and comprises an electronic control device for controlling the clutch actuation device, in which control device a characteristic curve is stored which describes a given torque which can be transmitted by the clutch and is dependent on the control variable, which control device is designed for adapting the curve according to one of the methods described above.

The invention can be applied to different types of torque detecting devices and different types of speed change devices with continuously adjustable gear ratios.

Claims (10)

1. Method for adapting a relation between a torque transmittable by a clutch and a control variable controlling a clutch operating device stored in an electronic control device, the clutch being arranged in an automated motor vehicle drive train having a torque detection device arranged between the clutch and a transmission with a continuously variable transmission ratio for generating an output variable related to the detected torque and the instantaneous transmission ratio, in which method the torque transmitted by the clutch is calculated from the transmission ratio of the instantaneous transmission and the output variable value, and the transmitted torque is allocated as an updated transmittable torque to said control variable in an operating state of the clutch in which the clutch transmittable torque equals the transmitted torque.

2. Method according to claim 1, characterized in that the transmission ratio adapted thereto is the maximum possible transmission ratio of the transmission.

3. Method according to claim 2, characterized in that the adaptation is performed while the vehicle is stationary or creeping.

4. A method according to claim 2 or 3, characterized in that the transmission is a conical disc-wrap contact transmission, the driven side conical disc pair of which is loaded with increased pressure before and during fitting in order to press against the wrap contact.

5. A method according to claim 2 or 3, characterized by activating in a transmission control unit before the start of the adaptation and during the adaptation a transmission ratio set value corresponding to a transmission ratio larger than the maximum possible transmission ratio.

6. A method according to claim 2 or 3, characterized by activating an increased transmission given input speed in a transmission control unit before the start of adaptation and during adaptation.

7. Method according to claim 1, characterized in that the output signal is a pressure of the hydraulic medium and a monitoring device is provided, by means of which adaptation in the event of torque-independent influences on the pressure of the hydraulic medium can be avoided.

8. Method according to claim 1, characterized in that in the case of a transmission ratio different from the maximum possible ratio, the adaptation is only carried out if this ratio can be calculated currently.

9. Method according to claim 1 or 8, characterized in that the output signal is a pressure of the hydraulic medium and in the case of a transmission with a gear ratio different from the maximum possible gear ratio, the adaptation is performed only if the value of the output measured at a large opening of the clutch is lower than the value measured when the clutch is adjusted at a given clutch torque.

10. Device for adapting the transmittable torque of a clutch in an automated motor vehicle drive train, characterized in that the drive train has a drive engine connected via the clutch to a transmission with a steplessly variable transmission ratio and a torque detection device for detecting an input torque of the transmission, which torque detection device produces output quantities related to the torque and to the transmission ratio of the transmission, said adaptation device comprising an electronic control device for controlling the clutch operating device by a control quantity, in which control device a characteristic curve is stored, which characteristic curve gives a given torque transmittable by the clutch in relation to the control quantity, the control device being constructed and adapted to adapt the characteristic curve in accordance with the method according to one of claims 1 to 8.