Transmission for industrial vehicle

A transmission for an industrial vehicle has an input shaft; first and second transmission mechanisms each having a plurality of speed-change steps; a second transmission mechanism; a clutch mechanism; a rotation direction switching mechanism; and an output shaft. The clutch mechanism is disposed on the input side of the first and second transmission mechanisms and is provided with a forward clutch and a reverse clutch for switching between forward and reverse travel, and is further provided with first and second snap clutches for selecting which of the first and second transmission mechanisms will receive rotational input from the engine. The rotation direction switching mechanism is a mechanism for switching the direction of rotation inputted to the first transmission mechanism or the second transmission mechanism to the direction of rotation for forward travel or the direction of rotation for reverse travel in accordance with the switching of forward and reverse travel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2007-071970, filed on Mar. 20, 2007. The entire disclosures of Japanese Patent Application No. 2007-071970 are hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a transmission for an industrial vehicle, particularly to a transmission for an industrial vehicle for changing and outputting the speed of rotation from the engine while capable of multiple speed changes during forward and reverse travel.

BACKGROUND ART

A hydraulic transmission such as that disclosed in Japanese Laid-Open Patent Application No. 2005-282830 is commonly provided as a transmission for a wheel loader or another industrial vehicle. This type of transmission has a torque converter disposed between the engine and the transmission body. Disposed inside the transmission body are a hydraulic clutch for forward travel and a hydraulic clutch for reverse travel whereby a switch is made between forward and reverse travel, as well as hydraulic clutches for a plurality of speed-change steps that can operate in forward and reverse.

With such a transmission, the hydraulic clutch for forward travel is engaged (brought into a power transmission state) and the hydraulic clutch for reverse travel is disengaged (brought into a power cutoff state) during forward travel, after which the hydraulic clutch of the corresponding speed-change step is engaged so that a suitable speed-change step is selected in accordance with the travel state or the like. Conversely, the hydraulic clutch for forward travel is disengaged and the hydraulic clutch for reverse travel is engaged during reverse travel, after which the hydraulic clutch of the corresponding speed-change step is engaged so that a suitable speed-change step is selected in accordance with the travel state or the like.

In a passenger vehicle, on the other hand, a twin-clutch transmission for a vehicle is provided for rapidly switching speeds (e.g., Japanese Laid-Open Patent Application No. 2001-99246). The transmission shown in Japanese Laid-Open Patent Application No. 2001-99246 has a first transmission mechanism for odd-numbered speeds, a second transmission mechanism for even-numbered speeds, and first and second clutch mechanisms provided in correspondence to the respective transmission mechanisms.

In such a configuration, it is possible to rapidly change speed from an odd-numbered speed-change step to an even-numbered speed-change step because the speed change can be prepared (pre-shifted) in the second transmission mechanism for even-numbered speeds when the vehicle is travelling in an odd-numbered speed, for example.

SUMMARY OF THE INVENTION

A conventional transmission for an industrial vehicle generally uses a torque converter and a plurality of hydraulic clutches, as shown in Japanese Laid-Open Patent Application No. 2005-282830. The torque converter has poor power transmission because power is transmitted using a fluid. Also, a conventional transmission has a hydraulic clutch provided to each speed-change step, so the configuration is complex, and the configuration of the oil lines for providing hydraulic pressure to the hydraulic clutch is complicated.

Therefore, it is possible to consider using a configuration such as that shown in Japanese Laid-Open Patent Application No. 2001-99246, which is used as a transmission for a passenger vehicle, in a transmission for a wheel loader or another industrial vehicle.

However, in a transmission for an industrial vehicle, the reverse-movement side is similar to the forward-movement side in that a plurality of speed-change steps is required in the same manner as during forward travel, and a configuration such as that shown in Japanese Laid-Open Patent Application No. 2001-99246 cannot be used without modification.

An object of the present invention is to provide a transmission for an industrial vehicle that has a simple configuration and good efficiency.

