Servo variable adjusting plunger hydraulic motor with follow-up mechanism

Abstract

The servo variable adjusting plunger hydraulic motor with the follow-up mechanism comprises a motor shell, a cylinder body, a transmission shaft, a swash plate, a valve plate and a displacement adjusting mechanism, the cylinder body is provided with a plunger and the valve plate, and the servo variable adjusting plunger hydraulic motor is characterized in that a valve element is fixed to the lower end of an adjusting screw rod, and a one-way valve is arranged at the position, close to a piston front cavity, of the motor shell; the cross section area of the piston rear cavity is larger than that of the piston front cavity, a piston oil inlet channel and a piston oil outlet channel are formed in the piston, the piston front cavity is communicated with the valve cavity through the piston oil inlet channel, and the length of the valve element is larger than the distance between a communicating opening of the piston oil inlet channel and the valve cavity and a communicating opening of the piston oil outlet channel and the valve cavity. According to the plunger hydraulic motor, every time the adjusting screw rod moves upwards or downwards by a certain distance, the piston can move upwards or downwards by a corresponding distance under the pushing action of the pressure difference of oil in the piston front cavity and the piston rear cavity so as to increase or reduce the inclination angle of the swash plate by a corresponding amount, and finally the displacement of the plunger hydraulic motor can be adjusted.

Description

Technical Field

[0001] The present invention relates to a plunger hydraulic motor, and more specifically, to a servo variable adjustment plunger hydraulic motor with a follower mechanism. Background Art

[0002] The hydraulic motor is an energy conversion device in the hydraulic system. It is used to drag the external load to do work. It converts the pressure energy of the liquid into mechanical energy in the form of rotation. The axial piston motor refers to the piston arranged axially in the cylinder body and evenly distributed along the circumference, and the piston axis is parallel to the rotation axis of the cylinder body. Due to the high working pressure (up to 350MPa), high speed (up to 3000 rpm) and high volumetric efficiency (up to 98%) of the axial piston motor, and the structural advantages of easy stepless speed change, the axial piston motor has been widely used in the national defense and civil industries, especially in engineering machinery. Generally, when the working pressure of the hydraulic system is greater than 160MPa, the axial piston motor is mostly used.

[0003] In the application process of hydraulic motors, in order to obtain the required torque or speed, the flow of the hydraulic motor needs to be accurately controlled. Under the condition of a certain pressure difference between the inlet and outlet of the hydraulic motor, the torque it outputs is proportional to its displacement, that is, the larger the displacement, the greater the output torque; under the condition of a certain input flow of the hydraulic motor, the speed of the motor is inversely proportional to its displacement, that is, the larger the displacement, the smaller the speed. For the same model of axial piston motors, in order to make it suitable for different torques or non-speed occasions, it is necessary to adjust the displacement of the axial piston motor. The hydraulic motor that can adjust the displacement is a variable hydraulic motor, and the one that cannot adjust the displacement is a fixed hydraulic motor. The displacement adjustment of the existing axial piston hydraulic motor is achieved through a manual variable mechanism. The hand wheel on the manual variable mechanism is turned by hand. The rotating hand wheel drives the piston to move along its axis through the adjusting screw, thereby changing the inclination angle of the swash plate. The change in the inclination angle of the swash plate changes the oil intake and discharge of the piston, and finally changes the displacement of the piston hydraulic motor.

[0004] However, the displacement adjustment method of the existing manual variable mechanism relies on the rigid connection between the adjusting screw and the piston to locate the position of the piston in the piston cavity during the adjustment process, resulting in the piston and the adjusting screw being stressed during the operation of the plunger hydraulic motor, which can easily cause the piston and the adjusting screw to deform or be damaged, shortening the service life of the axial hydraulic motor. In addition, the existing manual variable mechanism does not have a self-locking function and has a low adjustment accuracy, making it difficult to achieve automatic control. Summary of the invention

[0005] In order to overcome the disadvantages of the above technical problems, the present invention provides a servo variable adjustment plunger hydraulic motor with a follower mechanism.

