Pump system and axle-driving system

A pump system includes a housing, an input shaft, a pump shaft; a hydraulic pump body, a PTO shaft, a power transmission gear train, and a PTO clutch mechanism. The housing has a narrow gear accommodating space surrounding a region including a mesh point between the first and second transmission gears of the power transmission gear train, a PTO clutch accommodating space which surrounds the PTO clutch mechanism and which is fluidly communicated with the gear accommodating space, and a pair of first and second suction/discharge ports which communicate the internal space of the housing with an outside of the housing. The first suction/discharge port is arranged within the gear accommodating space so as to be positioned in an opposite side to the PTO clutch accommodating space with the mesh point between the first and second transmission gears interposed therebetween.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pump system provided with a hydraulic pump body and a PTO unit, and an axle-driving system which is provided for each drive axle and independently drives the corresponding drive axle in cooperation with an actuator.

2. Background Art

There has been conventionally used in various fields a pump system which includes a hydraulic pump body and a PTO unit and has a structure that an input from a driving source is input to both of the hydraulic pump body and the PTO unit (see, for example, JP-A 2003-291674).

Such a pump system is particularly useful in a working vehicle or the like, for example, because the hydraulic pump body can form a travel transmission path in cooperation with an actuator such as a hydraulic motor body or the like arranged apart from the pump system, and the PTO unit can form a PTO transmission path for transmitting a power to an external working machine.

However, the conventional pump system does not sufficiently take cooling efficiency for a PTO clutch mechanism in the PTO unit into consideration.

In other words, the PTO unit has a PTO shaft, and a PTO clutch mechanism which selectively engages/disengages a power transmission from the driving source to the PTO shaft.

Specifically, the PTO clutch mechanism is accommodated in a housing of the pump system which can reserve oil. The reserved oil within the housing can somewhat cool the PTO clutch mechanism. However, in the case that the reserved oil is retained, it is impossible to expect a sufficient cooling effect.

An aspect of the present invention has been made in view of the conventional art, and a main object of the present invention is to provide a pump system in which a hydraulic pump body and a PTO clutch mechanism are accommodated in a housing which can reserve oil, and which can improve a cooling efficiency for the PTO clutch mechanism.

In addition, there is a known axle-driving system which includes a motor unit forming a non-stepwise speed change device in cooperation with the actuator. The axle-driving system is provided for each drive axle.

The known axle-driving system will be described by taking a case in which a hydraulic pump unit is used as the actuator and a hydraulic motor unit in fluid communication with the hydraulic pump unit is used as the motor unit (e.g., U.S. Pat. No. 4,920,733 or Japanese Utility Model Publication No. S 56-77437).

In the axle-driving systems described in these prior art documents, a turning ability of the vehicles, especially an ability to make a small turn of a vehicle can be advantageously improved since each of the drive axles can be independently driven with changing its rotational speed. The miniaturization of the entire apparatus, however, has been left to be improved.

Particularly, to make a smaller turn of a vehicle, it is preferred to provide with a brake unit for each drive axle. Neither of the prior art documents, however, mentions such a brake unit, and, of course, there is no description as to how the brake unit could be reduced in its capacity and size.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a pump system including a housing capable of reserving oil in an internal space; an input shaft supported by the housing so as to be operatively connected to a driving source; a pump shaft supported by the housing; a hydraulic pump body which is accommodated in the housing and is driven by the pump shaft; a PTO shaft supported by the housing; a power transmission gear train which transmits a power from the input shaft to the pump shaft and the PTO shaft, and is accommodated in the housing; and a PTO clutch mechanism accommodated in the housing so as to be positioned in a power transmission path from the input shaft to the PTO shaft.

The power transmission gear train has at least two first and second transmission gears meshed with each other.

The housing has a narrow gear accommodating space surrounding a region including a mesh point between the first and second transmission gears, a PTO clutch accommodating space which surrounds the PTO clutch mechanism and which is fluidly communicated with the gear accommodating space, and a pair of first and second suction/discharge ports which communicate the internal space of the housing with an outside of the housing.

The first suction/discharge port is arranged within the gear accommodating space so as to be positioned in an opposite side to the PTO clutch accommodating space with the mesh point between the first and second transmission gears interposed therebetween.

With the pump system according to the present invention, it is possible to effectively prevent the oil from being retained within the PTO clutch accommodating space by means of a pump action accompanied with rotating motions of the first and second transmission gears, so that it is possible to improve a cooling efficiency for the PTO clutch mechanism.

Preferably, a first fluid groove extending from the first suction/discharge port to the PTO clutch accommodating space via the mesh point is formed in at least one of a pair of inner surfaces of the housing, the inner surfaces defining the gear accommodating space and facing to each other with the first and second transmission gears interposed therebetween.

With this configuration, it is possible to further elicit the pump action by means of the first and second transmission gears.

More preferably, the first fluid groove extending from the first suction/discharge port to the PTO clutch accommodating space via the mesh point is formed also in the other of the pair of inner surfaces of the housing.

In the above various configurations, preferably, the first suction/discharge port is positioned in an upstream side in a rotational direction of the first and second transmission gears on the basis of the mesh point.

In the above various configurations, the second suction/discharge port may be arranged within the gear accommodating space.

Preferably, the first and second suction/discharge ports are provided in the vicinity of an outer peripheral edge of the first or second transmission gear, and the housing has a partition portion for preventing a direct oil flow between the first and second suction/discharge ports.

Preferably, a second fluid groove extending from the PTO clutch accommodating space to the second suction/discharge port is formed in at least one of a pair of inner surfaces of the housing. The inner surfaces defining the gear accommodating space and facing to each other with the first and the second transmission gears interposed therebetween.

More preferably, the second fluid groove extending from the PTO clutch accommodating space to the second suction/discharge port is formed also in the other of the pair of inner surfaces of the housing.

Preferably, the second fluid groove is formed so as to face an outer peripheral edge of any transmission gear forming the power transmission gear train. In such a case, the second suction/discharge port is positioned in a downstream side in a rotational direction of the transmission gear.

In the above various configurations, the housing may include a base housing for accommodating the power transmission gear train and the PTO clutch mechanism, and a pump case which is detachably coupled to the base housing and accommodates the hydraulic pump body.

Preferably, an opening fluidly communicating the internal space of the pump case with the gear accommodating space is provided in the pump case and the base housing.

In the above various configurations, the pump shaft may include first and second pump shafts, and the hydraulic pump body may include first and second hydraulic pump bodies respectively driven by the first and second pump shafts.

In one embodiment, the first and second hydraulic pump bodies are arranged in parallel.

In the other embodiment, the first and second hydraulic pump bodies are arranged in series.

According to one aspect of the present invention, there is also provided a pump system including a base housing which has an input portion operatively connected to a driving source and which is capable of being directly or indirectly attached to a support member; a pump unit which has first and second pump shafts, first and second hydraulic pump bodies respectively driven by the first and second pump shafts, and a pump case surrounding the first and second hydraulic pump bodies, the pump case being detachably coupled to the base housing; a PTO unit having a PTO shaft and a PTO clutch mechanism accommodated in the base housing in a state of being supported by the PTO shaft; and a power transmission gear train which transmits a power from the input portion to the first pump shaft, the second pump shaft and the PTO shaft, and which is accommodated in the base housing.

The power transmission gear train has first and second transmission gears meshed with each other.

The base housing has a narrow gear accommodating space surrounding a region including a mesh point between the first and second transmission gears, a PTO clutch accommodating space which surrounds the PTO clutch mechanism and which is fluidly communicated with the gear accommodating space, and a pair of first and second suction/discharge ports which fluidly communicates the gear accommodating with an outside of the housing.

The first suction/discharge port is positioned in an opposite side to the PTO clutch accommodating space with the mesh point between the first and second transmission gears interposed therebetween.

