A hydraulic control system for a low-horsepower tractor

Abstract

The present invention belongs to the technical field of fluid working systems, and provides a hydraulic control system for a small horsepower tractor. A hydraulic control system for a small horsepower tractor, each clutch pressure control mechanism is provided with a clutch solenoid valve, each clutch solenoid valve is provided with a corresponding accumulator, and the hydraulic oil needs to pass through the accumulator corresponding to the clutch solenoid valve before flowing into the clutch solenoid valve; the clutch solenoid valve directly drives the execution structure to provide hydraulic oil. Each clutch solenoid valve is provided with a corresponding accumulator, and the accumulator provides power to the gearbox pressure system; the accumulator absorbs the pressure shock when the hydraulic system shifts gears and eliminates pulsation; the accumulator has a fast oil discharge characteristic, which can reduce the gearbox shift response time, avoid frustration, and improve driving comfort; the clutch solenoid valve directly drives to provide the execution structure hydraulic pressure, reduce the control valve components, and improve the control accuracy and response speed.

Description

Technical Field

[0001] The invention relates to the technical field of fluid working systems, and in particular provides a hydraulic control system for a small horsepower tractor. Background Art

[0002] With the accelerated advancement of agricultural intensification in China, the automation and intelligence of agricultural machinery are developing rapidly to meet the needs of agricultural development. The annual sales volume of domestic tractors has reached about 400,000 units, but the proportion of domestic tractors equipped with automatic transmissions is almost zero. High-end tractors equipped with automatic transmissions are basically all imported. At present, the transmissions of domestic tractors are mainly manual, and there has been no breakthrough in automatic transmission technology. In developed countries abroad, tractors basically all use automatic transmissions, and technically they basically use continuously variable transmission and power shift automatic transmission technology. The continuously variable transmission technology has relatively high operating efficiency and relatively high cost, making it more suitable for high-horsepower tractors that are not sensitive to price; the power shift performance is weaker than the continuously variable transmission, but the price advantage is obvious, making it the mainstream in small and medium horsepower products. Prior art JP2009133436A provides a hydraulic control device for an automatic transmission, which includes an orifice and an accumulator, and when the hydraulic control device changes from the D range to the N range, the orifice and the accumulator supply the original pressure to the linear solenoid valve for a predetermined time to achieve the release control of the clutch C-1 and prevent the sudden release of the clutch C-1. The orifice and the accumulator are arranged in the oil circuit closer to the linear solenoid valve SLC1 than the branch part branching to the oil circuit. Since the pressure accumulation of the accumulator does not act on the first clutch apply relay valve, the accumulator only needs to be used for the release control of the clutch C-1 through the linear solenoid valve SLC1. The inventor believes that there is a large room for improvement in the prior art. Summary of the invention

[0003] The purpose of the present invention is to provide a hydraulic shift system for a power shift transmission for small and medium horsepower tractors. The hydraulic shift system builds pressure through an oil pump and adjusts the solenoid valve to push the clutch and the shift selector valve core to move; to achieve accurate collection of the flow of the hydraulic control system and accurate control of the solenoid valve pressure to avoid overcharging of the clutch; to reduce the shift response time, avoid frustration, and improve driving comfort. To this end, the present invention provides a hydraulic control system for a small horsepower tractor, including a clutch pressure control system and an execution structure. The clutch pressure control system includes at least two clutch pressure control mechanisms, an accumulator, and the hydraulic oil must pass through the accumulator corresponding to the clutch solenoid valve before flowing into the clutch solenoid valve; the clutch solenoid valve directly drives the execution structure to provide hydraulic oil. Each clutch solenoid valve is provided with a corresponding accumulator. The vane pump assembly is powered by the accumulator after suppressing pressure pulsation, thereby reducing working noise and maintaining uniform working pressure. The accumulator absorbs pressure shock during gear shifting of the hydraulic system and eliminates pulsation. The accumulator has the characteristic of rapid oil discharge, which can reduce the gear shift response time, avoid frustration, and improve driving comfort. The clutch solenoid valve direct drive provides controllable hydraulic pressure of the actuator structure hydraulic ratio, reduces control valve components, and improves control accuracy and response speed.

