Dual pump hydraulic system for automatic transmission and control method thereof

Abstract

The application discloses an automatic transmission double-pump hydraulic system and a control method thereof, and solves the problem that different required pressure oils of different modules in an existing agricultural machinery automatic transmission hydraulic system are difficult to meet the requirements through single oil pump twice pressure reduction, and specifically comprises a transmission working hydraulic system, a transmission driving brake hydraulic system and an oil tank; the transmission working hydraulic system comprises a first oil inlet oil path, a first gear pump, a safety valve, a first oil filter, a main pressure regulating overflow valve and an oil cooler, and a plurality of clutch execution units and a parking brake execution unit are arranged in front of the main pressure regulating overflow valve. The application adopts a double-pump design, provides pressure oils with different oil pressure values and flow rates, and the pressure oils are greatly different, so that the working states of the two systems are stable and reliable; the double pumps share an oil pool in the bottom of a transmission shell, and the tank space is saved; the oil in the oil pool is circulated and supplemented through a plurality of oil return oil paths, so that the oil suction amount of the double pumps can be met, and the oil pump is prevented from being sucked empty.

Description

Technical Field

[0001] This invention relates to a hydraulic control system for a transmission, specifically to a dual-pump hydraulic system for an automatic transmission and its control method. Background Technology

[0002] In the automatic transmissions of large agricultural harvesting machinery, the hydraulic control system is the core module enabling automatic gear shifting. The hydraulic control system of an automatic transmission for agricultural harvesting machinery mainly consists of two parts: the transmission working hydraulic system and the transmission service brake hydraulic system. The oil pressure of the transmission working hydraulic system is around 30 bar, and the flow rate is around 30 L / min; while the oil pressure of the transmission service brake hydraulic system is around 70 bar, and the flow rate is around 16 L / min. If a single gear pump is used to supply pressurized oil, and a pressure drop of 40 bar is achieved through two stages of pressure reduction, while maintaining the required oil flow rates for both hydraulic systems without significant fluctuations, it is practically difficult to achieve with a single pump.

[0003] Chinese patent CN111425593A discloses a 6-speed hydraulic system for agricultural machinery transmissions. However, for hydraulic systems of agricultural harvesting machinery, multi-speed transmissions do not have many application scenarios. A 2-speed design can already meet the needs of harvesting crops: 1st speed for field work mode at 0-15km / h; 2nd speed for highway transfer mode at 0-35km / h. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of existing agricultural machinery automatic transmission hydraulic systems, which have different pressure requirements for the transmission working system and the service braking system, making it difficult to meet the working conditions of their respective hydraulic modules through two pressure reductions by a single pump, or the existing 6-speed agricultural machinery transmission hydraulic system being unable to meet the actual application scenarios of agricultural harvesting machinery. The invention provides an automatic transmission dual-pump hydraulic system and its control method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An automatic transmission dual-pump hydraulic system is characterized by comprising: a transmission working hydraulic system, a transmission service brake hydraulic system, and an oil tank;

[0007] The transmission hydraulic system includes: a first oil inlet circuit, a first gear pump that draws oil from the oil tank into the first oil inlet circuit, a first oil filter, a main pressure regulating relief valve and an oil cooler connected in series after the first gear pump in the first oil inlet circuit, and a return oil circuit connected to the oil tank.

[0008] It also includes a safety valve that connects the oil inlet to the first oil inlet circuit between the oil inlet and the first gear pump and the first oil filter, and connects the oil outlet to the return oil circuit.

[0009] It also includes multiple clutch actuators and a parking brake actuator, which are located between the first oil inlet circuit and the oil return circuit in front of the main pressure regulating relief valve; the parking brake actuator includes a control valve, a shut-off valve, a parking brake piston connected in sequence, and a parking pressure sensor located on the oil circuit between the shut-off valve and the parking brake piston; the multiple clutch actuators include a low-gear clutch actuator D1, a high-gear clutch actuator D2, and a differential clutch actuator D3;

[0010] The transmission service brake hydraulic system includes: a second oil inlet circuit; a second gear pump that draws oil from the return oil circuit or the oil tank into the second oil inlet circuit; a second oil filter and a one-way valve connected in series on the second oil inlet circuit; and a service brake valve assembly installed between the second oil inlet circuit and the return oil circuit after the one-way valve. The service brake valve assembly includes a left brake valve and a right brake valve respectively connected between the second oil inlet circuit and the return oil circuit after the one-way valve. The outlet of the left brake valve is connected to a left brake piston, and the outlet of the right brake valve is connected to a right brake piston.

