A four-speed power reversing valve for a loader

Abstract

The present invention discloses a four-speed power reversing valve for a loader, which includes an upper valve body, a lower valve body, a flow dividing valve, a reversing valve, and a shifting valve arranged in the upper valve body, and a balance valve I, a balance valve II, a buffer valve I, and a buffer valve II arranged in the lower valve body; an oil port I of the buffer valve I is connected in parallel to the forward gear working oil circuit, and an oil port II of the buffer valve I is connected to the back pressure oil port of the balance valve I through a buffer oil circuit I; an oil port I of the buffer valve II is connected in parallel to the reverse gear working oil circuit, and an oil port II of the buffer valve II is connected to the back pressure oil port of the balance valve II through a buffer oil circuit II. When the valve group of the present invention switches gears, the balance valve and the buffer valve are used to adjust the oil pressure and flow rate of the gear oil circuit, so that the power device of the loader can achieve the function of smooth gear shifting without impact and shock. The loader operates smoothly without impact during starting, moving forward, and stopping, improving the driving comfort.

Description

Technical Field

[0001] The present invention relates to the field of fluid control devices for valves, and particularly to a four-speed power reversing valve for a loader. Background Art

[0002] The power reversing valve is an important device for a loader to perform power reversing and gear shifting. It is mainly used to control the connection and disconnection of the gear oil circuits in the hydraulic power system, and change the flow direction of the liquid flow to meet the requirements of the loader for changing the traveling direction and gear shifting.

[0003] In actual use, especially during the gear shifting process, if the system pressure rises too fast or the flow rate is too large, it is easy to cause the flow velocity noise to intensify. Vibration and hydraulic shock will occur during reversing and gear shifting, the bucket will vibrate and shake, affecting the operation accuracy, shortening the service life of components, and even causing failures in severe cases. Moreover, it is too large in size, inconvenient for installation and maintenance, has limited gears, and cannot perform fine operations. Summary of the Invention

[0004] To overcome the defects of the prior art, the purpose of the present invention is to provide a four-speed power reversing valve for a loader, which controls and adjusts the gears, oil pressure, and flow velocity, so that the power device of the loader can achieve the function of smooth gear shifting without impact and shock.

[0005] For this purpose, the present invention provides a four-speed power reversing valve for a loader, including an upper valve body, a lower valve body, a flow dividing valve, a reversing valve, a gear shifting valve arranged in the upper valve body, a balance valve one and a balance valve two arranged in the lower valve body; further including:

[0006] A main oil supply circuit for paralleling the oil inlet of the flow dividing valve and the oil inlet of the gear shifting valve;

[0007] An oil return circuit for paralleling the oil return port of the flow dividing valve, the oil return port of the reversing valve, the oil return port of the gear shifting valve, the oil return port of the balance valve one, and the oil return port of the balance valve two;

[0008] A reverse gear oil supply circuit for connecting the oil outlet of the flow dividing valve and the first oil inlet of the reversing valve;

[0009] A forward gear oil supply circuit for connecting the oil outlet of the flow dividing valve and the second oil inlet of the reversing valve;

[0010] A reverse gear working oil circuit for paralleling the first oil outlet of the reversing valve, the oil inlet of the balance valve one, and the oil passage port KR of the reverse gear clutch;

[0011] A forward gear working oil circuit for paralleling the second oil outlet of the reversing valve, the oil inlet of the balance valve two, and the oil passage port KF of the forward gear clutch;

[0012] A first gear working oil circuit for connecting the first oil outlet of the gear shifting valve and the oil passage port K1 of the first gear clutch;

[0013] The second - gear working oil circuit for connecting the second oil outlet of the shift valve and the oil inlet of the second - gear clutch K2;

[0014] The third - gear working oil circuit for connecting the third oil outlet of the shift valve and the oil inlet of the third - gear clutch K3;

[0015] The fourth - gear working oil circuit for connecting the fourth oil outlet of the shift valve and the oil inlet of the fourth - gear clutch K4.

