A wet clutch pressure control method and apparatus

Abstract

The application provides a clutch target pressure control method and device. The method considers the differences of the clutch under various working conditions caused by centrifugal force, slip and clutch plate temperature, establishes a torque or pressure compensation method for the influencing factors, corrects the real torque request of the clutch, controls the pressure of the clutch under the current state, and finally obtains the target clutch torque, so that the clutch torque and the engine torque are matched, the workload of vehicle matching is reduced, the development cost is reduced, and the good and stable driving feeling of the driver is ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of automobile transmission control, and particularly relates to a pressure control method for torque transmission characteristics of a wet clutch. BACKGROUND

[0002] When a passenger car is working, the clutch in the transmission needs to cooperate with the engine torque to start, idle, shift gears, and travel, and the clutch torque control plays a crucial role in performing these actions. For example, a clutch pressure control device disclosed in patent document EP2233766B1 corrects the torque request of the actual clutch according to a slip signal and an oil temperature signal, and calculates the target torque of the clutch. However, according to the principle of clutch friction torque transmission characteristics, in actual application, the clutch in the working environment will be affected by multiple factors, and the compensation calculation limited to slip and oil temperature cannot completely predict the actual torque of the clutch. The applicant found that the engine speed, the speed difference between the front and rear ends of the clutch, and the temperature between the clutch plates all have a serious impact on the torque transmission characteristics of the clutch. The current application method on the market considers the clutch torque control very roughly, the torque transmission accuracy is poor, which leads to a large amount of vehicle matching work, high development cost, and poor vehicle drivability. SUMMARY

[0003] To solve the above technical problems, the present application provides a clutch target pressure control method based on clutch torque transmission characteristics. The method considers the differences caused by the centrifugal force, slip, and clutch plate temperature under various working conditions, establishes a torque or pressure compensation method for the influencing factors, corrects the actual torque request of the clutch, controls the pressure of the clutch under the current state, and finally obtains the target clutch torque, so that the clutch torque and the engine torque are matched appropriately, the amount of vehicle matching work is reduced, the development cost is reduced, and the driver's good and stable driving experience is ensured.

[0004] The technical solution adopted by the present application is as follows:

[0005] In a first aspect, the present application provides a clutch pressure control method based on clutch torque transmission characteristics, which comprises the following steps:

[0006] Step 1: preliminarily calculating the clutch torque request according to the current engine torque and working condition.

[0007] Step 2: calculating the clutch half-combination point torque at this time according to the current clutch slip speed, and calculating the clutch action pressure torque by comparing the clutch torque request, the calculation formula is as follows:

[0008] T kp =T adaption+ T (slip) ;

[0009] T apply = T request - T kp ;

[0010] Wherein, T kp : clutch half-engage point torque; T adaption : clutch half-engage point torque value under adaptive working condition; T (slip) : clutch half-engage point torque offset value affected by slip; T apply : clutch action torque.

[0011] Step 3, according to the input signal clutch last time torque, clutch front end speed, clutch rear end speed, clutch lubrication flow and cooling oil temperature calculation clutch current time slice temperature, according to the clutch current time slice temperature and current time correction pressure and clutch slip speed signal look-up table interpolation slice temperature compensation torque value; at the same time, according to the clutch correction pressure and clutch front and rear end speed difference look-up table interpolation slip compensation torque value, then the clutch action pressure torque and slice temperature compensation torque value and slip compensation torque value combination calculation clutch net torque, the calculation formula is as follows:

[0012] T pure = T apply + T temperature (temperature, pressure) + T slip (n slip , pressure) ;

[0013] Wherein, T pure : clutch net torque; T temperature (temperature, pressure): slice temperature compensation torque; T slip (n slip , pressure): slip compensation torque.

[0014] Step 4, using clutch net torque through clutch basic P-T curve look-up table interpolation to get the next time of clutch rough request pressure.

