Piston stroke control mechanism, variable displacement pump and hydraulic directional control valve

Abstract

The present invention relates to a piston stroke control mechanism, comprising a valve body, a piston and a rotating shaft, wherein a piston cavity is provided in the valve body; the piston is disposed in the piston cavity and can move axially; the piston cavity comprises an upper pressure chamber located at the upper end of the piston; a thrust mechanism for driving the piston to move upwards is provided below the piston; the rotating shaft extends into the upper pressure chamber and can rotate around the own axis thereof; the rotating shaft can also move up and down in an axial direction together with the piston; a transition conversion shaft is fixed above the upper pressure chamber, and is provided with an inflow channel and a return channel; the rotating shaft runs through the transition conversion shaft; a chute in communication with the upper pressure chamber is provided on an outer peripheral wall of the rotating shaft; and the rotating shaft can rotate to make the chute communicate with one of the inflow channel and the return channel, or block the chute from both the inflow channel and the return channel. The present invention has the advantages of rational structure, good dynamic response characteristics, convenient control, easy machining, and lower requirements for assembly accuracy.

Description

Piston stroke control mechanism, variable pump and hydraulic directional valve Technical Field

[0001] This invention belongs to the field of fluid transmission and control, and particularly relates to a piston stroke control mechanism. This invention also relates to a variable pump and a hydraulic directional valve using the aforementioned piston stroke control mechanism. Background Technology

[0002] Various valves (such as directional control valves) and variable displacement pumps are widely used in the hydraulic and pneumatic transmission industry. One of the core components of directional control valves and variable displacement pumps is the valve core (also known as piston) stroke control mechanism. For many years, directional control valves have used the thrust generated by energizing an electromagnetic coil to drive the valve core, thereby achieving hydraulic or pneumatic reversal and changing the direction of operation of the hydraulic or pneumatic actuator. Existing electromagnetic directional control valves have the following disadvantages: 1. Electromagnetic valves require continuous electromagnetic force to reverse; the valve core resets when de-energized. However, in some applications, pressure needs to be maintained continuously, requiring the directional control valve to remain in the reversing state. Prolonged energization of the electromagnetic coil generates heat and consumes power, significantly shortening the coil's lifespan. 2. Electromagnetic coils can only drive valve cores with small diameters. Larger diameter valve cores require hydraulic actuation controlled by an electromagnetic valve, known as electro-hydraulic directional control valves. Due to the two-stage switching, the response time of the directional control valve is lengthened. 3. Ordinary electromagnetic valves or electro-hydraulic directional control valves only have open, closed, and reversing states, and cannot control the opening degree, limiting their applicability.

[0003] To this end, the applicant has invented a Chinese invention patent, application number ZL202210611343.6 (publication number CN117189538A), entitled "A Piston Stroke Control Mechanism and a Variable Pump," which discloses such a piston stroke control mechanism. The mechanism includes a valve body and a piston. The valve body has a piston chamber, within which the piston can move axially. The piston chamber includes an upper pressure chamber located at the upper end of the piston. The piston has a pressure oil port and a return oil port. The mechanism also includes a rotating shaft extending into the upper pressure chamber and inserted into the piston. The circumferential wall of the rotating shaft has a groove that is always in communication with the upper pressure chamber. Rotation of the rotating shaft allows the groove to connect with either the pressure oil port or the return oil port, thus causing the piston to move upwards or downwards. When both the pressure oil port and the return oil port are blocked from the groove, the piston stops moving. The mechanism also includes a thrust mechanism that acts on the piston to allow it to move upwards. The thrust mechanism is a lower pressure chamber located at the lower end of the piston, connected to the oil inlet of the valve body. The piston has a connecting channel for connecting the pressure oil port and the lower pressure chamber. The area of ​​the pressure oil in the upper pressure chamber acting on the upper force-bearing surface of the piston is greater than the area of ​​the pressure oil in the lower pressure chamber acting on the lower force-bearing surface of the piston.

[0004] The aforementioned patent has the following drawbacks: machining long, slender connecting channels within the piston is extremely difficult, resulting in low production efficiency and high production costs; the rotating shaft in the aforementioned patent must rotate relative to the piston around its own axis, while the piston must also move relative to the rotating shaft's axis. The rotating shaft, the drive shaft that drives the rotating shaft, the upper pressure chamber, and the piston all require concentric alignment, resulting in significant accumulated tolerances. This makes it difficult to control concentricity during machining. Poor concentricity leads to high frictional losses between the rotating shaft and the piston, increasing friction, shortening lifespan, and introducing additional friction. The piston may cause the rotating shaft to move up and down, affecting product stability and increasing the failure rate. Therefore, the assembly precision requirements between the four components are extremely high, which significantly reduces the product's yield rate. In conclusion, existing piston stroke control mechanisms used in valves and variable pumps require further improvement. Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide a piston stroke control mechanism that has a reasonable structure, good dynamic response characteristics, convenient control, easy processing, and lower assembly precision requirements, in light of the above-mentioned existing technology.

