Clutch oil pressure control method and clutch driving system

Abstract

The invention relates to the technical field of gearbox clutches, and particularly provides a clutch oil pressure control method and a clutch driving system. According to the clutch oil pressure control method, a brushless direct current motor is adopted to drive an oil pump to supply oil to a clutch, and the control method comprises the steps that target oil pressure needed by the clutch under the current working condition is obtained, and the corresponding relation between the target oil pressure and q-axis current of the brushless direct current motor is established; determining q-axis target current of the brushless direct current motor corresponding to the target oil pressure according to the corresponding relation, and obtaining q-axis target voltage according to the target current, so that the actual oil pressure output to the clutch by the oil pump approaches the target oil pressure. According to the clutch oil pressure control method, vector control is adopted, the pressure of the brushless direct current motor is controlled by controlling the q-axis (quadrature-axis) current of the brushless direct current motor, signal dependence on the oil temperature sensor is reduced, the control logic of clutch oil pressure can be simplified, and the working efficiency of the brushless direct current motor can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of transmission clutch, and in particular to a clutch oil pressure control method. In addition, the present invention also relates to a clutch drive system. Background Art

[0002] In traditional automatic transmissions and special hybrid transmissions, the clutch pressure is generally controlled by directly controlling the clutch pressure through a brushless DC motor (BLDC) driving the oil pump. Compared with the traditional pressure control method using a solenoid valve, the pressure control method of the brushless DC motor driving the oil pump reduces the complex and costly hydraulic valve plate and solenoid valve, while avoiding the problem of solenoid valve jamming, reducing the complexity of the hydraulic system and improving the robustness of the system.

[0003] Usually, in the way that the oil pump controls the clutch oil pressure, the oil pump runs to fill the oil into the oil channel and the clutch cavity. There is a fixed oil drain port on the oil channel between the oil pump and the clutch cavity. The flow rate pumped in by the oil pump and the flow rate discharged from the oil drain port opening are balanced, and the corresponding stable oil pressure is generated through the throttle hole (the oil drain port with a fixed opening). The fluid dynamics equation of the oil drain port determines the pressure difference at both ends of the oil drain port (because the pressure outside the oil drain port is atmospheric pressure, the pressure difference on both sides of the oil drain port is equal to the oil pressure of the clutch oil channel relative to atmospheric pressure), which is mainly determined by the flow rate, the cross-sectional area of ​​the oil drain port, and the viscosity of the oil. Among them, the flow rate of the oil drain port is basically equal to the flow rate of the oil pumped out by the oil pump, the cross-sectional area of ​​the oil drain port is immutable, and the viscosity of the oil is sensitive to the oil temperature. Therefore, to establish the same pressure, the required speed of the oil pump at different oil temperatures varies greatly.

[0004] For the above hydraulic system, at different oil temperatures, the steady-state pressure, BLDC duty cycle and oil pump speed form a corresponding combination relationship. As shown in the example in Table 1, when the oil temperature changes, the same pressure corresponds to different BLDC duty cycles and oil pump speeds. Pressure control is very sensitive to oil temperature. For example, in the double closed-loop pressure control adopted in the comparative patent CN113790225A, in the most important control steps, the basic speed of the oil pump is obtained by looking up the target pressure and oil temperature, the basic duty cycle of the BLDC is obtained by looking up the target pressure and oil temperature, and the PID parameters of the pressure closed-loop control are also obtained by looking up the control deviation and the oil temperature. The existing control methods, including those mentioned in the above comparative patents, are strongly dependent on the oil temperature sensor. Once the sensor fails, it will seriously affect the control of the clutch oil pressure, making the control function of the gearbox clutch unable to be realized normally.

[0005] Table 1 Example of oil temperature-pressure-duty cycle-speed correspondence

[0006]

[0007] In addition, due to the principle of oil channel pressure building, in addition to oil temperature, the size of the throttle hole diameter also has a great influence on the combined relationship of pressure-BLDC duty cycle-oil pump speed. Due to process limitations, there is a certain tolerance in the processing of the throttle hole, resulting in strong individual differences in the combined relationship of pressure-BLDC duty cycle-oil pump speed, and this influencing factor cannot be measured by sensors. The example shown in Table 2 reflects the influence of different throttle hole diameters on BLDC duty cycle-oil pump speed at the same pressure of 8 bar. At present, there is no relevant research in the industry that proposes an effective response to this problem.

