LIQUID-PRESSURE ROTATING DEVICE

Abstract

A cylinder block including plurality of piston chambers formed at intervals in circumferential direction; plurality of pistons fitted in respective piston chambers movable in expanding and contracting directions to reciprocate in the expanding and contracting directions; a valve plate in contact with the cylinder block rear end surface and including first and second ports communicating with piston chambers. A portion of each ports is close to a top dead center switching land formed between first and second ports as a portion having a narrow opening width in a rotation radial direction of the cylinder block. An auxiliary port is formed at the valve plate switching land. Auxiliary port pressure is maintained lower than pressure of a side port that is the first or second port. When the piston chamber lacks communication with the side port (first or second port), the piston chamber and auxiliary port communicate with each other.

Description

TECHNICAL FIELD

The present invention relates to a liquid-pressure rotating device that can be used as a liquid-pressure motor or a liquid-pressure pump.

BACKGROUND ART

One example of a valve plate provided in a conventional liquid-pressure motor is shown in FIG. 9 (see PTL 1, for example). Main ports 2 and 3 are formed on a valve plate 1. Each of the main ports 2 and 3 is formed in a circular-arc shape extending along a route of a rotational movement of a cylinder port (not shown), and an opening width of each of the main ports 2 and 3 in a radial direction is a constant size W4.

Currently, high-pressure operating oil in the cylinder port (piston chamber) closed by the valve plate 1 is leaking through a sealed region between the valve plate 1 and a cylinder block, and a reduction in this leak amount is required.

CITATION LIST

Patent Literature

PTL 1: Japanese Laid-Open Patent Application Publication No. 45-39126

SUMMARY OF INVENTION

Technical Problem

It may be considered that to reduce the amount of operating oil leaking through the main ports, the opening width W4 of each of the main ports 2 and 3 is reduced. However, in this case, pressure loss of the operating oil flowing through each of the main ports 2 and 3 increases, and this causes a problem that mechanical efficiency of the liquid-pressure motor decreases.

The present invention was made to solve the above problem, and an object of the present invention is to provide a liquid-pressure rotating device capable of: reducing the amount of high-pressure operating oil leaking from a first or second port through a sealed region between a cylinder block and a valve plate; and suppressing an increase in pressure loss of operating oil flowing through each of the first and second ports.

Solution to Problem

A liquid-pressure rotating device according to the present invention includes: a cylinder block provided rotatably and including a plurality of piston chambers formed at intervals in a circumferential direction; a plurality of pistons fitted in the respective piston chambers so as to be movable in an expanding direction and a contracting direction and configured to reciprocate in the expanding direction and the contracting direction; and a valve plate provided in contact with the cylinder block and including a first port, a second port, and a switching land formed between the first port and the second port, the first and second ports communicating with the piston chambers, wherein: a portion of at least one of the first and second ports of the valve plate which portion is located close to the switching land is formed as a narrow portion having a narrow opening width in a radial direction; an auxiliary port is formed at the switching land of the valve plate; pressure of the auxiliary port is maintained lower than pressure of a high pressure side port that is any one of the first and second ports; and when the piston chamber does not communicate with the high pressure side port that is the first or second port, the piston chamber and the auxiliary port communicate with each other.

In the liquid-pressure rotating device according to the present invention, the portions of the first and second ports which portions are located close to the switching land are formed as the narrow portions each having the narrow opening width in the radial direction of the rotation of the cylinder block. Therefore, a seal area between the cylinder block and the valve plate can be increased by the narrow portions. The amount of high-pressure operating liquid leaking from the piston chamber through the first or second port can be reduced by a sealed region corresponding to the increased seal area.

The flow rate (the change amount of the volume of the piston chamber per unit rotation) of the operating liquid flowing through the portion of each of the first and second ports which portion is located close to the switching land is lower than the flow rate (the change amount of the volume of the piston chamber per unit rotation) of the operating liquid flowing through a portion of each of the first and second ports which portion is located far from the switching land. Therefore, even though the narrow portions are formed at the above portions, the pressure loss based on the flow of the operating liquid can be prevented from increasing to such a degree that the influence of the pressure loss is apparent. The reason why the flow rate of the operating liquid flowing through the portion close to the switching land is low is because the movement speed of the piston in the expanding and contracting directions becomes slow as the piston gets close to the switching land.

The narrow portions are not formed at the portions of the first and second ports which portions are located far from the switching land. Therefore, the pressure loss based on the flow of the operating liquid flowing through the far portions other than the narrow portions does not increase.

Further, when the piston chamber performs a rotational movement at the dead center and the vicinity of the dead center without communicating with the high pressure side port that is the first or second port, the high-pressure operating liquid in the piston chamber can be discharged through the auxiliary port. To be specific, the pressure of the operating liquid in the piston chamber at the dead center or the vicinity of the dead center which pressure contributes little to the rotation of the cylinder block and generates high resistance force against the rotation can be reduced, and the mechanical efficiency of the liquid-pressure rotating device can be improved.

The liquid-pressure rotating device according to the present invention may be configured such that the narrow portion is formed in an angle range from a position of a dead center to a position of not more than 45° in the circumferential direction.

By forming the narrow portions as above, the amount of high-pressure operating liquid leaking from the first or second port through the sealed region between the cylinder block and the valve plate can be effectively reduced, and the increase in the pressure loss by the flow of the operating liquid at the narrow portions can be effectively suppressed. To be specific, in a case where the rotation angle of the piston when the piston is located at the dead center is regarded as 0°, and the rotation angle of the piston which has moved in accordance with the rotation of the cylinder block is represented by θ, the movement speed of the piston in the expanding and contracting directions can be calculated as a value which changes based on a sine function in which a vertical axis denotes the movement speed of the piston in the expanding and contracting directions, and a horizontal axis denotes the rotation angle of the piston. The movement speed of the piston at the angle position where the rotation angle θ is 45° is about 70% of the maximum movement speed (the movement speed of the piston becomes the maximum movement speed when the piston is located at the angle position where the rotation angle θ is 90°. The flow rate of the operating liquid based on the movement of the piston also becomes about 70% of the maximum flow rate. Therefore, the opening width of the narrow portion in the radial direction can be set to about 70% of the opening width of the portion other than the narrow portion of each of the first and second ports, and the sealed region having an appropriate width can be formed.

