Axial piston device

Abstract

In the axial piston device of the present invention, the hydraulic servo mechanism includes: a servo piston that is housed in a servo space in such a manner as to liquid-tightly define first and second oil chambers and be reciprocally movable in the axial direction; a connecting arm that causes a swash plate to tilt and rotate about a swing axis according to the movement of the servo piston in the axial direction; a pressure oil line that receives pressure oil from a hydraulic source; first and second supply / discharge lines that are fluidly connected to the first and second oil chambers, respectively; a discharge line; a switching valve group that switches the connection state of the hydraulic lines, including a first valve shaft that is housed in a setting hole in a liquid-tight and axially rotatable manner and a second valve shaft that is housed in an axial hole of the first valve shaft in an axially rotatable manner, one and the other of the valve shafts serving as an input valve shaft and a feedback valve shaft, respectively; and a feedback arm that causes the feedback valve shaft to rotate about the axis according to the operation of the connecting arm.

Description

Technical Field

[0001] The present invention relates to an axial piston device including an axial piston member, a movable swash plate that changes the volume of the axial piston member, and a hydraulic servo mechanism that generates an operating force for tilting and rotating the movable swash plate. Background Art

[0002] In an axial piston device including an axial piston member and a movable swash plate that changes the volume of the axial piston member according to the tilting and rotating position around a swing axis, a structure including a hydraulic servo mechanism that generates an operating force for tilting and rotating the movable swash plate around the swing axis has been proposed and is being used (Japanese Patent Laid-Open No. 2015-055180).

[0003] The axial piston device having the above structure is useful in that it can reduce the manual operating force required to tilt and rotate the movable swash plate.

[0004] However, there is room for improvement in the miniaturization and simplification of the hydraulic servo mechanism in the conventional axial piston device. Summary of the Invention

[0005] The present invention has been completed in view of the above prior art, and an object thereof is to provide an axial piston device including a hydraulic servo mechanism that generates an operating force for tilting and rotating a movable swash plate and capable of achieving miniaturization and simplification of the hydraulic servo mechanism.

[0006] The present invention provides an axial piston device as follows to achieve the above object. The axial piston device includes: a housing; a rotating shaft supported by the housing so as to be rotatable about an axis; an axial piston member housed in the housing while being supported by the rotating shaft in a non-rotatable relative manner; a movable swash plate that changes the volume of the axial piston member according to the tilt rotation position about a swing axis; and a hydraulic servo mechanism that generates an operating force for tilting and rotating the movable swash plate about the swing axis. The hydraulic servo mechanism includes: a servo piston housed in a state of hermetically defining a first oil chamber and a second oil chamber at one end side and the other end side in the length direction of a servo space formed in the housing, moving in a first axial direction by supplying pressure oil to the first oil chamber and discharging pressure oil from the second oil chamber, and moving in a second axial direction by supplying pressure oil to the second oil chamber and discharging pressure oil from the first oil chamber; a connecting arm that tilts and rotates the movable swash plate about the swing axis in a first direction and a second direction respectively according to the movement of the servo piston in the first and second axial directions; a pressure oil pipeline that receives pressure oil from a hydraulic source; first and second supply / discharge pipelines fluidly connected to the first and second oil chambers respectively; a discharge pipeline; a switching valve group that switches the connection states of the pressure oil pipeline, the first supply / discharge pipeline, the second supply / discharge pipeline, and the discharge pipeline, including a first valve shaft housed in a setting hole formed in the housing in a hermetic and axis-rotatable manner and a second valve shaft housed in an axis hole of the first valve shaft in an axis-rotatable manner, one of the first and second valve shafts acting as an input valve shaft and the other of the first and second valve shafts acting as a feedback valve shaft; and a feedback arm that relatively rotates the feedback valve shaft about the axis with respect to the input valve shaft according to the movement of the connecting arm.

[0007] According to the axial piston device of the present invention, it is possible to pursue the miniaturization and simplification of the hydraulic servo mechanism that generates the operating force for tilting and rotating the movable swash plate as much as possible.

[0008] In one mode, an inflow port fluidly connected to the pressure oil pipeline and first and second connection ports fluidly connected to the first and second supply / discharge pipelines respectively are provided in the setting hole, and the discharge pipeline has a discharge oil passage formed in the second valve shaft.

[0009] In the first valve shaft, an inflow opening, a first connection opening, and a second connection opening that communicate the inflow port, the first connection port, and the second connection port with the axis hole of the first valve shaft respectively are provided at different positions in the circumferential direction.

[0010] The second valve shaft has, at circumferentially different positions, a discharge region formed by an opening of an inlet end portion of the discharge oil passage, an oil passage region capable of selectively fluid-connecting the inflow port to the first and second connection ports, and first and second closing regions capable of closing the first and second connection ports, respectively.

[0011] In this case, when the input valve shaft rotates about the axis in one of the first and second directions relative to the feedback valve shaft, a working state occurs in which "the inflow port is fluid-connected only to one of the first and second connection ports via the oil passage region and the other of the first and second connection ports is fluid-connected to the inlet end portion of the discharge pipe via the discharge region, and the servo piston moves in the corresponding axial direction". On the other hand, when the feedback valve shaft rotates relative to the input valve shaft about the axis via the feedback arm according to the axial movement of the servo piston, a holding state occurs in which "the first and second connection ports are closed by the first and second closing regions, respectively, and the servo piston is held in position in the axial direction".

[0012] In the one aspect, preferably, the first valve shaft has: an intermediate arc region, which is circumferentially located between the first and second connection openings and is capable of making a liquid-tight sliding contact with the inner peripheral surface of the installation hole between the first and second connection ports; a first arc region, which extends circumferentially from the intermediate arc region via the first connection opening toward the side closer to the inflow opening and is capable of making a liquid-tight sliding contact with the inner peripheral surface of the installation hole between the first connection port and the inflow port; and a second arc region, which extends circumferentially from the intermediate arc region via the second connection opening toward the side closer to the inflow opening and is capable of making a liquid-tight sliding contact with the inner peripheral surface of the installation hole between the second connection port and the inflow port.

[0013] In the one aspect, preferably, the discharge region is circumferentially located between the first and second closing regions, and the discharge oil passage is configured to release the discharge oil flowing in from the inlet end portion into the internal space of the housing.

[0014] In the various structures, the housing includes: a first end wall portion that supports a first end portion of the rotary shaft, which is closer to the swash plate main body than the axial piston member, so as to be rotatable about the axis; a second end wall portion that supports a second end portion of the rotary shaft, which is opposite to the first end portion, so as to be rotatable freely about the axis; and a peripheral wall portion that connects the peripheries of the first and second end wall portions to each other. An axial opening for supporting the swash plate shaft of the movable swash plate and a radial opening for opening the axial opening to the outside are provided in the peripheral wall portion.

[0015] In this case, preferably, the housing further includes a cover body detachably mounted on the peripheral wall portion so as to close the radial opening, and the switching valve group can be supported by the cover body.

[0016] Preferably, the servo space is provided at a corner of the housing connected to the first end wall near a region of the peripheral wall portion where the radial opening is provided so that the longitudinal direction is orthogonal to both the axis of the rotating shaft and the swing axis.

[0017] Preferably, the setting hole is formed on the cover body in a manner that the axis is parallel to the swing axis of the movable inclined plate, the feedback arm is connected to the feedback valve shaft at the base end side in a manner that is non-rotatable around the axis and the free end side extends in a direction orthogonal to the axis of the switching valve group, and the connecting arm is connected to the shaft portion of the movable inclined plate at the base end side in a manner that is non-rotatable around the axis and the free end side is engaged with the servo piston, extending in a direction orthogonal to the swing axis of the movable inclined plate.

[0018] In this case, the feedback arm and the connection arm are operatively connected via a concave-convex structure that can be engaged and disengaged according to attachment and detachment of the cover body with respect to the peripheral wall portion.

[0019] For example, the shell may include: a shell integrally including the first end wall portion and the peripheral wall portion, wherein the side of the peripheral wall portion opposite to the first end wall portion is set as an opening; and a sealing member (English: port block) which is detachably connected to the shell in a manner of closing the opening to form the second end wall portion.

[0020] In the embodiment in which the housing has the cover body, it is preferable to provide a reference position urging mechanism for urging the input valve shaft toward a reference position around the axis line.

[0021] The reference position urging mechanism comprises: a reference position arm, which extends in a direction orthogonal to the input valve axis in a state where the base end side is connected to the input valve axis in a manner that is non-rotatable relative to the axis; a locking pin, which is erected on the reference position arm in a manner parallel to the swing axis; a reference position piston, which is accommodated in a accommodating space formed on the cover body in a manner that makes the length direction orthogonal to the swing axis so as to be able to move back and forth in the length direction, and for the free end of the locking pin to be engaged; and a reference position urging member, which urges the reference position piston toward a length direction reference position corresponding to the reference position of the input valve axis around the axis.

[0022] In the first embodiment, the first valve shaft and the second valve shaft respectively function as the feedback valve shaft and the input valve shaft, and the second valve shaft is configured such that an operation input portion that can be manually operated is formed at an outer end portion thereof.

[0023] In the second embodiment, the first valve shaft and the second valve shaft respectively function as the input valve shaft and the feedback valve shaft, and the first valve shaft is configured such that the axial hole into which the second valve shaft is inserted opens at an inner end surface and an operation input portion that can be manually operated is formed at an outer end portion thereof.

[0024] In the third embodiment, the axial piston device can further include: an operation member that is manually operated; an operation sensor that detects an operation state of the operation member; a hydraulic operation mechanism that rotates the input valve shaft about an axis; and a control device that controls the operation of the hydraulic operation mechanism.