[0008] At present, for the BLDC used in the hydraulic system, the industry generally adopts the six-step method to control BLDC. The BLDC controlled by the six-step method has a large torque pulsation, which is easy to cause pressure fluctuations. However, the vector control FOC has a smaller torque pulsation, is easy to reduce pressure fluctuations, and has higher electrical efficiency.

[0009] Table 2 Effect of throttle hole diameter on duty cycle and oil pump speed at 8 bar pressure

[0010]

[0011] Summary of the invention

[0012] In view of this, the present invention aims to propose a clutch oil pressure control method to get rid of the strong dependence of pressure control on the oil temperature sensor, while solving the individual differences caused by the throttle hole diameter and improving the consistency of pressure control performance.

[0013] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0014] A clutch oil pressure control method uses a brushless DC motor to drive an oil pump to supply oil to the clutch, and the control method includes:

[0015] Obtaining the target oil pressure required under the current working condition of the clutch, and establishing a corresponding relationship between the target oil pressure and the q-axis current of the brushless DC motor;

[0016] Determining a q-axis target current of the brushless DC motor corresponding to the target oil pressure according to the corresponding relationship;

[0017] The q-axis target voltage is obtained according to the q-axis target current, so that the q-axis actual current is close to the q-axis target current, thereby making the actual oil pressure output by the oil pump to the clutch approach the target oil pressure.

[0018] Furthermore, obtaining the target oil pressure required by the clutch under the current working condition includes:

[0019] Establishing a clutch pressure-clutch torque characteristic table based on the torque characteristic of the clutch;

[0020] The target oil pressure is obtained by querying the clutch pressure-clutch torque characteristic table.

[0021] Furthermore, the corresponding relationship is constructed in the form of an oil pressure-q-axis current characteristic table; the oil pressure-q-axis current characteristic table is constructed based on the oil supply characteristics of the oil pump to the clutch driven by the brushless DC motor.

[0022] Further, the acquiring the q-axis target voltage according to the q-axis target current so that the q-axis current is close to the q-axis target current includes:

[0023] Acquiring the actual current of the q-axis and the actual current of the d-axis of the brushless DC motor, and setting the target current of the d-axis of the brushless DC motor;

[0024] Determine the q-axis target voltage and the d-axis target voltage of the brushless DC motor respectively by using the q-axis actual current and the q-axis target current, and the d-axis actual current and the d-axis target current;

[0025] The three-phase target voltage of the brushless DC motor is obtained according to the q-axis target voltage and the d-axis target voltage, and the three-phase voltage of the brushless DC motor is controlled to be close to the three-phase target voltage, so that the q-axis actual current and the d-axis actual current approach the q-axis target current and the d-axis target current respectively.

[0026] Furthermore, the d-axis target current is set to 0A.

[0027] Further, the obtaining of the actual q-axis current and the actual d-axis current of the brushless DC motor includes:

[0028] Collecting the three-phase current of the brushless DC motor;

[0029] The collected three-phase currents are subjected to Clark transformation and Park transformation in sequence to obtain the q-axis actual current and the d-axis actual current.

[0030] Further, the determining of the q-axis target voltage and the d-axis target voltage of the brushless DC motor includes:

[0031] Calculating corresponding current tracking errors based on the q-axis actual current and the q-axis target current, and the d-axis actual current and the d-axis target current respectively;

[0032] The q-axis target voltage and the d-axis target voltage are calculated and obtained by a PID controller according to the current following error.

[0033] Furthermore, the three-phase target voltage is obtained by performing Park inverse transformation and Clark inverse transformation on the q-axis target voltage and the d-axis target voltage in sequence and calculating them.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The clutch oil pressure control method of the present invention adopts vector control and controls the pressure of the clutch by controlling the q-axis (quadrature-axis) current of the brushless DC motor, which can simplify the control logic of the clutch oil pressure; at the same time, since the oil pressure is closely related to the torque of the brushless DC motor and the q-axis current of the brushless DC motor is positively correlated with the output torque of the brushless DC motor, the q-axis current is used as the core control variable of the oil pressure to reduce the signal dependence on the oil temperature sensor.