[0015] Step 5, according to the current time input shaft speed and current time clutch actual pressure look-up table interpolation to get the clutch centrifugal compensation pressure value, and then combined with the clutch rough request pressure to get the clutch pressure request P request， The calculation formula is as follows:

[0016] P centrifugal = w 2 *k(pressure, oil temperature)*r

[0017] P request =P centrifugal +P row

[0018] Here, w is the clutch input angular speed; k is a value related to the lubricating oil density; and r is a constant calculated from the clutch balance oil chamber geometry.

[0019] In a second aspect, the present invention further provides a clutch pressure control device, the device comprising the following functional modules:

[0020] The target torque calculation module is used to preliminarily calculate the clutch torque request based on the current engine torque and operating conditions.

[0021] The clutch half-engagement point torque module is used to calculate the clutch half-engagement point torque based on the current clutch slip speed. The calculation formula is as follows:

[0022] T kp =T adaption +T(slip).

[0023] The clutch pressure torque calculation module is used to calculate the clutch half-engagement point torque and the clutch torque request to obtain the clutch pressure torque. The calculation formula is as follows: apply =T request -T kp .

[0024] The clutch plate temperature calculation module is used to calculate the clutch plate temperature at the current moment based on the input signal clutch torque calculated at the previous moment, clutch front end speed, clutch rear end speed, clutch lubrication flow and cooling oil temperature.

[0025] The plate temperature compensation module is used to obtain the plate temperature compensation torque value by looking up and interpolating the clutch plate temperature at the current moment, the corrected pressure at the current moment, and the clutch slip speed signal.

[0026] The clutch slip compensation module is used to obtain the slip compensation torque value by looking up and interpolating the clutch correction pressure and the speed difference between the front and rear ends of the clutch.

[0027] The clutch net torque calculation module is used to combine the clutch pressure torque with the plate temperature compensation torque value and the slip compensation torque value to calculate the clutch net torque. The calculation formula is as follows:

[0028] T pure =T apply +T temperature (temperature,pressure)+T slip (n slip, pressure).

[0029] The clutch rough request pressure calculation module obtains the clutch rough request pressure at the next moment by using the clutch net torque to look up and interpolate the clutch basic P-T curve.

[0030] The clutch centrifugal compensation module is used to obtain the clutch centrifugal compensation pressure value by looking up and interpolating the input shaft speed at the current moment and the clutch actual pressure at the current moment.

[0031] The clutch pressure request calculation module is used to combine and calculate the clutch centrifugal compensation pressure value and the clutch rough request pressure to obtain the clutch pressure request P request , and the calculation formula is as follows:

[0032] P centrifugal = w 2 *k(pressure, oil temperature)*r

[0033] P request =P centrifugal +P row

[0034] Each of the above functional modules can be added in the vehicle transmission control TCU.

[0035] Specifically, the clutch slip speed is the difference between the front end speed of the clutch and the rear end speed of the clutch. The front end speed of the clutch includes but is not limited to an engine speed signal, a motor speed signal, a shaft speed signal, according to different power sources and arrangements. The rear end speed of the clutch includes but is not limited to a shaft speed signal, a differential speed signal, and a vehicle speed conversion signal, according to different structural arrangements. The clutch slip speed can be selected for filtering according to the calculation accuracy requirement.

[0036] Specifically, the clutch half-connection point torque calculation module can calculate the torque value of the clutch half-connection point by looking up and interpolating the basic torque of the current half-connection point and the clutch slip speed difference under the current working condition.

[0037] Specifically, the clutch pressure signal is the pressure in the clutch execution oil cavity, which can be directly measured by a sensor or calculated by different principles of an actuator, including but not limited to the characteristics of an electromagnetic valve and an electronic pump.

[0038] Specifically, the table used in the clutch plate temperature compensation module is a representation of the clutch plate temperature characteristics, which is obtained by analyzing the measured torque data of the clutch product.

[0039] Specifically, the table used in the clutch slip compensation module is a representation of the clutch slip characteristics, which is obtained by analyzing the measured characteristics of the clutch product.

