CN112112753A

CN112112753A - Hydraulic motor

Info

Publication number: CN112112753A
Application number: CN202011071148.6A
Authority: CN
Inventors: 段井胜; 刘秋燕
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-10-09
Filing date: 2020-10-09
Publication date: 2020-12-22

Abstract

The present invention relates to a hydraulic motor, comprising: the variable piston is provided with a first working position and a second working position, when the oil pressure of a P oil port is lower than a preset value n, the variable piston is located at the first working position, and hydraulic oil can drive the first rotor assembly to rotate; when P hydraulic fluid port oil pressure is higher than default m, the variable piston can extrude the variable spring to remove to second operating position, make hydraulic oil can drive the joint subassembly, and then make first rotor and second rotor joint, and can the synchronous drive first rotor rotatory with the second rotor. When the pressure of the oil inlet does not reach the preset value m, the second rotor assembly does not work, no friction exists between the second rotor assembly and the stator, and the service life can be prolonged; the invention has simple and reasonable structure, compact volume and low manufacturing cost.

Description

Hydraulic motor

Technical Field

The invention relates to the technical field of hydraulic motors, in particular to an inner curve radial plunger hydraulic motor.

Background

An inner curve radial plunger type hydraulic motor is a low-speed large-torque hydraulic motor frequently selected in the industries of engineering machinery, mine equipment and the like. Because the hydraulic motor plunger does work repeatedly in each rotation, the working volume of single-circle rotation is larger, and the number of the plungers is larger, so that the working stress state of each plunger can be effectively dispersed, and the hydraulic motor plunger has stronger impact resistance and high pressure resistance.

The inner side surfaces of stators of the existing inner curve radial plunger type hydraulic motors are all wavy curved surfaces, the curved surfaces are formed by connecting a plurality of independent concave arc surfaces end to end, for example, the invention with the Chinese patent number of 201010197277.X, which is named as an invention patent of an 'inner curve multi-action radial plunger type hydraulic motor', the inner side surfaces of the used stators are formed by 8 independent and communicated concave arc surfaces, the displacement of the inner curve radial plunger type hydraulic motor in the prior art is fixed, and if the displacement value after the displacement is changed, the structure of the motor needs to be integrally changed, for example, the structure of an oil distribution shaft and a rotor is changed, so that the oil distribution shaft can input oil with other proportions or the quantity of oil inlet plungers is changed, the structure is complex, the cost is high, and the change of the displacement value is not facilitated according to actual conditions. However, with the development of the mechanical industry, the hydraulic motor is also required to be capable of changing the displacement, so as to meet the functional requirements of low-speed large torque and high-speed small torque.

Disclosure of Invention

In view of the above, there is a need to provide an inner curve radial piston hydraulic motor that can automatically achieve a variable.

