Patent Description:
An HST capable of speed-change a rotational power in a stepless manner is preferably used as a part or a whole of a travel system transmission provided in a work vehicle such as a combine harvester and a tractor.

The following patent literature <NUM> discloses a transmission that shifts and transmits a rotational power from an engine arranged in front to a rear wheel that serves as a drive wheel, and that has a casing provided with an opening that opens upward and an HST housed in the casing, wherein all components of the HST are supported by a cover that closes the opening.

The transmission described in the patent literature <NUM> is useful in that the HST can be removed by removing the cover from the casing while the casing is mounted on a vehicle.

However, in the configuration described in the patent literature <NUM>, all components of the HST are supported by the cover in a cantilevered state, causing a problem that support stability is lacking.

The present invention has been made in view of the conventional technology, and it is a first object to provide an HST that can be integrally attached to and detached from a transmission case in a work vehicle without disassembling components of the work vehicle, while stabilizing a supporting state of the components including a center section, a pump-side swash plate holder, and a motor-side swash plate holder.

In addition, it is a second object of the present invention to provide a transmission that shifts a rotational power operatively input from a drive source, and, with the installation state of the transmission case maintained, that can be attached to and detached from the transmission case without disassembling the HST, while stabilizing the support of the HST components including the center section, the pump-side swash plate holder, and the motor-side swash plate holder.

In order to achieve the first object, the present invention provides an HST including a pump shaft, a pump main body supported by the pump shaft in a manner relatively non-rotatable around an axial line with respect to the pump shaft, a pump-side swash plate defining a capacity of the pump main body, a pump-side swash plate holder supporting a rear surface of the pump-side swash plate, a motor shaft, a motor main body supported by the motor shaft in a manner relatively non-rotatable around an axial line with respect to the motor shaft, a motor-side swash plate defining a capacity of the motor main body, a motor-side swash plate holder supporting a rear surface of the motor-side swash plate, a center section on which the pump main body and the motor main body directly or indirectly abut in a slidable manner around the respective axial lines and which is formed with oil paths fluidly connecting the pump main body and the motor main body, and a main plate and a sub-plate that hold or support the center section, the pump-side swash plate holder and the motor-side swash plate holder in a sandwiched manner by inner surfaces of the main plate and the sub-plate that face each other, wherein the main plate is provided with an extended region that extends farther outward in a planar direction of the main plate than an installation space of the center section, the pump-side swash plate holder and the motor-side swash plate holder, and than the sub-plate as viewed along a direction in which the main plate and the sub-plate face each other.

The HST according to the present invention makes it possible to be attached to and detached from a transmission case in a work vehicle without being disassembled while stabilizing the support of components including the center section, the pump-side swash plate holder and the motor-side swash plate holder.

In a first example of a first embodiment, the HST is of an in-line type in which the pump main body and the motor main body that are respectively arranged on one side and the other side in a thickness direction of the center section while being arranged coaxially with each other.

In a second example of the first embodiment, the pump main body is arranged on one side in the thickness direction of the center section, and the motor main body is arranged on the other side in the thickness direction of the center section with a shaft line of the motor main body being parallel to and displaced from a shaft line of the pump main body.

In a preferable configuration of the first embodiment, an inner surface of at least one of the main plate and the sub-plate is provided with a pump-side concave portion into which the pump-side swash plate holder is engaged and a motor-side concave portion into which the motor-side swash plate holder is engaged.

The pump-side concave portion and the motor-side concave portion are so configured as to prevent the pump-side swash plate holder and the motor-side swash plate holder from moving in a direction away from or a direction close to the center section with respect to the thickness direction of the center section.

In a preferable configuration of the first embodiment, an inner surface of at least one of the main plate and the sub-plate is provided with a center section-directed concave portion in which the center section is engaged in a manner to be immovable in the thickness direction of the center section.

The HST according to a second embodiment is of a parallel type in which the pump main body and the motor main body are arranged on one side in a thickness direction of the center section with their axial lines being parallel to each other.

In a preferable configuration of the second embodiment, the HST may include a common swash plate holder integrally having the pump-side swash plate holder and the motor-side swash plate holder.

In a more preferable configuration, an inner surface of at least one of the main plate and the sub-plate is provided with an engagement concave portion into which at least one of the common swash plate and the center section so that an HST preassembly in which the center section, the pump shaft, the pump main body, the pump-side swash plate, the motor shaft, the motor main body, the motor-side swash plate and the common swash plate holder are assembled is prevented from moving in the axial line direction of the pump shaft.

In any one of the above various configurations, at least one of the pump-side swash plate holder and the motor-side swash plate holder may support the rear surface of the corresponding swash plate in such a manner that the corresponding swash plate is swingable around a swing axial line.

In this case, the main plate is preferably provided with a hydraulic servo mechanism that swings a movable swash plate, which is supported in a swingable manner around the corresponding swing axial line among the pump-side swash plate and the motor-side swash plate, around the corresponding swing axial line.

For example, the hydraulic servo mechanism may include a pushing piston that is housed in the main plate in a manner to be reciprocally movable in a pushing direction and is operatively connected to the movable swash plate via a connecting rod so that the movable swash plate swings around the swing axial line in accordance with a movement of the pushing piston along the pushing direction, first and second hydraulic oil chambers formed in the main plate in such a manner that pressure oil supplied into the first and second hydraulic oil chambers push the pushing piston to one side and the other side in the pushing direction, respectively, a switching spool that switches supply and discharge of pressure oil to and from the first and second hydraulic oil chambers in accordance with a position in a switching direction, an operating piston that is housed in the main plate in a manner to be reciprocally movable in an operating direction parallel to the switching direction and is operatively connected to the switching spool via a connection pin, first and second operation oil chambers formed in the main plate in such a manner that pressure oil supplied into the first and second operation oil chambers push the operating piston to one side and the other side in the operating direction, and an operating valve that switches supply and discharge of pressure oil to and from the first and second operation oil chambers.

In this case, the main plate is preferably provided with a manual operating mechanism capable of manually changing the position of the switching spool in the switching direction.

