Patent Description:
There is a hydraulic rotating machine which includes a swash plate which is provided in a casing so as to be tiltable, and a tilt control piston which controls the tilt angle of the swash plate (see <CIT> which discloses a hydraulic rotating machine according to the preamble of claim <NUM>). In the hydraulic rotating machine described in <CIT>, a cylinder hole is formed in the casing, the tilt control piston is slidably inserted into the cylinder hole. Further hydraulic rotating machines are known from <CIT>, <CIT> and <CIT>.

In the hydraulic rotating machine described in <CIT>, since the tilt control piston slides in the cylinder hole, the inner peripheral surface of the cylinder hole is worn, thereby there is a possibility that the performance of a pump is deteriorated. To suppress wear of the inner peripheral surface of the cylinder hole, it is effective to perform a surface treatment such as heat treatment as a method of improving the hardness of the inner peripheral surface of the cylinder hole. However, it is not easy to perform the surface treatment such as heat treatment to the inner peripheral surface of the cylinder hole formed in the casing.

It is the object of the present invention to easily improve a wear resistance of a sliding surface that a tilt control piston slides.

The object of the invention is achieved with a hydraulic rotating machine according to claim <NUM>. An advantageous further development of the invention is defined by claim <NUM>.

A hydraulic rotating machine according to an embodiment of the present invention will be described with reference to the drawings. <FIG> and <FIG> are a cross-sectional view of the hydraulic rotating machine. <FIG> shows a state in which a tilt angle is maximum, <FIG> shows a state in which the tilt angle is minimum. <FIG> is a partial enlarged view of <FIG>, and <FIG> is a partial enlarged view of <FIG>.

The hydraulic rotating machine functions as a piston pump capable of discharging a hydraulic oil as a working fluid by rotating a shaft <NUM> and reciprocating a piston <NUM> by an power from the outside. The hydraulic rotating machine also functions as a piston motor capable of outputting a rotational driving force by reciprocating the piston <NUM> and rotating the shaft <NUM> by the fluid pressure of the hydraulic oil supplied from the outside. Incidentally, the hydraulic rotating machine may function only as the piston pump, or may function only as the piston motor.

In the present embodiment, a case where the hydraulic rotating machine is used as a swash plate type piston pump will be exemplified. Hereinafter, the hydraulic rotating machine is referred to as a "piston pump <NUM>".

As shown in <FIG> and <FIG>, the piston pump <NUM> is used as a hydraulic supply source for supplying hydraulic oil to an actuator such as a hydraulic cylinder (not shown). The piston pump <NUM> includes a shaft <NUM> which is rotated by a power source such as an engine (not shown), a cylinder block <NUM> which is connected to the shaft <NUM> and rotates together with the shaft <NUM>, and a case <NUM> which houses the cylinder block <NUM>, as shown in <FIG>. Hereinafter, a direction along a rotation center axis O1 of the cylinder block <NUM> (i.e. a central axis of the shaft <NUM>) is referred to as an axial direction, a circumferential direction around the rotation center axis O1 of the cylinder block <NUM> is referred to as a circumferential direction.

The case <NUM> includes a bottomed cylindrical case body 3a whose one end opens, and a cover 3b that closes the open end of the case body 3a. An inside of the case <NUM> communicates with a tank (not shown) through a drain passage (not shown).

The cover 3b is provided with a through hole 3c through which the shaft <NUM> penetrates. One end 1a of the shaft <NUM> is rotatably supported by the through hole 3c of the cover 3b via a bearing 4a. A power source such as an engine (not shown) is connected to the end 1a of the shaft <NUM> protruding from the case <NUM> to the outside.

The bottom of the case body 3a is provided with a shaft housing portion 3d that houses the other end 1b of the shaft <NUM>. The end 1b of the shaft <NUM> is rotatably supported by the shaft housing portion 3d of the case body 3a via a bearing 4b. Incidentally, the bottom of the case body 3a may be provided with the shaft housing portion 3d as a through hole through which the shaft <NUM> penetrates, and a rotary shaft of other hydraulic pump such as a gear pump (not shown) may be connected to the end 1b of the shaft <NUM> protruding from the case <NUM> to the outside.