The liquid-pressure rotating device according to the present invention may be configured such that: openings of the piston chambers which openings face the valve plate serve as cylinder ports; and the opening width of the narrow portion in the radial direction decreases as the narrow portion extends toward the dead center.

With this, when a bridge portion between the cylinder ports is located at the narrow portion by the rotation of the cylinder block, the seal width between the cylinder block and the valve plate in the circumferential direction becomes large. Therefore, the increase in the pressure loss based on the flow of the operating liquid at the narrow portion can be effectively suppressed while reducing the amount of high-pressure operating liquid leaking through between the cylinder block and the valve plate. To be specific, the flow rate of the operating liquid in the piston chamber decreases as the piston chamber moves toward the dead center (θ=0°) of the valve plate. Therefore, by reducing the opening width of the narrow portion in the radial direction as the narrow portion extends toward the dead center of the valve plate, the above effects can be obtained.

The liquid-pressure rotating device according to the present invention may be configured such that: openings of the piston chambers which openings face the valve plate serve as cylinder ports; each of the cylinder ports has a shape including a base portion and a convex portion projecting from the base portion outward or inward in the radial direction; the convex portion is formed such that when the piston chamber communicates with the auxiliary port through the cylinder port, only the convex portion communicates with the auxiliary port; and before and after the piston chamber communicates with the auxiliary port through the cylinder port, the base portion is located away from the auxiliary port by a sealing portion having a predetermined seal width in the radial direction.

With this, when the cylinder port performs the rotational movement at the dead center of the valve plate and the vicinity of the dead center, the base portion of the cylinder port can be located away from the auxiliary port by the sealing portion having the predetermined seal width in the radial direction. With this, in a state where the base portion of the cylinder port at the dead center of the valve plate or the vicinity of the dead center communicates with the high pressure side port that is the first or second port, the high-pressure operating liquid in the piston chamber can be prevented from flowing out through the base portion to the auxiliary port. With this, the communication between the base portion and the auxiliary port can be prevented, and the flow out of the operating liquid to the auxiliary port from a portion other than the convex portion can be prevented. Therefore, the volume efficiency improves.

The liquid-pressure rotating device according to the present invention may be configured such that the seal width is not less than 3 mm.

With this, in a state where the base portion of the cylinder port at the dead center of the valve plate or the vicinity of the dead center communicates with the high pressure side port that is the first or second port, the base portion is located away from the auxiliary port by the sealing portion having the seal width of 3 mm or more in the radial direction. Therefore, it is possible to effectively prevent a case where the high-pressure operating liquid in the piston chamber leaks from the sealing portion having the seal width of not less than 3 mm to flow into the auxiliary port.

Advantageous Effects of Invention

In the liquid-pressure rotating device according to the present invention, the portions of the first and second ports which portions are located close to the switching land are formed as the narrow portions, so that the amount of high-pressure operating liquid leaking from the first or second port through the sealed region between the rear end surface of the cylinder block and the valve plate can be reduced, and the increase in the pressure loss of the operating liquid flowing through the first and second ports can be suppressed. Thus, the overall efficiency of the liquid-pressure rotating device can be effectively improved.

The above object, other objects, features, and advantages of the present invention will be made clear by the following detailed explanation of preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view showing a valve plate of a liquid-pressure rotating device according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the liquid-pressure rotating device according to the embodiment.

FIG. 3 is an enlarged cross-sectional view showing a part of the liquid-pressure rotating device of FIG. 2.

FIG. 4 is an enlarged front view showing an upper half of the valve plate of FIG. 1.

FIG. 5 is an enlarged front view showing a lower half of the valve plate of FIG. 1.

FIG. 6 is a diagram showing a relation between an angle position θ of a piston chamber provided in the liquid-pressure rotating device of FIG. 2 and a stroke position of a piston.

FIG. 7 is a diagram showing a relation between the angle position θ of the piston chamber provided in the liquid-pressure rotating device of FIG. 2 and pressure of operating oil in the piston chamber.

FIG. 8A is a front view showing the valve plate of the liquid-pressure rotating device according to another embodiment of the present invention. FIG. 8B is an A-A enlarged cross-sectional view showing the valve plate of FIG. 8A.

FIG. 9 is a front view showing a valve plate of a conventional liquid motor.

DESCRIPTION OF EMBODIMENTS

Hereinafter, one embodiment of a liquid-pressure rotating device according to the present invention will be explained in reference to FIGS. 1 to 7. This embodiment will explain an example in which the liquid-pressure rotating device is used as an oil-pressure motor. It should be noted that the liquid-pressure rotating device can also be used as an oil-pressure pump.

An oil-pressure motor (liquid-pressure rotating device) 10 is a swash plate type oil-pressure motor configured to convert pressure of operating oil (operating liquid) into rotational force to output the rotational force. For example, the oil-pressure motor 10 is provided in an industrial machine, a construction machine, or the like and is used to drive the machine. As shown in FIG. 2, the oil-pressure motor 10 includes a valve plate 11, a cylinder block 12, a plurality of pistons 13, a plurality of shoes 14, and a swash plate 15, and these components are accommodated in a casing 16 included in the oil-pressure motor 10. The casing 16 includes a casing main body 16a, a front cover 16b, and a valve casing 16c.

The oil-pressure motor 10 further includes a rotating shaft 17. A first end portion 17a of the rotating shaft 17 is supported by the front cover 16b through a first bearing 19 so as to partially project from the front cover 16b and be rotatable around a rotation axis L10 that coincides with an axis of the rotating shaft 17. Further, a second end portion 17b of the rotating shaft 17 is supported by the valve casing 16c through a second bearing 20 so as to be rotatable around the rotation axis L10.