[0016] Furthermore, a first buffer valve and a second buffer valve are also provided on the lower valve body. The first oil port of the first buffer valve is connected in parallel to the forward - gear working oil circuit, and the second oil port of the first buffer valve is connected to the back - pressure oil port of the first balance valve through a first buffer oil circuit; the first oil port of the second buffer valve is connected in parallel to the reverse - gear working oil circuit, and the second oil port of the second buffer valve is connected to the back - pressure oil port of the second balance valve through a second buffer oil circuit.

[0017] Furthermore, the first buffer valve and the second buffer valve have the same structure, and both include a first valve body and a stop pin, an inner cavity, a buffer spring, and a buffer piston installed in the first valve body; the second oil port and the first oil port of the first buffer valve are arranged on the first valve body and are located on both sides of the buffer piston, and one end of the first oil port of the first buffer valve is connected to the oil inlet of the forward - gear clutch KF or the oil inlet of the reverse - gear clutch KR.

[0018] Furthermore, the second balance valve and the first balance valve have the same structure, and both include a second valve body, a fourth spring, and a piston. The left end of the piston forms a left cavity with the second valve body, the right end of the piston forms a right cavity with the second valve body, and the fourth spring is arranged in the right cavity; meanwhile, an oil inlet, an oil return port, and a back - pressure oil port are provided on the second valve body, and the back - pressure oil port is connected to the right cavity.

[0019] Furthermore, an oil passage two communicating with the right cavity is provided at the central position of the piston. The piston is also provided with a first throttle hole, an oil passage one, and a second throttle hole. The oil inlet of the first balance valve is connected to the left cavity through the first throttle hole, the oil inlet of the first balance valve is connected to the oil passage two through the oil passage one, the oil inlet of the first balance valve is connected to the right cavity through the second throttle hole, and a check valve is provided in the oil passage two to make the oil flow only from the back - pressure oil port of the first balance valve to the side of the oil inlet; unloading valves are formed at the positions corresponding to the oil inlet and the oil return port of the first balance valve on the piston.

[0020] Furthermore, the reversing valve is a three - position five - way manual reversing valve, including a manually pushed - pulled reversing valve rod, a first steel ball, a second spring, and three first positioning grooves.

[0021] Further, when the manual push-pull reversing valve rod is in the centered position, the first oil inlet and the second oil inlet of the reversing valve are closed, and the first oil outlet, the second oil outlet, and the oil return port are interconnected;

[0022] When the manual push-pull reversing valve rod is pushed inward, the second oil inlet and the second oil outlet of the reversing valve are connected, the first oil outlet and the oil return port are connected, the first oil inlet is closed, and the oil in the forward gear supply oil circuit passes through port [port number not provided in the original] and enters the forward gear working oil circuit;

[0023] When the manual push-pull reversing valve rod is pulled outward, the first oil inlet and the first oil outlet of the reversing valve are connected, the second oil outlet and the oil return port are connected, the second oil inlet is closed, the oil of the forward gear clutch passes through the second oil outlet and the oil return port of the reversing valve to the oil return circuit for unloading, and at the same time, the oil in the reverse gear supply oil circuit passes through the first oil inlet and the first oil outlet and enters the reverse gear working oil circuit.

[0024] Further, the shift valve is a four-position six-way manual shift valve. When the shift valve is in the first gear, the oil inlet of the shift valve is connected to port one, and the other ports are interconnected; when the shift valve is in the second gear, the oil inlet of the shift valve is connected to the second oil outlet, and the other ports are interconnected; when the shift valve is in the third gear, the oil inlet of the shift valve is connected to port three, and the other ports are interconnected; when the shift valve is in the fourth gear, the oil inlet of the shift valve is connected to port four, and the other ports are interconnected.

[0025] Further, the shift valve includes a manual push-pull shift valve rod, a second steel ball, a third spring, four second positioning grooves, and also includes an oil inlet hole, an oil passage, and an oil outlet hole.