The cylinder block <NUM> is provided with a through hole 2a through which the shaft <NUM> penetrates. The through hole 2a of the cylinder block <NUM> is splined to the shaft <NUM>. Thus, the cylinder block <NUM> rotates with the rotation of the shaft <NUM>.

The cylinder block <NUM> is provided with a plurality of cylinders 2b which open at one end of the cylinder block <NUM>. The cylinders 2b are formed in parallel with the shaft <NUM>. The plurality of cylinders 2b are formed with a predetermined interval in the circumferential direction of the cylinder block <NUM>. A cylindrical piston <NUM> is reciprocatively inserted into the cylinder 2b, and a volume chamber <NUM> is formed by the cylinder 2b and the piston <NUM>. The distal end of the piston <NUM> protrudes from a opening of the cylinder 2b. A spherical seat 5a is formed at the distal end of the piston <NUM>, the spherical seat 5a is rotatably connected to a shoe <NUM> described later.

The piston pump <NUM> further includes a swash plate <NUM> that reciprocates the piston <NUM> as the cylinder block <NUM> rotates, a shoe <NUM> that is in sliding contact with a sliding contact surface 8a formed on the front surface (a surface on the left side shown in the drawing) of the swash plate <NUM>, and a valve plate <NUM> that is provided between the cylinder block <NUM> and the bottom portion of the case body 3a.

The swash plate <NUM> is swingably supported by the case <NUM> via a tilt bearing <NUM>. In the piston pump <NUM>, a stroke of the piston <NUM> with respect to the cylinder 2b is changed by changing a tilt angle of the swash plate <NUM>. Thus, the pump capacity (displacement volume) which is a discharge amount of the hydraulic oil per rotation of the piston pump <NUM> is changed. The pump capacity becomes a minimum value when the tilt angle of the swash plate <NUM> is a minimum value. The pump capacity increases as the tilt angle of the swash plate <NUM> increases and becomes a maximum value when the tilt angle of the swash plate <NUM> is a maximum value. The tilt angle of the swash plate <NUM> is controlled by a tilt control device <NUM> described later.

The valve plate <NUM> is a member which a base end surface of the cylinder block <NUM> is in sliding contact with. The valve plate <NUM> is fixed to the bottom of the case body 3a. Although not shown, a suction port and a discharge port are formed in the valve plate <NUM>. The suction port connects a suction passage formed on the case body 3a and the volume chamber <NUM>. The discharge port connects a discharge passage formed on the case body 3a and the volume chamber <NUM>.

The tilt control device <NUM> includes a large-diameter piston <NUM> as a tilt control piston for controlling the tilt angle of the swash plate <NUM>, and a pressure chamber <NUM> that the large-diameter piston <NUM> faces. The case body 3a is provided with a housing recess <NUM> in which the large-diameter piston <NUM> is reciprocally accommodated. The pressure chamber <NUM> is formed by the housing recess <NUM> and the large-diameter piston <NUM>. The large-diameter piston <NUM> is disposed so as to face the front surface of the swash plate <NUM> (the surface on the left side shown in the drawing). The large-diameter piston <NUM> biases the swash plate <NUM> in a direction in which the tilt angle decreases by the pressure of the pressure chamber <NUM>.

The tilt control device <NUM> further includes a stopper <NUM> that defines a minimum value (a minimum tilt angle) of the tilt angle of the swash plate <NUM>, a small-diameter piston <NUM> as a tilt control piston that controls the tilt angle of the swash plate <NUM>, and a pressure chamber <NUM> that the small-diameter piston <NUM> faces. A mounting hole <NUM> is formed in the cover 3b. The the stopper <NUM> is mounted to the mounting hole <NUM>. The stopper <NUM> has a through hole. The inner peripheral surface of the through hole is a sliding surface <NUM> for slidably supporting the small-diameter piston <NUM>. The pressure chamber <NUM> is formed by the mounting hole <NUM>, the stopper <NUM>, and the small-diameter piston <NUM>. The small-diameter piston <NUM> is disposed so as to face the back surface of the swash plate <NUM> (a surface of the right side shown in the drawing). The small-diameter piston <NUM> biases the swash plate <NUM> in a direction in which the tilt angle increases by the pressure of the pressure chamber <NUM>.

