Axial piston variable displacement pump

Abstract

The application discloses an axial plunger variable pump and relates to hydraulic transmission technology. The axial plunger variable pump comprises a main pump body, a flow control valve and a power control valve. The main pump body is provided with a shell, a swash plate and a rear cover. The swash plate is provided with two groups of piston assemblies, i.e. a reset piston assembly and a variable piston assembly. A sliding bearing is arranged between a swash plate runway and a shell support runway. Four groups of friction pairs, i.e. a reset piston and a support sliding shoe one, a variable piston and a support sliding shoe two and a swash plate high-pressure runway and a corresponding sliding bearing, are respectively connected to an oil chamber and a crescent-shaped floating support groove, and pressure oil is introduced into the four groups of friction pairs to form a hydraulic oil film, so that dry friction of metal is converted into fluid friction, and oil circulation realizes self-cooling and wear reduction. A guide inclined surface and a variable cross-section communication groove are arranged at a ball head end of a support piston one, and a full-swing-angle oil path is continuously connected. The axial plunger variable pump has small wear, good heat dissipation, stable and precise control, energy saving and protection of an original driving machine overload, and is suitable for high-pressure working conditions such as engineering machinery and ocean engineering.

Description

Technical Field

[0001] This invention relates to the field of hydraulic transmission technology, and more specifically, to an axial piston variable displacement pump. Background Technology

[0002] Swashplate axial piston variable pumps are core power components of high-end hydraulic systems and are widely used in fields such as engineering machinery, metallurgical equipment, and marine engineering vessels. The performance of its swashplate variable support mechanism and variable control system directly determines the service life, operational reliability, working condition adaptability, and control accuracy of the piston pump.

[0003] Regarding the swashplate variable displacement support structure, existing axial piston pumps typically use sliding bearings to connect the high and low pressure sides of the swashplate to the support tracks within the housing. The return piston, variable piston, and corresponding support shoes directly abut against each other via their metal end faces. All four key friction pairs are in a state of hard metal-to-metal contact dry friction. Under high pressure and frequent reciprocating variable displacement conditions, the alternating fluid pressure and spring load act directly on the metal contact surfaces, resulting in severe friction and wear. This easily leads to abrasive wear, surface scoring, and other failures, which are major factors limiting the overall lifespan of the piston pump. Simultaneously, the large amount of frictional heat continuously generated by dry friction lacks an effective heat dissipation path, relying solely on natural heat dissipation through the oil within the housing. Under high pressure conditions, rapid local heat accumulation easily causes oil carbonization, metal surface adhesion, and sliding bearing seizure, leading to variable displacement mechanism jamming and failure. Furthermore, the high coefficient of friction in dry friction dynamically changes with wear, increasing the driving force loss of the swashplate oscillation and causing lag in swashplate angle adjustment and decreased control linearity, making it difficult to meet the requirements of high-precision variable displacement control. Currently, the industry mostly improves wear performance by using wear-resistant coatings and friction-reducing alloy materials. However, such solutions cannot fundamentally eliminate metal-to-metal dry friction, nor can they simultaneously solve the problem of insufficient heat dissipation. They also have limitations such as high cost, limited lifespan improvement, and lack of self-cooling buffering capabilities.

[0004] Based on the above problems, this invention applies for an axial piston variable pump that can simultaneously achieve friction reduction and self-cooling of the entire friction pair, and has stable operating conditions and long service life. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an axial piston variable pump that can form a stable hydraulic oil film between multiple key friction pairs, transforming dry metal friction into fluid friction, and simultaneously achieving friction reduction and self-cooling.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an axial piston variable displacement pump, comprising a main pump body, a flow control valve, and a power control valve. The main pump body includes a housing, a swashplate located within the housing, and a rear cover fixedly and sealed to one end of the housing. The swashplate is provided with opposing piston drive assemblies, including a reset-side piston assembly and a variable displacement control-side piston assembly. A high-pressure side swashplate track and a low-pressure side swashplate track are respectively provided on the front and rear sides of the swashplate. A semi-circular support track is provided on the inner wall of the housing corresponding to the high-pressure side swashplate track, and a semi-circular support track is provided corresponding to the low-pressure side swashplate track. Support track two, a sliding bearing one is provided between the high-pressure side inclined plate track and the semi-circular support track one, and a sliding bearing two is provided between the low-pressure side inclined plate track and the semi-circular support track two. The reset side piston assembly includes a reset rod fixed on the rear cover. The reset rod extends axially along the housing. A reset piston is coaxially sleeved on the outer periphery of its end. The reset piston and the reset rod slide in axial direction. A support slip shoe one is provided at the tail end of the reset piston. The support slip shoe one is assembled with the inclined plate through a support plunger one. A buffer friction area one is formed between the reset piston and the support slip shoe one. The rear cover has a high-pressure oil inlet channel that extends into the reset rod. The reset piston has an axially extending high-pressure oil channel that is connected to the high-pressure oil inlet channel. The support slipper has an oil chamber that is connected to the high-pressure oil channel inside the reset piston. The oil in the oil chamber generates a hydraulic oil film between the reset piston and the support slipper, forming the buffer friction zone. The variable control side piston assembly includes a control rod fixed to the rear cover. The control rod extends axially along the housing, and a variable piston is coaxially sleeved on the outer periphery of its end. The tail end of the variable piston is provided with a second support slipper. The second support slipper is assembled with the swashplate via a second support plunger. A second buffer friction zone is formed between the variable piston and the second support slipper. The second support slipper is provided with an oil chamber at one end corresponding to the variable piston. The second support plunger is provided with a low-pressure oil channel, which is connected to the inner cavity of the housing. Through the oil in the second oil chamber, a hydraulic oil film is generated between the variable piston and the second support slipper, forming the second buffer friction zone. The support plunger is provided with a high-pressure oil channel 2 that is connected to the oil chamber 1. A high-pressure oil channel 3 is provided on the swashplate. One end of the high-pressure oil channel 3 is connected to the high-pressure oil channel 2, and the other end extends into the high-pressure side swashplate track. A crescent-shaped floating support groove 1 is provided in the high-pressure side swashplate track. The oil passes through the crescent-shaped floating support groove 1, so that a hydraulic oil film is generated between the high-pressure side swashplate track and the sliding bearing 1, forming a buffer friction zone 3. A high-pressure oil channel four is also provided on the swashplate. One end of the high-pressure oil channel four is connected to the high-pressure oil channel two, and the other end extends into the low-pressure side swashplate track. A crescent-shaped floating support groove two is provided in the low-pressure side swashplate track. The oil passes through the crescent-shaped floating support groove two, so that a hydraulic oil film is generated between the low-pressure side swashplate track and the sliding bearing two, forming a buffer friction zone four.