[0026] Further, the flow dividing valve includes a third valve body, a valve cover, a spool valve, and a first spring. At the same time, the flow dividing valve has an oil outlet, an oil outlet, and an oil inlet, and the oil outlets and the oil outlet of the flow dividing valve are connected to the oil inlet.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. When the valve group of the present invention switches gears, the balance valve and the buffer valve are used to adjust the oil pressure and flow rate of the gear oil circuit, so that the power device of the loader can achieve the function of smooth gear shifting without impact and shock. The loader operates smoothly without impact during starting, moving forward, and stopping, improving driving comfort.

[0029] 2. The valve group of the present invention is formed by superimposing the upper valve body and the lower valve body into an integral whole. The upper valve body integrates a reversing valve, a speed change valve, and a flow dividing valve, and the lower valve body integrates a set of balance valves and buffer valves for controlling the forward gear and the reverse gear respectively. The space is utilized fully, and it has a small volume, light weight, and is easy to install;

[0030] 3. In the valve group of the present invention, for the bottom oil grooves of the upper valve body and the lower valve body, the low-pressure oil return circuit is distributed on the periphery, and the remaining high-pressure oil circuits are distributed on the inner periphery, greatly reducing the risk of oil leakage at the external joint surface of the valve group.

[0031] 4. In the valve group of the present invention, through the optimization of the structures of the reversing valve and the shifting valve, 9 gear shifts including 4 forward gears, 4 reverse gears and neutral gear are realized, improving the refined operation of the power transmission of the loader and being more adaptable to the needs of different working environments.

[0032] 5. The valve group of the present invention can improve the operation performance, reduce the labor intensity of the driver and improve the operation efficiency.

[0033] In addition to the purposes, features and advantages described above, the present invention has other purposes, features and advantages. The present invention will be further described in detail below with reference to the drawings. Description of the Drawings

[0034] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0035] Figure 1a is the external structure diagram of the four-speed power reversing valve of the present invention;

[0036] Figure 1b is the cross-sectional view of the upper valve body of the four-speed power reversing valve of the present invention;

[0037] Figure 1c is the cross-sectional view of the lower valve body of the four-speed power reversing valve of the present invention;

[0038] Figure 2 is the schematic diagram of the four-speed power reversing valve of the present invention;

[0039] Figure 3 is the cross-sectional view of the flow dividing valve in the four-speed power reversing valve of the present invention;

[0040] Figure 4 is the cross-sectional view of the reversing valve in the four-speed power reversing valve of the present invention;

[0041] Figure 5 is the cross-sectional view of the shifting valve in the four-speed power reversing valve of the present invention;

[0042] Figure 6 is the cross-sectional view of the balance valve in the four-speed power reversing valve of the present invention;

[0043] Figure 7 is the cross-sectional view of the buffer valve in the four-speed power reversing valve of the present invention;

[0044] Description of the Reference Numerals

[0045] 1. Upper valve body; 2. Lower valve body; 3. Flow dividing valve; 4. Direction changing valve; 5. Shift valve; 6. Buffer valve I; 7. Balance valve I; 8. Buffer valve II; 9. Balance valve II; 10. Main oil supply circuit; 11. Oil return circuit; 12. Reverse gear oil supply circuit; 13. Forward gear oil supply circuit; 14. Reverse gear working oil circuit; 15. Forward gear working oil circuit; 16. Buffer oil circuit I; 17. Buffer oil circuit II; 18. First gear working oil circuit; 19. Second gear working oil circuit; 20. Third gear working oil circuit; 21. Fourth gear working oil circuit; P. Total oil inlet; T. Oil drain port; KF. Forward gear clutch oil passage port; KR. Reverse gear clutch oil passage port; K1. First gear clutch oil passage port; K2. Second gear clutch oil passage port; K3. Third gear clutch oil passage port; K4. Fourth gear clutch oil passage port;