[0040] The present application has the advantages of:

[0041] The present application considers the compensation calculation of clutch torque based on slip and oil temperature, and also fully considers the influence of engine speed, the speed difference between the front and rear ends of the clutch, and the temperature between the clutch plates on the torque transmission characteristics of the clutch. A method of targeted clutch pressure control according to the characteristics of the clutch under centrifugal force, slip speed, and temperature between the clutch plates is proposed. The method continuously detects the state of the clutch to compensate and control the pressure of the clutch. Compared with the traditional rough control method, the clutch torque accuracy of the present application is higher, the adaptability to multiple working conditions is stronger, and the calibration is easier, thereby reducing the labor cost of calibration and improving the drivability of the vehicle under corresponding working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 A logic flowchart showing the clutch pressure request obtained from the clutch torque request calculation process is shown.

[0043] Figure 2 A calculation logic diagram of the slip speed of the clutch is shown.

[0044] Figure 3 A calculation logic diagram of the clutch centrifugal correction pressure value is shown.

[0045] Figure 4 A calculation logic diagram of the clutch plate temperature compensation is shown.

[0046] Figure 5 A characteristic parameter table of clutch slip compensation is shown.

[0047] Figure 6 A characteristic parameter table of clutch plate temperature compensation is shown.

[0048] Figure 7 A clutch basic P-T curve is shown.

[0049] Figure 8 A curve diagram of the clutch torque and engine state under general vehicle working conditions according to the control method of the present application is shown. DETAILED DESCRIPTION

[0050] For the person skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application are described clearly and completely based on the drawings. Those skilled in the art can easily understand other advantages and effects of the present application from the disclosure of the present specification. The present application can also be implemented or applied by different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0051] The present application will be described below with reference to Figure 1 The clutch pressure control method based on the clutch torque transmission characteristics of the present application is described below in combination with specific examples. When the control method is implemented, the following functional modules are provided in the clutch pressure control device in the vehicle transmission control TCU: target torque calculation module, clutch half-engagement point torque module, clutch application pressure torque calculation module, clutch plate temperature calculation module, plate temperature compensation module, clutch slip compensation module, clutch net torque calculation module, clutch rough request pressure calculation module, clutch centrifugal compensation module, and clutch pressure request calculation module. The control process of the control method and device is described below with the example of soft accelerator idle start.

[0052] Step 1, the target torque calculation module calculates the torque request Cl2TorqueRequest of the clutch based on the current engine torque ENG_Nm_EngineTorque and the accelerator pedal EMS_AccPedal.

[0053] Step 2, the clutch half-engagement point torque calculation module calculates the clutch half-engagement point torque Torque_VKP_Cl2 at the current clutch slip speed SlipSpeed_Cl2, using the following formula:

[0054] T kp = T adaption + T(slip);

[0055] Wherein, T kp : clutch half-engagement point torque; T adaption : clutch half-engagement point torque value under adaptive working conditions; T (slip) : offset value of clutch half-engagement point torque affected by slip difference.

[0056] Then the clutch application pressure torque calculation module calculates the clutch application pressure torque T_Apply by using the clutch half-engagement point torque Torque_VKP_Cl2 and the clutch torque request Cl2TorqueRequest, using the following formula:

[0057] T apply =T request -T kp .

[0058] As Figure 2 shown in the calculation logic of the clutch slip speed, the above clutch slip speed is the difference between the engine speed EngineSpeed and the input shaft speed InputShaft2Spd. The clutch slip speed can be selected for filtering processing according to the calculation accuracy requirement.

[0059] Step 3, the clutch plate temperature calculation module calculates the clutch plate temperature Clutch2Temperature at the current time according to the input signals clutch torque at the last time, clutch front end speed ENG_rpm_Engine, clutch rear end speed InputShaft2Spd, clutch lubrication flow FlowRequest, and cooling oil temperature OilTemperature.

[0060] The plate temperature compensation module further obtains the plate temperature compensation torque value according to the clutch plate temperature at the current time, the pressure corrected at the current time (corrected by centrifugal compensation), and the clutch slip speed SlipSpeed_Cl2.

[0061] The calculation logic of the above clutch plate temperature compensation is shown in Figure 4 .