In order to achieve the second object, the present invention provides a transmission that speed-changes rotational power operatively input from a drive source, the transmission including a transmission case, an input-side transmission shaft that is operatively connected to the drive source and is supported by the transmission case in a rotatable manner around an axial line, an input-side transmission gear supported by the input-side transmission shaft in a manner relatively non-rotatable around an axial line with respect to the input-side transmission shaft within the transmission case, an output-side transmission shaft supported by the transmission case in a rotatable manner around an axial line, an output-side transmission gear supported by the output-side transmission shaft in a manner relatively non-rotatable manner around an axial line with respect to the output-side transmission shaft within the transmission case, and the HST.

According to the transmission of the present invention, it is possible to attach and detach the HST to and from the transmission case without disassembling the HST and with keeping an installation state of the transmission case while stabilizing the support of components including the center section, the pump-side swash plate holder and the motor-side swash plate holder.

In the transmission according to the present invention, the HST includes a pump shaft, a pump main body supported by the pump shaft in a manner relatively non-rotatable around an axial line with respect to the pump shaft, a pump-side swash plate defining a capacity of the pump main body, a pump-side swash plate holder that supports a rear surface of the pump-side swash plate and is formed with a through hole through which the pump shaft is passed, a pump-side transmission gear supported by a portion of the pump shaft that extends from a portion passing through the pump-side swash plate holder in a direction away from the pump main body in such a manner that the pump-side transmission gear is relatively non-rotatable around the axial line with respect to the pump shaft, a motor shaft, a motor main body supported by the motor shaft in a manner relatively non-rotatable around an axial line with respect to the motor shaft, a motor-side swash plate defining a capacity of the motor main body, a motor-side swash plate holder that supports a rear surface of the motor-side swash plate and is formed with a through hole through which the motor shaft is passed, a motor-side transmission gear supported by a portion of the motor shaft that extends from a portion passing through the motor-side swash plate holder in a direction away from the motor main body in such a manner that the motor-side transmission gear is relatively non-rotatable around the axial line with respect to the motor shaft, a center section that is formed with oil paths fluidly connecting the pump main body and the motor main body, and a main plate and a sub-plate that hold or support the center section, the pump-side swash plate holder and the motor-side swash plate holder in a sandwiched manner by inner surfaces of the main plate and the sub-plate that face each other.

The transmission case has a peripheral wall and an opening formed in the peripheral wall. The opening is so sized as to allow, in an assembled state of the HST, insertion of components other than the main plate of the HST. The main plate is detachably connected to an outer surface of the peripheral wall of the transmission case so that the components of the HST other than the main plate is housed within the transmission case via the opening.

The pump-side transmission gear and the motor-side transmission gear is so configured as to mesh with the input-side transmission gear and the output-side transmission gear, respectively, in accordance with connection of the main plate to the outer surface of the peripheral wall of the transmission case.

In one embodiment of the transmission according to the present invention, the main plate is formed with a supply oil path having one end portion opened to an outer surface to form an inlet port for receiving charge oil of operation oil of the HST. The pump-side swash plate holder and the motor-side swash plate holder are formed with oil paths receiving a part of oil supplied into the supply oil path. The pump shaft is formed with an axial line hole receiving at least a part of oil introduced into the oil path of the pump-side swash plate holder, and the motor shaft is formed with an axial line hole receiving at least a part of oil introduced into the oil path of the motor-side swash plate holder.

The axial line hole of the pump shaft and the axial line hole of the motor shaft is so configured as to supply the introduced oil to a site to be lubricated.

One embodiment of an HST according to the present invention will be described below with reference to the accompanying drawings.

<FIG> illustrates a schematic diagram of a power transmission of a work vehicle <NUM> to which a transmission 10A provided with an HST 100A according to the present embodiment is applied.

<FIG> illustrates an exploded perspective view of a transmission case <NUM> and the HST 100A in the above transmission 10A.

Further, <FIG> illustrate an exploded perspective view, a transverse cross-sectional plan view, and a hydraulic circuit diagram of the HST 100A, respectively.

As illustrated in <FIG>, <FIG> and the like, the HST 100A includes a pump shaft <NUM> that operatively inputs a rotational power from a drive source <NUM> (<FIG>) provided in the work vehicle <NUM>, a pump main body <NUM> that is relatively non-rotatably supported by the pump shaft <NUM>, a pump-side swash plate <NUM> that defines a capacity of the pump main body <NUM>, a pump-side swash plate holder 125A which supports a rear surface of the pump-side swash plate <NUM>, a motor shaft <NUM>, a motor main body <NUM> which is relatively non-rotatably supported by the motor shaft <NUM>, a motor-side swash plate <NUM> which defines a capacity of the motor main body <NUM>, a motor-side swash plate holder 145A which supports a rear surface of the motor-side swash plate <NUM>, a center section 150A, a main plate 160A, and a sub-plate 170A.

The HST 100A according to the present embodiment is of an in-line type in which the pump main body <NUM> and the motor main body <NUM> are arranged on one side and the other side in the thickness direction of the center section 150A, respectively, while being arranged coaxially with each other.

<FIG> illustrates a cross-sectional view along the line VI-VI in <FIG>. As illustrated in <FIG> and <FIG>, the pump main body <NUM> has a pump-side cylinder block <NUM>, and pump-side pistons <NUM> housed in the pump-side cylinder block <NUM> so as to be relatively non-rotatable around an axial line and to advance and retreat in an axial line direction with respect thereto.

The pump-side cylinder block <NUM> is relatively non-rotatably supported by the pump shaft <NUM> with a base end surface directly or indirectly contacting a first end surface on one side in the thickness direction of the center section 150A.

The pump-side swash plate <NUM> is engaged with tip end portions of the pump-side pistons <NUM> so as to define the advance or retreat amount of the pump-side pistons <NUM> per revolution around the axial line of the pump-side cylinder block <NUM>, that is, the capacity of the pump main body <NUM>.