The transmission for an industrial vehicle according to a first aspect is a transmission adapted to output rotation from an engine while enabling multiple speed changes during forward and reverse travel. The transmission includes an input shaft, a first transmission mechanism, a second transmission mechanism, a clutch mechanism, a rotation direction switching mechanism, and an output shaft. The input shaft receives rotation from the engine as input. The first transmission mechanism configured and arranged to change the speed of rotation from the input shaft among a plurality of speed steps. The second transmission mechanism, provided in parallel to the first transmission mechanism, is configured and arranged to change the speed of rotation from the input shaft among a plurality of speed steps. The clutch mechanism is disposed on the input side of the first and second transmission mechanisms and is provided with a forward clutch and a reverse clutch for switching between forward and reverse travel states; a first snap clutch for inputting the rotation from the engine to the first transmission mechanism; and a second snap clutch for inputting the rotation from the engine to the second transmission mechanism. The rotation direction switching mechanism is configured and arranged to switch a direction of rotation inputted to the first transmission mechanism or the second transmission mechanism to one of a direction of rotation for forward travel and a direction of rotation for reverse travel in accordance with the switch between the forward and reverse travel states by using the forward clutch and the reverse clutch. The output shaft is configured and arranged to output the rotation inputted from the first and second transmission mechanisms.

With this transmission, rotation from the engine is inputted to an input shaft. The forward clutch is engaged (brought into a power transmission state) during forward travel and the reverse clutch is disengaged (brought into a power cutoff state) during forward travel. The rotation from the input shaft is inputted to the first transmission mechanism or the second transmission mechanism selected by the first snap clutch and the second snap clutch. Conversely, the forward clutch is disengaged during reverse travel, the reverse clutch is engaged during reverse travel, and the rotation from the input shaft is inputted to the first transmission mechanism or the second transmission mechanism. In a case in which the speed is changed by input to the first transmission mechanism during forward or reverse travel, the first snap clutch is engaged and the second snap clutch is disengaged. Conversely, when the speed is changed by input to the second transmission mechanism, the first snap clutch is disengaged and the second snap clutch is engaged.

In this arrangement, the rotation direction switching mechanism sets the direction of rotation inputted to the transmission mechanisms to be the direction of rotation for forward travel during forward travel, and the direction of rotation inputted to the transmission mechanisms to be the direction of rotation for reverse travel during reverse travel.

In this arrangement, a plurality of speed-change steps can be obtained during both forward travel and reverse travel using a single set of transmission mechanisms by providing the pre-stage of the transmission mechanism with a clutch mechanism having a forward clutch and a reverse clutch as well as a first snap clutch and a second snap clutch. Each speed-change step of forward and reverse travel can be rapidly changed.

With the transmission mechanism having a configuration such as that described above, the configuration of the transmission mechanisms can be simplified in comparison with a conventional transmission because the transmission mechanisms can be generally configured using a dog clutch.

The transmission for an industrial vehicle according to a second aspect is the transmission for an industrial vehicle as recited in the first aspect, wherein one of the forward clutch and the reverse clutch, and one of the first snap clutch and the second snap clutch, are coaxially arranged as a first clutch pair. Also, the other of the forward clutch and the reverse clutch, and the other of the first snap clutch and the second snap clutch, are coaxially arranged as a second clutch pair.

Here, as an example, the forward clutch and the first snap clutch are coaxially arranged as a first clutch pair, and the reverse clutch and the second snap clutch are coaxially arranged as a second clutch pair.

In this case, a portion of the constituent members of the two clutches contained in each clutch pair can be shared and the configuration can be simplified. For example, when the clutches are hydraulic clutches, a portion of the clutch casing for accommodating the clutch plate can be shared. It is possible to avoid situations in which the occupied space in the horizontal and vertical directions orthogonal to the axial direction increases in size.

The transmission for an industrial vehicle according to a third aspect is the transmission for an industrial vehicle as recited in the second aspect, wherein the first and second transmission mechanisms have first and second speed-change shafts, respectively, arranged parallel to the input shaft; one of the first and second clutch pairs is arranged coaxially with the input shaft; and the other of the first and second clutch pairs is arranged coaxially with one of the first speed-change shaft and the second speed-change shaft.

Here, as an example, the first clutch pair is arranged coaxially with the input shaft, and the second clutch pair is arranged coaxially with the second speed-change shaft.

