Symmetrical digital axial plunger pump / motor

Abstract

The invention discloses a symmetric digital axial plunger pump / motor, and belongs to the field of hydraulic elements. The device comprises a fixed shell, a transmission shaft, a cam and plungers, the shell is hollow, plunger cavities are formed in the two sides of the shell, the transmission shaft is supported by a bearing, the cam is fixedly connected with the transmission shaft, the working face contours of the two sides of the cam are double rotational symmetric curved surfaces and are provided with guide grooves, and the plungers are axially installed in the plunger cavities and pressed by springs. And the head guide ball is in rolling contact with the cam guide groove. Under the pump working condition, the transmission shaft drives the cam to rotate, the curved surface of the cam enables the plungers on the two sides to move in a reciprocating mode, the single plunger completes two times of oil discharge and two times of oil suction every time the cam rotates by a circle, four strokes are achieved, and the symmetrical structure counteracts axial force. Under the working condition of the motor, the digital valve flow distribution system controls high-pressure oil to enter the plunger cavities to push the plungers, linear motion is converted into continuous rotation of the cam and the shaft through the balls, the single plunger completes two times of oil inlet and two times of oil return every time the single plunger rotates, and high-power-density conversion of mechanical energy and hydraulic energy is achieved.

Description

Technical Field

[0001] This invention belongs to the field of axial piston pumps / motors, specifically relating to a symmetrical digital axial piston pump / motor, and more particularly to an axial piston pump / motor structure based on digital valve flow distribution. Background Technology

[0002] Most existing axial piston pumps / motors adopt a fixed swashplate-slipper-piston structure. During operation, the slipper and swashplate are in sliding friction contact. Under wide speed and high pressure conditions, problems such as slipper oil film instability leading to accelerated wear and large sliding friction power loss resulting in limited mechanical efficiency are prone to occur. In existing swashplate rotary drive piston pumps / motors, the slipper load-bearing and lubrication are too difficult. More importantly, existing rotary swashplates usually only have a single working surface, and their contours are asymmetrical. This structure means that the axial force on the swashplate during rotation cannot be self-balanced, and the bearing must bear the entire load, limiting the increase in working pressure. At the same time, the asymmetrical mass distribution will generate significant centrifugal force and centrifugal torque at high speeds, causing vibration and noise, which seriously affects the smoothness of operation and service life.

[0003] Therefore, there is an urgent need for an axial piston pump / motor structure that is suitable for rotating swashplate operation, has a highly symmetrical structure and motion, low friction loss, stable motion, high operating efficiency, and can be combined with digital valve flow distribution. Summary of the Invention

[0004] The purpose of this invention is to provide a symmetrical digital axial piston pump / motor, in which both sides of the cam are working surfaces and both working surfaces adopt a double rotational symmetry design. Guided balls and guide grooves are used to replace the slipper structure, and multi-stage piston ring seals and digital valve flow distribution are combined to counteract axial force, improve operating efficiency, eliminate centrifugal torque, reduce friction loss, enhance speed adaptability and system control flexibility.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A symmetrical digital axial piston pump / motor includes a fixed housing, a drive shaft, a cam, a piston, and a digital valve distribution system; The fixed housing has a through hole at its center, and plunger cavities are provided on both sides of the fixed housing. The plunger cavities are evenly arranged around the through hole in a circumferential direction. The drive shaft is axially supported by a rolling bearing and a through hole in the fixed housing. The cam is fixedly connected to the drive shaft via a spline and is housed inside the fixed housing. Both sides of the cam are working surfaces with symmetrical curved surfaces. Guide grooves are provided on both working curved surfaces. The plunger assembly is axially engaged with the fixed housing through the plunger cavity, forming a volume cavity between them. The preload spring is positioned between the tail of the plunger assembly and the plunger cavity opening. The guide ball is positioned at the head of the plunger assembly and forms a ball joint connection with the plunger assembly, and engages with the guide grooves on both sides of the working curved surface of the cam. The digital valve distribution system is connected to each of the aforementioned volume chambers and is used to control the oil inlet and outlet of each of the aforementioned volume chambers; When the pump is in operation, as the drive shaft drives the cam to rotate relative to the fixed housing, each plunger assembly completes four working strokes within one rotation, including two discharge strokes and two suction strokes. During the discharge stroke, the plunger assembly is in the cam lift section, moving away from the cam, and the volume of the sealing cavity continuously decreases, squeezing out the oil inside. During the suction stroke, the plunger assembly is in the cam descent section, moving towards the cam side, and the volume of the sealing cavity continuously increases, allowing oil to flow into the sealing cavity, thus realizing the conversion between mechanical energy and hydraulic energy.