In the present embodiment, the pump-side swash plate <NUM> is a movable swash plate that can swing around the swing axial line, and according to the swing position of the pump-side swash plate <NUM> around the swing axial line, the advance or retreat amount of the pump-side piston <NUM> changes thereby to change the capacity of the pump main body <NUM>.

The pump-side swash plate holder 125A is arranged in a manner to support the rear surface of the pump-side swash plate <NUM> (a surface opposite in the axial line direction to the surface with which the pump-side piston <NUM> is engaged).

As described above, in the present embodiment, the pump-side swash plate <NUM> is a movable swash plate that can swing around the swing axial line.

Accordingly, as illustrated in <FIG>, the pump-side swash plate holder 125Ahas a concave support surface along the swing path of the rear surface of the pump-side swash plate <NUM> which path is seen when the pump-side swash plate <NUM> is swung around the swing axial line.

With the base end and tip end portions thereof rotatably supported by the center section 150A and the pump-side swash plate holder 125A, respectively, the pump shaft <NUM> supports the pump main body <NUM> at a middle portion in a manner relatively non-rotatable around the axial line with respect to the pump shaft <NUM>.

The pump-side swash plate <NUM> is provided with a through hole that allows the pump shaft <NUM> to pass through.

As illustrated in <FIG> and <FIG>, the motor main body <NUM> has a motor-side cylinder block <NUM> and motor-side pistons <NUM> housed in the motor-side cylinder block <NUM> so as to be relatively non-rotatable around an axial line and to advance and retreat in an axial line direction with respect thereto.

With the base end surface directly or indirectly contacting the second end surface on the other side in the thickness direction of the center section 150A, the motor-side cylinder block <NUM> is supported by the motor shaft <NUM>, which is arranged coaxially with the pump shaft <NUM>, in a manner relatively non-rotatable around the axial line with respect to the motor shaft <NUM>.

The motor-side swash plate <NUM> is engaged with the tip end portions of the motor-side pistons <NUM> so as to define the advance or retreat amount of the motor-side pistons <NUM> per revolution around the axial line of the motor-side cylinder block <NUM>, that is, the capacity of the motor main body <NUM>.

In the present embodiment, the motor-side swash plate <NUM> is a fixed swash plate in which a swash angle relative to the motor shaft <NUM> is fixed so that the capacity of the motor main body <NUM> is fixed.

The motor-side swash plate holder 145A is arranged in a manner to support the rear surface of the motor-side swash plate <NUM> (a surface opposite in the axial line direction to the surface with which the motor-side piston <NUM> is engaged).

As described above, in the present embodiment, the motor-side swash plate <NUM> is the fixed swash plate.

Accordingly, as illustrated in <FIG>, the motor-side swash plate holder 145A has a swash support surface for fixing the motor-side swash plate <NUM> at a predetermined swash angle.

The motor shaft <NUM> is arranged coaxially with the pump shaft <NUM>. With the base end and the tip end portions thereof rotatably supported by the center section 150A and the motor-side swash plate holder 145A, respectively, the motor shaft <NUM> supports the motor main body <NUM> at the middle portion in a manner relatively non-rotatable manner around the axial line with respect to the motor shaft <NUM>.

The motor-side swash plate <NUM> is provided with a through hole that allows the motor shaft <NUM> to pass through.

<FIG> illustrates a cross-sectional view along the line VII-VII in <FIG>.

As illustrated in <FIG>, <FIG>, etc., a pair of HST operation oil paths <NUM> which fluidly connects the pump main body <NUM> and the motor main body <NUM> is formed in the center section 150A.

The main plate 160A and the sub-plate 170A are so configured as to hold or support the center section 150A, the pump-side swash plate holder 125A, and the motor-side swash plate holder 145A in a sandwiched manner by their inner surfaces facing each other.

That is, the main plate 160A, with the inner surface thereof in contact with the side surfaces of the center section 150A, the pump-side swash plate holder 125A, and the motor-side swash plate holder 145A on one side in the width direction orthogonal to the thickness direction (that is, the axial line direction of the pump shaft <NUM> and the motor shaft <NUM>), is connected to the above members by fastening members <NUM> (see <FIG>), such as a bolt.

With the center section 150A, the pump-side swash plate holder 125A, and the motor-side swash plate holder 145A arranged between the inner surface of the sub-plate 170A and the inner surface of the main plate 160A, the sub-plate 170A is arranged so as to face the main plate 160A. Further, the inner surface of the sub-plate 170A is brought into contact with the side surfaces of the center section 150A, the pump-side swash plate holder 125A, and the motor-side swash plate holder 145A on the other side in the width direction, and is connected to the above members by fastening members <NUM> (see <FIG>), such as a bolt.

As illustrated in <FIG>, <FIG>, <FIG>, and <FIG>, etc., when viewed along a direction in which the main plate 160A and the sub-plate 170Aface each other (i.e., a direction orthogonal to plate surfaces of the main plate 160A and the sub-plate 170A), the main plate 160Ais provided with an extended region <NUM> that extends farther outward in the planar direction than an installation space of the center section 150A, the pump-side swash plate holder 125A, and the motor-side swash plate holder 145A, and than the sub-plate 170A.

According to the HST 100A having such a configuration, since the center section 150A, the pump-side swash plate holder 125A, and the motor-side swash plate holder 145A are supported at both sides by the main plate 160A and the sub-plate 170A, the support of the components can be stabilized.

Further, in the transmission case <NUM> to which the HST 100A is mounted, providing an opening <NUM> (see <FIG>) that is smaller than the extended region <NUM> of the main plate 160A and larger than the installation space of the center section 150A, the pump-side swash plate holder 125A, and the motor-side swash plate holder 145A, and than the sub-plate 170A makes it possible to attach or detach the HST 100A to or from the transmission case <NUM> without disassembling the HST 100A.

Accordingly, the maintenance work and component replacement work of the HST 100A can be facilitated.

