Axial piston device

Abstract

To suppress noise in an axial piston device used as, for example, a hydraulic pump or a hydraulic motor of a hydrostatic continuously variable transmission.SOLUTION: A port block 3 has a supply / discharge port surface 15 with which a cylinder block contacts while rotating, first ports 11, 12, and 13, and second ports 21, 22, and 23. On at least one of a first dead center part 16 and a second dead center part 17, recessed portions 18 and 19 are formed on the supply / discharge port surface 15 from one of the first ports 11 and 13 and the second ports 21 and 23 located on the downstream side in a rotating direction A1 of the cylinder block toward the upstream side in the rotating direction A1 of the cylinder block.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an axial piston device used, for example, as a hydraulic pump or a hydraulic motor of a hydrostatic continuously variable transmission.

Background Art

[0002] In the axial piston device disclosed in Patent Document 1, a port block is provided with a supply / discharge port surface, a first port and a second port formed on the supply / discharge port surface. A cylinder block is provided with a cylinder port surface, a plurality of cylinder chambers, pistons, and a cylinder port formed across the cylinder port surface and the cylinder chambers.

[0003] In the axial piston device disclosed in Patent Document 1, assuming a hydraulic pump in which the cylinder block is rotationally driven by external power, attention is paid to one set of cylinder ports, cylinder chambers, and pistons. At the phase where the cylinder port faces the first port, the piston moves to the side away from the cylinder port, and the hydraulic oil is sucked from the first port through the cylinder port into the cylinder chamber. At the phase where the cylinder port faces the second port, the piston moves to the side approaching the cylinder port, and the hydraulic oil in the cylinder chamber is discharged from the cylinder port to the second port. In this case, the first port through which the hydraulic oil is sucked into the cylinder chamber is at a low pressure, and the second port through which the hydraulic oil is discharged from the cylinder chamber is at a high pressure.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, when a cylinder port moves from a low-pressure first port to a high-pressure second port, the cylinder port transitions from a state where it is connected to the low-pressure first port to a state where it is closed by the supply and discharge port surface of the port block.

[0006] As mentioned above, when the cylinder port moves from being connected to the low-pressure first port to being closed by the supply and discharge port surface, the area of ​​communication between the cylinder port and the low-pressure first port decreases, which can cause the pressure in the cylinder chamber to drop rapidly. When this occurs, the noise from the axial piston device increases, so there is room for improvement.

[0007] In Patent Document 1, when a cylinder port moves from a high-pressure second port to a low-pressure first port, the cylinder port transitions from a state where it is connected to the high-pressure second port to a state where it is closed by the supply and discharge port surface of the port block.

[0008] As mentioned above, when the cylinder port moves from being connected to the high-pressure second port to being closed by the supply and discharge port surface, the area of ​​communication between the cylinder port and the high-pressure second port decreases, which can cause the pressure in the cylinder chamber to rise rapidly. When this occurs, the noise from the axial piston device increases, so there is room for improvement.

[0009] The present invention aims to suppress noise in an axial piston device used, for example, as a hydraulic pump or hydraulic motor in a hydrostatic continuously variable transmission. [Means for solving the problem]

[0010] The axial piston device of the present invention comprises a port block, a cylinder block rotatable relative to the port block, and a swash plate. The port block has a supply / discharge port surface that the cylinder block contacts while rotating, a first port formed on one portion of the supply / discharge port surface with respect to a virtual line passing perpendicular to the rotation axis of the cylinder block, and a second port formed on the other portion of the supply / discharge port surface with respect to the virtual line. The cylinder block has a cylinder port surface in contact with the supply / discharge port surface, a plurality of cylinder chambers, a plurality of pistons provided inside the cylinder chambers so as to be reciprocally movable along the rotation axis, and a plurality of cylinder ports formed across the cylinder port surface and the cylinder chambers. The swash plate guides the pistons so that they are driven to reciprocate as the cylinder block is rotated, or the pistons are driven to reciprocate when hydraulic fluid is supplied to and discharged into the cylinder chambers, thereby causing the cylinder block to rotate. In the phase where the da-port faces the first port, the piston moves away from the cylinder port, allowing the hydraulic fluid to enter the cylinder chamber from the first port through the cylinder port. In the phase where the cylinder port faces the second port, the piston moves towards the cylinder port, allowing the hydraulic fluid in the cylinder chamber to exit the second port through the cylinder port. In at least one of the first dead center portion, which is one part between the first and second ports through which the dotted line passes, and the second dead center portion, which is the other part between the first and second ports through which the dotted line passes, a recess is formed on the supply and discharge port surface from one of the first and second ports located on the lower side in the rotational direction of the cylinder block toward the upper side in the rotational direction of the cylinder block. No recess is formed toward the lower side in the rotational direction of the cylinder block from the other of the first and second ports located on the upper side in the rotational direction of the cylinder block.

[0011] According to the present invention, in the case of a hydraulic pump, the cylinder block is rotationally driven by an external power source, and the piston is guided by the swash plate and reciprocated. According to the present invention, assuming a hydraulic motor, hydraulic fluid from the hydraulic pump is supplied to and discharged from the cylinder chamber, causing the piston to reciprocate by the swash plate, thereby rotating the cylinder block.

[0012] According to the present invention, in the phase when the cylinder port faces the first port, the piston moves away from the cylinder port, and the hydraulic fluid enters the cylinder chamber from the first port through the cylinder port. In the phase when the cylinder port faces the second port, the piston moves towards the cylinder port, and the hydraulic fluid in the cylinder chamber exits the cylinder chamber through the cylinder port to the second port.

[0013] According to the present invention, assuming a hydraulic pump, if a recess is provided at the first dead center where the cylinder port moves from the first port to the second port, even if the pressure in the cylinder chamber begins to drop rapidly when the cylinder port moves from the low-pressure first port to the high-pressure second port, the cylinder port will quickly reach the recess, and a state will be created where the cylinder port and the high-pressure second port are connected via the recess, thereby preventing a rapid drop in the pressure in the cylinder chamber. After this, the cylinder port is connected to the second port, the piston moves toward the side approaching the cylinder port, and the hydraulic fluid in the cylinder chamber exits through the cylinder port to the second port.

[0014] According to the present invention, assuming a hydraulic pump, if a recess is provided at the second dead center where the cylinder port moves from the second port to the first port, even if the pressure in the cylinder chamber begins to rise rapidly when the cylinder port moves from the high-pressure second port to the low-pressure first port, the cylinder port will quickly reach the recess, and a state will be created where the cylinder port and the low-pressure first port are connected via the recess, thereby preventing a rapid rise in the pressure in the cylinder chamber. After this, the cylinder port is connected to the first port, the piston moves away from the cylinder port, and the hydraulic fluid enters the cylinder chamber from the first port through the cylinder port.

[0015] According to the present invention, assuming a hydraulic motor, if a recess is provided at the first dead center where the cylinder port moves from the first port to the second port, even if the pressure in the cylinder chamber begins to rise rapidly when the cylinder port moves from the high-pressure first port to the low-pressure second port, the cylinder port will quickly reach the recess, and a state will be created where the cylinder port and the low-pressure second port are connected via the recess, thereby preventing a rapid rise in the pressure in the cylinder chamber. After this, the cylinder port is connected to the second port, the piston moves toward the side approaching the cylinder port, and the hydraulic fluid in the cylinder chamber exits through the cylinder port to the second port.

