Electric oil pump control method and system for continuously variable transmission of electric vehicle

Abstract

The present invention discloses a method for controlling an electric oil pump of a continuously variable transmission of an electric vehicle, and belongs to the technical field of continuously variable transmission electric oil pump control. The method first determines whether the hydraulic control unit of the continuously variable transmission has a pressure demand, and if not, further determines whether the hydraulic control unit has a flow demand. When there is neither a pressure demand nor a flow demand, the target speed of the electric oil pump is set to 0, thereby reducing the power loss of the control unit; when one of the system pressure and the system flow exists, the target speed of the electric oil pump is set to be greater than 0, and then adjusted according to whether the vehicle working condition is a transient working condition or a steady-state working condition, to obtain a specific target speed of the electric oil pump. The present invention also discloses a control system for an electric oil pump of a continuously variable transmission of an electric vehicle. The present invention achieves rapid response and optimized energy saving of a continuously variable transmission execution control system by optimizing the electric oil pump control strategy.

Description

Technical Field

[0001] The present invention belongs to the technical field of continuously variable transmission electric oil pump control, and in particular relates to a method and system for controlling an electric oil pump of a continuously variable transmission of an electric vehicle. Background Art

[0002] In order to improve the power and economy of electric vehicles, multi-speed transmissions are used in pure electric vehicles, and continuously variable transmissions have the characteristic of shifting without power interruption, making them ideal multi-speed transmissions for passenger cars. Traditional continuously variable transmissions use mechanical oil pumps to supply oil, which are driven by the engine speed. Since the engine speed has an idle speed, it can guarantee the flow demand of the hydraulic control system to a certain extent. However, due to the existence of the engine idle speed, the loss of the hydraulic system is also increased.

[0003] The speed of the traditional mechanical oil pump is coupled to the engine and cannot be adjusted independently according to the flow demand. When the engine speed is high, the oil pump speed is high, resulting in a large amount of flow loss and large losses; when the engine speed is low, the oil pump speed is low and cannot provide the corresponding flow according to the speed change response requirements, reducing the response effect of the speed ratio tracking. When the traditional continuously variable transmission is applied to electric vehicles, since the motor does not have an idle speed, the mechanical oil pump cannot supply oil, so an electric oil pump is required. The electric oil pump provides flow and pressure to the hydraulic control system through the motor. Since the motor speed is adjustable, the oil pump speed can be decoupled from the drive motor speed.

[0004] Therefore, it is urgent to invent an electric oil pump control method and system for an electric vehicle continuously variable transmission to solve the above technical problems. Summary of the invention

[0005] The present invention discloses a method and system for controlling an electric oil pump of a continuously variable transmission of an electric vehicle, which can adjust the oil pump speed in real time according to flow demand to reduce flow loss, and can also calculate the oil pump motor speed according to speed change demand to ensure speed ratio response characteristics, thereby effectively solving at least one technical problem involved in the background technology.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] A method for controlling an electric oil pump of a continuously variable transmission of an electric vehicle comprises the following steps:

[0008] Step 1: After the vehicle starts, determine whether the hydraulic control unit of the continuously variable transmission has a pressure requirement through the electric oil pump controller. If not, execute step 2; if yes, execute step 3;

[0009] Step 2, determine whether the hydraulic control unit has a flow demand, if not, set the target speed of the electric oil pump to 0; if yes, execute step 3;

[0010] Step 3, calculating the target speed of the electric oil pump, specifically including:

[0011] Step 31, determining whether the vehicle operating condition is a steady-state condition or a transient condition, if it is a steady-state condition, executing step 32; if it is a transient condition, executing step 33;

[0012] Step 32, calculating the required electric oil pump speed according to the leakage of the hydraulic control unit, comparing the required electric oil pump speed with the minimum speed, and taking the larger of the two as the electric oil pump target speed;

[0013] Step 33, calculating the electric oil pump speed that satisfies the speed change response flow according to the speed ratio change rate of the continuously variable transmission, calculating the required electric oil pump speed according to the leakage of the hydraulic control unit, adding the two and comparing them with the minimum speed, and taking the larger one as the electric oil pump target speed;

[0014] Step 4: Control the electric oil pump of the continuously variable transmission of the electric vehicle according to the target speed of the electric oil pump.

[0015] As a preferred improvement of the present invention, a permanent magnet synchronous motor is used as the driving source of the electric oil pump.

[0016] As a preferred improvement of the present invention, the permanent magnet synchronous motor adopts a speed control mode.

[0017] As a preferred improvement of the present invention, in step 3, the minimum rotational speed is the minimum rotational speed required for the vane pump blades to centrifugally form a suction and pressure oil cavity obtained from experimental tests.

[0018] As a preferred improvement of the present invention, in step 32, when the continuously variable transmission is in a steady-state condition, the electric oil pump provides a minimum flow rate according to the leakage of the hydraulic control unit.