[0006] When the motor is in operation, as the digital valve distribution system alternately inputs high-pressure oil into the volume chamber and connects the low-pressure circuit, the high-pressure oil drives the plunger assembly to move. The reciprocating linear motion of the plunger assembly acts on the working surface of the cam through the cooperation of the guide balls and guide grooves, driving the cam and drive shaft to rotate continuously. Within one rotation of the cam, each plunger assembly completes four working strokes, including two oil inlet strokes and two oil return strokes, realizing the conversion between hydraulic energy and mechanical energy.

[0007] Furthermore, the drive shaft is positioned at the geometric center of the cam, and the axis of the drive shaft coincides with the axis of the cam.

[0008] Furthermore, the axial cross-section of the cam is circular.

[0009] Furthermore, the working surfaces on both sides of the cam are doubly rotationally symmetric, and the cam mass is uniformly distributed with the center of mass coinciding with the geometric center.

[0010] Furthermore, the working surfaces on both sides of the cam each have two maximum radial points and two minimum radial points.

[0011] Furthermore, the working surfaces on both sides of the cam are wear-resistant surfaces that have undergone surface strengthening treatment.

[0012] Furthermore, the guide ball profile is a smooth sphere.

[0013] Furthermore, the guide groove and the guide ball contour fit closely together to form a line contact, restricting the circumferential or radial crawling of the guide ball on the working surface of the cam.

[0014] Furthermore, the preload spring has sufficient clamping force, and the guide balls make rolling contact with the guide groove.

[0015] Furthermore, the digital valve distribution system includes multiple independently controlled high-speed switching valves, each of which is connected to a corresponding volumetric cavity.

[0016] Compared with the prior art, the beneficial effects of the present invention are: By using spherical guide balls to contact the working surface of the cam, the sliding friction of traditional slipper contact is transformed into rolling friction, significantly reducing friction loss. Both sides of the cam are working surfaces, and the lifting and lowering sections of the working surfaces on both sides are synchronized, which can effectively counteract the axial force of the plunger assembly on the cam. Each working surface of the cam has two maximum radial points and two minimum radial points. This design allows for a doubling of the number of plungers that can be housed within the same external dimensions. Furthermore, a single plunger assembly can complete two oil suction / discharge (or oil inlet / return) cycles per revolution of the cam, i.e., four working strokes. Compared to traditional single-acting plunger pumps / motors, its theoretical displacement or torque output capacity is doubled, significantly improving space utilization and power density. The cam's working surface geometry is doubly rotationally symmetrical and has a uniform mass distribution, achieving dynamic balance during rotation and avoiding centrifugal forces and torques during operation. Digital valve flow distribution replaces mechanical flow distribution, allowing for controllable flow distribution timing and a high degree of system freedom; Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a symmetrical digital axial piston pump / motor according to the present invention, wherein (a) is a side sectional view and (b) is a front view; Figure 2 This is a schematic diagram of the cam structure of the present invention, wherein, Figure 2 (a) Front view Figure 2 (b) is a side view. Figure 2 (c) is the top view; Figure 3 This is a schematic diagram of the plunger structure of the present invention; Figure 4 This is a schematic diagram of the oil circuit of the present invention; Figure 5 This is a schematic diagram of the application scheme of the present invention; Wherein: 1-Fixed housing; 2-Drive shaft; 3-Cam; 4-Plunger assembly; 5-Preload spring; 6-Plunger cavity; 7-Guide groove; 8-Maximum radial point of cam surface; 9-Minimum radial point of cam surface; 10-Guide ball; 11-Plunger; 12-High-speed switching valve; 13-Oil tank; 14-High-pressure accumulator; 15-Hydraulic cylinder; 16-Motor; 17-Digital hydraulic transformer; 18-Check valve; 19-Relief valve. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0020] See Figure 1 , Figure 1 This is a schematic diagram of the structure of a symmetrical digital axial piston pump / motor according to the present invention. Figure 1 (a) Figure 1 (b) are the side sectional view and the front view of the present invention, respectively; including a fixed housing 1, a drive shaft 2, a cam 3 and a plunger assembly 4. The drive shaft 2 and the cam 3 are rigidly connected and disposed in the fixed housing 1. Plunger cavities 6 are provided on both sides of the fixed housing 1. Plunger assemblies 4 are disposed in the plunger cavities 6. The head of the plunger assembly 4 cooperates with the cam 3.