A first fluid groove extending from the first suction/discharge port to the PTO clutch accommodating space via the mesh point is formed in at least one of a pair of inner surfaces of the base housing, the inner surfaces defining the gear accommodating space and facing to each other with the first and second transmission gears interposed therebetween.

In one embodiment, the first and second hydraulic pump bodies are arranged in series with the base housing interposed therebetween.

In such a embodiment, the pump case includes first and second pump cases respectively surrounding the first and second hydraulic pump bodies.

In the other embodiment, the first and second hydraulic pump bodies are arranged in parallel on the same side of the base housing.

In such an embodiment, the pump case may be configured so as to surround both of the first and second hydraulic pump bodies.

Alternatively, the pump case may include first and second pump cases respectively surrounding the first and second hydraulic pump bodies.

According to another aspect of the present invention, there is provided an axle-driving system including an axle case, a motor unit and a reduction transmission unit.

The axle case has an outer wall which supports a drive axle in a rotatable manner around its axis and an inner wall which is disposed apart from the outer wall inwardly in the widthwise direction of the vehicle so that the inner end portion of the drive axle in the widthwise direction of the vehicle is positioned between the inner wall and the outer wall.

The motor unit forms a non-stepwise speed change device in cooperation with an actuator disposed apart therefrom. The motor unit includes a motor case which is connected to the inner wall of the axle case, a motor shaft which is supported by the motor case in a rotatable manner around its axis, and a motor body which is accommodated in the motor case while being supported on the motor shaft.

The reduction transmission unit is accommodated in the axle case.

The motor shaft has an outer end portion and an inner end portion in the widthwise direction of the vehicle. The outer end portion protrudes outwardly from the motor case so as to be positioned inside an accommodating space of the axle case, and the inner end portion protrudes outwardly from the motor case.

The inner end portion of the motor shaft is provided with a brake unit.

An axle-driving system according to the present invention is so constructed that the output of the motor unit is transmitted to the drive axle via the reduction transmission unit. Therefore, a motor unit of low-torque and high-speed type, which is highly reliable and compact, can be used as the motor unit.

In addition, the system is so constructed that a brake force is applied to the motor shaft prior to deceleration by the reduction transmission unit, and thus the capacity reduction and miniaturization of the brake unit can be achieved.

Furthermore, since the brake unit is not inserted into the reduction transmission unit, distances between the motor shaft, the intermediate shaft in the reduction transmission unit and the drive axle can be shortened. This effectively enables the miniaturization of the entire apparatus in the radial direction with respect to the drive axle.

In one embodiment, the motor case includes a motor case body and a port block. The motor case body has an outer end portion in the widthwise direction of the vehicle detachably coupled to the inner wall of the axle case, and an inner end portion in the widthwise direction of the vehicle forming an opening into which the motor body can be inserted. The port block is detachably coupled to the motor case body to close the opening in a liquid tight manner and is provided with a pair of hydraulic fluid ports serving as fluid connection ports for the actuator.

In the one embodiment, preferably, a bearing member which supports the motor shaft in a rotatable manner around its axis is provided with the outer end portion of the motor case body. At least a part of the bearing member protrudes outwardly of the motor case body. A recess, which engages the bearing member, is provided on the outer surface of the inner wall of the axle case.

In the one embodiment, preferably, the motor case body is configured to be connectable to the inner wall of the axle case in a first connecting position and in a second connecting position, which is circumferentially displaced by180° from the first connecting position with respect to the motor shaft.

With such a construction, a pair of right and left axle-driving systems can be constructed with identical parts, while the direction of the output adjustment member in the motor unit of the right axle-driving system and the direction of the output adjusting member in the motor unit of the left axle-driving system can be conformed to each other with respect to a traveling direction of the vehicle.

In another embodiment, the motor case includes a motor case body which is integrally formed with the inner wall of the axle case and is provided with an opening into which the motor body can be inserted at an inner end portion in the widthwise direction of the vehicle; and a port block which is detachably coupled to the motor case body to close the opening in a liquid tight manner and is provided with a pair of hydraulic fluid ports serving as fluid connection ports for the actuator.

In the above various configurations, preferably, the motor case body is configured to be connectable to the port block in a first connecting position and in a second connecting position which is circumferentially displaced by 180° opposite from the first connecting position with respect to the motor shaft.

Such a construction allows the conduit arrangements of the pair of right and left axle-driving systems to be the same, thereby piping workability could be enhanced.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a preferable embodiment of a pump system according to the present invention will be described with reference to the accompanying drawings.

FIGS. 1 and 2are respectively a side view and a plan view of a working vehicle1to which a pump system100in accordance with this embodiment is applied.FIG. 3is a hydraulic circuit diagram of the working vehicle1.

As shown inFIGS. 1 and 2, the working vehicle1includes a vehicle frame30, a driving source40mounted to the vehicle frame30, the pump system100operatively connected to the driving source40, a pair of first and second hydraulic motor units10and20hydraulically connected to the pump system100, and a pair of right and left driving wheels50respectively driven by the pair of first and second hydraulic motor units10and20.

The pump system100forms a non-stepwise speed change device for traveling in cooperation with the pair of first and second hydraulic motor units10and20of the working vehicle1and, also, forms a part of a PTO transmission mechanism for transmitting a driving power to a working machine (a mower in an illustrated embodiment) of the working vehicle1.

In this embodiment, the driving source40is supported in a vibration-absorbing manner in a rear region of the vehicle frame30. Further, the pump system100is supported to the vehicle frame30so as to be positioned in a front side of the driving source40.

Herein, reference numerals60,70and80inFIGS. 1 and 2respectively denote a caster wheel, a mower operatively driven by the driving source40, and a discharge duct forming a conveyance path for conveying the grass reaped by the mower70to a rear side of the vehicle.

FIGS. 4 to 6are respectively a front view, a plan view and a side view of the pump system100.

FIG. 7is a horizontal plan view of the pump system100taken along line VII-VII inFIG. 4.

FIG. 8is a vertical side view of the pump system100taken along line VIII-VIII inFIG. 7.

As shown inFIGS. 4 to 8, the pump system100includes a housing110supported to a support member such as the vehicle frame30, an input shaft210supported to the housing110so as to form an input end where one end is operatively connected to the driving source40, first and second pump shafts310aand310bsupported to the housing110, first and second hydraulic pump bodies320aand320bwhich are accommodated in the housing110and are respectively driven by the first and second pump shafts310aand310b, a PTO shaft610supported to the housing110, a power transmission gear train250which transmits a power from the input shaft210to the first pump shaft310a, the second pump shaft310band the PTO shaft610and is accommodated in the housing110, and a PTO clutch mechanism650accommodated in the housing110so as to be positioned in a power transmission path from the input shaft210to the PTO shaft610.

The housing110accommodates the hydraulic pump bodies320aand320b, the power transmission gear train250and the PTO clutch mechanism650, and has a structure that an interior space thereof can be utilized as an oil reservoir.

Specifically, as shown inFIGS. 7 and 8, the housing110has a pump accommodating space110A for accommodating the first and second hydraulic pump bodies320aand320b, a gear accommodating space110B surrounding a region including a mesh point T between below mentioned first and second transmission gears251and252forming the power transmission gear train250, a PTO clutch accommodating space110C which accommodates the PTO clutch mechanism650and which is fluidly communicated with the gear accommodating space110B, and a pair of first and second suction/discharge ports111P and112P for opening the interior space to an outside of the housing110.

As shown inFIGS. 7 and 8, in this embodiment, the housing110has a base housing120and a pump case150. The base housing120defines the gear accommodating space110B and the PTO clutch accommodating space110C, and is provided with the first and second suction/discharge ports111P and112P. The pump case150is detachably coupled to the base housing120and defines the pump accommodating space110A.

The base housing120has first and second housing portions121aand121bwhich are detachably coupled to each other so as to form the gear accommodating space110B and the PTO clutch accommodating space110C.

