Variable axial plunger pump

Abstract

The present application provides a variable axial plunger pump characterized by comprising: a swash plate in which a plurality of plungers are rotatably fastened to the swash plate, the stroke of reciprocating motion of the plurality of plungers in a cylinder bore being associated with the tilt angle of the swash plate, a first control plunger assembly positioned on a first side of the swash plate, a second control plunger assembly positioned on a second side of the swash plate, and a third control plunger assembly positioned on a third side of the swash plate, and a second control plunger assembly positioned on a second side of the swash plate, where the first side and the second side are radially opposite with respect to a central axis of the swash plate, the variable axial plunger pump is configured to adjust the inclination angle of the swash plate via hydraulic fluid flowing into and out of the first control plunger assembly and the second control plunger assembly, and wherein the second control plunger assembly further comprises a one-way valve, and the pressure relief valve is positioned in a pressure relief channel inside the second control plunger assembly so as to control hydraulic fluid in the second control plunger assembly to flow into a shell of the variable displacement type axial plunger pump through the pressure relief channel.

Description

TECHNICAL FIELD

[0001] The present application relates to a variable axial piston pump. BACKGROUND

[0002] As a key component of hydraulic systems, variable axial piston pumps have many advantages over other types of hydraulic pumps, such as high pressure operation, high efficiency, compact structure, adjustable displacement, etc., and are therefore widely used in various engineering machines that require hydraulic systems.

[0003] Generally, the displacement of a variable axial piston pump is changed by adjusting the tilt angle of a swash plate to change the stroke of pistons. The adjustment of the tilt angle of the swash plate is achieved by a control piston connected to the swash plate.

[0004] During the use of a variable axial piston pump, in some specific situations, it is necessary to adjust the swash plate back to a neutral position, at which the axis of the swash plate coincides with the axis of the pump body of the piston pump. It is desirable that the swash plate can return to the neutral position at the fastest speed.

[0005] However, in actual use, the tilt angle of the swash plate will swing back and forth around the axis of the piston pump several times before finally returning to the neutral position. This back-and-forth swinging is undesirable because it will cause the high-pressure area and the low-pressure area of the piston pump to exchange several times. In practical applications, this phenomenon has adverse effects on the piston pump itself and even on the mechanical equipment using the hydraulic system including the piston pump, such as premature aging and / or functional failure of the piston pump, and unsafe operation of the mechanical equipment, etc.

[0006] In view of the above and other considerations, it is desirable to provide a new type of variable axial piston pump to solve or at least alleviate the above problems. SUMMARY

[0007] The present application aims to provide a variable axial piston pump, which is advantageous in at least one aspect over the prior art.

[0008] To this end, the present application provides a variable axial piston pump comprising: a swash plate, wherein a plurality of pistons are rotatably fastened to the swash plate, a stroke of the plurality of pistons in a cylinder bore is associated with an inclination angle of the swash plate, a first control piston assembly positioned on a first side of the swash plate, and a second control piston assembly positioned on a second side of the swash plate, wherein the first side and the second side are diametrically opposite with respect to a central axis of the swash plate, wherein the variable axial piston pump is configured to be able to adjust the inclination angle of the swash plate via a flow of hydraulic fluid into and out of the first control piston assembly and the second control piston assembly, and wherein the second control piston assembly further comprises a one-way valve positioned in a pressure relief passage inside the second control piston assembly to control a flow of hydraulic fluid located in the second control piston assembly out of the second control piston assembly into a housing of the variable axial piston pump via the pressure relief passage.

[0009] In a feasible exemplary embodiment, the first control piston assembly comprises a first sleeve structure, an inside of the first sleeve structure is hollow to form a first working chamber, and the second control piston assembly comprises a second sleeve structure, an inside of the second sleeve structure is hollow to form a second working chamber,

[0010] wherein a cross-sectional area of the second working chamber is greater than a cross-sectional area of the first working chamber.

[0011] In a feasible exemplary embodiment, the first control piston assembly further has a first control piston, the first control piston is configured to be able to extend into the first working chamber via a first end and to be able to be rotatably connected to the first side of the swash plate via a second end.