[0021] See Figure 2 , Figure 2 (a), (b), and (c) are the front view, side view, and top view of the cam 3 of the present invention, respectively. The axial section of the cam 3 is circular, and both sides are working surfaces. The working surfaces are double rotationally symmetric curved surfaces. Each working surface has two maximum radial points 8 and two minimum radial points 9. Guide grooves 7 are provided on both sides of the working surfaces of the cam 3.

[0022] See Figure 3 , Figure 3 This is a schematic diagram of the plunger structure of the present invention. Figure 3 The diagram shows the configuration of the plunger assembly 4, which includes a plunger 11 and a guide ball 10 mounted on its head. A volume cavity is formed between the plunger assembly 4 and the plunger cavity 6. A preload spring 5 is disposed between the tail of the plunger assembly 4 and the plunger cavity opening. The guide ball 10 is disposed on the head of the plunger assembly 4 and cooperates with the guide grooves on both sides of the working curved surface of the cam 3.

[0023] The drive shaft 2 is axially supported by the through hole of the fixed housing 1 through the rolling bearing. The cam 3 is rigidly connected to the drive shaft 2 through the spline. The plunger assembly 4 is coaxially connected to the plunger cavity 6. The guide ball 10 is ball-jointed to the head of the plunger body 11. The guide ball 10 and the guide groove 7 are in line contact rolling fit.

[0024] See Figure 4 , Figure 5 Each plunger chamber 6 has two high-speed switching valves 12, which are used to control the connection and disconnection between the plunger chamber and the load working circuit. By receiving commands and sensor signals and outputting control signals, the drive source of the transmission shaft 2 and the actions of all high-speed switching valves 12 are synchronized and coordinated.

[0025] The high-speed switching valve 12 allows the plunger chamber 6 to draw oil from the low-pressure circuit during the suction stroke and discharge oil to the high-pressure circuit during the discharge stroke; Pump operation: When the drive shaft 2 drives the cam 3 to rotate relative to the fixed housing 1, within one rotation, a single plunger assembly 4 completes four working strokes, including two oil discharge strokes and two oil suction strokes. Oil discharge stroke: The plunger assembly 4 is in the lifting section of the cam 3. The plunger assembly 4 moves away from the cam 3, and the volume of the sealing cavity continuously decreases, and the oil in the cavity is squeezed out. Oil suction stroke: The plunger assembly 4 is in the descending section of the cam 3. The plunger assembly 4 moves towards the cam 3, and the volume of the sealing cavity continuously increases, and the oil flows into the sealing cavity, realizing the conversion between mechanical energy and hydraulic energy.

[0026] Motor operating condition: The sealed working chambers of each plunger assembly 4 are connected to the high-pressure oil circuit and the low-pressure circuit respectively through independent high-speed switching valves 12. By coordinating the opening and closing sequence of each high-speed switching valve 12 to synchronize with the rotational position of the cam 3, it can be ensured that: when a plunger assembly 4 moves to the lifting section of the cam 3, its corresponding working chamber is connected to the high-pressure oil circuit, and the high-pressure oil pushes the plunger assembly to do work, converting hydraulic energy into torque to drive the cam 3 to rotate; when the plunger assembly moves to the lowering section, its working chamber switches to the low-pressure circuit, and resets and returns oil under the combined action of the preload spring 5 and the cam profile. For each rotation of the cam 3, each plunger assembly 4 will complete two such "oil inlet-work-oil return" cycles. All plunger assemblies 4 work in sequence, thereby generating a continuous and stable total output torque.

[0027] In this specification, the illustrative expressions of the terms used do not necessarily refer to the same embodiments / modes or examples. Furthermore, the specific features, structures, materials, or characteristics described may be present in one or more embodiments / modes or examples. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of those different embodiments / modes or examples.