[0016] According to the present invention, assuming a hydraulic motor, if a recess is provided at the second dead center where the cylinder port moves from the second port to the first port, even if the pressure in the cylinder chamber begins to drop rapidly when the cylinder port moves from the low-pressure second port to the high-pressure first port, the cylinder port will immediately reach the recess, and a state will be created where the cylinder port and the high-pressure first port are connected via the recess, thereby preventing a rapid drop in the pressure in the cylinder chamber. After this, the cylinder port is connected to the first port, the piston moves away from the cylinder port, and the hydraulic fluid enters the cylinder chamber from the first port through the cylinder port.

[0017] According to the present invention, a recess is provided in at least one of the first dead center portion where the cylinder port moves from the first port to the second port and the second dead center portion where the cylinder port moves from the second port to the first port. This makes it possible to suppress at least one of the noises caused by a rapid decrease in pressure in the cylinder chamber and the noises caused by a rapid increase in pressure in the cylinder chamber, thereby reducing noise from the axial piston device.

[0018] In the present invention, it is preferable that the upper end portion in the rotational direction of the cylinder block in the concave portion is located on the virtual line, and the length along the rotational direction of the cylinder block in the concave portion is such that the cylinder port is connected to both the lower end portion in the rotational direction of the cylinder block in the other of the first port and the second port located on the upper side in the rotational direction of the cylinder block and the upper end portion in the rotational direction of the cylinder block in the concave portion. Furthermore, the axial piston device of the present invention comprises a port block, a cylinder block rotatable relative to the port block, and a swash plate, wherein the port block has a supply / discharge port surface that the cylinder block contacts while rotating, a first port formed on one portion of the supply / discharge port surface with respect to a virtual line passing perpendicular to the rotation axis of the cylinder block, and a second port formed on the other portion of the supply / discharge port surface with respect to the virtual line, wherein the cylinder block has a cylinder port surface in contact with the supply / discharge port surface, a plurality of cylinder chambers, a plurality of pistons provided inside the cylinder chambers so as to be reciprocally movable along the rotation axis, and a plurality of cylinder ports formed across the cylinder port surface and the cylinder chambers, wherein the swash plate guides the pistons so as the cylinder block is rotated, causing the pistons to reciprocate, or the cylinder block is rotated by supplying and discharging hydraulic fluid into the cylinder chambers causing the pistons to reciprocate, and in the phase where the cylinder port faces the first port, the piston moves forward The piston moves away from the cylinder port, allowing hydraulic fluid to enter the cylinder chamber from the first port through the cylinder port, and in the phase when the cylinder port faces the second port, the piston moves towards the cylinder port, allowing hydraulic fluid from the cylinder chamber to exit the cylinder chamber through the cylinder port at the second port. At least one of the first dead center portion, which is one part between the first and second ports through which the dotted line passes, and the second dead center portion, which is the other part between the first and second ports through which the dotted line passes, a recess is formed on the supply and discharge port surface from one of the first and second ports located on the lower side in the rotational direction of the cylinder block toward the upper side in the rotational direction of the cylinder block, and no recess is formed toward the lower side in the rotational direction of the cylinder block from the other of the first and second ports located on the upper side in the rotational direction of the cylinder block, and the upper end of the recess in the rotational direction of the cylinder block is located at least one of the first dead center portion and the second dead center portion.The length of the recess along the rotational direction of the cylinder block is set such that the cylinder port is connected to both the lower end of the other of the first and second ports, which are located on the upper side in the rotational direction of the cylinder block, and the upper end of the recess in the rotational direction of the cylinder block.

[0019] According to the present invention, assuming a hydraulic pump, when a concave portion is provided at the first dead center portion where the cylinder port moves from the first port to the second port, when the cylinder port moves from the low-pressure first port to the high-pressure second port, the cylinder port reaches the concave portion while still being connected to the first port, and the cylinder port and the high-pressure second port are connected via the concave portion, and a state occurs in which the cylinder port is connected to both the low-pressure first port and the high-pressure second port (concave portion). Thereby, a rapid decrease in the pressure of the cylinder chamber is further prevented, which is advantageous in terms of suppressing the noise of the axial piston device.

[0020] According to the present invention, assuming a hydraulic pump, when a concave portion is provided at the second dead center portion where the cylinder port moves from the second port to the first port, when the cylinder port moves from the high-pressure second port to the low-pressure first port, the cylinder port reaches the concave portion while still being connected to the second port, and the cylinder port and the low-pressure first port are connected via the concave portion, and a state occurs in which the cylinder port is connected to both the high-pressure second port and the low-pressure first port (concave portion). Thereby, a rapid increase in the pressure of the cylinder chamber is further prevented, which is advantageous in terms of suppressing the noise of the axial piston device.

[0021] According to the present invention, assuming a hydraulic motor, when a recess is provided in the first dead point portion where the cylinder port moves from the first port to the second port, when the cylinder port moves from the high-pressure first port to the low-pressure second port, the cylinder port reaches the recess while still being connected to the first port, and the cylinder port and the low-pressure second port are connected via the recess, resulting in a state where the cylinder port is connected to both the high-pressure first port and the low-pressure second port (recess). Thereby, a rapid increase in the pressure of the cylinder chamber is further prevented, which is advantageous in terms of suppressing the noise of the axial piston device.

[0022] According to the present invention, assuming a hydraulic motor, when a recess is provided in the second dead point portion where the cylinder port moves from the second port to the first port, when the cylinder port moves from the low-pressure second port to the high-pressure first port, the cylinder port reaches the recess while still being connected to the second port, and the cylinder port and the high-pressure first port are connected via the recess, resulting in a state where the cylinder port is connected to both the low-pressure second port and the high-pressure first port (recess). Thereby, a rapid decrease in the pressure of the cylinder chamber is further prevented, which is advantageous in terms of suppressing the noise of the axial piston device.

[0023] In the present invention, it is preferable that there are different arrangement pitches at the arrangement pitch, which is the interval between the virtual arrangement lines of adjacent cylinder ports, on the virtual arrangement line passing through the center in the rotational direction of the cylinder block in the cylinder port and the rotation axis.

[0024] In a hydraulic pump (hydraulic motor), when the cylinder port moves from the first port to the second port (or vice versa), the supply and discharge state of the hydraulic fluid switches between the cylinder port and the first and second hydraulic ports, which can cause vibrations in the cylinder chamber and piston due to pressure changes. If the phases of vibrations coincide in multiple cylinder chambers and pistons, the vibrations can be amplified, resulting in noise.

[0025] According to the present invention, in a cylinder block, the arrangement pitches of all cylinder ports are not the same, and there are arrangement pitches that are different from each other. This allows for a phase shift of the aforementioned vibrations in cylinder ports with different array pitches, thereby avoiding vibration amplification, which is advantageous in terms of suppressing noise in axial piston devices.

[0026] As mentioned above, if there are different arrangement pitches for the cylinder ports, one cylinder port may pass the first dead center (second dead center) section, and then the next cylinder port may reach the first dead center (second dead center) section earlier or later.

