Gear transmission

A gear transmission having a speed changing section includes a speed changing gear for setting a speed stage and a shift gear slidably mounted on a rotation support shaft and operated to engage and disengage with the speed changing gear, the speed changing section configured to speed-change inputted power and to output the resultant power via the rotation support shaft. An arrangement is provided for facilitating engagement of the shift gear with the speed changing gear even when respective end faces of the shift gear and the speed changing gear hit each other. A transmission mechanism (20B) is provided for outputting power of a rotation support shaft (24) to a traveling device. The transmission mechanism (20B) has a transmission flexibility portion (80) which allows free rotation of the rotation support shaft (24) by a set rotation angle.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2020-168721 filed Oct. 5, 2020, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a gear transmission.

2. Description of Related Art

The gear transmission includes a speed changing section having a speed changing gear for setting a speed stage and a shift gear slidably mounted on a rotation support shaft and operated to be engaged/disengaged to/from the speed changing gear, the speed changing section configured to speed-change inputted power and to output the resultant power via the rotation support shaft, and a transmission mechanism configured to output the power of the rotation support shaft to a traveling device.

An example of such gear transmission as above is known from e.g. Patent Document 1. The gear transmission disclosed in Patent Document 1 includes, as “speed changing gears”, a second low speed gear, a second high speed gear and a second reverse gear, a speed changing shaft as the “rotation support shaft”, and a first shifter and a second shifter as “shift gears”. Its transmission mechanism is configured such that power of the rotation support shaft is transmitted to a rear wheel differential device via a first speed reducing gear, a second speed reducing gear and a first output shaft and then outputted from the rear wheel differential device to rear wheels and also the power of the rotation support shaft is transmitted to a PTO shaft via the first speed reducing gear, the second speed reducing gear, a transmission gear, a second output shaft, etc., and then outputted from the PTO shaft to front wheels.Patent Document 1: Japanese Unexamined Patent Application No. 2009-67082 document.

SUMMARY OF THE INVENTION

With this kind of conventional gear transmission, when a speed changing operation is to be effected, if respective end faces of the shift gear and the speed changing gear hit each other, ground-contact reaction force applied to the traveling device will be transmitted to the transmission mechanism to act on the rotation support shaft, thus preventing rotation of the shift gear and making engagement of the shift gear with the speed changing gear difficult. Therefore, a troublesome operation procedure is needed, involving removing the shift gear from the speed changing gear first and then sliding the shift gear toward the speed changing gear for re-engagement therewith.

The present invention provides a gear transmission that allows easy engagement of a shift gear with a speed changing gear even when respective end faces of the shift gear and the speed changing gear hit each other.

A gear transmission according to the present invention comprises:

a speed changing section including a speed changing gear for setting a speed stage and a shift gear slidably mounted on a rotation support shaft and operated to be engaged/disengaged to/from the speed changing gear, the speed changing section being configured to speed-change inputted power and to output the resultant power via the rotation support shaft; and

a transmission mechanism configured to output the power of the rotation support shaft to a traveling device, the transmission mechanism having a transmission flexibility portion allowing free rotation of the rotation support shaft by a set rotational angle.

With the above-described arrangement, even if a ground-contact reaction force acting on the traveling device is applied to the transmission mechanism, the rotation support shaft can be rotated by the set rotational angle by the action of the transmission flexibility portion. Consequently, even if the respective end faces of the shift gear and the speed changing gear hit each other, as the shift gear is rotated with the rotation support shaft, so that a relative positional displacement may be readily provided between the shift gear and the speed changing gear to facilitate engagement of the shift gear to the speed changing gear.

In the present invention, preferably:

the transmission mechanism includes:a rotation transmission shaft operably coupled to the rotation support shaft via a gear coupling mechanism,a front wheel output shaft coupled to the rotation transmission shaft for outputting power of the rotation transmission shaft to a front wheel as the traveling device, anda rear wheel differential mechanism coupled to the rotation transmission shaft for outputting power of the rotation transmission shaft to a rear wheel as the traveling device; and

the transmission flexibility portion is provided at a portion of the rotation transmission shaft to which portion the gear coupling mechanism is coupled.

With the above-described arrangement, by simply providing the transmission flexibility portion only at the portion of the rotation transmission shaft to which portion the gear coupling mechanism is coupled, flexibility for the rotation support shaft by the set rotational angle is provided, in spite of the ground-contact reaction force acting on the front wheel and also in spite of the ground-contact reaction force acting on the rear wheel. Thus, with such simple arrangement of providing a small number of transmission flexibility portion (s), engagement of the shift gear with the speed changing gear can be facilitated.

In the present invention, preferably:

the transmission mechanism includes;a first transmission gear gear-coupled to the rotation support shaft,a rear wheel differential mechanism having an input shaft coupled to the first transmission gear and configured to output power from the first transmission gear toward the rear wheel as the traveling device,a second transmission gear gear-coupled to the rotation support shaft,a rotation transmission shaft gear-coupled to the second transmission gear, anda front wheel output shaft coupled to the rotation transmission shaft for outputting power from the rotation transmission shaft to a front wheel as the traveling device; and

the transmission flexibility portion is provided between the first transmission gear and the input shaft and also between the second transmission gear and the rotation transmission shaft.