[0004] Preferably, the clutch pressure control mechanism includes a speed sensor and a clutch, and the output oil circuit of the clutch solenoid valve is provided with a pressure sensor. The input shaft, output shaft and PTO of the hydraulic control system are provided with speed sensors, and the speed sensors are used to collect the speeds of the input shaft, output shaft and PTO, and the pressure sensors are used to accurately collect the hydraulic oil flow and accurately control the pressure of the solenoid valve, so as to ensure the accuracy of the gear position and avoid overcharging the clutch.

[0005] Preferably, the hydraulic control system includes a vane pump assembly and an oil tank. The vane pump assembly is provided with a relief valve. The oil inlet end of the relief valve is connected to the output end of the vane pump, and the overflow end of the relief valve is connected to the oil tank. The output oil pressure of the vane pump assembly is fed back to the relief valve. The relief valve maintains the output pressure and flow of the pump within the upper limit range, limiting the maximum pressure and flow of the hydraulic system; the hydraulic oil overflowed by the relief valve is directly returned to the oil tank, accelerating the circulation of the hydraulic oil, reducing the necessary redundant hydraulic oil for overflow, reducing the total amount of hydraulic oil required by the hydraulic control system, and reducing the consumption of hydraulic oil.

[0006] Preferably, the hydraulic control system includes a pressure regulating mechanism and a cooling mechanism, the hydraulic oil flows into the cooling mechanism through the pressure regulating mechanism, and the pressure regulating mechanism includes a main regulating valve, which controls the flow rate of the hydraulic oil. The hydraulic control system is provided with a pressure regulating structure to control the pressure and flow rate of the hydraulic system and establish the system pressure; the main regulating valve delivers the overflow flow rate to the cooling structure to lubricate and cool the system, accelerate the lubrication and cooling cycle of the hydraulic oil, and improve the lubrication and cooling effect of the cooling structure.

[0007] Preferably, the main regulating valve is provided with a first oil circuit, a second oil circuit and a third oil circuit, and the pressure difference between the first oil circuit and the third oil circuit is used to control the flow of the second oil circuit, and the hydraulic oil flows into the cooling mechanism through the second oil circuit. The pressure difference between the first oil circuit and the third oil circuit is used to control the piston opening in the pressure regulating mechanism, thereby controlling the flow of the second oil circuit and improving the accuracy of the control effect; the use of transmission control components is reduced by using the oil circuit pressure difference control, and the control response speed and the reliability of the control effect are improved.

[0008] As a preferred embodiment, the clutch solenoid valve is provided with an oil inlet connected to the output end of the vane pump assembly connected to the working oil circuit, the pressure sensor detects the working oil circuit, and the working oil circuit is connected to the accumulator and the clutch. After being controlled by the clutch solenoid valve, the hydraulic oil enters the accumulator and the clutch along the working oil circuit to charge the accumulator and supply oil to the clutch. The accumulator ensures the stability of the oil pressure in the working oil circuit, absorbs the pressure shock of the hydraulic system during gear shifting and eliminates pulsation; the accumulator can quickly release oil and unload, reduce the gear shift response time, avoid frustration, and improve driving comfort.

[0009] Preferably, a filter is provided between the vane pump assembly and the oil tank. The filter mainly filters the hydraulic oil entering the vane pump assembly and the subsequent oil circuit to prevent the vane pump from getting stuck due to impurities in the hydraulic oil; ensure the cleanliness of the hydraulic system to prevent the solenoid valve from getting stuck due to impurities in the hydraulic oil and other abnormal responses; and prevent the hydraulic oil from having abnormal oil temperature due to impurities, which reduces the lubrication and cooling effect.

[0010] Preferably, the pressure regulating mechanism includes a regulating solenoid valve, which is connected to the first oil circuit and the third oil circuit. The vane pump provides hydraulic oil to the regulating solenoid valve through the first oil circuit, and after electromagnetic control, it is provided to the main regulating valve through the third oil circuit. A spring chamber is provided in the main regulating valve, and the first oil circuit and the third oil circuit are respectively connected to the two ends of the spring chamber. A valve core is provided in the spring chamber, and the valve core can move according to the pressure difference between the first oil circuit and the third oil circuit to adjust the flow of the second oil circuit. The above-mentioned setting plays a role in controlling the pressure of the main oil circuit and accurately controlling the flow of hydraulic oil to the cooling mechanism; the regulating solenoid valve changes its own change rate through the pressure sensor and speed sensor of the clutch pressure control system, collects clutch speed information and working oil circuit pressure information, obtains the clutch working state, and feedback controls the change rate of the regulating solenoid valve, improves the response rate under low speed state, and ensures stability under high speed state.

