Variable mechanism and hydraulic system

Abstract

The application provides a variable mechanism and a hydraulic system, and relates to the technical field of hydraulic control. The variable mechanism comprises a pressure regulating valve, the pressure regulating valve comprises a valve body, a valve core, a pressure regulating elastic element, a variable piston and a switch structure, the valve body is provided with a first cavity, a second cavity, a first flow channel and a second flow channel, and the two ends of the two flow channels are respectively communicated with the first cavity and the second cavity; the valve core is slidingly connected to the first cavity, one end of the variable piston is slidingly connected to the second cavity, and the variable piston is connected with a swash plate of a constant-pressure variable piston pump; when the constant-pressure variable piston pump is in a shutdown state, the variable piston is returned to an initial position, the switch structure is used for controlling the second flow channel to be communicated with or disconnected from the second cavity, and the pressure regulating elastic element drives the valve core to cut off the first flow channel. The overshoot of the outlet pressure of the constant-pressure variable piston pump when the constant-pressure variable piston pump is started can be timely and significantly reduced.

Description

Technical Field

[0001] This invention relates to the field of hydraulic control technology, and more specifically, to a variable mechanism and a hydraulic system. Background Technology

[0002] Constant pressure variable displacement piston pumps are characterized by high response speed and the ability to maintain a high-pressure, low-flow standby state. When the hydraulic system load demands flow, the constant pressure variable displacement piston pump can provide high pressure and high flow to the load in a very short time. They are widely used in hydraulic systems with high response requirements, such as aircraft and missile control mechanisms. The working principle of a constant pressure variable displacement piston pump is typically achieved by adjusting the displacement through a variable mechanism to meet the load's different flow rate requirements, and to bring the pump's output pressure towards a constant value. When the pump stops, it returns to its initial high-displacement state under the drive of the variable mechanism.

[0003] However, when a constant pressure variable displacement piston pump starts at a large displacement, the pump outlet pressure may exceed the pump's rated pressure due to the rapid increase in pump outlet pressure. Furthermore, the variable mechanism has a certain lag in the movement of the valve core, which causes the variable piston that drives the pump's swashplate angle to change to not respond in time. Consequently, the variable piston fails to displace in time to push the swashplate to rotate and cause the pump to change displacement. The pump remains in a large displacement state. In addition, the pressure overshoot results in a very high instantaneous torque when the pump starts, which is the product of pressure and displacement. This poses a certain safety hazard. Summary of the Invention

[0004] The present invention aims to solve the problem of certain safety hazards in constant pressure variable displacement piston pumps during large displacement startup.

[0005] To solve the above problems, the present invention provides a variable mechanism, the variable mechanism including a pressure regulating valve, the pressure regulating valve including a valve body, a valve core, a pressure regulating elastic element, a variable piston and a switching structure, the valve body having a first cavity, a second cavity, a first flow channel and a second flow channel inside, the first end of the first flow channel and the first end of the second flow channel respectively communicating with the first cavity, the second end of the first flow channel and the second end of the second flow channel respectively communicating with the second cavity;

[0006] The valve core is slidably connected to the first cavity, the pressure regulating elastic element abuts against the inner end of the first cavity and the valve core respectively, the variable piston is slidably connected to the second cavity, and one end of the variable piston extends out of the second cavity and is used to connect to the swashplate of the constant pressure variable piston pump.

[0007] When the constant pressure variable piston pump is in the stopped state, the variable piston returns to the initial position, the switching structure is used to control the connection or disconnection between the second flow channel and the second cavity, and the pressure regulating elastic element is used to drive the valve core to cut off the flow in the first flow channel.

[0008] The variable mechanism provided by this invention, compared with the prior art, has, but is not limited to, the following technical problems:

