A method and system for controlling the oil pressure of a power shift transmission clutch

Abstract

The present invention discloses a method and system for controlling the oil pressure of a power shift transmission clutch, belonging to the technical field of automatic transmissions. The method includes obtaining the engine speed, and calculating the corrected turbine torque in combination with preset hydraulic torque converter parameters and the dynamic characteristics of the torque converter; obtaining the current throttle pedal position, calculating the target value of the turbine angular acceleration, and performing dynamic correction to obtain the corrected dynamic target value of the turbine angular acceleration; calculating the feedforward target oil pressure according to the calculated turbine torque and the dynamic target value of the turbine angular acceleration; calculating the feedback target oil pressure according to the actual value of the turbine angular acceleration and the corrected dynamic target value of the turbine angular acceleration; calculating the target oil pressure of the clutch according to the feedforward target oil pressure and the feedback target oil pressure, and converting it into a control signal to be sent to the solenoid valve. The present invention can control the shift time, reduce the shift shock degree, improve the driving comfort, and at the same time improve the working efficiency of the hydraulic system during the shifting process.

Description

Technical Field

[0001] The present invention relates to a method and system for controlling the oil pressure of a clutch in a power shift transmission, belonging to the technical field of automatic transmissions. Background Art

[0002] The wet multi-plate clutch is an important component of the power shift transmission. Through the mutual cooperation of multiple clutches in the transmission, functions such as starting, shifting gears, and reversing of engineering vehicles can be realized. The engagement and separation of the clutch are achieved by the electronic control hydraulic system of the transmission. When engaging, the hydraulic oil enters the oil cylinder through the oil filling channel, pushing the piston to press the driving and driven disks of the clutch to achieve torque transmission; when separating, the hydraulic oil returns to the main fuel tank, the pressure in the oil cylinder drops, and the piston returns to the starting position under the push of the return spring, and the torque transmission is interrupted.

[0003] The existing method for controlling the oil pressure of the clutch in a power shift transmission usually adopts a segmented oil pressure control strategy, dividing the power shift process into 4 stages: the original gear position, the torque phase, the inertia phase, and the new gear position. This control method can achieve a better balance among the shift time, the shift shock degree, and the slip friction work, but whether the oil pressure strategies for each stage are reasonable depends to a large extent on engineering experience. Moreover, the existing method has poor adaptability to different working conditions, different vehicle models, and the wear of components in the transmission system, and cannot adjust itself according to the actual conditions of the vehicle. It requires engineers to debug according to engineering experience, increasing the consumption of manpower and material resources. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method and system for controlling the oil pressure of a clutch in a power shift transmission, which can control the shift time, reduce the shift shock degree, improve driving comfort, and at the same time improve the working efficiency of the hydraulic system during the shift process.

[0005] To achieve the above purpose, the present invention is implemented by the following technical solutions:

[0006] In the first aspect, the present invention provides a method for controlling the oil pressure of a clutch in a power shift transmission, including:

[0007] Obtain the engine speed, and calculate the corrected turbine torque by combining the preset parameters of the torque converter and the dynamic characteristics of the torque converter;

[0008] Obtain the current throttle pedal position, calculate the target value of the turbine angular acceleration, and perform dynamic correction to obtain the corrected dynamic target value of the turbine angular acceleration;

[0009] Calculate the feedforward target oil pressure according to the calculated turbine torque and the dynamic target value of the turbine angular acceleration;

[0010] Calculate the feedback target oil pressure based on the actually obtained turbine angular acceleration value and the corrected dynamic turbine angular acceleration target value.

[0011] Calculate the clutch target oil pressure based on the feedforward target oil pressure and the feedback target oil pressure, and convert it into a control signal to be sent to the solenoid valve. Control the clutch oil pressure through the solenoid valve to achieve the gear shifting operation of the transmission.

[0012] Furthermore, obtain the engine speed, and calculate the corrected turbine torque in combination with the preset torque converter parameters and the dynamic characteristics of the torque converter. The formula is as follows:

[0013] (1);

[0014] Where, is the engine speed, is the pump impeller speed, is the pump impeller speed, is the turbine torque, is the pump impeller torque, is the corrected pump impeller torque, is the torque converter speed ratio, is the torque converter torque ratio, is the density of the working medium oil, is the acceleration due to gravity, is the effective diameter of the circulating circle, is the pump impeller torque coefficient.