The invention discloses a hydraulic motor, which comprises: the stator is cylindrical, and the inner wall of the stator is a wavy curved surface; the first end plate and the second end plate are respectively covered at two ends of the stator; the liquid inlet control valve penetrates through the first end plate and is arranged in the stator, a liquid inlet channel, a backflow channel and a pressure adjusting cavity are arranged in the liquid inlet control valve, the liquid inlet channel and the backflow channel are communicated with the pressure adjusting cavity, the left end of the liquid inlet channel is communicated with the oil port P, and the left end of the backflow channel is communicated with the oil port T; the first rotor assembly comprises a first rotor, a first plunger and a first steel ball, the first rotor is sleeved on the liquid inlet control valve in a rotatable mode, a plurality of first containing cavities are formed in the first rotor in an annular distribution mode, a first plunger is arranged in each first containing cavity in a sliding mode, the first steel ball is arranged in the first plunger and abutted against the inner wall of the stator, a plurality of first through holes are formed in the first rotor and correspond to the first containing cavities one to one, the first through holes are alternately communicated with a liquid inlet channel and a backflow channel to drive the first rotor to rotate, and the right end of the first rotor forms an output shaft and extends out of the second end plate; the second rotor assembly comprises a second rotor, a second plunger and a second steel ball, the second rotor is sleeved on the liquid inlet control valve in a rotatable mode, a plurality of second containing cavities are formed in the second rotor in an annular distribution mode, a second plunger is arranged in each second containing cavity in a sliding mode, the second steel ball is arranged in the second plunger and abutted against the inner wall of the stator, a plurality of second through holes are formed in the second rotor in one-to-one correspondence to the second containing cavities, the second through holes are alternately communicated with a liquid inlet channel and a backflow channel to drive the second rotor to rotate, the second rotor assembly further comprises at least one clamping assembly, and the clamping assembly can be clamped with the first rotor so that the second rotor and the first rotor rotate synchronously; the through flow shaft is arranged at the right end of the pressure adjusting cavity to seal the pressure adjusting cavity, a first flow passage communicated with the oil port P is formed in the through flow shaft, a plurality of second flow passages are distributed on the liquid inlet control valve in an annular shape, the first flow passage is communicated with the second flow passages, and the second flow passages can be communicated with the first through holes; the variable spring is arranged in the pressure adjusting cavity; the variable piston is slidably arranged in the pressure adjusting cavity, the right end of the variable piston is abutted against the variable spring, the variable piston is provided with a first working position and a second working position, when the oil pressure of the oil port P is lower than a preset value n, the variable piston is located at the first working position, and hydraulic oil can drive the first rotor assembly to rotate; when the oil pressure of the P oil port is higher than a preset value m, the variable piston can extrude the variable spring to move to a second working position, so that the hydraulic oil can drive the clamping assembly, the first rotor and the second rotor are clamped and can be synchronously driven to rotate.

In one embodiment, a third flow passage is formed in the variable piston, the third flow passage penetrates through the left end and the right end of the variable piston, when the variable piston is located at the first working position, a first containing cavity is formed between the right end of the variable piston and the left end of the flow shaft, when the variable piston is located at the second working position, a second containing cavity is formed between the left end of the variable piston and the left end of the pressure adjusting cavity, a fourth flow passage and a first ring groove are further formed in the variable piston, the fourth flow passage is communicated with the P oil port and the first ring groove, a plurality of fifth flow passages are annularly distributed on the liquid inlet control valve, the fifth flow passage is communicated with the first ring groove, and the fifth flow passage can be communicated with the second through hole.

In one embodiment, a plurality of tenth flow passages 49 are uniformly formed in the liquid inlet control valve 4 in an annular shape, the tenth flow passages 49 are communicated with the return passage 42, and the tenth flow passages 49 can be communicated with the second through holes 73.

In one embodiment, a sixth flow passage is further formed in the liquid inlet control valve, a second ring groove, a seventh flow passage and a piston cavity are formed in the second rotor, the sixth flow passage is communicated with the piston cavity through the second ring groove and the seventh flow passage, a clamping groove is formed in the second rotor, the clamping assembly is arranged in the piston cavity and comprises a clamping block and a reset spring, the clamping block is slidably arranged in the piston cavity, and the right end of the clamping block abuts against the reset spring.

In one embodiment, a third ring groove is formed in the flow shaft, the backflow channel is communicated with the third ring groove, and the third ring groove is communicated with the plurality of first through holes, so that the plurality of first through holes are all communicated with the backflow channel.

In one embodiment, a sink groove is formed in the right side of the variable piston, the variable spring is arranged in the sink groove, the left end of the variable spring abuts against the variable piston, and the right end of the variable spring abuts against the through flow shaft.

In one embodiment, a second cavity is formed between the sinking groove and the liquid inlet control valve, an eighth flow passage is formed in the liquid inlet control valve, and the second cavity is communicated with the return flow passage through the eighth flow passage.

In one embodiment, the variable piston is provided with a fourth annular groove, and when the variable piston is located at the first working position, the second through hole is communicated with the fourth annular groove.

In one embodiment, 10 first through holes are uniformly distributed on the first rotor in an annular shape, and 10 second through holes are uniformly distributed on the second rotor in an annular shape.

In one embodiment, 6 second flow passages and ninth flow passages are uniformly distributed on the liquid inlet control valve in an annular shape, and the second flow passages and the ninth flow passages are alternately distributed; and 6 fifth flow passages and tenth flow passages are uniformly distributed on the liquid inlet control valve in an annular shape, and the fifth flow passages and the tenth flow passages are alternately distributed.