With the above-described arrangement, free rotation of the rotation support shaft against the ground-contact reaction force acting on the rear wheel is allowed by the transmission flexibility portion provided between the first transmission gear and the input shaft. Similarly, free rotation of the rotation support shaft against the ground-contact reaction force acting on the front wheel is allowed by the transmission flexibility portion provided between the second transmission gear and the rotation support shaft. Thus, in spite of the ground-contact reaction force acting on the front wheel and also in spite of the ground-contact reaction force acting on the rear wheel, engagement of the shift gear with the speed changing gear can be facilitated.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Next, an embodiment as an example of the present invention will be explained with reference to the accompanying drawings.

Incidentally, in the following explanation, with respect to a traveling vehicle body of a multiple-purpose vehicle, the direction of arrow F shown inFIG. 1is defined as “vehicle body front side”, the direction of arrow B shown therein is defined as “vehicle body rear side”, the direction of arrow U shown therein is defined as “vehicle body upper side”, the direction of arrow D shown therein is defined as “vehicle body lower side”, the direction on the near (front) side of the plane of illustration is defined as “vehicle body left side”, and the direction on the far (back) side of the plane of illustration is defined as “vehicle body right side”, respectively.

As shown inFIG. 1, the multiple-purpose vehicle includes a traveling vehicle body having a pair of steerable and drivable left and right front wheels1as “traveling devices” and a pair of drivable left and right rear wheels2as further “traveling devices”. At a front/rear intermediate portion of the traveling vehicle body, a driving section3is formed. In this driving section3, there are provided a driver's seat4and a steering wheel5for steering the front wheels1. At a rear portion of the traveling vehicle body, a load-carrying deck7is provided. Beneath the load-carrying deck7, there is provided an engine8outputting power to the front wheels1and the rear wheels2.

FIG. 2is a plan view showing a traveling power transmission system configured to transmit power from the engine8to the front wheels1(seeFIG. 1) and the rear wheels2(seeFIG. 1). This traveling power transmission system includes a stepless speed changing device10configured to speed-change power from the engine8and to output the resultant power to the front wheels1and the rear wheels2, and a gear transmission20. The gear transmission20is provided rearwardly of the engine8. The stepless speed changing device10and the gear transmission20are arranged in series with each other so that the output of the stepless speed changing device10is inputted to the gear transmission20. In this embodiment, power of an output shaft (not shown) of the engine8is inputted to the stepless speed changing device10and the power speed-changed by the stepless speed changing device10is inputted to the gear transmission20and the power speed-changed by the gear transmission20is outputted from a front wheel output shaft51(seeFIG. 3) which protrudes forwardly from a lower portion of a transmission case21to the front wheels1. The power speed-changed by the gear transmission20is transmitted from a rear wheel differential mechanism53provided within a rear portion of the transmission case21to the rear wheels2via left and right rear wheel driving shafts53b. The front wheel output shaft51is coupled to a front wheel differential mechanism (not shown) provided inside a front wheel driving case9(seeFIG. 1) via a rotational shaft51a(seeFIG. 1).

As shown inFIG. 2, the stepless speed changing device10is provided between a lateral side of the engine8and a lateral side of the gear transmission20. This stepless speed changing device10is constituted of a hydrostatic stepless speed changing device. The stepless speed changing device10is configured as a main speed changing device for changing driving speeds of the front wheels1and the rear wheels2. Speed changing operations of the stepless speed changing device10are effected by a stepless speed changing operational tool (not shown) provided separately of a stepped speed changing operational tool66(seeFIG. 2) for effecting speed changing operations of the gear transmission20.

The stepless speed changing device10is configured as a main speed changing device for changing driving speeds of the front wheels1and the rear wheels2. Speed changing operations of the stepless speed changing device10are effected by a stepless speed changing operational tool (not shown) coupled to an operational portion of the stepless speed changing device10.

The gear transmission20, as shown inFIG. 2, includes the transmission case21and is arranged in such a manner that the lateral width direction of the transmission case21is aligned with the lateral width direction of the traveling vehicle body. As shown inFIG. 4,FIG. 5andFIG. 6, the gear transmission20includes a speed changing section20A having a first shaft23rotatably supported to a front upper portion of the transmission case21, etc. and a transmission mechanism20B configured to output power of the speed changing section20A to the front wheels1and the rear wheels2.

The speed changing section20A, as shown inFIGS. 5 and 6, includes, in addition to the first shaft23, a second shaft24and a third shaft25which are provided inside the transmission case21and arranged side by side in parallel with the first shaft23. The first shaft23, the second shaft24and the third shaft25are provided to extend along the lateral width direction of the transmission case21.

One end side of the first shaft23protrudes from the transmission case21toward the stepless speed changing device10and is coupled to an output pulley13of the stepless speed changing device10. The first shaft23acts as an input shaft of the gear transmission20. As shown inFIGS. 5 and 6, inside the transmission case21, the first shaft23mounts thereon a first input gear26, a second input gear27, a third input gear28, and a fourth input gear29.

