Procedure for calibrating a clutch control

Abstract

The present invention relates to a method for calibrating a clutch control of a drive train of a motor vehicle. The drive train has an electric motor (14). An output of the drive train is blocked (32) and the motor (14) is operated (36) with a value for a first operating variable. The clutch is then actuated (54, 66) with a first value for a clutch control variable, and a first value of a second operating variable of the motor (14) is detected. The clutch is also actuated (64) with a second value for the clutch control variable, and a second value of the second operating variable of the motor (14) is detected. Clutch characteristics are determined as a function of the detected first value and the detected second value of the second operating variable.

Description

Technical FieldThe present invention relates to a method for calibrating a clutch control of a drive train of a motor vehicle, wherein the drive train has an engine designed as an electric motor.Prior ArtCalibration routines are used to optimize control of vehicle transmissions, for example, to compensate for component and manufacturing tolerances. This is intended to compensate, for example, for different clutches of the same series being able to transmit completely different torques in the case of an actuation of the same type. Due to respective tolerances, the clutches can otherwise close to different extents with the same control. However, an actual contact pressure is usually not detected at the clutch, since its measurement is very complicated. In motor vehicles, the sensors necessary for this purpose are usually not installed at all. Instead, for example, only a fill compensation pressure is determined for calibration. For this purpose, a clutch is actuated at different pressure levels and, on the basis of a detected rotational speed, it is determined from when the clutch begins to transmit a torque which is greater than a drag torque. The thus determined relationship between an activation of the clutch and the transmittable torque is, however, low. In addition, calibration can thus be carried out, for example, only with a single operating point.Alternatively, the calibration can also be carried out on a test stand directly after the production of the clutch or of a transmission. However, such a calibration is already complicated and expensive per se. In addition, recalibration can then take place only at the factory, for example during maintenance of the motor vehicle. Thus, for example, it is not possible to react to aging of a clutch oil with renewed calibration by the motor vehicle itself.SUMMARY OF THE INVENTIONA first aspect relates to a method for calibrating a clutch control of a drive train. The calibration may involve a change in control parameters of one or more clutches of the powertrain. The drive train has at least one clutch. The clutch can be designed, for example, as a multiplate clutch. The coupling can be effected, for example, by means of an electrohydraulic pressure regulating valve. By energizing the pressure regulating valve, an actuation pressure of the clutch proportional thereto can be adjusted. Depending on manufacturing tolerances, for example, a proportional relationship between energization and actuation pressure may be different in the case of clutches of the same type. The drive train can be designed to generate and transmit a driving force for a motor vehicle. The drive train has a motor designed as an electric motor. The electric motor can be designed, for example, as a synchronous machine or an asynchronous machine. The motor may be, for example, a traction motor of the motor vehicle. The motor vehicle can be designed, for example, as a passenger car, construction machine or agricultural machine.The method includes blocking an output of the powertrain. The output can be, for example, a driven axle or an output shaft of a transmission of the drive train. The blocking can take place, for example, by means of a parking brake or a service brake. If a plurality of clutches are present, complete closing of all clutches in the power flow from the engine to the output can additionally take place, which are not to be calibrated. These couplings can be printed on at maximum, for example, and thus provide a connection that is almost fixed against relative rotation.The method includes operating the engine with a value for a first operating variable. The value may be, for example, a predetermined value. The operating variable can be, for example, a power, a rotational speed or a torque of the motor. In an electric motor, respective operating variables can be detected and predefined with high quality. For example, in an electric motor, a torque can be set with high accuracy and can also be held at different loads. The torque of the electric motor can be present, for example, as a measured variable in an inverter of the drive train. As a result, no additional sensors are necessary. The operating variable can be transmitted, for example, in a data bus of the motor vehicle, such as a CAN bus, to an ECU, such as a transmission ECU. For carrying out the calibration method, structural adaptation of the drive train and additional elements, which are not required in regular clutch operation or driving operation, may thus be unnecessary.The method includes actuating the clutch with a first value for a clutch manipulated variable. The clutch can be actuated, for example, while the engine is operated with the value for the operating