The invention has the advantages that:

1. when the pressure of an oil inlet is lower than a preset value n, the variable piston controls the second rotor assembly to be disconnected with the clamping assembly of the first rotor assembly, the second rotor assembly is disconnected with the liquid inlet channel, only the first rotor assembly is in a working state, and high-speed output in light load, namely high-speed small torque, can be realized; when the pressure of the oil inlet is greater than a preset value m, the variable piston controls the second rotor assembly to be connected with the output shaft of the first rotor assembly, the oil inlet of the second rotor assembly is communicated, the first rotor assembly and the second rotor assembly are in a working state at the same time, and low speed, namely low-speed and high torque during heavy load can be realized;

2. when the pressure of an oil inlet does not reach the preset value m, the second rotor assembly does not work, no friction exists between the second rotor assembly and the stator, and the service life can be prolonged;

3. the invention has simple and reasonable structure, compact volume and low manufacturing cost.

Drawings

FIG. 1 is a front view of a hydraulic motor provided in accordance with the present invention;

FIG. 2 is a cross-sectional view taken at A-A of FIG. 1 in accordance with the present invention;

FIG. 3 is a cross-sectional view at B-B of FIG. 2 in accordance with the present invention;

fig. 4 is another operating state diagram according to fig. 3 of the present invention.

In the figure, a stator 1, a first end plate 11, a second end plate 12, a first plunger 21, a first steel ball 22, a first accommodating cavity 23, a first rotor 3, a clamping groove 30, a first through hole 31, an output shaft 33, a liquid inlet control valve 4, a liquid inlet channel 41, a return channel 42, a pressure adjusting cavity 43, a second channel 44, a fifth channel 45, a sixth channel 46, an eighth channel 47, a ninth channel 48, a tenth channel 49, a through-flow shaft 5, a first channel 51, a third annular groove 52, a second rotor 6, a second annular groove 61, a seventh channel 62, a piston cavity 63, a second plunger 71, a second steel ball 72, a second through hole 73, a clamping block 741, a return spring 742, a second accommodating cavity 75, a variable piston 8, a third channel 81, a fourth channel 82, a first annular groove 83, a sink groove 84, a variable spring 85, and a fourth annular groove 86.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that when an element is referred to as being "mounted on" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. When an element is referred to as being "secured to" another element, it can be directly secured to the other element or intervening elements may also be present.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "or/and" includes any and all combinations of one or more of the associated listed items.

As shown in fig. 1 to 4, the present invention discloses a hydraulic motor, which includes:

the stator 1 is cylindrical, and the inner wall of the stator 1 is a wavy curved surface;

the first end plate 11 and the second end plate 12 are respectively covered at two ends of the stator 1;

the liquid inlet control valve 4 penetrates through the first end plate 11 and is arranged in the stator 1, a liquid inlet channel 41, a backflow channel 42 and a pressure adjusting cavity 43 are arranged in the liquid inlet control valve 4, the liquid inlet channel and the backflow channel 42 are both communicated with the pressure adjusting cavity 43, the left end of the liquid inlet channel 41 is communicated with a P oil port, the left end of the backflow channel 42 is communicated with a T oil port, and it can be understood that the P oil port is communicated with a high pressure port, and the T oil port is communicated with an oil tank;

the first rotor assembly comprises a first rotor 3, a first plunger 21 and a first steel ball 22, the first rotor 3 is rotatably sleeved on the liquid inlet control valve 4, a plurality of first accommodating cavities 23 are annularly distributed on the first rotor 3, a first plunger 21 is slidably arranged in each first accommodating cavity 23, the first steel ball 22 is arranged in the first plunger 21 and abutted against the inner wall of the stator 1, a plurality of first through holes 31 are formed in the first rotor 3 in one-to-one correspondence with the first accommodating cavities 23, the first through holes 31 are alternately communicated with a liquid inlet channel 41 and a return channel 42 to drive the first rotor 3 to rotate, and an output shaft 33 is formed at the right end of the first rotor 3 and extends out of the second end plate 12;