[0036] In addition, because there is a processing tolerance in the diameter of the throttle hole, this parameter greatly affects the steady-state correspondence of the hydraulic system. For example, at the same temperature, the relationship between steady-state pressure-steady-state oil pump speed-steady-state BLDC duty cycle will cause the basic table during clutch pressure control to be difficult to cover all individual boxes. During pressure control, the basic target oil pump speed and basic target duty cycle calculated according to the basic table are greatly different from the actual performance of the box, resulting in inconsistency in pressure control quality. The present invention can solve this problem well, because different throttle hole diameters do not affect the steady-state relationship between clutch pressure and BLDC output torque. The control scheme proposed by the present invention uses the q-axis current that is positively correlated with the BLDC output torque, which can be unaffected by individual differences in the box throttle holes.

[0037] In addition, according to the difference between the actual current and the target current of the d-axis and q-axis, after determining the q-axis target voltage and d-axis target voltage of the brushless DC motor, the current actual current situation can be changed by adjusting and controlling the three-phase target voltage of the brushless DC motor to infinitely approach and reach the target current requirement, thereby achieving a good oil pressure control effect on the clutch.

[0038] Another object of the present invention is to propose a clutch drive system for oil pressure drive of a vehicle clutch, the clutch drive system being configured with a control unit; the control unit comprising a processor and a memory, the memory storing a computer program, the computer program being executed by the processor to implement the clutch oil pressure control method described in the present invention.

[0039] Furthermore, an oil passage is connected between the oil pump and the clutch, an oil pressure sensor for detecting the clutch oil pressure is provided on the oil passage, and the oil passage is connected to an oil return pipeline for returning the oil supply liquid, and a throttling hole is provided on the oil return pipeline.

[0040] The clutch drive system of the present invention has the technical advantages of the clutch oil pressure control method described above. Moreover, since the clutch oil pressure is directly used as an independent variable to control the q-axis current of the brushless DC motor, the control logic is simple and effective, and the monitoring of the oil temperature can be omitted, thereby avoiding the problem that the control cannot be realized when the oil temperature sensor fails due to the control dependence. At the same time, the negative impact of the throttle diameter tolerance on the pressure control is avoided, and the consistency of the pressure control is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which constitute part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention. The directional terms such as front and back, up and down, etc. involved therein are only used to indicate relative positional relationships and do not constitute improper limitations on the present invention. In the accompanying drawings:

[0042] Figure 1 It is a schematic diagram of the overall control flow of the clutch oil pressure control method according to an embodiment of the present invention;

[0043] Figure 2 A schematic diagram of a control flow of controlling the clutch oil pressure by using the q-axis current in the clutch oil pressure control method according to an embodiment of the present invention;

[0044] Figure 3 A schematic diagram of a target current vector control process of a brushless DC motor according to an embodiment of the present invention;

[0045] Figure 4 Schematic diagram of the system structure of the clutch drive system according to an embodiment of the present invention.

[0046] Description of reference numerals:

[0047] 1. Brushless DC motor; 10. Motor controller; 2. Oil pump; 20. Oil supply container; 21. Oil supply pipeline; 22. Oil supply filter; 3. Oil channel; 30. Oil drain port; 31. Oil return filter; 32. Throttle hole; 33. Oil return pipeline; 4. Oil pressure sensor; 5. Clutch. DETAILED DESCRIPTION

[0048] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0049] In the description of the present invention, it should be stated that if terms indicating directions or positional relationships such as up, down, left, right, front, back, inside, and outside appear, they are based on the directions or positional relationships shown in the drawings and are only for the convenience of describing the present invention. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed or operate in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0050] In addition, in the description of the present invention, unless otherwise clearly defined, the terms installation, connection, connection, and connector should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, an indirect connection through an intermediate medium, or a connection between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood in combination with specific circumstances.