[0027] According to the present invention, by forming a recess at the first dead center portion (second dead center portion), even if the next cylinder port of one cylinder port reaches the first dead center portion (second dead center portion) earlier or later, it is easier to obtain a state in which the cylinder port and the high-pressure (low-pressure) second port are connected via the recess (a state in which the cylinder port and the low-pressure (high-pressure) first port are connected via the recess).

[0028] This makes it easier to achieve a state where the cylinder port and the high-pressure (low-pressure) second port are connected via a recess (a state where the cylinder port and the low-pressure (high-pressure) first port are connected via a recess), and it is advantageous in suppressing noise in axial piston devices because it avoids amplification of vibrations in the cylinder chamber and piston.

[0029] In the present invention, it is preferable that the arrangement pitch, which is the distance between the arrangement virtual lines of adjacent cylinder ports, is different from that of the arrangement virtual lines passing through the center of the cylinder block in the rotational direction and the rotation axis in the cylinder port.

[0030] In a hydraulic pump (hydraulic motor), when the cylinder port moves from the first port to the second port (or vice versa), the supply and discharge state of the hydraulic fluid switches between the cylinder port and the first and second hydraulic ports, which can cause vibrations in the cylinder chamber and piston due to pressure changes. If the phases of vibrations coincide in multiple cylinder chambers and pistons, the vibrations can be amplified, resulting in noise.

[0031] According to the present invention, in a cylinder block, the arrangement pitches of all cylinder ports are different from each other. This allows the phase of the aforementioned vibrations to be shifted in all cylinder ports, thus avoiding vibration amplification, which is advantageous in terms of suppressing noise in the axial piston mechanism.

[0032] As mentioned above, if the arrangement pitch of all cylinder ports is different from one another, one cylinder port may pass the first dead center (second dead center) section, and then the next cylinder port may reach the first dead center (second dead center) section earlier or later.

[0033] According to the present invention, by forming a recess at the first dead center portion (second dead center portion), even if the next cylinder port of one cylinder port reaches the first dead center portion (second dead center portion) earlier or later, it is easier to obtain a state in which the cylinder port and the high-pressure (low-pressure) second port are connected via the recess (a state in which the cylinder port and the low-pressure (high-pressure) first port are connected via the recess).

[0034] This makes it easier to achieve a state where the cylinder port and the high-pressure (low-pressure) second port are connected via a recess (a state where the cylinder port and the low-pressure (high-pressure) first port are connected via a recess), and it is advantageous in suppressing noise in axial piston devices because it avoids amplification of vibrations in the cylinder chamber and piston.

[0035] In the present invention, it is preferable that the recess is provided in both the first dead center portion and the second dead center portion.

[0036] According to the present invention, recesses are provided in both the first dead center portion and the second dead center portion, which is advantageous in terms of suppressing noise from both the rapid decrease in pressure in the cylinder chamber and the rapid increase in pressure in the cylinder chamber.

[0037] In the present invention, the cylinder block is rotated in one direction by an external power source, and the swash plate guides the piston so that the piston is driven to reciprocate as the cylinder block is rotated. Furthermore, it is preferable that the swash plate is capable of changing its orientation to a forward rotation position in which, when the cylinder port is facing the first port, the piston moves away from the cylinder port, and when the cylinder port is facing the second port, the piston moves towards the cylinder port; and a reverse rotation position in which, when the cylinder port is facing the first port, the piston moves towards the cylinder port, and when the cylinder port is facing the second port, the piston moves away from the cylinder port.

[0038] According to the present invention, the axial piston device is a hydraulic motor. As the cylinder block is rotationally driven by an external power source, the piston is guided by the swash plate and reciprocated. The swash plate can change its orientation to a forward rotation position and a reverse rotation position.

[0039] When the swash plate is operated to the forward position, in the phase where the cylinder port faces the first port, the piston moves away from the cylinder port, and the hydraulic fluid enters the cylinder chamber from the first port through the cylinder port. In the phase where the cylinder port faces the second port, the piston moves towards the cylinder port, and the hydraulic fluid in the cylinder chamber exits the cylinder chamber through the cylinder port to the second port.

[0040] When the swashplate is operated to the reverse position, in the phase where the cylinder port faces the first port, the piston moves toward the cylinder port, and the hydraulic fluid in the cylinder chamber exits through the cylinder port to the first port. In the phase where the cylinder port faces the second port, the piston moves toward the cylinder port, and the hydraulic fluid enters the cylinder chamber from the second port through the cylinder port.

[0041] According to the present invention, in the above configuration, the recess is provided in both the first dead center portion and the second dead center portion. When the swash plate is operated to the forward rotation position, it is possible to obtain both a state in which a rapid decrease in pressure in the cylinder chamber is prevented at the first dead center where the cylinder port moves from the first port to the second port, and a state in which a rapid increase in pressure in the cylinder chamber is prevented at the second dead center where the cylinder port moves from the second port to the first port. This prevents rapid drops and increases in cylinder chamber pressure, which is advantageous in terms of suppressing noise from the axial piston mechanism.

[0042] When the swash plate is operated to the reverse position, it is possible to achieve both a state in which a rapid increase in pressure in the cylinder chamber is prevented at the first dead center where the cylinder port moves from the first port to the second port, and a state in which a rapid decrease in pressure in the cylinder chamber is prevented at the second dead center where the cylinder port moves from the second port to the first port. This prevents rapid increases and decreases in cylinder chamber pressure, which is advantageous in terms of suppressing noise from the axial piston mechanism. [Brief explanation of the drawing]

[0043] [Figure 1] This is a longitudinal cross-sectional side view of a hydraulic pump. [Figure 2] This is a front view of the cylinder port surface of the cylinder block. [Figure 3] This is a front view of the port plate. [Figure 4] This is a cross-sectional view of the cylinder chamber and a front view of the port plate, showing the state in which the cylinder ports of phases #1 and #9 reach and connect to the first recess while remaining connected to the first port. [Figure 5] This is a cross-sectional view of the cylinder chamber and a front view of the port plate, showing the cylinder chamber centers at phases #1 and #9 positioned along the imaginary line of the first dead center. [Figure 6]This is a cross-sectional view of the cylinder chamber and a front view of the port plate, showing the cylinder chamber centers at phases #2, #4, #6, and #8 positioned along the imaginary line of the first dead center. [Figure 7] This is a cross-sectional view of the cylinder chamber and a front view of the port plate, showing the cylinder chamber centers at phases #3, #5, and #7 positioned along the imaginary line of the first dead center. [Modes for carrying out the invention]

[0044] Figures 1 to 7 show an example of an axial piston device, specifically a hydraulic pump for a hydrostatic continuously variable transmission (CVT) that includes a hydraulic pump and a hydraulic motor.

[0045] (Overall configuration of the hydraulic pump) As shown in Figure 1, the hydraulic pump has a drive shaft 1, a cylinder block 2, a cylinder chamber 6 and a piston 7, a port block 3, and a swash plate 4.

[0046] The drive shaft 1 is supported by passing through the port block 3 so as to be rotatable around the axis P1. The drive shaft 1 is rotated in one direction A1 (see Figures 2 and 3) by an external power source such as an engine (not shown) and an electric motor (not shown).