[0007] Furthermore, the present invention includes a ball-head assembly end on the first supporting plunger, and an assembly groove adapted to the ball-head assembly end is opened at the end of the first supporting slipper away from the first oil chamber. The ball-head assembly end is hinged in the assembly groove and can rotate relative to it. The second high-pressure oil channel extends to the ball-head assembly end, and the channel opening corresponds to the inner wall of the assembly groove. A connecting groove is provided between the first oil chamber and the assembly groove. The cross-sectional area of ​​the opening of the connecting groove at the end connecting the first oil chamber is smaller than the cross-sectional area of ​​the opening of the connecting groove at the end connecting the assembly groove.

[0008] Furthermore, in this invention, the second high-pressure oil channel is located at the opening of the ball head assembly end, and guide slopes are provided on both sides of the ball head swing direction. Within the full angular range of rotation of the ball head assembly end in the assembly groove, the opening of the second high-pressure oil channel is always in fluid communication with the inlet of the connecting groove through the guide slopes.

[0009] In a further embodiment of the present invention, the flow control valve includes a flow control valve body, a flow control valve core slidably mounted in the flow control valve body, and a flow regulating spring assembly disposed at one end of the valve core; the flow control valve body is provided with a high-pressure oil passage five communicating with the oil outlet of the main pump body, a control oil passage one communicating with the variable piston chamber, a return oil passage communicating with the oil drain chamber of the main pump body housing, and a feedback oil passage one for connecting to the load feedback pressure.

[0010] Furthermore, the outer wall of the flow control valve core is provided with a damping groove, which cooperates with the valve core hole of the flow control valve body to form damping B and damping C; damping E is provided in the return oil channel, and damping E and damping B are arranged in series; the flow control valve body is also provided with a second control oil passage, and damping D is provided in the second control oil passage; the flow control valve core is also provided with a variable damping, and damping D and variable damping cooperate to form a C-type hydraulic half-bridge; a flushing center hole is provided at the axial center of the flow control valve core, and the flushing center hole is connected with damping C to form a self-flushing circuit.

[0011] In a further embodiment of the present invention, the flow regulating spring assembly includes a flow spring seat, a large flow control spring, a small flow control spring, a flow regulating rod, and a flow regulating rod sleeve; the large flow control spring and the small flow control spring are coaxially nested, with their two ends respectively abutting against the base end faces of the flow spring seat and the flow regulating rod; the flow regulating rod sleeve is threadedly connected to the flow control valve body, and the flow regulating rod passes through the flow regulating rod sleeve and is axially locked by a nut.

[0012] Furthermore, the annular groove of the flow regulating rod is provided with an O-ring and a retaining ring for sealing the load feedback control oil.

[0013] In a further embodiment of the present invention, the power control valve includes a power control valve body, a power control valve sleeve slidably mounted within the power control valve body, a power control valve core, and a power adjusting spring assembly located at one end of the power control valve sleeve; a feedback lever is fixedly connected to the swashplate, and the feedback lever is embedded in the slot of the power control valve sleeve to form a mechanical linkage; the power control valve core has a control cavity, the control cavity is connected to a second feedback oil passage, and is connected to a first feedback oil passage via the second feedback oil passage, the first feedback oil passage being provided with damping A; the oil drain passage of the power control valve is connected to the oil drain chamber of the main pump housing.

[0014] Further, the present invention includes a power spring seat, a large power spring, a small power spring, a power adjusting rod, and a power adjusting rod sleeve; the large power spring and the small power spring are coaxially nested, with one end of each abutting against the power spring seat; the other end of the large power spring abuts against the end face of the power adjusting rod sleeve, and the other end of the small power spring abuts against the end face of the power adjusting rod; the power adjusting rod sleeve is threaded to the power control valve body, and the power adjusting rod passes through the power adjusting rod sleeve and is axially locked by a nut.