[0012] In a feasible exemplary embodiment, the second control piston assembly further has a second control piston, the second control piston is configured to be able to extend into the second working chamber via a third end and to be able to be rotatably connected to the second side of the swash plate via a fourth end, and wherein a cross-sectional area of the second control piston is greater than a cross-sectional area of the first control piston.

[0013] In a feasible exemplary embodiment, the second control piston assembly further comprises the pressure relief passage, the pressure relief passage is opened in the inside of the second control piston, and is configured to be able to communicate high-pressure hydraulic fluid located in the second working chamber to the housing outside the second working chamber when the swash plate is in a neutral position.

[0014] In a feasible exemplary embodiment, the pressure relief passage comprises a first pressure relief section extending parallel to or along an axis of the second working chamber and a second pressure relief section perpendicular to and communicating to the first pressure relief section.

[0015] In a possible exemplary embodiment, the second pressure relief section is configured to be in fluid communication to a fluid passage within the housing in case the swash plate is in the neutral position.

[0016] In a possible exemplary embodiment, the one-way valve is positioned in the first pressure relief section and is configured to fluidly communicate the second working chamber to the second pressure relief section in case the one-way valve is in the open position, and to fluidly isolate the second working chamber from the second pressure relief section in case the one-way valve is in the closed position.

[0017] In a possible exemplary embodiment, the variable axial piston pump is configured to position the one-way valve in the open position in case a first electrical signal is received, and / or to position the one-way valve in the closed position in case a second electrical signal is received.

[0018] In a possible exemplary embodiment, the one-way valve is configured to be movable into the open position in case the hydraulic pressure in the second working chamber is greater than or equal to a predetermined hydraulic pressure threshold Pre thd , and to be movable into the closed position in case the hydraulic pressure in the second working chamber is less than the predetermined hydraulic pressure threshold Pre thd .

[0019] The variable axial piston pump according to the present application has at least the advantage that it enables the variable axial piston pump to return to the neutral position in a fast responding manner, while avoiding the undesired mutual transition between the high pressure zone and the low pressure zone, thereby providing a more efficient and robust variable axial piston pump. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A schematic view of a variable axial piston pump according to an embodiment of the present application is shown.

[0021] Figure 2 A variable axial piston pump in Figure 1 is shown in simplified form. DETAILED DESCRIPTION

[0022] Some possible embodiments of the present application are described below, with reference to the accompanying drawings. It is noted that the figures are not drawn to scale. Certain details may be exaggerated, while some unnecessary particulars are omitted. In order to simplify the present application, some terms are used without a specific definition in the background of the present application.

[0023] As Figures 1-2 shown, a schematic view of a variable axial piston pump 100 according to an embodiment of the present application is shown.

[0024] The variable displacement axial piston pump 100 includes a housing 101 with an opening and an end plate 102 covering the opening of the housing to close the housing 101. A distribution plate (not shown) may be configured on the end plate 102 to guide the flow of hydraulic fluid in and out.

[0025] The variable displacement axial piston pump 100 also includes a cylinder 103 and a plurality of pistons (not shown) that cooperate with the cylinder. The cylinder 103 is mounted on a spindle 105 and configured to rotate with the spindle 105. The cylinder 103 may have a (basically) cylindrical geometry. The axis of rotation of the spindle 105 coincides with the central axis of the cylinder 103. The plurality of pistons are also circumferentially distributed around the spindle 105.

[0026] The cylinder body 103 has multiple cylinder bores (not shown) adapted to accommodate multiple plungers that can reciprocate within them. The reciprocating motion of the multiple plungers in the multiple cylinder bores allows hydraulic fluid to be drawn in and discharged from the multiple cylinder bores accordingly (through the distribution plate 106).

[0027] It is understood that the number of the plurality of plungers can be three or more, for example, five, seven, or nine. In some specific cases, the number of the plurality of plungers can also be an even number, such as four, six, eight, or ten. It is understood that the number of the plurality of cylinder bores is configured to be equal to the number of the plurality of plungers.