[0051] In addition, the q-axis (quadrature axis) mentioned in the embodiments of the present invention refers to the quadrature axis of the motor, and its main function is to control the magnitude of the motor output force); the d-axis (direct-axis) refers to the direct axis of the motor, and its main function is to control the magnitude of the motor magnetic field. Clark transformation (also known as coordinate transformation method) is mainly used to convert the time domain components of the three-phase system (in the abc coordinate system) into two components in the orthogonal stationary coordinate system (αβ); Park transformation is mainly used to analyze the operation of synchronous motors. It was proposed by American engineer RH Park in 1929. The purpose is to project the a, b, and c three-phase currents of the stator onto the direct axis (d axis) and the quadrature axis (q axis) that rotate with the rotor, thereby realizing the diagonalization of the stator inductance matrix and simplifying the operation analysis of the synchronous motor. BLDC (Brushless Direct Current Motor) is the abbreviation of brushless DC motor.

[0052] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0053] Embodiment 1

[0054] This embodiment relates to a clutch oil pressure control method, which uses a brushless DC motor 1 to drive an oil pump 2 to supply oil to a clutch 5, which can simplify the oil pressure control logic of the clutch 5 and improve the working efficiency of the brushless DC motor 1; an exemplary control process is as follows Figure 1 shown.

[0055] In general, the control method includes the following steps:

[0056] S1, obtaining the target oil pressure required by the clutch 5 under the current working condition, and establishing a corresponding relationship between the target oil pressure and the q-axis current of the brushless DC motor 1;

[0057] S2, determining the q-axis target current of the brushless DC motor 1 corresponding to the target oil pressure according to the corresponding relationship;

[0058] S3. According to the q-axis target current, the q-axis current is controlled to be close to the q-axis target current, so that the actual oil pressure output by the oil pump 2 to the clutch 5 approaches the target oil pressure.

[0059] It should be pointed out that, based on the above-mentioned overall design concept, the technical solution of the present invention can adopt a variety of different specific implementation structures, forms or configuration sequences. For example, the above-mentioned target oil pressure can be calculated based on the working load condition of the clutch 5 through a preset formula, or it can be determined by looking up a pre-established table. For the parts required for the implementation of the overall solution but not involved in the above-mentioned overall setting, reasonable and flexible designs can be made with reference to the mature setting means in the field, the actual situation during implementation, etc. The specific implementation scheme described below in this embodiment is only one of the better solutions that can be formed by the above-mentioned various combinations and their variations. In actual implementation, those skilled in the art can make flexible adjustments and improvements based on the actual situation. Obviously, the many solutions that can be formed by the above-mentioned various specific forms of combination and their variations, as well as the specific implementation scheme of this embodiment, are all within the scope of protection of the present invention.

[0060] In this embodiment, a clutch pressure-clutch torque characteristic table is pre-established based on the torque characteristic of the clutch 5, and the target oil pressure is obtained by a table lookup method. At the same time, preferably, the above correspondence is constructed in the form of an oil pressure-q-axis current characteristic table; first, based on the oil supply characteristic of the lower oil pump 2 driven by the brushless DC motor 1 to the clutch 5, an oil pressure-q-axis current characteristic table is pre-established as the above correspondence; then, the q-axis target current of the brushless DC motor 1 is determined by the target oil pressure based on the oil pressure-q-axis current characteristic table.

[0061] According to the oil supply performance characteristics of the oil pressure system of the oil pump 2 and the torque characteristics of the oil pressure sensor 4, through mathematical modeling and experimental verification, the functional relationship between the oil pressure of the clutch 5 and the q-axis current of the brushless DC motor 1 of the oil pump 2 can be constructed. By establishing a functional model, the q-axis current required by the brushless DC motor 1 can be determined according to the current target oil pressure of the clutch 5; similarly, the relationship between the torque of the clutch 5 and the oil pressure of the clutch 5 can also be established through mathematical modeling and verification. By using the table lookup method, by pre-establishing a data corresponding table, the control amount can be quickly determined according to the target amount, thereby reducing the control calculation amount and improving the control efficiency.

[0062] like Figure 2As shown, according to the obtained target oil pressure prs_tar of the clutch 5, the oil pressure-q-axis current characteristic table P-ITable is checked to obtain the q-axis target current Iq_tar of the brushless DC motor 1, and then the d-axis target current Id_tar of the brushless DC motor 1 is set; the q-axis target current Iq_tar and the d-axis target current Id_tar are input to the motor controller 10, and the target current is used as the control target to control the q-axis actual current Iq_act1 and the q-axis actual current Id_act1 of the brushless DC motor 1 to approach the corresponding target current, so that the brushless DC motor 1 can achieve the expected output torque and operation requirements, and the actual oil pressure output by the oil pump 2 can approach the target oil pressure, and finally meet the control standard of the target oil pressure.