As shown in FIGS. 1 and 2, the valve plate 11 has a substantially circular plate shape and is provided to be fixed to the valve casing 16c in a state where the rotating shaft 17 is inserted through the valve plate 11. Two supply/discharge ports 21 and 22 (first and second ports) and two auxiliary ports 23 and 24 are formed on the valve plate 11. In the valve plate 11 shown in FIG. 1, the supply/discharge ports 21 and 22 are formed bilaterally symmetrically, and each of the supply/discharge ports 21 and 22 extends in a circumferential direction around the rotation axis L10 and is formed in a circular-arc shape. Each of the supply/discharge ports 21 and 22 includes tapered notches 90 at both respective circumferential-direction end portions thereof. Each of the notches 90 serves as a pressure change suppressing portion configured to reduce a gradient of a change in the pressure of the operating oil in a below-described piston chamber 27 and is formed so as to be able to reduce: a steep pressure change caused by switching between connection with the piston chamber 27 and disconnection from the piston chamber 27; and noise generated by the pressure change.

The upper auxiliary port 23 is provided at a top dead center switching land formed between one end portion of the supply/discharge port 21 and one end portion of the supply/discharge port 22, and the lower auxiliary port 24 is provided at a bottom dead center switching land formed between the other end portion of the supply/discharge port 21 and the other end portion of the supply/discharge port 22. To facilitate understanding, in FIGS. 2 and 3, the position of the supply/discharge port 21 is shifted in the circumferential direction from an actual position.

The cylinder block 12 is provided at the rotating shaft 17 such that: the rotating shaft 17 is inserted through a center of the cylinder block 12; and the cylinder block 12 and the rotating shaft 17 are prevented from rotating relative to each other by, for example, spline. Thus, the cylinder block 12 is provided rotatably around the rotation axis L10. A plurality of (nine, for example) piston chambers 27 are formed on the cylinder block 12 at substantially regular intervals in the circumferential direction. Further, cylinder ports 28 communicating with the respective piston chambers 27 are formed on the cylinder block 12 at substantially regular intervals in the circumferential direction. The piston chambers 27 are open at an axial rear end portion of the cylinder block 12 through the cylinder ports 28. A rear end surface 12a of the cylinder block 12 slidably contacts the valve plate 11, and a seal structure is realized between the cylinder block 12 and the valve plate 11. In accordance with a rotation angle position of the cylinder block 12, the cylinder ports 28 are connected to the left supply/discharge port 21, the right supply/discharge port 22, the upper auxiliary port 23, and the lower auxiliary port 24.

Each of the pistons 13 has a substantially columnar shape. Each of the pistons 13 is fitted and accommodated in the piston chamber 27 of the cylinder block 12 so as to realize a sealed state between the piston 13 and the piston chamber 27. Each of the pistons 13 forms an oil-pressure chamber 31. Each of the pistons 13 is provided so as to be movable in an expanding direction and contracting direction along an axis of the piston 13. The volumes of the oil-pressure chambers 31 change by the movements of the pistons 13. Each of outer surfaces of first end portions 33 of the pistons 13 is formed in a spherical shape, the first end portions 33 projecting from the piston chambers 27.

Each of the shoes 14 includes a flange portion 35 having a contact surface 34 which is located at one end portion of the shoe 14 and perpendicular to an axis of the shoe 14. Each of the shoes 14 forms a fitting concave space 36 that is open at the other end portion of the shoe 14. An inner surface of the shoe 14 which surface faces the fitting concave space 36 is formed in a spherical shape. The first end portion 33 of the piston 13 is fitted in the fitting concave space 36. The shoe 14 is coupled to the piston 13 so as to be rotatable around three orthogonal axes by using a center of each of the fitting concave space 36 and the first end portion 33 as a rotation center.

The swash plate 15 is provided close to a left end portion of the cylinder block 12 shown in FIG. 2 and includes a flat supporting surface 37 that receives and supports the contact surfaces of the shoes 14. The swash plate 15 is provided so as to be tiltable around a tilt axis L11 orthogonal to the rotation axis L10. The swash plate 15 is tilted around the tilt axis L11 by a servo mechanism 38 included in the oil-pressure motor 10. Thus, an angle of the supporting surface 37 with respect to the rotation axis L10 is changed.

The oil-pressure motor 10 shown in FIG. 2 further includes a retainer guide 40 and a pressing member 41. The retainer guide 40 is provided at the rotating shaft 17 such that: the rotating shaft 17 is coaxially inserted through the retainer guide 40; and the retainer guide 40 and the rotating shaft 17 are prevented from rotating relative to each other by, for example, spline. The retainer guide 40 includes a guide surface that is spherical about a point on the rotation axis L10, that is, an intersection point of the axes L10 and L11 in the present embodiment. The pressing member 41 is provided so as to be supported by the guide surface of the retainer guide 40 and rotatable around three orthogonal axes by using a center of a sphere including the guide surface, that is, the intersection point of the axes L10 and L11 as a rotation center. The pressing member 41 locks the flange portions 35 of the shoes 14 to press the shoes 14 against the supporting surface 37 of the swash plate 15. In this state, each of the shoes 14 is allowed to slightly move relative to the pressing member 41 in directions along the supporting surface 37 of the swash plate 15 and a rotational direction whose rotation center is the intersection point of the axes L10 and L11.

In the oil-pressure motor 10, a spring member (not shown) such as a compression coil spring is provided at the cylinder block 12, and spring force of the spring member is transferred to the retainer guide 40. With this, the retainer guide 40 guides and supports the pressing member 41 as described above to press the pressing member 41 against the swash plate 15. Then, the pressing member 41 presses the shoes 14 against the swash plate 15. Thus, the shoes 14 are prevented from being separated from and floating from the swash plate 15.

The oil-pressure motor 10 is configured such that when the cylinder block 12 rotates once, each of the pistons 13 reciprocates once. A reciprocating movement of the piston 13 includes a top dead center and a bottom dead center at angle positions corresponding to every 180° when the piston 13 performs the rotational movement about the rotation axis L10. Specifically, the top dead center and the bottom dead center are located at respective angle positions at each of which a virtual flat surface including the rotation axis L10 and vertical to the tilt axis L11 and the axis of the piston 13 coincide with each other.