In detail, as illustrated in <FIG> and <FIG>, the transmission 10A is provided with the transmission case <NUM>, an input-side transmission shaft <NUM> which is, in a state of being operatively connected to the drive source <NUM>, supported by the transmission case <NUM> in a manner to rotate around an axial line, an input-side transmission gear <NUM> supported by the input-side transmission shaft <NUM> in a manner relatively non-rotatable around the axial line with respect to the input-side transmission shaft <NUM> within the transmission case <NUM>, an output-side transmission shaft <NUM> supported by the transmission case <NUM> in a manner to rotate around an axial line, an output-side transmission gear <NUM> supported by the output-side transmission shaft <NUM> in a manner relatively non-rotatable manner around the axial line with respect to the output-side transmission shaft <NUM> within the transmission case <NUM>, and the HST 100A. The input-side transmission gear <NUM> and the output-side transmission gear <NUM> are arranged axially spaced apart within a front half portion or a first half portion of the transmission case <NUM>.

The HST 100A is so configured as to be detachably attached to the transmission case <NUM>, and so configured that when the HST 100A is mounted on the transmission case <NUM>, the pump shaft <NUM> is operatively connected to the input-side transmission shaft <NUM> and the motor shaft <NUM> is operatively connected to the output-side transmission shaft <NUM>.

In detail, as illustrated in <FIG> and the like, the HST 100A further has a pump-side transmission gear <NUM> supported by the pump shaft <NUM> in a manner relatively non-rotatable around the axial line with respect to the pump shaft <NUM> and a motor-side transmission gear <NUM> supported by the motor shaft <NUM> in a manner relatively non-rotatable around the axial line with respect to the motor shaft <NUM>.

In the present embodiment, the pump-side transmission gear <NUM> is supported at a portion of the pump shaft <NUM> that extends from a portion passing through the pump-side swash plate holder 125Ain a direction away from the pump main body <NUM>, and the motor-side transmission gear <NUM> is supported at a portion of the motor shaft <NUM> that extends from a portion passing through the motor-side swash plate holder 145Ain a direction away from the motor main body <NUM>.

As illustrated in <FIG>, the transmission case <NUM> has, in the first half portion thereof, a peripheral wall <NUM> and the opening <NUM> provided in the peripheral wall <NUM>.

The opening <NUM> is so sized as to allow, in the assembled state of the HST 100A, insertion of components other than the main plate 160Ain the HST 100A.

That is, the opening <NUM> is so configured as to be larger than the installation space of the center section 150A, the pump-side swash plate holder 125A, and the motor-side swash plate holder 145A, and than the sub-plate 170A, but smaller than the extended region <NUM> of the main plate 160A.

In the present embodiment, the opening <NUM> is provided at a side surface of the peripheral wall <NUM>, the side surface being located on the side based on the state in which the transmission case <NUM> is mounted on the work vehicle <NUM>.

Alternatively, it is also possible to provide the opening <NUM> at an upper surface or a lower surface of the peripheral wall <NUM>.

As illustrated in <FIG> and <FIG>, fastening holes <NUM> through which fastening members such as a bolt can be inserted are formed at the extended region <NUM> of the main plate 160A.

The extended region <NUM> is brought in contact with an outer surface of the peripheral wall <NUM> of the transmission case <NUM> in a state in which the HST 100A's component other than the main plate 160A is housed within the transmission case <NUM> via the opening <NUM>, and is detachably connected to the outer surface via fastening members such as a bolt to be inserted into the fastening hole <NUM>.

Further, the pump-side transmission gear <NUM> and the motor-side transmission gear <NUM> are so arranged to respectively mesh with the input-side transmission gear <NUM> and the output-side transmission gear <NUM> in accordance with connection of the extended region <NUM> of the main plate 160A to the outer surface of the peripheral wall <NUM> of the transmission case <NUM>.

As illustrated in <FIG> and <FIG>, in the present embodiment, the inner surfaces of the main plate 160A and the sub-plate 170A are provided with center section-directed concave portions <NUM> and <NUM> in which the center section 150A is engaged in a manner to be immovable in the thickness direction.

Providing such a configuration makes it possible to stabilize the support of the HST preassembly in which the center section 150A, the pump shaft <NUM>, the pump main body <NUM>, the pump-side swash plate <NUM>, the pump-side swash plate holder 125A, the motor shaft <NUM>, the motor main body <NUM>, the motor-side swash plate <NUM>, and the motor-side swash plate holder 145A are assembled.

In the present embodiment, the main plate 160A and the sub-plate 170A are formed with the center section-directed concave portions <NUM> and <NUM>, respectively, but it is possible that only one of the main plate 160A and the sub-plate 170A is formed with the corresponding concave portion.

Further, as illustrated in <FIG> and <FIG>, in the present embodiment, the inner surfaces of the main plate 160A and the sub-plate 170A are provided with pump-side concave portions <NUM> and <NUM> into which the pump-side swash plate holder 125A is engaged, and motor-side concave portions <NUM> and <NUM> into which the motor-side swash plate holder 145A is engaged.

The pump-side concave portions <NUM>, <NUM> and the motor-side concave portions <NUM>, <NUM> are so configured as to prevent the pump-side swash plate holder 125A and the motor-side swash plate holder 145A from moving in a direction away from the center section 150A with respect to the thickness direction (axial line direction of the pump shaft <NUM> and the motor shaft <NUM>).

As illustrated in <FIG>, in the present embodiment, the pump-side concave portions <NUM> and <NUM> have step portions 166a and 176a that engage with end surfaces of the pump-side swash plate holder 125A on a far side from the center section 150A.

The motor-side concave portions <NUM> and <NUM> have step portions 167a and 177a that engage with end surfaces of the motor-side swash plate holder 145A on a far side from the center section 150A.

Providing such a configuration can further stabilize the support state of the HST preassembly.

In place of this configuration, the pump-side concave portions <NUM>, <NUM> and the motor-side concave portions <NUM>, <NUM> can be so configured as to prevent the pump-side swash plate holder 125A and the motor-side swash plate holder 145A from moving in a direction proximate to the center section 150A with respect to the thickness direction.