Specifically, the first housing portion121ahas a first end wall122aformed so as to support the input shaft210, and a first peripheral wall125aextending to a downstream side (a front side in the vehicle in this embodiment) in a transmitting direction of the input shaft210from a peripheral edge portion of the first end wall122a.

The second housing portion121bhas a second end wall122bformed so as to support the input shaft210, and a second peripheral wall125bextending to an upstream side (a rear side in the vehicle in this embodiment) in the transmitting direction of the input shaft210from a peripheral edge portion of the second end wall122b.

The base housing120has a structure that the gear accommodating space110B and the PTO clutch accommodating space110C are formed by coupling the first and second housing portions121aand121bto each other in a state of contacting an end face of the first peripheral wall125aand an end face of the second peripheral wall125b.

Specifically, as shown inFIGS. 6 and 8, the first end wall122ahas a first gear region123acorresponding to the gear accommodating space110B, and a first PTO clutch region124acorresponding to the PTO clutch accommodating space110C.

The first PTO clutch region124ais expanded to the upstream side in the transmitting direction of the input shaft210from the first gear region123a.

In the same manner, the second end wall122bhas a second gear region123bcorresponding to the gear accommodating space110B, and a second PTO clutch region124bcorresponding to the PTO clutch accommodating space110C (seeFIGS. 6 and 8).

The second PTO clutch region124bis expanded to the downstream side in the transmitting direction of the input shaft210from the second gear region123b.

The first and second gear regions123aand123bare formed so as to extend closely and approximately in parallel to each other in a state of coupling the first and second housing portions121aand121b, so that the narrow gear accommodating space110B is defined.

On the other hand, the first and second PTO clutch regions124aand124bare apart from each other in such a manner that the PTO clutch accommodating space110C which can accommodate the PTO clutch mechanism650is defined between the first and second PTO clutch regions124aand124b.

As shown inFIG. 8, the first PTO clutch region124ais provided with an opening126, and the opening126is formed so as to be sealed in a liquid tight manner by a lid member130detachably coupled to the first end wall122a.

In this embodiment, the base housing120is formed so as to be supported to the vehicle frame30via an attachment stay140.

Specifically, as shown inFIGS. 4,5and7, a pair of right and left attachment stays140are coupled to the peripheral wall (the first peripheral wall125ain the illustrated embodiment) of the base housing120.

Then, the pair of attachment stays140are respectively coupled to a pair of right and left main frames31in the vehicle frame30, so that the base housing120is supported to the vehicle frame30(seeFIG. 2).

A configuration of the pump case150will be described later.

The pump system100according to this embodiment has an auxiliary pump unit500operatively driven by the input shaft210, in addition to the aforementioned configuration.

Specifically, in this embodiment, as shown inFIGS. 7 and 8, the input shaft210is supported by the first end wall122ain a state that a first end211forming the input end protrudes outward, and is supported by the second end wall122bin a state that a second end212extends outward.

Further, the auxiliary pump unit500includes an auxiliary pump body510driven by the second end212of the input shaft210, and an auxiliary pump case520coupled to the second end wall122bso as to surround the auxiliary pump body510.

The first and second pump shafts310aand310bare supported to the housing110in a state of being operatively connected to the input shaft210via the power transmission gear train250.

In this embodiment, as shown inFIGS. 7 and 8, the power transmission gear train250includes the first transmission gear251supported by the input shaft210in a relatively non-rotatable manner, and the second transmission gear252which is meshed with the first transmission gear251and is supported by both the first and second pump shafts310aand310bin a relatively non-rotatable manner.

In other words, in this embodiment, as shown inFIG. 7, the first and second pump shafts310aand310bare supported by the base housing120so as to be positioned coaxially.

Specifically, the first pump shaft310ais supported by the first housing portion121ain such a manner that a base end is positioned within the gear accommodating space110B and a tip end protrudes outward so as to be extended to an opposite side to the second pump shaft310b.

On the other hand, the second pump shaft310bis supported by the second housing portion121bin such a manner that a base end is positioned within the gear accommodating space110B and a tip end protrudes outward so as to be extended to an opposite side to the first pump shaft310a.

Further, the second transmission gear252is supported on each of the base ends of the first and second pump shafts310aand310bin a relatively non-rotatable manner.

The first and second hydraulic pump bodies320aand320bare respectively driven by outer extending portions of the first and second pump shafts310aand310b.

In other words, in this embodiment, the first and second hydraulic pump bodies320aand320bare respectively arranged so as to be positioned at a first side (a rear side of the vehicle in the illustrated embodiment) and a second side (a front side of the vehicle in the illustrated embodiment) with the base housing120interposed therebetween.

As shown inFIG. 3, the first hydraulic pump body320ais fluidly connected to a first hydraulic motor body11in the first motor unit10via a pair of first hydraulic fluid lines400a.

The first hydraulic pump body320aand the first hydraulic motor body11are configured such that at least one of them is of a variable displacement type, thereby forming a first HST variably driving one of the drive wheels50.

In the same manner, the second hydraulic pump body320bis fluidly connected to a second hydraulic motor body21in the second motor unit20via a pair of second hydraulic fluid lines400b.

The second hydraulic pump body320band the second hydraulic motor body21are configured such that at least one of them is of a variable displacement type, thereby forming a second HST variably driving the other of the drive wheels50.

In this embodiment, the first and second hydraulic pump bodies320aand320bare of the variable displacement type, and the first and second hydraulic motor bodies11and12are of a fixed displacement type.

The first hydraulic pump body320ahas a piston unit321aperforming a reciprocating motion in accordance with a rotation of the first pump shaft310a, and a cylinder block322asupporting the piston unit321ain a reciprocatable manner.

As described above, in this embodiment, the first hydraulic pump body320ais of the variable displacement type.

Accordingly, the first pump body320aincludes an output adjusting member323afor adjusting suction/discharge rates by changing a slidable range of the piston unit321a, in addition to the aforementioned configuration.

In this embodiment, a movable swash plate is employed as the output adjusting member323a, and a shoe provided at a tip end of the piston unit321ais brought into contact therewith.

The output adjusting member323acan be externally operated by a control shaft324a. In this embodiment, a trunnion shaft linked with the output adjusting member323avia an arm is employed as the control shaft324a.

Herein, the second hydraulic pump body320bhas substantially the same configuration as the first hydraulic pump body320a. Accordingly, with regard to constituent elements of the second hydraulic pump body320b, a last reference symbol “a” in the first hydraulic pump body320ais replaced by reference symbol “b” in the drawings, and its detailed description will be appropriately omitted.

Herein, the pump case150will be described.

The pump system100according to this embodiment has a first pump case150asurrounding the first hydraulic pump body320a, and a second pump case150bsurrounding the second hydraulic pump body320b, as the pump case150.

As described above, the first and second hydraulic pump bodies320aand320bare arranged so as to be positioned with the base housing120interposed therebetween.

Accordingly, the first and second pump cases150aand150bare respectively coupled to a first side and a second side of the base housing120.

Specifically, as shown inFIGS. 5 and 7, the first pump case150ahas a first case body160ain which a base end is coupled to the first end wall122aand an opening capable of inserting the first hydraulic pump body320atherethrough is provided in a tip end, and a first port block170adetachably coupled to the first case body160aso as to close the opening of the first case body160ain a liquid tight manner.

Herein, the second pump case150bhas substantially the same configuration as the first pump case150aexcept a point that the second pump case150bis coupled to the second end wall122b. Accordingly, with regard to constituent elements of the second pump case150b, a last reference symbol “a” in the first pump case150ais replaced by reference symbol “b” in the drawings, and its detailed description will be appropriately omitted.

The first case body160ahas an end face161acoupled to the first end wall122a, and a peripheral wall162aextending in a pump axial direction from a peripheral edge of the end face161aso as to surround the first hydraulic pump body320a, and a free end side of the peripheral wall portion162ais set to the opening.