[0063] As for the specific control method of the q-axis current, there are of course a variety of different control schemes to choose from; for example, the existing proportional regulation control model can be referred to to adjust the input voltage of the motor according to the difference between the actual current and the target current.

[0064] In this embodiment, if Figure 1 Combine and combine Figure 3 As shown, obtaining the q-axis target voltage according to the q-axis target current and making the q-axis current close to the q-axis target current specifically includes the following steps:

[0065] S21, obtaining the q-axis actual current and the d-axis actual current of the brushless DC motor 1, and setting the d-axis target current of the brushless DC motor 1;

[0066] S22, determining the q-axis target voltage and the d-axis target voltage of the brushless DC motor 1 by using the q-axis actual current and the q-axis target current, and the d-axis actual current and the d-axis target current respectively;

[0067] S23, obtaining the three-phase target voltage of the brushless DC motor 1 according to the q-axis target voltage and the d-axis target voltage, and controlling the three-phase voltage of the brushless DC motor 1 to be close to the three-phase target voltage, so that the q-axis actual current and the d-axis actual current approach the q-axis target current and the d-axis target current respectively.

[0068] According to the difference between the actual current and the target current of the d-axis and q-axis, by adjusting and controlling the three-phase voltage of the brushless DC motor 1, the current actual current situation can be changed to infinitely approach and reach the required target current situation, thereby achieving a good oil pressure control effect on the clutch 5.

[0069] Among them, it is preferred to set the d-axis target current to 0A. When the brushless DC motor 1 adopts the vector control method, the torque of the brushless DC motor 1 can be controlled by controlling the q-axis current, and the magnetic field can be controlled by controlling the d-axis current. Because the d-axis does not contribute to the torque, when the d-axis current Id=0A is controlled, the total current of the motor under the same torque condition is minimized, which can maximize the efficiency of the brushless DC motor 1. Selecting the q-axis current to generate the torque of the brushless DC motor 1 required for the target oil pressure of the clutch 5 is similar to the solenoid valve control oil pressure method in which the electromagnetic force corresponding to the clutch pressure is generated by controlling the solenoid valve current, thereby changing the oil pressure of the clutch 5, and has a good control effect.

[0070] Moreover, the above control scheme is adopted to get rid of the strong dependence of pressure control on the oil temperature sensor. The control of q-axis current provides the main oil pump torque support for the establishment of oil pressure. The brushless DC motor 1 can adjust the q-axis current in time according to the target oil pressure, thereby meeting the target oil pressure requirement.

[0071] like Figure 3 As shown, the actual current of the q-axis and the actual current of the d-axis of the brushless DC motor 1 can be obtained in the following manner:

[0072] S211, collecting three-phase currents of the brushless DC motor 1;

[0073] S212, performing Clark transformation and Park transformation on the collected three-phase current in sequence to obtain a q-axis actual current and a d-axis actual current.

[0074] Since the q-axis current is a virtual current and cannot be directly measured by a sensor, in actual vector control, the actual three-phase currents Iu, Iv and Iw of the brushless DC motor 1 are first collected according to the current sensor, and the three-phase currents Iu, Iv and Iw are converted into the actual currents Id and Iq of the d-axis and q-axis through Clark transformation and Park transformation. According to the current difference between the target currents of the d-axis and q-axis (the q-axis target current is determined based on the target oil pressure, and the d-axis target current is set in the system) and the actual currents of the d-axis and q-axis, the PID adjustment method is used to calculate the target voltages Vd and Vq of the d-axis and q-axis, and then the target voltages Vd and Vq are converted into the three-phase target voltages required to control the brushless DC motor 1 through Park inverse transformation and Clark inverse transformation, so that the power output of the brushless DC motor 1 can be well controlled, and the target oil pressure required by the clutch 5 can be obtained.

[0075] Based on the above-mentioned conversion calculation structure, the corresponding current tracking errors are calculated according to the q-axis actual current and the q-axis target current, as well as the d-axis actual current and the d-axis target current. According to the current following errors, the q-axis target voltage and the d-axis target voltage are calculated by the PID controller; the q-axis target voltage and the d-axis target voltage of the brushless DC motor 1 can be determined.