[0015] By adopting the above technical solution, the following technical effects are achieved: 1. Fluid lubrication of all friction pairs significantly reduces wear and extends the overall service life. In this invention, pressure oil is introduced through corresponding oil chambers or crescent-shaped floating support grooves at four key friction pairs: the reset piston and support shoe one, the variable piston and support shoe two, the high-pressure side swashplate track and sliding bearing one, and the low-pressure side swashplate track and sliding bearing two, forming a stable hydraulic oil film. This transforms traditional dry metal friction into fluid friction, avoiding direct contact between metal surfaces, significantly reducing the friction coefficient and wear rate, and effectively extending the service life of the friction pairs and the entire piston pump.

[0016] 2. Self-cooling circulating oil suppresses the risk of high-temperature failure. High-pressure oil continuously circulates along the internal oil passage between the oil chamber, floating support groove and main oil passage, which can promptly remove the frictional heat generated by the friction pair, avoid failures such as oil carbonization, metal surface adhesion and sliding bearing seizure caused by localized excessive oil temperature, and greatly improve the operational reliability under high-pressure and frequent variable operating conditions.

[0017] 3. Constant flow and constant power combined control, balancing energy saving and overload protection under all operating conditions. This invention integrates a flow control valve and a power control valve to achieve dual-mode adaptive switching: Under medium and low pressure conditions, the flow control valve adjusts the pump displacement based on load feedback pressure to maintain a constant throttling pressure difference, achieving on-demand flow supply, significantly reducing overflow and throttling energy losses, and improving system energy efficiency; when the system pressure rises to the set power threshold, the power control valve automatically intervenes, driving the swashplate to reduce the swing angle, so that the output flow decreases with the increase in pressure, keeping the pump output power approximately constant, which fully utilizes the rated power of the prime mover and avoids overload shutdown of the prime mover under heavy load conditions, making it more adaptable to different operating conditions.

[0018] 4. Multi-stage damping and optimized hydraulic half-bridge design significantly improves control stability and adjustment accuracy. This invention incorporates a multi-stage damping and hydraulic half-bridge structure in the control oil circuit: Damper A in the feedback oil passage filters out high-frequency fluctuations in the load feedback pressure signal, smoothing the control input; Damper E and Damper B in the return oil passage are connected in series, increasing the valve core movement damping, suppressing valve core vibration caused by pressure shocks, and ensuring stable flow output; Damper D, in conjunction with the variable damper, forms a C-type hydraulic half-bridge, smoothly controlling the pressure gain characteristics, achieving precise and smooth adjustment of the variable piston chamber pressure, and effectively reducing hydraulic shock and mechanical vibration during variable flow processes. Simultaneously, the self-flushing circuit of the flow valve core removes impurities from the valve core gap, preventing valve core jamming and improving operational reliability.

[0019] 5. Mechanical negative feedback constant power regulation offers rapid response and high control precision. This invention utilizes a feedback lever fixed on the swashplate and embedded in the power control valve sleeve groove to form a mechanically linked closed-loop negative feedback structure between the swashplate angle and the valve sleeve displacement. When system pressure changes drive changes in the swashplate angle, the feedback lever moves synchronously with the swashplate and drives the power control valve sleeve to displace in the same direction, quickly adjusting the valve opening and re-establishing force balance. This effectively suppresses flow regulation overshoot, resulting in a more accurate constant power characteristic curve and smoother regulation transition.

[0020] 6. The oil circuit layout is compact, and the oil flow at the hinge is stable and reliable. High-pressure oil is introduced into the swashplate track step by step through the internal channels of the reset rod, reset piston, and support plunger, while low-pressure oil returns directly through the inner cavity of the housing. There is no need to add complex external pipelines, resulting in a compact overall structure with strong adaptability. At the same time, the guide slope design at the opening of the ball head assembly end, combined with the variable cross-section connecting groove, can not only throttle and stabilize the pressure and smooth oil pressure fluctuations, but also compensate for the opening misalignment when the ball head swings, ensuring continuous and uninterrupted oil flow throughout the entire swing angle range and ensuring stable oil film pressure at each friction pair. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of an axial piston variable pump. Figure 2 Cross-sectional view of the swashplate, reset-side piston assembly, variable control-side piston assembly, and rear cover; Figure 3 for Figure 1 Enlarged view of point a in the middle; Figure 4 for Figure 1 Enlarged view at point b in the middle; Figure 5 A schematic diagram of the swashplate, reset-side piston assembly, and variable control-side piston assembly; Figure 6 Exploded view of the swashplate, reset-side piston assembly, and variable control-side piston assembly; Figure 7 This is a partial sectional view of the swashplate. Figure 8 This is a schematic diagram of the shell structure; Figure 9 Overall cross-section of the axial piston variable pump Figure 1 ; Figure 10 Overall cross-section of the axial piston variable pump Figure 2 ; Figure 11 This is a cross-sectional view of the flow control valve structure. Figure 12 This is a partial sectional view of a flow control valve; Figure 13 This is a longitudinal sectional view of the flow control valve structure. Figure 14 This is a cross-sectional view of a power control valve. Figure 15 This is a longitudinal sectional view of the power control valve; Figure 16 A schematic diagram of the main pump body and power control valve; Figure 17 Overall cross-section of the axial piston variable pump Figure 3 .