[0046] 31. Valve cover; 32. Spool valve; 33. Spring I; 41. Direction changing valve rod; 42. Spring II; 43. Steel ball I; 44. Positioning groove I; 51. Shift valve rod; 52. Oil inlet hole; 53. Oil passage; 54. Oil outlet hole; 55. Positioning groove II; 56. Spring III; 57. Steel ball II; 61. Left cavity; 62. Throttle hole I; 63. Oil passage I; 64. Check valve; 65. Oil passage II; 66. Throttle hole II; 67. Spring IV; 68. Piston; 69. Right cavity; 610. Unloading valve; 71. Stop pin; 72. Inner cavity; 73. Buffer spring; 74. Buffer piston. Detailed implementation mode

[0047] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0048] As shown in FIGS. 1 to Figure 2 As shown, the four-speed power direction changing valve for a loader according to the present invention includes an upper valve body 1, a lower valve body 2, a flow dividing valve 3, a direction changing valve 4, a shift valve 5 arranged in the upper valve body 1, a buffer valve I 6, a balance valve I 7, a buffer valve II 8, and a balance valve II 9 arranged in the lower valve body 2.

[0049] The four-speed power reversing valve further includes: a main oil supply circuit 10 for paralleling the oil inlet ③ of the flow dividing valve 3 and the oil inlet ② of the shifting valve 5; an oil return circuit 11 for paralleling the oil return port ① of the flow dividing valve 3, the oil return port ① of the reversing valve 4, the oil return port ① of the shifting valve 5, the oil return port ② of the first balance valve 7, and the oil return port ② of the second balance valve 9; a reverse gear oil supply circuit 12 for connecting the oil outlet ② of the flow dividing valve 3 and the first oil inlet ③ of the reversing valve 4; a forward gear oil supply circuit 13 for connecting the oil outlet ④ of the flow dividing valve 3 and the second oil inlet ④ of the reversing valve 4; a reverse gear working oil circuit 14 for paralleling the first oil outlet ② of the reversing valve 4, the first oil inlet ① of the first balance valve 7, the oil port ① of the second buffer valve 8, and the oil passage port KR of the reverse gear clutch; a forward gear working oil circuit 15 for paralleling the second oil outlet ⑤ of the reversing valve 4, the first oil inlet ① of the second balance valve 9, the oil port ① of the first buffer valve 6, and the oil passage port KF of the forward gear clutch.

[0050] Meanwhile, the four-speed power reversing valve further includes: a first buffer oil circuit 16 for connecting the back pressure oil port ③ of the first balance valve 7 and the oil port ② of the first buffer valve 6; a second buffer oil circuit 17 for connecting the back pressure oil port ③ of the second balance valve 9 and the oil port ② of the second buffer valve 8; a first gear working oil circuit 18 for connecting the first oil outlet ③ of the shifting valve 5 and the oil passage port K1 of the first gear clutch; a second gear working oil circuit 19 for connecting the second oil outlet ④ of the shifting valve 5 and the oil passage port K2 of the second gear clutch; a third gear working oil circuit 20 for connecting the third oil outlet ⑤ of the shifting valve 5 and the oil passage port K3 of the third gear clutch; a fourth gear working oil circuit 21 for connecting the fourth oil outlet ⑥ of the shifting valve 5 and the oil passage port K4 of the fourth gear clutch.

[0051] In addition, the four-speed power reversing valve further includes: a total oil inlet P for connecting to a hydraulic pump, an oil drain port T for connecting to the oil return circuit, an oil passage port KF for connecting to the forward gear clutch, an oil passage port KR for connecting to the reverse gear clutch, an oil passage port K1 for connecting to the first gear clutch, an oil passage port K2 for connecting to the second gear clutch, an oil passage port K3 for connecting to the third gear clutch, and an oil passage port K4 for connecting to the fourth gear clutch.