[0006] The servo variable adjustment plunger hydraulic motor with a follower mechanism of the present invention comprises a motor housing, a cylinder body, a transmission shaft, a swash plate, a distribution plate and a displacement adjustment mechanism. The motor housing is provided with an oil inlet and an oil return port. The cylinder body is rotatably arranged in the internal cavity of the motor housing. A plurality of plungers are evenly arranged on the cylinder body. The distribution plate is arranged at the front end of the cylinder body, and the rear end of the plunger is hinged on the swash plate. In the process of the plunger following the rotation of the cylinder body, the opening at the front end of the plunger is selectively connected with the oil inlet or the oil return port through the distribution cavity on the distribution plate. The displacement adjustment mechanism is arranged at the rear of the swash plate, and the displacement adjustment mechanism is composed of a piston, an adjustment screw, an adjustment hand wheel and a large nut. A piston cavity is arranged at the rear of the swash plate, and the piston is arranged in the piston cavity. The large nut is fixed on the motor housing. The adjustment hand wheel is located above the large nut. The upper end of the adjustment screw is fixed on the adjustment hand wheel, and the adjustment screw passes through the large nut in the form of threaded matching. A concave cavity for accommodating the top end of the swash plate is opened on the piston, and the top end of the swash plate is hinged to the piston via a pin shaft. It is characterized in that: A valve cavity is provided in the piston, and a cylindrical valve core inserted into the valve cavity is fixed at the lower end of the adjusting screw; a piston front cavity is formed below the piston, and a piston rear cavity is formed above the piston, and the valve cavity is connected to the piston rear cavity; a one-way valve is provided on the motor housing near the position of the piston front cavity, and a channel connecting the oil inlet with the inlet of the one-way valve is provided on the motor housing, and the outlet of the one-way valve is connected to the piston front cavity; the cross-sectional area of ​​the piston rear cavity is larger than the cross-sectional area of ​​the piston front cavity, and a piston oil inlet channel and a piston oil outlet channel are provided on the piston, the piston front cavity is connected to the valve cavity via the piston oil inlet channel, the piston rear cavity is connected to the piston oil outlet channel and the valve cavity, and the valve cavity is connected to the concave cavity; the length of the valve core satisfies: the length of the valve core is larger than the distance between the connecting port between the piston oil inlet channel and the valve cavity and the connecting port between the piston oil outlet channel and the valve cavity.

[0007] The servo variable adjustment plunger hydraulic motor with a follower mechanism of the present invention has a valve chamber opened on the piston, including an upper valve chamber, a middle valve chamber and a lower valve chamber, all of which are cylindrical in shape. The upper valve chamber is connected with the rear chamber of the piston, the upper valve chamber is connected with the lower valve chamber via the middle valve chamber, and the lower valve chamber is connected with the concave chamber; a sleeve is arranged in the middle valve chamber, and an upper opening and a lower opening are respectively opened at the upper and lower parts of the sleeve, which are connected with the upper end of the piston oil inlet passage and the lower end of the piston oil outlet passage; the valve core is located in the sleeve, the inner diameter of the sleeve is equal to the outer diameter of the valve core, and the length of the valve core is greater than the distance between the upper opening and the lower opening.

[0008] The servo variable adjustment plunger hydraulic motor with a follower mechanism of the present invention has a cover plate fixed to the upper end of the piston, a central through hole for the adjustment screw to pass through is opened in the center of the cover plate, a connecting hole is opened on the cover plate outside the central through hole, and the upper valve cavity is connected with the piston rear cavity through the connecting hole.

[0009] The servo variable adjustment plunger hydraulic motor with a follower mechanism of the present invention comprises a motor housing consisting of a middle housing, a front housing and a rear housing, wherein the front housing and the rear housing are respectively fixed at the front and rear ends of the middle housing, the cylinder body is arranged in the internal cavity of the middle housing, and the interior of the rear housing is a swash plate cavity for accommodating a swash plate; the channel consists of a front channel, a middle channel and a rear channel respectively arranged on the front housing, the middle housing and the rear housing, and the oil inlet is connected to the piston front cavity via the upper front channel, the middle channel, the rear channel and the one-way valve in sequence.

[0010] The servo variable adjustment plunger hydraulic motor with a follower mechanism of the present invention has a rear bearing arranged on the periphery of the cylinder body, the rear bearing is fixed on the inner wall of the middle housing, and a front bearing is arranged on the periphery of the transmission shaft, the front bearing is fixed on the inside of the front housing; the front bearing includes a cylindrical roller bearing and a double-row angular contact ball bearing, and the rear bearing is a cylindrical roller bearing.