[0009] When this variable mechanism is used in conjunction with a constant pressure variable displacement piston pump, when the constant pressure variable displacement piston pump is in a stopped state, the swashplate is in the initial large displacement position, which will also drive the variable piston connected to it to return to the initial position. Since there is no oil pressure inside the valve body when the constant pressure variable displacement piston pump is stopped, the pressure regulating elastic element will drive the valve core to move and reset to cut off the flow in the first flow channel. Thus, when the constant pressure variable displacement piston pump starts from a large displacement shutdown state, the second flow channel and the second chamber can be connected simultaneously through the switching structure. In this way, even if the outlet pressure of the constant pressure variable displacement piston pump increases instantaneously, exceeding the rated pressure of the constant pressure variable displacement piston pump, this instantaneous large pressure does not need to overcome the elastic force of the pressure regulating element to drive the valve core to move and open the first flow channel. Instead, it directly enters the second chamber through the second flow channel, bypassing the valve core and acting directly on the variable piston to drive the variable piston to move first. Then, the variable piston directly absorbs the pressure shock when the constant pressure variable displacement piston pump starts, so that the overshoot of the outlet pressure when the constant pressure variable displacement piston pump starts is reduced in a timely and significant manner, unaffected by the hysteresis of the valve core, ensuring the safety of the pump and the hydraulic system. When the constant pressure variable displacement piston pump starts, after the variable piston moves to the set distance, the second flow channel and the second chamber can be disconnected by the switching structure. At this time, the oil pressure entering the first chamber has just dropped to within the rated pressure of the constant pressure variable displacement piston pump. At this time, the oil pressure entering the first chamber can only overcome the large preload of the pressure regulating elastic element, such as the spring, to make the valve core move, and then make the oil in the first chamber enter the second chamber from the first flow channel to meet the basic constant pressure variable displacement characteristics of the constant pressure variable displacement piston pump.

[0010] Furthermore, the switching structure includes a transition groove and a recess, the transition groove being disposed on the inner wall of the second cavity at a position between the second end of the first flow channel and the second end of the second flow channel, and the recess being disposed on the peripheral side of the variable piston;

[0011] When the constant pressure variable piston pump is in the stopped state, the variable piston returns to its initial position so that the second flow channel communicates with the cavity and the transition groove connects the second cavity with the cavity.

[0012] Furthermore, the variable mechanism also includes a return structure connected to the swashplate; when the constant pressure variable piston pump is in a stopped state, the return structure is used to drive the swashplate to rotate to the initial large displacement position, and the rotation of the swashplate drives the variable piston to move to the initial position.

[0013] Furthermore, the return structure includes a cylinder, a return spring, and a return piston. The return piston is slidably connected to the cylinder, one end of the return piston extends out of the cylinder and is connected to the swashplate, and the other end of the return piston is connected to the inner end of the cylinder through the return spring.

[0014] Furthermore, the first cavity includes a first small-diameter cavity and a first large-diameter cavity. The inner end of the first small-diameter cavity is connected to the first large-diameter cavity. The valve core includes a valve stem and a pressure regulating piston. The pressure regulating valve also includes a valve sleeve. The valve sleeve is disposed on the inner wall of the first small-diameter cavity. The inner diameter of the valve sleeve is the same as the diameter of the pressure regulating piston. The pressure regulating piston is fixedly sleeved on the valve stem. The pressure regulating piston is slidably connected to the first small-diameter cavity. The pressure regulating elastic element abuts against the inner end of the first large-diameter cavity and the valve stem, respectively.

[0015] Furthermore, the valve core also includes a limiting block, which is fixed to the portion of the valve stem that extends into the first large-diameter cavity. The diameter of the limiting block is greater than the inner diameter of the valve sleeve, and the diameter of the limiting block is less than or equal to the inner diameter of the first small-diameter cavity. The pressure regulating elastic element abuts against the inner end of the first large-diameter cavity and the limiting block, respectively.

[0016] Furthermore, the pressure regulating elastic element is a first spring, one end of which abuts against the inner end of the first large-diameter cavity, and the other end of which is sleeved on the valve stem and abuts against the limiting block.

[0017] Furthermore, the valve sleeve is provided with a first through hole and a second through hole, the first through hole being connected to the first flow channel and the second through hole being connected to the second flow channel.

[0018] Furthermore, the first flow channel includes a first annular flow channel and a first straight flow channel. The first annular flow channel is disposed on the inner wall of the first small-diameter cavity and surrounds the first small-diameter cavity. The two ends of the first straight flow channel are respectively connected to the first annular flow channel and the second cavity.

[0019] And / or, the second flow channel includes a second annular flow channel and a second straight flow channel, the second annular flow channel is disposed on the inner wall of the first small diameter cavity and surrounds the first small diameter cavity, and the two ends of the second straight flow channel are respectively connected to the first annular flow channel and the second cavity.