That is, the pump-side concave portions <NUM> and <NUM> can be so configured as to have step portions that engage with the end surfaces of the pump-side swash plate holder 125A on a near side to the center section 150A, and the motor-side concave portions <NUM> and <NUM> can be so configured as to have step portions that engage with the end surfaces of the motor-side swash plate holder 145A on a near side to the center section 150A.

In the present embodiment, as illustrated in <FIG>, the center section-directed concave portions <NUM>, <NUM> have step portions 165a, 165b, 175a, 175b that engage with the lower surface and upper surface of the center section 150A.

<FIG> and <FIG> illustrate cross-sectional views along the lines VIII-VIII and IX-IX in <FIG>, respectively.

As illustrated in <FIG>, in the present embodiment, the pump-side concave portions <NUM> and <NUM> have step portions 166b, 176b, 166c, and 176c that engage with the lower surface and upper surface of the pump-side swash plate holder 125A.

Similarly, as illustrated in <FIG>, the motor-side concave portions <NUM> and <NUM> have step portions 167b, 177b, 167c, and 177c that engage with the lower surface and upper surface of the motor-side swash plate holder 145A.

Such a configuration can further stabilize the support of the HST preassembly.

In the present embodiment, the center section-directed concave portions <NUM> and <NUM> have step portions 165a and 175a that engage with the lower surfaces of the center section 150A and step portions 165b and 175b that engage with the upper surfaces of the center section 150A, but alternatively, can be modified in such a way as to have only the step portion that engages with any one of the lower surface and the upper surface.

The pump-side concave portions <NUM> and <NUM> and the motor-side concave portions <NUM> and <NUM> have step portions 166b, 176b, 167b, and 177b that engage with the lower surfaces of the corresponding swash plate holder and step portions 166c, 176c, 167c, and 177c that engage with the upper surfaces of the corresponding swash plate holder, but alternatively, can be transformed in such a way as to have only the step portion that engages with any one of the lower surface and the upper surface.

In the present embodiment, although the pump-side concave portions <NUM> and <NUM> are provided in the main plate 160A and the sub-plate 170A respectively, and the motor-side concave portions <NUM> and <NUM> are provided in the main plate 160A and the sub-plate 170A respectively, it is also possible to provide the pump-side concave portion only in one of the main plate 160A and the sub-plate 170A, and/or to provide the motor-side concave portions only in one of the main plate 160A and the sub-plate 170A.

As illustrated in <FIG> and <FIG>, the above HST 100A according to the present embodiment further has a hydraulic servo mechanism <NUM> that generates a force for swinging a movable swash plate (the pump-side swash plate <NUM> in the present embodiment).

In the present embodiment, the hydraulic servo mechanism <NUM> is provided at the main plate 160A.

<FIG> and <FIG> illustrate cross-sectional views along the lines X-X and XI-XI in <FIG>, respectively.

As illustrated in <FIG>, <FIG>, <FIG> and <FIG>, the hydraulic servo mechanism <NUM> includes: a pushing piston <NUM> housed in the main plate 160A in a manner to be reciprocally movable in a direction (hereinafter, referred to as pushing direction) orthogonal to both the axial line of the hydraulic body (the pump main body <NUM> in the present embodiment) having the capacity varied by the movable swash plate (the pump-side swash plate <NUM> in the present embodiment) and the swing axial line, and is operatively connected to the movable swash plate via a connecting rod <NUM> so that the movable swash plate swings around the swing axial line by a movement along the pushing direction, first and second hydraulic oil chambers <NUM> (<NUM>) and <NUM> (<NUM>) formed in the main plate 160A in a manner that pressure oil supplied into the first and second hydraulic oil chambers push the pushing piston <NUM> to one side and the other side respectively in the pushing direction, respectively, a switching spool <NUM> that can selectively take: a first operation position where a hydraulic source is fluidly connected to the first hydraulic oil chamber <NUM> (<NUM>) and the second hydraulic oil chamber <NUM> (<NUM>) is drained thereby to supply the pressure oil from the hydraulic source to the first hydraulic oil chamber <NUM> (<NUM>), a second operation position where the hydraulic source is fluidly connected to the second hydraulic oil chamber <NUM> (<NUM>) and the first hydraulic oil chamber <NUM> (<NUM>) is drained thereby to supply the pressure oil from the hydraulic source to the second hydraulic oil chamber <NUM> (<NUM>), and a close position for closing the first hydraulic oil chamber <NUM> (<NUM>) and the second hydraulic oil chamber <NUM> (<NUM>), an operating piston <NUM> that is, in a state of being connected to the switching spool <NUM> via a connection pin <NUM>, reciprocally housed in the main plate 160A, and can take: a first operation position, a hold position, and a second operation position for respectively positioning the switching spool <NUM> in the first operation position, the close position, and the second operation position, a first operation oil chamber <NUM> (<NUM>) and a second operation oil chamber <NUM> (<NUM>) formed in the main plate 160A in a manner that the supplied pressure oil can push the operating piston <NUM> to the first operation position and the second operation position respectively, and an operating valve <NUM> that can selectively take: a first position where the hydraulic source is fluidly connected to the first operation oil chamber <NUM> (<NUM>) and the second operation oil chamber <NUM> (<NUM>) is drained thereby to supply the pressure oil from the hydraulic source to the first operation oil chamber <NUM> (<NUM>) so as to position the operating piston <NUM> in the first operation position, a second position where the hydraulic source is fluidly connected to the second operation oil chamber <NUM> (<NUM>) and the first operation oil chamber <NUM> (<NUM>) is drained thereby to supply the pressure oil from the hydraulic source to the second operation oil chamber <NUM> (<NUM>) so as to position the operating piston <NUM> in the second operation position, and a close position where the first operation oil chamber <NUM> (<NUM>) and the second operation oil chamber <NUM> (<NUM>) are closed thereby to position the operating piston <NUM> in the hold position.

In the present embodiment, the switching spool <NUM> is housed in an axial line hole formed in the pushing piston <NUM>, and the direction in which the switching spool reciprocates (switch direction) and the pushing direction in which the pushing piston reciprocates are the same.