[0015] Furthermore, obtain the current throttle pedal position, calculate the turbine angular acceleration target value, and perform dynamic correction. The dynamic correction formula is as follows:

[0016] (2);

[0017] Where, is the corrected dynamic turbine angular acceleration target value, is the turbine angular acceleration target value, is the period of the trigonometric function, is the current gear shifting time, is the moment when the corrected dynamic turbine angular acceleration target value starts to decline.

[0018] Furthermore, during the oil pressure control process, the oil pressure starts to rise from 0, reaches the target value at , starts to decline at , and returns to 0 at . At this moment, the rotational speed difference between the driving and driven disks has been eliminated.

[0019] Further, the change process of the dynamic turbine angular acceleration target value is fitted according to Formula (2), and when a preset condition is satisfied, the dynamic turbine angular acceleration target value smoothly transitions from a preset initial value to 0.

[0020] Further, the preset condition is: the rotational speed difference between the theoretical turbine rotational speed value when shifting into the target gear at the current vehicle speed calculated based on the current transmission output shaft rotational speed, the target gear, and the preset transmission ratios of each gear, and the current turbine rotational speed is equal to or less than a preset target rotational speed difference.

[0021] Further, the preset target rotational speed difference is calculated by Formula (3):

[0022] (3)

[0023] wherein, is the rotational speed difference between the current turbine rotational speed and the target turbine rotational speed, is the current turbine rotational speed, is the transmission output shaft rotational speed, is the transmission ratio of the target gear.

[0024] Further, the feedforward target oil pressure is calculated based on the calculated turbine torque and the dynamic turbine angular acceleration target value, and the formula is as follows:

[0025] (4);

[0026] wherein, is the feedforward target oil pressure, is the moment of inertia at the transmission input end, is the number of clutch friction pairs, is the friction coefficient of the friction pair, is the acting radius of the clutch transmission torque, is the piston acting area, is the return spring force.

[0027] In a second aspect, the present invention provides a power shift transmission clutch oil pressure control system, which adopts the power shift transmission clutch oil pressure control method described in any one of the foregoing items. The system includes: an engine, a torque converter, a transmission, a drive wheel, a clutch, a solenoid valve, a throttle position sensor, a first rotational speed sensor, a second rotational speed sensor, an engine control unit, and a transmission control unit. The first rotational speed sensor is installed on the torque converter, and the second rotational speed sensor is installed on the output shaft of the transmission, wherein:

[0028] The engine control unit receives the engine speed and sends it to the transmission control unit. The first speed sensor sends the measured pump impeller speed and turbine speed to the transmission control unit. The second speed sensor sends the measured transmission output shaft speed to the transmission control unit. After receiving the data from the engine control unit, the first speed sensor, and the second speed sensor, the transmission control unit calculates the target clutch oil pressure according to the internally preset parameters and sends a control signal to the solenoid valve. The solenoid valve controls the clutch oil pressure to achieve the shifting action of the transmission.

[0029] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0030] The present invention provides a method and system for controlling the clutch oil pressure of a power shift transmission. By calculating the target clutch oil pressure and sending a control signal to the solenoid valve to control the clutch oil pressure, the shifting action of the vehicle transmission can be achieved. The shifting time can be controlled, the shifting shock can be reduced, the driving comfort can be improved, and at the same time, the working efficiency of the hydraulic system during the shifting process can be improved. Description of the Drawings

[0031] Figure 1 It is a flowchart of a method for controlling the clutch oil pressure provided by an embodiment of the present invention;

[0032] Figure 2 It is a schematic diagram of a method for controlling the clutch oil pressure provided by an embodiment of the present invention;

[0033] Figure 3 It is a structural block diagram of an electronically controlled hydraulic system of a transmission provided by an embodiment of the present invention;

[0034] Figure 4 It is a curve graph of the target value of the dynamic turbine angular acceleration provided by an embodiment of the present invention. Detailed Embodiments

[0035] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the protection scope of the present invention.