[0011] It also includes a relief valve that connects the oil inlet to the second oil inlet circuit between the oil inlet and the second oil filter and the check valve. The oil outlet of the relief valve is connected to an auxiliary pressure regulating valve. The oil outlet of the auxiliary pressure regulating valve is connected to the return oil circuit, and the oil outlet is connected to the second oil inlet circuit between the check valve and the accumulator.

[0012] Furthermore, the low-gear clutch actuator D1, high-gear clutch actuator D2, and differential clutch actuator D3 have the same structure, each including a combined solenoid valve and a piston.

[0013] The combined solenoid valve is a cartridge valve that is integrated and connected internally via oil passages. It includes a solenoid valve control slide valve, a solenoid valve main valve, a throttle, an oil inlet, an oil outlet, and an oil outlet. The oil inlet is connected to the first oil inlet circuit, the oil outlet is connected to the return oil circuit, and the oil outlet is connected to the piston's oil inlet.

[0014] When the combined solenoid valve is de-energized, the solenoid valve control slide valve is in the conducting state, the solenoid valve main valve is in the closed state, and the pressurized oil enters from the inlet, is throttled by the throttle, and flows back to the return oil circuit from the outlet through the solenoid valve control slide valve, and the piston has no pressure. When the combined solenoid valve is energized, the solenoid valve control slide valve is in the closed state, the solenoid valve main valve is opened under the action of hydraulic pressure, and the pressurized oil enters the piston through the outlet, and the piston moves.

[0015] Furthermore, an accumulator, a temperature sensor, and a pressure sensor are sequentially installed on the first oil inlet line between the first oil filter and the main pressure regulating relief valve;

[0016] An accumulator is installed on the second oil inlet line between the one-way valve and the service brake valve assembly.

[0017] Furthermore, the first oil filter and the second oil filter have bypass functions.

[0018] Furthermore, the opening pressure of the safety valve is 35 bar.

[0019] Furthermore, the first gear pump provides pressurized oil with a pressure greater than 30 bar and a flow rate greater than 30 L / min; the second gear pump provides pressurized oil with a pressure greater than 70 bar and a flow rate greater than 16 L / min.

[0020] Furthermore, the left brake valve and the right brake valve are three-position four-way spool valves.

[0021] Furthermore, the drain port of the overflow valve is connected to the return oil circuit.

[0022] Meanwhile, the present invention also provides a control method for the above-mentioned dual-pump hydraulic system of an automatic transmission, which is characterized by including the following steps:

[0023] S1, the vehicle is powered on and ready to start. The control valve is energized, its oil circuit is opened, and the pressurized oil pushes the piston to move against the spring force of the parking brake, releasing the parking brake lock.

[0024] S2, the combined solenoid valve in the low-gear clutch actuator D1 is energized and in the conducting position, the piston of the low-gear clutch actuator D1 is filled with oil, the low-gear clutch is engaged, the transmission is in 1st gear, and the vehicle moves in 1st gear; the 1st gear is the low gear of the transmission.

[0025] S3 determines whether the shifting conditions are met based on the vehicle's usage.

[0026] If yes, proceed to step 4; otherwise, proceed to step S5.

[0027] S4, gear shift;

[0028] S4.1, the combined solenoid valve of the low gear clutch actuator D1 is de-energized, and the combined solenoid valve of the high gear clutch actuator D2 is energized, so that the vehicle can travel in 2nd gear.

[0029] S4.2, Determine if there is a stuck vehicle signal; if yes, proceed to S4.3; if no, proceed to S4.5.