In the present embodiment, the operating valve <NUM> is a solenoid valve that is operated and controlled by a control device provided in the work vehicle <NUM>.

As illustrated in <FIG> and <FIG>, in the present embodiment, a first spring <NUM> (<NUM>) for biasing the operating piston <NUM> toward the first operation position is arranged in the first operation oil chamber <NUM> (<NUM>), and a second spring <NUM> (<NUM>) for biasing the operating piston <NUM> toward the second operation position is arranged in the second operation oil chamber <NUM> (<NUM>).

The first and second springs <NUM>(<NUM>), <NUM>(<NUM>) are set to exert a biasing force in a manner to position the operating piston <NUM> in the hold position, when the pressure oil fails to act on both of the first and second operation oil chambers <NUM>(<NUM>), <NUM>(<NUM>).

The HST 100A further has a manual operating mechanism <NUM> for manually moving the switching spool <NUM>.

In detail, as illustrated in <FIG>, the direction in which the operating piston <NUM> reciprocates (operation direction) and the direction in which the switching spool <NUM> reciprocates (switch direction) are parallel to each other, and the connection pin <NUM> has a base end portion engaged with the switching spool <NUM> and a tip end portion engaged with the operating piston <NUM> so that the switching spool <NUM> moves along the switch direction in accordance with the movement of the operating piston <NUM> in the operation direction.

In the present embodiment, the manual operating mechanism <NUM> is provided at the main plate 160A.

In detail, the manual operating mechanism <NUM> has an operation shaft <NUM> supported by the main plate 160A rotatably around an axial line in a state that it is parallel to the connection pin <NUM> and its tip end portion extends outward, and a connection arm <NUM> that has a base end portion connected to the operation shaft <NUM> in a manner to be relatively non-rotatable around an axial line with respect thereto and has a tip end portion connected to the connection pin <NUM>.

Rotating the operation shaft <NUM> around the axial line by human operation moves the switching spool <NUM> in the switch direction via the connection arm <NUM> and the connection pin <NUM>.

Providing the manual operating mechanism <NUM> can provide a mode in which the switching spool <NUM> is moved by the human operation on the operation shaft <NUM>, in addition to the mode in which the switching spool <NUM> is moved by the action of the hydraulic pressure via the operating valve <NUM>.

Accordingly, even if one of the control structure for electrically controlling the position of the operating valve <NUM> and the manual operating mechanism for manually controlling the position of the operating valve <NUM> should fail due to some trouble, the position of the operating piston <NUM> can be controlled by the other.

Next, the oil path in the above HST 100A will be described.

<FIG> is a front view of the HST 100A in a state of being mounted on the transmission case <NUM>, as viewed from the outside of the transmission case <NUM>. In <FIG>, the part XII in <FIG> is illustrated in cross section.

<FIG> illustrates a cross-sectional view along the line XIII-XIII in <FIG>.

Further, <FIG> illustrates a cross-sectional view along the line XIV XIV in <FIG>.

As illustrated in <FIG>, <FIG>, and <FIG>, the main plate 160Ahas a supply oil path <NUM> having one end portion opened to an outer surface to form an inlet port 310P, a charge relief valve <NUM> that sets the hydraulic pressure of the supply oil path <NUM>, a lubrication oil path <NUM> that receives a relief oil of the charge relief valve <NUM>, and a lubrication relief valve <NUM> that sets the oil pressure of the lubrication oil path <NUM>.

As illustrated in <FIG>, in the present embodiment, the pressure oil is supplied to the inlet port 310P via a piping <NUM> from an auxiliary pump <NUM> driven by the drive source of the work vehicle <NUM>.

As illustrated in <FIG> and <FIG>, the supply oil path <NUM> has a downstream in the pressure oil flow direction that is branched into a charge supply oil path <NUM> and a servo supply oil path <NUM>.

As illustrated in <FIG>, the charge supply oil path <NUM> has a downstream side in the pressure oil flow direction opening on a contact surface with the center section 150A thereby to form a main plate side charge port 311P.

In the present embodiment, as described above, the center section-directed concave portion <NUM> is formed in the main plate 160Ain which the center section 150A is engaged in a manner to be immovable in the thickness direction, and the main plate side charge port 311P is provided on the bottom surface of the center section-directed concave portion <NUM>.

As illustrated in <FIG> and <FIG>, the center section 150A is formed with, in addition to the above pair of HST operation oil paths <NUM>, a charge oil path <NUM> having one end portion opened to an outer surface to form a center section side charge port 153P.

The charge oil path <NUM> has a downstream side in the pressure oil flow direction branched into two directions that are respectively fluidly connected to the pair of HST operation oil paths <NUM> via check valves <NUM>.

As illustrated in <FIG>, in the present embodiment, the check valve <NUM> is provided with a high-pressure relief function, so that when one HST operation oil path <NUM> has an abnormally high pressure, the pressure oil in the one HST operation oil path <NUM> is relieved to the other HST operation oil path <NUM>.

The servo supply oil path <NUM> is so configured as to supply the pressure oil to the operating valve <NUM> and the switching spool <NUM>.

As illustrated in <FIG> and <FIG>, the transmission case <NUM> is capable of storing the oil in the first half portion, and an oil level OL of the transmission case <NUM> is set lower so as not to become a rotational resistance of the pump main body <NUM> and the motor main body <NUM> when the HST 100A is mounted on the transmission case <NUM>. For this reason, as illustrated in <FIG> and the like, the lubrication oil path <NUM> has a pump-side lubrication oil path <NUM> and a motor-side lubrication oil path <NUM> so that forced lubrication is made for the HST 100A.

As illustrated in <FIG>, <FIG>, and <FIG>, etc., the pump-side lubrication oil path <NUM> is communicated to a predetermined lubrication site such as a bearing or a piston shoe via a lubrication oil path <NUM> formed in the pump-side swash plate holder 125A and an axial line hole <NUM> formed in the pump shaft <NUM>.