As shown inFIGS. 5 and 6, a second shaft24, as a “rotation support shaft”, rotatably mounts thereon a first speed (speed changing) gear31meshed with the first input gear26for setting a forward first speed, a second speed (speed changing) gear32meshed with the second input gear27for setting a forward second speed, and a third speed (speed changing) gear33meshed with the third input gear28for setting a forward third speed. A reverse-rotation gear34meshed with the fourth input gear29is mounted on a third shaft25, and a reverse traveling gear35meshed with the reverse-rotation gear34for setting reverse first speed is rotatably mounted on the second shaft24.

As shown inFIG. 7, the outside diameter of the first speed gear31is set larger than the outside diameter of the third speed gear33. The outside diameter of the first speed gear31is set also larger than the outside diameter of the second speed gear32. The outside diameter of the second speed gear32is set larger than the outside diameter of the third speed gear33. The first speed gear31whose outside diameter is larger than the outside diameter of the second speed gear32and the outside diameter of the third speed gear33is located on more inner side than the second speed gear32and located also on more inner side than the third speed gear33, in the lateral width direction of the transmission case21.

As shown inFIG. 7, between the first speed gear31and the third speed gear33, a first shift gear36is supported to the second shaft24. The first shift gear36is supported on the second shaft24to be slidable to a transmission state in which the first shift gear36is meshed with a teeth portion31aformed at a lateral portion of the first speed gear31to operably couple the first speed gear31to the second shaft24, a transmission state in which the first shift gear36is meshed with a teeth portion33aformed at a lateral portion of the third speed gear33to operably couple the third speed gear33to the second shaft24, and a neutral state in which the first shift gear36is removed from the teeth portion31aof the first speed gear31to release the operable coupling of the first speed gear31relative to the second shaft24and also removed from the teeth portion33aof the third speed gear33to release the operable coupling of the third speed gear33relative to the second shaft24.

As shown inFIG. 7, between the second speed gear32and the reverse traveling gear35, a second shift gear37is supported to the second shaft24. The second shift gear37is supported on the second shaft24to be slidable to a transmission state in which the second shift gear37is meshed with a teeth portion32aformed at a lateral portion of the second speed gear32to operably couple the second speed gear32to the second shaft24, a transmission state in which the second shift gear37is meshed with a teeth portion35aformed at a lateral portion of the reverse traveling gear35to operably couple the reverse traveling gear35to the second shaft24, and a neutral state in which the second shift gear37is removed from the teeth portion32aof the second speed gear32to release the operable coupling of the second speed gear32relative to the second shaft24and also removed from the teeth portion35aof the reverse traveling gear35to release the operable coupling of the reverse traveling gear35relative to the second shaft24.

As shown inFIG. 6, the transmission mechanism20B includes a fifth shaft49as a “rotation transmission shaft” having one end portion thereof operably coupled to the second shaft24via a gear coupling mechanism40having a fourth shaft41, etc., a front wheel output shaft51operably coupled to the other end of the fifth shaft49via a bevel gear mechanism50for outputting power of the fifth shaft49to the front wheel1, and a rear wheel differential mechanism53having an input gear53athereof operably coupled to an intermediate portion of the fifth shaft49for outputting power of the fifth shaft49to the rear wheel2. The input gear53ais engaged with a transmission gear52provided on the fifth shaft49, thus being operably coupled to this fifth shaft49. The front wheel output shaft51is provided to extend in the front/rear direction of the transmission case21. The fourth shaft41and the fifth shaft49are provided to extend along the lateral width direction of the transmission case21.

The gear coupling mechanism40, as shown inFIG. 6, includes, in addition to the fourth shaft41, a first transmission gear42mounted on the second shaft24, a second transmission gear43mounted at one end portion of the fourth shaft41and meshed with the first transmission gear42, a third transmission gear44provided at the other end portion of the fourth shaft41, and a fourth transmission gear45meshed with the third transmission gear44and provided at one end portion of the fifth shaft49.

As shown inFIG. 7, at an angular portion opposed to the first transmission gear42at the root portion of the reverse traveling gear35, there is formed a stepped portion35bfor mitigating stress concentration. At an angular portion opposed to the first transmission gear42at the root portion of the first speed gear31, there is formed a stepped portion similar to the stepped portion35bof the reverse traveling gear35.

As shown inFIGS. 5 and 7, a first shifter55having a leading end portion55athereof engaged with the first shift gear36and a second shifter56having a leading end portion56athereof engaged with the second shift gear37are slidably supported on a shifter support shaft57. This shifter support shaft57is supported to the transmission case21in parallel juxtaposition with the second shaft24. A shift drum58having a drum axis Y parallel with a support axis X of the shifter support shaft57is rotatably supported to the transmission case21. In the outer circumferential portion of the shift drum58, there are provided a first shifter operating cam portion59to which an operation portion55bof the first shifter55is engaged and a second shifter operating cam portion60to which an operation portion56bof the second shifter56is engaged. The first shifter operating cam portion59and the second shifter operating cam portion60are constituted of guide grooves into which the operation portions56b,56brespectively come into slidable engagement. As the shift drum58is rotated about the drum axis Y, the first shifter55is slid along the shifter support shaft57by the first shifter operating cam portion59to slide the first shift gear36and the second shifter56is slid along the shifter support shaft57by the second shifter operating cam portion60to slide the second shift gear37.