variable. The clutch manipulated variable may be a control variable with which the clutch is actuated. For example, the clutch control variable can be a voltage or a current flow with which the pressure regulating valve of the clutch is energized. By the actuation, the clutch is actuated with a pressure corresponding to the first value. Accordingly, the clutch is then partially closed, for example. The clutch can then transmit, for example, a torque corresponding to the first value for the clutch manipulated variable.The method includes detecting a first value of a second operating variable of the engine upon actuation of the clutch at the first value. The second operation amount may be an amount corresponding to a performance of the engine, which is different from the first operation amount. As a result, it is possible to infer a state of the clutch during the actuation with the first value of the clutch manipulated variable. The state can be, for example, a transmittable torque which corresponds to the first value of the clutch manipulated variable. The detection can be carried out, for example, by means of the drive train. For example, a torque can be detected by means of the motor and alternatively or additionally the inverter, which is required to maintain the predetermined rotational speed. Due to the blocked output of the drive train, this torque corresponds to the transmittable torque of the clutch, optionally minus respective drag torques in the drive train. Alternatively, for example, a rotational speed can be detected which is established by the motor at a predefined torque. Overall, an actuation degree of the clutch can thus be determined.The method includes actuating the clutch with a second value for the clutch manipulated variable. The second value of the clutch manipulated variable differs from the first value. The second value of the clutch manipulated variable may be greater than the first value, for example. The method includes detecting a second value of the second operating variable of the engine upon actuation of the clutch at the second value. Thus, a second operating point of the clutch may be determined. Even when the clutch is actuated with the second value of the clutch manipulated variable and the second value of the second operating variable of the engine is detected, the output of the drive train can be blocked and the engine can be operated with the value for its first operating variable.Optionally, further operating points can also be taken into account for calibration. For this purpose, the clutch can be actuated, for example, with a third value and optionally further values for the clutch manipulated variable. To this end, a third value and optionally further values for the second operating variable of the engine can then be correspondingly detected during the corresponding actuation of the clutch.Optionally, the method can be repeated at different values for the first operating variable. For example, transmittable torques may be determined at a first level of engine speed and at a second level of engine speed different therefrom. As a result, additional operating points can be determined and further data can be generated and taken into account for calibration. In addition, different clutch control parameters or clutch control characteristic lines can thus be calibrated for different rotational speeds.The method comprises ascertaining clutch characteristic data as a function of the detected first value and the detected second value of the second operating variable. These clutch characteristics can be used for calibrating the clutch control. For example, by interpolating and, if more than two operating points are determined, a relationship between the clutch manipulated variable and the transmittable torque of the clutch can be determined by a compensation curve. This relationship can be stored and used for clutch control, for example by a transmission control. The clutch characteristics can accordingly have a characteristic curve. For example, a clutch control characteristic curve can be changed depending on the determined clutch characteristic data. For ascertaining clutch characteristic data, further characteristic variables can optionally be taken into account, such as the value for the first operating variable of the engine, the first value for the clutch manipulated variable and the second value for the clutch manipulated variable.In a further embodiment of the method, it can be provided that the first operating variable is a rotational speed of the motor and the second operating variable is a torque of the motor. The motor can thus be speed-controlled at least during calibration. For example, a transmittable torque through the clutch may be ascertained on the basis of a current flow necessary for maintaining the rotational speed of the engine. The calibration can thus be particularly simple and accurate.In a further embodiment of the method, it can be provided that the first operating variable is a torque of the motor and the second operating variable is a rotational speed of the motor. The motor can thus be torque-controlled at least during calibration. Thus, overloading of the clutch can be reliably avoided during calibration.In a further embodiment of the method, it can be provided that during the actuation of the clutch, respective values for the clutch manipulated variable are regulated in order to achieve respective predefined target variables for the second operating variable. Thus, instead of measuring, for example, the