In this embodiment, the end face161aand the peripheral wall162aare formed separately (see toFIG. 7); however, they can be of course integrally formed with each other.

As shown inFIG. 3, a pair of first hydraulic fluid passages410aforming a part of the pair of first hydraulic fluid lines400aare formed in the first port block170a.

Each of the pair of first hydraulic fluid passages410ahas a first end fluidly connected to the first hydraulic pump body320avia a kidney port provided in the first port block170a, and a second end opened to an outer surface of the first port block170aso as to form a first hydraulic fluid port411a.

Further, as shown inFIG. 3, the first port block170ais provided with a first charge oil passage420aguiding charge oil sent from the auxiliary pump unit500to the pair of first hydraulic fluid passages410a, and a first bypass oil passage430acommunicating between the pair of first hydraulic fluid passages410a.

The first charge oil passage420ahas a first end opened to an outer surface of the first port block170aso as to form a first charge port421a, and a second end fluidly connected to each of the pair of first hydraulic fluid passages410avia a check valve425.

As shown inFIG. 5, in this embodiment, the first charge port421ais provided on an end face in an opposite side to a connection face to the first case body160ain the outer surface of the first port block170a.

The first bypass oil passage430ahas a first end opened to one side face (one side face orthogonal to the end face) of the first port block170a. A switching valve435which communicates/shuts off the first bypass oil passage430ais inserted through the opening in a state of being operatable manner from outsides.

As shown inFIG. 8, the PTO shaft610is supported by the first PTO clutch region124ain the first end wall122aand the second PTO clutch region124bin the second end wall122bin a rotatable manner around its axis.

In this embodiment, the PTO shaft610has a first end (a rear end in the illustrated embodiment) supported by the lid member130closing the opening provided in the PTO clutch region124ain a liquid tight manner, and a second end (a front end in the illustrated embodiment) supported by the second PTO clutch region124b.

The PTO clutch mechanism650is accommodated in the PTO clutch accommodating space110C in a state of being supported by the PTO shaft610.

Specifically, the PTO clutch mechanism650has a driving-side member651which is supported on the PTO shaft610in a relatively rotatable manner and is operatively connected to the input shaft210via the power transmission gear train250.

More specifically, in this embodiment, as shown inFIG. 8, the power transmission gear train250has a third transmission gear253meshed with the first transmission gear251, in addition to the first and second transmission gears251and252.

Further, the driving-side member651is configured in a relatively non-rotatable manner with respect to the third transmission gear253. In this embodiment, the driving-side member651and the third transmission gear253are integrally formed.

Further, the PTO clutch mechanism650has a driving-side friction plate652engaged with the driving-side member651in a relatively non-rotatable manner and in a movable manner in an axial direction, a driven-side member653supported on the PTO shaft610in a relatively non-rotatable manner, a driven-side friction plate654which is mounted on the driven-side member653in a relatively non-rotatable manner and in a movable manner in an axial direction, and is arranged so as to oppose to the driving-side friction plate653, and a clutch member655switching a friction engagement/disengagement of the driving-side friction plate652and the driven-side friction plate654.

The clutch member655has a piston member656frictionally engaging the driving-side friction plate652and the driven-side friction plate654, and a biasing member657biasing the piston member656in a direction of moving the piston member657apart from the driving-side friction plate652and the driven-side friction plate654. Herein, the piston member656brings the driving-side friction plate652and the driven-side friction plate654into friction contact with each other against the biasing force of the biasing member657by means of a hydraulic action, so that the power is transmitted to the driven-side friction member653from the driving-side member651.

Further, the pump system100according to this embodiment includes a PTO brake mechanism660applying a braking force to the PTO shaft610contradictory against the PTO clutch mechanism650.

In other words, the PTO brake mechanism660operatively applies the braking force to the PTO shaft610when the driving-side friction plate652and the driven-side friction plate654are not engaged, and releases the braking force when the driving-side friction plate652and the driven-side friction plate654are engaged.

The pump system100has the following configuration for circulating the oil reserved within the housing110without additional member.

FIG. 9is an end view of the first housing portion121ataken along line IX-IX inFIG. 8.

Specifically, in the pump system100according to this embodiment, as shown inFIGS. 7 and 8, an inner surface of the first gear region123adefining the gear accommodating space110B is close to first side faces of the first and second transmission gears251and252, and an inner surface of the second gear region123bdefining the gear accommodating space110B is close to second side faces of the first and second transmission gears251and252.

Further, as shown inFIG. 9, one (the first suction/discharge port111P) of the pair of first and second suction/discharge ports111P and112P is arranged within the gear accommodating space110B so as to be positioned in an opposite side to the PTO clutch accommodating space110C with the mesh point T between the first and second transmission gears251and252interposed therebetween.

With this configuration, it is possible to efficiently suck the oil into the PTO clutch accommodating space110C or discharge the oil from the PTO clutch accommodating space110C, by utilizing rotating motion of the first and second transmission gears251and252.

In other words, for example, in the case that the first suction/discharge port111P is used as the suction port (seeFIG. 3), as in this embodiment, it is possible to promote to suck the oil from the first suction/discharge port111P by setting the rotational direction of the first and second transmission gears251and252in such a manner that the first suction/discharge port111P is positioned in an upstream side in the rotational direction of the first and second transmission gears251and252with reference to the mesh point T between the first and second transmission gears251and252.

As is different from this, in the case that the first suction/discharge port111P is used as the discharge port, it is possible to promote to discharge the oil from the first suction/discharge port111P by setting the rotational direction of the first and second transmission gears251and252in such a manner that the first suction/discharge port111P is positioned in a downstream side in the rotational direction of the first and second transmission gears251and252with reference to the mesh point T of the first and second transmission gears251and252.

As described above, since the pump system100according to this embodiment has the aforementioned configuration, it is possible to promote to suck the oil into the PTO clutch accommodating space110C or discharge the oil from the PTO clutch accommodating space110C, so that it is possible to efficiently circulate the reserved oil within the PTO clutch accommodating space110C so as to efficiently prevent the oil from being retained in the PTO clutch accommodating space110C.

Accordingly, it is possible to improve a cooling efficiency of the PTO clutch mechanism650accommodated in the PTO clutch accommodating space110C.

Preferably, as shown inFIGS. 7 and 9, it is possible to form a first oil groove115extending from the first suction/discharge port111P to the PTO clutch accommodating space110C via the mesh point T, at the inner surface of the first gear region123a.

It is possible to efficiently obtain the pump action by the first and second transmission gears251and252by forming the first oil groove115so as to securely circulate the oil within the PTO clutch accommodating space110C.

More preferably, as shown inFIG. 7, it is possible to form the first oil groove115extending from the first suction/discharge port111P to the PTO clutch accommodating space110C via the mesh point T, also at the inner surface of the second gear region123b.

In this embodiment, the other (the second suction/discharge port112P in the illustrated embodiment) of the pair of first and second suction/discharge ports111P,112P is provided so as to be opened to an inside of the gear accommodating space110B (seeFIG. 9).

Preferably, the second suction/discharge port112P is arranged in such a manner that it is possible to promote to discharge/suck the oil from the second suction/discharge port112P by utilizing rotating motion of any transmission gear forming the power transmission gear train250.

Specifically, the second suction/discharge port112P is arranged in the vicinity of an outer peripheral edge of one transmission gear (the first transmission gear251in this embodiment) forming the power transmission gear train250.

As described above, in this embodiment, since the first suction/discharge port111P is utilized as the suction port, the second suction/discharge port112P is utilized as the discharge port.

Further, the second suction/discharge port112P is positioned in the downstream side in the rotating direction of the one transmission gear (the first transmission gear251in this embodiment), so that it is possible to promote to discharge the oil reserved in the PTO clutch accommodating space110C from the second suction/discharge port112P, by utilizing the pump action by the one transmission gear.