[0076] After the q-axis target voltage and the d-axis target voltage of the brushless DC motor 1 are determined, the three-phase target voltage can be obtained in the following manner:

[0077] The q-axis target voltage and the d-axis target voltage are subjected to Park inverse transformation and Clark inverse transformation in sequence, and the three-phase target voltage of the brushless DC motor 1 is calculated.

[0078] In general, the motor controller 10 (MCU) can obtain the current tracking error of the q-axis and d-axis according to the q-axis and d-axis target currents of the brushless DC motor 1 (BLDC), and the actual q-axis and d-axis currents obtained by Clark transformation and Park transformation of the three-phase currents Iu, Iv and Iw; calculate the target voltages Vq and Vd of the q-axis and d-axis through the PID controller according to the current following error of the q-axis and d-axis; calculate the three-phase target voltages Uu, Uv and Uw by using Park inverse transformation and Clark inverse transformation for the target voltages Vq and Vd of the q-axis and d-axis respectively; and then adjust the three-phase voltage of the BLDC to be infinitely close to the above-mentioned three-phase target voltage, so as to achieve the purpose of controlling the oil pressure of the clutch 5 according to the target current of the q-axis.

[0079] In traditional automatic transmissions, solenoid valves are usually used to control the clutch pressure. The electromagnetic coil (Electromagnetic Force Motor) of the solenoid valve is energized to generate thrust, which pushes the valve core to overcome the spring force and open the valve body oil inlet opening. The oil in the oil inlet flows to the clutch through the oil outlet. At the same time, some oil flows to the feedback chamber through the feedback port to establish feedback force. When the pressure at the oil outlet is established, the valve core is pushed through the feedback chamber, and the valve core oil inlet gradually closes, and finally reaches a balance under the control current of the solenoid valve and the oil outlet pressure. Through this method, the clutch pressure can be controlled by the solenoid valve current, and a one-to-one correspondence can be achieved in the steady state. The difference in the current-pressure (pI) characteristic curves at different oil temperatures is very small. However, this traditional solenoid valve oil circuit control method has high costs for the hydraulic valve plate and the solenoid valve, and it is difficult to avoid the problem of solenoid valve jamming.

[0080] In the system configuration of the clutch oil pressure control method of the present invention, the oil pressure of the clutch 5 causes the load of the oil pump 2 and its brushless DC motor 1. There is a one-to-one correspondence between the output torque of the brushless DC motor 1 and the oil pressure of the clutch 5. When the output torque of the brushless DC motor 1 is greater than the resistance torque generated by the oil pressure of the clutch 5, the speed of the oil pump 2 will increase, increasing the flow rate at the oil drain port, thereby increasing the pressure of the clutch 5 oil circuit. Finally, the output torque of the brushless DC motor 1 and the corresponding oil pressure of the clutch 5 reach a balance. It can be seen that the control amount used to control the torque of the brushless DC motor 1 has a key influence on the control of the oil pressure of the clutch 5.

[0081] Based on the above analysis, in the q-axis current vector control mode of the brushless DC motor 1 of this embodiment, the q-axis current Iq represents the torque of the brushless DC motor 1, and the load of the brushless DC motor 1 comes from the pressure of the clutch 5. Therefore, in the steady state, the q-axis current Iq is strongly correlated with the pressure of the clutch 5, and there is also a pressure-current (pI) relationship. Compared with the (pI) characteristic in the oil pressure control mode using the solenoid valve, it is also a characteristic relationship dominated by linearity. The oil temperature has a certain influence on the pI characteristic by affecting the volumetric efficiency and mechanical efficiency of the oil pump 2. However, compared with the traditional control mode, the control mode of the present invention greatly reduces the influence of the oil temperature on the control amount. By controlling the pressure through the q-axis current Iq, in the transient process, when the actual pressure is less than the target oil pressure, the Iq_tar corresponding to the target oil pressure will prompt the brushless DC motor 1 to drive the oil pump 2 to accelerate. When the actual pressure is close to the target oil pressure, the acceleration of the oil pump 2 will gradually decrease, and the system will reach a stable state.