[0036] Embodiment 1, as Figure 1 、 Figure 2 shown, this embodiment introduces a method for controlling the clutch oil pressure of a power shift transmission, including:

[0037] Obtain the engine speed, and calculate the corrected turbine torque in combination with the preset hydraulic torque converter parameters and the dynamic characteristics of the torque converter;

[0038] Obtain the current throttle pedal position, calculate the target value of the turbine angular acceleration, and perform dynamic correction to obtain the corrected dynamic target value of the turbine angular acceleration;

[0039] Calculate the feedforward target oil pressure based on the calculated turbine torque and the dynamic target value of the turbine angular acceleration;

[0040] Based on the actually measured value of the turbine angular acceleration obtained in advance and the corrected dynamic target value of the turbine angular acceleration;

[0041] Calculate the target oil pressure of the clutch based on the feedforward target oil pressure and the feedback target oil pressure, and convert it into a control signal to be sent to the solenoid valve, and control the clutch oil pressure through the solenoid valve to achieve the gear shifting action of the transmission.

[0042] The clutch oil pressure control method for the power shift transmission provided in this embodiment is applied to the electro-hydraulic control system of the transmission, and its structure is shown in Figure 3 , which is composed of an engine 1, a torque converter 2, a transmission 3, a drive wheel 4, a clutch 5, a solenoid valve 6, a throttle position sensor 7, speed sensors 8 and 9, an engine control unit (ECU) 10, a transmission control unit (TCU) 11, and other signals 12.

[0043] The ECU receives the engine speed and sends it to the TCU; the speed sensors installed on the torque converter send the measured pump wheel speed and turbine speed to the TCU; the speed sensor installed at the output shaft of the transmission sends the measured transmission output shaft speed to the TCU. After receiving the above data and signals, the TCU calculates the target oil pressure of the clutch according to the internally preset parameters, and sends a control signal to the solenoid valve, thereby realizing the control of the clutch oil pressure and the gear shifting action of the vehicle transmission.

[0044] The following parameters and corresponding relationships are stored in the TCU: the preset acting radius of the clutch transmission torque, the number of friction pairs, the piston acting area, the friction coefficient of the friction pair, and the return spring force;

[0045] The corresponding relationship between the preset pump wheel torque correction value and the actually measured value of the turbine angular acceleration;

[0046] The corresponding relationship between the preset target value of the turbine angular acceleration and the throttle opening;

[0047] The corresponding relationship between the preset trigonometric function period T and the throttle opening;

[0048] The preset transmission ratios of each gear.

[0049] The TCU receives the current engine speed sent by the ECU, the pump impeller speed and the turbine speed sent by the speed sensor, and calculates the theoretical value of the turbine torque according to the corresponding relationship between the parameters of the torque converter, the torque ratio and the torque converter speed ratio preset in the TCU.

[0050] Specifically, it is calculated by formula (1):

[0051] (1);

[0052] Where, is the engine speed, is the pump impeller speed, is the pump impeller speed, is the turbine torque, is the pump impeller torque, is the corrected pump impeller torque, is the torque converter speed ratio, is the torque converter torque ratio, is the density of the working medium oil, is the acceleration due to gravity, is the effective diameter of the circulating circle, is the pump impeller torque coefficient.

[0053] Due to the harsh working conditions of construction machinery and large load fluctuations, the fluctuation of the turbine speed will cause the fluctuation of the pump impeller torque, making the calculation result of the static characteristic expression of the torque converter inaccurate. Therefore, the dynamic output torque of the pump impeller is corrected.

[0054] The corresponding relationship between the dynamic output torque of the pump impeller and the actual value of the turbine angular acceleration is stored in the TCU in the form of Table 1, and this corresponding relationship is shown in Table 1:

[0055] Table 1 Corresponding relationship between the actual value of the turbine angular acceleration and the corrected value of the pump impeller output torque

[0056]

[0057] Next, the throttle position is obtained, and according to the corresponding relationship between the preset throttle opening and the target value of the turbine angular acceleration, the target value of the turbine angular acceleration is obtained. The corresponding relationship between the preset target value of the turbine angular acceleration and the throttle opening is shown in Table 2:

[0058] Table 2 Corresponding relationship between the preset target value of the turbine angular acceleration and the throttle opening

[0059]

[0060] Meanwhile, to avoid the step change of the clutch target oil pressure and the target value of the turbine angular acceleration at the start and end of starting or shifting, which may cause impact on the transmission system, the dynamic target value of the turbine angular acceleration is calculated. The calculation result is as shown in Figure 4 shown.