In this case, space in the horizontal and vertical directions can be made the same as that of a transmission for an industrial vehicle such as that described in Japanese Laid-Open Patent Application No. 2005-282830. In other words, in a conventional transmission, the input shaft, the first speed-change shaft, and the second speed-change shaft are provided, and a hydraulic clutch is arranged for each shaft. In the present invention, space in the horizontal and vertical directions is not increased even if the clutch mechanisms were to be provided with a hydraulic clutch configuration in the same manner as in the prior art because a clutch mechanism is merely provided to the input shaft and the first or second speed-change shaft.

The transmission for an industrial vehicle according to a fourth aspect is the transmission for an industrial vehicle as recited in the third aspect, wherein the rotation direction switching mechanism has a first gear train, a second gear train and a third gear train. The first gear train is configured and arranged to input rotation to the first clutch pair and the second clutch pair in the same direction. The second gear train is configured and arranged to transmit output between the first clutch pair and the second clutch pair so that the first clutch pair and the second clutch pair rotate in opposite directions. The third gear train is configured and arranged to transmit the output of the one of the first and second clutch pairs that is arranged coaxially with the input shaft to the other of the first and second speed-change shafts that is not coaxial with the other of the first and second clutch pairs so that the other of the first and second speed-change shafts rotates in an opposite direction from the one of the first and second clutch pairs.

In this arrangement, the rotation from the engine is inputted to the first clutch pair and the second clutch pair, and the direction of rotation inputted to the clutch pairs is set in the same direction as the first gear train. However, the mutual output rotations of the clutch pairs are given the opposite direction by the second gear train and transmitted to the counterpart side. The output rotation of the clutch pair disposed coaxially with the input shaft is furthermore made to rotate in the opposite direction by the third gear train and inputted to the speed-change shaft that is not coaxial with the two clutch pairs.

Here, as an example, the first clutch pair composed of the forward clutch and the first snap clutch is arranged coaxially with the input shaft, and the second clutch pair composed of the reverse clutch and the second snap clutch is arranged coaxially with the speed-change shaft of the second transmission mechanism. In this example, when the forward clutch is engaged and the reverse clutch is disengaged during forward travel, the engine rotation is inputted to the first and second transmission mechanisms via the following pathways.

Input to the First Transmission Mechanism During Forward Travel: First Snap Clutch Engaged

Input to the Second Transmission Mechanism During Forward Travel: Second Snap Clutch Engaged

In this manner, the rotation in the second direction (forward direction) is transmitted to the first transmission mechanism and the second transmission mechanism.

On the other hand, the forward clutch is engaged and the reverse clutch is disengaged during reverse travel, and the engine rotation is inputted to the first and second transmission mechanisms via the following pathways.

Input to the First Transmission Mechanism During Reverse Travel: First Snap Clutch Engaged

Input to the Second Transmission Mechanism During Reverse Travel: Second Snap Clutch Engaged

In this manner, the rotation in the first direction (reverse direction) is transmitted to the first transmission mechanism and the second transmission mechanism.

The transmission for an industrial vehicle according to a fifth aspect is the transmission for an industrial vehicle as recited in any of the first to fourth aspects, further comprising a main clutch device, disposed between the engine and the clutch mechanism, configured and arranged to transmit the rotation from the engine to the input shaft.

In this case, the engine power can be transmitted with good efficiency because the rotation from the engine is transmitted to the transmission mechanisms by a main clutch device rather than a torque converter. The main clutch device can control the clutch capacity by controlling the hydraulic pressure of the clutch in the case of a hydraulic clutch, for example. Therefore, engine stoppage under a rapid increase in load or at other times can be avoided by reducing the clutch capacity of the main clutch device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Overall Structure

FIG. 1is a layout cross-sectional development view of the transmission according to an embodiment of the present invention.FIG. 2is a schematic layout view of the shafts and the like as viewed from the rear of the transmission.FIG. 3is a skeleton view of the present transmission.FIG. 4is a schematic partial view of the transmission mechanism.

The transmission shown inFIG. 1is installed, e.g., in a wheel loader, and is provided with ten speed-change steps for both forward and reverse travel. The transmission has a main clutch1to which rotation from the engine is inputted, an input shaft2to which the engine rotation is inputted via the main clutch1, a first transmission mechanism3, a second transmission mechanism4, a clutch mechanism5, a rotation direction switching mechanism6, and an output shaft7. A speed-changing idle shaft8and an output idle shaft9are disposed between the output shaft7and the first and second transmission mechanisms3,4.