[0006] The technical solution adopted by the present invention to solve the first technical problem mentioned above is as follows: a piston stroke control mechanism, including a valve body, a piston, and a rotating shaft. The valve body has a piston chamber, and the piston is located in the piston chamber and can move axially. The piston chamber includes an upper pressure chamber located at the upper end of the piston. A thrust mechanism is provided below the piston to enable it to move upward. The rotating shaft extends into the upper pressure chamber and can rotate around its own axis. The rotating shaft can also move up and down along the axial direction with the piston. A transition conversion shaft is fixed above the upper pressure chamber. The transition conversion shaft has an inlet channel and a return channel. The rotating shaft passes through the transition conversion shaft. The outer peripheral wall of the rotating shaft has an inclined groove that communicates with the upper pressure chamber. The rotation of the rotating shaft can make the inclined groove communicate with one of the inlet channel and the return channel, or can make the inclined groove block both the inlet channel and the return channel.

[0007] The inclined groove has a certain length and is arranged along the circumference of the rotation axis to form a spiral groove.

[0008] As an improvement, the upper end of the piston is provided with a mounting cavity, and the lower end of the rotating shaft is inserted into and mounted in the mounting cavity. An annular shoulder is provided on the outer peripheral wall of the lower end of the rotating shaft, and a sealing ring is provided between the rotating shaft and the inner peripheral wall of the mounting cavity. The mounting cavity is connected through an oil drain channel on the piston. Because the mounting cavity is connected to the oil drain channel, which is connected to the low-pressure area, it ensures that the area below the rotating shaft and inside the mounting cavity is always under low pressure. This allows the oil pressure to act on the small annular shoulder, applying a force to the rotating shaft that moves towards the piston, thus better ensuring that the rotating shaft can move axially with the piston.

[0009] As a further improvement, ball bearings are provided between the bottom surface of the rotating shaft and the inner bottom surface of the mounting cavity. The ball bearings make the rotating shaft rotate more easily. To ensure the sealing ring is securely installed between the rotating shaft and the inner circumferential wall of the mounting cavity, the sealing ring is held in place by a pressure ring.

[0010] Preferably, the aforementioned rotating shaft is driven to rotate by a drive mechanism. The output shaft of the drive mechanism is connected to the rotating shaft through a transmission joint. The transmission joint and the rotating shaft are connected by a shaft groove structure. The shaft groove structure includes a vertically extending slide groove and a drive shaft that can slide up and down in the slide groove. The slide groove is located in one of the transmission joint and the rotating shaft, and the drive shaft is located in the other of the transmission joint and the rotating shaft.

[0011] More specifically, when the slide groove is provided in the transmission section, the transmission section is shaft-shaped and has an insertion cavity with its opening facing downwards. The peripheral wall of the insertion cavity is provided with a slide groove, and the drive shaft is located at the upper end of the rotating shaft. The upper end of the transmission section is provided with a first slot for the output shaft of the drive mechanism to be inserted. The drive mechanism is preferably a motor, and the rotating shaft is driven by the motor, which facilitates automated control. The rotating shaft can also be driven in other ways.

[0012] Alternatively, the aforementioned thrust mechanism is a spring acting on the lower end of the piston. When the inlet channel is connected to the inclined groove, the force exerted on the piston by the upper pressure chamber is greater than the force exerted on the piston by the spring, causing the piston to move downwards. When the return channel is connected to the inclined groove, the force exerted on the piston by the upper pressure chamber is less than the force exerted on the piston by the spring, causing the piston to move upwards. The upward or downward movement of the piston can block both the inlet and return channels from the inclined groove. Using a spring to provide upward thrust to the piston has the advantages of simple structure and low cost.