There is provided a speed changing operation shaft61for rotating the shift drum58. Specifically, the speed changing operation shaft61, as shown inFIGS. 5 and 7, extends along the lateral width direction of the transmission case21and is rotatably supported to an upper portion of the transmission case21in parallel juxtaposition with the drum axis Y. As shown inFIG. 7, inside the transmission case21, between one end portion of the speed changing operation shaft61and a supporting shaft portion58aof the shift drum58, there is provided a coupling mechanism62for operably coupling the speed changing operation shaft61with the shift drum58. When the speed changing operation shaft61is rotatably operated, power of the speed changing operation shaft61is transmitted by the coupling mechanism62to the supporting shaft portion58a, whereby the shift drum58is operated.

The coupling mechanism62, as shown inFIGS. 7 and 8, includes a drum operating gear63provided on the support shaft portion58aof the shift drum58and rotatable with the shift drum58and a transmission gear64provided at one end portion of the speed changing operation shaft61as being meshed with the drum operating gear63and rotatable with the speed changing operation shaft61. The transmission gear64is constituted of a fan-shaped gear.

As shown inFIGS. 2 and 7, a stepped speed changing operational tool66is coupled via the coupling mechanism65to the speed changing operation shaft61. The stepped speed changing operational tool66is provided at the driving section3. The coupling mechanism65includes a pivot arm67extended from the end portion of the speed changing operation shaft61opposite to the side where the coupling mechanism62is provided, an operation cable for coupling the pivot arm67to the stepped speed changing operational tool66, etc.

A detent mechanism70is provided for fixing the shift drum58at a rotation operation position where the first shift gear36and the second shift gear37are engaged with each other or under the neutral state. The detent mechanism70is provided inside the transmission case21.

Specifically, the detent mechanism70, as shown inFIGS. 7 and 9, includes a positioning rotation portion71formed at the support shaft portion58aof the shift drum58and a positioning spring73having a coil portion73athereof engaged on a boss portion72aof a positioning arm72.

At five positions in the circumference portion of the positioning rotation portion71, there are provided receded portions74as “positioning action portions”. The positioning arm72is rotatably supported, at a boss portion72aprovided at the base portion thereof, on the speed changing operation shaft61. At the free end portion of the positioning arm72, a roller75is rotatably provided. In operation, as the positioning arm72is pivoted about the speed changing operation shaft61in association with rotation of the positioning rotation portion71, the positioning arm72will be engaged/disengaged with/from the receded portion74by the roller75and with this engagement in the receded portion74, the positioning rotation portion71is fixed in a rotational position corresponding to the rotation operation position of the shift drum58. One end portion of the positioning spring73is retained to the positioning arm72and the other end portion of the positioning spring73is retained to the transmission case21. The positioning arm72is pivotally urged by the positioning spring73to be engaged in the receded portion74.

A rotation potentiometer76is provided for detecting an operation position (operated position) of the speed changing operation shaft61. This rotation potentiometer76, as shown inFIGS. 4 and 7, is provided outside the transmission case21. A meter case76aof the rotation potentiometer76is screw-fixed to the transmission case21. A rotation operation shaft76bof the rotation potentiometer76is disposed such that the axis of this rotation operation shaft76bis positioned on the axis of the speed changing operation shaft61. The rotation operation shaft76band the speed changing operation shaft61are engaged with each other to be rotatable in unison. More particularly, the rotation operation shaft76band the speed changing operation shaft61are engaged with each other to be rotatable in unison, with engagement of the rotation operation shaft76bin a coupling hole provided in the speed changing operation shaft. The engagement between the rotation operation shaft76band the speed changing operation shaft61is realized by the rotation operation shaft76band a non-circular shape of the coupling hole.

The gear transmission20is configured to be speed-changed as an auxiliary speed changing device which changes the driving speeds of the front wheels1and the rear wheels2in a reverse traveling one speed, and forward traveling three speeds, in total four speeds. Speed changing operations of the gear transmission20are effected by the stepped speed changing operational tool66.

More particularly, as shown inFIG. 3, the stepped speed changing operational tool66, in association with pivotal operations thereof, is guided by an operational tool guide77to be switched over to a neutral position [N], a reverse (reverse traveling) position [R], a forward first speed position [UL], a forward second speed position [L] and a forward third speed position [H].

The forward second speed position [L] is an operation position of a lower speed than the forward third speed position [H]. The forward first speed position [UL] is an operation position of a lower speed than the forward second speed position [L]. Switching operations of the stepped speed changing operation tool66to the neutral position [N], the forward third speed position [H], the forward second speed position [L] and the forward first speed position [UL] are effected in this mentioned order. Namely, the stepped speed changing operation tool66is switched from the neutral position [N] to the forward third speed position [H], switched from the forward third speed position [H] to the forward second speed position [L] and switched from the forward second speed position [L] to the forward first speed position [UL].

