HST hydraulic control system of tractor

Abstract

A tractor HST hydraulic control system relates to the technical field of hydraulic control systems and comprises a hydraulic pump and a hydraulic motor, the hydraulic pump and the hydraulic motor are connected through a high-pressure oil way and a low-pressure oil way which are connected in parallel, the hydraulic pump is connected with an oil supplementing oil way, and the oil supplementing oil way is connected with a first slide valve and a second slide valve in parallel. An oil inlet of the first sliding valve is connected with a variable piston bottom oil cavity of the hydraulic pump, and an oil inlet of the second sliding valve is connected with a variable piston top oil cavity of the hydraulic pump. The hydraulic control loop solves the problems that in the prior art, a hydraulic control loop always has the defects of being poor in comfort, complex in operation and waste in power, and consequently fuel economy is poor.

Description

Technical Field

[0001] This utility model relates to the field of hydraulic control system technology, specifically to the HST hydraulic control system for tractors. Background Technology

[0002] The HST system is the hydraulic drive system for a tractor. It uses a hydraulic pump to deliver pressurized oil to a hydraulic motor, which in turn drives the wheels. The forward and reverse rotation of the hydraulic pump determines the direction of its pressurized oil output, which in turn determines the direction of rotation of the hydraulic motor's output shaft, thus enabling the tractor to move forward and backward.

[0003] As the application areas of tractors expand, users have higher requirements for the speed control of the whole machine. They not only need to achieve continuous speed control, but also need to make the operation more convenient and comfortable.

[0004] A prior art patent with publication number CN222277062U discloses a solution including a replenishing pump, a travel pump, and a travel motor. The travel pump and the travel motor are connected in a loop via pipelines. The outlet of the replenishing pump has a replenishing branch and a control branch. The replenishing branch is connected to a first check valve and a second check valve via branch lines. The outlet of the first check valve is connected to one end of the travel motor, and the outlet of the second check valve is connected to the other end of the travel motor. The control branch is connected to an electromagnetic directional valve, which is connected to a plunger mechanism. The output end of the plunger mechanism is connected to the control switch of the travel pump. Using this invention, the replenishing pump supplies oil to the control branch, and the electromagnetic directional valve controls the oil output direction, thereby controlling the continuous movement of the output end of the plunger mechanism. The control switch of the travel pump enables forward and backward state control and continuous speed control of the HST system, improving operational convenience.

[0005] As existing devices are used, the shortcomings of this technology have gradually become apparent, mainly in the following aspects:

[0006] Existing hydraulic control circuits have always suffered from drawbacks such as poor comfort, complex operation, and wasted power, resulting in poor fuel economy.

[0007] In conclusion, the existing technology obviously has inconveniences and defects in practical use, so it is necessary to improve it. Utility Model Content

[0008] In view of the shortcomings of the existing technology, this utility model solves the problems of poor comfort, complicated operation, and power waste in the hydraulic control circuit of the traditional technology, which leads to poor fuel economy.

[0009] To solve the above problems, this utility model provides the following technical solution:

[0010] The tractor HST hydraulic control system includes a hydraulic pump and a hydraulic motor. The hydraulic pump and the hydraulic motor are connected in parallel via a high-pressure oil circuit and a low-pressure oil circuit. The hydraulic pump is connected to a replenishing oil circuit, which is connected in parallel with a first slide valve and a second slide valve. The oil inlet of the first slide valve is connected to the bottom oil chamber of the variable piston of the hydraulic pump, and the oil inlet of the second slide valve is connected to the top oil chamber of the variable piston of the hydraulic pump.

[0011] As an optimized solution, a throttle valve is connected to the oil replenishment line.

[0012] As an optimized solution, a replenishment overflow valve is connected in parallel on the replenishment oil line.

[0013] As an optimized solution, a system relief valve is connected in parallel to both the high-pressure oil circuit and the low-pressure oil circuit, and the outlet ends of the two system relief valves are connected to the replenishing relief valve.

[0014] As an optimized solution, the hydraulic motor is provided with hydraulic motor detection ports on both sides of the high-pressure oil circuit and the low-pressure oil circuit.

[0015] As an optimized solution, hydraulic pump detection ports are provided at both ends of the variable piston of the hydraulic pump.

[0016] As an optimized solution, the first and second slide valves include two-position three-way valves.

[0017] As an optimized solution, the outlet end of the oil replenishment overflow valve is connected to the oil tank.

[0018] As an optimized solution, the oil outlets of the first and second slide valves are connected to the oil tank.

[0019] Compared with the prior art, the beneficial effects of this utility model are:

[0020] The hydraulic pump is powered directly by the engine. The high-pressure oil it produces is converted from hydraulic energy to mechanical energy by the hydraulic motor. The high-pressure oil is also converted into low-pressure oil and returns to the hydraulic pump inlet.