[0013] Preferably, the thrust mechanism is a lower pressure chamber located at the lower end of the piston, connected to an oil inlet. The area of ​​the pressure oil in the upper pressure chamber acting on the upper force-bearing surface of the piston is greater than the area of ​​the pressure oil in the lower pressure chamber acting on the lower force-bearing surface of the piston. This thrust mechanism is advantageous for providing oil pressure, and the oil inlet is already present on the valve body, making this design more reasonable. Using oil pressure to provide upward thrust to the piston has the advantage of high precision control, maintaining high control accuracy even after long-term use. The pressure oil in the upper and lower pressure chambers can be supplied by the same pressure oil circuit, and then divided into two lines connected to the upper and lower pressure chambers from outside the piston. Alternatively, they can be supplied by different pressure oil circuits. The key is that when oil is flowing through both the upper and lower pressure chambers, a pressure difference can be formed between them, thereby controlling the piston's upward or downward movement by changing the pressure difference. For example, when the lower and upper pressure chambers are supplied with oil through the same pressure oil circuit, the pressures in the upper and lower pressure chambers are equal. Because the areas of the upper and lower force-bearing surfaces are different, a pressure difference can easily be generated at both ends of the piston, thereby controlling the piston's movement. Using hydraulic pressure to provide upward thrust to the piston has the advantage of high precision control. Even after long-term use, it can maintain high control precision. Moreover, the hydraulic pressure easily achieves equilibrium at both ends of the piston, effectively ensuring that the piston remains in a certain set position within the return channel. During the piston's upward movement due to the pressure difference at both ends, when the pressurized oil no longer enters the upper pressure chamber, and the upper pressure chamber is not connected to the return channel, it neither receives nor leaks oil. The piston has moved to its limit position, and the hydraulic oil in the upper pressure chamber can no longer be compressed. Therefore, the forces on the upper and lower ends of the piston reach equilibrium, keeping the piston in that set position.

[0014] Specifically, based on the area difference of the aforementioned force-bearing surfaces, when the inflow channel is connected to the inclined groove, the pressurized oil enters the upper pressure chamber. The force exerted by the upper pressure chamber on the piston is greater than the force exerted by the lower pressure chamber on the piston, causing the piston to move downward. When the return channel is connected to the inclined groove, the pressurized oil is discharged from the upper pressure chamber, the oil pressure decreases, and the force exerted by the upper pressure chamber on the piston is less than the force exerted by the lower pressure chamber on the piston, causing the piston to move upward. The upward or downward movement of the piston can block both the inflow channel and the return channel from the inclined groove.

[0015] The function of the aforementioned thrust mechanism is to apply an upward thrust to the lower end of the piston, thereby allowing the piston to move upward within the piston chamber. Therefore, the aforementioned thrust mechanism may include elastic mechanisms such as helical springs, pneumatic springs, and torsion springs, as well as permanent magnets, electromagnets, hydraulic cylinders, pneumatic cylinders, etc. Any mechanism that can apply an upward thrust to the lower end of the piston can be used as the thrust mechanism described in this invention.

[0016] Preferably, with the inclined chute blocked from both the inlet and return channels, the inlet and return channels are located on opposite sides of the inclined chute. This allows the rotating shaft to connect the inclined chute to the inlet channel when rotated in one direction, and to connect it to the return channel when rotated in the opposite direction. This facilitates control and allows the drive mechanism to rotate within a small angle range, achieving axial movement of the piston. The circuit controlling the rotation of the drive mechanism is easily digitally controlled. The integrated control circuit of the drive mechanism can control the rotating shaft simply by inputting a signal.

[0017] The fluid flowing in the inflow channel, return channel, upper pressure chamber, and lower pressure chamber can be air, water, hydraulic oil, or other liquids, with hydraulic oil being the best choice.

[0018] Compared with existing technologies, the advantages of this piston stroke control mechanism are:

[0019] 1. By using an additional transition shaft with inlet and return channels, there is no need to machine complex channels inside the piston. The transition shaft is shorter than the piston and is a fixed part, which makes it easier to design and machine channels inside it, thereby greatly improving production efficiency.

[0020] 2. By driving the rotating shaft to rotate, the inclined groove can be connected to either the inlet channel or the return channel, thereby changing the oil pressure in the upper pressure chamber. When the inlet channel is connected to the inclined groove, the oil pressure in the upper pressure chamber increases, which increases the downward force of the pressurized oil on the piston. The force exerted by the upper pressure chamber on the piston is greater than the force exerted by the thrust mechanism on the piston, so the piston can move downward and drive the rotating shaft to move downward. Because it is an inclined groove, as it moves downward along the axis, the opening of the oil port gradually decreases until it stops moving downward. When the return channel is connected to the inclined groove, the oil pressure in the upper pressure chamber decreases, which decreases the downward force of the pressurized oil on the piston. Under the action of the thrust mechanism, the piston can move upward and drive the rotating shaft to move upward. As it moves upward along the axis, the opening of the oil port gradually decreases until it stops moving upward. The larger the rotation angle, the longer the stroke of the axis. The rotation angle determines the stroke. The rotating shaft moves axially with the piston. Because the connection is a point contact, the concentricity requirement between the rotating shaft, the piston, and the upper pressure chamber is greatly reduced. There will also be no axial slippage friction between the rotating shaft and the piston, making assembly simpler, greatly improving the product qualification rate, and providing better mating stability, which greatly reduces the failure rate. The connection between the piston and the rotating shaft can be any connection that can achieve rotational self-alignment.