When the stepped speed changing operation tool66is operated to the neutral position [N], the speed changing operation shaft61is rotated by the operation force of the stepped speed changing operation tool65and in response to the operation force of the speed changing operation shaft61, the shift drum58is rotated to a rotation operation position for realizing the neutral state. Then, the first shifter55is slid by the first shifter operating cam portion59, whereby the first shift gear36is operated by the first shifter55to a state disengaged from the first speed gear31and from the third speed gear33. Further, the second shifter56is slid by the second shifter operating cam portion60, whereby the second shift gear37is operated by the second shifter56to a state disengaged from the second speed gear32and the reverse traveling gear35. As the positioning rotation portion71is rotated in unison with the shift drum58, the positioning arm72is engaged in a first receded portion74aof the receded portions74provided at the five positions and the shift drum58is position-fixed by the detent mechanism70at the rotation operation position providing the neutral state (the rotation operation position where the first shift gear36and the second shift gear37are disengaged). In the gear transmission20, the neutral state is provided, whereby transmission of power of the first shaft23to the second shaft24is stopped and the output to the front wheels1and the rear wheels2is stopped. The gear transmission20is maintained under the neural state by the detent mechanism70. The rotation operation shaft76bof the rotation potentiometer76is rotatably operated by the speed changing operation shaft61and the operation position of the speed changing operation shaft61is detected by the rotation potentiometer76, and the detection result is outputted as detection result of the neutral state of the gear transmission20from the rotation potentiometer76to a display device (not shown) or the like.

When the stepped speed changing operation tool66is operated to the reverse position [R], by the operation force of the speed changing operation shaft61, the shift drum58is operated to the rotation operation position realizing reverse traveling. Then, the first shifter55is slid by the first shifter operating cam portion59and the first shift gear36is operated by the first shifter55to a state disengaged from the first speed gear31and the third speed gear33. Further, the second shifter56is slid by the second shifter operating cam portion60, and the second shift gear37is operated by the second shifter56into a state engaged with the reverse traveling gear35. The positioning rotation portion71is rotated in unison with the shift drum58and the positioning arm72is engaged with a second receded portion74bof the receded portions74provided at the five positions and the shift drum58is maintained by the detent mechanism70at the rotation operation position realizing reverse traveling (the rotation operation position at which the second shift gear37is engaged with the reverse traveling gear35and the first shift gear36is disengaged from the first speed gear31and the third speed gear33). In the gear transmission20, reverse traveling state is provided, whereby the power of the first shaft23is speed-changed into reverse traveling power by a fourth input gear29, a reverse-rotation gear34and a reverse traveling gear35and reverse traveling power is transmitted to the second shaft24and inputted from this second shaft24to the transmission mechanism20B and reverse traveling power is outputted from the front wheel output shaft51to the front wheels1and reverse traveling power is outputted from the rear wheel differential mechanism53to the rear wheels2. The gear transmission20is maintained under the reverse traveling transmission state by the detent mechanism70. The rotation operation shaft76bof the rotation potentiometer76is rotated by the speed changing operation shaft61and the operation position of the speed changing operation shaft61is detected by the rotation potentiometer76and the result of this detection is outputted from the rotation potentiometer76as detection result of the reverse traveling transmission state of the gear transmission20.

When the stepped speed changing operation tool66is operated to the forward third speed position [H], by the operation force of the stepped speed changing operation tool66, the speed changing operation shaft61is rotated and by the operation force of this speed changing operation shaft61, the shift drum58is rotatably operated to the rotation operation position realizing forward third speed. Then, the first shifter55is slid by the first shifter operating cam portion59and the shift gear36is operated by the first shifter55into a state engaged with the third speed gear33. Further, the second shifter56is slid by the second shifter operating cam portion60and the second shift gear37is operated by the second shifter56into a state disengaged from the second speed gear32and the reverse traveling gear35. The positioning rotation portion71is rotated in unison with the shift drum58and the positioning arm72is engaged in a third receded portion74cof the receded portions74provided at the five positions, and the shift drum58is fixed in position by the detent mechanism70at the rotation operation position realizing the forward third speed (the rotation position at which the first shift gear36is engaged with the third speed gear33and the second shift gear37is disengaged from the second speed gear32and from the reverse traveling gear35). In the gear transmission20, there is provided a forward traveling transmission state of the forward traveling third speed, whereby the power of the first shaft23is speed-changed to the forward traveling third speed power by the third input gear28and the third speed gear33and the forward traveling third speed power is transmitted to the second shaft24and inputted from this second shaft24to the transmission mechanism20B and forward traveling third speed power of higher speed than the forward traveling first speed and the forward traveling second speed is outputted from the front wheel output shaft51to the front wheels1, and the forward traveling power of the forward traveling third speed is outputted from the rear wheel differential mechanism53to the rear wheels2. The gear transmission20is maintained under the forward traveling state of the forward third speed by the detent mechanism70. The rotation operation shaft76bof the rotation potentiometer76is rotatably operated by the speed changing operation shaft61and the operation position of the speed changing operation shaft61is detected by the rotation potentiometer76and the result of this detection as detection result of the forward traveling transmission state of the forward traveling third speed of the gear transmission20is outputted from the rotation potentiometer76.