The large-diameter piston <NUM> and the small-diameter piston <NUM> are disposed to face each other across the swash plate <NUM>. In the present embodiment, the large-diameter piston <NUM> and the small-diameter piston <NUM> are arranged so as to be concentric.

The pressure chamber <NUM> is connected to the discharge passage (not shown) of the piston pump <NUM>. Therefore, the discharge pressure P1 (self-pressure) of the piston pump <NUM> is always guided to the pressure chamber <NUM> through the discharge passage (not shown).

The tilt control device <NUM> further includes a control pressure adjusting device <NUM> for adjusting the pressure (Hereinafter, referred to control pressure Pc) of the pressure chamber <NUM>. The control pressure adjusting device <NUM> adjusts the control pressure Pc in accordance with the discharge pressure P1 of the piston pump <NUM> to control an output of the piston pump <NUM>.

The control pressure adjusting device <NUM> includes a control pressure adjusting spool <NUM> for adjusting the control pressure Pc, a sleeve <NUM> for axially movably accommodating the control pressure adjusting spool <NUM>, a cylindrical feedback pin <NUM> that abuts the swash plate <NUM>, and springs 53a and 53b as biasing members for biasing the feedback pin <NUM> toward the swash plate <NUM> and for biasing the control pressure adjusting spool <NUM> in a direction for switching the control pressure adjusting spool <NUM> to a tank communication position described later.

The tilt angle of the swash plate <NUM> is adjusted by a balance of a moment around a swing center axis O2. The direction of the moment of the force transmitted from the feedback pin <NUM> to the swash plate <NUM> by the elastic force of the springs 53a and 53b is the same as a direction of the moment of the force transmitted from the small-diameter piston <NUM> to the swash plate <NUM> by the pressure of the pressure chamber <NUM>, and is opposite to a direction of the moment of the force transmitted from the large-diameter piston <NUM> to the swash plate <NUM> by the pressure of the pressure chamber <NUM>.

The control pressure adjusting device <NUM> has a pump port 50p communicating with the discharge passage (not shown) of the piston pump <NUM>, a tank port 50t communicating with a tank (not shown), and a control pressure port 50c communicating with the pressure chamber <NUM>.

The control pressure adjusting spool <NUM> has a pump communication position and a tank communication position. In the pump communication position, the pump port 50p and the control pressure port 50c communicate with each other and a communication between the tank port 50t and the control pressure port 50c is blocked. In the tank communication position, the tank port 50t and the control pressure port 50c communicate with each other and a communication between the pump port 50p and the control pressure port 50c is blocked.

When the control pressure adjusting spool <NUM> is switched to the pump communication position, the hydraulic oil discharged from the piston pump <NUM> is guided to the pressure chamber <NUM>, and the control pressure Pc increases. When the control pressure Pc becomes higher than the predetermined pressure, the swash plate <NUM> tilts in a direction in which the tilt angle of the swash plate <NUM> decreases, and the pump capacity decreases.

When the control pressure adjusting spool <NUM> is switched to the tank communication position, the hydraulic oil of the pressure chamber <NUM> is discharged to the tank (not shown), and the control pressure Pc decreases. When the control pressure Pc becomes lower than the predetermined pressure, the swash plate <NUM> tilts in a direction in which the tilt angle of the swash plate <NUM> increases, and the pump capacity increases.

The control pressure adjusting device <NUM> may include a port which the discharge pressure (external pump pressure) of another pump driven by the engine (not shown) together with the piston pump <NUM>, and/or the signal pressure (external signal pressure) from the outside is guided. In this case, the control characteristics of the swash plate <NUM> can be adjusted by the external pump pressure and/or the external signal pressure.