More preferably, as shown inFIGS. 7 and 9, it is possible to form a second oil groove116extending from the PTO clutch accommodating space110C to the second suction/discharge port112P in a state of facing to the outer peripheral edge of the one transmission gear (the first transmission gear251in this embodiment), in the inner surface of the first gear region123aand/or the inner surface of the second gear region123b.

It is possible to efficiently obtain the pump action by the one transmission gear by forming the second oil groove116.

In this embodiment, the second oil groove116is provided in both of the inner surface of the first gear region123aand the inner surface of the second gear region123b.

More preferably, in order to prevent the oil from directly communicating between the first suction/discharge port111P and the second suction/discharge port112P as much as possible, a partition portion129may be provided in an inner surface of the base housing120(seeFIG. 9).

In this embodiment, as shown inFIG. 9, both of the first and second suction/discharge ports111P and112P are arranged so as to face an outer peripheral edge of the first transmission gear251. Accordingly, the partition portion129is arranged as close as possible to the outer peripheral edge of the first transmission gear251between the first and second suction/discharge ports111P and112P.

With the provision of the partition portion129, it is possible to effectively prevent the oil introduced into the base housing120from the first suction/discharge port111P from being discharged from the second suction/discharge port112P while bypassing the PTO clutch accommodating space110C, and it is possible to improve a circulating efficiency of the oil reserved in the PTO clutch accommodating space110C.

Further, the pump system100according to this embodiment can guide the leak oil from the first and second hydraulic pump bodies320aand320bto the PTO clutch accommodating space110C so as to effectively prevent the leak oil from being retained in the pump case150.

To be concrete, a first opening190afor communicating an internal space of the first pump case150awith an internal space of the base housing120is provided in the end face161aof the first case body150aand the first end wall122aof the base housing120.

In the same manner, a second opening190bfor communicating an internal space of the second pump case150bwith an internal space of the base housing120is provided in the end face161bof the second case body150band the second end wall122bof the base housing120.

Preferably, the first and second openings190aand190bare opened to an inside of the gear accommodating space110B, and are configured in such a manner that the leak oil from the first and second pump cases150aand150bare efficiently guided to the PTO clutch accommodating space110C by utilizing the rotating motion of any transmission gear in the power transmission gear train250.

In this embodiment, as well shown inFIG. 9, the first and second openings190aand190bare respectively arranged so as to face to a first side face and a second side face of the second transmission gear252, and are configured in such a manner that the leak oil flows into the PTO clutch accommodating space110C via the first oil groove115by utilizing the rotating motion of the second transmission gear252.

Herein, a hydraulic circuit of the pump system100will be described.

The pump system100has an external reserve tank900in addition to the aforementioned configuration (seeFIG. 3). The external reserve tank900forms an oil reservoir together with the housing100.

The pump system100has a suction line440which fluidly connects the external reserve tank900and a suction port of the auxiliary pump body510and in which an oil filter910is inserted, a discharge line450fluidly connected to a discharge port of the auxiliary pump body510, and the charge line420, a PTO line460and a working machine line470which are branched from the discharge line450, in addition to the pair of first hydraulic fluid lines400aand the pair of hydraulic fluid lines400b.

The suction line440has a suction conduit441fluidly connected to the external reserve tank900, and a suction oil passage442formed in the auxiliary pump case520.

The suction oil passage442has a first end opened to an outer surface of the auxiliary pump case520so as to form a suction port440P, and a second end fluidly connected to a suction side of the auxiliary pump case body510.

In this embodiment, the oil filter910is connected to the auxiliary pump case520so as to be inserted in the suction oil passage442, as shown inFIG. 8, thereby intending to lighten a burden of a conduit work and a maintenance work.

The discharge line450has a discharge oil passage451formed in the auxiliary pump case520.

The discharge oil passage451has a first end fluidly connected to a discharge side of the auxiliary pump body510.

In this embodiment, a safety valve920is inserted in the discharge oil passage451(seeFIG. 3), and relief oil from the safety valve920is returned to the oil reservoir (the base housing120).

As shown inFIG. 3, the charge line420has a first end fluidly connected to the discharge line450via a resistance valve930, and second ends fluidly connected to the pair of first hydraulic fluid lines400aand the pair of second hydraulic fluid lines400bvia the check valves425.

Specifically, the charge line420includes a charge supplying oil passage422which is formed in the auxiliary pump case520so as to have a first end communicated with the discharge oil passage451and a second end opened to the outer surface to form a charge supplying port400out, and in which the resistance valve930is inserted, the first charge oil passage420aformed in the first port block170a, a second charge oil passage420bformed in the second port block170b, a first charge conduit423afluidly connecting the charge supplying port400out to the first charge port421a, and a second charge conduit423bfluidly connecting the charge supplying port400out to a second charge port421b.

Preferably, the first and second charge conduits423aand423bcan have inner diameters, which are defined based on their lengths, respectively.

In other words, as shown inFIG. 5, the first port block170ais positioned in an opposite side to the auxiliary pump unit500on the basis of the base housing120, and the second port block170bis positioned in the same side as the auxiliary pump unit500on the basis of the base housing120.

In this configuration, the first charge conduit423abecomes longer than the second charge conduit423b.

Accordingly, in this embodiment, an inner diameter of the first charge conduit423ais made larger than an inner diameter of the second charge conduit423b, thereby lowering a loss pressure in the charge line420as much as possible.

The PTO line460has a first end fluidly connected to the discharge line450via an orifice940, and a second end fluidly connected to the PTO clutch mechanism650(seeFIG. 3).

FIG. 10is a cross sectional view of the lid member130taken along line X-X inFIG. 8.

In this embodiment, the PTO line460has a first PTO oil passage461(seeFIG. 7) which is formed in the auxiliary pump case520so as to have a first end communicated with the discharge oil passage451and a second end opened to a joint face with the second housing portion121b, and in which the orifice940is inserted, a second PTO oil passage462(seeFIG. 7) formed in the second housing portion121bso as to have a first end opened to the joint face with the auxiliary pump case520so as to be communicated with the first PTO oil passage461and a second end opened to the joint face with the first housing portion121a, a third PTO oil passage463(seeFIGS. 7 and 8) formed in the first housing portion121aso as to have a first end opened to the joint face with the second housing portion121band a second end opened to the joint face with the lid member130, a communication groove467(seeFIG. 9) provided in the joint face of the first housing portion121aand the second housing portion121bso as to communicate the second PTO oil passage462and the third PTO oil passage463, a fourth PTO oil passage464(seeFIGS. 8 and 10) formed in the lid member130so as to have a first end communicated with the third PTO oil passage463, an axial hole465(seeFIGS. 8 and 10) perforated in the PTO shaft610, and a rotary joint466(seeFIGS. 8 and 10) formed between an inner surface of the support hole of the lid member130and an outer surface of the PTO shaft610so as to fluidly connect the fourth PTO oil passage464and the axial hole465.

As described above, in this embodiment, the PTO line460is constituted by the respective oil passages formed in the auxiliary pump case520, the base housing120and the lid member130, thereby intending to achieve a structure without conduits.

Herein, the lid member130is provided with a PTO clutch ON/OFF valve950, a relief valve960for setting a PTO clutch operating pressure and an accumulator970so that they are inserted in the fourth PTO oil passage464, as shown inFIGS. 3 and 10.

The working machine line470is formed, as shown inFIG. 3, such that the pressure oil in the discharge line450can be supplied to a working machine hydraulic mechanism (a mower elevating hydraulic mechanism75in this embodiment).

In this embodiment, the working machine line470has a working machine supply line470ahaving a first end fluidly connected to the discharge line450via a charge relief valve980and a second end fluidly connected to the working machine hydraulic mechanism75, and a return line480bhaving a first end fluidly connected to the working machine hydraulic mechanism75and a second end fluidly connected to the first suction/discharge port111P in the base housing120.