[0025] The hydraulic operation mechanism includes: an operation arm that extends in a direction orthogonal to the input valve shaft in a state where a proximal end side thereof is connected to the input valve shaft so as not to be relatively rotatable about the axis; an operation piston that is accommodated in the accommodation space of the housing in a state where first and second operation oil chambers are respectively defined in a liquid-tight manner at one end side and the other end side in the length direction of the accommodation space such that a length direction thereof is orthogonal to a swing axis, and moves in a first length direction by supplying pressure oil to the first operation oil chamber and discharging pressure oil from the second operation oil chamber and moves in a second length direction by supplying pressure oil to the second operation oil chamber and discharging pressure oil from the first operation oil chamber; a connection member that operatively connects the operation piston and the operation arm such that the input valve shaft rotates about the axis in the first and second directions respectively according to the movement of the operation piston in the first and second length directions; first and second operation biasing members that are respectively disposed so as to sandwich the operation piston in the first and second input oil chambers; an operation pressure oil line that receives pressure oil from a hydraulic source; an operation discharge line; and first and second electromagnetic proportional valves that respectively switch the supply and discharge of pressure oil to and from the first and second operation oil chambers.

[0026] The first and second electromagnetic proportional valves are configured to be able to assume a pressure oil supply state in which a corresponding operation oil chamber is cut off from the operation discharge line and connected to the operation pressure oil line, a holding state in which a corresponding operation oil chamber is cut off from both the operation pressure oil line and the operation discharge line, and a pressure oil discharge state in which a corresponding operation oil chamber is cut off from the operation pressure oil line and connected to the operation discharge line.

[0027] The control device controls the operation of the first and second electromagnetic proportional valves based on a signal from the operation sensor so that the input valve shaft is positioned around the axis corresponding to the operation state of the operation member.

[0028] In the third aspect, for example, the first and second electromagnetic proportional valves can include: a main body having a drive part; and a spool that is housed in the main body so as to be able to move forward and backward in the axial direction so that an initial position where the holding state appears, a protruding position where the pressure oil supply state appears, and a storage position where the pressure oil discharge state appears can be taken.

[0029] The drive part is configured to take an ON state in which the spool is forcibly pushed in the protruding direction based on a control signal from the control device so that the spool is in the protruding position, and an OFF state in which substantially no driving force is applied to the spool. The spool has an oil chamber side pressure receiving part that receives the pressure of the operation oil chamber and generates a storage direction driving force that pushes the spool in the storage direction, and is configured to take the initial position when the pressure in the operation oil chamber is substantially zero and is in a balanced state with the operation discharge pipeline in the OFF state of the drive part, and take the storage position when the storage direction driving force exceeds the pressure of the operation discharge pipeline in the oil chamber hydraulic pressure generation state.

[0030] In this case, preferably, the drive part can have a pin that abuts against the base end surface of the spool in the ON state and pushes the spool in the protruding direction. The drive part is configured to apply a force to the pin toward the base end surface of the spool in the OFF state so as to allow the spool to take the initial position in the balanced state and the spool to take the storage position in the oil chamber hydraulic pressure generation state and maintain the abutting state of the pin with the base end surface of the spool. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a hydraulic circuit diagram of the axial piston device according to Embodiment 1 of the present invention.

[0032] Figure 2 is a cross-sectional view of the axial piston device according to Embodiment 1.

[0033] Figure 3 is along Figure 2 a cross-sectional view taken along line III-III in

[0034] Figure 4 is along Figure 2 a cross-sectional view taken along line IV-IV in

[0035] Figure 5 is Figure 3 an enlarged view of part V in

[0036] Figure 6 is a cross-sectional view along Figure 5 the VI-VI line in

[0037] Figure 7 is a cross-sectional view along Figure 5 the VII-VII line in

[0038] Figure 8 is an exploded perspective view of the main components of the hydraulic servo mechanism and the first swash plate in the axial piston device of the first embodiment

[0039] Figure 9 is a partial cross-sectional view corresponding to Figure 6 showing the state in which the second valve shaft is operated in the first direction around the axis relative to the first valve shaft

[0040] Figure 10 is a partial cross-sectional view corresponding to Figure 9 showing the state after the servo piston is pushed in the first axis direction

[0041] Figure 11 is a partial cross-sectional view of the axial piston device of the first embodiment of the present invention, and is a partial cross-sectional view corresponding to Figure 5 in the first embodiment

[0042] Figure 12 is a cross-sectional view along Figure 11 the XII-XII line in, and is a cross-sectional view corresponding to Figure 6 the first embodiment

[0043] Figure 13 is a cross-sectional view corresponding to Figure 12 showing the state in which the first valve shaft is operated in the first direction around the axis relative to the second valve shaft

[0044] Figure 14 is a partial cross-sectional view corresponding to Figure 13 showing the state after the servo piston is pushed in the first axis direction

[0045] Figure 15 is a hydraulic circuit diagram of the axial piston device of the third embodiment of the present invention

[0046] Figure 16 is a partial cross-sectional view of the axial piston device of the third embodiment, and is a partial cross-sectional view corresponding to Figure 5 in the first embodiment

[0047] Figure 17 is a cross-sectional view along Figure 16The cross-sectional view taken along line XVII-XVII in [the figure] is the corresponding cross-sectional view of Embodiment 1 Figure 6

[0048] Figure 18 is Figure 17 an enlarged view of part XVIII in [the figure], Figure 18 where (a) to (c) respectively show the states of the spool of the electromagnetic proportional valve at the initial position, the protruding position, and the storage position. Detailed Embodiment

[0049] Embodiment 1

[0050] Hereinafter, an embodiment of the axial piston device of the present invention will be described with reference to the drawings.

[0051] Figure 1 and Figure 2 respectively show a hydraulic circuit diagram and a cross-sectional view of the axial piston device 1A of the present embodiment.

[0052] In addition, Figure 3 and Figure 4 respectively show cross-sectional views taken along line III-III and line IV-IV in [the figure]. Figure 2

[0053] Moreover, Figure 5 shows Figure 3 an enlarged view of part V in [the figure].

[0054] In addition, Figure 6 and Figure 7 respectively show cross-sectional views taken along line VI-VI and line VII-VII in [the figure]. Figure 5

[0055] As Figures 1 to 7 shown, the axial piston device 1A includes a housing 100, a first rotating shaft 30(1) rotatably supported by the housing 100 about an axis, a first axial piston member 40(1) housed in the housing 100 while being supported by the first rotating shaft 30(1) in a non-rotatable relative manner, a movable first swash plate 50(1) that changes the volume of the first axial piston member 40(1) according to the tilting rotation position about a swing axis, and a hydraulic servo mechanism 500 that generates an operating force for tilting and rotating the first swash plate 50(1) about the swing axis.

[0056] The axial piston device 1A of the present embodiment is configured as a hydrostatic continuously variable transmission (hereinafter referred to as HST).

[0057] ​​​That is, the axial piston device 1A further includes a second rotary shaft 30(2) rotatably supported about an axis by the housing 100, a second axial piston member 40(2) housed in the housing 100 while being non-rotatably supported by the second rotary shaft 30(2), and a second swash plate 50(2) that defines the volume of the second axial piston member 40(2).

[0058] In addition, of course, the axial piston device of the present invention is not limited to the above-described manner, and is applicable to various manners such as a hydraulic pump device having a single or multiple hydraulic pumps.

[0059] In the present embodiment, the first axial piston member 40(1) functions as a hydraulic pump, the second axial piston member 40(2) functions as a hydraulic motor, and the first and second axial piston members 40(1) and 40(2) are fluidly connected by a pair of first and second working oil pipelines 200a and 200b.

[0060] The first rotary shaft 30(1) functions as a pump shaft whose one end can be operatively connected to a drive source (not shown), and the second rotary shaft 30(2) functions as a motor shaft whose one end can output rotational power to the outside.

[0061] In the present embodiment, the first and second rotary shafts 30(1) and 30(2) are arranged parallel to each other.

[0062] As Figure 1 and Figure 2 shown, the second swash plate 50(2) is a fixed type, and the volume of the second axial piston member 40(2) that functions as the hydraulic motor is fixed.

[0063] Of course, the second swash plate 50(2) can also be a movable type.

[0064] The housing 100 has a first end wall portion 110 that supports a first end portion 31(1) of the first rotary shaft 30(1) closer to the swash plate main body 55(1) side of the first axial piston member 40(1) than the first axial piston member 40(1) so as to be rotatable about the axis, a second end wall portion 112 that supports a second end portion 32(1) of the first rotary shaft 30(1) on the side opposite to the first end portion 31(1) so as to be rotatable about the axis, and a cylindrical peripheral wall portion 115 that connects the peripheries of the first and second end wall portions 110 and 112 to each other.

[0065] In addition, in the present embodiment, the second end portion 32(1) of the first rotary shaft 30(1) functions as an input end portion for operatively inputting rotational power from the drive source.

[0066] As described above, in the present embodiment, the second rotation shaft 30(2) is arranged in parallel with the first rotation shaft 30(1).

[0067] Therefore, the first end portion 31(2) of the second rotation shaft 30(2) that is closer to the second swash plate 50(2) than the second axial piston member 40(2) is supported by the first end wall portion 110 so as to be rotatable about the axis, and the second end portion 32(2) of the second rotation shaft 30(2) on the side opposite to the first end portion 31(2) is supported by the second end wall portion 112 so as to be rotatable about the axis.

[0068] In the present embodiment, the second end portion 32(2) of the first rotation shaft 30(1) functions as an output end portion for outputting the rotational power of the hydraulic motor.

[0069] In the present embodiment, as Figure 2 and Figure 3 shown, etc., the housing 100 has: a housing body 120, integrally having the first end wall 110 and the peripheral wall portion 115, and the side of the peripheral wall portion 115 opposite to the first end wall 110 is provided with an axial direction opening allowing the insertion of the first and second axial piston members 40(1) and 40(2); and a sealing member 130, detachably connected to the housing body 120 in a manner to close the axial direction opening to form the second end wall portion 112.

[0070] In the sealing member 130, a pair of first and second working oil passages 210a and 210b for forming the pair of first and second working oil pipelines 200a and 200b are formed.