[0022] 1. Shell; 10. Semicircular support track one; 11. Semicircular support track two; 2. Rear cover; 3. Inclined plate; 30. High-pressure side swashplate track; 31. Low-pressure side swashplate track; 32. Sliding bearing one; 33. Sliding bearing two; 34. Reset rod; 340. Reset spring; 35. Reset piston; 36. Support shoe one; 37. Support plunger one; 38. Buffer friction zone one; 39. High-pressure oil channel one; 40. Oil chamber one; 41. High-pressure oil channel two; 42. Control rod; 43. Variable piston; 44. Support. 45. Slipper II, 46. Supporting plunger II, 47. Buffer friction zone II, 48. Oil chamber II, 49. Low-pressure oil channel, 50. High-pressure oil channel III, 51. Crescent-shaped floating support groove I, 52. Buffer friction zone III, 53. High-pressure oil channel IV, 54. Crescent-shaped floating support groove II, 55. Buffer friction zone IV, 56. Ball head assembly end, 57. Assembly groove, 58. Connecting groove, 59. Guide slope, 50. Feedback lever; 6. Flow control valve body; 60. Flow control valve core; 62. High-pressure oil channel five; 63. Control oil channel one; 64. Return oil channel; 65. Feedback oil channel one; 66. Damping B; 67. Damping C; 68. Damping E; 69. Control oil channel two; 70. Damping D; 71. Variable damping; 72. Flushing center hole; 73. Flow spring seat; 74. Large flow control spring; 75. Small flow control spring; 76. Flow regulating rod; 77. Flow regulating rod sleeve; 78. Nut one; 79. O-ring; 80. Retaining ring. 9. Power control valve body; 90. Power control valve sleeve; 91. Power control valve core; 93. Slot; 95. Feedback oil passage two; 96. Damping A; 97. Oil drain passage; 98. Power spring seat; 99. Power adjustment large spring; 100. Power adjustment small spring; 101. Power adjustment rod; 102. Power adjustment rod sleeve; 103. Nut two. Detailed Implementation

[0023] Reference Figures 1 to 17 The embodiments of the present invention will be further described below.

[0024] The axial piston variable pump disclosed in this embodiment is mainly composed of three parts: a main pump body, a flow control valve, and a power control valve. It has the functions of floating friction reduction and self-cooling, as well as constant flow and constant power composite control.

[0025] I. Overall Structure of Main Pump Body The main pump body includes a housing 1. One end of the housing 1 is fixed and sealed with a rear cover 2 by bolts. Inside the housing 1, there is a swashplate 3 that can swing around a swing axis. The front and rear sides of the swashplate 3 are integrally formed with a high-pressure side swashplate track 30 and a low-pressure side swashplate track 31, respectively. A semi-circular support track 10 is provided on the inner wall of the housing 1 at the position corresponding to the high-pressure side swashplate track 30, and a semi-circular support track 21 is provided at the position corresponding to the low-pressure side swashplate track 31. A sliding bearing 32 is embedded between the high-pressure side swashplate track 30 and the semi-circular support track 10, and a sliding bearing 33 is embedded between the low-pressure side swashplate track 31 and the semi-circular support track 21. The inner ring of the sliding bearing is in contact with the swashplate track, and the outer ring is in contact with the housing support track, so that the swashplate 3 can swing freely along the arc surface of the track, realizing the displacement adjustment of the plunger pump.

[0026] The upper and lower ends of the swashplate 3 are provided with opposing piston drive assemblies, including a reset-side piston assembly and a variable control-side piston assembly, which work together to drive the swashplate 3 to change the swing angle.

[0027] II. Reset-side piston assembly and buffer friction area The reset side piston assembly includes a reset rod 34, one end of which is fixedly mounted on the rear cover 2, and the entire assembly extends horizontally along the axial direction of the housing 1. A reset piston 35 is coaxially sleeved on the outer periphery of the end of the reset rod 34, and the reset piston 35 and the reset rod 34 slide in axial direction. A reset spring 340 is also sleeved between the reset rod 34 and the reset piston 35, and the two ends of the reset spring 340 abut against the stepped surface of the reset rod 34 and the inner end surface of the reset piston 35, respectively, providing a preload force to move the reset piston 35 in the direction of the swashplate 3.

[0028] A support slipper 36 is provided at the tail end of the swashplate 3 facing the reset piston 3. The support slipper 36 and the swashplate 3 are connected by a support plunger 37. Specifically, one end of the support plunger 37 is fixedly embedded inside the swashplate 3, and the other end is provided with a ball head assembly end 55. The end of the support slipper 36 opposite to the reset piston 35 has a recessed spherical assembly groove 56. The contour of the assembly groove 56 is adapted to the outer contour of the ball head assembly end 55. The ball head assembly end 55 is hinged in the assembly groove 56 and can swing relative to the center of the ball. This hinged structure ensures that no matter what angle the swashplate 3 is at, the axial thrust of the reset piston 35 can be smoothly transmitted to the swashplate 3 through the support plunger and slipper assembly.

[0029] A buffer friction zone 38 is formed between the end faces of the reset piston 35 and the supporting slipper 36. A high-pressure oil inlet channel is provided inside the rear cover 2, extending into the interior of the reset rod 34. A high-pressure oil channel 39 extending axially is provided inside the reset piston 35, with the inlet end of the high-pressure oil channel 39 always in communication with the high-pressure oil inlet channel. An oil chamber 40 is recessed on the end face of the supporting slipper 36 facing the reset piston 35, with the opening of the oil chamber 40 positioned opposite the outlet end of the high-pressure oil channel 39.