[0028] The variable displacement axial piston pump 100 also includes a swashplate 107. The plurality of pistons are rotatably secured to the swashplate 107. The stroke of the pistons reciprocating within the cylinder bore (also referred to as piston stroke) is related to the tilt angle of the swashplate 107. The larger the tilt angle of the swashplate 107, the greater the stroke of the pistons within the cylinder bore. It can be understood that the tilt angle of the swashplate 107 refers to the relative angle between the central axis of the swashplate 107 and the axis of the main shaft 105.

[0029] The tilt angle of the swashplate 107 is configured to be adjustable. For example... Figure 1 As shown, the swashplate 107 is configured to adjust the tilt angle of the swashplate 107 via a first control plunger assembly 108a positioned on a first side 107a of the swashplate 107 and a second control plunger assembly 108b positioned on a second side 107b of the swashplate 107. The tilt angle can be adjusted, for example, in the range of approximately 0-16 degrees, approximately 0-18 degrees, or approximately 0-20 degrees. The first side 107a and the second side 107b are radially opposite to each other relative to the central axis of the swashplate 107 (positioned on opposite sides of each other).

[0030] For example, in the case where the swash plate 107 has a zero inclination angle, by moving the first control plunger assembly 108a in the direction of the axial direction (with respect to the main shaft 105) toward the swash plate 107 (i.e., away from the end plate 102) and moving the second control plunger assembly 108b in the direction of the axial direction (with respect to the main shaft 105) away from the swash plate 107 (i.e., toward the end plate 102), the inclination angle of the swash plate 107 can be increased accordingly, thereby increasing the displacement of the variable axial piston pump 100. Correspondingly, in the case where the swash plate 107 has a zero inclination angle, by moving the second control plunger assembly 108b in the direction toward the swash plate 107 and moving the first control plunger assembly 108a in the direction away from the swash plate 107, the inclination angle of the swash plate 107 can be decreased accordingly, thereby decreasing the displacement of the variable axial piston pump 100.

[0031] One possible case is that the first control plunger assembly 108a is configured to have a first sleeve structure 1. The first sleeve structure 1 can be shaped as a cuboid or a cylinder. The inside of the first sleeve structure 1 is hollow to form a first working chamber (not shown) and has a first opening (not shown) open to the swash plate 107. In addition, at the other end (first opening end) 1b opposite to the end (first opening end) 1a where the first opening is located, the first sleeve structure 1 is configured with an opening 5 for the inflow and outflow of hydraulic fluid.

[0032] The first control plunger assembly 108a also has a first control plunger 4. The first control plunger 4 has two ends opposite to each other: a first end 41 (hidden by a spring in the figure, showing the approximate position) and a second end 42. The first end 41 can extend into the first working chamber of the first sleeve structure 1 from the first opening of the first sleeve structure 1 and close (or substantially close, without considering liquid leakage) the first opening. The second end 42 is rotatably connected (e.g., hinged) to the first side 107a of the swash plate 107.

[0033] The first control plunger assembly 108a also includes a first return spring 6 for returning the first control plunger 4 (in the direction away from the swash plate 107). One end of the first return spring 6 is fixed to the wall of the first working chamber (e.g., the wall at the first opening end 1a), and the opposite end is fixed to the first control plunger 4. The first return spring 6 can be a compression spring.

[0034] In the case where the hydraulic fluid flows from the first opening into the first working chamber, the static pressure of the hydraulic fluid pushes the first control plunger 4 to move in the direction toward the first working chamber (i.e., the direction in which the first working chamber increases), so that the first control plunger 4 pushes the swash plate 107 to rotate in the first rotation direction A. Thus, the inclination angle of the swash plate 107 is increased.

[0035] Correspondingly, in the case that hydraulic fluid flows out of the first working chamber from the first opening, the first return spring 6 pushes the first control plunger 4 to move in the direction of extending into the first working chamber (i.e. the direction in which the first working chamber becomes smaller), so that the first control plunger 4 drives the swash plate 107 to rotate in the second rotation direction B opposite to the first rotation direction A. Thus, the inclination angle of the swash plate 107 is reduced.