[0011] The beneficial effects of the present invention are as follows: the servo variable adjustment plunger hydraulic motor with a follow-up mechanism of the present invention is composed of a motor housing, a cylinder body, a transmission shaft, a swash plate, a plunger, a distribution plate and a displacement adjustment mechanism. The cylinder body and the transmission shaft are rotatably arranged in the motor housing via bearings. The plunger on the cylinder body takes in oil through the oil inlet and discharges oil through the oil return port under the action of the distribution plate to realize the rotational movement of the cylinder body and the transmission shaft; the displacement adjustment mechanism is composed of an adjusting hand wheel, an adjusting screw and a piston. The front cavity of the piston is connected to the oil inlet through a one-way valve and a hole on the motor housing. A piston oil inlet channel and a piston oil outlet channel are provided on the piston. The front cavity of the piston is connected to the piston rear cavity through the piston oil inlet channel and the valve cavity on the piston. The piston rear cavity is connected to the piston oil outlet channel, the valve cavity and the concave cavity accommodating the top end of the swash plate; in this way, when the plunger hydraulic motor is working, During the process, the adjusting screw is driven downward by turning the adjusting handwheel to open the upper end opening of the piston oil inlet. At this time, the high-pressure oil in the front chamber of the piston will enter the front chamber of the piston through the piston oil inlet passage. Since the cross-sectional area of ​​the front chamber of the piston is larger than the area of ​​the rear chamber of the piston, the piston will be driven downward under the action of the pressure difference, thereby driving the top end of the swash plate downward, increasing the inclination angle of the swash plate, and thereby increasing the displacement of the plunger hydraulic motor; correspondingly, when the adjusting screw is driven upward by turning the adjusting handwheel, the hydraulic oil in the rear chamber of the piston will be discharged to the oil return port through the piston oil outlet passage, the valve chamber, and the concave chamber, making the pressure in the front chamber of the piston greater than the pressure in the rear chamber of the piston. Under the action of the pressure difference, the piston is driven upward, thereby driving the top end of the swash plate upward, reducing the inclination angle of the swash plate, and reducing the displacement of the plunger hydraulic motor.

[0012] It can be seen that in the process of adjusting the inclination angle of the swash plate by adjusting the up and down displacement of the screw, every time the adjusting screw moves up or down a certain distance, the piston will move up or down a corresponding distance under the action of the pressure difference between the oil in the front chamber and the rear chamber of the piston, so as to increase or decrease the inclination angle of the swash plate by a corresponding amount. It can be said to have a "servo" effect, and ultimately achieve the adjustment of the displacement of the plunger hydraulic motor.

[0013] Furthermore, since the length of the cylindrical valve core at the lower end of the adjusting screw is greater than the distance between the upper opening of the piston oil inlet channel and the lower opening of the piston oil outlet channel, when the piston moves up or down according to the movement of the adjusting screw, the valve core will block the openings of the piston oil inlet channel and the piston oil outlet channel in the valve cavity. In this way, the hydraulic oil in the front cavity and the rear cavity of the piston is sealed and no longer flows, which can be said to realize the "self-locking" of the displacement adjustment mechanism, ensure that the position of the piston remains unchanged, and ensure the stability of the plunger hydraulic motor during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a front view of the servo variable adjustment plunger hydraulic motor with a follower mechanism of the present invention; Figure 2 A three-dimensional diagram of a servo variable adjustment plunger hydraulic motor with a follower mechanism of the present invention; Figure 3 It is a cross-sectional view of the servo variable adjustment plunger hydraulic motor with a follower mechanism of the present invention; Figure 4 for Figure 3 A partial enlarged view of the mid-displacement adjustment mechanism.