The piston pump <NUM> is controlled by the tilt control device <NUM> so that the pump capacity decreases when the discharge pressure P1 increases and the pump capacity increases when the discharge pressure P1 decreases. Hereinafter, as an example of the operation of the piston pump <NUM>, the operation of the piston pump <NUM> when the discharge pressure P1 increases to the predetermined pressure will be described.

If the discharge pressure P1 of the piston pump <NUM> is less than a predetermined value, the pump capacity is maintained at a maximum state (see <FIG>). When the discharge pressure P1 increases to a predetermined pressure equal to or higher than the predetermined value, the control pressure adjusting spool <NUM> moves to the right in the drawing and is switched to the pump communication position. When the control pressure adjusting spool <NUM> is switched to the pump communication position, the pressure in the pressure chamber <NUM> (the control pressure Pc) increases and the large-diameter piston <NUM> presses the swash plate <NUM>, so that the tilt angle of the swash plate <NUM> decreases.

When the tilt angle of the swash plate <NUM> decreases as the control pressure Pc increases, the feedback pin <NUM> is pushed leftward in the drawing by the swash plate <NUM>. When the feedback pin <NUM> is pushed to the leftward, the control pressure adjusting spool <NUM> is pushed back to the leftward by being biased by the feedback pin <NUM> via the springs 53a and 53b and switched to the tank communication position. When the control pressure adjusting spool <NUM> is switched to the tank communicating position, the pressure of the pressure chamber <NUM> decreases. When the control pressure Pc decreases, the tilt angle of the swash plate <NUM> increases because the swash plate <NUM> is pressed by the small-diameter piston <NUM>.

When the tilt angle of the swash plate <NUM> increases as the control pressure Pc decreases, the control pressure adjusting spool <NUM> is switched to the pump communication position again, and the tilt angle of the swash plate <NUM> decreases. Thus, in the tilt control device <NUM>, the increase and decrease of the tilt angle of the swash plate <NUM> is repeated. When the moment of the force transmitted from the small-diameter piston <NUM> and the feedback pin <NUM> to the swash plate <NUM> and the moment of the force transmitted from the large-diameter piston <NUM> to the swash plate <NUM> are balanced, the tilt of the swash plate <NUM> is stopped, and the tilt angle of the swash plate <NUM> becomes a tilt angle in accordance with the discharge pressure P1.

Thus, in the present embodiment, a horsepower control is performed in which the pump capacity is controlled in accordance with the discharge pressure P1 so that an output of the piston pump <NUM> is kept constant. In the horsepower control, when the discharge pressure P1 of the piston pump <NUM> increases, the tilt angle is controlled so that the pump capacity decreases. Thus, it is possible to prevent an overload of the engine (not shown) as the power source of the piston pump <NUM>.

In general, in a piston pump, the members constituting the piston pump may wear due to sliding, and thereby, backlash between the members occur. The backlash between the members may cause deterioration of the pump performance, such as unstable discharge rate of the piston pump. Therefore, in order to maintain the pump performance over a long period, it is effective to suppress the wear of the member. As a method for suppressing the wear of the member, it is effective to perform surface treatment such as heat treatment on the member. However, depending on size and shape of the member, it may not be easy to perform the surface treatment. For example, since the case body 3a and the cover 3b constituting the case <NUM> are large and complicated shape compared to other components, it is particularly difficult to perform the surface treatment to the case body 3a and the cover 3b.

Therefore, in the present embodiment, the cover 3b does not directly slidably support the small-diameter piston <NUM> which is a sliding component, but a small component mounted to the cover 3b slidably supports the small-diameter piston <NUM>. In addition, the stopper <NUM> which defines the minimum tilt angle of the swash plate <NUM> is adopted as the small component for slidably supporting the small-diameter piston <NUM>. That is, the stopper <NUM> according to the present embodiment has both a function of defining the minimum tilt angle of the swash plate <NUM> and a function of slidably supporting the small-diameter piston <NUM>. Thus, as compared with a case of providing individually parts having respective functions, it is possible to reduce the number of parts.

The swash plate <NUM> includes a swash plate body <NUM> formed by casting or the like, a piston receiving member <NUM> disposed between the swash plate body <NUM> and the small-diameter piston <NUM>, a first support member <NUM> disposed between the swash plate body <NUM> and the large-diameter piston <NUM>, and a second support member <NUM> disposed between the swash plate body <NUM> and the feedback pin <NUM>.