[0030] During operation, external high-pressure oil enters the oil chamber 40 through the high-pressure oil inlet of the rear cover 2 and the high-pressure oil channel 39 inside the reset piston 35. After filling the oil chamber, a high-pressure hydraulic oil film is formed between the contact surfaces of the reset piston 35 and the support slipper 36, separating the two metal surfaces and converting the original dry friction into fluid friction, thereby achieving friction reduction of the floating support.

[0031] The supporting plunger 37 has a high-pressure oil channel 41 inside, one end of which extends to the end face of the ball head assembly end 55, forming a circular channel opening. The supporting slipper 36 has a connecting groove 57 inside, with its two ends connecting the oil chamber 40 and the assembly groove 56 respectively, allowing fluid communication between the high-pressure oil channel 41 and the oil chamber 40. The end of the connecting groove 57 connecting to the oil chamber 40 has a smaller cross-sectional area, while the end connecting to the assembly groove 56 has a larger cross-sectional area, forming a variable cross-section flow structure. The smaller end can act as a throttling and pressure-stabilizing agent, smoothing oil pressure fluctuations, while the larger end can be adapted to the opening size of the ball head end face, ensuring flow capacity.

[0032] High-pressure oil channel 2 41 is located at the opening of the ball head assembly end 55. Both sides of the ball head's swing direction are machined with guide slopes 58, which smoothly transition from the opening edge to the spherical surface of the ball head. When the swashplate 3 swings, causing the support plunger 37 to swing, the ball head assembly end 55 rotates relative to the assembly groove 56, causing a certain misalignment of the opening. Through the transition compensation of the guide slopes 58 on both sides, the opening of high-pressure oil channel 2 41 always maintains overlap with the inlet of the connecting groove 57 throughout the entire swing angle range, preventing complete flow interruption and ensuring the continuous stability of the oil film pressure in oil chamber 40.

[0033] III. Variable control side piston assembly and buffer friction zone II The variable displacement control piston assembly includes a control rod 42, one end of which is threadedly fixed to the rear cover 2 and extends horizontally along the axial direction of the housing 1. A variable displacement piston 43 is coaxially sleeved on the outer periphery of the end of the control rod 42, and the variable displacement piston 43 and the control rod 42 slide in axial direction. A control oil unloading hole is provided inside the control rod 42. When the inner end face of the variable displacement piston 43 moves to communicate with the unloading hole, the control oil is unloaded, the swashplate 3 swing angle no longer decreases, and the minimum displacement position of the plunger pump is limited.

[0034] The variable piston 43 is provided with a support slipper 44 facing the tail end of the swashplate 3. The support slipper 44 and the swashplate 3 are connected by a support plunger 45. One end of the support plunger 45 is fixedly embedded inside the swashplate 3, and the other end is also connected to the support slipper 44 by a ball joint, which can adapt to the change of the swashplate 3's swing angle.

[0035] A buffer friction zone 46 is formed between the opposing end faces of the variable piston 43 and the second support slipper 44. An oil chamber 47 is recessed on the end face of the second support slipper 44 facing the variable piston 43. A low-pressure oil channel 48 is formed inside the second support plunger 45. One end of the low-pressure oil channel 48 is connected to the second oil chamber 47, and the other end is connected to the inner cavity of the housing 1. The inner cavity of the housing 1 is filled with low-pressure return oil. The low-pressure oil enters the second oil chamber 47 through the low-pressure oil channel 48, forming a low-pressure hydraulic oil film between the contact surfaces of the variable piston 43 and the second support slipper 44, achieving floating lubrication and reducing friction and wear. At the ball joint of the second support plunger 45 and the second support slipper 44, a connecting groove and a guide slope consistent with the structure on the reset side are provided to ensure continuous communication between the low-pressure oil channel 48 and the second oil chamber 47 throughout the entire swing angle range.

[0036] IV. Inclined runway buffer friction zone 3.51 A buffer friction zone 31 is formed between the high-pressure swashplate 30 and the sliding bearing 32, and a buffer friction zone 4 is formed between the low-pressure swashplate 31 and the sliding bearing 33.

[0037] The swash plate 3 has two internal high-pressure oil channels: a third high-pressure oil channel 49 and a fourth high-pressure oil channel 52. The inlet of the third high-pressure oil channel 49 is connected to the second high-pressure oil channel 41 inside the first support plunger 37, and the outlet extends to the surface of the high-pressure side swash plate track 30. The surface of the high-pressure side swash plate track 30 has a crescent-shaped floating support groove 50, which is connected to the outlet of the third high-pressure oil channel 49. High-pressure oil enters the crescent-shaped floating support groove 50 through the second high-pressure oil channel 41 and the third high-pressure oil channel 49, forming a high-pressure hydraulic oil film between the high-pressure side swash plate track 30 and the sliding bearing 32, separating the contact surface between the two into fluid friction.

[0038] The inlet end of high-pressure oil channel 42 is connected to high-pressure oil channel 21, and the outlet end extends to the surface of the low-pressure side swashplate track 31. A crescent-shaped floating support groove 23 is formed on the surface of the low-pressure side swashplate track 31, and the crescent-shaped floating support groove 253 is connected to the outlet end of high-pressure oil channel 42. High-pressure oil enters the crescent-shaped floating support groove 253 through high-pressure oil channel 21 and high-pressure oil channel 42, forming a hydraulic oil film between the low-pressure side swashplate track 31 and the sliding bearing 23, achieving floating lubrication.