[0071] The first axial piston member 40(1) has a cylinder block 42(1) supported on the first rotation shaft 30(1) in a non-rotatable manner and having a plurality of cylinder bores arranged around the axis of the first rotation shaft 30(1), and a plurality of pistons 45(1) received in the plurality of cylinder bores in a reciprocating manner and having free ends engaged with the swash plate body 55(1) of the first swash plate 50(1).

[0072] In addition, the second axial piston member 40(2) has a substantially same structure as the first axial piston member 40(1).

[0073] Therefore, for the second axial piston member 40(2), the same reference numerals are used by changing the last digit (1) of the reference numeral of the first axial piston member 40(1) to (2), and its description is appropriately omitted.

[0074] The end face of the cylinder block 42(1) on the side opposite to the corresponding first swash plate 50(1) in the axial direction abuts against the sealing member 130 via the distribution valve plate.

[0075] The side of the cylinder bore close to the corresponding first swash plate 50(1) is provided with an opening allowing the reciprocating movement of the piston 45(1), and on the side opposite to the corresponding first swash plate 50(1) in the axial direction, it is fluidly connected to the pair of working oil passages 210a, 210b via the distribution valve plate.

[0076] The first swash plate 50(1) which is a movable swash plate has: a swash plate shaft 51(1) supported by the housing 100 so as to be rotatable about the swing axis; and a swash plate body 55(1) which is inclined and rotated about the swing axis according to the rotation of the swash plate shaft 51(1) about the axis, and the free ends of the plurality of pistons 45(1) of the corresponding first axial piston member 40(1) are engaged therewith.

[0077] As Figure 3 shown, in the present embodiment, a bearing portion 116 for supporting the swash plate shaft 51(1) is provided on the peripheral wall portion 115 of the housing 100, and the swash plate shaft 51(1) is supported by the bearing portion 116 via a bearing 59 so as to be rotatable about the axis.

[0078] In the present embodiment, as Figure 3 shown, the first swash plate 50(1) is provided as a trunnion - type swash plate having a first swash plate shaft 51a(1) on the input side of the tilting rotation operating force and a second swash plate shaft 51b(1) extending to the side opposite to the first swash plate shaft 51a(1) across the swash plate body 55(1) as the swash plate shaft 51(1).

[0079] Therefore, on the peripheral wall portion 115 of the housing 100, first and second bearing portions 116a, 116b for respectively supporting the first and second swash plate shafts 51a(1), 51b(1) are provided as the bearing portion 116.

[0080] Of course, the present invention is not limited to the above - described manner. As the first swash plate 50(1), a bracket - type swash plate capable of tilting and rotating about the swing axis in a state where the back surface on the side opposite to the piston engaging surface is in sliding contact with the first end wall portion 110 can also be used. In this case, the proximal end side of the link arm 520 described later is connected to one side surface of the bracket - type swash plate so as not to be relatively rotatable about the swing axis.

[0081] As Figure 3As shown, on the peripheral wall portion 115 of the housing 100, there is also provided a first radial opening 117 that opens the bearing portion (in this embodiment, the first bearing portion 116a) of the swash plate shaft on the input inclined rotation operation force side (in this embodiment, the first swash plate shaft 51a(1)) among the first and second swash plate shafts 51a(1) and 51b(1) for at least supporting the first swash plate 50(1) outward. The first radial opening 117 is closed by a first cover body 140a that is detachably assembled to the peripheral wall portion 115.

[0082] In addition, in this embodiment, as Figure 3 shown, on the peripheral wall portion 115 of the housing 100, in addition to the first radial opening 117a, there is also provided a second radial opening 117b that opens the bearing portion (in this embodiment, the second bearing portion 116b) of the swash plate shaft other than the input side swash plate shaft among the swash plate shafts for supporting the first swash plate 50(1) (in this embodiment, the second swash plate shaft 51b(1)) outward. The second radial opening 117b is closed by a second cover body 140b that is detachably assembled to the peripheral wall portion 115.

[0083] As Figure 1 and Figure 2 shown, etc., the axial piston device 1A of this embodiment further has an auxiliary pump unit 60 including an auxiliary pump 62 that is driven to rotate by the first rotating shaft 30(1).

[0084] The auxiliary pump unit 60 further has an auxiliary pump housing 65 that is connected to the housing 100 so as to surround the auxiliary pump 62.

[0085] As Figure 2 shown, in this embodiment, the first end portion 31(1) of the first rotating shaft 30(1) extends outward from the first end wall portion 110, and the auxiliary pump 62 is supported on the outward extending portion of the first end portion 31(1) of the first rotating shaft 30(1) in a non-rotatable manner.

[0086] The auxiliary pump housing 65 is connected to the first end wall portion 110 so as to surround the auxiliary pump 62.

[0087] In the auxiliary pump housing 65, there are provided a suction oil passage 66 having one end opening on the outer surface to form a suction port 66P and the other end fluidly connected to the suction side of the auxiliary pump 62, and a discharge oil passage 67 having one end fluidly connected to the discharge side of the auxiliary pump 62 and the other end opening on the outer surface to form a discharge port 67P.

[0088] As Figure 1 and Figure 2As shown, in the housing 100, in addition to the pair of first and second working oil passages 210a, 210b, there are also provided: a supply oil passage 220 having one end opening on the outer surface to form an inlet port 220P; a relief valve 225 for setting the hydraulic pressure of the supply oil passage 220; a charge oil passage 230 having one end fluidly connected to the supply oil passage 220 and branching into first and second branch oil passages 230a, 230b at a branch point 231, and the downstream end portions in the pressure oil flow direction of the first and second branch oil passages 230a, 230b are respectively fluidly connected to the first and second working oil passages 210a, 210b; and check valves 235 respectively inserted into the first and second branch oil passages 230a, 230b in such a manner as to allow the pressure oil to flow from the supply oil passage 220 into the corresponding working oil passages 210a, 210b and prevent reverse flow.

[0089] The inlet port 220P is connected to the discharge port 67P via an external pipe 222, and the pressure oil from the auxiliary pump 62 is supplied to the supply oil passage 220.

[0090] In the present embodiment, high-pressure relief valves 240 are respectively inserted into the first and second branch oil passages 230a, 230b in a state parallel to the check valves 235. When there is an abnormal high pressure in one of the working oil passages (for example, the first working oil passage 210a), the high-pressure relief valve 240 releases the pressure oil in the one working oil passage 210a to the other working oil passage 210b via the branch oil passage 230b connected to the other working oil passage 210b and the check valve 325 inserted into the branch oil passage 230b.

[0091] In addition, in one of the first and second branch oil passages 230a, 230b, a bypass oil passage 250 bypassing the check valve 235 inserted into the one branch oil passage and a throttle portion 252 inserted into the bypass oil passage 250 are provided.

[0092] The bypass oil passage 250 and the throttle portion 252 are provided to prevent the deterioration of the HST working efficiency and ensure the HST neutral range, and preferably, are provided in a branch oil passage (for example, the second branch oil passage 230b) fluidly connected to the working oil passage (for example, the second working oil passage 210b) on the high-pressure side during backward movement among the pair of first and second working oil passages 210a, 210b.

[0093] Figure 8 A disassembled perspective view showing the main constituent members of the hydraulic servo mechanism 500 and the first swash plate 50(1).

[0094] As Figures 1 to 8As shown, the hydraulic servo mechanism 500 includes a servo piston 510 that is housed in a servo space 505 formed in the housing 100 so as to be reciprocally movable, and a connecting arm 520 that connects the servo piston 510 to the first swash plate 50(1).

[0095] As Figure 3 , Figure 5 and Figures 7 to 8 shown, the servo piston 510 is housed in the servo space 505 in a state where a first oil chamber 506a and a second oil chamber 506b are respectively defined in a liquid-tight manner at one end side and the other end side in the length direction of the servo space 505, and moves in the first axis direction by supplying pressure oil to the first oil chamber 506a and discharging pressure oil from the second oil chamber 506b, and moves in the second axis direction by supplying pressure oil to the second oil chamber 506b and discharging pressure oil from the first oil chamber 506a.

[0096] As Figure 3 and Figure 5 shown, in the present embodiment, the servo space 505 is provided in a corner of the housing 100 that is connected to the first end wall portion 110 near a region of the peripheral wall portion 115 where the first radial opening 117a is provided in such a manner that the length direction is orthogonal to both the axis of the first rotating shaft 30(1) and the swing axis.

[0097] According to the above structure, it is possible to achieve miniaturization of the housing 100 as much as possible and form the servo space 505.

[0098] As Figure 3 , Figure 5 and Figure 8 shown, the connecting arm 520 connects the servo piston 510 to the input side swash plate shaft (the first swash plate shaft 51a(1)) of the first swash plate 50(1) in such a manner that the first swash plate 50(1) is inclined and rotated in the first and second directions around the swing axis according to the movement of the servo piston 510 in the first and second axis directions.

[0099] In the present embodiment, as Figure 7 and Figure 8 shown, the servo piston 510 has a first large-diameter portion 511a that is in contact with the inner peripheral surface of the servo space 505 in a liquid-tight and slidable manner with its end face facing the first oil chamber 506a, a second large-diameter portion 511b that is in contact with the inner peripheral surface of the servo space 505 in a liquid-tight and slidable manner with its end face facing the second oil chamber 506b, and a small-diameter portion 513 that is located between the first and second large-diameter portions 511a and 511b in the length direction.

[0100] In the present embodiment, a neutral biasing mechanism is provided that forcibly returns the servo piston 510 to the neutral position when there is no hydraulic supply to the oil chambers 506a and 506b due to engine stop or the like. As Figure 7 shown, in this embodiment, the servo piston 510 is formed in a hollow cylindrical shape, and a spring 510a that forms the neutral biasing mechanism is housed in the hollow portion of the servo piston 510. The servo piston 510 is suspended in the servo space 505 via the spring 510a from a support rod 510b assembled to the housing 100.