[0047] A circular port plate 15 (corresponding to the supply and discharge port surface) is attached to the port block 3, and the port block 3 is provided with first ports 11, 12, 13 and second ports 21, 22, 23 (see Figure 3).

[0048] The cylinder block 2 is connected to the spline portion 1a of the drive shaft 1. The cylinder block 2 has a cylinder chamber 6 and a piston 7. When the drive shaft 1 is rotated in one direction, the cylinder block 2 (cylinder chamber 6 and piston 7) is rotated together with the drive shaft 1 in one direction A1 (see Figure 2) around the axis P1 (corresponding to the axis of rotation).

[0049] The swash plate 4 is supported so that the drive shaft 1 passes through it, and the end of the piston 7 is in contact with the swash plate 4. When the cylinder block 2 is rotationally driven, the piston 7 reciprocates inside the cylinder chamber 6 due to the swash plate 4.

[0050] With the above configuration, the device is equipped with a port block 3, a cylinder block 2 that is rotatable relative to the port block 3, and a swash plate 4.

[0051] (Cylinder block configuration) As shown in Figures 1 and 2, nine cylinder chambers 6 are provided in the cylinder block 2 along the axis P1. If we assume a virtual circle C1 centered on the axis P1, the center B1 of the cylinder chamber 6 is located on the virtual circle C1.

[0052] A cylinder port surface 2a is formed at the end of the cylinder block 2, and oval-shaped cylinder ports 8 are provided across the cylinder port surface 2a of the cylinder block 2 and the cylinder chamber 6, corresponding to each of the cylinder chambers 6.

[0053] Considering the phases #1 to #9 (radial direction of the cylinder block 2 passing through the axis P1) where the center B1 of the cylinder chamber 6 is located around the axis P1 of the cylinder block 2, the array pitch D1, which is the interval between adjacent phases #1 to #9, is all the same.

[0054] A piston 7 is provided inside each of the cylinder chambers 6, and the piston 7 is capable of reciprocating along the axis P1. In each of the cylinder chambers 6, a spring 9 is provided extending from the end of the cylinder chamber 6 to the piston 7, and the piston 7 is biased by the spring 9 toward the side away from the cylinder port 8.

[0055] (Configuration of cylinder ports in a cylinder block) As shown in Figure 2, the cylinder port 8 is oval-shaped, positioned at the location of the virtual circle C1, and curved in an arc along the virtual circle C1. The length L1 of the cylinder port 8 along the rotational direction A1 (length along the virtual circle C1) is the same for all cylinder ports 8.

[0056] The relationship between the center F1 in the rotational direction A1 of the cylinder port 8 (the center along the virtual circle C1) and the center B1 of the cylinder chamber 6 is explained below. In phases #1 and #9, the center B1 of the cylinder chamber 6 and the center F1 of the cylinder port 8 coincide. Therefore, assuming the virtual alignment lines G1 and G9 passing through the center F1 of the cylinder port 8 and the axis P1, phase #1 coincides with the virtual alignment line G1, and phase #9 coincides with the virtual alignment line G9.

[0057] In phases #2, #4, #6, and #8, if we assume that the virtual lines G2, G4, G6, and G8 pass through the center F1 of the cylinder port 8 and the axis P1, then the virtual lines G2, G4, G6, and G8 are located on the leading (downward) side of the rotation direction A1 with respect to phases #2, #4, #6, and #8 by a phase angle difference of θ2, θ4, θ6, and θ8.

[0058] In phases #3, #5, and #7, assuming that the virtual lines G3, G5, and G7 pass through the center F1 of the cylinder port 8 and the axis P1, these virtual lines G3, G5, and G7 are located on the lag side (upward side) of the rotation direction A1 with respect to phases #3, #5, and #7 by phase angle differences θ3, θ5, and θ7.

[0059] All of the phase angle differences θ2 to θ8 are set to different values ​​from each other. As a result, all of the array pitches E1 to E9 are different from each other: array pitch E1, which is the spacing between array virtual lines G1 and G2; array pitch E2, which is the spacing between array virtual lines G2 and G3; array pitch E3, which is the spacing between array virtual lines G3 and G4; array pitch E4, which is the spacing between array virtual lines G4 and G5; array pitch E5, which is the spacing between array virtual lines G5 and G6; array pitch E6, which is the spacing between array virtual lines G6 and G7; array pitch E7, which is the spacing between array virtual lines G7 and G8; array pitch E8, which is the spacing between array virtual lines G8 and G9; and array pitch E9, which is the spacing between array virtual lines G9 and G1.

[0060] With the above configuration, in the arrangement of virtual lines G1 to G9 that pass through the center B1 and axis P1 (rotation axis) of the cylinder block 2 in the rotation direction A1 of the cylinder port 8, all of the arrangement pitches E1 to E9, which are the intervals between the arrangement of virtual lines G1 to G9 of adjacent cylinder ports 8, are different from each other.

[0061] (Port block configuration) As shown in Figure 3, in the port plate 15 attached to the port block 3, if we assume a virtual line H1 passing perpendicular to the axis P1 (in the diametrical direction centered on the axis P1), then three first ports 11, 12, and 13 are formed on one side (left side in Figure 3) of the port plate 15 with respect to the virtual line H1. Three second ports 21, 22, and 23 are formed on the other side (right side in Figure 3) of the port plate 15 with respect to the virtual line H1.

[0062] The first ports 11, 12, 13 and the second ports 21, 22, 23 are oval-shaped, located at the position of the virtual circle C1, and are curved in an arc along the virtual circle C1 (see Figure 2). The first ports 11, 12, 13 and the second ports 21, 22, 23 are point-symmetric with respect to the axis P1.

[0063] In the port plate 15, the portion between the first port 13 and the second port 21 through which the virtual line H1 passes is defined as the first dead point portion 16, and the portion between the first port 11 and the second port 23 through which the virtual line H1 passes is defined as the second dead point portion 17.

[0064] In the first dead center portion 16 of the port plate 15, a first recess 18 (corresponding to a recess) with a V-shaped cross-section is formed extending from the second port 21 (corresponding to one of the first port 13 and the second port 21 located on the lower side in the rotation direction A1 of the cylinder block 2) toward the first port 13 (corresponding to the other of the first port 13 and the second port 21 located on the upper side in the rotation direction A1 of the cylinder block 2).

[0065] In the second dead center portion 17 of the port plate 15, a second recess 19 (corresponding to a recess) with a V-shaped cross-section is formed extending from the first port 11 (corresponding to one of the first port 11 and the second port 23 located on the lower side in the rotation direction A1 of the cylinder block 2) toward the second port 23 (corresponding to the other of the first port 11 and the second port 23 located on the upper side in the rotation direction A1 of the cylinder block 2).

[0066] The first recess 18 and the second recess 19 are located at the position of the virtual circle C1 and are provided along the virtual circle C1. The ends of the first recess 18 and the second recess 19 are located on the virtual line H1. The lengths L2 of the first recess 18 and the second recess 19 along the rotational direction A1 (length along the virtual circle C1) are the same.

[0067] The length L3 (length along virtual circle C1) along the rotational direction A1 between the end of the first recess 18 and the first port 13 is the same as the length L3 (length along virtual circle C1) along the rotational direction A1 between the end of the second recess 19 and the second port 23. The length L3 is shorter than the length L1 of the cylinder port 8 (see Figure 2).