[0020] The present invention also provides a hydraulic system including a constant pressure variable displacement piston pump and a variable displacement mechanism as described above, wherein the variable displacement piston of the variable displacement mechanism is connected to the swashplate of the constant pressure variable displacement piston pump.

[0021] Since the technical improvements and beneficial effects of the hydraulic system are at least the same as those of the variable mechanism, the hydraulic system will not be described in detail here. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the variable mechanism in an embodiment of the present invention.

[0023] Explanation of reference numerals in the attached figures:

[0024] 1. Valve body; 11. First cavity; 111. First small-diameter cavity; 112. First large-diameter cavity; 12. First flow channel; 121. First annular flow channel; 122. First straight flow channel; 13. Second flow channel; 131. Second annular flow channel; 132. Second straight flow channel; 14. Second cavity; 141. Transition groove; 2. Valve core; 21. Valve stem; 22. Pressure regulating piston; 23. Limiting block; 3. Pressure regulating elastic element; 4. Variable piston; 41. Cavity; 5. Swashplate; 6. Return structure; 61. Cylinder; 62. Return spring; 63. Return piston; 7. Valve sleeve; 71. First through hole; 72. Second through hole. Detailed Implementation

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0026] In the description of this invention, it should be understood that the terms "front" and "rear", 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 this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0027] Furthermore, in the attached diagram, the X-axis represents the vertical direction, that is, the front and back position, and the positive direction of the X-axis (that is, the direction the arrow on the X-axis points) represents the front, and the negative direction of the X-axis (that is, the direction opposite to the positive direction of the X-axis) represents the back; the direction indicated by the arrow Y in the attached diagram is the direction of the swashplate's counterclockwise rotation.

[0028] It should also be noted that the aforementioned X-axis designation is only for the purpose of facilitating the description of the present invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0029] Traditional constant-pressure variable displacement piston pumps experience a rapid increase in outlet pressure during high-displacement startup, potentially exceeding the pump's rated pressure. Furthermore, the variable displacement mechanism, due to the lag in valve spool movement, means the variable piston, which drives the swashplate angle, cannot respond promptly. This results in the variable piston failing to displace and rotate the swashplate in time, causing the pump to remain in a high-displacement state. Combined with this pressure overshoot, the product of pressure and displacement (i.e., the instantaneous starting torque) becomes very high, posing safety hazards. For example, it can cause a high instantaneous current in the pump motor, putting strain on the motor and the drive shaft, potentially leading to shaft breakage. Particularly concerning is the increased outlet pressure overshoot and longer valve spool response time during low-temperature startup, especially with constant-pressure variable displacement piston pumps, due to the influence of oil viscosity, further exacerbating the safety risks to the motor and pump.

[0030] Specifically, some existing solutions involve designing a larger diameter drive shaft for the pump. However, this approach not only fails to address the issue of high instantaneous current in the motor, but even if a larger diameter drive shaft does not pose a risk of breakage, it also increases the pump's weight without altering its maximum output power. This reduces the power-to-weight ratio of the pump and even the motor, making it counterproductive.

[0031] Based on the above issues, see Figure 1 This embodiment provides a variable mechanism, including a pressure regulating valve. The pressure regulating valve includes a valve body 1, a valve core 2, a pressure regulating elastic element 3, a variable piston 4, and a switching structure. The valve body 1 is provided with a first cavity 11, a second cavity 14, a first flow channel 12, and a second flow channel 13. The first end of the first flow channel 12 and the first end of the second flow channel 13 are respectively connected to the first cavity 11, and the second end of the first flow channel 12 and the second end of the second flow channel 13 are respectively connected to the second cavity 14.

[0032] The valve core 2 is slidably connected to the first cavity 11, the pressure regulating elastic element 3 abuts against the inner end of the first cavity 11 and the valve core 2 respectively, the variable piston 4 is slidably connected to the second cavity 14, and one end of the variable piston 4 extends out of the second cavity 14 and is used to connect to the swashplate 5 of the constant pressure variable piston pump.

[0033] When the constant pressure variable piston pump is in the stopped state, the variable piston 4 returns to the initial position, the switching structure is used to control the connection or disconnection between the second flow channel 13 and the second cavity 14, and the pressure regulating elastic element 3 is used to drive the valve core 2 to cut off the flow in the first flow channel 12.