a second rotor assembly comprising a second rotor 6, a second plunger 71, a second steel ball 72, the second rotor 6 is rotatably sleeved on the liquid inlet control valve 4, a plurality of second accommodating cavities 75 are annularly distributed on the second rotor 6, a second plunger 71 is slidably arranged in each second accommodating cavity 75, the second steel ball 72 is arranged in the second plunger 71, and is abutted against the inner wall of the stator 1, a plurality of second through holes 73 are formed on the second rotor 6 in one-to-one correspondence with the second accommodating cavities 75, the second through holes 73 alternately communicate the liquid inlet channel 41 with the return channel 42 to drive the second rotor 6 to rotate, the second rotor assembly further comprises at least one clamping assembly, and the clamping assembly can be clamped with the first rotor 3, so that the second rotor 6 and the first rotor 3 rotate synchronously;

the flow shaft 5 is arranged at the right end of the pressure adjusting cavity 43 to close the pressure adjusting cavity 43, a first flow passage 51 communicated with the oil port P is formed in the flow shaft 5, a plurality of second flow passages 44 are distributed on the liquid inlet control valve 4 in an annular shape, the first flow passage 51 is communicated with the second flow passages 44, and the second flow passages 44 can be communicated with the first through holes 31;

a variable spring 85 disposed in the pressure adjustment chamber 43;

the variable piston 8 is slidably arranged in the pressure adjusting cavity 43, the right end of the variable piston 8 is abutted to the variable spring 85, the variable piston 8 has a first working position and a second working position, when the oil pressure of the oil port P is lower than a preset value n, the variable piston 8 is located at the first working position, and hydraulic oil can drive the first rotor assembly to rotate; when the oil pressure of the oil port P is higher than a preset value m, the variable piston 8 can extrude the variable spring 85 so as to move to a second working position, the clamping assembly can be driven by hydraulic oil, the first rotor 3 is clamped with the second rotor 6, and the first rotor 3 and the second rotor 6 can be synchronously driven to rotate.

It should be noted that when the oil pressure of the P port is lower than the preset value n, the variable spring 85 can limit the variable piston 8 at the first working position, and when the oil pressure of the P port is higher than m, the variable spring 85 is compressed, so that the variable piston 8 moves to the right side to the second working position.

Preferably, a third flow channel 81 is formed in the variable piston 8, the third flow channel 81 penetrates through the left end and the right end of the variable piston 8, when the variable piston 8 is located at the first working position, a first containing cavity is formed between the right end of the variable piston 8 and the left end of the through flow shaft 5, when the variable piston 8 is located at the second working position, a second containing cavity is formed between the left end of the variable piston 8 and the left end of the pressure adjusting cavity 43, a fourth flow channel 82 and a first annular groove 83 are further formed in the variable piston 8, the fourth flow channel 82 is communicated with the P oil port and the first annular groove 83, a plurality of fifth flow channels 45 are annularly distributed on the liquid inlet control valve 4, the fifth flow channels 45 are communicated with the first annular groove 83, and the fifth flow channel 45 can be communicated with the second through hole 73.

Preferably, a plurality of tenth flow passages 49 are uniformly formed in the liquid inlet control valve 4 in an annular shape, the tenth flow passages 49 are communicated with the return passage 42, and the tenth flow passages 49 can be communicated with the second through holes 73.

Preferably, a sixth flow channel 46 is further formed in the liquid inlet control valve 4, a second annular groove 61, a seventh flow channel 62 and a piston cavity 63 are formed in the second rotor 6, the sixth flow channel 46 is communicated with the piston cavity 63 through the second annular groove 61 and the seventh flow channel 62, a clamping groove 30 is formed in the second rotor 6, the clamping component is disposed in the piston cavity 63 and comprises a clamping block 741 and a return spring 742, the clamping block 741 is slidably disposed in the piston cavity 63, and the right end of the clamping block 741 abuts against the return spring 742.

Preferably, a third ring groove 52 is formed in the flow shaft 5, a plurality of ninth flow passages 48 are uniformly formed in the liquid inlet control valve 4 in an annular shape, the backflow passage 42 is communicated with the third ring groove 52 through the ninth flow passage 48, the third ring groove 52 is communicated with the plurality of first through holes 31, and the plurality of first through holes 31 are communicated with the backflow passage 42.