[0052] Specifically, as Figure 3 shown, the flow dividing valve 3 is of a spool type structure, including a valve body two, a valve cover 31, a spool 32, and a first spring 33. The flow dividing valve 3 has four oil ports. The oil outlet ② and the oil outlet ④ of the flow dividing valve 3 are communicated with the oil inlet ③, and its function is to divide the main oil circuit into two paths, one path being the forward gear oil supply circuit 13 and the other path being the reverse gear oil supply circuit 12. The spool 32 controls the opening and closing of the oil return port ① of the flow dividing valve 3 according to the oil pressure of the first spring 33 and the oil outlet ② of the flow dividing valve 3 to achieve pressure relief and oil return.

[0053] As Figure 4As shown, the reversing valve 4 is a three-position five-way manual reversing valve, and its function is: by manually pushing and pulling the reversing valve rod 41 and the positioning mechanism composed of the first steel ball 43, the second spring 42, and the three first positioning grooves 44, to control the loader to be in three gears: forward gear, neutral gear, and reverse gear.

[0054] When the valve rod is in the middle position, the first oil inlet ③ and the second oil inlet ④ are closed, the first oil outlet ②, the second oil outlet ⑤, and the oil return port ① are interconnected, there is no oil flowing out from the forward clutch oil port KF and the reverse clutch oil port KR, the clutch is in the neutral position, and the loader stops moving.

[0055] When the valve rod is pushed inward, the second oil inlet ④ and the second oil outlet ⑤ are interconnected, the first oil outlet ② and the oil return port ① are interconnected, the first oil inlet ③ is closed, and the oil in the forward gear oil supply circuit 13 enters the forward gear working circuit 15 through ports ④ and ⑤, and then enters the forward clutch through port KF to be filled with oil, driving the loader to move forward.

[0056] When the valve rod is pulled outward, ③ and ② are interconnected, ⑤ and ① are interconnected, ④ is closed, the oil in the forward clutch flows through ports ⑤ and ① to the oil return circuit 11 for unloading, and at the same time, the oil in the reverse gear oil supply circuit 12 enters the reverse gear working circuit 14 through ports ③ and ②, and then enters the reverse clutch through port KR to be filled with oil, driving the loader to move backward.

[0057] As Figure 5 shown, the shift valve 5 is a four-position six-way manual shift valve, and its function is: by manually pushing and pulling the shift valve rod 51 and the positioning mechanism composed of the second steel ball 57, the third spring 56, and the four second positioning grooves 55, to control the loader to be in four shift gears: first gear, second gear, third gear, and fourth gear.

[0058] When the valve rod is at the outermost end, the oil inlet ② and the first oil port ③ are interconnected, the oil return port ①, the second oil outlet ④, the third oil outlet ⑤, and the fourth oil outlet ⑥ are interconnected. The main oil circuit oil enters from the oil inlet ②, passes through the valve rod groove and the valve cavity to enter the oil inlet hole 52, and then flows out from the first oil port ③ through the oil passage 53 and the oil outlet hole 54 to the first gear working circuit 18, and then enters the first gear clutch through port K1 to be filled with oil, driving the loader to move forward or backward at the first gear speed.

[0059] When the valve rod is pushed inward by one grid, ② and ④ are interconnected, ①, ③, ⑤, and ⑥ are interconnected. The oil in the first gear clutch flows through ports ③ and ① to the oil return circuit 11 for unloading, and at the same time, the main oil circuit oil passes through ② and ④ to the second gear working circuit 19, and then enters the second gear clutch through port K2 to be filled with oil, driving the loader to move forward or backward at the second gear speed.

[0060] When the valve stem is pushed inward by one more grid, ports ② and ⑤ are connected, and ports ①, ③, ④, and ⑥ are interconnected. The oil of the second - gear clutch passes through ports ④ and ① to the return oil circuit 11 for unloading. At the same time, the oil of the main oil circuit passes through ports ② and ⑤ to the third - gear working oil circuit 20, and then through port K3 to fill the third - gear clutch, driving the loader to move forward or backward at the third - gear speed.