[0030] S4.3, the combined solenoid valve of the high-gear clutch actuator D2 is de-energized, the combined solenoid valve of the low-gear clutch actuator D1 is energized, and the transmission downshifts to 1st gear;

[0031] S4.4, the combined solenoid valve of the differential clutch actuator unit D3 is energized, the differential clutch is engaged, and the two half shafts move at the same speed, allowing the vehicle to get out of trouble. After the vehicle is out of trouble, the combined solenoid valve of the differential clutch actuator unit D3 is de-energized, and then returns to S2.

[0032] S4.5, the transmission remains in 2nd gear, allowing the vehicle to travel in 2nd gear. When it is time to stop, the combination solenoid valve of the high gear clutch actuator D2 is de-energized, the transmission is in neutral, and then S6 is executed.

[0033] S5: Keep the transmission in 1st gear to keep the vehicle moving in 1st gear, and immediately check if there is a stuck signal; if there is, proceed to S6; if not, proceed to S7.

[0034] S6, the combined solenoid valve of the differential clutch actuator unit D3 is energized, the differential clutch is engaged, and the two half shafts move at the same speed, allowing the vehicle to get out of trouble. After the vehicle is out of trouble, the combined solenoid valve of the differential clutch actuator unit D3 is de-energized, and then S7 is executed.

[0035] S7, the vehicle continues to travel in 1st gear until it needs to stop. The combination solenoid valve of the low gear clutch actuator D1 is de-energized, the transmission is in neutral, and then S8 is executed.

[0036] S8 de-energizes the control valve, disconnecting its oil circuit, resetting the piston, locking the parking brake, and completing the control of the automatic transmission's dual-pump hydraulic system.

[0037] The beneficial effects of this invention are:

[0038] 1) The present invention discloses an automatic transmission dual-pump hydraulic system, which adopts a dual-pump design to provide different pressure oil to the transmission working system and the service braking system, which have different and significantly different required oil pressure values ​​and flow rates. The provided pressure oil flow rate and oil pressure do not fluctuate significantly, ensuring that the working state of the two systems is stable and reliable.

[0039] 2) In the transmission hydraulic system, a pilot proportional control assembly solenoid valve is used. The small spool valve controlled by the current drives the working spool valve to fill and release oil to the piston. The small valve core is controlled by a small current. The hydraulic oil itself enters the working valve core drive chamber by its own pressure. The small valve core then controls the working valve, which can amplify the execution capability of the small current.

[0040] 3) The present invention discloses an automatic transmission dual-pump hydraulic system that uses a combination of a shut-off valve and a proportional solenoid valve in the transmission working system to ensure the safe and normal operation of the transmission parking brake system.

[0041] 4) The present invention provides an automatic transmission dual-pump hydraulic system that uses a differential control valve. When a signal is received that the vehicle is stuck, the transmission can open the differential control valve to lock both wheels and help the vehicle get out of trouble.

[0042] 5) In the service braking system, a three-position four-way proportional solenoid valve that is linearly related to the depth of the foot pedal is used to control the connection and unloading of the service brake oil circuit, so that the oil pressure is proportional to the friction torque of the brake, and the braking torque is indirectly linearly controlled. That is, the braking force is linearly controlled according to the driver's intention, so that the vehicle decelerates and stops, and the braking process is smooth.

[0043] 6) In the automatic transmission dual-pump hydraulic system of the present invention, the two pumps working share the bottom oil sump inside the transmission housing, which saves the space of the housing; the oil in the oil sump is replenished by multiple return oil circuits, which can meet the oil suction volume of the two pumps and at the same time prevent the oil pumps from sucking in air. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of an embodiment of a dual-pump hydraulic system for an automatic transmission according to the present invention;

[0045] Figure 2 This is a schematic diagram of the combined solenoid valve in an embodiment of an automatic transmission dual-pump hydraulic system of the present invention;

[0046] Figure 3 This is a schematic diagram of the shifting logic of a control method for a dual-pump hydraulic system of an automatic transmission according to the present invention.

[0047] Figure 4 This is a schematic diagram showing the on / off state of each control valve in different gears of a control method for a dual-pump hydraulic system of an automatic transmission according to the present invention.