The stopper <NUM> has a mounting portion <NUM> which is mounted to the mounting hole <NUM> of the cover 3b, and an abutting portion <NUM> which abuts the piston receiving member <NUM> which is attached to the swash plate <NUM>. A male screw is formed on the outer periphery of the mounting portion <NUM>. The male screw is screwed onto a female screw which is formed on the inner periphery of the mounting hole <NUM>.

As shown in <FIG> and <FIG>, a state in which the large-diameter piston <NUM> abuts against the bottom of the housing recess <NUM> and the protruding length of the small-diameter piston <NUM> protruding from the stopper <NUM> toward the swash plate <NUM> is maximized is a state in which the tilt angle of the swash plate <NUM> is maximized. From this state, the tilt angle of the swash plate <NUM> is decreased, and as shown in <FIG> and <FIG>, when the piston receiving member <NUM> attached to the swash plate <NUM> abuts the distal end surface of the abutting portion <NUM> of the stopper <NUM>, it is restricted that the tilt angle of the swash plate <NUM> is further decreased. A state in which the piston receiving member <NUM> attached to the swash plate <NUM> abuts the distal end surface of the abutting portion <NUM> and the small-diameter piston <NUM> is housed in the stopper <NUM> is a state in which the tilt angle of the swash plate <NUM> is minimized.

As shown in <FIG>, the small-diameter piston <NUM> accommodated in the through hole of the stopper <NUM> has a cylindrical piston body <NUM> and a piston shoe <NUM> provided at the distal end of the piston body <NUM>. The piston shoe <NUM> has a disc-shaped base <NUM> and a spherical seat <NUM> which is fixed to the base <NUM>. Incidentally, the base <NUM> and the spherical seat <NUM> may be formed as a single component by integral molding.

A receiving portion 71a for receiving the spherical seat <NUM> of the piston shoe <NUM> is formed at the distal end of the piston body <NUM>. The inner surface of the receiving portion 71a is formed in a spherical shape so as to be in sliding contact with the outer surface of the spherical seat <NUM>. This allows the piston shoe <NUM> to be displaced in any direction relative to the piston body <NUM>.

The piston receiving member <NUM> is attached to a step portion <NUM> formed on the back surface of the swash plate <NUM>. A back-side recess <NUM> as a recess portion is formed on the step portion <NUM>. The piston receiving member <NUM> has a cylindrical press-fit portion <NUM> which is press-fitted and fixed to the back-side recess <NUM>, and a disc-shaped receiving portion <NUM> which abuts the step portion <NUM>. A sliding contact surface <NUM> is formed on the receiving portion <NUM>. The small-diameter piston <NUM> is in sliding contact with the sliding contact surface <NUM>.

The sliding contact surface <NUM> of the receiving portion <NUM> is in sliding contact with the base <NUM> of the piston shoe <NUM>. The piston shoe <NUM> is held in a state sandwiched between the receiving portion <NUM> of the piston receiving member <NUM> and the receiving portion 71a of the piston body <NUM>. Therefore, in the present embodiment, in a case where the tilt angle is in the minimum state, when the control pressure Pc is lowered and the small-diameter piston <NUM> is pushed toward the swash plate <NUM> by the discharge pressure P1 of the piston pump <NUM>, the piston shoe <NUM> provided at the distal end of the small-diameter piston <NUM> presses the swash plate body <NUM> via the piston receiving member <NUM>. Thus, the tilt angle of the swash plate <NUM> increases.

Since the stopper <NUM> is smaller in size and simpler in shape than the cover 3b, it is possible to easily perform surface treatment such as heat treatment. Therefore, it is possible to easily improve the hardness of the sliding surface <NUM> on which the outer peripheral surface of the small-diameter piston <NUM> slides. Thus, backlash and/or prizing between the small-diameter piston <NUM> and the sliding surface <NUM> are prevented over a long period, and thereby, it is possible to maintain good sliding property. As a result, it is possible to prevent the control of the swash plate <NUM> from becoming unstable due to the backlash or the like, and to maintain good pump performance for a long period.

