Hydraulic control valve

Abstract

The utility model discloses a hydraulic control valve which comprises a valve body, an oil pump and a conversion check valve. A gear shifting oil cavity is formed in the valve body, a slidable gear shifting piston is installed in the gear shifting oil cavity, and the moving positions of the gear shifting piston comprise the low-speed gear position and the high-speed gear position. Working oil passing through the low-gear oil inlet can apply pressure to one end of the gear shifting piston, and the engine can apply pressure to the other end of the gear shifting piston through the oil pump. The shift piston is controlled to move through pressure at two ends of the shift piston; when the gear shifting piston is kept at the high-gear position, working oil can enter the high-gear oil inlet of the gearbox only through the high-gear oil outlet by switching the check valve. By means of the arrangement, the defects of an original hydraulic downshift control mechanism are overcome, interlocking of gears and the rotating speed of an engine is achieved, and it is guaranteed that the gear shifting process is stable and smooth, and continuous power output is achieved.

Description

Technical Field

[0001] The utility model relates to the field of hydraulic control devices for construction machinery and agricultural machinery, and particularly relates to a hydraulic control valve. Background Art

[0002] The existing hydraulic control valves for agricultural machinery mainly function as gear shifting, and are mainly used on the gearboxes of agricultural machinery and construction machinery to adjust the working pressure of the gearbox clutch. However, the existing hydraulic control valves do not have a limiting function to control the gearbox from directly shifting from a high gear to a low gear when the engine is at a high speed.

[0003] The prior art with the publication number of CN104141780B discloses a method for shifting a shift transmission that can be switched between at least two transmission stages of a transmission device. The transmission device is driven by a hydrostatic transmission. In order to shift the gear of the shift transmission between the transmission stages, in the first step, the load of the shift transmission is unloaded, which is achieved by changing the input quantity of the hydraulic motor and / or the liquid intake per revolution of the hydraulic motor until the pressure difference preset on the hydraulic motor is lower, or by over-adjusting the brake valve device to the open position for closing the brake valve function. In the second step, the shift transmission is shifted into neutral. In the third step, the speed of the hydraulic motor is synchronously controlled electro-hydraulically. In the fourth step, the shift transmission is shifted into a new transmission stage. In the fifth step, the shift transmission is loaded.

[0004] The prior art requires unloading before shifting gears, and then monitoring the engine state, which is prone to stall risks. Moreover, since the engine speed is not constant when performing gear shifting, especially when directly shifting from a high engine speed to a low gear, it is easy to cause greater damage to the machine and there are significant safety hazards. Summary of the Utility Model

[0005] In order to solve the problem of unloading required before shifting gears in the prior art, the purpose of the utility model is to provide a hydraulic control valve, which realizes real-time connection between the engine speed and gear shifting through a valve group, making the gear shifting process smoother.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions: A hydraulic control valve includes a valve body, an oil pump, and a conversion check valve. A shift oil cavity is arranged in the valve body, and a slidable shift piston is installed in the shift oil cavity. The moving positions of the shift piston include a low gear position and a high gear position. The valve body is also provided with a low gear oil inlet, a low gear oil outlet, a high gear oil inlet, and a high gear oil outlet. The low gear oil inlet and the low gear oil outlet are both communicated with the shift oil cavity;

[0007] The conversion check valve includes a first oil inlet, a second oil inlet, and an oil passage; the first oil inlet and the second oil inlet are both communicated with the shift oil cavity, and the oil passage is communicated with the high-speed gear oil outlet; a first steel ball is arranged in the conversion check valve, and the first steel ball moves between the first oil inlet and the second oil inlet to seal the first oil inlet or the second oil inlet.

[0008] When the shift piston is in the low-speed gear position, the working oil sequentially enters the low-speed gear oil inlet of the gearbox after passing through the low-speed gear oil inlet, the shift piston, and the low-speed gear oil outlet.

[0009] When the shift piston remains in the high-speed gear position, by controlling the entry position of the working oil, the first oil inlet or the second oil inlet is blocked, so as to realize the connection of the low-speed gear oil inlet, the shift piston, the high-speed gear oil outlet, and the high-speed gear oil inlet of the gearbox, or the connection of the high-speed gear oil inlet, the shift piston, the high-speed gear oil outlet, and the high-speed gear oil inlet of the gearbox.