[0048] Icon labels:

[0049] 1-Transmission working hydraulic system, 2-Transmission service brake hydraulic system, 3-Oil tank, 4-First gear pump, 5-First oil inlet circuit, 6-Safety valve, 7-First oil filter, 8-Accumulator, 9-Temperature sensor, 10-Pressure sensor, 11-Main pressure regulating relief valve, 12-Combination solenoid valve, 13-Control valve, 14-Shut-off valve, 15-Parking pressure sensor, 16-Parking brake piston, 17-Piston, 18-Oil cooler, 19-Return oil circuit, 20-Second gear pump, 21-Second gear pump Oil inlet circuit, 22-Second oil filter, 23-Relief valve, 24-Auxiliary pressure regulating valve, 25-Check valve, 26-Accumulator, 27-Service brake valve assembly, 28-Left brake valve, 29-Right brake valve, 30-Right brake piston, 31-Left brake piston, 32-Solenoid valve control spool valve, 33-Solenoid valve main valve, 34-Throttle, 35-Inlet port, 36-Outlet port, 37-Outlet port, D1-Low gear clutch actuator, D2-High gear clutch actuator, D3-Differential clutch actuator. Detailed Implementation

[0050] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] An embodiment of the present invention provides a dual-pump hydraulic system for an automatic transmission, such as... Figure 1 As shown, it includes the transmission working hydraulic system 1, the transmission service brake hydraulic system 2, and the oil tank 3;

[0052] The transmission hydraulic system 1 includes an oil tank 3, a first gear pump 4, a first oil inlet circuit 5, a safety valve 6, a first oil filter 7, an accumulator 8, a temperature sensor 9, a pressure sensor 10, a main pressure regulating relief valve 11, an oil cooler 18, a return oil circuit 19, a low-gear clutch actuator D1, a high-gear clutch actuator D2, a differential clutch actuator D3, and a parking brake actuator.

[0053] The first oil filter 7, the main pressure regulating relief valve 11, and the oil cooler 18 are connected in series in the first oil inlet circuit 5 after the first gear pump 4; the oil inlet of the safety valve 6 is connected to the first oil inlet circuit 5 between the first gear pump 4 and the first oil filter 7, and the oil outlet is connected to the return oil circuit 19. The opening pressure is 35 Bar. When the oil pressure of the first oil filter 7 increases to 35 Bar due to system impurities, the safety valve 6 opens. At this time, the pressurized oil flows back to the oil tank 3 through the safety valve 6 and the return oil circuit 19, protecting the first gear pump 4 from damage.

[0054] Accumulator 8, temperature sensor 9, and pressure sensor 10 are sequentially installed on the first oil inlet circuit 5 between the first oil filter 7 and the main pressure regulating overflow valve 11. Accumulator 8 plays a role in stabilizing pressure, stabilizing system pressure when the transmission working hydraulic system is open, and compensating for oil flow to prevent system pressure fluctuations from causing temporary failure of other oil circuits that are working at the same time. Temperature sensor 9 and pressure sensor 10 respectively detect the temperature and pressure of the pressure oil entering each clutch actuator unit and parking brake actuator unit.

[0055] The inlet of the main pressure regulating relief valve 11 is connected to the first oil inlet circuit 5, the outlet is connected to the return oil circuit 19, and the outlet is connected to an oil cooler 18. When the pressure of the oil is high, the main pressure regulating relief valve 11 opens, the oil cooler 18 is connected to the first oil inlet circuit 5, the pressure oil enters from the inlet of the main pressure regulating relief valve 11, flows out through the outlet to the oil cooler 18, and flows into the return oil circuit 19 after cooling.

[0056] Each clutch actuator and parking brake actuator is installed on the first oil inlet circuit 5 between the pressure sensor 10 and the main pressure regulating relief valve 11; the first gear pump 4 draws oil from the oil tank 3, generating pressurized oil with an oil pressure greater than 30 bar and a flow rate greater than 30 L / min. The pressurized oil enters the first oil filter 7 through the first oil inlet circuit 5. The first oil filter 7 has a bypass function to prevent the working device from being unable to supply oil if the first oil filter 7 is blocked; the pressurized oil flowing out of the first oil filter 7 flows to the main pressure regulating relief valve 11, where the oil pressure stabilizes at 30 Bar, and then flows into each clutch actuator and parking brake actuator.