[0034] It is understood that one end of the first cavity 11 is used as a hydraulic inlet, and the other end is a closed end; the inner end of the first cavity 11 refers to the closed end. The two ends of the first flow channel 12 and the second flow channel 13 are respectively connected to the side wall of the first cavity 11 and the side wall of the second cavity 14.

[0035] In this embodiment, after the variable mechanism is used in conjunction with the constant pressure variable piston pump, when the constant pressure variable piston pump is in the shutdown state, since the swashplate 5 is in the initial large displacement position, the swashplate 5 in the initial large displacement position will also drive the variable piston 4 connected to it to return to the initial position. Since there is no oil pressure inside the valve body 1 when the constant pressure variable piston pump is in the shutdown state, the pressure regulating elastic element 3 will drive the valve core 2 to move and reset to cut off the flow in the first flow channel 12. Thus, when the constant pressure variable displacement piston pump starts from a large displacement shutdown state, the second flow channel 13 and the second chamber 14 can be connected simultaneously through the switching structure. In this way, even if the outlet pressure of the constant pressure variable displacement piston pump increases instantaneously and exceeds the rated pressure of the constant pressure variable displacement piston pump, this instantaneous large pressure does not need to overcome the elastic force of the pressure regulating elastic element 3 to drive the valve core 2 to move and open the first flow channel 12. Instead, it directly enters the second chamber 14 through the second flow channel 13, thus bypassing the valve core 2 and acting directly on the variable piston 4 to drive the variable piston 4 to move first. Then, the variable piston 4 directly absorbs the pressure shock when the constant pressure variable displacement piston pump starts, so that the overshoot of the outlet pressure when the constant pressure variable displacement piston pump starts is reduced in a timely and significant manner, without being affected by the lag of the valve core 2, ensuring the safety of the pump and the hydraulic system. When the constant pressure variable piston pump starts, after the variable piston 4 moves to the set distance, the second flow channel 13 and the second chamber 14 can be disconnected by the switch structure. At this time, the oil pressure entering the first chamber 11 has just dropped to within the rated pressure of the constant pressure variable piston pump. At this time, the oil pressure entering the first chamber 11 can only overcome the large preload of the pressure regulating elastic element 3, such as the spring, to make the valve core 2 move, so that the oil in the first chamber 11 can enter the second chamber 14 from the first flow channel 12 to meet the basic constant pressure variable characteristics of the constant pressure variable piston pump.

[0036] In this embodiment, the variable mechanism solves the problem of pressure overshoot during startup of the constant pressure variable piston pump, as well as the problem of large instantaneous current of the motor. It does not affect the basic variable characteristics of the constant pressure variable piston pump. At the same time, it does not require a large diameter of the pump's drive shaft, nor does it reduce the power-to-weight ratio of the pump or even the motor.

[0037] See Figure 1 Optionally, the switching structure includes a transition groove 141 and a cavity 41. The transition groove 141 is located on the inner wall of the second cavity 14 between the second end of the first flow channel 12 and the second end of the second flow channel 13. The cavity 41 is located on the circumferential side of the variable piston 4.

[0038] When the constant pressure variable displacement piston pump is in the stopped state, the variable piston 4 returns to the initial position so that the second flow channel 13 is connected to the cavity 41 and the transition groove 141 connects the second cavity 14 to the cavity 41.

[0039] In this embodiment, when the constant pressure variable displacement piston pump is in the shutdown state, as the variable piston 4 returns to its initial position, the concave cavity 41 on the peripheral side of the variable piston 4 will connect with the second end of the second flow channel 13, and then the concave cavity 41 on the peripheral side of the variable piston 4 will connect with the first cavity 11. At the same time, the transition groove 141 on the inner wall of the second cavity 14 connects the concave cavity 41 with the second cavity 14. Since there is no oil pressure inside the valve body 1 when the constant pressure variable displacement piston pump is in the shutdown state, the pressure regulating elastic element 3 will drive the valve core 2 to move and reset to cut off the flow in the first flow channel 12.