[0061] When the valve stem is pushed inward by one more grid, ports ② and ⑥ are connected, and ports ①, ③, ④, and ⑤ are interconnected. The oil of the third - gear clutch passes through ports ⑤ and ① to the return oil circuit 11 for unloading. At the same time, the oil of the main oil circuit passes through ports ② and ⑥ to the third - gear working oil circuit 20, and then through port K4 to fill the fourth - gear clutch, driving the loader to move forward or backward at the fourth - gear speed.

[0062] As Figure 6 shown, the balance valve two 9 and the balance valve one 7 have the same structure, both including a valve body two, a spring four 67, and a piston 68. The left end of the piston 68 and the valve body two form a left chamber 61, the right end of the piston 68 and the valve body two form a right chamber 69, and the spring four 67 is arranged in the right chamber 69. At the same time, the valve body two is provided with an oil inlet ①, an oil return port ②, and a back - pressure oil port ③, and the back - pressure oil port ③ is communicated with the right chamber 69.

[0063] An oil passage two 65 communicated with the right chamber 69 is arranged at the central position of the piston 68. The piston 68 is also provided with a throttle hole one 62, an oil passage one 63, and a throttle hole two 66. The oil inlet ① is communicated with the left chamber 61 through the throttle hole one 62, the oil inlet ① is communicated with the oil passage two 65 through the oil passage one 63, the oil inlet ① is communicated with the right chamber 69 through the throttle hole two 66, and a check valve 64 is arranged in the oil passage two 65, enabling the oil to flow only from the back - pressure oil port ③ to the side of the oil inlet ①; unloading valves 610 are formed at the positions of the piston 68 corresponding to the oil inlet ① and the oil return port ②.

[0064] As Figure 7 shown, the buffer valve one 6 and the buffer valve two 8 have the same structure, both including a valve body one and a stop pin 71, an inner cavity 72, a buffer spring 73, and a buffer piston 74 installed in the valve body one; the valve body one has an oil port ② and an oil port ①, the oil port ② and the oil port ① are located on both sides of the buffer piston 74, and one end of the oil port ① is connected to the oil - passing port KF of the forward - gear clutch or the oil - passing port KR of the reverse - gear clutch.

[0065] The working principle and working process of the four - gear power - reversing valve for the loader of the present invention will be briefly described below with reference to the accompanying drawings.

[0066] As Figure 2 、 6 、7 shown, when the reversing valve 4 is in the forward - gear position, the oil of the forward - gear working oil circuit 15 is divided into three paths. One path enters port KF to the forward - gear clutch; another path enters the oil port ① of the buffer valve one 6 to fill the inner cavity 72 with oil; the third path enters the oil port ① of the balance valve two 9.

[0067] Under the action of throttle orifice 62 and throttle orifice 66, the flow rate of the oil entering the oil port ① of balance valve 9 is restricted, and the pressure of the forward buffer oil circuit 17 is lower than that of the forward gear working oil circuit 15. The pressure difference at both ends of piston 68 keeps check valve 64 closed, creating a closed condition for buffer valve 8 to absorb oil pressure in the next step.

[0068] The oil entering the oil port ① of balance valve 9 is divided into two paths. One path passes through throttle orifice 62 and enters the left chamber 61. The oil pressure acts on the left end face of piston 68, compressing spring 67. Piston 68 moves, and unloading valve 610 is opened. Ports ① and ② are connected. Part of the oil in the forward gear working oil circuit 15 is unloaded through ports ① and ② of balance valve 9 to the return oil circuit 11, maintaining a lower pressure in the forward gear working oil circuit 15 for the forward gear clutch to be filled with oil. Its pressure is determined by the force value of spring 67.

[0069] The other path enters the right chamber 69 through throttle orifice 66 of balance valve 9, exits from port ③, enters port ② of buffer valve 8 through buffer oil circuit 17. Buffer spring 73 is compressed, buffer piston 74 moves, and buffer valve 8 absorbs part of the oil pressure energy. When buffer piston 74 moves to the end, the oil pressure in buffer oil circuit 17 starts to rise. The oil pressure in the right chamber 69 of balance valve 9 acts on the right end face of piston 68, and unloading valve 610 is closed slightly. The pressure in the forward gear working oil circuit 15 rises, and the friction plates of the forward gear clutch come into contact with each other, and the vehicle starts to move forward.