Main Clutch

The main clutch1is a hydraulic clutch that can control the clutch capacity by controlling the hydraulic pressure of the clutch. The main clutch1has an input-side member1alinked to an engine-side member, and an output-side member1blinked to the input shaft2. A power takeoff mechanism (not shown) for driving auxiliary equipment is linked to the input-side member1aof the main clutch1.

Input Shaft

The input shaft2is rotatably supported by a pair of bearings in a housing10. The output-side member1bof the main clutch1is linked by a spline to the distal end of the input shaft2, and the input-side member1aof the main clutch1is rotatably supported via a bearing.

First Transmission Mechanism

The first transmission mechanism3receives rotation as input when an odd-numbered step (1st and 3rd speeds, 5th speed, and 7th and 9th speeds) is selected from among ten speed-change steps; has a first speed-change shaft12, first- and third-speed (hereinafter referred to as 1st- and 3rd-speed) drive gears13, a fifth-speed (hereinafter referred to as 5th-speed) drive gear14, seventh and ninth speed (hereinafter referred to as 7th- and 9th-speed) drive gears15, and a reduction gear16; and further has first to third dog clutches C1, C2, C3.

The first speed-change shaft12is offset from the input shaft2, is disposed in parallel to the input shaft2, and is rotatably supported by a pair of bearings in the housing10. The 1st- and 3rd-speed drive gears13, the 5th-speed drive gear14, and the 7th- and 9th-speed drive gears15are each rotatably supported by a pair of bearings on the first speed-change shaft12. The reduction gear16is nonrotatably mounted on the engine-side distal end of the first speed-change shaft12.

The dog clutches C1to C3are clutches that move in the axial direction and are designed either to relatively nonrotatably fix the drive gears13to15to the first speed-change shaft12or to link two drive gears to each other.

Specifically, the first dog clutch C1is a clutch for switching between engaging (linking) the first speed-change shaft12and the 1st- and 3rd-speed drive gears13with each other, engaging the 1st- and 3rd-speed drive gears13with the 5th-speed drive gear14, and disengaging (not linking) these elements from each other. The second dog clutch C2is a clutch for switching between engaging the first speed-change shaft12and the 5th-speed drive gear14with each other, engaging the 5th-speed drive gear14with the 7th- and 9th-speed drive gears15, and disengaging these elements from each other. The third dog clutch C3is a clutch for switching between engaging and disengaging the first speed-change shaft12and the 7th- and 9th-speed drive gears15. The third dog clutch C3is constantly kept in a state of being incapable of rotating relative to the first speed-change shaft12, and the first and second dog clutches C1, C2can assume a position in which the clutches are incapable of rotating relative to the first speed-change shaft12, or a position in which the clutches are capable of rotating relative to the shaft.

Second Transmission Mechanism

The second transmission mechanism4receives rotation as input when an even-numbered step (second and fourth speeds, sixth speed, and eighth and tenth speeds) is selected from among ten speed-change steps; has a second speed-change shaft20, second- and fourth-speed (hereinafter referred to as 2nd-and 4th-speed) drive gears21, a sixth-speed (hereinafter referred to as 6th-speed) drive gear22, and eighth and tenth speed (hereinafter referred to as 8th- and 10th-speed) drive gears23; and also has fourth to sixth dog clutches C4, C5, C6.

The second speed-change shaft20is offset from the input shaft2, is disposed in parallel to the input shaft2and the first speed-change shaft12, and is rotatably supported by a pair of bearings in the housing10. The 2nd- and 4th-speed drive gears21, the 6th-speed drive gear22, and the 8th- and 10th-speed drive gears23are each rotatably supported by a pair of bearings on the second speed-change shaft20.

The fourth to sixth dog clutches C4, C5, C6are clutches that move in the axial direction and are designed either to fix (make incapable of relative rotation) the drive gears21through23to the second speed-change shaft20, or to link two drive gears to each other. The sixth dog clutch C6is constantly kept in a state of being incapable of rotating relative to the second speed-change shaft20, and the fourth and fifth dog clutches C4, C5can assume a position in which the clutches are incapable of rotating relative to the second speed-change shaft20, or a position in which the clutches are capable of rotating relative to the shaft.