[0062] The table used here is a representation of the characteristics of the clutch plate temperature, which is obtained by analyzing the measured torque data of the clutch product. For example, the characteristic parameter table of the general clutch plate temperature compensation is shown in Figure 6 .

[0063] At the same stage, the clutch slip compensation module obtains the slip compensation torque value according to the clutch pressure corrected (i.e. the pressure corrected at the current time in the front) and the difference between the clutch front and rear end speeds, and the clutch acting pressure torque is combined with the plate temperature compensation torque value and the slip compensation torque value to obtain the clutch net torque TroquePure.

[0064] T pure =T apply +T temperature (temperature,pressure)+T slip (n slip ,pressure)。

[0065] T pure : clutch net torque; T temperature (temperature,pressure): plate temperature compensation torque; T slip(n slip , pressure): slip compensation torque.

[0066] Specifically, the table used here is a representation of the clutch slip characteristics, which is obtained from the measured characteristics of the clutch product. For example, a general clutch slip compensation characteristic parameter table is shown in Figure 5 .

[0067] Step 4: The clutch net torque is obtained by interpolating the clutch base P-T (pressure-torque) curve table at the next time point to obtain the clutch rough request pressure.

[0068] A general clutch base P-T curve is shown in Figure 7 , which is a linear relationship between clutch pressure and clutch torque.

[0069] Step 5: The clutch centrifugal compensation module obtains the clutch centrifugal compensation pressure value according to the input shaft speed at the current time and the clutch actual pressure (i.e. clutch pressure signal) at the current time, and then combines it with the clutch rough request pressure to calculate the clutch pressure request Cl2Demand. Subsequently, the clutch control module makes the real pressure Cl2Pressure follow the clutch pressure request Cl2Demand, realizes the rear-end speed Inputshaft2 to rise or drop, and thus controls the vehicle speed VehicleSpeed to increase or stop smoothly.

[0070] P centrifugal = w 2 *k(pressure, oil temperature)*r

[0071] P request =P centrifugal +P row

[0072] Here, w: clutch input angular speed; k: a value related to the density of lubricating oil. r: a constant calculated from the geometry of the clutch balance oil cavity.

[0073] The calculation logic of the clutch centrifugal compensation pressure value is shown in Figure 3 .

[0074] Above, the clutch pressure signal (i.e. the clutch actual pressure at the current time) is the pressure in the clutch actuator cavity, which can be directly measured by a sensor, or can be calculated through the principle of different actuators, including but not limited to through the electromagnetic valve characteristics, electronic pump characteristics.

[0075] It should be understood that, for those of ordinary skill in the art, various forms of the flow shown above can be used to reorder, add or delete steps. For example, the steps described in the present application can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in the present application can be achieved, and the present application does not limit here.

Claims

1. A clutch pressure control method, characterized in that: The control method comprises the following steps: Step 1: Preliminary calculation of clutch target torque request based on current engine torque and operating conditions; Step 2: Calculate the clutch half-engagement point torque based on the current clutch slip speed and add it to the clutch torque request to obtain the clutch applied torque. The calculation formula is as follows: ， ， Among them, T kp : Clutch half-engagement point torque; T adaption : half-engagement point torque value of the clutch under adaptive working conditions; T （slip） : The offset value of the clutch half-engagement point torque affected by slip; T apply : Clutch torque; Step 3: Calculate the clutch plate temperature at the current moment based on the input signal clutch torque at the previous moment, clutch front speed, clutch rear speed, clutch lubrication flow, and cooling oil temperature. Then, interpolate the plate temperature compensation torque value based on the clutch plate temperature at the current moment, the clutch corrected pressure, and the clutch slip speed signal. At the same time, interpolate the slip compensation torque value based on the clutch corrected pressure and the clutch front and rear speed difference. Then, combine the clutch torque with the plate temperature compensation torque value and the slip compensation torque value to calculate the clutch net torque. The calculation formula is as follows: ， Among them, T pure : Clutch net torque; T temperature (temperature, pressure): chip temperature compensation torque; T slip (n slip , pressure): slip compensation torque; Step 4: Use the clutch net torque to interpolate the clutch basic PT curve table to obtain the clutch rough request pressure P at the next moment. row ; Step 5: According to the current input shaft speed and the current actual clutch pressure, the clutch centrifugal compensation pressure value P is obtained by interpolation from the table. centrifugal , and then combined with the clutch rough request pressure to calculate the clutch pressure request P request， The calculation formula is as follows: ， P request =P centrifugal +P row , Here, w is the angular speed of the clutch input end, k is a value related to the density of the lubricating oil, and r is a constant calculated from the geometric dimensions of the clutch balance oil chamber.