[0101] Regarding the link arm 520, the base end side is connected to the input side swash plate shaft of the first swash plate 55(1) (the first swash plate shaft 51a(1) in this embodiment) so as not to rotate relative to the axis, and the free end side is engaged with the small diameter portion 513 of the servo piston 510. Thus, the first swash plate 55(1) is tilted and rotated about the swing axis by the axial movement of the servo piston 510.

[0102] As Figure 1 and Figure 4 shown, the hydraulic servo mechanism 500 further includes a pressure oil line 530 that receives pressure oil from a hydraulic source, first and second supply / discharge lines 535a and 535b that are fluidly connected to the first and second oil chambers 506a and 506b respectively, a discharge line 540, and a switching valve group 600A that switches the connection states of the pressure oil line 530, the first supply / discharge line 535a, the second supply / discharge line 535b, and the discharge line 540.

[0103] As Figures 4 to 6 and Figure 8 shown, the switching valve group 600A has a first valve shaft 610A that is housed in a setting hole 105 formed in the housing 100 in a liquid-tight and rotatable manner about the axis, and a second valve shaft 620A that is housed in an internal axis hole of the first valve shaft 610A in a rotatable manner about the axis.

[0104] In the present embodiment, as Figure 4 and Figure 5 shown, the setting hole 105 is formed in the first cover body 140a such that the axis direction is parallel to the swing axis, and the switching valve group 600A is assembled to the first cover body 140a.

[0105] One of the first and second valve shafts 610A and 610B functions as an input valve shaft, and the other of the first and second valve shafts 610A and 610B functions as a feedback valve shaft.

[0106] Details of the switching valve group 600A will be described later.

[0107] The pressure oil pipeline 530 is configured to guide the pressure oil received from the hydraulic source to the inflow port 106 of the setting hole 105.

[0108] As Figure 1 and Figures 4 to 6 shown, in the present embodiment, the pressure oil pipeline 530 has a pressure oil pipeline 532 formed in the housing 100 such that one end is fluidly connected to the supply oil path 220 and the other end is fluidly connected to the inflow port 106. Specifically, in the present embodiment, the pressure oil pipeline 532 is formed in the housing 120, the sealing member 130, and the first cover body 140a.

[0109] In the present embodiment, the first and second supply / discharge pipelines 535a, 535b respectively have first and second supply / discharge oil paths 537a, 537b formed in the housing 100.

[0110] Specifically, as Figure 6 and Figure 7 shown, the first supply / discharge oil path 537a is formed in the housing 120 and the first cover body 140a such that one end is fluidly connected to the first connection port 107a of the setting hole 105 and the other end is fluidly connected to the first oil chamber 506a.

[0111] The second supply / discharge oil path 537b is formed in the housing 120 and the first cover body 140a such that one end is fluidly connected to the second connection port 107b of the setting hole 105 and the other end is fluidly connected to the second oil chamber 506b.

[0112] In the present embodiment, the discharge pipeline 540 has a discharge oil path 542 formed in the second valve shaft 620A.

[0113] As Figure 5 and Figure 6 shown, regarding the discharge oil path 542, the inlet end opens on the outer surface of the second valve shaft 520A and the outlet end opens to the internal space of the housing 100 through the first radial opening 117a.

[0114] The hydraulic servo mechanism 500 further has a feedback arm 550 that relatively rotates the feedback valve shaft (the first valve shaft 610A in the present embodiment) relative to the input valve shaft (the second valve shaft in the present embodiment) about the axis according to the movement of the link arm 520.

[0115] As Figure 5 and Figure 8As shown in the figure, in the present embodiment, with respect to the feedback arm 550, the proximal end side is connected to the inner end portion of the feedback valve shaft (the first valve shaft 610A in the present embodiment) in a state where it cannot rotate relative to the axis, and the free end side extends radially outward of the feedback valve shaft (the first valve shaft 610A).

[0116] Moreover, the feedback arm 550 and the connecting arm 520 are operatively connected via a concavo-convex structure 560 that can be engaged and disengaged according to the attachment and detachment of the first cover 140a with respect to the peripheral wall portion 115.

[0117] Specifically, as Figure 5 and Figure 8 shown, the concavo-convex structure 560 has a convex portion 562 provided at an intermediate portion between the proximal end side and the free end side of the connecting arm 520 so as to protrude outward in the radial direction with respect to the axis of the first rotation shaft 30(1), and a concave portion (opening) 564 provided in the feedback arm 550 so that the convex portion 562 can be engaged therewith.

[0118] By having the above structure, by assembling the first cover 140a in a state where the switching valve group 600A and the feedback arm 550 are assembled to the housing 100 in a state where the first swash plate 50(1), the connecting arm 520, and the servo piston 510 are assembled, the engaged state of the connecting arm 520 and the feedback arm 550 can occur.

[0119] Therefore, it is possible to improve the efficiency of the assembly operation of the axial piston device 1A.

[0120] In addition, of course, the concavo-convex structure 560 can also be deformed to have a convex portion (not shown) provided on the feedback arm 550 so as to protrude inward in the radial direction with respect to the axis of the first rotation shaft 30(1), and a concave portion (opening) (not shown) provided on the connecting arm 520 so that the convex portion can be engaged therewith.

[0121] Here, the detailed structure of the switching valve group 600A will be described.

[0122] As Figure 6 shown, and as described above, the inflow port 106 and the first and second connection ports 107a, 107b are provided in the setting hole 105 into which the first valve shaft 610A is inserted.

[0123] On the other hand, in the first valve shaft 610A, inflow openings 611, first connection openings 612a, and second connection openings 612b are provided at circumferentially different positions to communicate the inflow port 106, the first connection port 107a, and the second connection port 107b with the inner axis hole of the first valve shaft 610a, respectively.

[0124] In addition, in the present embodiment, as Figure 6 shown, the inflow openings 611 are provided at two circumferentially different positions.

[0125] As Figure 6 shown, in the second valve shaft 620A inserted into the first valve shaft 610A, an exhaust region 621 formed by an opening at the inlet end of the exhaust oil passage 542, an oil passage region 622 capable of selectively fluid-connecting the inflow port 106 with the first or second connection ports 107a, 107b, and first and second closing regions 623a, 623b capable of closing the first and second connection ports 107a, 107b, respectively, are provided at circumferentially different positions.

[0126] In the present embodiment, the second valve shaft 620A functions as an input valve shaft for inputting an inclined rotational operating force, and the first valve shaft 610A functions as a feedback valve shaft.

[0127] Specifically, as Figure 5 shown, etc., the first valve shaft 610A functioning as the feedback valve shaft is a cylindrical shaft with the inner axis hole being a through hole, and the second valve shaft 620A functioning as the input valve shaft has an outward extension portion 628A extending outward at the outer end in a state of being inserted into the first valve shaft 610A, and the outward extension portion 628A forms an operation input portion that can be manually operated.

[0128] Figure 6 The state is shown in which the second valve shaft 620A functioning as the input valve shaft is located at a reference position around the axis (for example, a neutral position where the neutral state of the HST appears) and the first swash plate 50(1) is located at a reference position around the swing axis (for example, a neutral position where the neutral state of the HST appears).

[0129] As Figure 6 shown, when the second valve shaft 620A and the first swash plate 50(1) are located at the reference positions, the first and second closing regions 623a, 623b close the first and second connection ports 107a, 107b, respectively, whereby the first swash plate 50(1) is held at the reference position.

[0130] Figure 9 Shown in connection withFigure 6 The corresponding partial cross-sectional view and the partial cross-sectional view of the state in which the second valve shaft 620A is operated in the first direction (counterclockwise in Figure 9 this case) around the axis relative to the first valve shaft 610A.

[0131] As Figure 9 shown, if the second valve shaft 620A is rotated around the axis by a predetermined amount in the first direction by the tilting rotation operating force, then via the oil passage region 622, the inflow port 106 is only fluidly connected to the first connection port 107a, which is the corresponding one of the first and second connection ports 107a and 107b, and via the discharge region 621, the second connection port 107b, which is the other of the first and second connection ports 107a and 107b, is fluidly connected to the inlet end of the discharge oil passage 542.

[0132] Thereby, the servo piston 510 is pushed in the corresponding first axis direction, causing the first swash plate 50(1) to tilt and rotate in the first direction around the corresponding swing axis.

[0133] In addition, Figure 9 the state before the servo piston 510 is about to be pushed in the first axis direction is shown.

[0134] Figure 10 The partial cross-sectional view corresponding to Figure 9 and the partial cross-sectional view of the state after the servo piston 510 is pushed in the first axis direction are shown.

[0135] If the servo piston 510 is moved in the first axis direction by a predetermined amount, the first swash plate 50(1) rotates by a predetermined amount in the first direction around the corresponding swing axis.

[0136] At this time, according to the movement of the servo piston 510 in the first axis direction by a predetermined amount, the first valve shaft 610A rotates around the axis in the corresponding direction (counterclockwise in Figure 10 this case) relative to the second valve shaft 620A via the connecting arm 520 and the feedback arm 550.

[0137] Thereby, as Figure 10 shown, a holding state of "the first and second connection ports 107a and 107b are respectively closed by the first and second closing regions 623a and 623b, the servo piston 510 is held at the position at this time in the axis direction, and the first swash plate 50(1) is held at the position at this time around the swing axis" appears.

[0138] The hydraulic servo mechanism 500 of the switching valve group 600A having the above structure can achieve miniaturization and simplification compared with the conventional structure, and can achieve cost reduction of the axial piston device 1A.

[0139] In the present embodiment, as Figure 6 and Figures 8 to 10 shown, the first valve shaft 610A has: an intermediate arc region 615, which is circumferentially located between the first and second connection openings 612a and 612b, and can slidably contact the inner peripheral surface of the setting hole 105 in a liquid-tight manner between the first and second connection ports 107a and 107b; a first arc region 616a, which extends from the intermediate arc region 615 toward the inflow opening 611 side via the first connection opening 612a in the circumferential direction, and can slidably contact the inner peripheral surface of the setting hole 105 in a liquid-tight manner between the first connection port 612a and the inflow port 611; and a second arc region 616b, which extends from the intermediate arc region 615 toward the inflow opening 611 side via the second connection opening 612b in the circumferential direction, and can slidably contact the inner peripheral surface of the setting hole 105 in a liquid-tight manner between the second connection port 612b and the inflow port 611.