[0011] The present invention provides a hydraulic shifting system for a power shifting gearbox for small and medium horsepower tractors. The default initial gear position of the hydraulic shifting system is neutral. The clutch and the shifting valve core are driven to move by building up pressure through an oil pump and adjusting the solenoid valve. The output oil circuits of all clutch solenoid valves are provided with pressure sensors. The input shaft, output shaft and PTO of the hydraulic control system are provided with speed sensors. The speed sensors are used to collect the speeds of the input shaft, output shaft and PTO. The pressure sensors are used to accurately collect the flow of the hydraulic control system and accurately control the pressure of the solenoid valve to avoid overcharging of the clutch. The solenoid valve is equipped with an accumulator to absorb the pressure impact of the hydraulic system during the shifting process, thereby reducing the shifting response time, avoiding the sense of frustration, and improving High driving comfort, and has the following beneficial effects: the hydraulic control system is provided with an overflow structure to control the output pressure and flow of the vane pump to be maintained within the upper limit range, thereby ensuring the maximum pressure of the hydraulic control system; at the same time, the overflowing hydraulic oil is supplied to the cooling mechanism for lubrication and cooling, thereby accelerating the circulation of the hydraulic oil, reducing the necessary redundant hydraulic oil for overflow, reducing the total amount of hydraulic oil required by the hydraulic control system, and reducing the consumption of hydraulic oil; the clutch solenoid valve is used to directly drive the control execution structure and the clutch, thereby reducing the control valve parts, and improving the control accuracy and response speed; the pressure difference control between the first oil circuit and the third oil circuit is used to improve the accuracy of the control effect, reduce the use of transmission control components, and improve the control response speed and the reliability of the control effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0013] Figure 1 It is a structural schematic diagram of the present invention;

[0014] Figure 2 It is a structural schematic diagram of the vane pump assembly of the present invention;

[0015] Figure 3 It is a structural schematic diagram of the pressure regulating structure of the present invention;

[0016] Figure 4 It is a schematic structural diagram of the clutch pressure control mechanism of the present invention.

[0017] Explanation of the reference numerals: 1 oil tank; 2 filter; 3 vane pump; 4 overflow valve; 5 valve body; 6 main regulating valve core; 7 main regulating valve spring; 8 stopper; 9 main regulating valve positioning plate; 10 regulating solenoid valve; 11 first oil circuit; 12 second oil circuit; 13 third oil circuit; 14 clutch solenoid valve; 15 clutch bearing; 16 accumulator piston; 17 accumulator spring; 18 execution structure; 19 clutch pressure control system. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0019] Embodiment 1

[0020] like Figure 1 As shown, the present invention provides a hydraulic control system for a small horsepower tractor, including an oil tank 1, a filter 2, a vane pump assembly, a pressure regulating mechanism, a cooling mechanism, a clutch pressure control system 19 and an execution structure 18. The clutch pressure control system 19 includes a first clutch pressure control mechanism, a second clutch pressure control mechanism, a third clutch pressure control mechanism, a fourth clutch pressure control mechanism and a power take-off clutch pressure control mechanism. Each clutch pressure control mechanism is provided with a clutch solenoid valve 14, and each clutch solenoid valve 14 is provided with a corresponding accumulator. The accumulator includes an accumulator spring 17 and an accumulator piston 16, and the actual maximum pressure is controlled by the vane pump assembly. Before the hydraulic oil flows into the clutch solenoid valve 14, it needs to pass through the accumulator corresponding to the clutch solenoid valve 14. After the hydraulic oil enters the accumulator, it pushes the accumulator piston 16 to compress the accumulator spring 17 to charge the accumulator; the clutch solenoid valve 14 directly drives the execution structure 18 to provide hydraulic oil. A filter 2 is provided between the vane pump assembly and the oil tank 1.