[0021] 3. This control mechanism only needs to control the rotation of the rotating shaft within a 90-degree or even smaller angle range. The maximum stroke displacement of the piston can be controlled via a servo motor, with the speed and time often completed in milliseconds, exhibiting excellent dynamic response characteristics. Furthermore, the core components of this control mechanism are the rotating shaft and the piston, whose interaction is simple, resulting in low cost and a simple and reasonable structure. The thrust mechanism facilitates the formation of a pressure difference between the upper and lower ends of the piston. After oil is discharged and pressure is released in the upper pressure chamber, the piston can move upward more effectively; when oil is introduced and pressurized in the upper pressure chamber, the piston can move downward more effectively.

[0022] 4. Driving the rotating shaft requires only a small force. A servo motor can easily drive the piston, requiring very little energy even to drive a large-diameter piston, resulting in energy savings. The motor can easily drive the rotating shaft, and a servo motor allows for precise control of the motor's rotation angle. The motor control is responsive; the entire control stroke only requires the motor to rotate 90 degrees or less. An encoder precisely controls the rotation angle, which is then converted into the piston's up-and-down movement position via the rotating shaft. The built-in rotary encoder reads and provides feedback on the current piston position, thereby controlling the piston's stroke and improving the precision of the control mechanism. Of course, other mechanisms can also be used to drive the rotating shaft.

[0023] 5. When the piston moves to the set position, both the inlet and return channels are blocked from the inclined groove, preventing oil from entering or leaving the upper pressure chamber. This balances the forces on both ends of the piston, keeping it in the set position without requiring continuous power. This avoids the need for a constantly energized solenoid coil, as required by traditional solenoid valves. Compared to using a servo valve for high-frequency dynamic piston position adjustment (controlling pressure loss), this method is more energy-efficient.

[0024] 6. The aforementioned intermittent forward or reverse rotation of the rotating shaft is a decomposed action to fully demonstrate the axial movement process and principle of the piston, facilitating a thorough understanding of the invention by those skilled in the art. Of course, in practical applications, based on a pre-designed program and given parameters, the rotation of the rotating shaft can be continuous, and the displacement of the piston can also be continuous. This allows for precise control of the piston's displacement by controlling the angle of rotation of the rotating shaft.

[0025] The second technical problem to be solved by the present invention is to provide a variable pump with a simple and reasonable structure, good dynamic response characteristics, and the ability to accurately control the swing angle of the variable pump head, in light of the above-mentioned existing technology.

[0026] The technical solution adopted by this invention to solve the second technical problem mentioned above is as follows: a variable displacement pump, including a variable displacement head, characterized in that it further includes the aforementioned piston stroke control mechanism, wherein the variable displacement head is oscillatingly connected to the piston, so that the axial movement of the piston drives the variable displacement head to oscillate. The variable displacement head and the piston are oscillatingly connected via a ball joint structure. The ball joint structure allows the axial movement of the piston to more easily drive the variable displacement head to oscillate.

[0027] Compared with existing technologies, the advantages of this variable displacement pump are as follows: This variable displacement pump controls the swing angle of the variable displacement head by controlling the axial movement of the piston. The aforementioned piston stroke control mechanism has excellent dynamic response characteristics, and the piston displacement can be precisely controlled by controlling the rotation angle of the rotating shaft. Therefore, the swing control of this variable displacement pump also has excellent dynamic response characteristics and can precisely control the swing angle of the variable displacement head. Of course, the aforementioned piston stroke control mechanism can be used in other fields or products, such as variable displacement piston pumps, variable displacement gear pumps, variable displacement vane pumps, hydraulic valves, hydraulic cylinders, and hydraulic transformers.

[0028] The third technical problem to be solved by the present invention is to provide a hydraulic directional valve that has a simple and reasonable structure, good dynamic response characteristics, and can accurately control the piston movement, in light of the above-mentioned existing technology.