[0140] According to the above structure, it is possible to achieve stabilization of the operation of the first valve shaft 610A around the axis.

[0141] The axial piston device 1A of the present embodiment further includes a reference position biasing mechanism 650 that biases the input valve shaft (the second valve shaft 620A in the present embodiment) toward the reference position around the axis.

[0142] The reference position around the axis of the input valve shaft is set, for example, as the neutral position where the neutral state of the HST appears.

[0143] As Figure 5 , Figure 6 and Figures 8 to 9 shown, the reference position biasing mechanism 650 has: a reference position arm 655, which extends in a direction orthogonal to the axis of the second valve shaft 620A in a state where the proximal end side is connected to the second valve shaft 620A so as not to be relatively rotatable around the axis; an engagement pin 660, which is erected on the reference position arm 655 in a direction parallel to the swing axis; a reference position piston 670, which is housed in a housing space formed in the first cover 140a so that the longitudinal direction is orthogonal to the swing axis and can reciprocate in the longitudinal direction, and the free end of the engagement pin 660 is engaged therewith; and a reference position biasing member 665, which biases the reference position piston 670 toward the longitudinal direction reference position corresponding to the reference position around the axis of the second valve shaft 620A.

[0144] In the present embodiment, as Figure 5 shown, the inner end portion of the second valve shaft 620A extends outward from the axial hole of the first valve shaft 610A, and the proximal end side of the reference position arm 655 is connected to the inner end portion of the second valve shaft 620A in a non-rotatable manner.

[0145] In the present embodiment, as Figure 6 shown, in the first cover 140a, a cavity 147 is formed such that the longitudinal direction is orthogonal to the swing axis and both ends are open, and the openings on one side and the other side in the longitudinal direction of the cavity 147 are closed by the first and second caps 148a, 148b, respectively.

[0146] The space defined by the cavity 147 and the first and second caps 148a, 148b forms the accommodation space.

[0147] The reference position piston 670 has first and second large-diameter portions 672a, 672b respectively located on one side and the other side in the longitudinal direction and in liquid-tight and slidable contact with the inner peripheral surface of the accommodation space, and a small-diameter portion 674 located between the first and second large-diameter portions 672a, 672b in the longitudinal direction. The reference position piston 670 is accommodated in the accommodation space in a state where a first input chamber 145a is defined between the end surface of the first large-diameter portion 672a and the first cap 148a and a second input chamber 145b is defined between the end surface of the second large-diameter portion 672b and the second cap 148b so as to be capable of reciprocating movement in the longitudinal direction. Each of the input chambers 145a, 145b is always open to the internal space of the housing 100 through a discharge hole (not shown) provided in the first cover 140a and through the first radial opening 117a.

[0148] The free end portion of the engagement pin 660 is engaged with an engagement groove defined by the small-diameter portion 674. According to the longitudinal movement of the reference position piston 670, the second valve shaft 620A is rotated about the axis via the engagement pin 660 and the reference position arm 655.

[0149] First and second position adjustment bolts 680a, 680b with changeable fixed positions in the longitudinal direction are provided in the first and second input chambers 145a, 145b, respectively.

[0150] In addition, the first and second position adjustment bolts 680a, 680b have the same structure.

[0151] Therefore, in the figure, for the second position adjustment bolt 680b, the same reference numeral as the first position adjustment bolt 680a with the end changed to b is marked, and its description is appropriately omitted.

[0152] Specifically, the first position adjustment bolt 680a has a threaded portion screwed with the first cap 148a at its outer end and a large-diameter head 682a at its inner end, and the fixed position in the length direction is changed according to the rotation around the axis.

[0153] In addition, reference numeral 684a in the figure is a fixing nut that is screwed with the threaded portion of the first position adjustment bolt 980a to fix the lengthwise position of the first position adjustment bolt 680a.

[0154] A first outer spring bracket 690a is provided on the outer end side of the portion of the first position adjustment bolt 680a located in the first input chamber 145a in a manner that does not allow relative movement in the length direction, and a first inner spring bracket member 692a is provided on the inner end side of the first position adjustment bolt 680a in a manner that allows relative movement in the length direction.

[0155] The first inner spring bracket member 692a is defined with a mobile end toward the inner end by engaging with the head 682a of the first position adjustment bolt 680a.

[0156] The reference position biasing member 665 has a first reference position biasing member 665a inserted in a compressed state between the first inner spring bracket member 692a and the first outer spring bracket member 690a, and a second reference position biasing member 665b inserted in a compressed state between the second inner spring bracket member 692b and the second outer spring bracket member 690b.

[0157] On the first large-diameter portion 672a of the reference position piston 670, a first outer axial hole with an inner diameter that allows the insertion of the first inner spring bracket member 692a is provided, and a first inner axial hole that extends inward in the axial direction from the first outer axial hole in a state of being reduced in diameter with a first stepped portion is provided.

[0158] The first inner axial hole is set to have an inner diameter that allows the insertion of the head 682a of the first position adjustment bolt 680a and prevents the insertion of the first inner spring bracket member 692a.

[0159] Here, when the piston 670 at the reference position is at the longitudinal reference position corresponding to the reference position around the axis of the second valve shaft 620A that functions as the input valve shaft, the first inner spring bracket member 692a that is biased in the direction of the second oil chamber 145b by the first reference position biasing member 665a engages with both the head 682a of the first position adjustment bolt 680a and the first step portion, and the second inner spring bracket member 692b that is biased in the direction of the first oil chamber 145a by the second reference position biasing member 665b engages with both the head 682b of the second position adjustment bolt 680b and the second step portion, and in this way, the longitudinal positions of the first and second position adjustment bolts 680a and 680b are set.

[0160] Therefore, in a non-operating state where the first axial piston member 40(1) is set to the operating state by the rotational drive of the first rotating shaft 30(1) but no tilting rotational operating force around the axis is applied to the second valve shaft 620A, the reference position piston 670 is located at the axial reference position by being clamped and fixed by the first and second reference position biasing members 665a and 665b, and the second valve shaft 620A is held at the reference position around the axis (for example, the neutral position). Thus, the reference state in which the suction side pressure and the discharge side pressure of the first axial piston member 40(1) have a predetermined difference is maintained (in this embodiment, it is the neutral state where the difference between the suction side pressure and the discharge side pressure is zero).

[0161] On the other hand, if an operating force is applied to the second valve shaft 620A and the second valve shaft 620A rotates around the axis from the reference position around the axis to one side, the reference position piston 670 compresses the corresponding one of the first and second reference position biasing members 665a and 665b and is pushed in the corresponding longitudinal direction at the same time.

[0162] At this time, the head (682a) of the position adjustment bolt (for example, the first position adjustment bolt 680a) on the side of the compressed biasing member (for example, the first reference position biasing member 665a) intrudes into the inner axis hole of the reference position piston (the first position adjustment bolt 680a).

[0163] And if the operating force applied to the second valve shaft 620A is released, the reference position piston 670 returns to the axial reference position by the acting force of the biasing member (for example, the first reference position biasing member 665a) compressed by the longitudinal movement of the reference position piston 670, and is held at the axial reference position by the first and second reference position biasing members 665a and 665b.

[0164] Embodiment 2

[0165] Hereinafter, while referring to the attached Figure 1 drawings, other embodiments of the axial piston device of the present invention will be described.

[0166] Figure 11 A partial cross-sectional view showing the axial piston device 1B of the present embodiment and a corresponding partial cross-sectional view in Embodiment 1. Figure 5

[0167] In addition, Figure 12 a cross-sectional view along line XII-XII in Figure 11 and a corresponding cross-sectional view in Embodiment 1 are shown. Figure 6

[0168] In addition, in the drawings, the same reference numerals are given to the same components as in Embodiment 1, and the description thereof is appropriately omitted.

[0169] The axial piston device 1B of the present embodiment has a switching valve group 600B instead of the switching valve group 600A compared with the axial piston device 1A of the first embodiment.

[0170] The switching valve group 600B has a first valve shaft 610B housed in the setting hole 105 in a liquid-tight manner and rotatable about the axis, and a second valve shaft 620B housed in the inner axis hole of the first valve shaft 610B rotatably about the axis. The first valve shaft 610B functions as an input valve shaft that rotates about the axis by an inclined turning operation force, and the second valve shaft 620B functions as a feedback valve shaft.

[0171] Specifically, as Figure 11 shown, the axis hole of the first valve shaft 610B opens at the inner end face. In addition, the outer end portion of the first valve shaft 610B extends outward from the housing 100 (the first cover body 140a) to form an outward extension portion 618B, and the outward extension portion 618B forms an operation input portion that can be manually operated.

[0172] One end portion of the second valve shaft 620B forms an extension portion that extends outward (inside the housing 100) from the axis hole of the first valve shaft 610B and is inserted into the axis hole in a rotatable manner about the axis.

[0173] In the present embodiment, the proximal end side of the feedback arm 550 is connected to the inner end side of the extension portion of the second valve shaft 620B in a non-rotatable manner relative to the axis.

[0174] In addition, the proximal end side of the reference position arm 655 is connected to the inner end side of the first valve shaft 610B in a non-rotatable manner relative to the axis. ​​

[0175] The switching valve group 600B operates as follows.

[0176] Figure 12 The state is shown where the first valve shaft 610B, which functions as the input valve shaft, is in a reference position around the axis (for example, a neutral position where the neutral state of the HST appears), and the first swash plate 50(1) is in a reference position around the swing axis (for example, a neutral position where the neutral state of the HST appears).