[0039] The two crescent-shaped floating support grooves are designed with different dimensions according to the stress conditions of the corresponding runways: the high-pressure side has a large load, so the flow area and coverage area of ​​the crescent-shaped floating support groove 1 50 are larger to ensure sufficient oil film support force; the low-pressure side has a relatively small load, so the size of the crescent-shaped floating support groove 2 53 is adapted to the low-pressure load to control the amount of oil leakage while ensuring the lubrication effect.

[0040] V. Structure of Flow Control Valve The flow control valve includes a flow control valve body 6, in which a flow control valve core 60 is slidably mounted. One end of the valve core is limited and sealed by a screw plug; the other end of the valve core abuts against a flow regulating spring assembly 61. The flow control valve body 6 has multiple oil passages: a high-pressure oil passage 62 connects to the main pump body outlet; a control oil passage 63 connects to the variable piston chamber of the main pump body; a return oil passage 64 connects to the main pump body housing drain chamber; and a feedback oil passage 65 is used to connect to the load feedback pressure.

[0041] The flow regulating spring assembly 61 includes a flow spring seat 73, a large flow control spring 74, a small flow control spring 75, a flow regulating rod 76, and a flow regulating rod sleeve 77. The large flow control spring 74 and the small flow control spring 75 are coaxially nested, with their ends respectively abutting against the base end faces of the flow spring seat 73 and the flow regulating rod 76. The flow regulating rod sleeve 77 is threaded to the flow control valve body 6. The flow regulating rod 76 passes through the central hole of the flow regulating rod sleeve 77, and its end is axially locked by a nut 78. Rotating the flow regulating rod 76 changes the spring pre-compression, thereby adjusting the differential pressure setting value for flow control. An O-ring 79 and a retaining ring 80 are installed in the annular groove of the flow regulating rod 76 to achieve reliable sealing of the load feedback oil.

[0042] The outer wall of the flow control valve core 60 is provided with a damping groove, which cooperates with the valve core hole of the flow control valve body 6 to form damping B66 and damping C67. A flushing center hole 72 is provided in the axial center of the flow control valve core 60. The flushing center hole 72 is connected to the damping C67 to form a self-flushing circuit, which can carry away impurities in the gap of the flow control valve core 60 with the oil flow and prevent the valve core from sticking. A damping E68 is provided in the oil return channel 64. The damping E68 and the damping B66 are arranged in series, which can increase the motion damping of the flow control valve core 60, suppress valve core vibration caused by pressure shock, and make the flow output more stable.

[0043] A damper A96 is installed in the feedback oil passage 65 to filter out high-frequency fluctuations in the load feedback pressure signal and improve system stability. The flow control valve body 6 also has a control oil passage 69, which contains a damper D70. The flow control valve core 60 also has a variable damper 71. The dampers D70 and 71 work together to form a C-type hydraulic half-bridge, i.e., a half-bridge hydraulic control circuit composed of a fixed damper and a variable damper connected in series. This smooths the pressure gain curve and achieves precise and stable control of the hydraulic pressure in the control chamber.

[0044] VI. Power Control Valve Structure The power control valve includes a power control valve body 9, a power control valve sleeve 90 is assembled in the valve core through hole of the power control valve body 9, and a power control valve core 91 is slidably assembled in the power control valve sleeve 90; one end of the power control valve sleeve 90 abuts against the power adjustment spring assembly 92, and the other end is limited and sealed by a screw plug.

[0045] The power regulating spring assembly 92 includes a power spring seat 98, a large power regulating spring 99, a small power regulating spring 100, a power regulating rod 101, and a power regulating rod sleeve 102. The large power regulating spring 99 and the small power regulating spring 100 are coaxially nested, with their ends respectively abutting against the end faces of the power spring seat 98, the power regulating rod sleeve 102, and the power regulating rod 101. The power regulating rod sleeve 102 is threadedly connected to the power control valve body 9, and the power regulating rod 101 passes through the power regulating rod sleeve 102. Its end is axially locked by a nut 103. Rotating the power regulating rod 101 can adjust the spring pre-compression, thereby setting the constant power pressure threshold.

[0046] A feedback lever 59 is fixedly installed on the swashplate 3. The end of the feedback lever 59 is embedded in the slot 93 of the power control valve sleeve 90. When the swashplate 3 swings at different angles, it can drive the power control valve sleeve 90 to move axially synchronously, thus forming a mechanical negative feedback mechanism. One end of the power control valve core 91 has a control chamber, which is connected to the feedback oil passage 65 via the second feedback oil passage 95. The drain passage 97 of the power control valve is connected to the drain chamber of the main pump housing.

[0047] VII. Working Principle 1. Variable adjustment process In the initial state, high-pressure oil is continuously supplied to the reset side oil circuit. The high-pressure oil generates forward hydraulic pressure on the reset piston 35, which, combined with the spring force of the reset spring 340, pushes the reset piston 35, the support slipper 36, and the support plunger 37 together, keeping the swashplate 3 at the maximum swing angle position. The plunger pump outputs at the maximum displacement by default.