Furthermore, in the present embodiment, by improving the hardness of the sliding surface <NUM>, it can be set shorter axial length of the piston body <NUM>. Thus, it is possible to reduce the frictional resistance between the sliding surface <NUM> and the piston body <NUM>. As a result, the hysteresis of the tilt angle of the swash plate <NUM> between increasing the tilt angle and decreasing the tilt angle, which is set in accordance with the control pressure Pc, can be reduced.

Further, since the piston receiving member <NUM> is smaller in size and simpler in shape than the swash plate <NUM>, it is possible to easily perform surface treatment such as heat treatment. Therefore, it is possible to easily improve the hardness of the sliding contact surface <NUM> which the piston shoe <NUM> of the small-diameter piston <NUM> is in sliding contact with. Thus, it is possible to prevent wear of the sliding contact surface <NUM>.

When the swash plate <NUM> is worn, the position of the force transmitted from each of the small-diameter piston <NUM>, the large-diameter piston <NUM>, and the feedback pin <NUM> may change, and thereby, the performance of the piston pump <NUM> may change. In the present embodiment, as described above, since the small-diameter piston <NUM> is in sliding contact with the piston receiving member <NUM> attached to the swash plate <NUM>, the wear of the swash plate <NUM> can be prevented. As a result, the performance of the piston pump <NUM> can be well maintained for a long period.

As shown in <FIG> and <FIG>, a front-side first recess <NUM> and a front-side second recess <NUM> as recesses are formed on the front surface of the swash plate <NUM>. The cylindrical or spherical first support member <NUM> is accommodated in the front-side first recess <NUM>. The cylindrical or spherical second support member <NUM> is accommodated in the front-side second recess <NUM>.

The first support member <NUM> is held in a state sandwiched between the front-side first recess <NUM> and the large-diameter piston <NUM>. That is, the large-diameter piston <NUM> transmits a force to the swash plate <NUM> via the first support member <NUM>. The second support member <NUM> is held in a state sandwiched between the front-side second recess <NUM> and the feedback pin <NUM>. That is, the feedback pin <NUM> transmits a force to the swash plate <NUM> via the second support member <NUM>.

Since the first support member <NUM> is smaller in size and simpler in shape than the swash plate <NUM>, surface treatment such as heat treatment can be easily performed. Therefore, it is possible to easily improve the hardness of a sliding contact surface 86a which the large-diameter piston <NUM> is in sliding contact with. Similarly, since the second support member <NUM> is smaller in size and simpler in shape than the swash plate <NUM>, surface treatment such as heat treatment can be easily performed. Therefore, it is possible to easily improve the hardness of a sliding contact surface 87a which the feedback pin <NUM> is in sliding contact with.

Since the large-diameter piston <NUM> is in sliding contact with the first support member <NUM> provided on the swash plate <NUM>, wear of the swash plate <NUM> can be prevented. Further, since the feedback pin <NUM> is in sliding contact with the second support member <NUM> provided on the swash plate <NUM>, wear of the swash plate <NUM> can be prevented. As a result, the performance of the piston pump <NUM> can be well maintained for a long period.

The large-diameter piston <NUM> biases the swash plate <NUM> against the force transmitted from the small-diameter piston <NUM> to the swash plate <NUM> and the force transmitted from the feedback pin <NUM> to the swash plate <NUM>. Therefore, the force acting on the front-side first recess <NUM> of the swash plate <NUM> from the first support member <NUM> is larger than the force acting on the front-side second recess <NUM> of the swash plate <NUM> from the second support member <NUM>. In the present embodiment, as shown in <FIG>, a curved surface 83a contacting the outer peripheral surface of the first support member <NUM> is formed at the bottom of the front-side first recess <NUM>. Therefore, as compared with a case where the first support member <NUM> and the bottom of the front-side first recess <NUM> are point contact or line contact with each other, the load applied from the first support member <NUM> to the bottom of the front-side first recess <NUM> can be dispersed, and thereby, wear of the front-side first recess <NUM> can be effectively prevented.