torque which is necessary to maintain a predefined rotational speed at a predefined value for the clutch manipulated variable, the clutch manipulated variable is controlled in order, for example, to achieve a predefined torque for the motor at a predefined rotational speed. Such a calibration method can cause a particularly low load for the motor. For example, this regulation can be used only for one value, such as the first value or the second value, of the clutch manipulated variable. However, this regulation can also be used for a plurality of or all values for the clutch manipulated variable.In a further embodiment of the method, it can be provided that a rapid filling of the clutch takes place before the clutch is actuated with one of the respective values for the clutch manipulated variable. A rapid filling can be a filling of a hydraulic actuator of the clutch before an actual actuation. This allows the actuator to be vented. During rapid filling, the pressure regulating valve can be opened particularly widely, for example. The rapid filling can allow a particularly rapid calibration. Moreover, standardized actuation methods which are also used in normal operation can thus be used for actuating the clutch during calibration. A time duration for the rapid filling can be permanently predefined, for example, or can be determined within the scope of the calibration method. The rapid filling can take place before each actuation of the coupling during the calibration process or else only during some of the actuations. After the rapid filling, a piston of the clutch may not yet abut, for example, plates of the clutch and alternatively or additionally a fan clearance may not yet be eliminated.In a further embodiment of the method, it can be provided that before actuating the clutch with one of the respective values for the clutch manipulated variable, a fill compensation of the clutch takes place. As a result, remaining residual oil quantities in the actuator of the clutch can be taken into account, for example. The fill compensation can be a filling of a hydraulic actuator of the clutch before an actual actuation and after the rapid filling. A time duration can also be predefined for the fill compensation. During the filling compensation, the pressure regulating valve can be opened to a lesser extent than during the rapid filling, for example, in order to avoid unintentional actuation and the beginning of friction during the clutch. After the fill compensation, a clutch piston can abut at a minimum clutch torque. The blocking of the output drive can take place, for example, only after the first filling compensation.In a further embodiment of the method, it can be provided that the clutch is actuated a first time with the first value for the clutch manipulated variable starting from a less strongly actuated clutch and a second time with the first value for the clutch manipulated variable starting from a more strongly actuated clutch. The first value can be smaller than the second value and the clutch is thus actuated to a lesser extent. For example, the clutch may be actuated the first time after a fill compensation with the first value and the second time after actuation of the clutch with the second value of the clutch manipulated variable. As a result, hysteresis can be detected during calibration, wherein only three instead of four measurements of operating points may be necessary. Depending on whether the clutch is adjusted in the direction of its open position or closed position, the relationship between the manipulated variable and the torque transmittable at the clutch may be different. Accordingly, the relationship can thus be determined with little effort for both adjustment directions. Two corresponding characteristic curves can then be determined or, for example, a characteristic curve with hysteresis loop.In a further embodiment of the method, it may be provided that the method has a step of detecting a further value of the second operating variable of the engine when the clutch is not actuated. As a result, for example, a drag torque can be determined. The drag torque can be caused by friction in the drive train and alternatively or additionally a minimum torque transmission when the clutch is fully open. The drag torque corresponds, for example, to no transmittable torque at the clutch and can be calculated, for example, for the clutch control. The clutch characteristic data can be ascertained as a function of the detected further value of the second operating variable. For example, the further value can be subtracted from the other detected values of the second operating variable in order to determine the torque which can be transmitted by the clutch. Respective characteristic curves for the clutch control can thus be offset or corrected by the drag torque.In a further embodiment of the method, it can be provided that the method has a step of changing a clutch control as a function of the determined clutch characteristic data. For example, respective control parameters and alternatively or additionally control characteristic curves of the clutch control can be changed. For example, the clutch control can thus be calibrated once when the motor vehicle is put into operation. However, an adaptation of the clutch control over the lifetime can also take place. For example, the method for calibration can be carried out periodically. The calibration can take place, for example, after a predefined driving power, after a predefined time or at each