[0048] Constant flow mode (medium and low pressure conditions): After the high-pressure oil at the pump outlet is throttled by the external speed control valve, the pump outlet pressure and the load-side pressure are respectively introduced to both ends of the flow control valve core 60, forming a mechanical balance with the spring force of the flow regulating spring assembly on the right. When the load flow demand increases and the speed control valve opening widens, the throttling pressure difference decreases, and the flow control valve core 60 moves under the action of the spring force. The control oil passage 63 connects with the return oil passage 64, the variable piston chamber drains oil, the swashplate 3 swing angle increases, and the pump output flow increases. When the load flow demand decreases and the speed control valve opening narrows, the throttling pressure difference increases, the hydraulic thrust overcomes the spring force, and the flow control valve core 60 moves in the opposite direction. The high-pressure oil passage 62 connects with the control oil passage 63, and the high-pressure oil enters the variable piston chamber, pushing the swashplate 3 swing angle to decrease, and the pump output flow decreases. The throttling pressure difference of the speed control valve is maintained constant throughout the process, so that the pump output flow is only related to the valve opening, realizing on-demand flow supply and reducing overflow loss.

[0049] Constant power mode (high pressure heavy load condition): When the system pressure is lower than the power threshold, the power control valve core 91 remains in its initial position under the action of the spring force, the valve port is closed, and the normal operation of the flow control valve is not affected. The system operates in constant flow mode. When the system pressure rises to the power threshold, the hydraulic thrust in the control chamber overcomes the spring force of the power regulating spring assembly, pushing the power control valve core 91 to move, the valve port opens, and the control oil flows into the drain chamber of the housing through the drain channel 97; the oil flow creates a pressure difference at both ends of the damper A96, breaking the force balance of the flow control valve core 60, causing the flow control valve core 60 to move, the high pressure oil enters the variable piston chamber, and pushes the swashplate 3 to move in the direction of small swing angle, reducing the pump displacement.

[0050] As the swash plate 3 decreases in angle, the feedback lever 59 moves synchronously with it, pushing the power control valve sleeve 90 to move in the same direction, closing the valve port again. The system stabilizes at the operating point of "increased pressure and decreased flow," and the output power remains approximately constant. If the pressure continues to rise, the above process repeats, and the flow rate decreases synchronously with the pressure, always maintaining constant power characteristics. If the pressure decreases, the power control valve core 91 resets in the reverse direction, the pressure difference across damper A96 disappears, the flow control valve core 60 resets, the swash plate 3 increases in angle, the flow rate recovers, and finally stabilizes at the new constant power operating point.

[0051] 2. Lubrication and cooling process During the entire operation of the plunger pump, high-pressure oil enters oil chamber 40 through the high-pressure oil inlet passage of the rear cover 2 and the high-pressure oil passage 39 inside the reset piston 35, forming a high-pressure hydraulic oil film between the reset piston 35 and the support slipper 36. Part of the high-pressure oil is diverted through the connecting groove 57 and the high-pressure oil passage 41. One path enters the crescent-shaped floating support groove 50 through the high-pressure oil passage 49, forming a hydraulic oil film between the high-pressure side swashplate track 30 and the sliding bearing 32. The other path enters the crescent-shaped floating support groove 53 through the high-pressure oil passage 52, forming a hydraulic oil film between the low-pressure side swashplate track 31 and the sliding bearing 33. Low-pressure oil from the housing cavity is introduced into oil chamber 47 on the variable side through the low-pressure oil passage 48, forming a low-pressure oil film between the variable piston 43 and the support slipper 44.

[0052] All four friction pairs are lubricated by hydraulic oil film, with no direct contact between metal surfaces, which greatly reduces the coefficient of friction. The swashplate 3 swings flexibly, responds quickly to variables, and has high control precision. At the same time, the circulating oil continuously carries away the heat generated by friction, avoiding local high temperature accumulation and effectively extending the service life of the friction pairs and the whole machine.

[0053] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An axial piston variable displacement pump, comprising a main pump body, a flow control valve, and a power control valve, wherein the main pump body includes a housing, a swashplate located within the housing, and a rear cover fixedly and sealed to one end of the housing; the swashplate is provided with opposing piston drive assemblies, including a reset-side piston assembly and a variable displacement control-side piston assembly; a high-pressure side swashplate track and a low-pressure side swashplate track are respectively provided on the front and rear sides of the swashplate; a semi-circular support track one is provided on the inner wall of the housing corresponding to the high-pressure side swashplate track, and a semi-circular support track two is provided corresponding to the low-pressure side swashplate track; a sliding bearing one is provided between the high-pressure side swashplate track and the semi-circular support track one, and a sliding bearing two is provided between the low-pressure side swashplate track and the semi-circular support track two, characterized in that: The reset side piston assembly includes a reset rod fixed to the rear cover. The reset rod extends axially along the housing. A reset piston is coaxially sleeved on the outer periphery of its end. The reset piston and the reset rod slide in axial direction. The tail end of the reset piston is provided with a support slip shoe. The support slip shoe is assembled with the swashplate through a support plunger. A buffer friction area is formed between the reset piston and the support slip shoe. The rear cover has a high-pressure oil inlet channel that extends into the reset rod. The reset piston has an axially extending high-pressure oil channel that is connected to the high-pressure oil inlet channel. The support slipper has an oil chamber that is connected to the high-pressure oil channel inside the reset piston. The oil in the oil chamber generates a hydraulic oil film between the reset piston and the support slipper, forming the buffer friction zone. The variable control side piston assembly includes a control rod fixed to the rear cover. The control rod extends axially along the housing, and a variable piston is coaxially sleeved on the outer periphery of its end. The tail end of the variable piston is provided with a second support slipper. The second support slipper is assembled with the swashplate via a second support plunger. A second buffer friction zone is formed between the variable piston and the second support slipper. The second support slipper is provided with an oil chamber at one end corresponding to the variable piston. The second support plunger is provided with a low-pressure oil channel, which is connected to the inner cavity of the housing. Through the oil in the second oil chamber, a hydraulic oil film is generated between the variable piston and the second support slipper, forming the second buffer friction zone. The support plunger is provided with a high-pressure oil channel 2 that is connected to the oil chamber 1. A high-pressure oil channel 3 is provided on the swashplate. One end of the high-pressure oil channel 3 is connected to the high-pressure oil channel 2, and the other end extends into the high-pressure side swashplate track. A crescent-shaped floating support groove 1 is provided in the high-pressure side swashplate track. The oil passes through the crescent-shaped floating support groove 1, so that a hydraulic oil film is generated between the high-pressure side swashplate track and the sliding bearing 1, forming a buffer friction zone 3. A high-pressure oil channel four is also provided on the swashplate. One end of the high-pressure oil channel four is connected to the high-pressure oil channel two, and the other end extends into the low-pressure side swashplate track. A crescent-shaped floating support groove two is provided in the low-pressure side swashplate track. The oil passes through the crescent-shaped floating support groove two, so that a hydraulic oil film is generated between the low-pressure side swashplate track and the sliding bearing two, forming a buffer friction zone four.