[0010] When the shift piston is in the low-speed gear position, the shift piston cuts off the oil passage between the low-speed gear oil inlet and the conversion check valve, and connects the oil passage between the high-speed gear oil inlet, the conversion check valve, and the high-speed gear oil outlet.

[0011] The working oil passing through the low-speed gear oil inlet can exert pressure on one end of the shift piston, and the engine can exert pressure on the other end of the shift piston through the oil pump; the movement of the shift piston is controlled by the pressure at both ends of the shift piston.

[0012] Preferably, a leakage check valve is installed on the valve body. One end of the oil passage where the leakage check valve is installed is communicated with the oil passage between the second oil inlet and the shift oil cavity, and the other end of the oil passage where the leakage check valve is installed is communicated with the oil passage between the shift oil cavity and the low-speed gear oil outlet.

[0013] Preferably, a control check valve is also installed on the valve body. The oil passage where the control check valve is installed is communicated with the oil passage of the low-speed gear oil inlet and the shift oil cavity, and the other end of the oil passage where the control check valve is installed is communicated with the inner oil passage on the valve body; the control check valve can limit the oil from the low-speed gear oil inlet to directly enter the inner oil passage.

[0014] Preferably, a return spring is also installed in the shift oil cavity. The return spring is arranged between the shift piston and the valve body; the return spring is used to drive the shift piston to move towards the low-speed gear position.

[0015] Preferably, the valve body includes a valve seat and a valve cover fixedly connected. The shift oil cavity is arranged in the valve seat, and the low-speed gear oil inlet, the low-speed gear oil outlet, the high-speed gear oil inlet, and the high-speed gear oil outlet are arranged on the valve cover.

[0016] Preferably, a connecting portion protrudes on the valve seat, and two axially arranged O-rings are sleeved outside the connecting portion; the control valve is fixed on the box body of the fuel tank through the connecting portion.

[0017] Preferably, a pressure limiting valve for ensuring that the maximum pressure of the lubricating oil does not exceed the limit is installed at the oil pump.

[0018] Preferably, the oil pump is integrally installed on the valve body.

[0019] Preferably, the oil pump is a two-way oil pump, and a part of the oil extracted by the oil pump is used to lubricate the parts, and the other part is used to apply pressure to the reversing piston 4.

[0020] Preferably, the valve body is provided with an oil suction hole for extracting oil.

[0021] The beneficial effects of the technical solution of the present utility model are as follows: the higher the engine speed, the greater the pressure given by the oil pump to the shift piston. In this way, when switching to a low gear at a high engine speed, the oil pump can still give a large pressure to the shift piston, keeping the shift piston in the high gear position. As a result, the oil flowing into the hydraulic downshift control mechanism through the low gear oil inlet will still flow out from the high gear oil outlet until the engine speed drops to a certain value, at which time the pressure difference at both ends of the shift piston reverses, and only then is the vehicle allowed to switch to the low gear for operation. In this way, the above solution closely monitors the engine speed and the vehicle's shifting process, achieving a high-speed locking function, overcoming the deficiencies of the original hydraulic downshift control mechanism, and realizing the interlock between the gear position and the engine speed. It makes the vehicle's shifting process smoother, reduces mechanical damage to components such as the engine, transmission, and drive axle, reduces the risk of failure and damage, and maintains continuous power output of the vehicle. Description of the Drawings

[0022] Figure 1 Structural schematic of the downshift control mechanism Figure 1 ;

[0023] Figure 2 Structural schematic of the downshift control mechanism Figure 2 ;

[0024] Figure 3 is Figure 1 Cross-sectional view taken along line A-A in

[0025] Figure 4 is Figure 1 Cross-sectional view taken along line B-B in

[0026] Figure 5 Hydraulic schematic diagram of the downshift control mechanism when the engine speed is low and the gear position is low gear;

[0027] Figure 6 Hydraulic schematic diagram of the downshift control mechanism when the engine speed is low and the gear position is high gear;

[0028] Figure 7Hydraulic schematic diagram of the downshift control mechanism when the engine is at high speed and the gear is in the high-speed gear;

[0029] Figure 8 Hydraulic schematic diagram of the downshift control mechanism when the engine is increased from low speed to high speed and the gear is in the low-speed gear;

[0030] Figure 9 Hydraulic schematic diagram of the downshift control mechanism when the engine is at high speed and the gear is switched from the high-speed gear to the low-speed gear.