As illustrated in <FIG>, <FIG>, and <FIG>, etc., the motor-side lubrication oil path <NUM> is communicated to a predetermined lubrication site such as a bearing or a piston shoe via a lubrication oil path <NUM> formed in the motor-side swash plate holder 145A and an axial line hole <NUM> formed in the motor shaft <NUM>.

A reference numeral <NUM> in <FIG> is a pressure oil takeout oil path having one end portion connected to the HST operation oil path <NUM> and the other end portion opened on the outer surface of the main plate 160A thereby to form a takeout port for measuring the pressure in the HST operation oil path <NUM>, and a reference numeral <NUM> in <FIG> is a plug which closes the takeout port.

Herein, the transmission 10A will be described.

As illustrated in <FIG>, according to the present embodiment, the transmission 10A has a multi-step speed-change mechanism <NUM> that changes the rotational power of the output-side transmission shaft <NUM> in multiple steps, a differential mechanism <NUM> that differentially transmits the output of the multi-step speed-change mechanism <NUM> to a pair of left and right main drive axles <NUM>, a traveling brake mechanism <NUM> for applying a braking force to the main drive axles <NUM>, and a sub-drive wheel-directed power takeout mechanism <NUM> capable of outputting the output of the multi-step speed-change mechanism <NUM> to the sub-drive wheel.

The transmission 10A further has a PTO shaft <NUM> capable of outputting the rotational power toward external equipment such as work equipment, a PTO transmission shaft <NUM> operatively connected to the input-side transmission shaft <NUM>, a PTO brake mechanism <NUM> and a PTO speed-change mechanism <NUM> interposed in the PTO transmission path from the input-side transmission shaft <NUM> to the PTO shaft <NUM>.

Naturally, the HST 100A is applicable to another transmission 10B.

<FIG> illustrates a schematic diagram of power transmission of the work vehicle <NUM> to which the other transmission 10B provided with the above HST 100A is applied.

In the figure, the same reference numerals are attached to the same components as in the present embodiment.

The transmission 10B has a planetary gear mechanism <NUM>, a front/rear switching mechanism <NUM>, and a multi-step speed-change mechanism <NUM>, in place of the multi-step speed-change mechanism <NUM>.

The planetary gear mechanism <NUM> has three planetary elements including a sun gear <NUM>, a planetary carrier <NUM> and an internal gear <NUM>, and is so configured as to synthesize the rotational power of the HST 100A input via the output-side transmission shaft <NUM> and the rotational power of the drive source <NUM> input via the input-side transmission shaft <NUM>, and to output the synthesized rotational power.

In the configuration illustrated in the figure, the rotational power of the HST 100A is input to the sun gear <NUM> via the output-side transmission shaft <NUM>, the rotational power of the drive source <NUM> is input to the internal gear <NUM> via the input-side transmission shaft <NUM>, and the synthesized rotational power is output from the planetary carrier <NUM>.

Another embodiment of the HST according to the present invention will be described below with reference to the accompanying drawings.

<FIG> illustrates a vertical cross-sectional view of an HST 100B according to the present embodiment in a state of being mounted on the transmission case <NUM>, as viewed from the inside of the transmission case <NUM>.

<FIG> illustrates a cross-sectional view along the line XVII-XVII in <FIG>.

In the figure, the same components as those in the first embodiment described above are designated by the same reference numerals and the description thereof will be omitted as appropriate.

The HST 100B according to the present embodiment differs from the HST 100A according to the first embodiment in that the HST 100B is of a parallel type in which the pump main body <NUM> and the motor main body <NUM> are arranged on one side in a thickness direction of the center section 150B in a state parallel to each other.

Specifically, the HST 100B includes: a center section 150B, a pump-side swash plate holder 125B, a motor-side swash plate holder 145B, a main plate 160B and a sub-plate 170B that hold or support the center section 150B, the pump-side swash plate holder 125B, and the motor-side swash plate holder 145B in a sandwiched manner in a state where both the pump-side swash plate holder 125B and the motor-side swash plate holder 145B are arranged on one side of the center section 150B in the thickness direction, the pump shaft <NUM> supported rotatably around an axial line by the center section 150B and the pump-side swash plate holder 125B, the pump main body <NUM> supported by the pump shaft <NUM> in a manner relatively non-rotatable with respect to the pump shaft <NUM>, the pump-side swash plate <NUM> having the rear surface supported by the pump-side swash plate holder 125B, the motor shaft <NUM> that is, in a state of being parallel to the pump shaft <NUM>, supported by the center section 150B and the motor-side swash plate holder 145B in a manner to be rotatable around the axial line, the motor main body <NUM> supported by the motor shaft <NUM> in a manner relatively non-rotatable with respect to the motor shaft <NUM>, and the motor-side swash plate <NUM> having the rear surface supported by the motor-side swash plate holder 145B.

As illustrated in <FIG> and <FIG>, in the present embodiment, the pump-side swash plate holder 125B and the motor-side swash plate holder 145B are formed by a single common swash plate holder <NUM>.

That is, the HST 100B is provided with the common swash plate holder <NUM> integrally having a portion acting as the pump-side swash plate holder 125B and a portion acting as the motor-side swash plate holder 145B, and the main plate and the sub-plate are so configured as to hold or support the center section and the common swash plate holder in a sandwiched manner.

Similar to the main plate 160A in the first embodiment, when viewed along the direction in which the main plate 160B and the sub-plate 170B face one another, the main plate 160B is provided with the extended region <NUM> that extends farther outward in the planar direction than the installation space of the center section 150B, the pump-side swash plate holder 125B, and the motor-side swash plate holder 145B (that is, the common swash plate holder <NUM>), and than the sub-plate 170B.

The inner surfaces of the main plate 160B and the sub-plate 170B are provided with engagement concave portions into which the common swash plate holder <NUM> and the center section 150B are engaged in a manner to prevent the HST preassembly from moving in the axial line direction.