[0036] In addition, a possible case is that the second control plunger assembly 108b is configured to have a second sleeve structure 10.

[0037] The second sleeve structure 10 can be shaped as a cuboid or a cylinder. For example, the three-dimensional shape of the second sleeve structure 10 can be substantially the same as that of the first sleeve structure 1. In this way, it is convenient for many process flows including manufacturing and processing. For another example, the three-dimensional shape of the second sleeve structure 10 can be different from that of the first sleeve structure 1. For example, the shape of the first sleeve structure 1 is a cylinder, while the shape of the second sleeve structure 10 is a cuboid; for another example, the shape of the first sleeve structure 1 is a cuboid, while the shape of the second sleeve structure 10 is a cylinder. It can be understood that the specific shape to be adopted can be determined according to the structure and space of the variable axial plunger pump 100.

[0038] The inside of the second sleeve structure 10 is hollow to form a second working chamber 20. The cross-sectional area of the second working chamber 20 is configured to be greater than that of the first working chamber. In this way, it can be understood that in the case of simultaneously applying hydraulic changes (e.g. controlled by a solenoid valve) to the first working chamber and the second working chamber, because the cross-sectional area of the first working chamber is different from that of the second working chamber, the force applied to the first control plunger 4 and the second control plunger is different, and thus the swash plate rotates accordingly.

[0039] The second sleeve structure 20 also has a second opening 30 facing the swash plate 107 open. In addition, at the other end (second opening end) opposite to the end (second opening end) where the second opening 30 is located, the second sleeve structure 10 is configured with a second opening for the inflow and outflow of hydraulic fluid.

[0040] The second control plunger assembly 108b also has a second control plunger 40. Correspondingly, the second control plunger 40 has a cross-sectional area larger than that of the first control plunger 4. The second control plunger 40 has two ends opposite to each other: a third end 401 and a fourth end 402. The third end 401 is capable of extending into the second working chamber 20 of the second sleeve structure 10 from the second opening 30 of the second sleeve structure 10 and is configured to be capable of closing (or substantially closing, without considering liquid leakage) the second opening 30. The fourth end 402 is rotatably connected (e.g., hinged) to the second side 107b of the swash plate 107 via a linkage structure 402a, as shown in Figure 1 The cross-sectional area of the linkage structure 402a can be configured to be smaller than that of the second control plunger 40. This can be advantageous, especially considering that material usage can be saved, the structure can be compact, and / or control of the swash plate 107 can be facilitated. In addition, alternatively or additionally, the cross-sectional area of the linkage structure 402a can be configured to be substantially equal to that of the first control plunger 4.

[0041] On the other hand, it can also be envisaged that the second control plunger 40 can be configured to be directly rotatably connected to the second side 107b of the swash plate 107 via the fourth end 402, without using the linkage structure 402a. In this way, the structural complexity and manufacturing difficulty can also be simplified.

[0042] The second control plunger assembly 108b also includes a second return spring 60 for returning the second control plunger 40 (towards a direction away from the swash plate 107). One end of the second return spring 60 is fixed to a wall of the second working chamber 20 (e.g., at the second opening end), and the opposite end is fixed to the second control plunger 40. The second return spring 60 can be a tension spring.

[0043] In addition, the second control plunger assembly 108b also includes a pressure relief passage 200. The pressure relief passage 200 is formed in the interior of the second control plunger 40 and is configured to be capable of connecting the high-pressure hydraulic fluid in the second working chamber 20 to the housing 101 outside the second working chamber 20 when the swash plate 107 is in the neutral position (swash plate inclination angle of 0 degrees), so as to further flow back to the oil tank (not shown).

[0044] The pressure relief passage 200 can include a first pressure relief section 201 extending parallel to or along the axis of the second working chamber 20 and a second pressure relief section 202 perpendicular to and connected to the first pressure relief section 201. The second pressure relief section 202 is configured to be capable of fluidly connecting to the housing 101, e.g., a fluid passage in the housing 101, when the swash plate 107 is in the neutral position.