[0057] The parking brake actuator unit includes a control valve 13, a shut-off valve 14, a parking pressure sensor 15, and a parking brake piston 16. The inlet of the control valve 13 is connected to the first oil inlet circuit 5, the outlet is connected to the inlet of the shut-off valve 14, and the drain port is connected to the return oil circuit 19. The outlet of the shut-off valve 14 is connected to the inlet of the piston 16. A parking pressure sensor 15 is installed on the oil circuit between the piston 16 and the shut-off valve 14. The shut-off valve 14 is also energized and conducting after the control valve 13 is energized. When the system is suddenly de-energized, the shut-off valve 14 is disconnected to prevent backflow of pressure oil from the parking brake piston 16 and ensure that the parking brake is released. The parking pressure sensor 15 constantly monitors the oil circuit pressure of the parking brake actuator unit. If the oil pressure of the parking brake piston 16 fails to reach the preset value, the parking brake control valve 13 will be energized at this time to replenish the oil circuit pressure.

[0058] The low-gear clutch actuator D1, high-gear clutch actuator D2, and differential clutch actuator D3 have the same structure, each consisting of an assembly solenoid valve 12 and a piston 17.

[0059] like Figure 2 As shown, the assembled solenoid valve 12 is an assembled solenoid valve with pilot proportional control: the working spool valve is driven by a current-controlled small spool valve to realize the filling and discharging of oil to the piston. It includes a solenoid valve control spool valve 32, a solenoid valve main valve 33, a throttle valve 34, an oil inlet 35, an oil outlet 36 and an oil outlet 37. The oil inlet 35 is connected to the first oil inlet circuit 5, the oil outlet 36 is connected to the return oil circuit 19, and the oil outlet 37 is connected to the oil inlet of the piston 17.

[0060] When the solenoid valve 12 is de-energized, the solenoid valve controls the slide valve 32 to be in position A. Pressurized oil enters from the inlet 35, is throttled by the throttle valve 34, and flows back to the return oil circuit 19 through the outlet 36 from the control valve at position A. Since the oil circuit is unobstructed, there is no pressure at point a. At this time, the solenoid valve main valve 33 is in position C, and the outlet 37 between the pressurized oil and the piston is closed, so the piston has no pressure. When the solenoid valve 12 is energized, the solenoid valve controls the slide valve 32 to be in position B under the action of electromagnetic force. The pressurized oil is disconnected, and the pressure at point a is the oil pressure. The solenoid valve main valve 33 is in position D under the action of hydraulic pressure. The solenoid valve main valve 33 is open, and the pressurized oil enters the piston through the outlet 37, causing the piston to move.

[0061] The transmission service brake hydraulic system 2 includes a second gear pump 20, a second oil inlet circuit 21, an overflow valve 23, an auxiliary pressure regulating valve 24, a second oil filter 22, a check valve 25, a service brake valve group 27 connected in series on the second oil inlet circuit 21, and an accumulator 26 installed on the second oil inlet circuit 21 between the check valve 25 and the service brake valve group 27.

[0062] One-way valve 25 is used to prevent oil from flowing back due to inertia after the service brake valve group 27 is closed; accumulator 26 is used to prevent oil pressure drop and insufficient pressure oil flow after the service brake valve group 28 is opened.

[0063] The inlet of the overflow valve 23 is connected to the second oil inlet circuit 21 between the second oil filter 22 and the check valve 25, the outlet is connected to the inlet of the auxiliary pressure regulating valve 24, and the drain port is connected to the return oil circuit 19; the outlet of the auxiliary pressure regulating valve 24 is connected to the second oil inlet circuit 21 between the check valve 25 and the accumulator 26, and the drain port is connected to the return oil circuit 19; since the service brake valve assembly 27 is normally closed, the drain port of the overflow valve 23 will always have a large flow and a certain pressure. Therefore, connecting the drain port of the overflow valve 23 to the return oil circuit 19 can supplement the oil flow, which is beneficial for the first gear pump 4 and the second gear pump 20 to draw oil and avoid the oil pump from drawing dry.