vehicle start.In a further embodiment of the method, it can be provided that the coupling is monitored using the calibration method. For this purpose, the clutch characteristic data determined can be compared with previously determined clutch characteristic data or desired clutch characteristic data. In the case of deviations greater than a threshold value, an output can take place, for example as an error message. This may signal to the user, for example, a need for clutch maintenance. For example, clutch wear can also be determined on the basis of the determined clutch characteristic data or a change in determined clutch characteristic data.In a further embodiment of the method, it can be provided that the clutch characteristics have a relationship between the clutch manipulated variable and a torque that can be transmitted by the clutch. The clutch can thus be controlled according to the desired transmittable torques.In a further embodiment of the method, it can be provided that the clutch characteristics have a coefficient of friction. For example, the calibration method can be used to determine which coefficient of friction the clutch currently has. As a result, changes in the clutch oil and on clutch friction linings can be taken into account.In a further embodiment of the method, it can be provided that the clutch characteristics have a clutch hysteresis. As a result, the clutch control can be calibrated in a manner adapted to the adjustment direction of the clutch.In a further embodiment of the method, it can be provided that the clutch characteristics have a clutch wear characteristic value. The clutch wear characteristic value can be proportional to the transmittable torque, for example, and can be calculated as a percentage deviation from a setpoint value. The clutch wear characteristic value can be determined, for example, on the basis of an average deviation in all determined operating points during the calibration or on the basis of a highest deviation in all determined operating points.In a further embodiment of the method, it can be provided that the method further comprises a step of detecting a clutch temperature and the determination of clutch characteristic data takes place as a function of the detected clutch temperature. As a result, it can be taken into account during the calibration that the clutch temperature has a great influence on the friction in the clutch and thus on the transmittable torque. In addition, the calibration and also the clutch control can thus also take place as a function of temperature. The clutch temperature may be, for example, a friction lining temperature or an oil temperature in the clutch.A second aspect relates to a transmission control device which is designed to carry out the method according to the first aspect. Respective further features, embodiments and advantages can be gathered from the descriptions of the first aspect. Conversely, features, embodiments and advantages of the second aspect also represent features, embodiments and advantages of the first aspect. The transmission control unit may be designed to actuate respective clutches of a motor vehicle. The transmission control unit may be designed to transmit respective control signals to a clutch actuator, to an engine control unit of the motor vehicle and to a brake system of the motor vehicle. The transmission control unit can thus, for example, block the output of the drive train of the motor vehicle, specify a value for the first operating variable of the engine and specify a value for the clutch control variable for the actuation of the clutch. In addition, the transmission control unit may be designed to receive state signals from the engine control unit. For example, currently detected values of the second operating variable of the engine can thus be transmitted to the transmission control unit. In addition, the transmission control unit can be designed to ascertain clutch characteristic data as a function of the detected first value and the detected second value of the second operating variable.A third aspect relates to a system which is designed to carry out the method according to the first aspect. Respective further features, embodiments and advantages can be gathered from the descriptions of the first aspect. Conversely, features, embodiments and advantages of the third aspect also represent features, embodiments and advantages of the first aspect.Brief Description of the FiguresFIG. 1 schematically shows a system by means of which a clutch control of a drive train of a motor vehicle can be calibrated. FIG. 2 schematically illustrates a method for determining an operating point during the calibration of the clutch control. FIG. 3 is a diagram illustrating actuation of a clutch to calibrate control thereof.Detailed Description of EmbodimentsFIG. 