[0045] The second control plunger assembly 108b further comprises a one-way valve 500, which can be arranged in the pressure relief channel 200, for controlling the outflow of hydraulic fluid from the second control plunger assembly 108b (via the pressure relief channel 200) into the housing 101. The one-way valve 500 is positionable in the first pressure relief section 201 and configured to fluidly connect the second working chamber 20 to the second pressure relief section 202 in case the one-way valve 500 is in an open position, and to fluidly isolate the second working chamber 20 from the second pressure relief section 202 in case the one-way valve 500 is in a closed position.

[0046] It is appreciated that the one-way valve 500 can also be electrically controllable. In case a first electrical signal is received, the one-way valve 500 is brought into the open position, and / or in case a second electrical signal is received, the one-way valve 500 is brought into the closed position. The first electrical signal and the second electrical signal can be the same or different.

[0047] Another possibility is that the one-way valve 500 can be hydraulically controllable. For example, the one-way valve 500 is configured to be movable into the open position in case the hydraulic pressure in the second working chamber 20 is greater than or equal to a predetermined hydraulic pressure threshold Pre thd , and to be movable into the closed position in case the hydraulic pressure in the second working chamber 20 is less than the predetermined hydraulic pressure threshold Pre thd .

[0048] In case hydraulic fluid flows out of the second working chamber 20 from the second opening 30, the second return spring 60 pulls the second control plunger 40 in a direction in which the second control plunger 40 protrudes into the second working chamber 20 (i.e. in a direction in which the second working chamber 20 becomes smaller), so that the second control plunger 40 brings the swash plate 107 into rotation in the first rotational direction A. Thereby, the inclination angle of the swash plate 107 is increased.

[0049] Correspondingly, in case hydraulic fluid flows into the second working chamber 20 from the second opening 30, the static pressure of the hydraulic fluid pushes the second control plunger 40 in a direction in which the second control plunger 40 protrudes out of the second working chamber 20 (i.e. in a direction in which the second working chamber 20 becomes larger), so that the second control plunger 40 pushes the swash plate 107 into rotation in the second rotational direction B. Thereby, the inclination angle of the swash plate 107 is decreased.

[0050] In case the swash plate 107 is rotated into the neutral position, and when the hydraulic pressure in the second working chamber 20 is greater than or equal to the predetermined hydraulic pressure threshold Pre thdWhen the pressure in the second working chamber 20 exceeds the pressure in the first working chamber 10, the one-way valve 500 moves into the open position, so that the hydraulic fluid in the second working chamber 20 flows out into the housing 101 via the pressure relief channel 200, in particular the first pressure relief section 201 and the second pressure relief section 202, thereby reducing the hydraulic pressure in the second working chamber 20 in time, so that the swash plate 107 does not further rotate in the second rotational direction B to avoid causing a negative inclination angle of the swash plate 107. In this way, it is possible to avoid the suction and discharge areas of the variable axial piston pump 100 exchanging with each other and the corresponding hazards caused thereby.

[0051] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or variations thereof, are intended to be open-ended and do not limit the component, element, or feature to which the terms are applied to or the process, process step, or process steps with which it is associated, to the specific components, elements, features, or process, process steps, or process steps listed and / or to corresponding full

[0052] The foregoing description of embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the application be limited not with the recited embodiments, but rather by the appended claims, taking into account the full scope of equivalents thereof. That is, all embodiments and / or characteristics of any embodiment can be taken in any combination. It is intended that each of the recited features can be used to the exclusion of the other described features or that each described feature can be used in combination with the other described features. It is further intended that the various aspects, embodiments, examples and alternatives set forth herein can be used in any and all combinations. It is intended that the scope of the application be limited only by the appended claims. Applicant reserves the right to change any subsequently filed application or subsequent filings of the present application, including any amendments thereof, to conform to the specifications and to pursue patent protection under any other available patent law.