[0064] The second gear pump 20 draws oil from the return oil line 19 or the oil tank 3, generating pressurized oil with a pressure greater than 70 bar and a flow rate greater than 16 L / min. The pressurized oil enters the second oil filter 22 through the second oil inlet line 21. The second oil filter 23 has a bypass function to prevent the working device from being unable to supply oil if the second oil filter 22 is blocked. The pressurized oil flowing out of the second oil filter 22 flows through the overflow valve 24, and the oil pressure is stabilized at 70 Bar. It then flows into the service brake valve group 27 through the accumulator 26.

[0065] The service brake valve assembly 27 includes a left brake valve 28 and a right brake valve 29. The left brake valve 28 and the right brake valve 29 are three-position four-way spool valves linearly related to the pedal depth. The outlet of the left brake valve 28 is connected to a left brake piston 31, and the outlet of the right brake valve 29 is connected to a right brake piston 30. The inlets of the left brake valve 28 and the right brake valve 29 are connected to the second oil inlet circuit 21. The outlets of the left brake valve 28 and the right brake valve 29 are respectively connected to the return oil circuit 19 to ensure that the pressure in the return oil circuit is standard atmospheric pressure or negative pressure, so that the left brake piston 31 and the right brake piston 30 can return to their positions quickly.

[0066] When the vehicle is in motion, the left brake valve 28 and the right brake valve 29 are connected to the return oil circuit 19, ensuring that the left brake piston 31 and the right brake piston 30 are in an unobstructed state and can automatically return to their original positions. When the service brake is required, the foot pedal is pressed, and the left brake valve 28 and the right brake valve 29 are energized and switched. Under the action of electromagnetic force, the left brake valve 28 and the right brake valve 29 overcome the spring force and are in the position where the pressure oil is connected to the left brake piston 31 and the right brake piston 30. The left brake piston 31 and the right brake piston 30 are filled with oil to meet the service brake requirements.

[0067] Furthermore, this invention also provides a control method based on the aforementioned dual-pump hydraulic system for automatic transmissions, referring to... Figures 3-4 This includes the following steps:

[0068] S1, the vehicle is powered on and ready to start. Control valve 13 is energized, its oil circuit is opened, and the pressurized oil pushes piston 16 to move against the spring force of the parking brake, releasing the parking brake lock.

[0069] S2, the combined solenoid valve 12 in the low gear clutch actuator D1 is energized and in the conducting position, the piston 17 of the low gear clutch actuator D1 is filled with oil, the low gear clutch is engaged, the transmission is in 1st gear, and the vehicle moves in 1st gear; the 1st gear is the low gear of the transmission.

[0070] S3 determines whether the shifting conditions are met based on the vehicle's usage.

[0071] If yes, proceed to step 4; otherwise, proceed to step S5.

[0072] S4, gear shift;

[0073] S4.1, the combined solenoid valve 12 of the low gear clutch actuator D1 is de-energized, and the combined solenoid valve 12 of the high gear clutch actuator D2 is energized, so that the vehicle can travel in 2nd gear.

[0074] S4.2, Determine if there is a stuck vehicle signal; if yes, proceed to S4.3; if no, proceed to S4.5.

[0075] S4.3, the combined solenoid valve 12 of the high-gear clutch actuator D2 is de-energized, the combined solenoid valve 12 of the low-gear clutch actuator D1 is energized, and the transmission downshifts to 1st gear;

[0076] S4.4, the combined solenoid valve 12 of the differential clutch actuator unit D3 is energized, the differential clutch is engaged, and the two half shafts move at the same speed, allowing the vehicle to get out of trouble. After the vehicle is out of trouble, the combined solenoid valve 12 of the differential clutch actuator unit D3 is de-energized, and then returns to S2.

[0077] S4.5, the transmission remains in 2nd gear, allowing the vehicle to travel in 2nd gear. When it is necessary to stop, the combination solenoid valve 12 of the high gear clutch actuator D2 is de-energized, the transmission is in neutral, and then S6 is executed.