1 shows a system 10 which is designed for calibrating a clutch control of a drive train of a motor vehicle. The system 10 includes a brake 12 configured to block an output of the powertrain. The system 10 comprises an engine 14 designed as an electric motor and a transmission 16 which is designed to transmit a driving force from the engine 14 to the output. In the example shown, the transmission 16 has only one clutch, which in the example shown is designed as a multiplate clutch. The system 10 includes an inverter 18 that controls a power supply of the motor 14 through a power source 20. Inverter 18 is also designed to detect respective uncontrolled operating variables of motor 14. In addition, the system 10 has a transmission control unit 22 designed as an ECU. The transmission controller 22 is configured to control the clutch of the transmission 16 by adjusting a current flow for a pressure regulating valve. In addition, in one specific embodiment, transmission control unit 22 is designed to record a clutch temperature. In addition, the transmission control unit 22 can specify a setpoint value for a motor rotational speed to the inverter 18 and alternatively or additionally a motor torque. Additionally, the transmission controller 22 may receive a current value of engine speed from the inverter 18 and alternatively or additionally engine torque.In the example shown, the motor 14 is speed controlled. The inverter 18 thus provides the motor 14 with a value for a rotational speed as a first operating variable and, for this purpose, correspondingly regulates the power supply. From the necessary power supply, the inverter 18 derives a value of the motor torque as a second operating variable. If the engine 14 is operated at a fixed rotational speed, which is specified by the transmission control unit 22 during a calibration, and the brake 12 blocks the output, the detected engine torque thus corresponds to a torque that can be transmitted by the clutch in the transmission 16.FIG. 2 illustrates a method for determining an operating point during a calibration of a clutch control of the clutch of the transmission 16. In a step 32, the output is blocked by means of the brake 12. In a step 34, a calibration of a rapid filling and a filling compensation takes place. Due to the rapid filling and the filling compensation, a piston of the clutch can be brought into contact with plates, while the clutch is still fully open. In a step 36, a fixed setpoint rotational speed for the engine 14 is predefined by the transmission control unit 22. In response, inverter 18 controls a power supply so that motor 14 maintains this target speed. In a step 38, the motor torque generated in this case is detected by the inverter 18 and transmitted to the transmission control unit 22. This determined engine torque corresponds to a drag torque when the clutch is open. In a step 40, the clutch having a value for a clutch manipulated variable is controlled by the transmission control unit 22 in order to correspondingly actuate the clutch. The torque generated by the motor 14 upon the clutch actuation with the value of the clutch manipulated variable is also detected. This results in a corresponding operating point at which the torque that can be transmitted by the clutch corresponding to a value of the clutch manipulated variable has been detected. Step 40 can be repeated several times in order to determine corresponding data for further operating points. Respective data thus collected are used in a step 42 for ascertaining clutch characteristic data. In a simple embodiment, the data of two operating points are used to generate a straight line as a clutch control characteristic. The clutch characteristic data determined or clutch control calibrated therewith is stored in a step 44 by the transmission control unit 22.FIG. 3 is a diagram illustrating an embodiment for actuating the clutch or energizing the pressure regulating valve to actuate the clutch for calibrating the clutch control. The current flow in mA is plotted on the ordinate. The abscissa represents a time course in seconds.During calibration, the engine 14 is operated with a predetermined value for the engine speed as the first operating variable. In the region 48, the clutch is opened and the output is blocked by the brake 12. The drag torque is determined. In a region 50, a first rapid filling takes place and in a region 52, a filling compensation takes place. Subsequently, the clutch is actuated in a region 54 with a first value for the clutch control variable, i.e. a specific level of current flow through the pressure regulating valve. The torque required to hold the predetermined value for the engine speed is detected as a first value for the second operation amount of the engine 14. Subsequently, in a region 56, the clutch is energized again with the value of the clutch control variable for the filling compensation and the clutch is thus opened again. A piston of the clutch remains in contact with the plates. The torque required to maintain the predetermined value for engine speed is, in one embodiment, detected as the value for the second operating amount of the engine 14 to determine a point of hysteresis of the clutch control.Subsequently, in a region 58, a complete emptying of an actuator of the clutch and a waiting time take place. Thereafter, a rapid filling takes place again in a region 60 and a filling compensation takes place in a region 62. Subsequently, the clutch is actuated in a range 64 with a second value for the clutch manipulated variable, which is greater than the first value of the clutch manipulated variable. The torque required to hold the predetermined value for the engine speed is detected as a second value for the second operation amount of the engine 14. Subsequently, in a region 66, the clutch is actuated again with the first value of the clutch control variable and the clutch is thus easily opened again. The torque required to maintain the predetermined value for engine speed is, in one embodiment, detected as another value for the second operating amount of the engine 14 to determine another point of hysteresis of the clutch control. Subsequently, in a region 68, the clutch is energized again with