Preferably, a sinking groove 84 is formed in the right side of the variable piston 8, the variable spring 85 is disposed in the sinking groove 84, the left end of the variable spring 85 abuts against the variable piston 8, and the right end abuts against the flow shaft 5.

Preferably, a second cavity is formed between the sinking groove 84 and the liquid inlet control valve 4, an eighth flow passage 47 is formed in the liquid inlet control valve 4, and the second cavity is communicated with the return passage 42 through the eighth flow passage 47.

Preferably, 10 first through holes 31 are uniformly distributed on the first rotor 3 in an annular shape, and 10 second through holes 73 are uniformly distributed on the second rotor 6 in an annular shape.

Preferably, 6 second flow passages 44 and ninth flow passages 48 are uniformly distributed on the liquid inlet control valve 4 in an annular shape, and the second flow passages 44 and the ninth flow passages 48 are alternately distributed; the liquid inlet control valve 4 is uniformly distributed with 6 fifth flow passages 45 and tenth flow passages 49 in an annular shape, and the fifth flow passages 45 and the tenth flow passages 49 are alternately distributed.

Preferably, the variable piston 8 is provided with a fourth annular groove 86, and when the variable piston 8 is located at the first working position, the second through hole 73 is communicated with the fourth annular groove 86.

The working mode of the invention is as follows: as shown in fig. 3, when the variable piston 8 is located at the first working position, the liquid inlet channel 43 is communicated with a part of the first through holes 31 through the third flow channel 81, the first flow channel 51 and the second flow channel 44, a part of the first through holes 31 are communicated with the return channel 42 through the ninth flow channel 48, the part 21 is pushed to move towards the concave part of the inner wall of the stator 1 through hydraulic pressure, and the driving force generated by all the first steel balls 22 can drive the first rotor 3 to rotate positively, so that the effect of driving the output shaft 33 to rotate is achieved;

as shown in fig. 4, when the variable piston 8 is located at the second working position, the liquid inlet channel 43 is communicated with a part of the second through holes 73 through the third channel 81, the fourth channel 82, the first annular groove 83 and the fifth channel 45, a part of the second through holes 73 is communicated with the return channel 42 through the tenth channel 49, meanwhile, hydraulic oil in the fifth channel 45 is communicated with the piston cavity 63 through the sixth channel 46, the second annular groove 61 and the seventh channel 62, the clamping block 741 is pushed to be clamped into the clamping groove 30, so that the first rotor 3 is clamped with the second rotor 6, the hydraulic oil can synchronously drive the first rotor 3 and the second rotor 6 to rotate, and a larger torque can be output.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A hydraulic motor, said hydraulic motor comprising:

the stator is cylindrical, and the inner wall of the stator is a wavy curved surface;

the first end plate and the second end plate are respectively covered at two ends of the stator;

the liquid inlet control valve penetrates through the first end plate and is arranged in the stator, a liquid inlet channel, a backflow channel and a pressure adjusting cavity are arranged in the liquid inlet control valve, the liquid inlet channel and the backflow channel are communicated with the pressure adjusting cavity, the left end of the liquid inlet channel is communicated with the oil port P, and the left end of the backflow channel is communicated with the oil port T;

the first rotor assembly comprises a first rotor, a first plunger and a first steel ball, the first rotor is sleeved on the liquid inlet control valve in a rotatable mode, a plurality of first containing cavities are formed in the first rotor in an annular distribution mode, a first plunger is arranged in each first containing cavity in a sliding mode, the first steel ball is arranged in the first plunger and abutted against the inner wall of the stator, a plurality of first through holes are formed in the first rotor and correspond to the first containing cavities one to one, the first through holes are alternately communicated with a liquid inlet channel and a backflow channel to drive the first rotor to rotate, and the right end of the first rotor forms an output shaft and extends out of the second end plate;

the second rotor assembly comprises a second rotor, a second plunger and a second steel ball, the second rotor is sleeved on the liquid inlet control valve in a rotatable mode, a plurality of second containing cavities are formed in the second rotor in an annular distribution mode, a second plunger is arranged in each second containing cavity in a sliding mode, the second steel ball is arranged in the second plunger and abutted against the inner wall of the stator, a plurality of second through holes are formed in the second rotor in one-to-one correspondence to the second containing cavities, the second through holes are alternately communicated with a liquid inlet channel and a backflow channel to drive the second rotor to rotate, the second rotor assembly further comprises at least one clamping assembly, and the clamping assembly can be clamped with the first rotor so that the second rotor and the first rotor rotate synchronously;