[0029] The technical solution adopted by this invention to solve the third technical problem mentioned above is: a hydraulic directional valve, characterized in that it includes the aforementioned piston stroke control mechanism, wherein the piston has multiple annular grooves. This allows for precise control of the opening and closing of the piston (traditionally called a valve core) and the oil circuit, as well as the degree of opening. Existing technologies can only control the opening and closing direction, but cannot control the degree of opening. The other structural features of the directional valve are consistent with the existing directional valve structure and principle. Attached Figure Description

[0030] Figure 1 is a three-dimensional structural schematic diagram of an embodiment of the variable pump of the present invention;

[0031] Figure 2 is a three-dimensional structural schematic diagram of an embodiment of the variable pump of the present invention;

[0032] Figure 3 is a cross-sectional view of an embodiment of the variable pump of the present invention, which includes a piston stroke control mechanism (the inclined groove is connected to the return channel);

[0033] Figure 4 is an enlarged view of point A in Figure 3;

[0034] Figure 5 is a sectional view along the BB direction of Figure 3;

[0035] Figure 6 is a cross-sectional view of the variable pump embodiment of the present invention, which includes a piston stroke control mechanism, showing that the inclined groove 51 of the rotating shaft 5 is connected to the inlet and return channels T of the transition shaft 8.

[0036] Figure 7 is a cross-sectional view of an embodiment of the variable pump of the present invention, which includes a piston stroke control mechanism (with the inclined groove 51, inlet channel P, and return channel T all blocked).

[0037] Figure 8 is a cross-sectional view of the variable pump embodiment of the present invention, in which the inclined groove 51 of the rotating shaft 5 is connected to the inlet channel P of the transition shaft 8.

[0038] Figure 9 is a three-dimensional structural diagram of the rotating shaft of the present invention.

[0039] Figure 10 is a three-dimensional structural schematic diagram of the piston of the present invention;

[0040] Figure 11 is a three-dimensional structural diagram of the transition shaft of the present invention;

[0041] Figure 12 is an exploded perspective view of the piston stroke control mechanism of the present invention (with the valve body hidden);

[0042] Figure 13 shows the hydraulic directional valve with piston stroke control mechanism of the present invention;

[0043] Figure 14 is a standalone schematic diagram of the piston stroke control mechanism, which can be extended to various application scenarios. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0045] Figures 1-12 show a preferred embodiment of the variable pump of the present invention using a piston stroke control mechanism.

[0046] A variable displacement pump includes a variable displacement head and a piston stroke control mechanism.

[0047] The piston stroke control mechanism in this embodiment includes a valve body 1, a piston 3, and a rotating shaft 5. The piston 3 is cylindrical, and the valve body 1 has a piston chamber. The piston 3 is positioned in the piston chamber so that it can only move axially up and down and cannot rotate. If a certain section of the cross-section of the piston 3 is a non-circular structure, the cross-section of a section of the piston chamber at the corresponding position is also a non-circular structure, so that the piston 3 can only move up and down. The piston chamber includes an upper pressure chamber 11 located at the upper end of the piston 3. A thrust mechanism is provided below the piston 3, allowing it to move upwards. A rotating shaft 5 extends into the upper pressure chamber 11 and is inserted into the piston 3, capable of rotating around its own axis. The rotating shaft 5 is driven to rotate by a drive mechanism 7, preferably a servo motor. The output shaft of the drive mechanism 7 is connected to the rotating shaft 5 via a transmission joint 9. The transmission joint 9 is shaft-shaped and has an insertion cavity 91 with its opening facing downwards. The upper end of the transmission joint 9 has a slot 911 for the output shaft of the drive mechanism 7 to be inserted into. Symmetrically arranged sliding grooves 912 are provided on the peripheral wall of the insertion cavity 91. A drive shaft 6 is provided at the upper end of the rotating shaft 5, and the drive shaft 6 is located within the sliding grooves 912 and can move. The variable head 2 is oscillatingly connected to the piston 3, so that the axial movement of the piston 3 drives the variable head 2 to oscillate. The variable head 2 and the piston 3 are oscillatingly connected via a ball joint structure. Other parts of the variable pump refer to the existing variable piston pump structure.

[0048] The rotating shaft 5 can also move along the axial direction with the piston 3. The upper end of the piston 3 is provided with a mounting cavity 31. The lower end of the rotating shaft 5 is inserted into and mounted in the mounting cavity 31. A ball bearing 4 is provided between the bottom surface of the rotating shaft 5 and the inner bottom surface of the mounting cavity 31. An annular shoulder 52 is provided on the outer peripheral wall of the lower end of the rotating shaft 5. A sealing ring 10 is provided between the rotating shaft 5 and the inner peripheral wall of the mounting cavity 31. The sealing ring 10 is pressed by a pressure ring 101. The mounting cavity 31 is connected to the oil drain channel 3a on the piston 3. Because the mounting cavity 31 is connected to the oil drain channel 3a, and the oil drain channel 3a is connected to the low-pressure area, it is ensured that the pressure below the rotating shaft and inside the mounting cavity 31 is always low. In this way, the oil pressure can act on the annular shoulder 52 with a very small cross-sectional area, applying a force to the rotating shaft 5 to move in the direction of the piston 3, so as to better ensure that the rotating shaft 5 can move axially with the piston 3.