Specifically, the working machine supply line470ahas a working machine oil passage471formed in the auxiliary pump case520so as to have a first end communicated with the discharge oil passage451and a second end opened to the outer surface to form the working machine port470P, and a supply conduit472extending between the working machine port470P and the working machine hydraulic mechanism75.

Herein, the charge relief valve980is installed in the auxiliary pump case520so as to be inserted in the working machine oil passage471.

The return line470bhas a return conduit473having a first end fluidly connected to the working machine hydraulic mechanism75and a second end fluidly connected to the first suction/discharge port111P.

As shown inFIG. 3, in this embodiment, an oil cooler990is inserted in the return conduit473, and it is possible to further improve a cooling efficiency of the PTO clutch mechanism650by returning the cooled oil to the base housing120.

In this embodiment, the pump system100is configured such that the first and second hydraulic pump bodies320aand320bare tandem arranged along the axial direction of the pump shaft; however, the first and second hydraulic pump bodies320aand320bmay be arranged or positioned in parallel in place thereof.

In the aspect in which the first and second hydraulic pump bodies320aand320bare arranged in parallel, the first and second pump shafts310aand310bare arranged in parallel to each other. In the case that the first and second pump shafts are arranged in parallel, it is possible to use any one of the first and second pump shafts310aand310bas the input shaft210(seeFIG. 19), or to use an independent input shaft210which is separate from the first and second pump shafts310aand310bas the input shaft210(seeFIG. 20).

Further, in this embodiment, two hydraulic pump bodies (the first and second hydraulic pump bodies320aand320b) are provided; however, only one hydraulic pump body may be provided, or three or more hydraulic pump bodies may be provided, in place thereof.

A preferred embodiment of an axle-driving system according to another aspect of the present invention will be described below with reference to the accompanying drawings.

An axle-driving system according to the present invention includes a motor unit which forms a non-stepwise speed change in cooperation with an actuator such as a hydraulic pump unit and drives a corresponding drive axle, so that the axle-driving system drives the corresponding drive axle with changing its rotational speed in cooperation with the actuator.

It should be noted that this embodiment is described with an example in which a hydraulic pump unit is used as the actuator and a hydraulic motor unit which constitutes HST in cooperation with the hydraulic pump unit is used as the motor unit. However, an axle-driving system according to the present invention also covers an embodiment in which an electric motor unit is used as the motor unit. When such an electric motor unit is used, an electric generator or the like is used as the actuator.

First, a mode of a vehicle to which axle-driving systems10,20according to this embodiment are applied will be described.

FIGS. 11-13are a schematic side view, a schematic plan view and a hydraulic circuit diagram, respectively, of a vehicle1to which the axle-driving systems10,20according to this embodiment are applied.

As shown inFIGS. 11 and 12, the vehicle1includes a vehicle frame30having a pair of main frames31arranged along the longitudinal direction of the vehicle; an engine40which is supported on the vehicle frame30; a hydraulic pump system100which receives the output from the engine40via a flywheel45; a pair of driving wheels50; a pair of first and second drive axles50a,50bwhich are connected to each of the pair of the driving wheels50in a non-rotatable manner around its axis; and first and second axle-driving systems10,20according to this embodiment, which are so constructed as to drive the first and second drive axles50a,50bindependently.

It should be noted that in the embodiment shown in the FIG., the vehicle1includes a caster wheel60supported to the front of the vehicle frame30, a mower70installed between the caster wheel60and the driving wheels50with respect to the longitudinal direction of the vehicle1; and a discharge duct80forming a conveyance path for conveying the grass mowed by the mower70rearwardly of the vehicle, in addition to the above-mentioned construction.

As shown inFIGS. 11 and 12, the engine40is supported in a vibration-absorbing manner on the pair of main frames31to the rear of the drive axles50a,50bvia a vibration-absorbing rubber.

In the form shown in the FIGS., the engine40is supported on the pair of main frames31at four front, rear, right and left points via vibration-absorbing rubbers.

As shown inFIGS. 11 and 12, the hydraulic pump system100is supported on the pair of main frames31via attachment stays140to the front of the engine40.

As shown inFIGS. 11 to 13, the hydraulic pump system100includes an input shaft210having an input end211which is operatively connected to the engine40via the flywheel45and a transmission shaft46with a universal joint; a first hydraulic pump unit300awhich acts as a power source for a motor unit1050described later in the first axle-driving system10; a second hydraulic pump unit300bwhich acts as a power source for the motor unit1050described below in the second axle-driving system20; a PTO unit600which acts as a power source for a working device (the mower70in this embodiment) attached to the working vehicle1; and a power transmission gear train250which transmits power from the input shaft210to the first and second hydraulic pump units300a,300band to the PTO unit600.

The first and second hydraulic pump units300a,300bform first and second HSTs, respectively, in cooperation with the hydraulic motor units in the first and second axle-driving systems10,20.

Specifically, as shown inFIG. 13, the first hydraulic pump unit300aincludes a first pump shaft310awhich is operatively connected to the input shaft210via the power transmission gear train250; and a first hydraulic pump body320adriven by the first pump shaft310a.

As described below, the first hydraulic pump body320aand a hydraulic motor body1300in the first axle-driving system10are hydraulically connected via a pair of first hydraulic fluid lines400a, and at least one of these is of variable-displacement type.

Likewise, as shown inFIG. 13, the second hydraulic pump unit300bincludes a second pump shaft310bwhich is operatively connected to the input shaft210via the power transmission gear train250; and a second hydraulic pump body320bdriven by the second pump shaft310b.

The second hydraulic pump body320band a hydraulic motor body1300described later in the second axle-driving system20are hydraulically connected via a pair of second hydraulic fluid lines400b, and at least one of these is of variable-displacement type.

It should be noted that in this embodiment, the first and second hydraulic pump bodies320a,320bare of variable-displacement type, and the first and second hydraulic motor bodies, of which details are described later, are of fixed-displacement type.

As shown inFIG. 13, the PTO unit600includes a PTO shaft610; a PTO clutch mechanism650inserted between the power transmission gear train250and the PTO shaft610; and a PTO brake mechanism660which counteracts the PTO clutch mechanism650.

It should be noted that the pump system100shown inFIGS. 11 to 13includes an auxiliary pump unit500operatively driven by the input shaft210in addition to the above construction.

More specifically, the auxiliary pump unit500includes a main auxiliary pump body510which is operatively driven by the input shaft210; and an auxiliary pump case520surrounding the main auxiliary pump body510(refer toFIG. 13).

In this embodiment, as shown inFIG. 13, the pressure oil from the auxiliary pump unit500is distributively supplied to a charge line420for supplying pressure oil to the pair of the first hydraulic fluid lines400aand the pair of second hydraulic fluid lines400b; a PTO line460for supplying hydraulic oil to the PTO clutch mechanism650and the PTO brake mechanism660; and a working device line470for supplying hydraulic oil to a hydraulic mechanism75for a working device.

The numeral900inFIGS. 11 and 13denotes an external reserve tank provided separately from the pump system100. The auxiliary pump unit500suctions oil from the external reserve tank900.

FIG. 14shows a front sectional view of the first axle-driving system10along the line XIV-XIV inFIG. 12.FIG. 15Ashows an end view of the first axle-driving system10along the line XV inFIG. 14.

As shown inFIGS. 14andFIG. 15A, the first axle-driving system10includes an axle case1000which rotatably supports the corresponding first drive axle50aaround the axis: the hydraulic motor unit1050connected to and supported by the axle case1010; and a reduction transmission unit1500which transmits the output of the hydraulic motor unit1100to the first drive axle50awith reducing its rotational speed.

As shown inFIG. 14, the axle case1000is so constructed that it is connected to the corresponding main frame31in such a state that it is situated outwardly of the corresponding main frame31in the widthwise direction of the vehicle via a suitable attachment stay (not shown).