[0015] In the figure: 1 middle housing, 2 front housing, 3 rear housing, 4 cylinder body, 5 transmission shaft, 6 swash plate, 7 plunger, 8 distribution plate, 9 oil inlet, 10 oil return port, 11 swash plate cavity, 12 front bearing, 13 rear bearing, 14 piston, 15 adjusting screw, 16 adjusting hand wheel, 17 large nut, 18 valve core, 19 concave cavity, 20 pin shaft, 21 front channel, 22 middle channel, 23 rear channel, 24 one-way valve, 25 piston front cavity, 26 piston rear cavity, 27 piston oil inlet channel, 28 upper opening, 29 upper valve cavity, 30 connecting hole, 31 piston oil outlet channel, 32 lower opening, 33 sleeve, 34 lower valve cavity, 36 cover plate, 37 middle valve cavity. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0017] like Figure 1 , Figure 2 and Figure 3 As shown, the front view, stereogram and cross-sectional view of the servo variable adjustment plunger hydraulic motor with a follower mechanism of the present invention are respectively given, Figure 4 Given Figure 3 A partial enlarged view of the middle displacement adjustment mechanism, the plunger hydraulic motor shown is composed of a motor housing, a cylinder body 4, a transmission shaft 5, a swash plate 6, a plunger 7, a distribution plate 8 and a displacement adjustment mechanism. The motor housing plays a fixing and supporting role. The motor housing shown is composed of a middle housing 1, a front housing 2 and a rear housing 3. The front housing 2 and the rear housing 3 are respectively fixed on the front and rear sides of the middle housing 1. An oil inlet 9 and an oil return port 10 are provided on the front housing 2. The oil inlet 9 is used to connect to the high-pressure oil circuit, and the oil return port 10 is connected to the low-pressure oil circuit, so that there is a pressure difference between the oil inlet 9 and the oil return port 10 to drive the hydraulic motor to operate. The cylinder body 4 is arranged in the cavity inside the middle shell 1, and a rear bearing 13 is arranged on the periphery of the cylinder body 4, and the rear bearing 13 is fixed on the inner wall of the middle shell 1; the transmission shaft 5 is fixedly connected to the cylinder body 4, and a front bearing 12 is arranged on the periphery of the transmission shaft 5, and the front bearing 12 is fixed on the inner wall of the front shell 2. In this way, by arranging the front bearing 12 and the rear bearing 13, the cylinder body 4 and the transmission shaft 5 can rotate synchronously.

[0018] The distribution plate 8 shown is arranged at the front end of the cylinder body 4, and a plurality of plungers 7 are arranged around the cylinder body 4. The rear end of the plunger 7 is rotatably arranged on the inclined plate 6 via a sliding shoe, and the oil inlet 9 and the oil return port 10 are communicated with the front end of the plunger 7 via the distribution holes on the distribution plate 8. When the plunger 7 rotates to a position communicating with the oil inlet 9, the high-pressure oil in the oil inlet 9 enters the plunger 7, driving the plunger 7 to extend, and the extended plunger 7 pushes the inclined plate 6 to rotate, thereby driving the cylinder body 4 and the transmission shaft 5 to rotate. When the plunger 7 rotates to a position communicating with the oil return port 10, the oil in the plunger 7 is discharged. In the process of the plunger 7 rotating with the cylinder body 4, the plunger 7 cycles and alternates between the oil inlet and oil outlet states, so as to drive the transmission shaft 5 to output mechanical energy to the outside, thereby finally realizing the conversion of the pressure energy of the oil into mechanical energy.

[0019] The interior of the rear housing 3 shown is a swash plate cavity 11, the front part of the swash plate 6 is arranged in the swash plate cavity 11, and the rear end of the plunger 7 is provided with a damping hole communicating with the swash plate cavity 11, and the oil flowing out of the damping hole can realize the lubrication of the sliding shoe. The rear side of the rear housing 3 is provided with a piston cavity, and the piston 14 is arranged in the piston cavity. The piston 14 is provided with a concave cavity 19 for accommodating the top part of the swash plate 6. The top part of the swash plate 6 is hinged in the piston 14 through the pin 20, so that the swash plate 6 can rotate at a corresponding angle. It can be seen that when the angle between the central axis of the swash plate 6 and the horizontal direction increases, the telescopic length of the plunger 7 increases, that is, the displacement increases; when the angle between the central axis of the swash plate 6 and the horizontal direction decreases, the telescopic length of the plunger 7 decreases, that is, the displacement decreases.