[0021] Through the above arrangement, each clutch solenoid valve 14 is provided with a corresponding accumulator, which provides power to the gearbox pressure system; the accumulator absorbs the pressure shock during the hydraulic system shifting and eliminates pulsation; the accumulator has the characteristic of rapid oil discharge, which can reduce the gearbox shifting response time, avoid frustration, and improve driving comfort; the clutch solenoid valve 14 directly drives and provides hydraulic oil to the execution structure 18, reduces the control valve components, and improves the control accuracy and response speed. The filter 2 mainly filters the hydraulic oil entering the vane pump assembly and the subsequent oil circuit to prevent the vane pump 3 from being stuck due to impurities in the hydraulic oil; ensure the cleanliness of the hydraulic system to avoid abnormal responses such as the solenoid valve being stuck due to impurities in the hydraulic oil; and avoid abnormal oil temperature due to the presence of impurities in the hydraulic oil, which reduces the lubrication and cooling effect.

[0022] like Figure 4As shown, each clutch pressure control mechanism includes a clutch bearing 15 and a corresponding clutch, and the clutch solenoid valve 14 is provided with a pressure sensor. The output oil circuits of all clutch solenoid valves are provided with pressure sensors, and the input shaft, output shaft and PTO of the hydraulic control system are provided with speed sensors. The speed sensors are used to collect the speeds of the input shaft, output shaft and PTO, and the pressure sensors are used to accurately collect the hydraulic oil flow and accurately control the pressure of the solenoid valve, so as to ensure the accuracy of the gear position, avoid overcharging the clutch, collect the clutch speed information and the working oil circuit pressure information, obtain the clutch working state, and feedback control to adjust the change rate of the solenoid valve, improve the response rate under low speed state, and ensure the stability under high speed state.

[0023] Combination Figure 1 and Figure 2 As shown, Figure 2 The middle arrow indicates the flow direction of the hydraulic oil when the hydraulic control system is working. The hydraulic control system includes a vane pump assembly and an oil tank 1. The vane pump assembly is provided with a relief valve 4. One end of the relief valve 4 is connected to the output end of the vane pump assembly, and the other end of the relief valve 4 is connected to the oil tank 1. The relief valve 4 maintains the output pressure and flow of the pump within the upper limit range, limiting the maximum pressure and flow of the hydraulic system; the hydraulic oil overflowed by the relief valve 4 is directly returned to the oil tank 1, which speeds up the circulation of the hydraulic oil, reduces the necessary redundant hydraulic oil for overflow, reduces the total amount of hydraulic oil required by the hydraulic control system, and reduces the consumption of hydraulic oil.

[0024] like Figure 1 As shown, the hydraulic control system includes a pressure regulating mechanism and a cooling mechanism. The hydraulic oil flows into the cooling mechanism through the pressure regulating mechanism. The pressure regulating mechanism includes a main regulating valve, which controls the flow of the hydraulic oil. The hydraulic control system sets a pressure regulating structure to control the pressure and flow of the hydraulic system and establish the system pressure; the main regulating valve delivers the overflow flow to the cooling structure to lubricate and cool the system, accelerate the lubrication and cooling cycle of the hydraulic oil, and improve the lubrication and cooling effect of the cooling structure.