[0021] In this circuit, both the high-pressure oil circuit and the low-pressure oil circuit are equipped with a system relief valve to ensure system pressure.

[0022] This solution also includes a replenishment oil circuit, with the replenishment port G connected to an external oil circuit, and a replenishment overflow valve is installed in the replenishment oil circuit.

[0023] A branch line of oil is introduced from the replenishment oil port G and sent to the first and second slide valves. A throttle valve is installed in this oil line to ensure that the oil pressure reaching the variable piston of the hydraulic pump is stable and without impact, so that the output flow of the hydraulic pump does not fluctuate drastically when the pump is variable.

[0024] The first and second spool valves are two-position three-way valves that can be mechanically controlled or controlled by an electromagnet. The oil inlet of the first spool valve is connected to the bottom oil chamber of the hydraulic pump variable piston, and the oil outlet is connected to the oil tank. The oil inlet of the second spool valve is connected to the top oil chamber of the hydraulic pump variable piston, and the oil outlet is connected to the oil tank.

[0025] A detection port is provided on each side of the hydraulic motor to monitor the system pressure and the stability of motor operation. Detection ports are provided at both ends of the variable piston of the hydraulic pump to monitor the pressure at both ends of the variable piston.

[0026] Hydraulic circuits are simple, reliable, easier to implement, and inexpensive. They are compatible with both electronic and mechanical control methods, making tractor operation simpler and more comfortable. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0028] Figure 1 This is a schematic diagram of the structure of this utility model.

[0029] In the diagram: 1-Hydraulic pump; 2-Hydraulic motor; 3-High-pressure oil circuit; 4-Low-pressure oil circuit; 5-System relief valve; 6-First slide valve; 7-Second slide valve; 8-Maintenance oil circuit; 9-Maintenance relief valve; 10-Throttle valve; 11-Oil tank; 12-Hydraulic motor test port; 13-Hydraulic pump test port. Detailed Implementation

[0030] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0031] like Figure 1 As shown, the tractor HST hydraulic control system includes a hydraulic pump 1 and a hydraulic motor 2. The hydraulic pump 1 and the hydraulic motor 2 are connected in parallel by a high-pressure oil circuit 3 and a low-pressure oil circuit 4. The hydraulic pump 1 is connected to a replenishing oil circuit 8. The replenishing oil circuit 8 is connected in parallel with a first slide valve 6 and a second slide valve 7. The oil inlet of the first slide valve 6 is connected to the bottom oil chamber of the variable piston of the hydraulic pump 1, and the oil inlet of the second slide valve 7 is connected to the top oil chamber of the variable piston of the hydraulic pump 1.

[0032] A throttle valve 10 is connected to the oil replenishment line 8.

[0033] A replenishing overflow valve 9 is connected in parallel to the replenishing oil line 8.

[0034] System relief valves 5 are connected in parallel on the high-pressure oil circuit 3 and the low-pressure oil circuit 4 respectively, and the outlet ends of the two system relief valves 5 are connected to the replenishing relief valve 9.

[0035] The hydraulic motor 2 is equipped with hydraulic motor detection ports 12 on both sides of the high-pressure oil circuit 3 and the low-pressure oil circuit 4.

[0036] Hydraulic pump detection ports 13 are provided at both ends of the variable piston of hydraulic pump 1.

[0037] The first slide valve 6 and the second slide valve 7 include two-position three-way valves.

[0038] The outlet end of the oil replenishment overflow valve 9 is connected to the oil tank 11.

[0039] The oil outlets of the first slide valve 6 and the second slide valve 7 are connected to the oil tank 11.

[0040] The working principle of this device is as follows:

[0041] Hydraulic pump 1 is powered directly by the engine. The high-pressure oil it generates is converted from hydraulic energy to mechanical energy by hydraulic motor 2. The high-pressure oil is also converted into low-pressure oil and returns to the oil inlet of hydraulic pump 1.

[0042] In this circuit, both the high-pressure oil circuit 3 and the low-pressure oil circuit 4 are equipped with a system relief valve 5 to ensure system pressure.

[0043] This scheme also includes a replenishment oil circuit 8, with the replenishment port G connected to an external oil circuit, and a replenishment overflow valve 9 is installed in the replenishment oil circuit 8.

[0044] A branch oil path is introduced from the replenishment oil port G into the replenishment oil path 8, which leads to the first slide valve 6 and the second slide valve 7. A throttle valve 10 is installed in this oil path to ensure that the oil pressure reaching the variable piston of the hydraulic pump 1 is stable and without impact, so that the output flow of the hydraulic pump 1 does not fluctuate drastically when it is in variable position.