The bottom of the front-side first recess <NUM> and the bottom of the back-side recess <NUM> are communicated through a communication passage <NUM>. Therefore, when the press-fit portion <NUM> of the piston receiving member <NUM> is press-fitted to the back-side recess <NUM>, a gas between the back-side recess <NUM> and the press-fit portion <NUM> is discharged to the front-side first recess <NUM> through the communication passage <NUM>. Therefore, the piston receiving member <NUM> can be appropriately and easily attached to the swash plate <NUM>.

Further, in the present embodiment, as shown in <FIG>, each member is disposed so that a contact portion C1 between the small-diameter piston <NUM> and the swash plate <NUM>, a contact portion C2 between the large-diameter piston <NUM> and the swash plate <NUM>, and a contact portion C3 between the feedback pin <NUM> and the swash plate <NUM> are positioned on the same plane. The effect of this configuration will be described in comparison with the comparative example.

In the comparative example of the present embodiment, the contact portion C2 is disposed on a virtual plane which is perpendicular to the swing center axis O2 of the swash plate <NUM> and includes the rotation center axis O1 of the cylinder block <NUM>. Further, in the comparative example of the present embodiment, the contact portion C1 is disposed at a position separated from the virtual plane by a predetermined distance on one side. The contact portion C3 is disposed at a position separated from the virtual plane by a predetermined distance on the other side (the side opposite to the contact portion C1). For example, the contact portion C1 and the contact portion C3 are disposed so as to be plane symmetric with respect to the virtual plane. In such a configuration, there is a case where the swash plate <NUM> is inclined in a direction different from the swing direction. For example, the swash plate <NUM> may be inclined around an axis orthogonal to the rotation center axis O1 and the swing center axis O2.

In contrast, in the present embodiment, since the contact portion C1, the contact portion C2, and the contact portion C3 are disposed on the same plane, it is possible to prevent the swash plate <NUM> from inclining in a direction different from the swing direction. As a result, the hysteresis of the tilt angle of the swash plate <NUM> between increasing the tilt angle and decreasing the tilt angle, which is set in accordance with the control pressure Pc, can be reduced. Further, in the present embodiment, since the small-diameter piston <NUM> and the large-diameter piston <NUM> sandwich the swash plate <NUM> on the same straight line, vibration of the swash plate <NUM> can be suppressed as compared with the comparative example. Thus, in the present embodiment, since the control hysteresis is reduced and the vibration of the swash plate <NUM> can be suppressed, the tilt control of the swash plate <NUM> can be performed more stably. As a result, the discharge rate of the piston pump <NUM> is more stable.

Furthermore, in the present embodiment, the small-diameter piston <NUM> presses the back surface of the swash plate <NUM> by the pressure of the pressure chamber <NUM>. Therefore, since the load applied to the tilt bearing <NUM> can be reduced as compared with a case where the small-diameter piston <NUM> presses the front surface of the swash plate <NUM>, damage to the tilt bearing <NUM> can be effectively prevented.

According to the above-described embodiment, the following operational effects can be achieved.

In the present embodiment, a small-diameter piston <NUM> as the tilt control piston is slidably supported by the stopper <NUM> mounted to the cover 3b constituting the case <NUM>. Since the stopper <NUM> is smaller in size than the cover 3b, it is possible to easily perform surface treatment such as heat treatment. Therefore, it is possible to easily improve the wear resistance of the sliding surface <NUM> which the small-diameter piston <NUM> slides. Thus, since it is possible to maintain good slidability of the small-diameter piston <NUM> for a long period, it is possible to maintain good performance of the piston pump <NUM> for a long period.

The described hydraulic rotating machine can be modified as defined in the following modifications; however, the invention is defined by the appended claims.

<Modification <NUM>> In the above embodiment, an example in which the piston receiving member <NUM> is provided between the swash plate body <NUM> and the small-diameter piston <NUM> has been described. However, the piston receiving member <NUM> may be omitted. In this case, the swash plate body <NUM> abuts the stopper <NUM> directly, and thereby, the minimum tilt angle is defined. Further, the swash plate body <NUM> is directly pressed by the small-diameter piston <NUM> in a direction in which the tilt angle increases.