[0025] like Figure 3 As shown, Figure 3The middle arrow indicates the flow direction of the hydraulic oil when the hydraulic control system is working. The main regulating valve is provided with a first oil circuit 11, a second oil circuit 12 and a third oil circuit 13. The pressure difference between the first oil circuit 11 and the third oil circuit 13 is used to control the flow of the second oil circuit 12, and the hydraulic oil flows into the cooling mechanism through the second oil circuit 12. The pressure regulating mechanism includes a regulating solenoid valve 10. The regulating solenoid valve 10 connects the first oil circuit 11 and the third oil circuit 13. The vane pump 3 provides hydraulic oil to the regulating solenoid valve 10 through the first oil circuit 11, and after electromagnetic control, it is provided to the main regulating valve through the third oil circuit 13. A spring chamber is provided in the valve body 5 of the main regulating valve, and a main regulating valve spool 6 and a main regulating valve spring 7 are provided in the spring chamber. One end of the main regulating valve spool 6 abuts against the stopper 8 and the main regulating valve positioning plate 9 in turn. The inlet end of the first oil circuit 11 and the second oil circuit 12 is the vane pump assembly, and the outlet end of the first oil circuit 11 is one end of the regulating solenoid valve and the main regulating valve spring chamber, which provides the regulating solenoid valve and the main regulating valve with hydraulic oil of system pressure, that is, the hydraulic oil whose output pressure of the vane pump assembly is not regulated; the outlet end of the second oil circuit 12 is the main regulating valve spool 6, and the main regulating valve spool 6 controls the opening of the outlet end to adjust the flow of the second oil circuit 12. The inlet end of the third oil circuit 13 is the regulating solenoid valve, and the first oil circuit 11 supplies oil to the regulating solenoid valve, which is pressure-adjusted by the regulating solenoid valve and output by the third oil circuit 13. The outlet end of the third oil circuit 13 is the other end of the main regulating valve spring chamber. The first oil circuit 11 and the third oil circuit 13 are connected to the two ends of the spring chamber respectively. Since the hydraulic oil output by the third oil circuit 13 is the hydraulic oil whose pressure is adjusted by the regulating solenoid valve of the first oil circuit 11. A main regulating valve core 6 is arranged in the spring chamber, and the main regulating valve core 6 can move according to the pressure difference between the first oil circuit 11 and the third oil circuit 13 to adjust the flow of the second oil circuit 12. The first oil circuit 11 is directly supplied with oil by the vane pump 3, and the hydraulic oil pushes the main regulating valve core 6 to compress the main regulating valve spring 7, so that the hydraulic oil in the second oil circuit 12 can go to the cooling mechanism.

[0026] The above arrangement plays a role in controlling the pressure of the main oil circuit and accurately controlling the flow of hydraulic oil to the cooling mechanism. The pressure difference control between the first oil circuit 11 and the third oil circuit 13 is adopted to improve the accuracy of the control effect, reduce the use of transmission control components, and improve the control response speed and the reliability of the control effect.

[0027] like Figure 4 As shown, the clutch solenoid valve 14 is provided with an oil inlet and an oil outlet connected to the output end of the vane pump assembly and connected to the working oil circuit. The pressure sensor detects the working oil circuit, and the working oil circuit is connected to the accumulator and the clutch. After being controlled by the clutch solenoid valve 14, the hydraulic oil enters the accumulator and the clutch along the working oil circuit to charge the accumulator and supply oil to the clutch. The accumulator ensures the stability of the oil pressure in the working oil circuit, absorbs the pressure shock of the hydraulic system during gear shifting and eliminates pulsation; the accumulator can quickly release oil and unload, reduce the gear shift response time, avoid frustration, and improve driving comfort.

[0028] The present invention provides a hydraulic shifting system for a power shifting gearbox for small and medium horsepower tractors. The hydraulic shifting system defaults to the neutral gear as the initial gear position. The clutch and the shifting valve core are driven to move by building up pressure through an oil pump and adjusting the solenoid valve. The output oil circuits of all clutch solenoid valves are provided with pressure sensors. The input shaft, output shaft and PTO of the hydraulic control system are provided with speed sensors. The speed sensors are used to collect the speeds of the input shaft, output shaft and PTO. The pressure sensors are used to accurately collect the flow of the hydraulic control system and accurately control the pressure of the solenoid valve to avoid overcharging of the clutch. The solenoid valve is equipped with an accumulator to absorb the pressure impact of the hydraulic system during the shifting process, thereby reducing the shifting response time, avoiding the sense of frustration, and improving Driving comfort, and has the following beneficial effects: the hydraulic control system is provided with an overflow structure to control the output pressure and flow of the vane pump 3 to be maintained within the upper limit range, thereby ensuring the maximum pressure of the hydraulic control system; at the same time, the overflowing hydraulic oil is supplied to the cooling mechanism for lubrication and cooling, thereby accelerating the circulation of the hydraulic oil, reducing the necessary redundant hydraulic oil for overflow, reducing the total amount of hydraulic oil required by the hydraulic control system, and reducing the consumption of hydraulic oil; the clutch solenoid valve is used to directly drive the control execution structure 18 and the clutch, thereby reducing the control valve parts and improving the control accuracy and response speed; the pressure difference control between the first oil circuit and the third oil circuit is used to improve the accuracy of the control effect, reduce the use of transmission control components, and improve the control response speed and the reliability of the control effect.