Specifically, the fourth dog clutch C4is a clutch for switching between engaging the second speed-change shaft20with the 2nd- and 4th-speed drive gears21, engaging the 2nd- and 4th-speed drive gears21with the 6th-speed drive gear22, and disengaging these elements from each other. The fifth dog clutch C5is a clutch for switching between engaging the second speed-change shaft20and the 6th-speed drive gear22, engaging the 6th-speed drive gear22with the 8th- and 10th-speed drive gears23, and disengaging these elements from each other. The sixth dog clutch C6is a clutch for switching between engaging and disengaging the second speed-change shaft20and the 8th- and 10th-speed drive gears23.

A synchronizing mechanism24for ensuring a smooth meshing of the clutch during speed change is provided to the second speed-change shaft20. The synchronizing mechanism24has a first synchronizing gear24aand a second synchronizing gear24bthat are rotatably supported on the second speed-change shaft20, and a cone clutch24cfor linking the synchronizing gears24a,24band the second speed-change shaft20as shown inFIG. 3.

The speed-changing idle shaft8is rotatably supported by a pair of bearings in the housing10in the same manner as the speed-change shafts12,20. The speed-changing idle shaft8is disposed parallel to the shafts12,20below the first and second speed-change shafts12,20and on the same perpendicular line as the input shaft2, as shown inFIG. 2. The speed-changing idle shaft8is provided with the seventh and eighth drive clutches C7, C8, as well as a driven gear that meshes with the drive gears provided to the first and second transmission mechanisms3,4. More specifically, first to fifth driven gears26,27,28,29,30are rotatably supported in sequence from the engine by the speed-changing idle shaft8via bearings. The first driven gear26and the second driven gear27are configured so as to integrally rotate with each other, and the fourth driven gear29and the fifth driven gear30are configured so as to integrally rotate with each other. The driven gear26constantly meshes with the 7th- and 9th-speed drive gears15, the second driven gear27with the 2nd- and 4th-speed drive gears21, the third driven gear28with the 5th-speed drive gear14and the 6th-speed drive gear22, the fourth driven gear29with the 1st- and 3rd-speed drive gears13, and the fifth driven gear30with the 8th- and 10th-speed drive gears23, respectively.

The seventh and eighth dog clutches C7, C8are clutches that move in the axial direction and are desired to relatively nonrotatably fix the driven gears to the speed-changing idle shaft8. The seventh and eighth dog clutches C7, C8are constantly kept in a state of being incapable of rotating relative to the speed-changing idle shaft8.

Specifically, the seventh dog clutch C7is a clutch for engaging or disengaging the speed-changing idle shaft8with or from the first and second driven gears26,27; and the eighth dog clutch C8is a clutch for engaging or disengaging the speed-changing idle shaft8with or from the fourth and fifth driven gears29,30.

A parking brake32provided to the rear end (the end on the side opposite from the engine) of the speed-changing idle shaft8.

Output Idle Shaft

The output idle shaft9is rotatably supported by a pair of bearings in the housing10in the same manner as other shafts. As shown inFIG. 2, the output idle shaft9is disposed parallel to the speed-changing idle shaft8below the speed-changing idle shaft8, and is offset to the left side (toward the second speed-change shaft20) as viewed from the rear. First and second output idle gears35,36are fixed to the output idle shaft9. The first output idle gear35meshes with the third driven gear28of the speed-changing idle shaft8.

Output Shaft

The output shaft7is rotatably supported by a pair of bearings in the housing10in the same manner as other shafts, and output flanges40,41linked to an axle-side member are mounted on the two ends of the output shaft. The output shaft7is disposed parallel to the shafts, below the output idle shaft9, and on the same perpendicular line as the input shaft2and the second speed-change shaft20, as shown inFIG. 2. An output gear42is fixed to the output shaft7, and the output gear42meshes with the second output idle gear36of the output idle shaft9.