As mentioned above, disposing the axle case1000outwardly of the corresponding main frame31in the widthwise direction of the vehicle ensures a free space between the pair of main frames31. Therefore, the modifications between a center discharge type (refer toFIG. 11) in which the discharging duct80for the mower70is disposed between the pair of drive axles50a,50b, and other types such as a side discharge type can be easily performed.

More specifically, the axle case1000includes an outer wall1011which supports the corresponding drive axle (the first drive axle50ain the first axle-driving system10) in a rotatable manner around the axis; and an inner wall1021which is disposed apart from the outer wall1011inwardly in the widthwise direction of the vehicle so that the inner end portion of the corresponding drive axle is situated between the inner wall1021and the outer wall1011.

Specifically, the first axle case1000is so configured that an accommodating space1000S is defined by the outer wall1011and the inner wall1021, causing the inner end portion of the corresponding drive axle to be positioned inside the accommodating space1000S.

In this embodiment, the axle case1000has an outer member1010which has the outer wall1011; and an inner member1020which has the inner wall1021. The outer member1010and the inner member1020are detachably connected by a fastening member1030such as a bolt.

It should be noted that the numeral1040inFIG. 15Adenotes frame mounting seats formed on the outer surface of the inner wall1021, and the attachment stays are connected to the frame mounting seats1040.

The hydraulic motor unit1050is hydraulically connected to the corresponding hydraulic pump unit to form an HST in cooperation with the corresponding hydraulic pump unit via a pair of hydraulic fluid lines.

The hydraulic motor unit1050in the first axle-driving system10is, as mentioned above, hydraulically connected to the first hydraulic pump unit300avia the pair of the first hydraulic fluid lines400ato form a closed circuit, constituting the first HST in cooperation with the first hydraulic pump unit300a.

More specifically, as shown inFIG. 14, the hydraulic motor unit1050has a motor case1100connected to the inner wall1021of the axle case1000; a motor shaft1200which is supported by the motor case1100in a rotatable manner around the axis and has an outer end portion in the widthwise direction of the vehicle is positioned inside the accommodating space1000S of the axle case1000; a hydraulic motor body1300which is accommodated in the motor case1100and rotationally drives the motor shaft1200.

The motor case1100has a motor case body1110detachably coupled to the inner wall1021of the axle case10a; and a port block1120detachably connected to the motor case body1110.

The motor case body1110has an end wall1111in contact with the inner wall1021; and a peripheral wall1115extending inwardly in the widthwise direction of the vehicle from the peripheral edge of the end wall1111, and its end face on the opposite side of the inner wall1021is opened.

Preferably, the end wall1111is so configured to be in a concave-convex engagement with the inner wall1021.

Such a construction allows accurate positioning of the motor case body1110with respect to the axle case1000.

In this embodiment, a projection1112is provided on the end wall1111, and a corresponding recess1022is provided on the inner wall1021.

The port block1120is detachably coupled to the motor case body1110in a manner of closing the opening of the motor case body1110via a fastening member1130such as a bolt.

As shown inFIGS. 13-15A, the port block1120is provided with a pair of first hydraulic fluid passages1410constituting a part of the pair of the first hydraulic fluid lines400a.

The pair of first hydraulic fluid passages1410have first ends opened to the inner surface (the surface facing the accommodating space of the motor case body1110) of the port block1120so as to form a pair of kidney ports which are fluidly communicated with a suction side and a discharge side of the hydraulic motor body1300, and second ends opened to the outer surface of the port block1120so as to form a pair of hydraulic fluid ports1411for the corresponding first hydraulic pump unit300a.

The motor shaft1200is supported by the end wall1111of the motor case body1110and the port block1120in a rotatable manner around the axis.

More specifically, the motor shaft1200is rotatably supported around the axis by a bearing member1250disposed in a through-hole1113formed on the end wall1111and a bearing hole1125formed in the port block1120.

Preferably, as shown inFIG. 14, the through-hole1113can have a central portion1113M; and a large diameter portion1113L which is enlarged from the central portion1113M with a step and is opened outwardly in the widthwise direction of the vehicle.

The bearing member1250is disposed in the large diameter portion1113L so that at least part of it is protruded outwardly of the end wall1111in the widthwise direction of the vehicle, and the inner wall1021is provided with a recess1023engaging with the protruding portion of the bearing member1250on its outer surface (the surface facing the end wall1111).

Such a construction allows the bearing member1250to be also used as a positioning member of the motor case body1110with respect to the axle case1000.

More preferably, the motor case body1110can be provided with a sealing member1260which seals the through-hole1113in a liquid tight manner.

In this embodiment, as shown inFIG. 14, the through-hole1113has a small diameter potion1113S which is contracted from the central portion1113M with a step and is opened to the accommodating space of the motor case body1110. The sealing member1260is disposed in the small diameter potion1113S.

Such a construction enables the inner space of the motor case1100to be effectively used as an oil reservoir, and can effectively prevent the leak oil of the hydraulic motor body1300from being leaked to the outside of the motor case1100.

The hydraulic motor body1300includes a cylinder block1310which is relatively non-rotatably supported on the motor shaft1200so as to be situated within the inner space defined by the motor case body1110and the port block1120and which is fluidly connected to the pair of first hydraulic fluid passages1410; a piston1320which is accommodated relatively non-rotatably and reciprocally in the cylinder block1310; and an output adjustment member1330which defines the reciprocating range of the piston1320.

As mentioned above, in this embodiment, the hydraulic motor body1300is of a fixed-displacement type. Therefore, the hydraulic motor body1300includes a fixed swash plate as the output adjustment member1330.

Such a hydraulic motor body1300is so constructed that the hydraulic fluid supplied and discharged via the pair of the first hydraulic fluid lines400acause the piston1320to be reciprocated within the cylinder block1310and to be rotated around the motor shaft1200, whereby the cylinder block1310and the motor shaft1200are rotated around the axis.

The reduction transmission unit1500includes an output gear1510ditched on the motor shaft1200at its outer end portion in the widthwise direction of the vehicle; a first intermediate gear1520meshing with the output gear1510; an intermediate shaft1530provided with the first intermediate gear1520and supported by the axle case1000; a second intermediate gear1540provided non-rotatably relatively to the intermediate shaft1530; and a final gear1550which meshes with the second intermediate gear1540and is relatively non-rotatably supported on the corresponding drive axle50aat its inner end portion in the widthwise direction of the vehicle. The thus reduction transmission unit1500can transmit the rotational power from the motor shaft1200to the corresponding drive axle50awith reducing the rotational speed.

As mentioned above, the first axle-driving system10according to this embodiment includes the reduction transmission unit1500between the hydraulic motor unit1050and the corresponding drive axle50a. Therefore, in the first axle-driving system10, a motor unit of a low-torque and high-speed type, which is highly reliable, can be used as the hydraulic motor unit1050.

As opposed to a high-torque and low-speed motor, the low-torque and high-speed motor has the advantages of smaller dimension, a smaller amount of hydraulic oil leaked and higher volume efficiency.

In addition, the first axle-driving system10according to this embodiment includes a brake unit1600which can apply brake force operatively to the corresponding first drive axle50a.

The brake unit1600is so constructed that it can apply brake force to the motor shaft1200, as shown inFIG. 14.

More specifically, as shown inFIG. 14, the motor shaft1200has the outer end portion in the widthwise direction of the vehicle and the inner end portion in the widthwise direction of the vehicle, both extending outwardly from the motor case1100.

The brake unit1600is connected to the port block1120at its inner end face in the widthwise direction of the vehicle so that brake force can be applied to the motor shaft1200at its inner end portion in the widthwise direction of the vehicle.

As can be seen from the above, the axle-driving system10according to this embodiment is so constructed that brake force can be applied to the motor shaft1200with high speed and low torque before the rotational speed being decelerated by the reduction transmission unit1500. The capacity and the cost of the brake unit1600can be thus reduced.

Based on this point, in this embodiment, the axle-driving system10includes an internal expanding brake unit as the brake unit1600.