[0045] The first slide valve 6 and the second slide valve 7 are two-position three-way valves that can be mechanically controlled or controlled by an electromagnet. The oil inlet of the first slide valve 6 is connected to the bottom oil chamber of the variable piston of the hydraulic pump 1, and the oil outlet is connected to the oil tank 11. The oil inlet of the second slide valve 7 is connected to the top oil chamber of the variable piston of the hydraulic pump 1, and the oil outlet is connected to the oil tank 11.

[0046] A detection port is provided on each side of the hydraulic motor 2 to monitor the system pressure and the stability of motor operation. Detection ports are provided at both ends of the variable piston of the hydraulic pump 1 to monitor the pressure at both ends of the variable piston.

[0047] Specifically, after the tractor starts, the engine drives the hydraulic pump 1 to rotate. At the same time, the oil in the replenishment circuit is throttled by the throttle valve 10 and reaches the oil ports of the first slide valve 6 and the second slide valve 7. When the first slide valve 6 and the second slide valve 7 are in the right position, the variable piston of the hydraulic pump 1 does not move, the hydraulic pump 1 has no variable displacement, and the flow rate is stable. When deceleration is required, the first slide valve 6 is pushed to the left position by electronic or mechanical control. The replenishment oil enters the bottom oil chamber of the variable piston of the hydraulic pump 1, pushing the piston upward. The oil in the top oil chamber of the piston flows out to the oil tank 11, completing the variable displacement. The displacement of the hydraulic pump 1 decreases, the system flow rate decreases accordingly, the motor speed decreases, and the tractor decelerates. At this time, the first slide valve 6 is pushed to the center of the left and right positions by electronic or mechanical control. There is no more oil flow at both ends of the variable piston, the displacement of the hydraulic pump 1 no longer changes, and the flow rate is stable. When acceleration is needed, the second slide valve 7 is pushed to the left position via electronic or mechanical control. Oil enters the top oil chamber of the variable piston in hydraulic pump 1, pushing the piston downwards. Oil from the top oil chamber flows out to the oil tank 11, completing the variable displacement. The displacement of hydraulic pump 1 increases, the system flow rate increases accordingly, the motor speed increases, and the tractor accelerates. At this point, adjusting the second slide valve 7 to the center of the left / right position via electronic or mechanical control stops oil flow at both ends of the variable piston, the displacement of hydraulic pump 1 no longer changes, and the flow rate output remains stable.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model, and they should all be covered within the scope of the claims and specification of this utility model.

Claims

1. A tractor HST hydraulic control system, characterized in that: The system includes a hydraulic pump (1) and a hydraulic motor (2). The hydraulic pump (1) and the hydraulic motor (2) are connected in parallel via a high-pressure oil circuit (3) and a low-pressure oil circuit (4). The hydraulic pump (1) is connected to a replenishing oil circuit (8). The replenishing oil circuit (8) is connected in parallel with a first slide valve (6) and a second slide valve (7). The oil inlet of the first slide valve (6) is connected to the bottom oil chamber of the variable piston of the hydraulic pump (1), and the oil inlet of the second slide valve (7) is connected to the top oil chamber of the variable piston of the hydraulic pump (1).

2. The tractor HST hydraulic control system according to claim 1, characterized in that: A throttle valve (10) is connected to the oil replenishment circuit (8).

3. The tractor HST hydraulic control system according to claim 1, characterized in that: A replenishing overflow valve (9) is connected in parallel to the replenishing oil circuit (8).

4. The tractor HST hydraulic control system according to claim 3, characterized in that: The high-pressure oil circuit (3) and the low-pressure oil circuit (4) are respectively connected in parallel with system overflow valves (5), and the outlet ends of the two system overflow valves (5) are connected to the oil replenishment overflow valve (9).

5. The tractor HST hydraulic control system according to claim 1, characterized in that: The hydraulic motor (2) is provided with hydraulic motor detection ports (12) on both sides of the high-pressure oil circuit (3) and the low-pressure oil circuit (4).

6. The tractor HST hydraulic control system according to claim 1, characterized in that: The hydraulic pump (1) has hydraulic pump detection ports (13) at both ends of the variable piston.

7. The tractor HST hydraulic control system according to claim 1, characterized in that: The first slide valve (6) and the second slide valve (7) include two-position three-way valves.

8. The tractor HST hydraulic control system according to claim 3, characterized in that: The outlet end of the oil replenishment overflow valve (9) is connected to the oil tank (11).

9. The tractor HST hydraulic control system according to claim 1, characterized in that: The oil outlets of the first slide valve (6) and the second slide valve (7) are connected to the oil tank (11).

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