[0029] The above embodiments and / or implementation methods are only used to illustrate the preferred embodiments and / or implementation methods for realizing the technology of the present invention, and are not intended to impose any form of limitation on the implementation methods of the technology of the present invention. Any technical personnel in this field may make slight changes or modifications to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as technologies or embodiments that are essentially the same as the present invention.

Claims

1. A hydraulic control system for a small horsepower tractor, comprising a clutch pressure control system (19) and an execution structure (18), characterized in that: The clutch pressure control system (19) comprises at least two clutch pressure control mechanisms, each clutch pressure control mechanism is provided with a clutch solenoid valve (14), each clutch solenoid valve (14) is provided with a corresponding accumulator, and hydraulic oil needs to pass through the accumulator corresponding to the clutch solenoid valve (14) before flowing into the clutch solenoid valve (14); the clutch solenoid valve (14) provides hydraulic oil for direct driving of the execution structure (18); The hydraulic control system comprises a pressure regulating mechanism and a cooling mechanism, the hydraulic oil flows into the cooling mechanism through the pressure regulating mechanism, the pressure regulating mechanism comprises a main regulating valve, and the main regulating valve controls the flow rate of the hydraulic oil; The main regulating valve is provided with a first oil circuit (11), a second oil circuit (12) and a third oil circuit (13), and the flow rate of the second oil circuit (12) is controlled by using the pressure difference between the first oil circuit (11) and the third oil circuit (13), and the hydraulic oil flows into the cooling mechanism through the second oil circuit (12); The accumulator comprises an accumulator spring (17) and an accumulator piston (16). After the hydraulic oil enters the accumulator, it pushes the accumulator piston (16) to compress the accumulator spring (17) to charge the accumulator. A spring chamber is provided in the valve body (5) of the main regulating valve, and a main regulating valve core (6) and a main regulating valve spring (7) are provided in the spring chamber. One end of the main regulating valve core (6) abuts against a stopper (8) and a main regulating valve positioning plate (9) in sequence. The inlet ends of the first oil circuit (11) and the second oil circuit (12) are vane pump assemblies. The outlet end of the first oil circuit (11) is an end of the regulating solenoid valve and the main regulating valve spring chamber, and provides hydraulic oil of system pressure, i.e., hydraulic oil whose output pressure of the vane pump assembly is not regulated, to the regulating solenoid valve and the main regulating valve. The outlet end of the second oil circuit (12) is the main regulating valve core (6), and the main regulating valve core (6) controls the opening of the outlet end to adjust the flow of the second oil circuit (12).

2. A hydraulic control system for a small horsepower tractor according to claim 1, characterized in that: The clutch pressure control mechanism comprises a rotation speed sensor and a clutch, and the output oil circuit of the clutch solenoid valve (14) is provided with a pressure sensor.

3. The hydraulic control system for a small horsepower tractor according to claim 1, characterized in that: The hydraulic control system comprises a vane pump assembly and an oil tank (1), the vane pump assembly being provided with a relief valve (4), the oil inlet end of the relief valve (4) being connected to the output end of the vane pump assembly, and the overflow end of the relief valve (4) being connected to the oil tank (1).

4. A hydraulic control system for a small horsepower tractor according to claim 2, characterized in that: The clutch solenoid valve (14) is provided with an oil inlet connected to the output end of the vane pump assembly and connected to a working oil circuit, the pressure sensor detects the working oil circuit, and the working oil circuit is connected to the accumulator and the clutch.

5. The hydraulic control system for a small horsepower tractor according to claim 3, characterized in that: A filter (2) is provided between the vane pump assembly and the oil tank (1).

6. The hydraulic control system for a small horsepower tractor according to claim 1, characterized in that: The pressure regulating mechanism comprises a regulating solenoid valve (10), wherein the regulating solenoid valve (10) is connected to the first oil circuit (11) and the third oil circuit (13).

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