[0049] A transition shaft 8 is fixed inside the upper pressure chamber 11. The transition shaft 8 is fixed inside the upper pressure chamber 11 by a flange. The transition shaft 8 is provided with an inlet channel P and a return channel T. A rotating shaft 5 passes through the transition shaft 8. The outer peripheral wall of the rotating shaft 5 is provided with a sloping groove 51 that communicates with the upper pressure chamber 11. The sloping groove 51 refers to a groove structure with a certain length that is inclined along the peripheral wall of the rotating shaft 5, thus having a certain spiral shape. There can be one sloping groove 51, but preferably there are two symmetrically arranged sloping grooves 51, forming a similar double spiral structure. The rotation of the rotating shaft 5 can cause the sloping groove 51 to communicate with one of the inlet channel P or the return channel T, thereby causing the piston to move up or down. When both the inlet channel P and the return channel T are blocked from the sloping groove 51, the inlet channel P and the return channel T are located on both sides of the sloping groove 51, and the piston 3 stops moving.

[0050] In this embodiment, the thrust mechanism is a lower pressure chamber 12 located at the lower end of the piston 3, which is connected to the oil inlet 14 of the valve body 1. Rotation of the rotating shaft 5 allows the inclined groove 51 to connect with either the inlet channel P or the return channel T, or it can block the inclined groove 3 from both the inlet channel P and the return channel T. The area of ​​the pressure oil in the upper pressure chamber 11 acting on the upper force-bearing surface 3a of the piston 3 is greater than the area of ​​the pressure oil in the lower pressure chamber 12 acting on the lower force-bearing surface 3b of the piston 3. When the inlet channel P is connected to the inclined groove 51, the force exerted by the upper pressure chamber 11 on the piston 3 is greater than the force exerted by the lower pressure chamber 12 on the piston 3, causing the piston 3 to move downwards. When the return channel T is connected to the inclined groove 51, the force exerted by the upper pressure chamber 11 on the piston 3 is less than the force exerted by the lower pressure chamber 12 on the piston 3, causing the piston 3 to move upwards. The upward or downward movement of the piston 3 can block both the inlet channel P and the return channel T from the inclined groove 51. Thus, neither oil enters nor exits the upper pressure chamber 11, and the upper and lower pressures of the piston are balanced.

[0051] Of course, the thrust mechanism can also be a spring acting on the lower end of the piston 3, preferably placed in the lower pressure chamber 12. When the inlet channel P is connected to the inclined groove 51, the force exerted on the piston 3 by the pressurized oil in the upper pressure chamber 11 is greater than the force exerted on the piston 3 by the spring, causing the piston 3 to move downward; when the return channel T is connected to the inclined groove 51, the force exerted on the piston 3 by the upper pressure chamber 11 is less than the force exerted on the piston 3 by the spring, causing the piston 3 to move upward; the upward or downward movement of the piston 3 can block both the inlet channel P and the return channel T from the inclined groove 51. This embodiment is not shown in the drawings.

[0052] The working principle and process of this piston stroke control mechanism are as follows:

[0053] In this embodiment and other embodiments, the fluid flowing in the valve body is hydraulic oil. When the drive mechanism 7 drives the rotating shaft 5 to rotate in the positive direction by an angle, as shown in Figures 3-6, the inclined groove 51 on the rotating shaft 7 is connected to the return channel T and blocked from the inlet channel P. The pressure oil in the upper pressure chamber 11 is discharged through the return channel T on the transition shaft 8, and the upper pressure chamber 11 is depressurized. The pressure oil in the oil inlet 14 still flows to the lower pressure chamber 12, so the piston 3 moves upward under the action of oil pressure, and the rotating shaft 5 also moves upward. The greater the angle of rotation of the rotating shaft 5 in this direction, the greater the distance the piston 3 moves upward. When the drive mechanism 7 stops working, the rotating shaft 5 moves upward until the inclined groove 3 is blocked from the inlet channel P and the return channel T on the transition shaft 8, as shown in Figure 7. The upper pressure chamber 11 is no longer depressurized, and no more pressure oil continues to enter. The force of the upper pressure chamber 11 acting on the piston 3 is just balanced with the force of the lower pressure chamber 12 acting on the piston 3, and the piston 3 remains in this position.