[0068] As a result, the first recess 18, first port 13, and second port 21 of the first dead center portion 16, and the second recess 19, first port 11, and second port 23 of the second dead center portion 17 are point-symmetric with respect to the axis P1.

[0069] As described above, when the cylinder block 2 is rotationally driven, the cylinder port surface 2a of the cylinder block 2 is rotated in the rotational direction A1 while in contact with the port plate 15, and the cylinder port 8 of the cylinder block 2 is connected to the first ports 11, 12, 13 and the second ports 21, 22, 23 of the port plate 15 (port block 3).

[0070] (Construction of the slanted plate) As shown in Figure 1, the trunnion shaft 5 is supported so as to be able to swing around an axis P2 perpendicular to the axis P1, and the swash plate 4 is connected to the trunnion shaft 5. By operating the trunnion shaft 5 from the outside, the swash plate 4 changes its attitude between the neutral position N, the forward rotation maximum speed position FM, and the reverse rotation maximum speed position RM. The position between the neutral position N and the forward rotation maximum speed position FM, and the forward rotation maximum speed position FM itself, is the forward rotation position F. The position between the neutral position N and the reverse rotation maximum speed position RM, and the reverse rotation maximum speed position RM itself, is the reverse rotation position R.

[0071] The ring member 10 is slidably mounted on the swash plate 4 around the axis P1, and each end of the piston 7 is connected to the ring member 10 via a universal joint 14. When the cylinder block 2 (cylinder chamber 6 and piston 7) is rotationally driven, the ring member 10 is rotationally driven together with the cylinder block 2 (cylinder chamber 6 and piston 7) and slides relative to the swash plate 4 around the axis P1.

[0072] When the cylinder block 2 is rotationally driven, the swash plate 4 and spring 9 cause the piston 7 to reciprocate along the axis P1 inside the cylinder chamber 6 as described below.

[0073] (The swashplate is operated to the forward rotation position.) The state shown in Figure 1 is when the swashplate 4 is operated to the position FM, which is the maximum forward rotation speed position at the forward rotation position F.

[0074] When the swash plate 4 is operated to the forward rotation maximum speed position FM, as shown in Figure 3, when the cylinder chamber 6 and piston 7 are positioned on the imaginary line H1 of the second dead center portion 17 relative to the port block 3 (port plate 15), the piston 7 is positioned on the side closest to the cylinder port 8 (see the lower piston 7 in Figure 1).

[0075] As shown in Figures 1, 2, and 3, when the cylinder block 2 is rotated in the rotational direction A1, the cylinder chamber 6 and piston 7 move along the first ports 11, 12, and 13 from the imaginary line H1 of the second dead center portion 17, and the piston 7 moves toward the side away from the cylinder port 8.

[0076] During this time, low-pressure hydraulic fluid enters the cylinder chamber 6 from the first ports 11, 12, and 13 through the cylinder port 8, and the first ports 11, 12, and 13 become low-pressure. When the cylinder chamber 6 and piston 7 are located on the imaginary line H1 of the first dead center portion 16, piston 7 is located on the side furthest from the cylinder port 8 (see the upper piston 7 in Figure 1).

[0077] As the cylinder block 2 is rotated in the rotational direction A1, the cylinder chamber 6 and piston 7 move along the second ports 21, 22, and 23 from the imaginary line H1 of the first dead center portion 16, and the piston 7 moves toward the side approaching the cylinder port 8. During this time, the high-pressure hydraulic fluid from the cylinder chamber 6 exits through the cylinder port 8 to the second ports 21, 22, and 23, and the second ports 21, 22, and 23 become high-pressure.

[0078] When the swash plate 4 is operated to a position between the neutral position N and the maximum forward speed position FM in the forward rotation position F, if the cylinder chamber 6 and piston 7 are located on the imaginary line H1 of the second dead center section 17, the piston 7 will be located further from the cylinder port 8 than the position shown for the lower piston 7 in Figure 1. If the cylinder chamber 6 and piston 7 are located on the imaginary line H1 of the first dead center section 16, the piston 7 will be located closer to the cylinder port 8 than the position shown for the upper piston 7 in Figure 1.

[0079] (The swashplate is operated to the reverse position.) Considering the state shown in Figure 1, let's assume the swashplate 4 is operated to the reverse maximum speed position RM at the reverse position R.

[0080] As shown in Figures 1, 2, and 3, when the swash plate 4 is operated to the reverse maximum speed position RM, and the cylinder chamber 6 and piston 7 are positioned on the imaginary line H1 of the first dead center portion 16 relative to the port block 3 (port plate 15), the piston 7 is positioned on the side closest to the cylinder port 8 (see the lower piston 7 in Figure 1).

[0081] As the cylinder block 2 is rotated in the rotational direction A1, the cylinder chamber 6 and piston 7 move along the second ports 21, 22, and 23 from the imaginary line H1 of the first dead center portion 16, and the piston 7 moves toward the side away from the cylinder port 8.

[0082] During this time, low-pressure hydraulic fluid enters the cylinder chamber 6 from the second ports 21, 22, and 23 through the cylinder port 8, and the second ports 21, 22, and 23 become low-pressure. When the cylinder chamber 6 and piston 7 are located on the imaginary line H1 of the second dead center portion 17, piston 7 is located on the side furthest from the cylinder port 8 (see the upper piston 7 in Figure 1).

[0083] As the cylinder block 2 is rotated in the rotational direction A1, the cylinder chamber 6 and piston 7 move along the first ports 11, 12, and 13 from the imaginary line H1 of the second dead center portion 17, and the piston 7 moves toward the side approaching the cylinder port 8. During this time, the high-pressure hydraulic fluid from the cylinder chamber 6 exits through the cylinder port 8 to the first ports 11, 12, and 13, and the first ports 11, 12, and 13 become high-pressure.

[0084] When the swash plate 4 is operated to a position between the neutral position N and the reverse maximum speed position RM in the reverse position R, if the cylinder chamber 6 and piston 7 are located on the imaginary line H1 of the first dead center section 16, the piston 7 will be located further from the cylinder port 8 than the position shown for the lower piston 7 in Figure 1. If the cylinder chamber 6 and piston 7 are located on the imaginary line H1 of the second dead center section 17, the piston 7 will be located closer to the cylinder port 8 than the position shown for the upper piston 7 in Figure 1.

[0085] (Correspondence between cylinder block and port block and claims) With the above configuration, as shown in Figures 1, 2, and 3, the port block 3 has a port plate 15 (supply and discharge port surface) that the cylinder block 2 contacts while rotating, first ports 11, 12, and 13 formed on one portion of the port plate 15 (supply and discharge port surface) with respect to a virtual line H1 that passes perpendicular to the axis P1 (rotation axis) of the cylinder block 2, and second ports 21, 22, and 23 formed on the other portion of the port plate 15 (supply and discharge port surface) with respect to the virtual line H1.

[0086] The cylinder block 2 has a cylinder port surface 2a that contacts the port plate 15 (supply and discharge port surface), a plurality of cylinder chambers 6, a plurality of pistons 7 provided inside the cylinder chambers 6 so as to be able to reciprocate along the axis P1 (rotation axis), and a plurality of cylinder ports 8 formed across the cylinder port surface 2a and the cylinder chambers 6. The cylinder block 2 is rotated in one direction by an external power source.