2. The axial piston variable pump according to claim 1, characterized in that: The first support plunger is provided with a ball head assembly end, and the first support slipper is provided with an assembly groove adapted to the ball head assembly end at the end opposite to the first oil chamber. The ball head assembly end is hinged in the assembly groove and can rotate relative to it. The second high-pressure oil channel extends to the ball head assembly end, and the channel opening corresponds to the inner wall of the assembly groove. A connecting groove is provided between the first oil chamber and the assembly groove. The cross-sectional area of ​​the opening of the connecting groove at the end connecting the first oil chamber is smaller than the cross-sectional area of ​​the opening of the connecting groove at the end connecting the assembly groove.

3. An axial piston variable pump according to claim 1, characterized in that: The second high-pressure oil channel is located at the opening of the ball head assembly end. Guide slopes are provided on both sides of the ball head swing direction. Within the full range of rotation of the ball head assembly end in the assembly groove, the opening of the second high-pressure oil channel is always in fluid communication with the inlet of the connecting groove through the guide slopes.

4. An axial piston variable pump according to claim 1, characterized in that: The flow control valve includes a flow control valve body, a flow control valve core slidably mounted in the flow control valve body, and a flow regulating spring assembly located at one end of the valve core; the flow control valve body has a high-pressure oil passage five communicating with the oil outlet of the main pump body, a control oil passage one communicating with the variable piston chamber, a return oil passage communicating with the oil drain chamber of the main pump body housing, and a feedback oil passage one for connecting to the load feedback pressure.

5. An axial piston variable pump according to claim 4, characterized in that: The outer wall of the flow control valve core is provided with a damping groove, so the damping groove and the valve core hole of the flow control valve body cooperate to form damping B and damping C; the return oil channel is provided with damping E, and damping E and damping B are arranged in series; the flow control valve body is also provided with a second control oil passage, and damping D is provided in the second control oil passage; the flow control valve core is also provided with a variable damping, and damping D and variable damping cooperate to form a C-type hydraulic half-bridge; the axial center of the flow control valve core is provided with a flushing center hole, and the flushing center hole is connected with damping C to form a self-flushing circuit.

6. An axial piston variable pump according to claim 4, characterized in that: The flow regulating spring assembly includes a flow spring seat, a large flow control spring, a small flow control spring, a flow regulating rod, and a flow regulating rod sleeve. The large flow control spring and the small flow control spring are coaxially nested, with their two ends respectively abutting against the base end faces of the flow spring seat and the flow regulating rod. The flow regulating rod sleeve is threaded to the flow control valve body, and the flow regulating rod passes through the flow regulating rod sleeve and is axially locked by a nut.

7. An axial piston variable pump according to claim 6, characterized in that: The flow regulating rod has an O-ring and a retaining ring inside its annular groove for sealing the load feedback control oil.

8. An axial piston variable pump according to claim 4, characterized in that: The power control valve includes a power control valve body, a power control valve sleeve slidably mounted within the power control valve body, a power control valve core, and a power adjusting spring assembly located at one end of the power control valve sleeve; a feedback lever is fixedly connected to the swashplate, and the feedback lever is embedded in the slot of the power control valve sleeve to form a mechanical linkage; the power control valve core has a control cavity, and the control cavity is connected to a second feedback oil passage, which is connected to a first feedback oil passage, and the first feedback oil passage is provided with damping A; the oil drain passage of the power control valve is connected to the oil drain chamber of the main pump housing.

9. An axial piston variable pump according to claim 8, characterized in that: The power regulating spring assembly includes a power spring seat, a large power regulating spring, a small power regulating spring, a power regulating rod, and a power regulating rod sleeve. The large power regulating spring and the small power regulating spring are coaxially nested, with one end of each abutting against the power spring seat. The other end of the large power regulating spring abuts against the end face of the power regulating rod sleeve, and the other end of the small power regulating spring abuts against the end face of the power regulating rod. The power regulating rod sleeve is threaded to the power control valve body, and the power regulating rod passes through the power regulating rod sleeve and is axially locked by a nut.

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