Clutch Mechanism

The clutch mechanism5has a first clutch pair5F disposed coaxially with the input shaft2, and a second clutch pair5R disposed coaxially with the second transmission mechanism4and the second speed-change shaft20.

First Clutch Pair: Forward Clutch & First Snap Clutch

The first clutch pair5F has a forward clutch F that is engaged (power transmission state) during forward travel, and a first snap clutch SC1for transmitting rotation to the first transmission mechanism3, as shown inFIG. 3. The forward clutch F and the first snap clutch SC1are both hydraulic multidisc clutches and are disposed coaxially with each other.

More specifically, the forward clutch F has a forward input gear FG nonrotatably fixed to the input shaft2, a clutch case45provided so as to be able to rotate about the input shaft2, and a plurality of clutch plates disposed between the forward input gear FG and the clutch case45. The first snap clutch SC1has a clutch case shared with the clutch case45of the forward clutch F, an intermediate gear46rotatably supported on the input shaft2, and a plurality of clutch plates disposed between the clutch case45and the intermediate gear46. The intermediate gear46has a first intermediate gear46adisposed on the input side, and a second intermediate gear46bdisposed on the output side. The first intermediate gear46ameshes with the first synchronizing gear24aof the synchronizing mechanism24, and the second intermediate gear46bmeshes with the second synchronizing gear24bof the synchronizing mechanism24. The first intermediate gear46aand the second intermediate gear46bare integrally formed. A clutch case gear47is formed on the end part of the output side (right side inFIG. 1) on the external periphery of the clutch case45.

With such a configuration, power can be transmitted between the forward input gear FG (i.e., the input shaft2) and the clutch case45by engaging the forward clutch F. Power can be transmitted between the clutch case45and the intermediate gear46by engaging the first snap clutch SC1.

Second Clutch Pair: Reverse Clutch & Second Snap Clutch

The second clutch pair5R has a reverse clutch R that is engaged during reverse travel (power transmission state), and a second snap clutch SC2for transmitting rotation to the second transmission mechanism4, as shown inFIG. 3. The reverse clutch R and the second snap clutch SC2are both hydraulic multidisc clutches and are disposed coaxially with each other.

More specifically, the reverse clutch R has a clutch shaft48disposed coaxially with the second speed-change shaft20, a reverse input gear RG rotatably supported on the clutch shaft48, a clutch case49provided so as to be able to rotate about the clutch shaft48, and a plurality of clutch plates disposed between the reverse input gear RG and the clutch case49. A spline hole is formed in the end part of the output side (right side ofFIG. 1) of the clutch shaft48, and a splined shaft formed at the distal end of the second speed-change shaft20is coupled to the spline hole. The reverse input gear RG is linked to the forward input gear FG via an idling gear IG (seeFIGS. 2 and 3) rotatably supported in the housing10. The second snap clutch SC2has a clutch case shared with the clutch case49of the reverse clutch R, and a plurality of clutch plates disposed between the clutch case49and the clutch shaft48. A clutch case gear50is formed on the end part of the output side (right side inFIG. 1) on the external periphery of the clutch case45, and the clutch case gear50meshes with the clutch case gear47of the first snap clutch SC1.

In such a configuration, the reverse clutch R is engaged, whereby power can be transmitted between the reverse input gear RG (i.e., the input shaft2) and the clutch case49. The second snap clutch SC2is engaged, whereby power can be transmitted between the clutch case49and the clutch shaft48(i.e., the second speed-change shaft20).

Rotation Directions Switching Mechanism

The rotation direction switching mechanism6is a mechanism whereby the direction of rotation inputted to the first transmission mechanism3or second transmission mechanism4is set, by using the clutch mechanism5, to the direction of rotation for forward travel and the direction of rotation for reverse travel in accordance with the switch between the forward and reverse travel. The rotation direction switching mechanism6has a first gear train52for inputting rotation of the same direction to the first clutch pair5F and the second clutch pair5R, a second gear train53for reversing the direction of rotational output of both the first clutch pair5F and the second clutch pair5R and transmitting the reversed rotational output to the counterpart side, and a third gear train54for reversing the direction of rotational output of the first clutch pair5F and inputting the reversed rotational output to the first transmission mechanism3, as shown inFIG. 3.