[0020] The displacement adjustment mechanism shown is composed of a piston 14, an adjustment screw 15, an adjustment hand wheel 16, a large nut 17 and a valve core 18. The large nut 17 is fixed to the upper end of the rear housing 3. A threaded hole is provided in the center of the large nut 17. The upper end of the adjustment screw 15 passes through the threaded hole in the middle of the large nut 17 in a threaded fit and is fixed to the adjustment hand wheel 16. In this way, the adjustment screw 15 can be driven to rise and fall during the rotation of the adjustment hand wheel 16. A valve cavity is provided in the center of the upper part of the piston 14. A cylindrical valve core 18 is fixed to the lower end of the adjustment screw 15. The valve core 18 is located in the valve cavity. The piston 14 shown has a front piston cavity 25 below it and a rear piston cavity 26 above it. A one-way valve 24 is provided on the rear housing 3 near the front piston cavity 25. A hole is provided on the motor housing. The oil inlet 9 is connected to the front piston cavity 25 via the hole and the one-way valve 24. The one-way valve 24 only allows the oil in the oil inlet 9 to flow into the front piston cavity 25.

[0021] The channels on the motor housing shown in the figure are composed of a front channel 21, a middle channel 22 and a rear channel 23, which are respectively arranged in the front housing 2, the middle housing 1 and the rear housing 3, so that the oil in the oil inlet 9 enters the piston front cavity 25 through the front channel 21, the middle channel 22, the rear channel 23 and the one-way valve 24 in sequence. The piston 14 shown in the figure is provided with a piston oil inlet channel 27 and a piston oil outlet channel 31, and the lower end of the piston oil inlet channel 27 is communicated with the piston front cavity 25.

[0022] The valve chamber on the piston 14 shown includes an upper valve chamber 29, a middle valve chamber 37 and a lower valve chamber 34 which are arranged in sequence from top to bottom. The upper valve chamber 29 is communicated with the piston rear chamber 26, the upper valve chamber 29 is communicated with the lower valve chamber 34 through the middle valve chamber 37, and the lower valve chamber 34 is communicated with the concave chamber 19. A sleeve 33 is arranged in the middle valve chamber 37, and an upper opening 28 which is communicated with the upper opening of the piston oil inlet passage 27 is opened in the upper part of the sleeve 33, and a lower opening 32 which is communicated with the lower opening of the piston oil outlet passage 31 is opened in the lower part of the sleeve 22, and the upper opening 28 is located above the lower opening 32. The valve core 18 is located in the sleeve 22, and the outer diameter of the cylindrical valve core 18 is equal to the inner diameter of the sleeve 22, and the height of the valve core 18 is greater than the distance between the upper opening 28 and the lower opening 32, so that the valve core 18 can simultaneously block the upper opening 28 and the lower opening 32. The upper opening of the oil outlet passage 31 is communicated with the upper valve chamber 29 .

[0023] A cover plate 36 is fixed to the upper end of the piston 14, a central through hole is provided in the center of the cover plate 36 for the adjusting screw 15 to pass through, a connecting hole 30 is provided on the cover plate 36 outside the central through hole, and the upper valve cavity 29 is connected to the piston rear cavity 26 through the connecting hole 30. The cross-sectional area of ​​the piston front cavity 25 is larger than the cross-sectional area of ​​the piston rear cavity 26.

[0024] For ease of description and understanding, the front channel 21, the middle channel 22 and the rear channel 23 are denoted as a, b, c respectively; the piston front chamber 25, the piston oil inlet channel 27, the upper opening 28, the connecting hole 30, the middle valve chamber 37, and the upper valve chamber 29 are denoted as d, e, f, g, h, i respectively; the piston rear chamber 26, the piston oil outlet channel 31, the lower opening 32 and the lower valve chamber 34 are denoted as j, k, l, m respectively.