The piston chamber 27 in which the piston 13 at the dead center or the vicinity of the dead center is fitted is connected to the auxiliary port 23 or 24 through the cylinder port 28. Specifically, when the piston chamber 27 is located in an angle range from an angle position when the piston 13 is located at the top dead center that is the most contracted position toward each of both sides in the circumferential direction by an angle θ1, the piston chamber 27 is connected to the upper auxiliary port 23. Further, when the piston chamber 27 is located in an angle range from an angle position when the piston 13 is located at the bottom dead center that is the most contracted position toward each of both sides in the circumferential direction by the angle θ1, the piston chamber 27 is connected to the lower auxiliary port 24. The angle θ1 is set to, for example, about 10°.

On the other hand, the piston chamber 27 in which the piston 13 at a position other than the dead center and the vicinity of the dead center is fitted is connected to the supply/discharge port 21 or 22 through the cylinder port 28. Specifically, when the cylinder block 12 is viewed from the first end portion 17a of the rotating shaft 17, and the cylinder block 12 rotates in a counterclockwise direction that is a direction shown by an arrow A1 in FIG. 1, the piston chamber 27 located at the angle position where the piston 13 is expanding except for the top dead center, the vicinity of the top dead center, the bottom dead center, and the vicinity of the bottom dead center is connected to the supply/discharge port 21. Further, when the cylinder block 12 is viewed from the first axial end portion 17a of the rotating shaft 17, and the cylinder block 12 rotates in a clockwise direction that is a direction shown by an arrow A2 in FIG. 1, the piston chamber 27 located at the angle position where the piston 13 is expanding except for one of the dead centers, the vicinity of the one dead center, the other dead center, and the vicinity of the other dead center is connected to the supply/discharge port 22.

Each of an angle range where the piston 13 moves in the expanding direction except for the dead centers and the vicinities of the dead centers and an angle range where the piston 13 moves in the contracting direction except for the dead centers and the vicinities of the dead centers is represented by {180−(2×θ1)}°. Therefore, each of these angle ranges is smaller than 180°. As above, each of the piston chambers 27 is connected to any one of the ports 21 to 24 in accordance with the angle position.

As shown in FIG. 2, the valve casing 16c of the oil-pressure motor 10 includes: a supply/discharge passage 51 communicating with the supply/discharge port 21 of the valve plate 11; and a supply/discharge passage (not shown) communicating with the supply/discharge port 22 of the valve plate 11. These supply/discharge passages communicate with an oil-pressure source, such as a pump, or a tank (both not shown) provided separately from the oil-pressure motor 10.

As shown in FIG. 1, in the present embodiment, the supply/discharge ports 21 and 22 of the valve plate 11 are formed symmetrically relative to the rotation axis L10 that is the axis of the valve plate 11, and the auxiliary ports 23 and 24 of the valve plate 11 are formed symmetrically relative to the rotation axis L10. Therefore, the oil-pressure motor 10 is rotatable in both normal and reverse directions. The operating oil is ejected from the oil-pressure source to be supplied through the supply/discharge passage 51 to the supply/discharge port 21 of the oil-pressure motor 10. Further, the operating oil is discharged from the supply/discharge port 22 of the oil-pressure motor 10 through the supply/discharge passage to an outside of the oil-pressure motor 10. With this, the piston in the piston chamber 27 connected to the supply/discharge port 21 expands. Thus, the cylinder block 12 rotates in the rotational direction A1, and the rotating shaft 17 also rotates in the rotational direction A1. For example, the rotation of the rotating shaft 17 can be output from the first end portion 17a to drive the other machine or the like in the same direction.

The supply/discharge port 21 serves as a first port to which the operating oil of high pressure, such as 35 MPa, which can drive the oil-pressure motor 10 is introduced from the oil-pressure source. The supply/discharge port 22 serves as a second port from which the operating oil discharged from the oil-pressure chamber 31 flows out, and the operating oil is discharged to the outside of the oil-pressure motor 10. Each of the auxiliary ports 23 and 24 serves as a third port. The pressure of the operating oil introduced to each of the auxiliary ports 23 and 24 is maintained higher than atmospheric pressure and lower than the pressure ejected from the oil-pressure source to the supply/discharge port 21 that is the high-pressure first port. For example, the pressure of the operating oil introduced to the auxiliary ports 23 and 24 is maintained not less than 0.01 MPa and not more than 2 MPa.

Further, the operating oil is ejected from the oil-pressure source to be supplied through the supply/discharge passage to the supply/discharge port 22 of the oil-pressure motor 10. Then, the operating oil is discharged from the supply/discharge port 21 of the oil-pressure motor 10 through the supply/discharge passage 51 to the outside of the oil-pressure motor 10. With this, the piston 13 in the piston chamber 27 connected to the supply/discharge port 22 expands. Thus, the cylinder block 12 rotates in the rotational direction A2 opposite to the rotational direction A1, and the rotating shaft 17 also rotates in the rotational direction A2. For example, the rotation of the rotating shaft 17 can be output from the first end portion 17a to drive the other machine or the like in the same direction.

In this case, the supply/discharge port 22 serves as the first port to which the operating oil of high pressure which can drive the oil-pressure motor 10 is introduced from the oil-pressure source. The supply/discharge port 21 serves as the second port from which the operating oil discharged from the oil-pressure chamber 31 flows out, and the operating oil is discharged to the outside of the oil-pressure motor 10. Further, also in this case, each of the auxiliary ports 23 and 24 serves as the third port. The pressure of the operating oil introduced to each of the auxiliary ports 23 and 24 is maintained higher than the atmospheric pressure and lower than the pressure ejected from the oil-pressure source to the supply/discharge port 22 that is the high-pressure first port. For example, the pressure of the operating oil introduced to the auxiliary ports 23 and 24 is maintained not less than 0.01 MPa and not more than 2 MPa.

As above, in the oil-pressure motor 10, when the piston 13 is not located at the dead center or the vicinity of the dead center and is located in a range where the piston 13 moves in the expanding direction, the piston chamber 27 communicates with the first port of the valve plate 11, and the high-pressure operating oil is introduced to the piston chamber 27. Further, when the piston 13 is not located at the dead center or the vicinity of the dead center and is located in a range where the piston 13 moves in the contracting direction, the piston chamber 27 communicates with the second port of the valve plate 11, and the low-pressure operating oil can be discharged to a discharge place. Furthermore, the piston chamber 27 located in the angle range where the piston 13 is located at the dead center or the vicinity of the dead center communicates with the auxiliary port 23 or 24 of the valve plate 11, and the high-pressure operating oil in this piston chamber 27 can be discharged through the auxiliary port 23 or 24 and a drain port 137 (see FIG. 2) to, for example, a drain tank lower in pressure than the piston chamber 27.