[0177] As Figure 12 shown, when the first valve shaft 610B and the first swash plate 50(1) are in the reference positions, the first and second closed regions 623a, 623b respectively close the first and second connection ports 107a, 107b. Thus, the first swash plate 50(1) is held in the reference position.

[0178] Figure 13 A partial cross-sectional view showing the state where the first valve shaft 610B is operated around the axis in a first direction (counterclockwise in Figure 13 ) relative to the second valve shaft 620B is shown.

[0179] As Figure 13 shown, if the first valve shaft 610B is rotated around the axis by a predetermined amount in the first direction by an inclined rotational operating force, the inflow port 106 is fluidly connected only to the first connection port 107a, which is the corresponding one of the first and second connection ports 107a, 107b, via the oil passage region 622 to supply pressure oil to the first oil chamber 506a, and the second connection port 107b, which is the other of the first and second connection ports 107a, 107b, is fluidly connected to the inlet end portion of the discharge oil passage 542 via the discharge region 621 to discharge pressure oil from the second oil chamber 506b.

[0180] Thereby, the servo piston 510 is pushed in the corresponding first axis direction, and the first swash plate 50(1) is inclined and rotated in the corresponding first direction around the swing axis.

[0181] In addition, Figure 13 A state before the servo piston 510 is about to be pushed in the first axis direction is shown.

[0182] Figure 14 A partial cross-sectional view showing the state where the servo piston 510 is pushed in the first axis direction is shown.

[0183] If the servo piston 510 is moved in the first axis direction by a predetermined amount, the first swash plate 50(1) is rotated by a predetermined amount in the corresponding first direction around the swing axis.

[0184] At this time, according to the movement of the servo piston 510 by a predetermined amount in the first axis direction, via the connecting arm 520 and the feedback arm 550, the second valve shaft 620B rotates in the corresponding direction (counterclockwise in Figure 14 this case) about the axis relative to the first valve shaft 610B.

[0185] Thereby, as Figure 14 shown, a holding state occurs where "the first and second connection ports 107a, 107b are respectively closed by the first and second closed regions 623a, 623b, the servo piston 510 is held at the position at this time in the axis direction, and the first swash plate 50(1) is held at the position at this time about the swing axis".

[0186] In the axial piston device 1B of the switching valve group 600B having the above structure, the same effects as those of the first embodiment can also be obtained.

[0187] Embodiment 3

[0188] Hereinafter, other embodiments of the axial piston device of the present invention will be described with reference to the drawings.

[0189] Figure 15 A hydraulic circuit diagram of the axial piston device 1C of the present embodiment is shown.

[0190] In addition, Figure 16 a partial cross-sectional view of the axial piston device 1C of the present embodiment and a corresponding partial cross-sectional view in the first embodiment are shown. Figure 5

[0191] Moreover, Figure 17 a cross-sectional view taken along line XVII-XVII in Figure 16 and a corresponding cross-sectional view in the first embodiment are shown. Figure 6

[0192] In addition, in the drawings, the same reference numerals are given to the same components as those in the first and second embodiments, and the description thereof is appropriately omitted.

[0193] In the first and second embodiments, an operation input portion that can be manually operated is formed at the outer end of the valve shaft (the second valve shaft 620A in the first embodiment and the first valve shaft 610B in the second embodiment) that functions as the input valve shaft among the first and second valve shafts 610A(610B), 620A(620B).

[0194] In contrast, the input valve shaft of the axial piston device 1C of the present embodiment rotates about the axis by the action of hydraulic pressure.​​

[0195] Specifically, compared with the first embodiment, the axial piston device 1C has a switching valve group 600C instead of the switching valve group 600A, and further includes an operation member 710 that is manually operated, an operation sensor 715 that detects the operation state of the operation member 710, a hydraulic operation mechanism 750 that rotates the input valve shaft about its axis, and a control device 700 that controls the operation of the hydraulic operation mechanism 750.

[0196] The switching valve group 600C is different from the switching valve group 600A in the first embodiment only in that the second valve shaft 620C that functions as an input valve shaft does not have a manually operable operation input portion.

[0197] Specifically, the switching valve group 600C has a first valve shaft 610A that is housed in the installation hole 105 in a liquid-tight manner and is rotatable about its axis, and a second valve shaft 620C that is housed in the inner axis hole of the first valve shaft 610A and is rotatable about its axis. The second valve shaft 620C functions as an input valve shaft for inputting the swash plate operating force, and the first valve shaft 620A functions as a feedback valve shaft.

[0198] The second valve shaft 620C is different from the second valve shaft 620A only in that it does not have the outward extension portion 628A.

[0199] In addition, Figure 16 The reference numeral 629C in is an engagement recess for manually operating the second valve shaft 620C that functions as an input valve shaft in the event of a failure of the hydraulic operation mechanism 750 or the like, and its cross-sectional shape is set to a non-circular shape such as a rectangle.

[0200] As Figures 15 to 17As shown, the hydraulic operating mechanism 750 includes: an operating arm 755 that extends in a direction orthogonal to the second valve shaft 620C in a state where the proximal end side is connected to the second valve shaft 620C so as not to be rotatable relative to the axis; an operating piston 770 that is accommodated in the accommodation space of the housing 100 in a state where the longitudinal direction is orthogonal to the swing axis and hermetically defines the first and second operating oil chambers 155a and 155b at one end side and the other end side in the longitudinal direction of the accommodation space, and moves in the first longitudinal direction by supplying pressure oil to the first operating oil chamber 155a and discharging pressure oil from the second operating oil chamber 155b, and moves in the second longitudinal direction by supplying pressure oil to the second operating oil chamber 155b and discharging pressure oil from the first operating oil chamber 155a; a connecting member 760 that operatively connects the operating piston 770 and the operating arm 755 in such a manner that the second valve shaft 620C, which functions as the input valve shaft according to the movement of the operating piston 770 in the first and second longitudinal directions, rotates about the axis in the first and second directions respectively; first and second operating biasing members 765a and 765b that are disposed in the first and second operating oil chambers 155a and 155b respectively so as to sandwich the operating piston 770; an operating pressure oil line 800 that receives pressure oil from a hydraulic source; an operating discharge line 810; and first and second electromagnetic proportional valves 820a and 820b that switch the supply and discharge of pressure oil to and from the first and second operating oil chambers 155a and 155b respectively.

[0201] In the present embodiment, the accommodation space that houses the operating piston 770 is formed in the first cover 140a in the same manner as the accommodation space that houses the reference position piston 670.

[0202] Specifically, as Figure 17 shown, in the first cover 140a, a cavity 157 is formed in such a manner that the longitudinal direction is orthogonal to the swing axis and both ends are open, and the openings on one side and the other side in the longitudinal direction of the cavity 157 are closed by first and second caps 158a respectively.

[0203] The space defined by the cavity 157 and the first and second caps 158a and 158b forms the accommodation space.

[0204] The operation piston 77 has a first and a second large-diameter portions 772a, 772b respectively located on one side and the other side in the longitudinal direction and in liquid-tight and slidable contact with the inner peripheral surface of the accommodation space, and a small-diameter portion 774 located between the first and second large-diameter portions 772a, 772b in the longitudinal direction. The operation piston 77 is accommodated in the accommodation space in a state where a first operation oil chamber 155a is defined between the end surface of the first large-diameter portion 772a and the first cap 158a and a second operation oil chamber 155b is defined between the end surface of the second large-diameter portion 772b and the second cap 158b, and is capable of reciprocating movement in the longitudinal direction.

[0205] In the present embodiment, the connection member 760 is provided as a snap pin that stands on the operation arm 755 in a direction parallel to the swing axis and whose free end is engaged with a snap groove defined by the small-diameter portion 774 of the operation piston 770.

[0206] In the present embodiment, as Figure 17 shown, the hydraulic operation mechanism 750 further has first and second position adjustment bolts 780a, 780b respectively disposed in the first and second operation oil chambers 155a, 115b in a manner capable of changing the fixed position in the longitudinal direction.

[0207] In addition, the first and second position adjustment bolts 780a, 780b have the same structure.

[0208] Therefore, in the figure, for the second position adjustment bolt 780b, the same reference numeral as the first position adjustment bolt 780a with the end changed to b is marked, and its description is appropriately omitted.

[0209] Specifically, the first position adjustment bolt 780a has a threaded portion screwed with the first cap 158a at the outer end and a large-diameter head 782a at the inner end, and the fixed position in the longitudinal direction is changed according to the rotation about the axis.

[0210] In addition, reference numeral 784a in the figure is a fixing nut that is screwed with the threaded portion of the first position adjustment bolt 780a to fix the longitudinal position of the first position adjustment bolt 780a.

[0211] A first outer spring bracket 790a is provided on the outer end side of the portion of the first position adjustment bolt 780a located in the first operation oil chamber 155a in a manner incapable of relative movement in the longitudinal direction, and a first inner spring bracket member 792a is provided on the inner end side of the first position adjustment bolt 780a in a manner capable of relative movement in the longitudinal direction.

[0212] The first inner spring bracket member 792a is defined with a mobile end toward the inner end side by engaging with the head 782a of the first position adjustment bolt 780a.

[0213] The first operating biasing member 765a is inserted in a compressed state between the first inner spring bracket member 792a and the first outer spring bracket member 790a, and the second operating biasing member 765b is inserted in a compressed state between the second inner spring bracket member 792b and the second outer spring bracket member 790b.

[0214] On the first large-diameter portion 772a of the operating piston 770, there are provided a first outer axial hole having an inner diameter into which the first inner spring bracket member 792a can be inserted, and a first inner axial hole extending inward in the axial direction from the first outer axial hole in a state of being reduced in diameter with a first stepped portion.

[0215] The first inner axial hole is set to have an inner diameter that allows the insertion of the head 782a of the first position adjustment bolt 780a and prevents the insertion of the first inner spring bracket member 792a.