2. The clutch pressure control method according to claim 1, characterized in that: The clutch slip rotation speed is the difference between the clutch front end rotation speed and the clutch rear end rotation speed.

3. The clutch pressure control method according to claim 1, characterized in that: The front end speed of the clutch includes an engine speed signal, a motor speed signal, and a shaft speed signal; the rear end speed of the clutch includes a shaft speed signal, a differential speed signal, and a vehicle speed conversion signal.

4. The clutch pressure control method according to claim 1, characterized in that: The clutch half-engagement point torque is calculated by interpolation based on the base torque of the current half-engagement point and the clutch slip rotational speed difference under the current working condition.

5. The clutch pressure control method according to claim 1, characterized in that: The actual clutch pressure at the current moment is the pressure in the clutch execution oil chamber, which is measured by a sensor or calculated based on the characteristics of the solenoid valve and the electronic pump.

6. The clutch pressure control method according to claim 1, characterized in that: The table used in clutch plate temperature compensation is a representation of the clutch plate temperature characteristics and is obtained by analyzing the measured torque data of the clutch product.

7. The clutch pressure control method according to claim 1, characterized in that: The table used in clutch slip compensation is a representation of the clutch slip characteristics, which is obtained from the actual measured characteristics of the clutch product.

8. A clutch pressure control device, characterized in that: include: a target torque calculation module, configured to preliminarily calculate a clutch target torque request based on the current engine torque and operating conditions; The clutch half-engagement point torque module is used to calculate the clutch half-engagement point torque based on the current clutch slip speed. The calculation formula is as follows: ； Among them, T kp : Clutch half-engagement point torque; T adaption : half-engagement point torque value of the clutch under adaptive working conditions; T （slip） : The offset value of the torque at the clutch half-engagement point affected by slip; The clutch pressure torque calculation module is used to calculate the clutch half-engagement point torque and the clutch torque request to obtain the clutch pressure torque. The calculation formula is as follows: ; where T apply : Clutch torque; The clutch plate temperature calculation module is used to calculate the clutch plate temperature at the current moment based on the input signal clutch torque calculated at the previous moment, clutch front end speed, clutch rear end speed, clutch lubrication flow and cooling oil temperature; The plate temperature compensation module is used to interpolate the plate temperature compensation torque value based on the current plate temperature of the clutch, the corrected pressure at the current moment, and the clutch slip speed signal; The clutch slip compensation module is used to interpolate the slip compensation torque value based on the clutch correction pressure and the speed difference between the front and rear ends of the clutch; The clutch net torque calculation module is used to combine the clutch pressure torque with the plate temperature compensation torque value and the slip compensation torque value to calculate the clutch net torque. The calculation formula is as follows: ， Among them, T pure : Clutch net torque; T temperature (temperature, pressure): chip temperature compensation torque; T slip (n slip , pressure): slip compensation torque; The clutch rough request pressure calculation module uses the clutch net torque to interpolate the clutch basic PT curve table to obtain the clutch rough request pressure at the next moment; The clutch centrifugal compensation module is used to obtain the clutch centrifugal compensation pressure value by looking up and interpolating the table according to the current input shaft speed and the current actual clutch pressure; The clutch pressure request calculation module is used to calculate the clutch pressure request P by combining the clutch centrifugal compensation pressure value and the clutch roughness request pressure. request， The calculation formula is as follows: ， P request =P centrifugal +P row , Here, w is the clutch input angular speed, k is a value related to the lubricating oil density, and r is a constant calculated from the geometric dimensions of the clutch balancing oil chamber.

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