Thus, the cylinder block 12 can be rotated by the pressure of the operating oil, and the rotation of the cylinder block 12 can be output from the rotating shaft 17. As above, the oil-pressure motor 10 can drive, for example, a device provided separately. Further, the piston chamber 27 located in the range where the piston 13 is located at the dead center or the vicinity of the dead center is connected to the auxiliary port, and the operating oil can be supplied to or discharged from the piston chamber 27. With this, the smooth movement of the piston in the vicinity of the dead center can be realized in the expanding direction and the contracting direction.

FIG. 4 is an enlarged view showing the upper auxiliary port 23 of FIG. 1 and its vicinity. An opening of the cylinder port 28 which opening faces the valve plate 11 is formed in a shape including a base portion 67 and a convex portion 68 projecting from the base portion 67 at least outward or inward in a radial direction. In the present embodiment, the base portion 67 has a substantially long cylindrical shape, and each of an inner peripheral edge side 70 and outer peripheral edge side 71 of the base portion 67 is formed so as to coincide with a virtual cylindrical surface about the rotation axis L10. The convex portion 68 is formed to project inward in the radial direction from a circumferential-direction middle portion of the base portion 67.

FIG. 6 is a diagram showing a relation between an angle position θ of the piston chamber 27 and a stroke position of the piston 13. FIG. 7 is a diagram showing a relation between the angle position θ of the piston chamber 27 and pressure P of the operating oil in the piston chamber 27. Regarding a horizontal axis in FIGS. 6 and 7, the angle position θ of the piston chamber 27 when the piston 13 is located at one of the dead centers is 0°, and an angle in the rotational direction A1 from the angle position of 0° is shown by 0. In FIG. 6, a vertical axis denotes the stroke position of the piston 13. The stroke position at one of the dead centers is shown by 0, and the stroke position at the other dead center is shown by I. In FIG. 7, a vertical axis denotes the pressure P of the operating oil in the piston chamber 27. Lowest pressure and highest pressure while the piston 13 reciprocates once, that is, while the piston chamber 27 rotates once are shown by P1 and P2, respectively.

When the angle θ1 is 10° as described above, and the piston chamber 27 (i.e., the cylinder port 28) is located in an angle range of more than 10° and less than 170° (10<θ<170), the piston chamber 27 (i.e., the cylinder port 28) is connected to the supply/discharge port 21. When the piston chamber 27 (i.e., the cylinder port 28) is located in an angle range of more than 190° and less than 350° (190<θ<350), the piston chamber 27 (i.e., the cylinder port 28) is connected to the supply/discharge port 22. Further, when the cylinder port 28 is located in an angle range of not less than 0° and not more than 10° (0≦θ≦10) or an angle range of not less than 350° and less than 360° (350≦θ<360), the cylinder port 28 is connected to the upper auxiliary port 23. When the cylinder port 28 is located in an angle range of not less than 170° and not more than 190° (170≦θ≦190), the cylinder port 28 is connected to the lower auxiliary port 24.

When the cylinder port 28 is located in the angle range where the cylinder port 28 is connected to the upper auxiliary port 23, and an entire stroke movement distance of the piston is regarded as 1, the stroke position of the piston 13 is in a position range of not less than 0 and not more than about 0.008. When the cylinder port 28 is located in the angle range where the cylinder port 28 is connected to the lower auxiliary port 24, and the entire stroke movement distance of the piston is regarded as 1, the stroke position of the piston is in a position range of not less than about 0.992 and not more than 1. When the piston 13 is located at the dead center or the vicinity of the dead center, the stroke movement distance relative to a unit angle movement distance of the cylinder block 12 is small. Therefore, the angle range where the cylinder port 28 is connected to the auxiliary port 23 or 24 is about 11% of one rotation (≈40°/360°), and the corresponding range of the stroke position of the piston 13 is about 1.6% (=about 0.008×2).

Further, in the present embodiment, the gradient of the change in the pressure P of the operating oil in the piston chamber 27 is made small by the notch 90. Therefore, while the cylinder port 28 is connected to the port 21, 22, 23, or 24 of the valve plate 11, the pressure P of the operating oil in the piston chamber 27 does not always become constant pressure. For example, while the cylinder port 28 is connected to the high pressure side port that is the first or second port, the pressure P does not always become the highest pressure P2. While the piston chamber 27 is located in the vicinity of the angle position where the status of connection with the high pressure side port is switched between connection and disconnection, that is, while the piston chamber 27 is located in the vicinity of 10° or 170°, the pressure P gradually changes.

In the oil-pressure motor 10, when the cylinder port 28 is located in the angle range of more than 10° and less than 170° (10<θ<170), the piston chamber 27 communicates with the supply/discharge port 21 that is the high pressure side port, and pressure that is not less than average pressure (P1+P2)/2 of the lowest pressure P1 and the highest pressure P2 is introduced to the piston chamber 27. Further, when the cylinder port 28 is located in the angle range other than the above, that is, when the cylinder port 28 is located in the angle range of not less than 0° and not more than 10° (0≦θ≦10) or in the angle range of not less than 170° and less than 360° (170≦θ<360), the piston chamber 27 communicates with the supply/discharge port 22 that is a low pressure side port, or the auxiliary port 23 or 24, and the pressure that is less than the average pressure (P1+P2)/2 of the lowest pressure P1 and the highest pressure P2 is introduced to the piston chamber 27.

Next, features of the oil-pressure motor 10 that is the liquid-pressure rotating device according to the present invention will be explained in more detail. As shown in FIGS. 4 and 5, each of the supply/discharge ports (first and second ports) 21 and 22 is formed so as to face a route through which the base portion 67 of the cylinder port 28 passes when the cylinder block 12 rotates. It should be noted that each of the supply/discharge ports 21 and 22 may be formed so as to face a route through which both the base portion 67 and convex portion 68 of the cylinder port 28 pass.