the value of the clutch control variable for the filling compensation and the clutch is thus fully opened again. A piston of the clutch remains in contact with the plates. The torque required to maintain the predetermined value for engine speed is, in one embodiment, detected as the value for the second operating amount of the engine 14 to determine another point of hysteresis of the clutch control.Subsequently, in a region 70, a complete emptying of an actuator of the clutch takes place. The measurements for calibration are then completed in one embodiment. In another embodiment, a waiting time takes place and then further operating points are determined at a different rotational speed level. After the waiting time, the engine 14 is operated with a different predetermined value for the engine speed as the first operating variable and the previously described ranges 50 to 68 are passed through again. This is repeated for a plurality of different rotational speed levels in one embodiment.Reference numerals denote reference numerals10 System 12 Brake 14 Motor 16 Transmission 18 Inverter 20 Energy source 22 Transmission control unit 30 Step Activation Calibration 32 Step Output blocking 34 Step Calibration Rapid filling and filling compensation 36 Step Presetting of a fixed setpoint rotational speed 38 Step Transmission Motor torque to Transmission control unit 40 Step Control Clutch with value 42 Step Ascertaining Clutch characteristic data 44 Step Storage Clutch characteristic data 48 Clutch open, Output blocked 50 Region First rapid filling 52 Region Filling compensation 54 Region Actuation Clutch with first value 56 Region Opening Clutch 58 Region Complete emptying Actuator, including. Waiting time 60 Region of renewed rapid filling 62 Region of filling compensation 64 Region of actuation of clutch with second value 66 Region of actuation of clutch with first value 68 Region of complete opening of clutch 70 Region of complete emptying of actuator

Claims

Method for calibrating a clutch control of a drive train of a motor vehicle, wherein the drive train has an engine (14) designed as an electric motor, and wherein the method has at least the following steps: - blocking (32) an output of the drive train; - operating (36) the engine (14) with a value for a first operating variable; - actuating (54, 66) the clutch with a first value for a clutch manipulated variable; - detecting a first value of a second operating variable of the engine (14) when actuating the clutch with the first value; - actuating (64) the clutch with a second value for the clutch manipulated variable; - detecting a second value of the second operating variable of the engine (14) when actuating the clutch with the second value; and - determining (42) clutch characteristic data as a function of the detected first value and the detected second value of the second operating variable.Method according to Claim 1, characterized in that the first operating variable is a rotational speed of the motor (14) and the second operating variable is a torque of the motor (14).Method according to Claim 1, characterized in that the first operating variable is a torque of the motor (14) and the second operating variable is a rotational speed of the motor (14).Method according to one of the preceding claims, characterized in that, when the clutch is actuated, respective values for the clutch manipulated variable are regulated in order to achieve respective predefined target variables for the second operating variable.Method according to one of the preceding claims, characterized in that rapid filling (50, 60) of the clutch takes place before the clutch is actuated with one of the respective values for the clutch manipulated variable.Method according to one of the preceding claims, characterized in that before the clutch is actuated with one of the respective values for the clutch manipulated variable, the clutch is compensated for fill (52, 62).Method according to one of the preceding claims, characterized in that the clutch is actuated a first time with the first value for the clutch manipulated variable starting from a less strongly actuated clutch and a second time with the first value for the clutch manipulated variable starting from a more strongly actuated clutch.Method according to one of the preceding claims, characterized in that the method has a step of detecting a further value of the second operating variable of the engine (14) when the clutch is not actuated, and clutch characteristic data are ascertained as a function of the detected further value of the second operating variable.Method according to one of the preceding claims, characterized in that the method has a step of changing a clutch control as a function of the clutch characteristic data determined.Method according to one of the preceding claims, characterized in that the coupling is monitored by the calibration method.Method according to one of the preceding claims, characterized in that the clutch characteristic data have at least one of the following data: - a relationship between the clutch control variable and a torque which can be transmitted by the clutch; - a coefficient of friction; - a clutch hysteresis; and - a clutch wear characteristic value.Method according to one of the preceding claims, characterized in that the method further comprises a step of detecting a clutch temperature and clutch characteristic data is determined as a function of the detected clutch temperature.

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