[0031] Reference numerals: 1, pressure limiting valve; 2, leakage check valve; 3, conversion check valve; 4, shift piston; 5, control check valve; 6, inner gear of oil pump; 7, outer gear of oil pump; 8, low-speed gear oil outlet; 9, high-speed gear oil outlet; 10, high-speed gear oil inlet; 11, low-speed gear oil inlet; 12, valve seat; 13, valve cover; 14, oil suction hole; 15, oil filter; 16, lubrication throttle hole; 17, input shaft of oil pump; 18, O-ring; 19, reversing valve. Detailed implementation manners

[0032] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals indicate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0034] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more, unless otherwise clearly defined.

[0035] In the present utility model, unless otherwise clearly defined and limited, terms such as "installation", "connection", "linkage", "fixation", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0036] In the present utility model, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on the top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "beneath" and "under the bottom of" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature. Embodiment

[0037] As Figures 1 to 4 shown, the displayed hydraulic downshift control mechanism includes a valve body, an oil pump and a conversion check valve 3; a shift oil cavity is arranged inside the valve body, and a slidable shift piston 4 is installed in the shift oil cavity. The moving positions of the shift piston 4 include a low-speed gear position and a high-speed gear position; a low-speed gear oil inlet 11, a low-speed gear oil outlet 8, a high-speed gear oil inlet 10 and a high-speed gear oil outlet 9 are further arranged on the valve body, and the low-speed gear oil inlet 11 and the low-speed gear oil outlet 8 are both communicated with the shift oil cavity;

[0038] As Figure 9 shown, when the shift piston 4 is in the high-speed gear position, the working oil passing through the low-speed gear oil inlet 11 or the high-speed gear oil inlet flows out from the high-speed gear oil outlet 9 through the conversion check valve 3; when the shift piston 4 is in the low-speed gear position, the working oil passing through the low-speed gear oil inlet 11 flows out from the low-speed gear oil outlet 8 after passing through the shift piston 4, and the working oil passing through the high-speed gear oil inlet flows out from the high-speed gear oil outlet 9 through the shift piston 4 and the conversion check valve 3;

[0039] As Figures 5 to 9 shown, the conversion check valve 3 includes a first oil inlet, a second oil inlet and an oil through hole; the first oil inlet and the second oil inlet are both communicated with the shift oil cavity, and the oil through hole is communicated with the high-speed gear oil outlet 9; a first steel ball is arranged inside the conversion check valve 3, and the first steel ball moves between the first oil inlet and the second oil inlet to seal the first oil inlet or the second oil inlet;

[0040] When the shift piston is in the low gear position, the working oil sequentially passes through the low gear oil inlet 11, the shift piston 4, and the low gear oil outlet 8 and then enters the low gear oil inlet of the transmission;

[0041] When the shift piston 4 remains in the high gear position, by controlling the entry position of the working oil, the first oil inlet or the second oil inlet is blocked, so as to realize the connection between the low gear oil inlet 11, the shift piston 4, the high gear oil outlet 9 and the high gear oil inlet of the transmission, or the connection between the high gear oil inlet 10, the shift piston 4, the high gear oil outlet 9 and the high gear oil inlet of the transmission; Specifically, when the shift piston 4 is in the high gear position: the first oil inlet is connected to the low gear oil inlet 11 through the shift piston, the second oil inlet is connected to the high gear oil inlet 10 through the shift piston, and the oil through hole is connected to the high gear oil outlet 9; If the working oil enters the low gear oil inlet 11, after the working oil enters the first oil inlet of the conversion check valve 3 through the shift piston 4, the working oil pushes the first steel ball to block the second oil inlet of the conversion check valve 3, and the working oil is discharged from the high gear oil outlet 9 after passing through the oil through hole of the conversion check valve 3; If the working oil enters the high gear oil inlet 10, the working oil can enter the second oil inlet of the conversion check valve 3 through the shift piston 4, the working oil pushes the first steel ball to block the first oil inlet, and the working oil is discharged from the high gear oil outlet 9 after passing through the oil through hole of the conversion check valve 3;