[0078] S5: Keep the transmission in 1st gear to keep the vehicle moving in 1st gear, and immediately check if there is a stuck signal; if there is, proceed to S6; if not, proceed to S7.

[0079] S6, the combined solenoid valve 12 of the differential clutch actuator unit D3 is energized, the differential clutch is engaged, and the two half shafts move at the same speed, allowing the vehicle to get out of trouble. After the vehicle is out of trouble, the combined solenoid valve 12 of the differential clutch actuator unit D3 is de-energized, and then S7 is executed.

[0080] S7, the vehicle continues to travel in 1st gear until it needs to stop. When the low gear clutch actuator D1's combination solenoid valve 12 is de-energized, the transmission is in neutral, and then S8 is executed.

[0081] S8 de-energizes control valve 13, disconnecting its oil circuit, resetting piston 16, locking the parking brake, and completing the control of the dual-pump hydraulic system of the automatic transmission.

Claims

1. A dual-pump hydraulic system for an automatic transmission, characterized in that, include: The transmission working hydraulic system (1), the transmission service brake hydraulic system (2), and the oil tank (3); The transmission hydraulic system (1) includes: a first oil inlet circuit (5), a first gear pump (4) that draws oil from the oil tank (3) into the first oil inlet circuit (5), a first oil filter (7), a main pressure regulating relief valve (11) and an oil cooler (18) connected in series after the first gear pump (4) in the first oil inlet circuit (5), and a return oil circuit (19) connected to the oil tank (3); It also includes a safety valve (6) that connects the oil inlet to the first oil inlet circuit (5) between the oil inlet and the first gear pump (4) and the first oil filter (7), and connects the oil outlet to the return oil circuit (19); It also includes multiple clutch actuators and a parking brake actuator, which are located between the first oil inlet circuit (5) and the oil return circuit (19) in front of the main pressure regulating overflow valve (11); the parking brake actuator includes a control valve (13), a shut-off valve (14), a parking brake piston (16) connected in sequence, and a parking pressure sensor (15) located on the oil line between the shut-off valve (14) and the parking brake piston (16); the multiple clutch actuators include a low-gear clutch actuator D1, a high-gear clutch actuator D2, and a differential clutch actuator D3; The transmission service brake hydraulic system (2) includes: a second oil inlet circuit (21), a second gear pump (20) that draws oil from the return oil circuit (19) or the oil tank (3) into the second oil inlet circuit (21), a second oil filter (22) and a check valve (25) connected in series on the second oil inlet circuit (21), and a service brake valve assembly (27) installed between the second oil inlet circuit (21) and the return oil circuit (19) after the check valve (25); the service brake valve assembly (27) includes a left brake valve (28) and a right brake valve (29) respectively connected between the second oil inlet circuit (21) and the return oil circuit (19) after the check valve (25), wherein the outlet of the left brake valve (28) is connected to a left brake piston (31), and the outlet of the right brake valve (29) is connected to a right brake piston (30); It also includes an overflow valve (23) that connects the oil inlet to the second oil inlet circuit (21) between the oil inlet and the second oil filter (22) and the check valve (25). The oil outlet of the overflow valve (23) is connected to an auxiliary pressure regulating valve (24). The oil outlet of the auxiliary pressure regulating valve (24) is connected to the return oil circuit (19), and the oil outlet is connected to the second oil inlet circuit (21) between the check valve (25) and the accumulator (26).

2. The dual-pump hydraulic system for an automatic transmission according to claim 1, characterized in that: The low-gear clutch actuator D1, high-gear clutch actuator D2, and differential clutch actuator D3 have the same structure, each including a combined solenoid valve (12) and a piston (17). The combined solenoid valve (12) is a cartridge valve that is integrated and connected internally by oil passages. It includes a solenoid valve control slide valve (32), a solenoid valve main valve (33), a throttle (34), an oil inlet (35), an oil outlet (36), and an oil outlet (37). The oil inlet (35) is connected to the first oil inlet circuit (5), the oil outlet (36) is connected to the return oil circuit (19), and the oil outlet (37) is connected to the oil inlet of the piston (17).