[0061] Specifically, it is calculated by formula (2):

[0062] (2);

[0063] Wherein, is the corrected dynamic target value of the turbine angular acceleration, is the target value of the turbine angular acceleration, is the period of the trigonometric function, is the current shifting time, is the moment when the corrected dynamic target value of the turbine angular acceleration starts to decrease.

[0064] The oil pressure starts to increase from 0, reaches the target value at and starts to decrease at and returns to 0 at At this moment, the rotational speed difference between the driving and driven disks has been eliminated. Wherein, can take a certain fixed value according to engineering experience, or a corresponding relationship with the throttle opening is preset to enhance its working condition adaptability. In this embodiment, the corresponding relationship between the preset trigonometric function period T and the throttle opening is shown in Table 3:

[0065] Table 3 Corresponding relationship between the preset trigonometric function period T and the throttle opening

[0066]

[0067] Then, the calculation is carried out in the following way: The TCU calculates the theoretical value of the turbine speed when shifting into the target gear at the current vehicle speed according to the current transmission output shaft speed, the target gear and the preset transmission ratios of each gear, and calculates the speed difference between the current turbine speed and the theoretical value of the turbine speed in the target gear, and compares it with the preset target speed difference.

[0068] The preset target speed difference is calculated by formula (3):

[0069] (3);

[0070] Wherein, is the speed difference between the current turbine speed and the target turbine speed, is the current turbine speed, is the transmission output shaft speed, is the transmission ratio of the target gear.

[0071] When the rotational speed difference between the current turbine speed and the turbine speed at the target gear is equal to or less than , the dynamic target value of the turbine angular acceleration starts to smoothly transition from the preset target value of the turbine angular acceleration to 0 according to the trigonometric function fitting of the dynamic target value of the turbine angular acceleration in formula (2). The corrected dynamic target value of the turbine angular acceleration is as shown in Figure 4 .

[0072] After that, the TCU calculates the feedforward target oil pressure based on the turbine torque calculated above, the corrected dynamic target value of the turbine angular acceleration , as well as the preset acting radius of the clutch transmission torque, the number of friction pairs, the piston acting area, the friction coefficient of the friction pair, and the return spring force.

[0073] The feedforward target oil pressure is calculated by formula (4):

[0074] (4);

[0075] where is the feedforward target oil pressure, is the moment of inertia of the transmission input end, is the number of clutch friction pairs, is the friction coefficient of the friction pair, is the acting radius of the clutch transmission torque, is the piston acting area, is the return spring force.

[0076] According to the difference between the target turbine speed change rate and the actual turbine speed change rate, PID adjustment is performed to obtain the feedback target oil pressure. The proportional coefficient, integral coefficient, and differential coefficient of the PID adjustment coefficient need to be determined according to the specific parameters and performance of the transmission.

[0077] Embodiment 2, the present invention provides a clutch oil pressure control system for a power shift transmission, adopting the power shift transmission clutch oil pressure control method described in any one of Embodiment 1. The system includes: an engine, a torque converter, a transmission, a driving wheel, a clutch, a solenoid valve, an accelerator position sensor, a first rotational speed sensor, a second rotational speed sensor, an engine control unit, and a transmission control unit. The first rotational speed sensor is installed on the torque converter, and the second rotational speed sensor is installed on the output shaft of the transmission, where:

[0078] The engine control unit receives the engine speed and sends it to the transmission control unit. The first speed sensor sends the measured pump speed and turbine speed to the transmission control unit. The second speed sensor sends the measured transmission output shaft speed to the transmission control unit. After receiving the data from the engine control unit, the first speed sensor, and the second speed sensor, the transmission control unit calculates the target clutch oil pressure according to the internally preset parameters and sends a control signal to the solenoid valve. The solenoid valve controls the clutch oil pressure to achieve the gear shifting operation of the transmission.