[0028] Furthermore, in the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0029] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A symmetrical digital axial piston pump / motor, characterized in that, It includes a fixed housing (1), a drive shaft (2), a cam (3), a plunger assembly (4), and a digital valve distribution system; The fixed housing (1) has a through hole at its center, and plunger cavities (6) are provided on both sides of the fixed housing (1). The plunger cavities (6) are evenly arranged around the through hole. The drive shaft (2) is axially supported by a rolling bearing and a through hole in the fixed housing (1); The cam (3) is fixedly connected to the transmission shaft (2) by a spline and is disposed inside the fixed housing (1). Both sides of the cam (3) are working surfaces and the contours of the working surfaces are symmetrical curved surfaces. Guide grooves (7) are provided on both working curved surfaces. The plunger assembly (4) is axially engaged with the fixed housing (1) through the plunger cavity (6), forming a volume cavity between the plunger assembly (4) and the plunger cavity (6). The preload spring (5) is disposed between the tail of the plunger assembly (4) and the plunger cavity opening. The guide ball (10) is disposed at the head of the plunger assembly (4) and forms a ball joint connection with the plunger assembly (4), and engages with the guide groove (7) on both sides of the working curved surface of the cam. The digital valve distribution system is connected to each of the volume chambers respectively, and is used to control the oil inlet and outlet of each volume chamber; When the pump is in operation, when the drive shaft (2) drives the cam (3) to rotate relative to the fixed housing (1), each plunger assembly (4) completes four working strokes within one rotation, including two oil discharge strokes and two oil suction strokes. Oil discharge stroke: the plunger assembly (4) is in the lifting section of the cam (3), the plunger assembly (4) moves away from the cam (3), the volume of the sealing cavity continuously decreases, and the oil in the cavity is squeezed out. Oil suction stroke: the plunger assembly (4) is in the falling section of the cam (3), the plunger assembly (4) moves to the side of the cam (3), the volume of the sealing cavity continuously increases, and the oil flows into the sealing cavity, realizing the conversion between mechanical energy and hydraulic energy.

2. When the motor is in operation, when the digital valve distribution system alternately inputs high-pressure oil into the volume chamber and connects the low-pressure circuit, the high-pressure oil pushes the plunger assembly (4) to move towards the cam (3). The reciprocating linear motion of the plunger assembly (4) acts on the working surface of the cam (3) through the cooperation of the guide ball (10) and the guide groove (7), driving the cam (3) and the transmission shaft (2) to rotate continuously. In the time it takes for the cam (3) to rotate once, each plunger assembly (4) completes four working strokes, including two oil inlet strokes and two oil return strokes, realizing the conversion between hydraulic energy and mechanical energy.

3. The symmetrical digital axial piston pump / motor according to claim 1, characterized in that, The drive shaft (2) is located at the geometric center of the cam (3), and the axis of the drive shaft (2) coincides with the axis of the cam (3).

4. The symmetrical digital axial piston pump / motor according to claim 1, characterized in that, The axial section of the cam (3) is circular.

5. The symmetrical digital axial piston pump / motor according to claim 1, characterized in that, The working surfaces on both sides of the cam (3) are both double rotationally symmetric, and the mass of the cam (3) is uniformly distributed, with the center of mass coinciding with the geometric center.

6. The symmetrical digital axial piston pump / motor according to claim 1, characterized in that, The working surfaces on both sides of the cam (3) have two maximum radial points (8) and two minimum radial points (9).

7. The symmetrical digital axial piston pump / motor according to claim 1, characterized in that, The working surfaces on both sides of the cam (3) are wear-resistant surfaces that have undergone surface strengthening treatment.

8. The symmetrical digital axial piston pump / motor according to claim 1, characterized in that, The guide ball (10) has a smooth spherical profile.

9. The symmetrical digital axial piston pump / motor according to claim 1, characterized in that, The guide groove (7) and the guide ball (10) are closely fitted to form a line contact, which restricts the circumferential or radial crawling of the guide ball (10) on the working surface of the cam (3).

10. The symmetrical digital axial piston pump / motor according to claim 1, characterized in that, The preload spring (5) has sufficient clamping force, and the guide ball (10) and guide groove (7) make rolling contact.

11. The symmetrical digital axial piston pump / motor according to claim 1, characterized in that, The digital valve distribution system includes multiple independently controlled high-speed switching valves, each of which is connected to a corresponding volumetric cavity.

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