[0087] Port block 3 is provided with the following configuration in at least one of the following two parts: a first dead point portion 16, which is one part between the first ports 11, 13 and the second ports 21, 23 through which virtual line H1 passes, and a second dead point portion 17, which is the other part between the first ports 11, 13 and the second ports 21, 23 through which virtual line H1 passes.

[0088] A first recess 18 (recess) is formed on the port plate 15 (supply and discharge port surface) extending from the second port 21 (one of the first ports 11, 13 and the second ports 21, 23), located on the lower side of the cylinder block 2 in the rotational direction A1, toward the upper side of the cylinder block 2 in the rotational direction A1.

[0089] A second recess 19 (recess) is formed on the port plate 15 (supply and discharge port surface) extending from the first port 11 (one of the first ports 11, 13 and the second ports 21, 23) located on the lower side of the cylinder block 2 in the rotational direction A1, toward the upper side of the cylinder block 2 in the rotational direction A1.

[0090] (Correspondence between the swashplate and the claims) With the above configuration, as shown in Figures 1, 2, and 3, the swash plate 4 guides the piston 7 so that it is driven to reciprocate as the cylinder block 2 is rotated.

[0091] When the swash plate 4 is operated to the forward rotation position F, in the phase where the cylinder port 8 is facing the first ports 11, 12, and 13, the piston 7 moves away from the cylinder port 8, and the hydraulic fluid enters the cylinder chamber 6 from the first ports 11, 12, and 13 through the cylinder port 8. When cylinder port 8 is facing the second ports 21, 22, and 23, piston 7 moves toward the side approaching cylinder port 8, and the hydraulic fluid in cylinder chamber 6 passes through cylinder port 8 to exit the second ports 21, 22, and 23.

[0092] When the swash plate 4 is operated to the reverse position R, in the phase where the cylinder port 8 faces the first ports 11, 12, and 13, the piston 7 moves toward the side approaching the cylinder port 8, and the hydraulic fluid in the cylinder chamber 6 passes through the cylinder port 8 to the first ports 11, 12, and 13. When cylinder port 8 is facing the second ports 21, 22, and 23, piston 7 moves away from cylinder port 8, and hydraulic fluid enters cylinder chamber 6 from the second ports 21, 22, and 23 through cylinder port 8. The first recess 18 (recess) and the second recess 19 (recess) are provided in both the first dead center portion 16 and the second dead center portion 17.

[0093] (Relationship between cylinder port and first and second recesses) - 1 As shown in Figure 4, when the cylinder block 2 is rotated in the rotational direction A1 and the cylinder chamber 6 and piston 7 move from the first port 13 to the first dead center portion 16, the cylinder port 8 reaches the first recess 18 and becomes connected to the first recess 18 while remaining connected to the first port 13.

[0094] As a result, cylinder port 8 is connected to the first port 13 and also to the second port 21 via the first recess 18. Figure 4 shows the cylinder chamber 6 and piston 7 and cylinder port 8 (see Figure 2) for phases #1 and #9, but the state shown in Figure 4 also occurs for cylinder chamber 6 and piston 7 and cylinder port 8 for phases #2 to #8.

[0095] Similarly, when the cylinder block 2 is rotationally driven in rotational direction A1, and the cylinder chambers 6 and piston 7 in phases #1 to #9 move from the second port 23 to the second dead center portion 17 (see Figure 3), the cylinder port 8 remains connected to the second port 23 and also connected to the first port 11 via the second recess 19.

[0096] As mentioned above, this is based on the fact that the length L3 along the rotational direction A1 between the end of the first recess 18 and the first port 13 (length along the virtual circle C1) and the length L3 along the rotational direction A1 between the end of the second recess 19 and the first port 11 (length along the virtual circle C1) are the same (see Figure 3), and that length L3 is shorter than the length L1 of the cylinder port 8 (see Figure 2).

[0097] (Relationship between cylinder port and first and second recesses) - 2 With the above configuration, as shown in Figures 3 and 4, the length L2 in the first recess 18 (recess) along the rotation direction A1 of the cylinder block 2 is set to a length such that the cylinder port 8 is connected to both the first port 13 (the other of the first ports 11, 13 and the second ports 21, 23) located on the upper side in the rotation direction A1 of the cylinder block 2, and the first recess 18 (recess).

[0098] As shown in Figures 3 and 4, the length L2 in the second recess 19 (recess) along the rotational direction A1 of the cylinder block 2 is set to a length such that the cylinder port 8 is connected to both the second port 23 (the other of the first ports 11, 13 and the second ports 21, 23) located on the upper side in the rotational direction A1 of the cylinder block 2, and the second recess 19 (recess).

[0099] (Relationship between the cylinder port and the first and second recesses) - 3 Assume that the cylinder block 2 is rotated in the rotational direction A1 from the state shown in Figure 4, and that the center B1 (see Figure 2) of the cylinder chamber 6 with phases #1 and #9 is located on the imaginary line H1 of the first dead center portion 16, as shown in Figure 5.

[0100] In the state shown in Figure 5, the center F1 (see Figure 2) of the cylinder port 8 in phases #1 and #9 is located on the imaginary line H1 of the first dead center portion 16. The cylinder port 8 in phases #1 and #9 moves away from the first port 13, and the connection portion between the cylinder port 8 in phases #1 and #9 and the first recess 18 becomes larger.

[0101] Similarly, when the center B1 of the cylinder chamber 6 and the center F1 of the cylinder port 8 in phases #1 and #9 reach the imaginary line H1 of the second dead center portion 17 (see Figure 3), the cylinder port 8 in phases #1 and #9 moves away from the second port 23, and the connection portion between the cylinder port 8 in phases #1 and #9 and the second recess 19 (see Figure 3) becomes larger.

[0102] (Relationship between cylinder port and first and second recesses) - 4 Assume that the cylinder block 2 is rotated in the rotational direction A1 from the state shown in Figure 4, and that the center B1 (see Figure 2) of the cylinder chamber 6 at phases #2, #4, #6, and #8 is located on the imaginary line H1 of the first dead center portion 16, as shown in Figure 6.

[0103] In the state shown in Figure 6, the center F1 (see Figure 2) of the cylinder ports 8 with phases #2, #4, #6, and #8 is located on the leading (downward) side of the rotation direction A1 by a phase angle difference θ2, θ4, θ6, and θ8 from the imaginary line H1 of the first dead center portion 16. The cylinder ports 8 with phases #2, #4, #6, and #8 move away from the first port 13, and the connection portion between the cylinder ports 8 with phases #2, #4, #6, and #8 and the first recess 18 becomes larger.

[0104] Similarly, when the center B1 of the cylinder chamber 6 in phases #2, #4, #6, and #8 reaches the imaginary line H1 of the second dead center portion 17 (see Figure 3), the cylinder ports 8 in phases #2, #4, #6, and #8 move away from the second port 23, and the connection portion between the cylinder ports 8 in phases #2, #4, #6, and #8 and the second recess 19 (see Figure 3) becomes larger.