[0019] As a preferred improvement of the present invention, in step 33, the electric oil pump speed that satisfies the speed change response flow is calculated based on the speed ratio change rate of the continuously variable transmission, specifically comprising: first calculating the required flow of the master and driven pulley hydraulic cylinders based on the speed ratio change rate of the continuously variable transmission, and then calculating the electric oil pump speed that satisfies the speed change response flow based on the required flow.

[0020] The present invention also provides an electric oil pump control system for an electric vehicle continuously variable transmission, comprising:

[0021] A pressure judgment module is used to judge whether the hydraulic control unit of the continuously variable transmission has a pressure demand through the electric oil pump controller after the vehicle starts;

[0022] A flow determination module, used to determine whether the hydraulic control unit has a flow demand;

[0023] A speed calculation module is used to calculate the target speed of the electric oil pump;

[0024] The oil pump control module is used to control the electric oil pump of the continuously variable transmission of the electric vehicle according to the target speed of the electric oil pump.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. The motor of the electric oil pump in the present invention adopts a speed control mode, and the target speed can be set according to the flow demand, and the oil pump motor torque can also be controlled according to the pressure load of the hydraulic control unit, ensuring that the actual speed tracks the target speed;

[0027] 2. The present invention achieves precise control of the oil pump speed by using an electric oil pump to decouple the oil pump speed from the engine speed, and can save energy and ensure response characteristics as much as possible according to actual operation flow requirements;

[0028] 3. The present invention can adjust the oil pump speed in real time according to the flow demand, thereby reducing the flow loss of the hydraulic control unit;

[0029] 4. The present invention can calculate the oil pump motor speed according to the speed change demand, ensure the speed ratio response characteristics, and improve the speed ratio control response quality of the continuously variable transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0031] Figure 1 A flow chart of the control method of the electric oil pump of the continuously variable transmission of an electric vehicle provided by the present invention;

[0032] Figure 2 This is a structural block diagram of the electric oil pump control system of the continuously variable transmission of an electric vehicle provided by the present invention. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0035] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0036] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" 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 or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0038] like Figure 1 As shown, the present invention provides a method for controlling an electric oil pump of a continuously variable transmission of an electric vehicle, comprising the following steps:

[0039] Step 1: After the vehicle starts, determine whether the hydraulic control unit of the continuously variable transmission has a pressure requirement through the electric oil pump controller. If not, execute step 2; if yes, execute step 3;

[0040] Step 2, determine whether the hydraulic control unit has a flow demand, if not, set the target speed of the electric oil pump to 0; if yes, execute step 3;

[0041] Specifically, after determining that there is no pressure demand, it is further determined whether the hydraulic control unit has a flow demand. When there is neither pressure demand nor flow demand, the target speed of the electric oil pump is set to 0 to reduce the power loss of the hydraulic control unit. When one of the pressure and flow exists, the target speed of the electric oil pump is set to greater than 0, and then adjusted according to whether the vehicle operating condition is a transient condition or a steady-state condition.

[0042] Step 3, calculating the target speed of the electric oil pump, specifically including:

[0043] Step 31, determining whether the vehicle operating condition is a steady-state condition or a transient condition, if it is a steady-state condition, executing step 32; if it is a transient condition, executing step 33;

[0044] Step 32, calculating the required speed of the electric oil pump according to the leakage of the hydraulic control unit, and then comparing it with the minimum speed required for the vane pump blades to centrifugally form a suction and pressure oil cavity obtained from the test, and taking the larger of the two as the target speed of the electric oil pump under steady-state conditions;

[0045] In this step, when the continuously variable transmission is in a steady-state condition, the electric oil pump provides a minimum flow rate according to the leakage of the hydraulic control unit.

[0046] Step 33, first calculate the required flow of the master and slave pulley hydraulic cylinders according to the speed ratio change rate of the continuously variable transmission, then calculate the electric oil pump speed that meets the speed change response flow according to the flow requirement; then calculate the required electric oil pump speed according to the leakage of the hydraulic control unit. Add the electric oil pump speed required for the speed ratio change and the electric oil pump speed required to meet the leakage, and compare them with the minimum speed required for the vane pump blades to centrifugally form a suction and pressure oil cavity obtained by the test, and take the larger one as the target speed of the electric oil pump under transient conditions.

[0047] Step 4: Control the electric oil pump of the continuously variable transmission of the electric vehicle according to the target speed of the electric oil pump.

[0048] In the specific implementation, a permanent magnet synchronous motor is used as the driving source of the electric oil pump. The permanent magnet synchronous motor adopts a speed control mode, sets the target speed according to the flow demand, and can also control the oil pump motor torque according to the pressure load of the hydraulic control unit to ensure that the actual speed tracks the target speed.