When the stepped speed changing operation tool66is operated to the forward traveling second speed [L], by the operation force of the stepped speed changing operation tool66, the speed changing operation shaft61is rotatably operated and by the operation force of the speed changing operation shaft61, the shift drum58is operated to the rotation operation position realizing forward traveling second speed. Then, the first shifter55is slid by the first shifter operating cam portion59and the first shift gear36is operated by the first shifter55into a state disengaged from the first speed gear31and from the third speed gear33.

Further, the second shifter56is slid by the second shifter operating cam portion60and the second shift gear37is operated by the second shifter56into a state engaged with the second speed gear32. The positioning rotation portion71is rotated in unison with the shift drum58and the positioning arm72is engaged in a fourth receded portion74dof the receded portions74provided at the five positions, and the shift drum58is fixed in position by the detent mechanism70at the rotation operation position realizing the forward second speed (the rotation position at which the first shift gear36is disengaged from the first speed gear31and from the third speed gear33and the second shift gear37is engaged with the second speed gear32). In the gear transmission20, there is provided a forward traveling transmission state of the forward traveling second speed, whereby the power of the first shaft23is speed-changed to the forward traveling second speed power by the second input gear27and the second speed gear32and the forward traveling second speed power is transmitted to the second shaft24and inputted from this second shaft24to the transmission mechanism20B and forward traveling second speed power of lower speed than the forward traveling third speed and also higher speed than the forward traveling first speed and the forward traveling second speed is outputted from the front wheel output shaft51to the front wheels1, and the forward traveling power of the forward traveling second speed is outputted from the rear wheel differential mechanism53to the rear wheels2. The gear transmission20is maintained under the forward traveling state of the forward second speed by the detent mechanism70. The rotation operation shaft76bof the rotation potentiometer76is rotatably operated by the speed changing operation shaft61and the operation position of the speed changing operation shaft61is detected by the rotation potentiometer76and the result of this detection as detection result of the forward traveling transmission state of the forward traveling second speed of the gear transmission20is outputted from the rotation potentiometer76.

When the stepped speed changing operation tool66is operated to the forward traveling first speed [UL], by the operation force of the stepped speed changing operation tool66, the speed changing operation shaft61is rotatably operated and by the operation force of the speed changing operation shaft61, the shift drum58is operated to the rotation operation position realizing forward traveling first speed. Then, the first shifter55is slid by the first shifter operating cam portion59and the first shift gear36is operated by the first shifter55into a state engaged with the first speed gear31. Further, the second shifter56is slid by the second shifter operating cam portion60and the second shift gear37is operated by the second shifter56into a state disengaged from the second speed gear32and from the reverse traveling gear35. The positioning rotation portion71is rotated in unison with the shift drum58and the positioning arm72is engaged in a fifth receded portion74eof the receded portions74provided at the five positions, and the shift drum58is fixed in position by the detent mechanism70at the rotation operation position realizing the forward first speed (the rotation position at which the first shift gear36is engaged with the first speed gear31and the second shift gear37is disengaged from the second speed gear32and from the reverse traveling gear35). In the gear transmission20, there is provided a forward traveling transmission state of the forward traveling first speed, whereby the power of the first shaft23is speed-changed to the forward traveling first speed power by the first input gear26and the first speed gear31and the forward traveling first speed power is transmitted to the second shaft24and inputted from this second shaft24to the transmission mechanism20B and forward traveling first speed power of lower speed than the forward traveling third speed and also higher speed than the forward traveling third speed and the forward traveling second speed is outputted from the front wheel output shaft51to the front wheels1, and the forward traveling power of the forward traveling first speed is outputted from the rear wheel differential mechanism53to the rear wheels2. The gear transmission20is maintained under the forward traveling state of the forward first speed by the detent mechanism70. The rotation operation shaft76bof the rotation potentiometer76is rotatably operated by the speed changing operation shaft61and the operation position of the speed changing operation shaft61is detected by the rotation potentiometer76and the result of this detection as detection result of the forward traveling transmission state of the forward traveling first speed of the gear transmission20is outputted from the rotation potentiometer76.

As shown inFIG. 6, the transmission mechanism20B includes a transmission flexibility portion80configured to allow free rotation of the second shaft24as the “rotation support shaft” by a set rotation angle. More particularly, this transmission flexibility portion80is provided at a portion of the fifth shaft49as the “rotation transmission shaft” at which portion the gear coupling mechanism40is coupled. This portion of the fifth shaft49at which portion the gear coupling mechanism40is coupled is a portion of the fifth shaft49on more transmission-wise upstream than the portions of the fifth shaft49at which portions the front wheel output shaft51and the rear wheel differential mechanism53are coupled. The transmission flexibility portion80, as shown inFIG. 6, includes a transmitting rotation portion81provided in the fourth transmission gear45and rotatable with this fourth transmission gear45and a transmitted rotation portion82provided on the fifth shaft49and rotatable together with the fifth shaft49. At a plurality of positions in the lateral portion of the transmitting rotation portion81, transmitting protrusions83are provided, whereas, at a plurality of positions in the lateral portion of the transmitted rotation portion82, transmitted protrusions84are provided. The transmitting protrusions83and the transmitted protrusions84are provided in such a manner that one transmitted protrusion84is engaged between mutually adjacent transmitting protrusions83and also the transmitting protrusions83and the transmitted protrusions84are position-displaceable by a set displacement angle A relative to each other.