[0054] Conversely, when the drive mechanism 7 drives the rotating shaft 5 to rotate in the opposite direction by an angle, as shown in Figure 8, the inclined groove 51 on the rotating shaft 7 is connected to the inlet channel P. The pressurized oil from the oil inlet 14 flows down to the lower pressure chamber 12, and simultaneously flows up to the upper pressure chamber 11 after passing through the inclined groove 51. Thus, the pressure in the upper pressure chamber 11 and the lower pressure chamber 12 becomes the same. However, the area of ​​the pressurized oil in the upper pressure chamber 11 acting on the upper force-bearing surface 3a of the piston 3 is greater than the area of ​​the pressurized oil in the lower pressure chamber 12 acting on the lower force-bearing surface 3b of the piston 3. Under the condition of the same pressure, a pressure difference is formed, that is, the piston 3 experiences a downward pressure greater than an upward pressure. The piston 3 moves axially downward, and the oil pressure in the upper pressure chamber 11 also acts on the annular shoulder 52 of the rotating shaft 5, so the rotating shaft 5 also moves downward with the piston 3. The greater the angle of rotation of the rotating shaft 5 in this direction, the greater the distance the piston 3 moves downward. When the drive mechanism 7 stops working, the piston 3 moves down to the inclined groove 51 and the inflow channel P and return channel T on the transition shaft 8 are blocked. The upper pressure chamber 11 will neither have any more pressurized oil entering nor will it depressurize. The force exerted on the piston 3 by the pressurized oil in the upper pressure chamber 11 is just balanced with the force exerted on the piston 3 by the pressurized oil in the lower pressure chamber 12. The piston 3 remains in this position.

[0055] This variable displacement pump achieves its pumping flow rate (i.e., pump displacement) per unit time by changing the swing angle of the variable displacement head 2, which is driven by the axial movement of the piston 3. This is a conventional design for variable displacement pumps.

[0056] The aforementioned intermittent forward or reverse rotation of the rotating shaft 5 is a breakdown of the action to fully demonstrate the up-and-down movement process and principle of the piston 3, facilitating a thorough understanding of the invention by those skilled in the art. Of course, in practical applications, based on a pre-designed program and given parameters, the rotation of the rotating shaft 5 can be continuous, and the displacement of the piston 3 can also be continuous. Therefore, the displacement of the piston 3 can be precisely controlled by the angle of rotation of the rotating shaft 5 via the drive mechanism 7.

[0057] Figure 13 shows a preferred embodiment of the hydraulic directional valve of the present invention, which employs a piston stroke control mechanism.

[0058] A hydraulic directional valve employs a piston stroke control mechanism, comprising a valve body 1, a piston 3, a rotating shaft 5, and a transition shaft 8. The valve body 1 is provided with an oil inlet 1a, a return channel 1b, and multiple oil outlets 1c. Its piston stroke control mechanism is the same as above, and the piston 3 has multiple annular grooves 32.

[0059] The reversing principle of the directional valve is similar to that of a traditional directional valve, and the movement principle of piston 3 is the same as that of the variable pump embodiment.

[0060] Compared to previous solenoid directional valves, which only allowed for on / off switching and couldn't directly control displacement (requiring high-frequency switching, resulting in significant control pressure loss and wastage), the hydraulic directional valve using this piston stroke control mechanism directly converts control into displacement measurement with minimal energy loss, making it more energy-efficient.

[0061] The above two embodiments are examples of specific application scenarios for the piston stroke control mechanism. However, the core lies in the piston stroke control mechanism itself, which is reflected in the above two embodiments, but can exist independently and be extended to other application scenarios, as shown in Figure 14.

[0062] It should be noted that in the description of this embodiment, the terms "front," "rear," "left," "right," "inner," "outer," "upper," and "lower," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are merely for the convenience of describing the 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. Therefore, they should not be construed as limitations on the invention. The terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

Claims

1. A piston stroke control mechanism, comprising a valve body (1), a piston (3), and a rotating shaft (5), wherein the valve body (1) has a piston chamber, the piston (3) is disposed in the piston chamber and is axially movable, the piston chamber includes an upper pressure chamber (11) located at the upper end of the piston (3), a thrust mechanism is provided below the piston (3) to enable it to move upward, and the rotating shaft (5) extends into the upper pressure chamber (11) and is rotatable about its own axis; characterized in that: The rotating shaft (5) can also move up and down along the axial direction with the piston (3). A transition conversion shaft (8) is fixed above the upper pressure chamber (11). The transition conversion shaft (8) is provided with an inlet channel (P) and a return channel (T). The rotating shaft (5) passes through the transition conversion shaft (8). The outer peripheral wall of the rotating shaft (5) is provided with a sloping groove (51) that communicates with the upper pressure chamber (11). The rotation of the rotating shaft (5) can make the sloping groove (51) communicate with one of the inlet channel (P) and the return channel (T), or can make the sloping groove (51) block both the inlet channel (P) and the return channel (T).