In the present embodiment, as illustrated in <FIG> and <FIG>, the inner surface of the main plate 160B is provided with a swash plate holder-directed concave portion <NUM> forming a step portion 350a that engages with an end surface of the common swash plate holder <NUM> that is on a far side from the center section 150B, and a center section-directed concave portion <NUM> forming a step 355a that engages with an end surface of the center section 150B that is on a far side from the common swash plate holder <NUM>, as the engagement concave portions.

Also, the inner surface of the sub-plate 170B is provided with a swash plate holder-directed concave portion <NUM> forming a step portion 360a that engages with the end surface of the common swash plate holder <NUM> that is on the far side from the center section 150B, and a center section-directed concave portion <NUM> forming a step portion 365a that engages with the end surface of the center section 150B that is on the far side from the common swash plate holder <NUM>, as the engagement concave portions.

Providing such a configuration allows the main plate 160B and the sub-plate 170B to stabilize the supporting state of the HST preassembly.

A still another embodiment of the HST according to the present invention will be described below with reference to the accompanying drawings.

<FIG> illustrates a vertical cross-sectional view of an HST 100C according to the present embodiment in a state of being mounted on the transmission case <NUM>, as viewed from the inside of the transmission case <NUM>.

In the figure, the same components as those in the first and second embodiment described above are designated by the same reference numerals and the description thereof will be omitted as appropriate.

The HST 100C according to the present embodiment is in common with the HST 100A according to the first embodiment in that the pump main body <NUM> and the motor main body <NUM> are respectively arranged on one side and the other side in the thickness direction of the center section 150C, but differs from the HST 100A in that the axial line positions of the pump main body <NUM> and the motor main body <NUM> are displaced from each other.

That is, in the HST 100C according to the present embodiment, the pump main body <NUM> is arranged on one side in the thickness direction of the center section 150C, while the motor main body <NUM> is arranged on the other side in the thickness direction of the center section 150C with the shaft line parallel to and at a different position from the shaft line of the pump main body <NUM>.

Specifically, as illustrated in <FIG>, the HST 100C includes: a center section 150C, a pump-side swash plate holder 125C, a motor-side swash plate holder 145C, a main plate 160C and a sub-plate 170C that hold or support the center section 150C, the pump-side swash plate holder 125C, and the motor-side swash plate holder 145C in a sandwiched manner in a state where the pump-side swash plate holder 125C and the motor-side swash plate holder 145C are respectively positioned on one side and the other side in the thickness direction of the center section 150B, the pump shaft <NUM> supported in a rotatable manner around the axial line by the center section 150C and the pump-side swash plate holder 125C, the pump main body <NUM> supported by the pump shaft <NUM> in a manner relatively non-rotatable around the axial line with respect to the pump shaft <NUM>, the pump-side swash plate <NUM> having the rear surface supported by the pump-side swash plate holder 125C, the motor shaft <NUM> supported rotatably around the axial line by the center section 150C and the motor-side swash plate holder 145C in a manner to be parallel to the pump shaft <NUM> and to be different in the axial line position, the motor main body <NUM> supported by the motor shaft <NUM> in a manner relatively non-rotatable around the axial line with respect to the motor shaft <NUM>, and the motor-side swash plate <NUM> having the rear surface supported by the motor-side swash plate holder 145B.

Similar to the main plate 160Ain the first embodiment and the main plate 160B in the second embodiment, when viewed along the direction in which the main plate 160C and the sub-plate 170C face one another, the main plate 160C is provided with the extended region <NUM> extending farther outward in the planar direction than the installation space of the center section 150C, the pump-side swash plate holder 125C, and the motor-side swash plate holder 145C, and than the sub-plate 170C.

The inner surfaces of the main plate 160C and the sub-plate 170C are also provided with engagement concave portions into which the pump-side swash plate holder 125C, the center section 150C, and the motor-side swash plate holder 145C are engaged in a manner to prevent the HST preassembly from moving in the axial line direction.

The engagement concave portions for the center section 150C are so formed as to have step portions that engage with the end surfaces of the center section 150C on one side and the other side in the thickness direction.

The engagement concave portion for the pump-side swash plate holder 125C is so formed as to have a step portion that engages with an end surface of the pump-side swash plate holder 125C that is on a far side from the center section 150C.

Claim 1:
An HST (100A-100C) comprising a pump shaft (<NUM>), a pump main body (<NUM>) supported by the pump shaft (<NUM>) in a manner relatively non-rotatable around an axial line with respect to the pump shaft (<NUM>), a pump-side swash plate (<NUM>) defining a capacity of the pump main body (<NUM>), a pump-side swash plate holder (125A-125C) supporting a rear surface of the pump-side swash plate (<NUM>), a motor shaft (<NUM>), a motor main body (<NUM>) supported by the motor shaft (<NUM>) in a manner relatively non-rotatable around an axial line with respect to the motor shaft (<NUM>), a motor-side swash plate (<NUM>) defining a capacity of the motor main body (<NUM>), a motor-side swash plate holder (145A-145C) supporting a rear surface of the motor-side swash plate (<NUM>), and a center section (150A-150C) on which the pump main body (<NUM>) and the motor main body (<NUM>) directly or indirectly abut in a slidable manner around the respective axial lines and which is formed with oil paths (<NUM>) fluidly connecting the pump main body (<NUM>) and the motor main body (<NUM>), the HST (100A-100C) being characterized in that,
the HST (100A-100C) includes a main plate (160A-160C) and a sub-plate (170A-170C) that hold or support the center section (150A-150C), the pump-side swash plate holder (125A-125C) and the motor-side swash plate holder (145A-145C) in a sandwiched manner by inner surfaces of the main plate (160A-160C) and the sub-plate (170A-170C) that face each other,
the main plate (160A-160C) is provided with an extended region (<NUM>) that extends farther outward in a planar direction of the main plate (160A-160C) than an installation space of the center section (150A-150C), the pump-side swash plate holder (125A-125C) and the motor-side swash plate holder (145A-145C), and than the sub-plate as viewed along a direction in which the main plate (160A-160C) and the sub-plate (170A-170C) face each other.