[0042] When the shift piston 4 is in the low gear position, the shift piston 4 cuts off the oil path between the low gear oil inlet 11 and the conversion check valve 3, and connects the oil path between the high gear oil inlet 10, the conversion check valve 3 and the high gear oil outlet 9;

[0043] The working oil passing through the low gear oil inlet 11 can apply pressure to one end of the shift piston 4, and the oil pump can apply pressure to the other end of the shift piston 4; The movement of the shift piston 4 is controlled by the pressure at both ends of the shift piston 4.

[0044] With such a setting, the higher the engine speed, the greater the pressure exerted by the oil pump on the shift piston 4. This enables, after switching to the low gear at a high engine speed, the oil pump to still exert a relatively large pressure on the shift piston 4, keeping the shift piston 4 in the high gear position. As a result, the oil entering the hydraulic downshift control mechanism through the low gear oil inlet 11 will still flow out from the high gear oil outlet 9 until the engine speed drops to a certain value, at which point the pressure difference at both ends of the shift piston 4 reverses, and only then is the vehicle allowed to switch to the low gear for operation; In this way, the above solution closely links the engine speed with the vehicle's shifting process, achieving a high-speed locking function, overcoming the deficiencies of the original hydraulic downshift control mechanism, and realizing the interlock between the gear position and the engine speed; This makes the vehicle's shifting process smoother, reduces mechanical damage to components such as the engine, transmission, and drive axle, and lowers the risk of failure and damage.

[0045] In this embodiment, as Figure 2 shown, a leakage check valve 2 is installed on the valve body. One end of the oil passage where the leakage check valve 2 is installed is communicated with the oil passage between the second oil inlet and the shift oil chamber, and the other end of the oil passage where the leakage check valve 2 is installed is communicated with the oil passage between the shift oil chamber and the low-speed gear oil outlet 8. Further, a second steel ball is installed in the leakage check valve 2, and the second steel ball can block any port of the leakage check valve 2.

[0046] In this embodiment, a first force-receiving part and a second force-receiving part are oppositely arranged on the shift piston 4. An internal oil passage is arranged on the valve body, and the ports of the internal oil passage are all communicated with the reversing oil chamber. The oil flowing through the low-speed gear oil inlet 11 or the low-speed gear oil outlet 8 acts on the first force-receiving part of the shift piston 4 through the shift piston 4 and then through the internal oil passage; the oil flowing through the oil pump enters the valve body and acts on the second force-receiving part.

[0047] In this embodiment, a control check valve 5 is also installed on the valve body. The oil passage where the control check valve 5 is installed is communicated with the oil passage between the low-speed gear oil inlet 11 and the shift oil chamber, and the other end of the oil passage where the control check valve 5 is installed is communicated with the internal oil passage on the valve body; the control check valve 5 can limit the oil from the low-speed gear oil inlet 11 to directly enter the internal oil passage.

[0048] In this embodiment, a return spring is further installed in the shift oil chamber. The return spring is arranged between the shift piston and the valve body; the return spring is used to drive the shift piston to move towards the low-speed gear position.

[0049] In this embodiment, as Figure 1 shown, the valve body includes a valve seat 12 and a valve cover 13 which are fixedly connected. The shift oil chamber is arranged in the valve seat 12, and the low-speed gear oil inlet 11, the low-speed gear oil outlet 8, the high-speed gear oil inlet 10 and the high-speed gear oil outlet 9 are arranged on the valve cover 13.