[0025] The displacement adjustment process and principle of the plunger hydraulic motor of the present invention are as follows: Increase displacement adjustment: Turn the adjusting hand wheel 16 in the manner of driving the adjusting screw 15 to move downward. After the adjusting screw 15 moves downward, the valve core 18 also moves downward with the adjusting screw 15. The downward movement of the valve core 18 will make the upper opening 28 communicate with the middle valve cavity 37. At this time, the oil that enters the piston front cavity 25 through the front channel 21, the middle channel 22, the rear channel 23 and the one-way valve 24 (that is, the oil that enters d through a, b, c, and the one-way valve 37) will pass through the piston front cavity 25, the upper opening 28, The upper part of the middle valve chamber 37, the upper valve chamber 29 and the connecting hole 30 enter the piston rear chamber 26 (i.e., enter k through e, f, g, h, i). Since the cross-sectional area of ​​the piston rear chamber 26 is larger than the cross-sectional area of ​​the piston front chamber 25, the pressure on the upper surface of the piston 14 is larger than the pressure on the lower surface of the piston 14. Under the action of the pressure difference, the piston 14 is driven downward until the piston 14 moves down to the upper end of the valve core 18 and blocks the upper opening 28 again. At this time, the lower opening 32 is also in a blocked state. The downward movement of the piston 14 will drive the top part of the swash plate 6 to move downward, so that the inclination angle of the swash plate 6 (i.e., the angle between the central axis of the swash plate 6 and the horizontal direction) increases, that is, the displacement of the plunger hydraulic motor increases.

[0026] Displacement reduction adjustment: Turn the adjusting screw 15 in the direction that drives the adjusting screw 15 upward. After the adjusting screw 15 moves upward, the lower opening 32 at the lower end of the piston oil outlet passage 31 will communicate with the lower part of the middle valve chamber 37, and at this time, the upper opening 28 is in a sealed state. Since the lower valve chamber 34 is communicated with the concave chamber 19, and the concave chamber 19 is communicated with the slant plate chamber 11, the oil in the piston rear chamber 26 passes through the communicating hole 30, the upper valve chamber 34, the piston oil outlet passage 31, the lower part of the middle valve chamber 37, the lower ... The valve cavity 34 enters the concave cavity 19 (i.e., enters the concave cavity 19 through i, h, k, l, and m), and because the concave cavity 19 is connected to the oil return port 10 through the damping hole on the swash plate cavity 11 and the plunger 7, the oil pressure in the piston rear cavity 26 is lower than the pressure in the piston front cavity 25, that is, the pressure on the lower surface of the piston 14 is higher than the pressure on the upper surface of the piston 14. Under the action of the pressure difference, the piston 14 moves upward until the piston 14 moves upward to the lower end of the valve core 18 and blocks the lower opening 32 again. The upward movement of the piston 14 reduces the inclination angle of the swash plate 6, that is, the displacement of the plunger hydraulic motor is reduced.

[0027] It can be seen that in the process of adjusting the inclination angle of the swash plate 6 by adjusting the up and down displacement of the screw rod 15, each time the screw rod 15 moves up or down a certain distance, the piston 14 will move up or down a corresponding distance under the action of the pressure difference between the oil in the piston front chamber 25 and the piston rear chamber 26, so as to increase or decrease the inclination angle of the swash plate 6 by a corresponding amount, which can be said to have a "servo" effect.

[0028] At the same time, since the plunger 7 will exert a large force on the swash plate 6 during the oil intake and oil discharge process, the hinge position at the rear end of the swash plate 6 is required to have good stability. This is achieved by the valve core 18 simultaneously blocking the upper opening 28 and the lower opening 32 after the adjustment. Since the valve core 18 simultaneously blocks the upper opening 28 and the lower opening 32, the piston front chamber 25 and the piston rear chamber 26 are always filled with oil, and the oil compressibility is very low, which effectively ensures the stability of the hinge fixation of the piston 14 to the rear end of the swash plate 6.