[0216] Here, when the operating piston 770 is at a lengthwise reference position corresponding to the reference position around the axis of the second valve shaft 620C that functions as the input valve shaft, the first inner spring bracket member 792a biased toward the second operating oil chamber 155a by the first operating biasing member 765a engages with both the head 782a of the first position adjustment bolt 780a and the first stepped portion, and the second inner spring bracket member 792b biased toward the first operating oil chamber 155a by the second operating biasing member 765b engages with both the head 782b of the second position adjustment bolt 780b and the second stepped portion. In this way, the lengthwise positions of the first and second position adjustment bolts 780a and 780b are set.

[0217] Therefore, in a state where pressure oil is not supplied to the first and second operating oil chambers 155a and 155b, the operating piston 770 is located at the axial reference position by being clamped by the first and second operating biasing members 765a and 765b. Thus, the second valve shaft 620C is held at the reference position around the axis (for example, the neutral position).

[0218] Figure 18 (a) to (c) of Figure 17 shows an enlarged view of part XVIII in

[0219] As Figure 17 and Figure 18As shown in (a) to (c) thereof, the first electromagnetic proportional valve 820a includes a main body 825 having a drive portion and a valve spool 830 that is accommodated in the main body 825 so as to be able to advance and retreat in the axial direction and can take an initial position, a protruding position, and a storage position in the axial direction.

[0220] Figure 18 (a) to (c) thereof respectively show the states in which the valve spool 830 is located at the initial position, the protruding position, and the storage position.

[0221] In addition, the second electromagnetic proportional valve 820b has the same structure as the first electromagnetic proportional valve 820a. Therefore, the description of the first electromagnetic proportional valve 820a also applies to the second electromagnetic proportional valve 820b.

[0222] In the present embodiment, when the valve spool 830 is located at the protruding position, the initial position, and the storage position, corresponding pressure oil supply states in which the first operation oil chamber 155a is cut off from the operation discharge pipeline 810 and connected to the operation pressure oil pipeline 800 (see Figure 18 (b) thereof), corresponding holding states in which the first operation oil chamber 155a is cut off from both the operation pressure oil pipeline 800 and the operation discharge pipeline 810 (see Figure 18 (a) thereof), and corresponding pressure oil discharge states in which the first operation oil chamber 155a is cut off from the operation pressure oil pipeline 800 and connected to the operation discharge pipeline 810 (see Figure 18 (c) thereof) occur respectively.

[0223] The drive portion is configured to be able to take an ON state in which the valve spool 830 is forcibly pushed in the protruding direction to be located at the protruding position and an OFF state in which substantially no driving force is applied to the valve spool 830.

[0224] In addition, in the present embodiment, as shown in (a) to (c) of Figure 18 the drive portion of the first and second electromagnetic proportional valves 820a and 820b has a pin 827 that abuts against the base end surface of the valve spool 830 in the ON state and pushes the valve spool 830 in the protruding direction.

[0225] In the present embodiment, a gap L is formed between the base end surface of the valve spool 830 and the top end surface of the pin 827 that face each other, and it is configured to take the initial position or the storage position according to the relative hydraulic pressure difference between the corresponding first operation oil chamber 155a and the operation discharge pipeline 810 in the OFF state of the drive portion.

[0226] Specifically, as shown in Figure 18As shown in (a) to (c) thereof, the spool valve 830 has: an oil chamber side pressure receiving portion 831 that receives the pressure of the corresponding first operation oil chamber 155a and generates a storage direction driving force that pushes the spool valve 830 in the storage direction; and an oil hole 832 that selectively closes the corresponding first operation oil chamber 155a, connects to the operation pressure oil pipeline 800, and connects to the operation discharge pipeline 810 according to the axial position of the spool valve 830 (initial position ( Figure 18 of (a)), storage position ( Figure 18 of (c)), and protruding position ( Figure 18 of (b))).

[0227] That is, when the drive unit is in the ON state, the spool valve 830 makes a predetermined stroke of the clearance L + α by the driving force from the pin 827 and is forcibly located at the protruding position ( Figure 18 of (b)). On the other hand, when the drive unit is in the OFF state, when the pressure in the first operation oil chamber 155a is zero and is in a balanced state with the operation discharge pipeline 810, it takes the initial position ( Figure 18 of (a)), and when the storage direction driving force exceeds the pressure (zero) in the operation discharge pipeline 810 and the oil chamber hydraulic pressure generation state occurs, it takes the storage position ( Figure 18 of (c)).

[0228] The control device 700 controls the operation of the first and second electromagnetic proportional valves 820a and 820b such that the second valve shaft 620C that functions as the input valve shaft is located at a position around the axis corresponding to the operation state of the operation member 710 (signal from the operation sensor 715).

[0229] That is, if the operation member 710 is operated in the first operation direction by a predetermined amount, the control device 700 makes the first electromagnetic proportional valve 820a in the ON state and the second electromagnetic proportional valve in the OFF state for a predetermined time so that the operation piston 770 moves in the corresponding first length direction by a predetermined amount.

[0230] Thereby, pressure oil is supplied from the operation pressure oil pipeline 800 to the corresponding first operation oil chamber 155a, and the operation piston 770 moves in the first length direction.

[0231] At this time, the second operation oil chamber 155b is compressed by the movement of the operation piston 770 in the first length direction, the hydraulic pressure of the second operation oil chamber 155b rises, and the second operation oil chamber 155b becomes an oil chamber hydraulic pressure generation state.

[0232] As the hydraulic pressure in the second operation oil chamber 155b rises, the valve core 830 of the second electromagnetic proportional valve 820b, in which the drive unit is in the OFF state, is pushed from the initial position to the storage position, and the pressure oil in the second operation oil chamber 155b is discharged to the operation discharge pipeline 810.

[0233] Therefore, when the operation member 710 is operated in the first operation direction, the operation piston 770 moves a predetermined amount in the first length direction. As a result, the second valve shaft 620C, which functions as the input valve shaft via the operation arm 755 and the connection member 760, rotates a predetermined angle around the axis in the corresponding direction. On the other hand, when the operation member 710 is operated in the second operation direction, the operation piston 770 moves a predetermined amount in the second length direction and the second valve shaft 620C rotates a predetermined angle around the axis in the corresponding reverse direction.

[0234] In addition, the hydraulic operation mechanism 750 also functions as a reference position reset mechanism that resets the second valve shaft 620C, which functions as the input valve shaft, to the reference position (for example, the neutral position) around the axis when manually operating the second valve shaft 620C in the event of a hydraulic failure or the like.

[0235] In the axial piston device 1C having the above structure, the same effects as those in the first and second embodiments can also be obtained.

[0236] Preferably, when the operation member 710 is in the neutral position, a weak current is passed through the drive unit in such a manner that the valve cores 830 of both the first and second electromagnetic proportional valves 820a and 820b can take the storage position from the protruding position and maintain the contact state between the top surface of the pin 827 and the base end surface of the valve core 830, and a slight force is applied to the pin 827 toward the base end surface of the valve core 830 to eliminate the gap L.

[0237] According to the above structure, the responsiveness of the valve core 830 from the initial position to the protruding position when switching the drive unit from the OFF state to the ON state can be improved.

[0238] In addition, in the present embodiment, the second valve shaft 620C is set as the input valve shaft and the first valve shaft 620A is set as the feedback valve shaft. However, instead of this, the first valve shaft can be set as the input valve shaft and the second valve shaft can be set as the feedback valve shaft as in the second embodiment.

Claims

1. An axial piston device, comprising: a housing; a rotating shaft rotatably supported about an axis by the housing; an axial piston member housed in the housing while being supported by the rotating shaft in a non-rotatable relative manner; a movable swash plate that changes the volume of the axial piston member according to the tilt rotation position about a swing axis; and a hydraulic servo mechanism that generates an operating force for tilting and rotating the movable swash plate about the swing axis, wherein the axial piston device is characterized in that, the hydraulic servo mechanism includes: a servo piston housed in a state of fluid-tightly defining a first oil chamber and a second oil chamber at one end side and the other end side in the length direction of a servo space formed in the housing, moving in a first axial direction by supplying pressure oil to the first oil chamber and discharging pressure oil from the second oil chamber and moving in a second axial direction by supplying pressure oil to the second oil chamber and discharging pressure oil from the first oil chamber; a connecting arm that tilts and rotates the movable swash plate about the swing axis in a first direction and a second direction respectively according to the movement of the servo piston in the first axial direction and the second axial direction; a pressure oil pipeline that receives pressure oil from a hydraulic source; a first supply / discharge pipeline and a second supply / discharge pipeline that are fluid-connected to the first oil chamber and the second oil chamber respectively; a discharge pipeline; a switching valve group that switches the connection states of the pressure oil pipeline, the first supply / discharge pipeline, the second supply / discharge pipeline, and the discharge pipeline, including a first valve shaft housed in a setting hole formed in the housing in a fluid-tight and rotatable manner about an axis and a second valve shaft housed in an axis hole of the first valve shaft in a rotatable manner about an axis, one of the first valve shaft and the second valve shaft functions as an input valve shaft and the other of the first valve shaft and the second valve shaft functions as a feedback valve shaft; and a feedback arm that relatively rotates the feedback valve shaft about the axis with respect to the input valve shaft according to the action of the connecting arm, the housing includes: The first end wall portion supports the first end of the rotary shaft, which is closer to the swash plate body side of the axial piston member than the movable swash plate, so as to be rotatable about the axis; the second end wall portion supports the second end of the rotary shaft, which is on the side opposite to the first end, so as to be rotatable freely about the axis; and the peripheral wall portion connects the peripheries of the first end wall portion and the second end wall portion to each other. A bearing portion for supporting the swash plate shaft of the movable swash plate and a radial opening for opening the bearing portion outward are provided in the peripheral wall portion. The housing further includes a cover that is detachably assembled to the peripheral wall portion so as to close the radial opening. The switching valve group is supported by the cover. The setting hole is formed in the cover such that the axis is parallel to the swing axis of the movable swash plate. The feedback arm extends in a direction orthogonal to the axis of the switching valve group with the base end side connected to the feedback valve shaft in a state where it cannot rotate relative to the axis and the free end side. The connecting arm extends in a direction orthogonal to the swing axis of the movable swash plate with the base end side connected to the shaft portion of the movable swash plate in a state where it cannot rotate relative to the axis and the free end side engaged with the servo piston. The feedback arm and the connecting arm are operatively connected via a concavo-convex structure that can be engaged and disengaged according to the attachment and detachment of the cover with respect to the peripheral wall portion.