[0070] As the pressure in the forward gear working oil circuit 15 continues to rise, the pressure difference at both ends of piston 68 gradually decreases to zero. Spring 67 pushes piston 68 to reset, and unloading valve 610 is closed. The pressure in the forward gear working oil circuit 15 rises rapidly, and the friction plates of the forward gear clutch are tightly held together, and the vehicle moves forward. At the same time, the elimination of the pressure difference at both ends of piston 68 opens check valve 64, creating an oil passage condition for buffer valve 8 to release oil pressure in the next step.

[0071] When the directional control valve 4 is switched to the neutral position, ports ⑤ and ① of the directional control valve 4 are connected. The oil of the forward gear clutch passes through the forward gear working oil circuit 15, through ports ⑤ and ① of the directional control valve 4, and is unloaded to the return oil circuit 11. At the same time, the oil pressure stored in buffer valve 8 is released to the forward gear working oil circuit 15 through buffer oil circuit 17 and check valve 64, slowing down the rate of pressure drop in the forward gear working oil circuit 15, and making the loader decelerate and stop smoothly. The buffer spring 73 of buffer valve 8 pushes buffer piston 74 to reset, preparing to absorb oil pressure for the next directional change action.

[0072] Through the mutual cooperation of balance valve 9 and buffer valve 8, the loader operates smoothly without impact during the starting, forward movement, and stopping processes, improving driving comfort.

[0073] The buffer working principle for the reverse gear is the same as that for the forward gear and will not be repeated.

[0074] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A four-speed power reversing valve for a loader, characterized in that, it includes an upper valve body (1), a lower valve body (2), a flow dividing valve (3), a reversing valve (4), a shifting valve (5) arranged in the upper valve body (1), a balance valve one (7) and a balance valve two (9) arranged in the lower valve body (2); it also includes: a main oil supply circuit (10) for paralleling the oil inlet of the flow dividing valve (3) and the oil inlet of the shifting valve (5); an oil return circuit (11) for paralleling the oil return port of the flow dividing valve (3), the oil return port of the reversing valve (4), the oil return port of the shifting valve (5), the oil return port of the balance valve one (7), and the oil return port of the balance valve two (9); a reverse gear oil supply circuit (12) for connecting the oil outlet of the flow dividing valve (3) and the first oil inlet of the reversing valve (4); a forward gear oil supply circuit (13) for connecting the oil outlet of the flow dividing valve (3) and the second oil inlet of the reversing valve (4); a reverse gear working oil circuit (14) for paralleling the first oil outlet of the reversing valve (4), the oil inlet of the balance valve one (7), and the oil passage of the reverse gear clutch (KR); a forward gear working oil circuit (15) for paralleling the second oil outlet of the reversing valve (4), the oil inlet of the balance valve two (9), and the oil passage of the forward gear clutch (KF); a first gear working oil circuit (18) for connecting the first oil outlet of the shifting valve (5) and the oil passage of the first gear clutch (K1); a second gear working oil circuit (19) for connecting the second oil outlet of the shifting valve (5) and the oil passage of the second gear clutch (K2); a third gear working oil circuit (20) for connecting the third oil outlet of the shifting valve (5) and the oil passage of the third gear clutch (K3); a fourth gear working oil circuit (21) for connecting the fourth oil outlet of the shifting valve (5) and the oil passage of the fourth gear clutch (K4); wherein, the reversing valve (4) is a three-position five-way manual reversing valve, and a buffer valve one (6) and a buffer valve two (8) are further arranged on the lower valve body (2). The first oil port of the buffer valve one (6) is paralleled to the forward gear working oil circuit (15), and the second oil port of the buffer valve one (6) is connected to the back pressure oil port of the balance valve one (7) through a first buffer oil circuit (16); the first oil port of the buffer valve two (8) is paralleled to the reverse gear working oil circuit (14), and the second oil port of the buffer valve two (8) is connected to the back pressure oil port of the balance valve two (9) through a second buffer oil circuit (17); the buffer valve one (6) and the buffer valve two (8) have the same structure, and both include a valve body one and a stop pin (71), an inner cavity (72), a buffer spring (73) and a buffer piston (74) installed in the valve body one; the second oil port and the first oil port of the buffer valve one (6) are arranged on the valve body one and are located on both sides of the buffer piston (74), and one end of the first oil port of the buffer valve one (6) is communicated with the oil passage of the forward gear clutch (KF) or the oil passage of the reverse gear clutch (KR); The second balance valve (9) and the first balance valve (7) have the same structure, and both include a second valve body, a fourth spring (67) and a piston (68). The left end of the piston (68) and the second valve body form a left chamber (61), and the right end of the piston (68) and the second valve body form a right chamber (69). An oil passage two (65) communicating with the right chamber (69) is provided at the central position of the piston (68). A first throttle hole (62), an oil passage one (63) and a second throttle hole (66) are also provided on the piston (68). The oil inlet of the first balance valve (7) communicates with the left chamber (61) through the first throttle hole (62), the oil inlet of the first balance valve (7) communicates with the oil passage two (65) through the oil passage one (63), and the oil inlet of the first balance valve (7) communicates with the right chamber (69) through the second throttle hole (66). A check valve (64) is provided in the oil passage two (65) to allow the oil to flow only from the back pressure oil port of the first balance valve (7) to the oil inlet side; unloading valves (610) are formed at the positions corresponding to the oil inlet and the oil return port of the first balance valve (7) on the piston (68).