[0050] In this embodiment, as Figure 1 and Figure 4 shown, a connecting portion protrudes on the valve seat 12, and two axially arranged O-rings 18 are sleeved outside the connecting portion; the hydraulic downshift control mechanism is fixed on the box body of the fuel tank through the connecting portion. Further preferably, a lubrication area is arranged in the valve seat 12, an oil suction hole 14 communicated with the lubrication area is arranged on the valve seat 12, and one end of the oil pump input shaft extends into the lubrication area; when the oil pump works, it can send the oil in the lubrication area to the end of the shift piston 4. Further preferably, the oil pump input shaft has an inner hole, and the oil in the lubrication area is sent to the end of the shift piston 4 through the inner hole of the oil pump input shaft; specifically, the oil pump can extract the oil in the fuel tank through the oil suction hole 14, and a throttle hole 16 communicated with the inner hole is arranged at the end of the oil pump input shaft extending into the lubrication area.

[0051] In this embodiment, as Figure 2As shown, a pressure limiting valve 5 for ensuring that the maximum pressure of the lubricating oil does not exceed the limit is installed at the oil pump. The pressure limiting valve 5 is installed in the lubrication area of the valve seat 12.

[0052] In this embodiment, as Figures 1 to 4 shown, the oil pump is integrally installed on the valve body; specifically, the oil pump includes an oil pump input shaft 17, an outer oil pump gear 7 and an inner oil pump gear 6 rotatably installed on the valve seat 12. The outer oil pump gear 7 is located inside the outer oil pump gear 7 and is in meshing transmission. The oil pump input shaft 17 is fixedly connected to the inner oil pump gear 6; one end of the oil pump input shaft 17 extends from the valve seat 12 and is provided with an internal spline, and the internal spline of the oil pump input shaft 17 is spline-connected to the output shaft installed on the oil tank body.

[0053] In this embodiment, the oil pump is a two-way oil pump; as Figure 4 shown, a part of the oil fluid in the lubrication area passes through the throttle hole 16 at the top of the oil pump input shaft 17 and goes to lubricate the parts through the inner hole of the oil pump input shaft 17, and the other part reaches the end of the shift piston 4 through the flow channel inside the valve body to provide a downshift interlock signal pressure for the shift piston 4.

[0054] In this embodiment, a filter 15 is installed at the oil suction hole 14 of the valve body.

[0055] In this embodiment, the working oil enters the low-speed gear inlet 11 or the high-speed gear inlet 10 through the reversing valve 19; the reversing valve 19 receives the shift signal and reverses according to the shift signal to make the working oil enter the high-speed gear inlet 10 or the low-speed gear outlet 8; further, the reversing valve 19 is an electromagnetic valve. Embodiment

[0056] A method for controlling a vehicle to downshift by using the hydraulic downshift control mechanism described in the above Embodiment 1:

[0057] Among them, if the gear is shifted to the low-speed gear, at this time, since the engine is still in a high-speed state, the pressure given by the engine to the shift piston 4 is greater than the working oil pressure, and the shift piston 4 remains in the high-speed position. The working oil passes through the low-speed gear inlet 11, the shift piston 4 and the high-speed gear outlet 9 in sequence and then enters the high-speed gear inlet of the transmission; among them, the oil path from the high-speed gear inlet 10 to the high-speed gear outlet 9 through the shift piston 4 is blocked; when the engine speed drops to the low-speed, the shift piston 4 moves to the low-speed gear position, and the working oil passes through the low-speed gear inlet 11, the shift piston 4 and the low-speed gear outlet 8 in sequence and then enters the low-speed gear inlet of the transmission. Among them, when the shift piston 4 is in the high-speed gear position, by the working oil entering the port of the conversion check valve 3, the steel ball blocks the first oil inlet or the second oil inlet, and further controls the conversion check valve 3 to cut off the high-speed gear inlet 10 and the high-speed gear outlet 9, or controls the conversion check valve 3 to be able to cut off the oil path between the low-speed gear inlet 11 and the high-speed gear outlet 9.