[0040] Thus, when the constant pressure variable displacement piston pump starts from a large displacement shutdown state, even if the outlet pressure of the constant pressure variable displacement piston pump increases instantaneously, exceeding the rated pressure of the constant pressure variable displacement piston pump, this instantaneous large pressure does not need to first overcome the elastic force of the pressure regulating elastic element 3 to drive the valve core 2 to move and open the first flow channel 12. Instead, it directly enters the concave cavity 41 on the peripheral side of the variable piston 4 through the second flow channel 13, and then enters the second cavity 14 through the transition groove 141. This allows it to bypass the valve core 2 and act directly on the variable piston 4, driving the variable piston 4 to move forward first. Then, the variable piston 4 directly absorbs the pressure shock when the constant pressure variable displacement piston pump starts, so that the overshoot of the outlet pressure when the constant pressure variable displacement piston pump starts is reduced in a timely and significant manner, without being affected by the lag of the valve core 2, ensuring the safety of the pump and hydraulic system operation.

[0041] When the constant pressure variable displacement piston pump starts, after the variable piston 4 moves forward a set distance, the concave cavity 41 can no longer connect with the second cavity 14 through the transition groove 141. That is, the oil pressure entering the second flow channel 13 from the first cavity 11 can no longer drive the variable piston 4 to move. At this time, the oil pressure entering the first cavity 11 has been reduced to within the rated pressure of the constant pressure variable displacement piston pump. At this time, the oil pressure entering the first cavity 11 can only overcome the large preload of the pressure regulating elastic element 3, such as the spring, to make the valve core 2 move, and then make the oil in the first cavity 11 enter the second cavity 14 from the first flow channel 12 to meet the basic variable characteristics of the constant pressure variable displacement piston pump.

[0042] It should be noted that, as Figure 1As shown, the variable piston 4 is in its initial position. At this time, the rear part of the transition groove 141 is connected to the second cavity 14, and the front part of the transition groove 141 is connected to the concave cavity 41. When the variable piston 4 moves forward a distance L (the aforementioned set distance), the concave cavity 41 is no longer connected to the transition groove 141. That is, the concave cavity 41 cannot be connected to the second cavity 14 through the transition groove 141 (this can also be referred to as the second flow channel 13 being disconnected from the second cavity 14). From this moment on, in the hydraulic system, the variable mechanism adjusts the displacement of the constant pressure variable piston pump to meet the load's demand for different flow rates, while simultaneously keeping the internal pressure of the system constant, satisfying the basic variable characteristics of the constant pressure variable piston pump. In order not to affect the basic variable characteristics of the constant pressure variable piston pump, the distance L is extremely small.

[0043] Optionally, the switching structure includes a solenoid valve disposed within the second flow channel 13, which can then be used to control the opening and closing of the second flow channel 13. Thus, the disconnection between the second flow channel and the second cavity 14 can also be controlled by the solenoid valve. Therefore, the distance L can be unlimited (of course, the transition groove 141 and the concave cavity 41 can also be omitted). When the constant pressure variable displacement piston pump starts, the solenoid valve is simultaneously controlled to connect the second flow channel 13 and the second cavity 14. The timing of disconnecting the second flow channel 13 can be selected according to actual needs, such as 2 seconds, 3 seconds, or 4 seconds after the constant pressure variable displacement piston pump starts. By setting a precise disconnection time, the impact on the basic variable characteristics of the constant pressure variable displacement piston pump can be minimized or even eliminated.

[0044] See Figure 1 Optionally, the variable mechanism further includes a return structure 6, which is connected to the swashplate 5. When the constant pressure variable piston pump is in a stopped state, the return structure 6 is used to drive the swashplate 5 to rotate to the initial large displacement position, and drive the variable piston 4 to move to the initial position through the rotation of the swashplate 5.

[0045] In this embodiment, the variable displacement mechanism controlling the constant pressure variable displacement piston pump includes not only a pressure regulating valve but also a return structure 6. Thus, when the constant pressure variable displacement pump is in a stopped state, the return structure 6 can drive the swashplate 5 to rotate counterclockwise until it returns to the initial high displacement position. Simultaneously, the swashplate 5, returning to the initial high displacement position, also drives the variable displacement piston 4 back to its initial position. Figure 1 The location shown.