2. The four-speed power reversing valve for a loader according to claim 1, characterized in that, the fourth spring (67) is arranged in the right chamber (69); at the same time, an oil inlet, an oil return port and a back pressure oil port are provided on the second valve body, and the back pressure oil port communicates with the right chamber (69).

3. The four-speed power reversing valve for a loader according to claim 1, characterized in that, when the manually pushed and pulled reversing valve rod (41) is in the middle position, the first oil inlet and the second oil inlet of the reversing valve (4) are closed, and the first oil outlet, the second oil outlet and the oil return port communicate with each other; when the manually pushed and pulled reversing valve rod (41) is pushed inward, the second oil inlet and the second oil outlet of the reversing valve (4) communicate with each other, the first oil outlet and the oil return port communicate with each other, the first oil inlet is closed, and the oil in the forward gear oil supply circuit (13) enters the forward gear working oil circuit (15) through the second oil inlet and the second oil outlet; when the manually pushed and pulled reversing valve rod (41) is pulled outward, the first oil inlet and the first oil outlet of the reversing valve (4) communicate with each other, the second oil outlet and the oil return port communicate with each other, the second oil inlet is closed, the oil of the forward gear clutch flows through the second oil outlet and the oil return port of the reversing valve (4) to the oil return circuit (11) for unloading, and at the same time, the oil in the reverse gear oil supply circuit (12) enters the reverse gear working oil circuit (14) through the first oil inlet and the first oil outlet.

4. The four-speed power reversing valve for a loader according to claim 1, characterized in that, the shift valve (5) is a four-position six-way manual shift valve, having an oil inlet, an oil return port, a first oil outlet, a second oil outlet, a third oil outlet and a fourth oil outlet; when the shift valve (5) is in the first gear, the oil inlet of the shift valve (5) communicates with the first oil outlet, and the other oil ports communicate with each other; when the shift valve (5) is in the second gear, the oil inlet of the shift valve (5) communicates with the second oil outlet, and the other oil ports communicate with each other; when the shift valve (5) is in the third gear, the oil inlet of the shift valve (5) communicates with the third oil outlet, and the other oil ports communicate with each other; When the shift valve (5) is in the fourth gear, the oil inlet of the shift valve (5) communicates with the fourth oil outlet, and the other oil ports communicate with each other.

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