Claims

1. A variable capacity axial piston pump characterized by, Comprising: a swash plate (107), wherein a plurality of plungers are rotatably fastened to the swash plate (107), the plurality of plungers associated with an angle of inclination of the swash plate (107) in relation to a stroke of reciprocating movement in a cylinder bore, a first control plunger assembly (108a) positioned on a first side (107a) of the swash plate (107), and a second control plunger assembly (108b) positioned on a second side (107b) of the swash plate (107), wherein the first side (107a) and the second side (107b) are diametrically opposite with respect to a central axis of the swash plate (107), wherein the variable axial piston pump is configured to be able to adjust the angle of inclination of the swash plate (107) via a flow of hydraulic fluid into and out of the first control plunger assembly (108a) and the second control plunger assembly (108b), and wherein the second control plunger assembly (108b) further comprises a one-way valve (500) positioned in a pressure relief channel (200) inside the second control plunger assembly (108b) to control a flow of hydraulic fluid located in the second control plunger assembly (108b) out of the second control plunger assembly (108b) into a housing (101) of the variable axial piston pump via the pressure relief channel (200).

2. The variable axial piston pump according to claim 1, characterized in that The first control plunger assembly (108a) comprises a first sleeve structure (1) which is hollow inside to form a first working chamber, and the second control plunger assembly (108b) comprises a second sleeve structure (10) which is hollow inside to form a second working chamber (20), wherein a cross-sectional area of the second working chamber (20) is greater than a cross-sectional area of the first working chamber.

3. A variable axial piston pump according to claim 2, characterized in that The first control plunger assembly (108a) further comprises a first control plunger (4) which is configured to be able to extend into the first working chamber via a first end (41) and to be rotatably connected to the first side (107a) of the swash plate (107) via a second end (42) with respect to the swash plate (107).

4. The variable axial piston pump according to claim 3, characterized in that The second control plunger assembly (108b) further comprises a second control plunger (40) which is configured to be able to extend into the second working chamber (20) via a third end (401) and to be rotatably connected to the second side (107b) of the swash plate (107) via a fourth end (402) with respect to the swash plate (107), wherein a cross-sectional area of the second control plunger (40) is greater than a cross-sectional area of the first control plunger (4).

5. The variable axial piston pump according to claim 4, characterized in that The second control plunger assembly (108b) further comprises the pressure relief channel (200) which is opened in the inside of the second control plunger (40) and is configured to be able to communicate high-pressure hydraulic fluid located in the second working chamber (20) to the housing (101) outside the second working chamber (20) in the case that the swash plate (107) is in a neutral position.

6. The variable axial piston pump according to claim 5, characterized in that The pressure relief passage (200) comprises a first pressure relief section (201) extending parallel to or along an axis of the second working chamber (20) and a second pressure relief section (202) perpendicular to and communicating to the first pressure relief section (201).

7. A variable axial piston pump according to claim 6, characterized in that The second pressure relief section (202) is configured to be in fluid communication to a fluid passage within the housing (101) with the swash plate (107) in a neutral position.

8. The variable axial piston pump according to claim 7, characterized in that The one-way valve (500) is positioned in the first pressure relief section (201) and is configured to fluidly communicate the second working chamber (20) to the second pressure relief section (202) with the one-way valve (500) in an open position and to fluidly isolate the second working chamber (20) from the second pressure relief section (202) with the one-way valve (500) in a closed position.

9. Variable axial piston pump according to any of claims 1 - 8, characterized in that The variable axial piston pump is configured to position the one-way valve (500) in the open position upon receipt of a first electrical signal and / or in the closed position upon receipt of a second electrical signal.

10. A variable axial piston pump according to any one of claims 2-8, characterized in that The one-way valve (500) is configured to be movable into an open position in case the hydraulic pressure in the second working chamber (20) is greater than or equal to a predetermined hydraulic pressure threshold Pre thd and into a closed position in case the hydraulic pressure in the second working chamber (20) is less than the predetermined hydraulic pressure threshold Pre thd .

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