[0058] Specifically, as Figure 5 shown, when the vehicle engine is at a low speed and the vehicle is in a low gear: The pressure oil enters the low gear oil inlet 11 through the reversing valve 19. The oil in the low gear oil inlet 11 is divided into two paths. One path acts on the first force-receiving part through the shifting piston 4 and the internal oil passage on the valve body, so that the shifting piston 4 is kept in the low gear position under the action of the return spring and the pressure oil. The other path of the oil pressure oil directly flows out from the low gear oil outlet 8 after passing through the shifting piston 4, and then the oil enters the low gear oil inlet 11 of the transmission. The high gear return oil flows back to the fuel tank from the reversing valve 19 after passing through the high gear oil outlet 9, the conversion check valve 3, the shifting piston 4 and the high gear oil inlet 10.

[0059] As Figure 8 shown, when the vehicle engine is at a low speed and the vehicle is in a low gear, if the engine speed rises to a high speed and the pressure of the oil pump acting on the shifting piston 4 reaches 2.8 bar, which is the pressure to push the shifting piston 4, since the working oil pressure in the low gear of the vehicle is much greater than 2.8 bar at this time, the shifting piston 4 can be kept in the low speed position, and the pressure oil still flows out from the low gear oil outlet 8.

[0060] As Figure 6 shown, when the vehicle engine is at a low speed and the vehicle is in a high gear: At this time, since the rotational speed of the oil pump driven by the engine is low, the pressure given by the oil pump to the shifting piston 4 is not enough to drive the shifting piston 4 to move, so the shifting piston 4 is kept in the low speed position. The pressure oil enters the high gear oil inlet 10 of the hydraulic downshift control mechanism through the reversing valve 19, and then the pressure oil sequentially enters the conversion check valve 3 from the second oil inlet through the shifting piston 4. The oil entering the conversion check valve 3 pushes the first steel ball to block the first oil inlet, and then the pressure oil enters the high-speed oil inlet of the transmission after passing through the oil through-hole and the high gear oil outlet 9. The oil that needs to perform the oil return action flows back to the fuel tank through the low gear oil return, the shifting piston 4 and the reversing valve 19.

[0061] As Figure 7As shown, when the vehicle engine is at high speed and the vehicle is in the high gear, both the low-speed oil inlet and the low-speed oil outlet are in the pressure relief state. When the engine is at high speed, the oil pump applies a greater pressure to the shift piston 4, keeping the shift piston 4 in the high-speed position. Among them, the pressure oil entering the hydraulic downshift control mechanism through the reversing valve 19 enters the second oil inlet of the conversion check valve 3 after passing through the shift piston 4, thereby sealing the first oil inlet of the conversion check valve 3. The pressure oil enters the high-speed oil inlet of the gearbox through the oil passage of the conversion check valve 3 and the high-speed oil outlet 9 on the valve body. Among them, the oil that needs to be returned passes through the low-speed oil return port and the shift piston 4 and then acts on the first force-receiving part of the shift piston 4 and the control check valve 5 in the valve body through the internal oil passage on the valve body. The oil flowing out of the control check valve 5 flows back to the fuel tank through the low-speed oil inlet 11 and the reversing valve 19.

[0062] As Figure 9 shown, when the vehicle engine is at high speed and the vehicle is in the high gear, if the gear is shifted from the high gear to the low gear, the pressure oil enters the hydraulic downshift control mechanism from the low-speed oil inlet 11 of the reversing valve 19. However, due to the action of the control check valve 5, the pressure oil cannot directly act on the first force-receiving part of the shift piston 4. And at this time, the engine is still at high speed. At this time, the pressure applied by the oil pump on the second force-receiving part is greater than the pressure on the first force-receiving part, thereby keeping the shift piston 4 in the high-gear position. The pressure oil enters the conversion check valve 3 from the second oil inlet after passing through the low-speed oil inlet 11 and the shift piston 4. The first steel ball inside the conversion check valve 3 seals the first oil inlet. The pressure oil enters the high-speed oil inlet of the gearbox through the oil passage and the high-speed oil outlet 9. Only when the engine speed drops to the low-speed state, the shift piston 4 returns to the low-speed position, and the pressure oil flows directly out of the low-speed oil outlet 8 through the shift piston 4.