[0105] (Relationship between cylinder port and first and second recesses) - 5 Assume that the cylinder block 2 is rotated in the rotational direction A1 from the state shown in Figure 4, and that the center B1 (see Figure 2) of the cylinder chamber 6 with phases #3, #5, and #7 is located on the imaginary line H1 of the first dead center portion 16, as shown in Figure 7.

[0106] In the state shown in Figure 7, the center F1 (see Figure 2) of the cylinder ports 8 with phases #3, #5, and #7 is located on the lag side (upward side) of the rotation direction A1 by phase angle differences θ3, θ5, and θ7 from the imaginary line H1 of the first dead center portion 16. The cylinder ports 8 with phases #3, #5, and #7 move away from the first port 13, and the connection portion between the cylinder ports 8 with phases #3, #5, and #7 and the first recess 18 becomes larger.

[0107] Similarly, when the center B1 of the cylinder chamber 6 in phases #3, #5, and #7 reaches the imaginary line H1 of the second dead center portion 17 (see Figure 3), the cylinder port 8 in phases #3, #5, and #7 moves away from the second port 23, and the connection portion between the cylinder port 8 in phases #3, #5, and #7 and the second recess 19 (see Figure 3) becomes larger.

[0108] (First alternative embodiment of the invention) In Figures 1 to 7, if the hydraulic motor is a hydrostatic continuously variable transmission having a hydraulic pump and a hydraulic motor, the swash plate 4 is fixed in the forward rotation position F or the reverse rotation position R. The following describes the state in which the swash plate 4 is fixed in the forward rotation position F and high-pressure hydraulic fluid is supplied to the first ports 11, 12, and 13.

[0109] When the cylinder chamber 6 and piston 7 are positioned on the imaginary line H1 of the second dead center portion 17 relative to the port block 3 (port plate 15), the piston 7 is positioned on the side approaching the cylinder port 8 (see the lower piston 7 in Figure 1).

[0110] High-pressure hydraulic fluid enters the cylinder chamber 6 from the first ports 11, 12, and 13 through the cylinder port 8. The high-pressure hydraulic fluid causes the piston 7 to move away from the cylinder port 8, resulting in high pressure at the first ports 11, 12, and 13. As the piston 7 moves away from the cylinder port 8, the cylinder block 2 is rotated in the rotational direction A1 (see Figure 2), and power in the rotational direction A1 is output from the drive shaft 1.

[0111] As the cylinder chamber 6 and piston 7 move along the second ports 21, 22, and 23 from the imaginary line H1 of the first dead center portion 16, the piston 7 moves toward the side approaching the cylinder port 8. During this time, the low-pressure hydraulic fluid from the cylinder chamber 6 exits through the cylinder port 8 to the second ports 21, 22, and 23, and the second ports 21, 22, and 23 become low-pressure.

[0112] With the above configuration, the swash plate 4 causes the piston 7 to reciprocate as hydraulic fluid is supplied to and discharged from the cylinder chamber 6, thereby causing the cylinder block 2 to rotate.

[0113] (Second alternative embodiment of the invention) Figures 1 to 7 show a hydraulic motor for a hydrostatic continuously variable transmission having a hydraulic pump and a hydraulic motor. When the swash plate 4 is fixed in the reverse position R and high-pressure hydraulic fluid is supplied to the first ports 11, 12, and 13, a state opposite to the state described in the above-mentioned (First Alternative Embodiment of the Invention) occurs, as described below.

[0114] High-pressure hydraulic fluid enters the cylinder chamber 6 from the first ports 11, 12, and 13 through the cylinder port 8, and the high-pressure hydraulic fluid moves the piston 7 away from the cylinder port 8, causing the cylinder block 2 to rotate in the opposite direction to the rotation direction A1 (see Figure 2), and power in the opposite direction to the rotation direction A1 is output from the drive shaft 1.

[0115] As the cylinder chamber 6 and piston 7 move along the second ports 21, 22, and 23 from the imaginary line H1 of the second dead center portion 17, the piston 7 moves toward the cylinder port 8, and the low-pressure hydraulic fluid in the cylinder chamber 6 exits through the cylinder port 8 to the second ports 21, 22, and 23.

[0116] With the above configuration, the swash plate 4 causes the piston 7 to reciprocate as hydraulic fluid is supplied to and discharged from the cylinder chamber 6, thereby causing the cylinder block 2 to rotate.

[0117] (Third alternative form of the invention) In Figures 1 to 7, if the hydraulic motor is a hydrostatic continuously variable transmission having a hydraulic pump and a hydraulic motor, the swash plate 4 is fixed in the forward rotation position F or the reverse rotation position R. The following describes the state in which the swash plate 4 is fixed in the forward rotation position F and high-pressure hydraulic fluid is supplied to the second ports 21, 22, and 23.

[0118] When the cylinder chamber 6 and piston 7 are positioned on the imaginary line H1 of the second dead center portion 17 relative to the port block 3 (port plate 15), the piston 7 is positioned on the side approaching the cylinder port 8 (see the lower piston 7 in Figure 1).

[0119] High-pressure hydraulic fluid enters the cylinder chamber 6 from the second ports 21, 22, and 23 through the cylinder port 8. The high-pressure hydraulic fluid causes the piston 7 to move away from the cylinder port 8, resulting in high pressure at the second ports 21, 22, and 23. As the piston 7 moves away from the cylinder port 8, the cylinder block 2 is rotated in the opposite direction to the rotation direction A1 (see Figure 2), and power in the opposite direction to the rotation direction A1 is output from the drive shaft 1.

[0120] As the cylinder chamber 6 and piston 7 move along the first ports 11, 12, and 13 from the imaginary line H1 of the first dead center portion 16, the piston 7 moves toward the cylinder port 8. During this time, the low-pressure hydraulic fluid from the cylinder chamber 6 exits through the cylinder port 8 to the first ports 11, 12, and 13, resulting in low pressure at the first ports 11, 12, and 13.

[0121] With the above configuration, the swash plate 4 causes the piston 7 to reciprocate as hydraulic fluid is supplied to and discharged from the cylinder chamber 6, thereby causing the cylinder block 2 to rotate.

[0122] (Fourth alternative embodiment of the invention) Figures 1 to 7 show the hydraulic motor of a hydrostatic continuously variable transmission having a hydraulic pump and a hydraulic motor. When the swash plate 4 is fixed in the reverse position R and high-pressure hydraulic fluid is supplied to the second ports 21, 22, and 23, a state opposite to the state described in the above-mentioned (third alternative embodiment of the invention) occurs, as described below.

[0123] High-pressure hydraulic fluid enters the cylinder chamber 6 through the second ports 21, 22, and 23 and the cylinder port 8. The high-pressure hydraulic fluid causes the piston 7 to move away from the cylinder port 8, and the cylinder block 2 is rotated in the rotational direction A1 (see Figure 2), and power in the rotational direction A1 is output from the drive shaft 1.

[0124] As the cylinder chamber 6 and piston 7 move along the first ports 11, 12, and 13 from the imaginary line H1 of the second dead center portion 17, the piston 7 moves toward the cylinder port 8, and the low-pressure hydraulic fluid from the cylinder chamber 6 exits through the cylinder port 8 to the first ports 11, 12, and 13.