[0049] like Figure 2As shown, the present invention also provides an electric oil pump control system for a continuously variable transmission of an electric vehicle, comprising a pressure judgment module 1, a flow judgment module 2, a speed calculation module 3 and an oil pump control module 4. The pressure judgment module 1 is used to judge whether the hydraulic control unit of the continuously variable transmission has a pressure demand through the electric oil pump controller after the vehicle starts; the flow judgment module 2 is used to judge whether the hydraulic control unit has a flow demand; the speed calculation module 3 is used to calculate the target speed of the electric oil pump; the oil pump control module 4 is used to control the electric oil pump of the continuously variable transmission of the electric vehicle according to the target speed of the electric oil pump.

[0050] The beneficial effects of the present invention are as follows:

[0051] 1. The motor of the electric oil pump in the present invention adopts a speed control mode, and the target speed can be set according to the flow demand, and the oil pump motor torque can also be controlled according to the pressure load of the hydraulic control unit, ensuring that the actual speed tracks the target speed;

[0052] 2. The present invention achieves precise control of the oil pump speed by using an electric oil pump to decouple the oil pump speed from the engine speed, and can save energy and ensure response characteristics as much as possible according to actual operation flow requirements;

[0053] 3. The present invention can adjust the oil pump speed in real time according to the flow demand, thereby reducing the flow loss of the hydraulic control unit;

[0054] 4. The present invention can calculate the oil pump motor speed according to the speed change demand, ensure the speed ratio response characteristics, and improve the speed ratio control response quality of the continuously variable transmission.

[0055] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for controlling an electric oil pump of a continuously variable transmission of an electric vehicle, characterized in that: The following steps are involved: Step 1: After the vehicle starts, determine whether the hydraulic control unit of the continuously variable transmission has a pressure requirement through the electric oil pump controller. If not, execute step 2; if yes, execute step 3; Step 2, determine whether the hydraulic control unit has a flow demand, if not, set the target speed of the electric oil pump to 0; If yes, go to step 3; Step 3, calculating the target speed of the electric oil pump, specifically including: Step 31, determining whether the vehicle operating condition is a steady-state condition or a transient condition, if it is a steady-state condition, executing step 32; if it is a transient condition, executing step 33; Step 32, calculating the required electric oil pump speed according to the leakage of the hydraulic control unit, comparing the required electric oil pump speed with the minimum speed, and taking the larger of the required electric oil pump speed and the minimum speed as the target speed of the electric oil pump; the minimum speed is the minimum speed required for the vane pump blades to centrifugally form a suction and pressure oil cavity obtained by experimental testing; Step 33, calculating the electric oil pump speed that meets the speed change response flow rate according to the speed ratio change rate of the continuously variable transmission, calculating the required electric oil pump speed according to the leakage amount of the hydraulic control unit, adding the electric oil pump speed that meets the speed change response flow rate and the required electric oil pump speed calculated according to the leakage amount of the hydraulic control unit, and comparing them with the minimum speed, and taking the larger one as the electric oil pump target speed; Step 4: Control the electric oil pump of the continuously variable transmission of the electric vehicle according to the target speed of the electric oil pump.

2. The method for controlling an electric oil pump of a continuously variable transmission of an electric vehicle according to claim 1, characterized in that: A permanent magnet synchronous motor is used as the driving source of the electric oil pump.

3. The method for controlling an electric oil pump of a continuously variable transmission of an electric vehicle according to claim 2, characterized in that: The permanent magnet synchronous motor adopts a speed control mode.

4. The method for controlling an electric oil pump of a continuously variable transmission of an electric vehicle according to claim 1, characterized in that: In step 32, when the continuously variable transmission is in a steady-state condition, the electric oil pump provides a minimum flow rate according to the leakage of the hydraulic control unit.

5. The method for controlling an electric oil pump of a continuously variable transmission of an electric vehicle according to claim 1, characterized in that: In step 33, the electric oil pump speed that meets the speed change response flow is calculated based on the speed ratio change rate of the continuously variable transmission, specifically including: first calculating the required flow of the master and slave pulley hydraulic cylinders based on the speed ratio change rate of the continuously variable transmission, and then calculating the electric oil pump speed that meets the speed change response flow based on the required flow.

6. An electric oil pump control system for a continuously variable transmission of an electric vehicle implementing the method described in any one of claims 1 to 5, characterized in that: include: A pressure judgment module is used to judge whether the hydraulic control unit of the continuously variable transmission has a pressure demand through the electric oil pump controller after the vehicle starts; A flow determination module, used to determine whether the hydraulic control unit has a flow demand; A speed calculation module is used to calculate the target speed of the electric oil pump; The oil pump control module is used to control the electric oil pump of the continuously variable transmission of the electric vehicle according to the target speed of the electric oil pump.

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