FIG. 15Bshows an end view of the first axle-driving system10along the line XV inFIG. 14in which the brake unit1600is represented by a shadow line.

Specifically, as shown inFIGS. 15A and 15B, the internal expanding brake unit has a brake case1630connected to the port block1120and provided with an opening at its inner end face in the widthwise direction of the vehicle; a brake drum1610accommodated in the brake case1630via the opening and relatively supported non-rotatably on the motor shaft1200at its inner end portion in the widthwise direction of the vehicle; a brake shoe1620disposed so as to face the inner peripheral surface of the brake drum1610; a biasing member1670which biases the brake shoe1620away from the inner peripheral surface of the brake drum1610; a brake cover1640which is detachably coupled to the brake case1630in a manner of closing the opening by a fastening member1650such as a bolt; and a brake operation arm1660which presses the brake shoe1620to the inner peripheral surface of the brake drum1610against the biasing force of the biasing member1670.

The internal expanding brake unit is employed as the brake unit1600in this embodiment as mentioned above. It is needless to say, however, a disk brake unit or other brake unit can be also used.

In addition, as mentioned above, the axle-driving system10according to this embodiment is so constructed that brake force can be applied to the motor shaft1200at its inner end portion in the widthwise direction of the vehicle. Therefore, a brake unit need not be disposed inside the reduction transmission unit1500.

Accordingly, the distances between the motor shaft1200and the intermediate shaft1530and corresponding drive axle50acan be shortened. This can achieve the miniaturization of the entire axle-driving system, thereby, for example, accommodating the reduction transmission unit1500within a tire rim51.

FIG. 16shows a front sectional view of the second axle-driving system20along the line XVI, XVI inFIG. 12.

As shown inFIG. 16, the second axle-driving system20has the identical construction to the first axle-driving system10except that it has a different connecting position of the motor case body1110with respect to the axle case1000and the port block1120.

Specifically, the motor case body1110is constructed so as to be connectable with the axle case1000in both a first connecting position shown inFIG. 14and a second connecting position shown inFIG. 16which is circumferentially displaced by 180° from the first connecting position with respect to the motor shaft.

In this embodiment, as shown inFIG. 15A, threaded holes1025, which are circumferentially displaced by 180° to each other based on the corresponding motor shafts50a,50b, are provided on the inner wall1021of the axle case1000, and the motor case body1110is provided with mounting holes or mounting grooves1114corresponding to the threaded holes1025.

In addition, the motor case body1110is connectable to the port block1120without changing the direction of a pair of hydraulic fluid ports1411in the port block1120in both the first and second connecting positions.

Specifically, the motor case body1110in a state of being in the first connecting position is connectable to the port block1120with the pair of hydraulic fluid ports1411directed downwardly (refer toFIG. 14). Also the motor case body1110in a state of being in the second connecting position is connectable to the port block1200with the pair of hydraulic oil ports1411directed downwardly.

That is to say, the motor case body1110can be connected to the port block1120in a first connecting position (refer toFIG. 14) and in a second connecting position (refer toFIG. 16) which is circumferentially displaces by 180° from the first connecting position with respect to the motor shaft.

In this embodiment, as shown inFIG. 15A, four threaded holes1116are provided on the peripheral wall1115of the motor case body1110at its inner end face in the widthwise direction of the vehicle. The four threaded holes1116are disposed at 90° intervals around the corresponding motor shaft in the circumferential direction. The port block1120is provided with mounting holes1126corresponding to the four threaded holes1116.

As mentioned above, the motor case body1110can be connected to the axle case1000and the port block1120in the first connecting position and the second connecting position which is 180° opposite from the first connecting position with respect to the motor shaft. This enables the first and the second axle-driving systems10,20to be constructed with identical parts, while the direction of the fixed swash plate and the hydraulic fluid port in the first axle-driving systems10, and the direction of the fixed swash plate and the hydraulic fluid port in the second axle-driving system20can be conformed to each other, respectively.

Specifically, if a known axle-driving system, in which a motor case is connected to an axle case and a port block only in a single connecting position, is applied to both a pair of right and left drive axles, the direction of a fixed swash plate in the known axle-driving system applied to the right drive axle, and the direction of a fixed swash plate in the known axle-driving system applied to the left drive axle become opposite to each other with respect to the traveling direction of the vehicle.

In that case, a pair of the hydraulic fluid lines that hydraulically connects one of a pair of axle-driving systems and the corresponding hydraulic pump unit need to be crossed.

In contrast, in this embodiment, the first axle-driving system10can be constructed by connecting the motor case body1110to the corresponding axle case1000and the corresponding port block1120in the first connecting position, and the second axle-driving system20can be constructed by connecting the motor case body1110to the corresponding axle case1000and corresponding port block1120in the second connecting position.

Therefore, the first and second axle-driving systems10,20can be constructed with identical parts; the directions of the fixed swash plates of the first axle-driving system10and the second axle-driving system20can be conformed to each other with respect to the traveling vehicle direction of the vehicle; and also the directions of the hydraulic fluid ports1411in the port blocks of the first axle-driving system10and the second axle-driving system20can be conformed to each other with respect to the traveling direction of the vehicle.

Thus, neither of the pair of the first hydraulic fluid lines400anor the pair of second hydraulic fluid lines400bneeds to be crossed.

Preferably, a pair of through-holes1118(refer toFIG. 16) can be provided on the peripheral wall1115of the motor case body1110disposed symmetrically about the motor shaft.

In the axle-driving system (first axle-driving system10) in the first connecting position, one of the pair of through-holes1118is connected to a drain conduit and the other is closed with a plug, while in the axle-driving system (second axle-driving system20) in the second connecting position, one of the pair of through-holes is closed with a plug and the other is connected to the drain conduit.

Such a construction allows the direction of the drain port of the axle-driving system10in which the motor case body1110is connected to the axle case1000and the port block1120in the first connecting position can be the same as the direction of the drain port of the axle-driving system20in which the motor case body1110is connected to the axle case1000and the port block1120in the second connecting position, thereby improving the piping work and achieving the efficient arrangement of the drain conduits.

An axle-driving system according to another embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 17is a front sectional view of the axle-driving system10B according to this embodiment.

It should be noted that the identical components to those in the embodiment 2 are denoted by the identical numerals in this FIG., and their detailed descriptions are omitted.

As shown inFIG. 17, the axle-driving system10B according to this embodiment is identical to the axle-driving system10A according to the embodiment 2 except that the motor case body1110is integrally formed with the inner case member1020of the axle case1000.

Also in the axle-driving system10B having such a construction, the capacity reduction and cost reduction of the brake unit1600can be achieved and the miniaturization of the entire apparatus with respect to the radial direction of the drive axle50acan be achieved.

An axle-driving system according to still another embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 18is a partial front sectional view of the axle-driving system10C according to this embodiment.

It should be noted that the identical components to those in the embodiment 2 or 3 in this Fig. are denoted by the identical numerals, and their detailed descriptions are omitted.

In the embodiments 2 and 3, as mentioned above, the brake case1630accommodating the brake drum1610is separate from the port block1120(refer toFIGS. 14 and 17). In the axle-driving system10C according to this embodiment, the brake case1630is integrally formed with a port block1120C.

Specifically, the axle-driving system10C according to this embodiment includes a port block1120C having a brake case1630integrally formed therewith in place of the port block1120in the axle-driving systems10,10B according to the embodiment 2 or 3.

Also in the axle-driving system10C having such a construction, the capacity reduction and cost reduction of the brake unit1600can be achieved, and the miniaturization of the entire apparatus with respect to the radial direction of the drive axle50acan be achieved.

This specification is by no means intended to restrict the present invention to the preferred embodiments set forth therein. Various modifications to the pump system and the axle-driving system may be made by those skilled in the art without departing from the spirit and scope of the present invention as defined in the appended claims.