[0046] See Figure 1Optionally, the return structure 6 includes a cylinder 61, a return spring 62, and a return piston 63. The return piston 63 is slidably connected to the cylinder 61. One end of the return piston 63 extends out of the cylinder 61 and is connected to the swashplate 5. The other end of the return piston 63 is connected to the inner end of the cylinder 61 through the return spring 62.

[0047] In this embodiment, when the swashplate 5 is in the initial large displacement position, the return spring 62 has a certain preload (small enough to keep the swashplate 5 in the initial large displacement position). When the constant pressure variable displacement piston pump is started from the large displacement shutdown state, even if the outlet pressure of the constant pressure variable displacement piston pump increases instantaneously and exceeds the rated pressure of the constant pressure variable displacement piston pump, this instantaneous large pressure does not need to overcome the elastic force of the pressure regulating elastic element 3 to drive the valve core 2 to move and open the first flow channel 12. Instead, it directly enters the concave cavity 41 on the peripheral side of the variable piston 4 through the second flow channel 13, and then enters the second cavity 14 through the transition groove 141. This allows it to bypass the valve core 2 and act directly on the variable piston 4. Only the small preload of the return spring 62 is needed to drive the variable piston 4 to move forward first, thereby absorbing the pressure shock when the constant pressure variable displacement piston pump starts, so that the overshoot of the outlet pressure when the constant pressure variable displacement piston pump starts is reduced in a timely and significant manner.

[0048] See Figure 1 Optionally, the first cavity 11 includes a first small-diameter cavity 111 and a first large-diameter cavity 112. The inner end (front end) of the first small-diameter cavity 111 is connected to the first large-diameter cavity 112. The pressure regulating valve also includes a valve sleeve 7, which is disposed on the inner wall of the first small-diameter cavity 111. The inner diameter of the valve sleeve 7 is the same as the diameter of the pressure regulating piston 22. The valve core 2 includes a valve stem 21 and a pressure regulating piston 22. The pressure regulating piston 22 is fixedly sleeved on the valve stem 21 and slidably connected to the first small-diameter cavity 111. The pressure regulating elastic element 3 abuts against the inner end of the first large-diameter cavity 112 and the valve stem 21, respectively.

[0049] In this embodiment, during installation, the pressure regulating elastic element 3 can be first installed into the first large-diameter cavity 112, then the pressure regulating piston 22 can be installed into the valve sleeve 7, and then the valve sleeve 7 can be installed into the first small-diameter cavity 111. Finally, the rear end of the first small-diameter cavity 111 can be closed. The first large-diameter cavity 112 provides space for the installation and deformation of the pressure regulating elastic element 3, the first small-diameter cavity 111 provides installation space for the valve sleeve 7, and the valve sleeve 7 provides space for the movement of the pressure regulating piston 22.

[0050] See Figure 1Optionally, the valve core 2 further includes a limiting block 23, which is fixed to the portion of the valve stem 21 that extends into the first large-diameter cavity 112. The diameter of the limiting block 23 is greater than the inner diameter of the valve sleeve 7, and the diameter of the limiting block 23 is less than or equal to the inner diameter of the first small-diameter cavity 111. The pressure regulating elastic element 3 abuts against the inner end of the first large-diameter cavity 112 and the limiting block 23, respectively.

[0051] In this embodiment, since the diameter of the limiting block 23 is less than or equal to that of the first small diameter cavity 111, the valve sleeve 7 and the valve core 2 can be installed together into the first cavity 11. Finally, the rear end of the first small diameter cavity 111 can be sealed by the plug. At this time, the pressure regulating elastic element 3, such as the first spring, is pre-compressed, and its pre-tightening force drives the limiting block 23 to abut against the front end of the valve sleeve 7, while the rear end of the valve sleeve 7 is abutted by the plug at the rear end.

[0052] See Figure 1 Optionally, the pressure regulating elastic element 3 is a first spring, one end of which abuts against the inner end of the first large-diameter cavity 112, and the other end of which is sleeved on the valve stem 21 and abuts against the limiting block 23.

[0053] In this embodiment, the first spring is sleeved on the valve stem 21, which not only makes it easy to install it into the first cavity 11, but also prevents the first spring from moving around.

[0054] See Figure 1 Optionally, the valve sleeve 7 is provided with a first through hole 71 and a second through hole 72, the first through hole 71 being connected to the first flow channel 12, and the second through hole 72 being connected to the second flow channel 13.