2. The piston stroke control mechanism according to claim 1, characterized in that: The upper end of the piston (3) is provided with a mounting cavity (31), the lower end of the rotating shaft (5) is installed in the mounting cavity (31), the lower end of the rotating shaft (5) is provided with an annular shoulder (52) on the outer peripheral wall, a sealing ring (10) is provided between the rotating shaft (5) and the inner peripheral wall of the mounting cavity (31), and the mounting cavity (31) is connected through the oil drain channel (3c) on the piston (3).

3. The piston stroke control mechanism according to claim 2, characterized in that: The sealing ring (10) is pressed by the pressure ring (101); a ball bearing (4) is provided between the bottom surface of the rotating shaft (5) and the bottom surface of the mounting cavity (31).

4. The piston stroke control mechanism according to claim 1, characterized in that: The rotating shaft (5) is driven to rotate by the drive mechanism (7). The output shaft of the drive mechanism (7) is connected to the rotating shaft (5) through the transmission joint (9). The transmission joint (9) and the rotating shaft (5) are connected by a shaft groove structure. The shaft groove structure includes a vertically extending slide groove (912) and a drive shaft (6) that can slide up and down in the slide groove (912). The slide groove (912) is located in one of the transmission joint (9) and the rotating shaft, and the drive shaft (6) is located in the other of the transmission joint (9) and the rotating shaft.

5. The piston stroke control mechanism according to claim 4, characterized in that: When the slide groove (912) is provided on the transmission section (9), the transmission section (9) is axial and has an insertion cavity (91) with the opening end facing downward. The peripheral wall of the insertion cavity (91) is provided with a slide groove (912). The drive shaft (6) is located at the upper end of the rotating shaft (5). The upper end of the transmission section (9) is provided with a slot (911) for the output shaft of the drive mechanism (7) to be inserted.

6. The piston stroke control mechanism according to claim 1, characterized in that: The thrust mechanism is a spring acting on the lower end of the piston (3). When the inflow channel (P) is connected to the inclined groove (51), the force of the upper pressure chamber (11) acting on the piston (3) is greater than the force of the spring acting on the piston (3), and the piston (3) moves downward. When the return channel (T) is connected to the inclined groove (51), the force of the upper pressure chamber (11) acting on the piston (3) is less than the force of the spring acting on the piston (3), and the piston (3) moves upward. The upward or downward movement of the piston (3) can block both the inflow channel (P) and the return channel (T) from the inclined groove (51).

7. The piston stroke control mechanism according to claim 1, characterized in that: The thrust mechanism is a lower pressure chamber (12) located at the lower end of the piston (3), and the lower pressure chamber (12) is connected to the inlet (14) of the valve body (1); the area of ​​the upper force-bearing surface (3a) of the piston (3) in the upper pressure chamber (11) is greater than the area of ​​the lower force-bearing surface (3b) of the piston (3) in the lower pressure chamber (12).

8. The piston stroke control mechanism according to claim 8, characterized in that: When the inflow channel (P) is connected to the inclined groove (51), the force exerted by the upper pressure chamber (11) on the piston (3) is greater than the force exerted by the lower pressure chamber (12) on the piston (3), and the piston (3) moves downward; when the return channel (T) is connected to the inclined groove (51), the force exerted by the upper pressure chamber (11) on the piston (3) is less than the force exerted by the lower pressure chamber (12) on the piston (3), and the piston (3) moves upward; The upward or downward movement of the piston (3) can block both the inflow channel (P) and the return channel (T) from the inclined groove (51).

9. A variable pump, comprising a variable head (2), characterized in that: It also includes a piston stroke control mechanism as described in any one of claims 1 to 8, wherein the variable head (2) is oscillatingly connected to the piston (3), such that the axial movement of the piston (3) drives the variable head (2) to oscillate.

10. A hydraulic directional valve, characterized in that: The piston stroke control mechanism as described in any one of claims 1 to 8 is provided, wherein the piston (3) has a plurality of annular grooves (32).

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