<Modification <NUM>> In the above embodiment, an example in which the contact portion C1, the contact portion C2, and the contact portion C3 are located on the same plane has been described. However, for example, the contact portion C2 may be disposed on an virtual plane orthogonal to the rotation center axis O1 and the swing center axis O2, and the contact portion C1 and the contact portion C3 may be disposed so as to be plane symmetric with respect to the virtual plane.

<Modification <NUM>> In the above embodiment, an example in which the small-diameter piston <NUM> for biasing the swash plate <NUM> by the discharge pressure P1 of the piston pump <NUM> is slidably supported by the stopper <NUM> has been described. However, the tilt control piston for biasing the swash plate <NUM> by the control pressure Pc may be slidably supported by the stopper <NUM>.

The configuration, operation, and effect of the embodiment configured as described above will be collectively described.

The hydraulic rotating machine (the piston pump <NUM> and piston motor) includes the case <NUM>, the cylinder block <NUM> housed in the case <NUM> and having a plurality of cylinders 2b, the piston <NUM> reciprocatively inserted into the cylinder 2b, the swash plate <NUM> configured to reciprocate the piston <NUM> as the cylinder block <NUM> rotates, the tilt control piston (small-diameter piston <NUM>) configured to biase the swash plate <NUM> and control the tilt angle of the swash plate <NUM>, and the stopper <NUM> which is mounted to the case <NUM> and configured to define the minimum tilt angle of the swash plate <NUM>. The stopper <NUM> has a sliding surface <NUM> for slidably supporting the tilt control piston (small-diameter piston <NUM>).

In this configuration, the tilt control piston (small-diameter piston <NUM>) is slidably supported by the stopper <NUM> mounted to the case <NUM>. Since the stopper <NUM> is smaller in size than the case <NUM>, it is possible to easily perform surface treatment such as heat treatment. Therefore, it is possible to easily improve the wear resistance of the sliding surface <NUM> which the tilt control piston (small-diameter piston <NUM>) slides.

In the hydraulic rotating machine (the piston pump <NUM> and the piston motor), the swash plate <NUM> includes the swash plate body <NUM> and the piston receiving member <NUM> attached to the swash plate body <NUM> and having the sliding contact surface <NUM> which the tilt control piston (the small-diameter piston <NUM>) is in sliding contact with.

In this configuration, the tilt control piston (the small-diameter piston <NUM>) is in sliding contact with the piston receiving member <NUM> attached to the swash plate body <NUM>. Since the piston receiving member <NUM> is smaller in size than the swash plate body <NUM>, it is possible to easily perform surface treatment such as heat treatment. Therefore, it is possible to easily improve the wear resistance of the sliding contact surface <NUM> which the tilt control piston (small-diameter piston <NUM>) is in sliding contact with.

Claim 1:
A hydraulic rotating machine (<NUM>) comprising:
a case (<NUM>);
a cylinder block (<NUM>) housed in the case (<NUM>) and having a plurality of cylinders (2b);
a piston (<NUM>) reciprocatively inserted into each of the cylinders (2b);
a swash plate (<NUM>) configured to reciprocate the pistons (<NUM>) as the cylinder block (<NUM>) rotates;
a tilt control piston (<NUM>) configured to bias the swash plate (<NUM>) and control a tilt angle of the swash plate (<NUM>); and
a stopper (<NUM>) mounted to a mounting hole (<NUM>) formed in the case (<NUM>), the stopper (<NUM>) and the cylinder block (<NUM>) being respectively located on opposite sides of the swash plate (<NUM>), the stopper (<NUM>) being configured to define a minimum tilt angle of the swash plate (<NUM>), wherein the stopper (<NUM>) has an abutting portion (<NUM>) which abuts the swash plate (<NUM>),
characterized in that
the stopper (<NUM>) has a through hole with a sliding surface (<NUM>) provided at an inner circumference thereof for slidably supporting the tilt control piston (<NUM>).