As shown in FIG. 4, each of the supply/discharge ports 21 and 22 includes a wide portion 130, a narrow portion 131, and the notch 90. Inner peripheral edge sides 75 and 76 of the wide portions 130 substantially coincide with the inner peripheral edge side 70 of the movement route of the cylinder port 28, and outer peripheral edge sides 77 and 78 of the supply/discharge ports 21 and 22 substantially coincide with the outer peripheral edge side 71 of the movement route of the cylinder port 28.

As shown in FIG. 4, the narrow portions 131 are formed at end portions of the supply/discharge ports 21 and 22, the end portions being close to a top dead center switching land 132. Each of the narrow portions 131 is formed as a portion whose opening width W2 in the radial direction of the rotation of the cylinder block 12 is narrower than an opening width W1 of the wide portion 130 in the same direction. To be specific, an inner peripheral edge side 131a of the narrow portion 131 is formed outside the inner peripheral edge side 70 of the movement route of the cylinder port 28 in the radial direction, and an outer peripheral edge side 131b of the narrow portion 131 substantially coincide with the outer peripheral edge side 71 of the movement route of the cylinder port 28.

As shown in FIG. 4, each of the narrow portions 131 is formed in an angle range from a predetermined angle position (θ=0) in the top dead center switching land 132 where the piston 13 is located at the top dead center to an angle positon of not more than 55° (preferably) 45°) in the rotational direction of the piston chamber 27. Further, the notches 90 of the supply/discharge ports 21 and 22 are grooves.

As shown in FIGS. 4 and 5, each of the auxiliary ports 23 and 24 is formed so as to avoid a route through which the base portion 67 of the cylinder port 28 passes when the cylinder block 12 rotates and to face a route through which the convex portion 68 passes when the cylinder block 12 rotates. Inner peripheral edge sides 80 and 81 of the auxiliary ports 23 and 24 coincide with an inner peripheral edge side of the movement route of the convex portion 68 of the cylinder port 28. Each of outer peripheral edge sides 82 and 83 of the auxiliary ports 23 and 24 is formed at an inner side of the inner peripheral edge side 70 of the movement route of the base portion 67 of the cylinder port 28 in the radial direction by an interval W3.

To be specific, the base portion 67 of the cylinder port 28 is formed away from each of the auxiliary ports 23 and 24 by a sealing portion 136 having a predetermined seal width W3 (preferably not less than 3 mm) in the radial direction.

As shown in FIGS. 4 and 5, the auxiliary ports 23 and 24 are formed such that when the piston chamber 27 located at the dead center of the valve plate 11 or the vicinity of the dead center does not communicate with the high pressure side supply/discharge port 21 or 22, the auxiliary port 23 or 24 communicates with this piston chamber 27.

Next, the actions of the oil-pressure motor 10 that is the liquid-pressure rotating device configured as above will be explained. As shown in FIG. 4, in the oil-pressure motor 10, portions of the supply/discharge ports 21 and 22 which portions are located close to the top dead center switching land 132 are formed as the narrow portions 131 each of whose opening width W2 in the radial direction of the rotation of the cylinder block 12 is narrow. Therefore, in a state where the cylinder port 28 of the cylinder block 12 is not located so as to overlap the narrow portion 131, a seal area between the rear end surface 12a of the cylinder block 12 and the valve plate 11 can be increased. With this, the amount of high-pressure operating oil leaking from the piston chamber 27 through the supply/discharge port 21 or 22 can be reduced by a sealed region corresponding to the increased seal area.

The flow rate of the operating oil flowing through the portion (narrow portion 131) of each of the supply/discharge ports 21 and 22 which portion is located close to the top dead center switching land 132 is lower than the flow rate of the operating oil flowing through the portion (wide portion 130) of each of the supply/discharge ports 21 and 22 which portion is far from the top dead center switching land 132. Therefore, even though the narrow portions 131 are formed as above, the pressure loss based on the flow of the operating oil can be prevented from increasing. The reason why the flow rate of the operating oil flowing through the portion close to the switching land 132 is low is because the movement speed of the piston 13 becomes slow as the piston 13 gets close to the switching land 132 (see FIG. 6).

Similarly, the flow rate of the operating oil flowing through the portion of each of the supply/discharge ports 21 and 22 which portion is located close to the bottom dead center switching land 133 is lower than the flow rate of the operating oil flowing through the portion of each of the supply/discharge ports 21 and 22 which portion is far from the bottom dead center switching land 133.

Further, at the portion of each of the supply/discharge ports 21 and 22 which portion is located far from the top dead center or bottom dead center switching land 132 or 133, the narrow portion 131 is not formed, but the wide portion 130 is formed. Therefore, the pressure loss based on the flow of the operating oil flowing through the wide portion 130 does not increase. With this, the volume efficiency of the oil-pressure motor 10 can be effectively improved without deteriorating the mechanical efficiency of the oil-pressure motor 10.

Then, as shown in FIG. 4, each of the narrow portions 131 is formed in an angle range from the predetermined angle position in the top dead center switching land 132 in which the piston 13 is located at the dead center to an angle position of not more than 55° (=θ2) in the rotational direction of the piston chamber 27. With this, the amount of high-pressure operating oil leaking from the supply/discharge port 21 or 22 through the sealed region between the rear end surface 12a of the cylinder block 12 and the valve plate 11 shown in FIG. 2 can be effectively reduced, and the increase in the pressure loss by the flow of the operating oil at the narrow portion 131 can be effectively suppressed.

It is preferable that the angle range where the narrow portion 131 is formed be an angle range of not more than 45° (=θ2). To be specific, the movement speed of the piston 13 can be calculated as a value which changes based on a sine function in which: a predetermined angle position in the top dead center switching land 132 of the valve plate 11 when the piston 13 is located at the top dead center is 0° (=θ); and the rotation angle of the piston chamber 27 is 0 (see FIG. 6). The movement speed of the piston 13 at the angle position where the rotation angle θ of the piston chamber 27 is 45° is about 70% of the maximum movement speed (the movement speed of the piston 13 becomes the maximum movement speed when the piston 13 is located at the angle position where the angle θ is 90°. Each of the flow rate of the operating oil flowing into the piston chamber 27 and the flow rate of the operating oil flowing out from the piston chamber 27 becomes about 70% of the maximum flow rate. Therefore, the opening width W2 of the narrow portion 131 in the radial direction can be set to about 70% of the opening width W1 of the wide portion 130 of each of the supply/discharge ports 21 and 22, and the sealed region having an appropriate width can be formed.