[0055] In this embodiment, since the valve sleeve 7 is installed in the first small diameter cavity 111, it is necessary to open the first through hole 71 and the second through hole 72 on the valve sleeve 7, so as to communicate with the first flow channel 12 or the second flow channel 13.

[0056] See Figure 1 Optionally, the first flow channel 12 includes a first annular flow channel 121 and a first straight flow channel 122. The first annular flow channel 121 is disposed on the inner wall of the first small diameter cavity 111 and surrounds the first small diameter cavity 111. The two ends of the first straight flow channel 122 are respectively connected to the first annular flow channel 121 and the second cavity 14.

[0057] And / or, the second flow channel 13 includes a second annular flow channel 131 and a second straight flow channel 132. The second annular flow channel 131 is disposed on the inner wall of the first small diameter cavity 111 and surrounds the first small diameter cavity 111. The two ends of the second straight flow channel 132 are respectively connected to the first annular flow channel 121 and the second cavity 14.

[0058] In this embodiment, due to the presence of the first annular flow channel 121, regardless of the rotation angle at which the valve sleeve 7 is inserted into the first small-diameter cavity 111, the first through hole 71 can communicate with the first annular flow channel 121, reducing the difficulty of installing the valve sleeve 7, and the valve sleeve 7 does not need to be fixed to the inner wall of the first small-diameter cavity 111. Similarly, due to the presence of the second annular flow channel 131, regardless of the rotation angle at which the valve sleeve 7 is inserted into the first small-diameter cavity 111, the second through hole 72 can communicate with the second annular flow channel 131, reducing the difficulty of installing the valve sleeve 7, and the valve sleeve 7 does not need to be fixed to the inner wall of the first small-diameter cavity 111. Furthermore, even if the valve sleeve 7 rotates during subsequent use of the pressure regulating valve, the first through hole 71 always communicates with the first annular flow channel 121, and the second through hole 72 always communicates with the second annular flow channel 131.

[0059] See Figure 1 Optionally, the cavity 41 is an annular groove disposed on the circumferential side of the variable piston 4.

[0060] In this embodiment, since the cavity 41 is an annular groove, regardless of the rotation angle of the variable piston 4 when it is installed into the second cavity 14, the transition groove 141 can connect the cavity 41 and the second cavity 14 when the constant pressure variable piston pump stops, reducing the installation difficulty of the variable piston 4. Alternatively, even if the variable piston 4 rotates during the subsequent use of the pressure regulating valve, it will not have an adverse effect.

[0061] Another embodiment of the present invention provides a hydraulic system including a constant pressure variable displacement piston pump and a variable displacement mechanism as described above, wherein the variable displacement piston of the variable displacement mechanism is connected to the swashplate of the constant pressure variable displacement piston pump.

[0062] Since the technical improvements and beneficial effects of the hydraulic system are at least the same as those of the variable mechanism, the hydraulic system will not be described in detail here.

[0063] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" and "second" may explicitly or implicitly include at least one of those features.

[0064] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A variable mechanism, characterized in that, The variable mechanism includes a pressure regulating valve, which includes a valve body (1), a valve core (2), a pressure regulating elastic element (3), a variable piston (4), and a switching structure. The valve body (1) is provided with a first cavity (11), a second cavity (14), a first flow channel (12), and a second flow channel (13). The first end of the first flow channel (12) and the first end of the second flow channel (13) are respectively connected to the first cavity (11), and the second end of the first flow channel (12) and the second end of the second flow channel (13) are respectively connected to the second cavity (14). The valve core (2) is slidably connected to the first cavity (11), the pressure regulating elastic element (3) abuts against the inner end of the first cavity (11) and the valve core (2) respectively, the variable piston (4) is slidably connected to the second cavity (14), one end of the variable piston (4) extends out of the second cavity (14) and is used to connect with the swashplate (5) of the constant pressure variable piston pump; When the constant pressure variable piston pump is in the shutdown state, the variable piston (4) returns to the initial position, the switch structure is used to control the second flow channel (13) to connect or disconnect from the second cavity (14), and the pressure regulating elastic element (3) is used to drive the valve core (2) to cut off the flow in the first flow channel (12); When the variable piston (4) is in the initial position, the first flow channel (12) is blocked and the second flow channel (13) is connected to the second cavity (14). When the constant pressure variable piston pump is started from the large displacement shutdown state, the oil passes over the valve core (2) and acts on the variable piston (4).