With the transmission flexibility portion80in operation, as the transmitting protrusion83and the transmitted protrusion84come into abutment each other via respective end faces thereof, transmission of forward traveling power from the fourth transmission gear45to the fifth transmission shaft49is effected. When the transmitting protrusion83and the transmitted protrusion84come into abutment each other via respective other end faces thereof, transmission of reverse traveling power from the fourth transmission gear45to the fifth shaft49is effected. And, by the relative positional displacement by the set displacement angle A between the transmitting protrusion83and the transmitted protrusion84, free rotation of the second shaft24by the set rotation angle is allowed.

When the first shift gear36is to be engaged with the first speed gear31, even if respective end faces of the first shift gear36and the teeth portion31aof the first speed gear31hit each other, as free rotation of the second shaft24is allowed by the transmission flexibility portion80, the first shift gear36and the first speed gear31can easily be displaced relative to each other in the rotational direction, so that the first shift gear36can come into engagement with the teeth portion31aof the first speed gear31easily. This is also true with the case of the first shift gear36being engaged with the third speed gear33, the case of the second shift gear37being engaged with the second speed gear32and the case of the second shift gear37being engaged with the reverse traveling gear35.

In this embodiment, the transmitting protrusions83and the transmitted protrusions84are provided. However, the transmission flexibility portion may be alternatively configured such that a receded portion is provided in one of the transmitting rotation portion81and the transmitted rotation portion82and a transmitting protrusion which can slidably engage into the receded portion to be slidable by a set rotation angle is provided in the other of the transmitting rotation portion81and the transmitted rotation portion82.

Other Embodiments

(1)FIG. 10is a section view showing a gear transmission90according to a further embodiment. The gear transmission90according to the further embodiment, as shown inFIG. 10, includes a speed changing section90A, as an “input shaft”, for speed-changing power of the first shaft91and a transmission mechanism90B configured to output the power speed-changed by the speed changing section90A to the front wheels1(seeFIG. 1) and to the rear wheels2(seeFIG. 1).

The speed changing section90A, as shown inFIG. 10, includes a first shaft91as an “input shaft”, and a second shaft92and a third shaft93which are disposed in parallel with the first shaft91. The first shaft91mounts a first input gear94, a second input gear95and a third input gear96. A first speed changing gear97for setting forward traveling first speed meshed with the first input gear94is rotatably mounted on the second shaft92. A reverse rotation gear98meshed with the third input gear96is mounted on the third shaft93. A reverse gear99for reverse traveling setting meshed with the reverse rotation gear98is rotatably mounted on the second shaft92. At a portion of the second shaft92between the first speed gear97and the reverse gear99, a shift gear100is slidably mounted.

The transmission mechanism90B includes a first transmission gear101gear-coupled with the second shaft92as a “rotation support shaft”, a rear wheel differential mechanism102having an input shaft102acoupled to the first transmission gear101, a second transmission gear103gear-coupled to the second shaft92, a rotation transmission shaft104coupled to the second transmission gear103, and a front wheel output shaft106coupled to the rotation transmission shaft104via a gear coupling mechanism105. The first transmission gear101is meshed with an output gear107mounted on the second shaft92and gear-coupled to the second shaft92via the output gear107. The second transmission gear103is meshed with the first transmission gear101and gear-coupled to the second shaft92via the first transmission gear101and the output gear107.

With the transmission mechanism90B in operation, power of the second shaft92is inputted via the output gear107to the first transmission gear101and the inputted power is inputted via the first transmission gear101to the rear wheel differential mechanism102and outputted from the rear wheel differential mechanism102to the rear wheels2. The power of the second shaft92is inputted from the output gear107via the first transmission gear101to the second transmission gear103and transmitted from the second transmission gear103via the rotation transmission shaft104and the gear coupling mechanism105to the front wheel output shaft106and from this front wheel output shaft106to the front wheel1.

In the gear transmission90, as the shift gear100is slid to be engaged/disengaged with/from the first speed gear97, the second input gear95and the reverse gear99, whereby speed changing operations in three stages of forward traveling two speed stages and reverse traveling one speed stage are effected, thereby to output forward traveling first speed power or the forward traveling second speed power or the reverse traveling power to the front wheels1and the rear wheels2.

Specifically, when the shift gear100is engaged with a teeth portion97aprovided at a lateral portion of the first speed gear97, the first speed gear97and the second shaft92are operably coupled to each other by the shift gear100. With this, in the gear transmission90, there is provided a forward traveling transmission state of forward first speed, whereby power of the first shaft91is speed-changed by the first input gear94and the first speed changing gear97to forward traveling power of forward first speed and transmitted as such via the shift gear100to the second shaft92and inputted from the output gear107to the transmission mechanism90B and the forward traveling power of forward first speed is inputted from the first transmission gear101to the rear wheel differential mechanism102and outputted from this rear wheel differential mechanism102to the rear wheel2. Further, the forward traveling power of the forward first speed is transmitted from the first transmission gear101to the second transmission gear103and from this second transmission gear103to the front wheel output shaft106, and outputted from the front wheel output shaft106to the front wheel1.