Further, as shown in FIG. 5, the lower auxiliary port 24 is formed such that when the cylinder port 28 (piston chamber 27) located at the bottom dead center of the valve plate 11 or the vicinity of the bottom dead center does not communicate with, for example, the high pressure side supply/discharge port 21, the lower auxiliary port 24 communicates with this cylinder port 28 (piston chamber 27). Similarly, the upper auxiliary port 23 is formed such that when the cylinder port 28 (piston chamber 27) located at the top dead center of the valve plate 11 or the vicinity of the top dead center does not communicate with, for example, the high pressure side supply/discharge port 21, the upper auxiliary port 23 communicates with this cylinder port 28 (piston chamber 27).

With this, when the cylinder port 28 of the piston chamber 27 performs the rotational movement at the bottom dead center and the vicinity of the bottom dead center in a state where the cylinder port 28 of the piston chamber 27 does not communicate with the high pressure side supply/discharge port 21 and is sealed by the valve plate 11, that is, in a state where the high-pressure operating oil is stored in the cylinder port 28 of the piston chamber 27, the lower auxiliary port 24 communicates with the piston chamber 27, and the high-pressure operating oil in the piston chamber 27 can be discharged through the lower auxiliary port 24. Therefore, the high-pressure operating oil in the piston chamber 27 can be prevented from leaking from between the rear end surface 12a of the cylinder block 12 and the valve plate 11, and the volume efficiency can be improved.

Further, with this, force applied from the piston 13 through the shoe 14 to the swash plate 15 and force applied from the cylinder block 12 to the valve plate 11 can be reduced, and frictional force between members sliding each other, such as between the shoe 14 and the swash plate 15 or between the valve plate 11 and the cylinder block 12, can be reduced. As a result, the mechanical loss can be reduced, and the seize resistance between the members sliding each other improves, in other words, the seizing can be made hard to occur.

Then, as described above, by the reduction in the leak amount of high-pressure operating oil, the oil-pressure motor 10 can be driven by pressure, lower than conventional pressure, at the time of start-up.

Further, when the cylinder port 28 shown in FIG. 5 performs the rotational movement at the dead center of the valve plate 11 and the vicinity of the dead center, the base portion 67 of the cylinder port 28 can be located away from each of the auxiliary ports 23 and 24 by the sealing portion 136 having the predetermined seal width W3 in the radial direction. With this, in a state where the base portion 67 of the cylinder port 28 located at the dead center of the valve plate 11 or the vicinity of the dead center communicates with the high pressure side supply/discharge port 21, the high-pressure operating oil can be prevented from flowing out through the base portion 67 to the auxiliary port 23 or 24. With this, the energy of the high-pressure operating oil can be efficiently utilized.

Then, the convex portion 68 of the cylinder port 28 can be set so as to communicate with the auxiliary port 23 or 24 at a predetermined timing at which the base portion 67 of the cylinder port 28 shown in FIG. 5 does not communicate with the high pressure side supply/discharge port 21. With this, the high-pressure operating oil in the piston chamber 27 communicating with the cylinder port 28 can be discharged through the auxiliary port 23 or 24.

Then, when the seal width W3 is not less than 3 mm, and the base portion 67 of the cylinder port 28 at the dead center of the valve plate 11 or the vicinity of the dead center communicates with the high pressure side supply/discharge port 21, the base portion 67 is located away from the auxiliary port 23 or 24 by the sealing portion 136 having the seal width W3 of not less than 3 mm in the radial direction. Therefore, the high-pressure operating oil in the piston chamber 27 can be effectively prevented from leaking through the sealing portion 136 having the seal width of not less than 3 mm and flowing into the auxiliary port 23 or 24.

Further, according to the oil-pressure motor 10, the piston chamber 27 in the angle range where the piston 13 is located at the vicinity of the dead center can perform the supply and discharge of the operating oil through the auxiliary port 23 or 24. With this, the smooth movement of the piston 13 in the expanding direction and the contracting direction at the vicinity of the dead center can be achieved. In addition, the operating oil having pressure higher than atmospheric pressure is introduced to the auxiliary ports 23 and 24, and when the piston 13 moves in the expanding direction at the vicinity of the dead center, it is unnecessary to suction the operating oil by negative pressure generated by the movement of the piston 13. Therefore, cavitation can be prevented.

Further, according to the oil-pressure motor 10, when the piston chamber 27 stores the high-pressure operating oil without communicating with the high pressure side supply/discharge port 21 or 22 and performs the rotational movement at the dead center and the vicinity of the dead center, the auxiliary port 23 or 24 can communicate with the piston chamber 27, and therefore, the high-pressure operating oil in the piston chamber 27 can be discharged through the auxiliary port 23 or 24.

In the above embodiment, as shown in FIG. 4, the narrow portion 131 is formed to have the opening width W2 that is substantially constant. However, instead of this, the narrow portion 131 may be formed such that the opening width W2 decreases as the narrow portion 131 extends toward the top dead center of the valve plate 11.

To be specific, the flow rate of the operating oil in the piston chamber 27 decreases as the piston chamber 27 moves toward the dead center (θ=0°) of the valve plate 11. Therefore, while suppressing the increase in the pressure loss based on the flow of the operating oil at the narrow portion 131, the amount of high-pressure operating oil leaking from the supply/discharge port 21 or 22 through between the rear end surface 12a of the cylinder block 12 and the valve plate 11 can be efficiently reduced.

In the above embodiment, as shown in FIGS. 4 and 5, the auxiliary ports 23 and 24 are through holes formed on the valve plate 11. However, instead of the through holes, as shown in FIGS. 8A and 8B, a concave portion may be formed on an inner edge portion of an attachment hole 134 formed at a middle of the valve plate 11, the rotating shaft 17 being attached to the attachment hole 134. As with the above embodiment, the pressure of the operating oil introduced to this concave portion is maintained higher than the atmospheric pressure and lower than the pressure ejected from the oil-pressure source and introduced to the high pressure side supply/discharge port 21 or 22. For example, the pressure of the operating oil introduced to the concave portion is maintained not less than 0.01 MPa and not more than 2 MPa. Other than this, the concave portion is the same as the auxiliary ports 23 and 24 of the above embodiment, so that detailed explanations thereof are omitted.