2. The variable mechanism according to claim 1, characterized in that, The switching structure includes a transition groove (141) and a cavity (41). The transition groove (141) is located on the inner wall of the second cavity (14) between the second end of the first flow channel (12) and the second end of the second flow channel (13). The cavity (41) is located on the peripheral side of the variable piston (4). When the constant pressure variable piston pump is in the shutdown state, the variable piston (4) returns to the initial position so that the second flow channel (13) is connected to the cavity (41) and the transition groove (141) connects the second cavity (14) to the cavity (41).

3. The variable mechanism according to claim 1, characterized in that, The variable mechanism also includes a return structure (6), which is connected to the swashplate (5). When the constant pressure variable piston pump is in a stopped state, the return structure (6) is used to drive the swashplate (5) to rotate to the initial large displacement position, and drive the variable piston (4) to move to the initial position through the rotation of the swashplate (5).

4. The variable mechanism according to claim 3, characterized in that, The return structure (6) includes a cylinder (61), a return spring (62), and a return piston (63). The return piston (63) is slidably connected to the cylinder (61). One end of the return piston (63) extends out of the cylinder (61) and is connected to the swashplate (5). The other end of the return piston (63) is connected to the inner end of the cylinder (61) through the return spring (62).

5. The variable mechanism according to claim 1, characterized in that, The first cavity (11) includes a first small-diameter cavity (111) and a first large-diameter cavity (112). The inner end of the first small-diameter cavity (111) is connected to the first large-diameter cavity (112). The valve core (2) includes a valve stem (21) and a pressure regulating piston (22). The pressure regulating valve also includes a valve sleeve (7). The valve sleeve (7) is disposed on the inner wall of the first small-diameter cavity (111). The inner diameter of the valve sleeve (7) is the same as the diameter of the pressure regulating piston (22). The pressure regulating piston (22) is fixedly sleeved on the valve stem (21). The pressure regulating piston (22) is slidably connected to the first small-diameter cavity (111). The pressure regulating elastic element (3) abuts against the inner end of the first large-diameter cavity (112) and the valve stem (21).

6. The variable mechanism according to claim 5, characterized in that, The valve core (2) also includes a limiting block (23), which is fixed to the part of the valve stem (21) that extends into the first large-diameter cavity (112). The diameter of the limiting block (23) is greater than the inner diameter of the valve sleeve (7), and the diameter of the limiting block (23) is less than or equal to the inner diameter of the first small-diameter cavity (111). The pressure regulating elastic element (3) abuts against the inner end of the first large-diameter cavity (112) and the limiting block (23).

7. The variable mechanism according to claim 6, characterized in that, The pressure regulating elastic element (3) is a first spring. One end of the first spring abuts against the inner end of the first large-diameter cavity (112), and the other end of the first spring is sleeved on the valve stem (21) and abuts against the limiting block (23).

8. The variable mechanism according to claim 6, characterized in that, The valve sleeve (7) is provided with a first through hole (71) and a second through hole (72). The first through hole (71) is connected to the first flow channel (12), and the second through hole (72) is connected to the second flow channel (13).

9. The variable mechanism according to claim 8, characterized in that, The first flow channel (12) includes a first annular flow channel (121) and a first straight flow channel (122). The first annular flow channel (121) is disposed on the inner wall of the first small diameter cavity (111) and surrounds the first small diameter cavity (111). The two ends of the first straight flow channel (122) are respectively connected to the first annular flow channel (121) and the second cavity (14). And / or, the second flow channel (13) includes a second annular flow channel (131) and a second straight flow channel (132). The second annular flow channel (131) is disposed on the inner wall of the first small diameter cavity (111) and surrounds the first small diameter cavity (111). The two ends of the second straight flow channel (132) are respectively connected to the first annular flow channel (121) and the second cavity (14).

10. A hydraulic system, characterized in that, It includes a constant pressure variable displacement piston pump and a variable displacement mechanism as described in any one of claims 1-9, wherein the variable displacement piston (4) of the variable displacement mechanism is connected to the swashplate (5) of the constant pressure variable displacement piston pump.

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