2. The axial piston device according to claim 1, characterized in that, An inflow port fluidly connected to the pressure oil pipeline, and a first connection port and a second connection port respectively fluidly connected to the first supply / discharge pipeline and the second supply / discharge pipeline are provided in the setting hole. The discharge pipeline has a discharge oil passage formed in the second valve shaft. In the first valve shaft, an inflow opening, a first connection opening, and a second connection opening for communicating the inflow port, the first connection port, and the second connection port with the axis hole of the first valve shaft respectively are provided at different positions in the circumferential direction. The second valve shaft has, at different positions in the circumferential direction, a discharge area where the inlet end opening of the discharge oil passage is formed, an oil passage area capable of selectively fluidly connecting the inflow port to the first connection port and the second connection port, and a first closing area and a second closing area capable of closing the first connection port and the second connection port respectively. If the input valve shaft rotates about the axis in one of the first direction and the second direction relative to the feedback valve shaft, the following working state occurs: the inflow port is fluidly connected to only one of the first connection port and the second connection port via the oil passage area, and the other of the first connection port and the second connection port is fluidly connected to the inlet end of the discharge pipeline via the discharge area, and the servo piston moves in the corresponding axial direction; on the other hand, if the feedback valve shaft rotates relative to the input valve shaft about the axis via the feedback arm according to the axial movement of the servo piston, the following holding state occurs: the first connection port and the second connection port are respectively closed by the first closing area and the second closing area, and the servo piston is held in position in the axial direction.

3. The axial piston device according to claim 2, characterized in that, The first valve shaft has: a middle arc region, which is circumferentially located between the first connection opening and the second connection opening and can slidably contact the inner peripheral surface of the setting hole in a liquid-tight manner between the first connection port and the second connection port; a first arc region, which extends from the middle arc region circumferentially via the first connection opening toward the inflow opening side and can slidably contact the inner peripheral surface of the setting hole in a liquid-tight manner between the first connection port and the inflow port; and a second arc region, which extends from the middle arc region circumferentially via the second connection opening toward the inflow opening side and can slidably contact the inner peripheral surface of the setting hole in a liquid-tight manner between the second connection port and the inflow port.

4. The axial piston device according to claim 2, characterized in that, The discharge region is circumferentially located between the first closed region and the second closed region. The discharge oil passage releases the discharged oil flowing in from the inlet end portion to the internal space of the housing.

5. The axial piston device according to claim 1, characterized in that, The servo space is provided near the region of the peripheral wall portion where the radial opening is provided and at the corner of the housing connected to the first end wall portion in such a manner that the length direction is orthogonal to both the axis of the rotating shaft and the swing axis.

6. The axial piston device according to claim 1, characterized in that, The housing has: a housing body, which integrally has the first end wall portion and the peripheral wall portion, and the side of the peripheral wall portion opposite to the first end wall portion is provided as an opening; and a sealing member, which is detachably connected to the housing body in a manner to close the opening to form the second end wall portion.

7. The axial piston device according to claim 1, characterized in that, A reference position biasing mechanism for biasing the input valve shaft toward the reference position around the axis is provided. The reference position biasing mechanism has: a reference position arm, which extends in a direction orthogonal to the input valve shaft in a state where the base end side is connected to the input valve shaft in a non-rotatable manner around the axis. An engagement pin, which is erected in parallel with the swing axis on the reference position arm; a reference position piston, which is housed in a housing space formed in the cover body in such a manner that the length direction is orthogonal to the swing axis and can reciprocate in the length direction, and the free end portion of the engagement pin is engaged therewith; and a reference position biasing member, which biases the reference position piston toward the length direction reference position corresponding to the reference position of the input valve shaft around the axis.

8. The axial piston device according to claim 1, characterized in that, The first valve shaft and the second valve shaft respectively function as the feedback valve shaft and the input valve shaft. An operation input portion that can be manually operated is formed at the outer end portion of the second valve shaft.

9. The axial piston device according to claim 1, characterized in that, The first valve shaft and the second valve shaft respectively function as the input valve shaft and the feedback valve shaft. The axis hole of the first valve shaft into which the second valve shaft is inserted is open at the inner end surface, and an operation input portion that can be manually operated is formed at the outer end portion.

10. An axial piston device, comprising: a housing; a rotating shaft supported by the housing so as to be rotatable about an axis; an axial piston member housed in the housing while being supported by the rotating shaft so as not to be relatively rotatable; A movable swash plate that changes the volume of the axial piston member according to its tilt rotation position about the swing axis; a hydraulic servo mechanism that generates an operating force for tilting the movable swash plate about the swing axis; an operating member that is manually operated; an operation sensor that detects the operating state of the operating member; and a hydraulic operating mechanism that rotates the input valve shaft about its axis; and a control device that controls the operation of the hydraulic operating mechanism. The axial piston device is characterized in that the hydraulic servo mechanism includes: a servo piston that is housed in a state where a first oil chamber and a second oil chamber are respectively liquid-tightly defined at one end side and the other end side in the length direction of a servo space formed in the housing, and moves in a first axial direction by supplying pressure oil to the first oil chamber and discharging pressure oil from the second oil chamber, and moves in a second axial direction by supplying pressure oil to the second oil chamber and discharging pressure oil from the first oil chamber; a connecting arm that tilts the movable swash plate about the swing axis in a first direction and a second direction respectively according to the movement of the servo piston in the first axial direction and the second axial direction; a pressure oil pipeline that receives pressure oil from a hydraulic source; a first supply / discharge pipeline and a second supply / discharge pipeline that are respectively fluid-connected to the first oil chamber and the second oil chamber; a discharge pipeline; a switching valve group that switches the connection states of the pressure oil pipeline, the first supply / discharge pipeline, the second supply / discharge pipeline, and the discharge pipeline, including a first valve shaft that is housed in a setting hole formed in the housing in a liquid-tight and rotatable manner about its axis and a second valve shaft that is housed in an axial hole of the first valve shaft in a rotatable manner about its axis, one of the first valve shaft and the second valve shaft functions as an input valve shaft and the other of the first valve shaft and the second valve shaft functions as a feedback valve shaft; and a feedback arm that relatively rotates the feedback valve shaft about its axis with respect to the input valve shaft according to the movement of the connecting arm, the hydraulic operating mechanism includes: an operating arm that extends in a direction orthogonal to the input valve shaft with its proximal end side connected to the input valve shaft in a non-rotatable manner about its axis; an operating piston that is housed in the housing space formed in the housing with its length direction orthogonal to the swing axis, and a first operating oil chamber and a second operating oil chamber are respectively liquid-tightly defined at one end side and the other end side in the length direction of the housing space, and moves in a first length direction by supplying pressure oil to the first operating oil chamber and discharging pressure oil from the second operating oil chamber, and moves in a second length direction by supplying pressure oil to the second operating oil chamber and discharging pressure oil from the first operating oil chamber; a connecting member that operatively connects the operating piston and the operating arm in such a manner that the input valve shaft rotates about its axis in a first direction and a second direction respectively according to the movement of the operating piston in the first length direction and the second length direction; a first operating biasing member and a second operating biasing member that are respectively disposed in the first input oil chamber and the second input oil chamber so as to clamp the operating piston; an operating pressure oil pipeline that receives pressure oil from a hydraulic source; an operating discharge pipeline; and a first electromagnetic proportional valve and a second electromagnetic proportional valve that respectively switch the supply and discharge of pressure oil to and from the first operation oil chamber and the second operation oil chamber, the first electromagnetic proportional valve and the second electromagnetic proportional valve are configured to be able to assume a pressure oil supply state in which the corresponding operation oil chamber is cut off from the operation discharge pipeline and connected to the operation pressure oil pipeline, a holding state in which the corresponding operation oil chamber is cut off from both the operation pressure oil pipeline and the operation discharge pipeline, and a pressure oil discharge state in which the corresponding operation oil chamber is cut off from the operation pressure oil pipeline and connected to the operation discharge pipeline, the control device controls the operation of the first electromagnetic proportional valve and the second electromagnetic proportional valve based on a signal from the operation sensor so that the input valve shaft is positioned around the axis corresponding to the operation state of the operation member.

11. The axial piston device according to claim 10, characterized in that, the first electromagnetic proportional valve and the second electromagnetic proportional valve include: a main body having a drive portion; and a valve core that is housed in the main body so as to be able to move forward and backward in the axial direction so that it can assume an initial position where the holding state appears, a protruding position where the pressure oil supply state appears, and a storage position where the pressure oil discharge state appears, the drive portion is configured to assume an ON state in which the valve core is forcibly pushed in the protruding direction based on a control signal from the control device and an OFF state in which substantially no driving force is applied to the valve core, the valve core has an oil chamber side pressure receiving portion that receives the pressure of the operation oil chamber and generates a storage direction driving force that pushes the valve core in the storage direction. When the drive portion is in the OFF state, the valve core assumes the initial position when the pressure of the operation oil chamber is substantially zero and is in a balanced state with the operation discharge pipeline, and assumes the storage position when the storage direction driving force exceeds the pressure of the operation discharge pipeline and the oil chamber hydraulic pressure is generated, 12. The axial piston device according to claim 11, characterized in that, the drive portion has a pin that abuts against the base end surface of the valve core in the ON state and pushes the valve core in the protruding direction, in the OFF state, the drive portion applies a force to the pin toward the base end surface of the valve core so as to allow the valve core to assume the initial position in the balanced state and the storage position in the oil chamber hydraulic pressure generation state and maintain the abutting state between the pin and the base end surface of the valve core.

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