[0125] With the above configuration, the swash plate 4 causes the piston 7 to reciprocate as hydraulic fluid is supplied to and discharged from the cylinder chamber 6, thereby causing the cylinder block 2 to rotate.

[0126] (Fifth alternative embodiment of the invention) In the cylinder block 2 shown in Figure 2, the centers B1 of all cylinder chambers 6 and the centers F1 of the cylinder ports 8 may be aligned, and the phases #1 to #9 may be aligned with the arrangement of virtual lines G1 to G9 of all cylinder ports 8. With this configuration, the arrangement pitches E1 to E9 will all be the same value.

[0127] (Sixth alternative embodiment of the invention) In the cylinder block 2 shown in Figure 2, the array pitches E1 to E9 may be set as described below.

[0128] Array pitches E1 to E7 are set to the same value. Array pitches E8 and E9 are set to different values, and are also set to different values ​​from array pitches E1 to E7. Array pitches E1 to E5 are set to the same value. Array pitches E6 to E9 are set to the same value, but are different from array pitches E1 to E5.

[0129] The array pitches E1, E3, E5, E7, and E9 are set to the same value. The array pitches E2, E4, E6, and E8 are set to the same value, and are also set to a different value from the array pitches E1, E3, E5, E7, and E9.

[0130] Array pitches E1 to E3 are set to the same value. Array pitches E4 to E6 are set to the same value. Array pitches E7 to E9 are set to the same value. Array pitches E1 to E3, E4 to E6, and E7 to E9 are set to different values.

[0131] With the above configuration, in the arrangement of virtual lines G1 to G9 that pass through the center F1 and axis P1 (rotation axis) of the cylinder block 2 in the rotation direction A1 of the cylinder port 8, there exist arrangement pitches E1 to E9 that are different from each other, which are the spacing between the arrangement of virtual lines G1 to G9 of adjacent cylinder ports 8.

[0132] (Seventh alternative embodiment of the invention) In the port block 3 (port plate 15), a first recess 18 may be provided, and the second recess 19 may be omitted. In the port block 3 (port plate 15), a second recess 19 may be provided, and the first recess 18 may be eliminated.

[0133] (Eighth alternative form of the invention) In the configuration shown in Figure 3, if an extension line is drawn from the first recess 18 along the longitudinal direction of the first recess 18 toward the right (see virtual circle C1), the virtual line reaches (intersects) the first port 13. In this case, the shape of the first recess 18 may be set so that the extension line from the first recess 18 does not intersect the first port 13.

[0134] (Ninth alternative embodiment of the invention) In the configuration shown in Figure 3, if an extension line is drawn from the second recess 19 along its longitudinal direction to the right (see virtual circle C1), the virtual line reaches (intersects) the second port 23. In this case, the shape of the second recess 19 may be set so that the extension line from the second recess 19 does not intersect the second port 23.

[0135] (Tenth alternative embodiment of the invention) In the cylinder block 2, eight cylinder chambers 6 and pistons 7 may be provided, or seven or six cylinder chambers 6 and pistons 7 may be provided. In the cylinder block 2, there may be 10 cylinder chambers 6 and pistons 7, or 11 or 12 cylinder chambers 6 and pistons 7. [Industrial applicability]

[0136] The present invention can be applied, for example, to an axial piston device used as a hydraulic pump or hydraulic motor in a hydrostatic continuously variable transmission. [Explanation of symbols]

[0137] 2 Cylinder Blocks 3 Port Block 4 Swash plate 6 Cylinder chamber 7 pistons 8 Cylinder Ports 11 Port 1 12 Port 1 13 Port 1 15. Port plate (supply and exhaust port surface) 16 1st dead center part 17 2nd dead center part 18. First recess (recess) 19. Second recess (recess) 21 Port 2 22 Port 2 23 Port 2 A1 Rotation direction E1~E9 array pitch F Forward rotation position F1 center G1~G9 Array Virtual Lines H1 virtual line L2 Length P1 Axis (Rotation axis) R Reversal Position

Claims

1. The system includes a port block, a cylinder block rotatable relative to the port block, and a swash plate. The port block has a supply and discharge port surface that the cylinder block contacts while rotating, a first port formed on one portion of the supply and discharge port surface with respect to a virtual line passing perpendicular to the rotation axis of the cylinder block, and a second port formed on the other portion of the supply and discharge port surface with respect to the virtual line. The cylinder block has a cylinder port surface in contact with the supply and discharge port surface, a plurality of cylinder chambers, a plurality of pistons provided inside the cylinder chambers so as to be reciprocally movable along the rotation axis, and a plurality of cylinder ports formed across the cylinder port surface and the cylinder chambers. The swash plate guides the piston so that it is driven to reciprocate as the cylinder block is rotated, or the piston is driven to reciprocate as hydraulic fluid is supplied to and discharged from the cylinder chamber, thereby causing the cylinder block to rotate. In the phase where the cylinder port faces the first port, the piston moves away from the cylinder port, and the hydraulic fluid enters the cylinder chamber from the first port through the cylinder port. When the cylinder port is facing the second port, the piston moves toward the cylinder port so that the hydraulic fluid in the cylinder chamber passes through the cylinder port and exits to the second port. In at least one of the first dead point portion, which is one part between the first port and the second port through which the virtual line passes, and the second dead point portion, which is the other part between the first port and the second port through which the virtual line passes, A recess is formed on the supply and discharge port surface from one of the first and second ports located on the lower side in the rotational direction of the cylinder block toward the upper side in the rotational direction of the cylinder block, and no recess is formed from the other of the first and second ports located on the upper side in the rotational direction of the cylinder block toward the lower side in the rotational direction of the cylinder block. An axial piston device in which the upper end of the cylinder block in the rotational direction in the recess is located at least one of the first dead center portion and the second dead center portion, and the length of the recess along the rotational direction of the cylinder block is set to such a length that the cylinder port is connected to both the lower end of the other of the first and second ports located on the upper side in the rotational direction of the cylinder block and the upper end of the recess in the rotational direction of the cylinder block.

2. The axial piston device according to claim 1, wherein, in the arrangement of virtual lines passing through the center of the cylinder block in the rotational direction and the rotation axis in the cylinder port, the arrangement pitch, which is the distance between the arrangement of virtual lines of adjacent cylinder ports, is different from that of each other.

3. The axial piston device according to claim 1, wherein in the arrangement of virtual lines passing through the center of the cylinder block in the rotational direction and the axis of rotation in the cylinder port, all of the arrangement pitches, which are the intervals between the arrangement of virtual lines of adjacent cylinder ports, are different from each other.

4. The axial piston device according to claim 1, wherein the recess is provided in both the first dead center portion and the second dead center portion.

5. The cylinder block is driven to rotate in one direction by an external power source. The swash plate guides the piston so that it is driven to reciprocate as the cylinder block is rotated, and The axial piston device according to claim 4, wherein the swash plate is capable of changing its orientation to a forward rotation position in which, when the cylinder port is facing the first port, the piston moves away from the cylinder port and when the cylinder port is facing the second port, the piston moves towards the cylinder port; and a reverse rotation position in which, when the cylinder port is facing the first port, the piston moves towards the cylinder port and when the cylinder port is facing the second port, the piston moves away from the cylinder port.

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