Claims

1. A servo variable adjustment plunger hydraulic motor with a follower mechanism, comprising a motor housing, a cylinder body (4), a transmission shaft (5), a swash plate (6), a distribution plate (8) and a displacement adjustment mechanism, wherein the motor housing is provided with an oil inlet (9) and an oil return port (10), the cylinder body is rotatably arranged in an internal cavity of the motor housing, a plurality of plungers (7) are evenly arranged on the cylinder body, the distribution plate is arranged at the front end of the cylinder body, and the rear end of the plunger is hinged on the swash plate; when the plunger rotates following the cylinder body, the opening at the front end of the plunger is selectively connected to the oil inlet or the oil return port through the distribution cavity on the distribution plate The displacement adjustment mechanism is arranged at the rear of the swash plate, and the displacement adjustment mechanism is composed of a piston (14), an adjustment screw (15), an adjustment hand wheel (16) and a large nut (17). A piston cavity is arranged at the rear of the swash plate, and the piston is arranged in the piston cavity. The large nut is fixed to the motor housing, and the adjustment hand wheel is located above the large nut. The upper end of the adjustment screw is fixed to the adjustment hand wheel, and the adjustment screw passes through the large nut in the form of threaded engagement. A concave cavity (19) for accommodating the top part of the swash plate is opened on the piston, and the top part of the swash plate is hinged to the piston via a pin (20); the characteristics are: The piston (14) is provided with a valve cavity, and a cylindrical valve core (18) inserted into the valve cavity is fixed at the lower end of the adjusting screw; a piston front cavity (25) is formed below the piston, and a piston rear cavity (26) is formed above the piston, and the valve cavity is connected to the piston rear cavity; a one-way valve (24) is provided on the motor housing near the piston front cavity, and a hole is provided on the motor housing to connect the oil inlet (9) with the inlet of the one-way valve, and the outlet of the one-way valve is connected to the piston front cavity; the cross-sectional area of ​​the piston rear cavity is larger than the cross-sectional area of ​​the piston front cavity, and a piston oil inlet channel (27) and a piston oil outlet channel (31) are provided on the piston, the piston front cavity is connected to the valve cavity via the piston oil inlet channel, the piston rear cavity is connected to the valve cavity via the piston oil outlet channel, and the valve cavity is connected to the concave cavity (19); the length of the valve core satisfies that the length of the valve core is larger than the distance between the connecting port between the piston oil inlet channel and the valve cavity and the connecting port between the piston oil outlet channel and the valve cavity.

2. The servo variable adjustment plunger hydraulic motor with a follower mechanism according to claim 1, characterized in that: The valve chamber provided on the piston (14) comprises an upper valve chamber (29), a middle valve chamber (37) and a lower valve chamber (34) all of which are cylindrical in shape. The upper valve chamber is connected to the piston rear chamber (26), the upper valve chamber is connected to the lower valve chamber via the middle valve chamber, and the lower valve chamber is connected to the concave chamber (19). A sleeve is provided in the middle valve chamber, and an upper opening (28) and a lower opening (32) are provided at the upper and lower parts of the sleeve, respectively connected to the upper end of the piston oil inlet passage (27) and the lower end of the piston oil outlet passage (31). The valve core (18) is located in the sleeve, the inner diameter of the sleeve is equal to the outer diameter of the valve core, and the length of the valve core is greater than the distance between the upper opening and the lower opening.

3. The servo variable adjustment plunger hydraulic motor with a follower mechanism according to claim 2, characterized in that: A cover plate (36) is fixed to the upper end of the piston (14), a central through hole through which the adjusting screw (15) passes is provided in the center of the cover plate, a connecting hole (30) is provided on the cover plate outside the central through hole, and the upper valve cavity (29) is connected to the piston rear cavity (26) via the connecting hole (30).

4. The servo variable adjustment plunger hydraulic motor with a follower mechanism according to claim 2, characterized in that: The motor housing is composed of a middle housing (1), a front housing (2) and a rear housing (3); the front housing and the rear housing are respectively fixed to the front and rear ends of the middle housing; the cylinder body (4) is arranged in the internal cavity of the middle housing; the interior of the rear housing is a swash plate cavity (11) for accommodating a swash plate (6); the channel is composed of a front channel (21), a middle channel (22) and a rear channel (23) respectively arranged on the front housing, the middle housing and the rear housing; the oil inlet (9) is connected to the piston front cavity (25) via the upper front channel, the middle channel, the rear channel and the one-way valve (24) in sequence.

5. The servo variable adjustment plunger hydraulic motor with a follower mechanism according to claim 1 or 2, characterized in that: A rear bearing (13) is arranged on the periphery of the cylinder body (4), and the rear bearing is fixed on the inner wall of the middle housing (1); a front bearing (12) is arranged on the periphery of the transmission shaft (5), and the front bearing is fixed on the inside of the front housing (2); the front bearing includes a cylindrical roller bearing and a double-row angular contact ball bearing, and the rear bearing is a cylindrical roller bearing.

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