[0063] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0064] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A hydraulic control valve, characterized in that: It includes a valve body, an oil pump and a conversion check valve (3); a shift oil cavity is arranged in the valve body, a slidable shift piston (4) is installed in the shift oil cavity, and the moving positions of the shift piston (4) include a low gear position and a high gear position; the valve body is also provided with a low gear oil inlet (11), a low gear oil outlet (8), a high gear oil inlet (10) and a high gear oil outlet (9), and the low gear oil inlet (11) and the low gear oil outlet (8) are both communicated with the shift oil cavity; The conversion check valve (3) includes a first oil inlet, a second oil inlet and an oil passage; both the first oil inlet and the second oil inlet are communicated with the shift oil cavity, and the oil passage is communicated with the high gear oil outlet (9); a first steel ball is arranged in the conversion check valve (3), and the first steel ball moves between the first oil inlet and the second oil inlet to seal the first oil inlet or the second oil inlet; When the shift piston (4) is in the low gear position, the working oil sequentially enters the low gear oil inlet of the gearbox after passing through the low gear oil inlet (11), the shift piston (4) and the low gear oil outlet (8); When the shift piston (4) remains in the high gear position, by controlling the entering position of the working oil, the blocking of the first oil inlet or the second oil inlet is further controlled, so as to realize the connection between the low gear oil inlet (11), the shift piston (4), the high gear oil outlet (9) and the high gear oil inlet of the gearbox, or the connection between the high gear oil inlet (10), the shift piston (4), the high gear oil outlet (9) and the high gear oil inlet of the gearbox; When the shift piston (4) is in the low gear position, the oil passage between the low gear oil inlet (11) and the conversion check valve (3) is cut off by the shift piston (4), and the oil passage between the high gear oil inlet (10), the conversion check valve (3) and the high gear oil outlet (9) is communicated; The working oil passing through the low gear oil inlet (11) can apply pressure to one end of the shift piston (4), and the engine can apply pressure to the other end of the shift piston (4) through the oil pump; the movement of the shift piston (4) is controlled by the pressure at both ends of the shift piston (4).

2. The hydraulic control valve according to claim 1, characterized in that: A leakage check valve (2) is installed on the valve body. One end of the oil passage where the leakage check valve (2) is installed is communicated with the oil passage between the second oil inlet and the shift oil cavity, and the other end of the oil passage where the leakage check valve (2) is installed is communicated with the oil passage between the shift oil cavity and the low gear oil outlet (8).

3. A hydraulic control valve according to claim 1, characterized in that: A control check valve (5) is also installed on the valve body. The oil passage where the control check valve (5) is installed is communicated with the oil passage between the low gear oil inlet (11) and the shift oil cavity, and the other end of the oil passage where the control check valve (5) is installed is communicated with the inner oil passage on the valve body; the control check valve (5) can limit the oil from the low gear oil inlet (11) to directly enter the inner oil passage.

4. A hydraulic control valve according to claim 1, wherein: A return spring is also installed in the shift oil cavity, and the return spring is arranged between the shift piston (4) and the valve body; the return spring is used to drive the shift piston (4) to move towards the low gear position.

5. A hydraulic control valve according to claim 1, characterized in that: The valve body includes a valve seat (12) and a valve cover (13) fixedly connected. The shift oil cavity is arranged in the valve seat (12), and the low gear oil inlet (11), the low gear oil outlet (8), the high gear oil inlet (10) and the high gear oil outlet (9) are arranged on the valve cover (13).

6. A hydraulic control valve according to claim 5, characterized in that: The valve seat (12) has a raised connecting portion, and two axially arranged O-rings (18) are sleeved outside the connecting portion; the control valve is fixed on the tank body through the connecting portion.

7. A hydraulic control valve according to claim 1, wherein: A pressure limiting valve (1) for ensuring that the maximum pressure of the lubricating oil does not exceed the limit is installed at the oil pump.

8. A hydraulic control valve according to claim 1, wherein: The oil pump is integrally installed on the valve body.

9. A hydraulic control valve according to claim 1, characterized in that: The oil pump is a two-way oil pump, and a part of the oil drawn by the oil pump is used to lubricate parts, and the other part is used to apply pressure to the shift piston (4).

10. A hydraulic control valve according to claim 1, characterized in that: The valve body is provided with an oil suction hole (14) for drawing oil.

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