the through flow shaft is arranged at the right end of the pressure adjusting cavity to seal the pressure adjusting cavity, a first flow passage communicated with the oil port P is formed in the through flow shaft, a plurality of second flow passages are distributed on the liquid inlet control valve in an annular shape, the first flow passage is communicated with the second flow passages, and the second flow passages can be communicated with the first through holes;

the variable spring is arranged in the pressure adjusting cavity;

the variable piston is slidably arranged in the pressure adjusting cavity, the right end of the variable piston is abutted against the variable spring, the variable piston is provided with a first working position and a second working position, when the oil pressure of the oil port P is lower than a preset value n, the variable piston is located at the first working position, and hydraulic oil can drive the first rotor assembly to rotate; when the oil pressure of the P oil port is higher than a preset value m, the variable piston can extrude the variable spring to move to a second working position, so that the hydraulic oil can drive the clamping assembly, the first rotor and the second rotor are clamped and can be synchronously driven to rotate.

2. The hydraulic motor according to claim 1, wherein a third flow channel is formed in the variable piston, the third flow channel extends through left and right ends of the variable piston, when the variable piston is located at the first working position, a first cavity is formed between the right end of the variable piston and the left end of the flow shaft, when the variable piston is located at the second working position, a second cavity is formed between the left end of the variable piston and the left end of the pressure adjustment cavity, a fourth flow channel and a first ring groove are further formed in the variable piston, the fourth flow channel is communicated with the P oil port and the first ring groove, a plurality of fifth flow channels are annularly distributed in the liquid inlet control valve, the fifth flow channel is communicated with the first ring groove, and the fifth flow channel can be communicated with the second through hole.

3. The hydraulic motor according to claim 2, wherein a plurality of tenth flow passages 49 are uniformly formed in the liquid inlet control valve 4 in an annular shape, the tenth flow passages 49 are communicated with the return passage 42, and the tenth flow passages 49 can be communicated with the second through holes 73.

4. The hydraulic motor according to claim 2, wherein a sixth flow passage is further formed in the liquid inlet control valve, a second ring groove, a seventh flow passage and a piston cavity are formed in the second rotor, the sixth flow passage is communicated with the piston cavity through the second ring groove and the seventh flow passage, a clamping groove is formed in the second rotor, the clamping assembly is arranged in the piston cavity and comprises a clamping block and a return spring, the clamping block is slidably arranged in the piston cavity, and the right end of the clamping block abuts against the return spring.

5. The hydraulic motor as claimed in claim 1, wherein a third annular groove is formed in the flow shaft, the return passage communicates with the third annular groove, and the third annular groove communicates with the first through holes, so that the first through holes communicate with the return passage.

6. The hydraulic motor as claimed in claim 1, wherein a sink groove is formed in a right side of the variable piston, the variable spring is disposed in the sink groove, and a left end of the variable spring abuts against the variable piston and a right end of the variable spring abuts against the flow shaft.

7. The hydraulic motor according to claim 6, wherein a second cavity is formed between the sink and the fluid inlet control valve, an eighth flow passage is formed in the fluid inlet control valve, and the second cavity is communicated with the return passage through the eighth flow passage.

8. The hydraulic motor of claim 2, wherein the variable piston defines a fourth annular groove, and wherein the second through hole communicates with the fourth annular groove when the variable piston is in the first operating position.

9. The hydraulic motor of claim 2, wherein the first rotor has 10 first through holes uniformly distributed in a ring shape, and the second rotor has 10 second through holes uniformly distributed in a ring shape.

10. The hydraulic motor of claim 8, wherein 6 second flow passages and ninth flow passages are uniformly distributed on the liquid inlet control valve in an annular shape, and the second flow passages and the ninth flow passages are alternately distributed; and 6 fifth flow passages and tenth flow passages are uniformly distributed on the liquid inlet control valve in an annular shape, and the fifth flow passages and the tenth flow passages are alternately distributed.