3. The dual-pump hydraulic system for an automatic transmission according to claim 1, characterized in that: An accumulator (8), a temperature sensor (9), and a pressure sensor (10) are sequentially installed on the first oil inlet circuit (5) between the first oil filter (7) and the main pressure regulating overflow valve (11); An accumulator (26) is provided on the second oil inlet circuit (21) between the one-way valve (25) and the service brake valve group (27).

4. The dual-pump hydraulic system for an automatic transmission according to claim 1, characterized in that: The first oil filter (7) and the second oil filter (22) have bypass functions.

5. The dual-pump hydraulic system for an automatic transmission according to claim 1, characterized in that: The opening pressure of the safety valve (6) is 35 bar.

6. The dual-pump hydraulic system for an automatic transmission according to claim 1, characterized in that: The first gear pump (4) provides pressurized oil with a pressure greater than 30 bar and a flow rate greater than 30 L / min; the second gear pump (20) provides pressurized oil with a pressure greater than 70 bar and a flow rate greater than 16 L / min.

7. The dual-pump hydraulic system for an automatic transmission according to claim 1, characterized in that: The left brake valve (28) and the right brake valve (29) are three-position four-way spool valves.

8. The dual-pump hydraulic system for an automatic transmission according to claim 1, characterized in that: The drain port of the overflow valve (23) is connected to the return oil circuit (19).

9. A control method for a dual-pump hydraulic system of an automatic transmission according to any one of claims 1-8, characterized in that, Includes the following steps: S1, the vehicle is powered on and ready to start. The control valve (13) is energized, its oil circuit is open, and the pressurized oil pushes the piston (16) to move against the spring force of the parking brake and release the parking brake lock. S2, the combined solenoid valve (12) in the low gear clutch actuator D1 is energized and in the conducting position, the piston (17) of the low gear clutch actuator D1 is filled with oil, the low gear clutch is engaged, the transmission is in 1st gear, and the vehicle travels in 1st gear; the 1st gear is the low gear of the transmission. S3 determines whether the shifting conditions are met based on the vehicle's usage. If yes, proceed to step 4; otherwise, proceed to step S5. S4, gear shift; S4.1, the combined solenoid valve (12) of the low gear clutch actuator D1 is de-energized, and the combined solenoid valve (12) of the high gear clutch actuator D2 is energized, so that the vehicle can travel in 2nd gear. S4.2, Determine if there is a stuck vehicle signal; if yes, proceed to S4.3; if no, proceed to S4.

5. S4.3, the combined solenoid valve (12) of the high gear clutch actuator D2 is de-energized, the combined solenoid valve (12) of the low gear clutch actuator D1 is energized, and the transmission is downshifted to 1st gear; S4.4, the combined solenoid valve (12) of the differential clutch actuator unit D3 is energized, the differential clutch is engaged, and the two half shafts move at the same speed, the vehicle gets out of trouble, and after the vehicle gets out of trouble, the combined solenoid valve (12) of the differential clutch actuator unit D3 is de-energized, and then returns to S2. S4.5, the transmission remains in 2nd gear, and the vehicle travels in 2nd gear. When it is necessary to stop, the combination solenoid valve (12) of the high gear clutch actuator D2 is de-energized, the transmission is in neutral, and then S6 is executed. S5: Keep the transmission in 1st gear to keep the vehicle moving in 1st gear, and immediately check if there is a stuck signal; if there is, proceed to S6; if not, proceed to S7. S6, the combined solenoid valve (12) of the differential clutch actuator unit D3 is energized, the differential clutch is engaged, and the two half shafts move at the same speed, the vehicle gets out of trouble. After the vehicle gets out of trouble, the combined solenoid valve (12) of the differential clutch actuator unit D3 is de-energized, and then S7 is executed. S7, the vehicle continues to travel in 1st gear until it needs to stop. The combination solenoid valve (12) of the low gear clutch actuator D1 is de-energized, the transmission is in neutral, and then S8 is executed. S8, de-energize the control valve (13) to disconnect its oil circuit, reset the piston (16), lock the parking brake, and complete the control of the dual-pump hydraulic system of the automatic transmission.

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