[0082] Depend on Figure 2 and 3 It can be seen that the closed-loop control of the d-axis current Id can be implemented in the motor controller 10 (MCU) of the brushless DC motor 1, which can be achieved with a lower calculation cycle (10ms) than the transmission controller. For the transmission controller (TCU), it only needs to undertake the calculation task of the target current of the q-axis.

[0083] In summary, the clutch oil pressure control method of this embodiment adopts vector control, and controls the pressure of the clutch by controlling the q-axis current of the brushless DC motor 1, which can simplify the control logic of the clutch oil pressure. At the same time, since the oil pressure is closely related to the torque of the brushless DC motor 1, and the q-axis current of the brushless DC motor 1 is positively correlated with the output torque of the brushless DC motor 1, the q-axis current is used as the core control variable of the oil pressure, and the entire hardware configuration is relatively simple. Unlike the traditional hydraulic system, it is not necessary to configure complex mechanical structures such as solenoid valves and oil circuit boards, but it can achieve a good effect of controlling the oil pressure by controlling the driving current of the solenoid valve. It not only simplifies the control method of the hydraulic system, reduces the parameters that need to be calibrated and self-learned, but also improves the motor efficiency of the brushless DC motor 1 and reduces the signal dependence on the oil temperature sensor.

[0084] Embodiment 2

[0085] The present embodiment relates to a clutch driving system for oil pressure driving of a vehicle clutch 5 , and the clutch driving system is provided with a control unit.

[0086] Moreover, the control unit of this embodiment includes a processor and a memory. The memory stores a computer program, and the computer program is loaded and executed by the processor to implement the clutch oil pressure control method provided in the first embodiment.

[0087] The specific configuration of the clutch drive system can be flexibly configured by referring to the existing clutch drive oil circuit system, but it is necessary to use a brushless DC motor 1 to drive the oil pump 2 to supply and output the oil circuit. Figure 4 As shown, the clutch drive system of this embodiment is provided with an oil supply container 20, and the oil pump 2 sucks oil through the oil supply pipeline 21, and the oil supply pipeline 21 is provided with an oil supply filter 22. An oil passage 3 is connected between the oil pump 2 and the clutch 5, and an oil drain port 30 is provided on the oil passage 3. The oil pressure sensor 4 for detecting the oil pressure of the clutch 5 is also provided on the oil passage 3; the oil drain port 30 of the oil passage 3 is connected with an oil return pipeline 33 for reflux of the oil supply liquid, and the oil return pipeline 33 can discharge the oil back into the oil supply container 20; the oil return pipeline 33 is provided with a throttle hole 32 and an oil return filter 31, and the throttle hole 32 is preferably provided downstream of the oil return filter 31 to control the reflux speed of the oil.

[0088] The clutch drive system of this embodiment directly uses the oil pressure of the clutch 5 as an independent variable to control the q-axis current of the brushless DC motor 1. The control logic is simple and effective, and the monitoring of the oil temperature can be omitted, thus avoiding the problem that the control cannot be realized when the oil temperature sensor fails due to the control dependence on the oil temperature sensor. Compared with the traditional solenoid valve pressure control method, the hardware cost is greatly reduced, the overall control effect is better, and the working efficiency of the brushless DC motor 1 is also greatly improved.

[0089] At the same time, compared with the existing clutch oil pressure control scheme, it can be clearly seen that the machining tolerance of the throttle hole has a serious impact on the stable operation state of the hydraulic system of the existing scheme. At the same temperature, the relationship between steady-state pressure-steady-state oil pump speed-steady-state BLDC duty cycle will make it difficult for the basic table during clutch pressure control to cover all box individuals. During pressure control, the basic target oil pump speed and basic target duty cycle calculated according to the basic table are greatly different from the actual performance of the box. This difference is directly related to the machining tolerance of the throttle hole, resulting in inconsistency in the quality of pressure control.

[0090] The present invention can solve this problem well, because different throttle hole diameters do not affect the steady-state relationship between the clutch pressure and the BLDC output torque. The control scheme proposed in the present invention uses the q-axis current positively correlated with the BLDC output torque as the control object, which is not affected by the individual differences of the box throttle holes. Therefore, the individual differences caused by the throttle hole diameter are solved and the consistency of the system pressure control performance is improved.