When the shift gear100is engaged with the second input gear95, the second input gear95and the second shaft92are coupled to each other by the shift gear100. With this, in the gear transmission90, there is provided a forward traveling transmission state of forward second speed, whereby power of the first shaft91is speed-changed by the second input gear95and the shift gear100to forward traveling power of forward second speed and transmitted as such via the shift gear100to the second shaft92and inputted from the output gear107to the transmission mechanism90B and the forward traveling power of forward second speed is inputted from the first transmission gear101to the rear wheel differential mechanism102and outputted from this rear wheel differential mechanism102to the rear wheel2. Further, the forward traveling power of the forward second speed is transmitted from the first transmission gear101to the second transmission gear103and from this second transmission gear103to the front wheel output shaft106, and outputted from the front wheel output shaft106to the front wheel1.

When the shift gear100is engaged with a teeth portion99aprovided at a lateral portion of the reverse gear99, the reverse gear99and the second shaft92are operably coupled to each other by the shift gear100. With this, in the gear transmission90, there is provided a reverse traveling transmission state, whereby power of the first shaft91is speed-changed by the third input gear96, the reverse rotation gear98and the reverse gear99to reverse traveling power and transmitted as such to the second shaft92and inputted via the output gear107to the transmission mechanism90B, and the reverse traveling power is inputted via the first transmission gear101to the rear wheel differential mechanism102and outputted from this rear wheel differential mechanism102to the rear wheel2. Further, the revere traveling power is transmitted from the first transmission gear101to the second transmission gear103and transmitted from the second transmission gear103to the front wheel output shaft106and outputted from the front wheel output shaft106to the front wheel1.

Between the first transmission gear101and the input shaft102a, there is provided a transmission flexibility portion80configured to allow free rotation of the second shaft92by a set rotation angle. And, between the rotation transmission shaft104and the second transmission gear103, there is provided a transmission flexibility portion108configured to allow free rotation of the second shaft92by a set rotation angle.

The transmission flexibility portion80provided between the first transmission gear101and the input shaft102ahas an identical arrangement to that of the transmission flexibility portion80shown inFIG. 6. Against a ground-contacting reaction force acting on the rear wheel2, free rotation of the second shaft92is allowed by the transmission flexibility portion80.

The transmission flexibility portion108provided between the rotation transmission shaft104and the second transmission gear103, as shown inFIG. 11, includes a transmitting rotation portion109provided in the second transmission gear103and rotatable in unison with the second transmission gear103and a transmitted rotation portion110provided in the rotation transmission shaft104and rotatable in unison with the rotation transmission shaft104. At a plurality of positions in the lateral portion of the transmitting rotation portion109, receded portions111are provided; whereas, at a plurality of positions in the lateral portion of the transmitted rotation portion110, transmitting protrusions112are provided. The receded portions111and the transmitting protrusions112are provided with one transmitting protrusion112being engaged in one receded portion111. The transmitting protrusions112are engaged in the receded portions111in such a manner to allow positional displacement between the receded portions111and the transmitting protrusions112by a relative set displacement angle Ain the rotation direction of the second transmission gear103.

With the transmission flexibility portion108in operation, when the transmitting rotation portion109and the transmitted rotation portion110are engaged with each other with the transmitting protrusion112being located on one end side of the receded portion111and with one end face of the transmitting protrusion112being placed in contact with the inner wall of the receded portion, transmission of the forward traveling power is effected from the second transmission gear103to the rotation transmission shaft104. And, when the transmitting rotation portion109and the transmitted rotation portion110are engaged with each other, with the transmitting protrusion112being located on the other end side of the receded portion111and the other end face of the transmitting protrusion112being placed in contact with the inner wall of the receded portion111, transmission of the reverse traveling power is effected from the second transmission gear103to the rotation transmission shaft104.

The transmission flexibility portion108allows free rotation of the second shaft92against the ground-contacting reaction force applied to the front wheel1.

(2) In the foregoing embodiment, there was disclosed an example in which the stepless speed changing device10is constituted of a hydrostatic type stepless speed changing device. The invention is not limited thereto, but the stepless speed changing device10may be constituted of various kinds of stepless speed changing device.

(3) In the foregoing embodiment, there was disclosed an example in which the stepless speed changing device10and the gear transmission20are provided in series in such a manner that power from the engine8is inputted to the stepless speed changing device10and output of the stepless speed changing device10is inputted to the gear transmission20. Alternatively, the stepless speed changing device10and the gear transmission20may be provided in series in such a manner that power from the engine8is inputted to the gear transmission20and output of the gear transmission20is inputted to the stepless speed changing device10.

(4) In the foregoing embodiment, there was disclosed an example in which the gear transmission20is configured to be capable of speed changing in reverse traveling one speed and forward traveling two speeds. Alternatively, it may be configured to be capable of speed changing in two or more reverse traveling speeds and three or more reverse traveling speeds.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a gear transmission including a speed changing gear for setting a speed stage, a shift gear slidably mounted on a rotation support shaft and operated to be engaged/disengaged to/from the speed changing gear, a speed changing section configured to speed-change inputted power and to output the resultant power via the rotation support shaft and a transmission mechanism configured to output the power of the rotation support shaft to a traveling device.

DESCRIPTION OF SIGNS