Further, in the above embodiment, as shown in FIG. 1, the narrow portions 131 are formed at the respective upper end portions of the supply/discharge ports 21 and 22. However, instead of this, the narrow portion 131 may be formed at any one of the lower end portions of the supply/discharge ports 21 and 22.

Further, in the above embodiment, as shown in FIG. 1, the narrow portions 131 are formed at the respective portions of the supply/discharge ports 21 and 22 which portions are located close to the top dead center switching land 132, and the narrow portions 131 are not formed at the respective portions of the supply/discharge ports 21 and 22 which portions are located close to the bottom dead center switching land 133. However, instead of this, the narrow portions 131 may be formed at the portions of the supply/discharge ports 21 and 22 which portions are located close to the top dead center switching land 132 and the portions of the supply/discharge ports 21 and 22 which portions are located close to the bottom dead center switching land 133.

Further, in the above embodiment, as shown in FIGS. 4 and 5, the upper auxiliary port 23 and the lower auxiliary port 24 are provided. However, instead of these, only one of these auxiliary ports may be provided.

Further, in the above embodiment, as shown in FIG. 1, one supply/discharge port 21 and one supply/discharge port 22 are provided at the left side and the right side, respectively. However, instead of these, as shown in FIG. 8A, a plurality of (three, for example) supply/discharge ports may be provided at each of the left and right sides: In this case, the narrow portions 131 may be fanned at ports located close to the top dead center switching land 132 among the three supply/discharge ports 21 and the three supply/discharge ports 22.

Further, the above embodiment has explained an example in which the liquid-pressure rotating device of the present invention is used as a variable displacement swash plate type motor. However, instead of this, the liquid-pressure rotating device of the present invention can be used as a variable displacement swash plate type pump or a fixed displacement motor or pump.

Further, the liquid-pressure rotating device of the present invention can be used as each of a device that is rotatable in both normal and reverse directions and a device that rotates in only one direction.

In the above embodiment, the pressure of each of the auxiliary ports 23 and 24 is set to be higher than the atmospheric pressure and lower than the pressure of the high pressure side supply/discharge port. However, instead of this, the pressure of each of the auxiliary ports 23 and 24 may be set to become pressure of the drain tank by connecting the auxiliary ports 23 and 24 to the drain tank.

Further, the above embodiment has explained an example in which the oil is used as the operating liquid. However, instead of this, water may be used as the operating liquid.

Further, in the above embodiment, the notches 90 are included. However, the notches 90 may not be included.

From the foregoing explanation, many modifications and other embodiments of the present invention are obvious to one skilled in the art. Therefore, the foregoing explanation should be interpreted only as an example and is provided for the purpose of teaching the best mode for carrying out the present invention to one skilled in the art. The structures and/or functional details may be substantially modified within the scope of the present invention.

INDUSTRIAL APPLICABILITY

As above, the liquid-pressure rotating device according to the present invention has excellent effect of being able to reduce the amount of high-pressure operating oil leaking from the first or second port through the sealed region between the rear end surface of the cylinder block and the valve plate and suppress the increase in the pressure loss of the operating oil flowing through the first and second ports. Thus, the present invention is suitably applied to such liquid-pressure rotating device.

REFERENCE SIGNS LIST

10 oil-pressure motor

11 valve plate

12 cylinder block

13 piston

14 shoe

15 swash plate

16 casing

17 rotating shaft

21 supply/discharge port (first port)

22 supply/discharge port (second port)

23 upper auxiliary port (third port)

24 lower auxiliary port (third port)

27 piston chamber

28 cylinder port

67 base portion

68 convex portion

90 notch

130 wide portion

131 narrow portion

131 a inner peripheral edge side

131 b outer peripheral edge side

132 top dead center switching land

133 bottom dead center switching land

134 attachment hole

136 sealing portion

137 drain port

L10 rotation axis

L11 tilt axis

W1 opening width of wide portion

W2 opening width of narrow portion

W3 seal width of sealing portion

Claims

1. A liquid-pressure rotating device comprising: a cylinder block provided rotatably and including a plurality of piston chambers formed at intervals in a circumferential direction;a plurality of pistons fitted in the respective piston chambers so as to be movable in an expanding direction and a contracting direction and configured to reciprocate in the expanding direction and the contracting direction; anda valve plate provided in contact with the cylinder block and including a first port, a second port, and a switching land formed between the first port and the second port, the first and second ports communicating with the piston chambers, wherein:a portion of at least one of the first and second ports of the valve plate which portion is located close to the switching land is formed as a narrow portion having a narrow opening width in a radial direction;an auxiliary port is formed at the switching land of the valve plate;pressure of the auxiliary port is maintained lower than pressure of a high pressure side port that is any one of the first and second ports; andwhen the piston chamber does not communicate with the high pressure side port that is the first or second port, the piston chamber and the auxiliary port communicate with each other.

2. The liquid-pressure rotating device according to claim 1, wherein the narrow portion is formed in an angle range from a position of a dead center to a position of not more than 45° in the circumferential direction.

3. The liquid-pressure rotating device according to claim 1, wherein: openings of the piston chambers which openings face the valve plate serve as cylinder ports; andthe opening width of the narrow portion in the radial direction decreases as the narrow portion extends toward the dead center.

4. The liquid-pressure rotating device according to claim 1, wherein: openings of the piston chambers which openings face the valve plate serve as cylinder ports;each of the cylinder ports has a shape including a base portion and a convex portion projecting from the base portion outward or inward in the radial direction;the convex portion is formed such that when the piston chamber communicates with the auxiliary port through the cylinder port, only the convex portion communicates with the auxiliary port; andbefore and after the piston chamber communicates with the auxiliary port through the cylinder port, the base portion is located away from the auxiliary port by a sealing portion having a predetermined seal width in the radial direction.

5. The liquid-pressure rotating device according to claim 4, wherein the seal width is not less than 3 mm.