[0091] The above description is only a preferred embodiment of the present invention. The detailed explanation of the configuration, the examples of the specific structural setting forms, or the description of the assembly connection mode, etc., are all for the purpose of sufficient disclosure so that those skilled in the art can better implement the present invention, but are not intended to limit the protection scope of the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A clutch oil pressure control method, using a brushless DC motor (1) to drive an oil pump (2) to supply oil to a clutch (5), characterized in that: The control method includes: Obtaining the target oil pressure required by the clutch (5) under the current working condition, and establishing a corresponding relationship between the target oil pressure and the q-axis current of the brushless DC motor (1); Determining a q-axis target current of the brushless DC motor (1) corresponding to the target oil pressure according to the corresponding relationship; A q-axis target voltage is obtained according to the q-axis target current, so that the q-axis current approaches the q-axis target current, thereby making the actual oil pressure output by the oil pump (2) to the clutch (5) approach the target oil pressure.

2. The clutch oil pressure control method according to claim 1, characterized in that: The step of obtaining the target oil pressure required by the clutch (5) under the current working condition comprises: Establishing a clutch pressure-clutch torque characteristic table based on the torque characteristic of the clutch (5); The target oil pressure is obtained by querying the clutch pressure-clutch torque characteristic table.

3. The clutch oil pressure control method according to claim 1, characterized in that: The corresponding relationship is constructed in the form of an oil pressure-q-axis current characteristic table; The oil pressure-q-axis current characteristic table is constructed based on the oil supply characteristics of the oil pump (2) to the clutch (5) driven by the brushless DC motor (1).

4. The clutch oil pressure control method according to any one of claims 1 to 3, characterized in that: The step of acquiring the q-axis target voltage according to the q-axis target current so that the q-axis current approaches the q-axis target current includes: Acquiring the actual q-axis current and the actual d-axis current of the brushless DC motor (1), and setting the d-axis target current of the brushless DC motor (1); Determining the q-axis target voltage and the d-axis target voltage of the brushless DC motor (1) respectively by using the q-axis actual current and the q-axis target current, and the d-axis actual current and the d-axis target current; The three-phase target voltage of the brushless DC motor (1) is obtained according to the q-axis target voltage and the d-axis target voltage, and the three-phase voltage of the brushless DC motor (1) is controlled to approach the three-phase target voltage, so that the q-axis actual current and the d-axis actual current approach the q-axis target current and the d-axis target current respectively.

5. The clutch oil pressure control method according to claim 4, characterized in that: The d-axis target current is set to 0A.

6. The clutch oil pressure control method according to claim 4, characterized in that: The step of obtaining the actual q-axis current and the actual d-axis current of the brushless DC motor (1) comprises: collecting three-phase current of the brushless DC motor (1); The collected three-phase currents are subjected to Clark transformation and Park transformation in sequence to obtain the q-axis actual current and the d-axis actual current.

7. The clutch oil pressure control method according to claim 4, characterized in that: Determining the q-axis target voltage and the d-axis target voltage of the brushless DC motor (1) comprises: Calculating corresponding current tracking errors based on the q-axis actual current and the q-axis target current, and the d-axis actual current and the d-axis target current respectively; The q-axis target voltage and the d-axis target voltage are calculated and obtained by a PID controller according to the current following error.

8. The clutch oil pressure control method according to claim 4, characterized in that: The three-phase target voltage is obtained by performing Park inverse transformation and Clark inverse transformation on the q-axis target voltage and the d-axis target voltage in sequence and calculating.

9. A clutch drive system for hydraulically driving a vehicle clutch (5), characterized in that: The clutch drive system is provided with a control unit; The control unit includes a processor and a memory, wherein a computer program is stored in the memory, and the computer program is executed by the processor to implement the clutch oil pressure control method according to any one of claims 1 to 8.

10. The clutch drive system according to claim 9, characterized in that: An oil passage (3) is connected between the oil pump (2) and the clutch (5), an oil pressure sensor (4) for detecting the oil pressure of the clutch (5) is provided on the oil passage (3), and an oil return pipeline (33) for returning the oil supply liquid is connected to the oil passage (33), and a throttling hole (32) is provided on the oil return pipeline (33).

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