[0079] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for controlling the oil pressure of a power shift transmission clutch, characterized in that, Including: Obtain the engine speed, and calculate the corrected turbine torque by combining the preset parameters of the hydraulic torque converter and the dynamic characteristics of the torque converter; Obtain the current throttle pedal position, calculate the target value of the turbine angular acceleration, and perform dynamic correction to obtain the corrected target value of the dynamic turbine angular acceleration; The dynamic correction formula is as follows: ； Among them, is the corrected dynamic turbine angular acceleration target value, is the turbine angular acceleration target value, is the period of the trigonometric function, is the current shift time, is the moment when the corrected dynamic turbine angular acceleration target value starts to decline; Calculate the feedforward target oil pressure according to the calculated turbine torque and the target value of the dynamic turbine angular acceleration; Calculate the feedback target oil pressure according to the actually measured value of the turbine angular acceleration obtained in advance and the corrected target value of the dynamic turbine angular acceleration; Calculate the target oil pressure of the clutch according to the feedforward target oil pressure and the feedback target oil pressure, and convert it into a control signal to be sent to the solenoid valve, and control the clutch oil pressure through the solenoid valve to realize the shifting action of the transmission.

2. The hydraulic pressure control method of the power shift transmission clutch according to claim 1, wherein The formula for obtaining the engine speed, combining the preset parameters of the hydraulic torque converter and the dynamic characteristics of the torque converter, and calculating the corrected turbine torque is as follows: ； Among them, is the engine speed, is the impeller speed, is the turbine speed, is the turbine torque, is the impeller torque, is the corrected impeller torque, is the torque converter ratio, is the torque multiplication ratio of the torque converter, is the density of the working medium oil, is the acceleration due to gravity, is the effective diameter of the circulation circle, is the impeller torque coefficient.

3. The hydraulic pressure control method for the power shift transmission clutch according to claim 1, characterized in that, During the oil pressure control process, the oil pressure starts to increase from 0 and reaches the target value at , starts to decrease at , and returns to 0 at . At this moment, the rotational speed difference between the driving and driven disks has been eliminated.

4. The hydraulic pressure control method of the power shift transmission clutch according to claim 1, wherein The change process of the target value of the dynamic turbine angular acceleration is fitted according to formula (2), and when the preset conditions are met, the target value of the dynamic turbine angular acceleration smoothly transitions from the preset initial value to 0.

5. The hydraulic pressure control method for the power shift transmission clutch according to claim 4, characterized in that, The preset conditions are: the theoretical value of the turbine speed when shifting into the target gear at the current vehicle speed calculated according to the current transmission output shaft speed, the target gear, and the preset transmission ratios of each gear, and the rotational speed difference between the current turbine speed is equal to or less than the preset target rotational speed difference.

6. The hydraulic pressure control method of the power shift transmission clutch according to claim 5, characterized in that, The preset target rotational speed difference is calculated by formula (3): ； wherein, is the rotational speed difference between the current turbine speed and the target turbine speed, is the current turbine speed, is the rotational speed of the output shaft of the transmission, is the transmission ratio of the target gear.

7. The hydraulic pressure control method for the power shift transmission clutch according to claim 1, wherein The formula for calculating the feedforward target oil pressure according to the calculated turbine torque and the target value of the dynamic turbine angular acceleration is as follows: ； Among them, is the feedforward target oil pressure, is the moment of inertia of the transmission input end, is the number of pairs of clutch friction pairs, is the friction coefficient of the friction pair, is the action radius of the clutch transmission torque, is the piston action area, is the return spring force.

8. A hydraulic pressure control system for a power shift transmission clutch, adopting the power shift transmission clutch hydraulic pressure control method according to any one of claims 1-7, the system comprising: An engine, a hydraulic torque converter, a transmission, a driving wheel, a clutch, a solenoid valve, a throttle position sensor, a first speed sensor, a second speed sensor, an engine control unit, and a transmission control unit. The first speed sensor is installed on the hydraulic torque converter, and the second speed sensor is installed on the output shaft of the transmission, where: The engine control unit receives the engine speed and sends it to the transmission control unit. The first speed sensor sends the measured pump wheel speed and turbine speed to the transmission control unit. The second speed sensor sends the measured transmission output shaft speed to the transmission control unit. After receiving the data from the engine control unit, the first speed sensor, and the second speed sensor, the transmission control unit calculates the target oil pressure of the clutch according to the internally preset parameters, and sends a control signal to the solenoid valve to control the clutch oil pressure through the solenoid valve to realize the shifting action of the transmission.

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