Specifically, the first gear train52is a gear train composed of the forward input gear FG, the idling gear IG, and the reverse input gear RG; the second gear train53is a gear train composed of the clutch case gear47of the first snap clutch SC1and the clutch case gear50of the second snap clutch SC2; and the third gear train54is a gear train composed of the intermediate gear46, and the reduction gear16provided to the first transmission mechanism3.

Power Transmission Pathway: Input-Side Shared Pathway

Next, the power transmission pathway of the transmission configured as described above will be described. First described is the shared pathway for each speed-change step, i.e., the power transmission pathway from the input shaft2to the transmission mechanisms3,4.

Forward Clutch Engaged & First Snap Clutch Engaged

In a case in which the forward clutch F and the first snap clutch SC1are engaged (the reverse clutch R and second snap clutch SC2are disengaged), rotation from the input shaft2is transmitted to the intermediate gear46via the forward clutch F and the first snap clutch SC1, and is inputted to the first speed-change shaft12of the first transmission mechanism3via the reduction gear16, which meshes with the intermediate gear46.

The corresponding direction of rotation is the first direction for the input shaft2and the intermediate gear46when the direction of engine rotation is set as the first direction (the same applies for all directions hereinafter), and the direction of rotation of the first speed-change shaft12is the second direction (forward).

Forward Clutch Engaged & Second Snap Clutch Engaged

In a case in which the forward clutch F and the second snap clutch SC2are engaged (the reverse clutch R and first snap clutch SC1are disengaged), rotation from the input shaft2is transmitted to the clutch shaft48via the forward clutch F and the second snap clutch SC2, and is inputted to the second speed-change shaft20of the second transmission mechanism4, which is spline linked with the clutch shaft48.

Since the corresponding direction of rotation is the first direction for the input shaft2and the clutch case gear47of the first snap clutch SC1, the clutch shaft48and the clutch case gear50of the second snap clutch SC2rotate in the second direction, and the direction of rotation of the second speed-change shaft20is the second direction (forward).

Reverse Clutch Engaged & First Snap Clutch Engaged

In a case in which the reverse clutch R and the first snap clutch SC1are engaged (the forward clutch F and second snap clutch SC2are disengaged), rotation from the input shaft2is transmitted to the reverse clutch R via the forward input gear FG, the idling gear IG, and the reverse input gear RG; and the rotation of the reverse clutch R is inputted to the first snap clutch SC1via the meshing of the two clutch case gears47,50. The rotation is transmitted to the intermediate gear46and is further inputted to the first speed-change shaft12of the first transmission mechanism3via the reduction gear16, which meshes with the intermediate gear46.

Since the corresponding direction of rotation is the first direction for the input shaft2, the clutch shaft48and the reverse clutch R (second snap clutch SC2) also rotate in the first direction. Therefore, the direction of rotation of the first snap clutch SC1is the second direction. Accordingly, the direction of rotation of the first speed-change shaft12is the first direction (reverse).

Reverse Clutch Engaged & Second Snap Clutch Engaged

In a case in which the reverse clutch R and the second snap clutch SC2are engaged (the forward clutch F and first snap clutch SC1are disengaged), rotation from the input shaft2is inputted to the reverse clutch R via the forward input gear FG, the idling gear IG, and the reverse input gear RG. The rotation of the reverse clutch R is inputted to the clutch shaft48and the second speed-change shaft20of the input shaft2via the second snap clutch SC2.

Since the corresponding direction of rotation is the first direction for the input shaft2, the clutch shaft48and the reverse clutch R (second snap clutch SC2) also rotate in the first direction. Therefore, the direction of rotation of the clutch shaft48and the second speed-change shaft20is the first direction (reverse).

Power Transmission Pathway: Each Speed-Changes Step

The speed of the rotation inputted to the first and second transmission mechanisms3,4is thus changed in the manner described below for each speed-change step.

Forward First Speed

In the case of the forward first speed, the forward clutch F and the first snap clutch SC1are engaged and the reverse clutch R and the second snap clutch SC2are disengaged. In this case, the rotation in the second direction is inputted to the first speed-change shaft12as described above. In forward first speed, the dog clutches are controlled so that the following members are engaged (linked) with each other, as shown inFIG. 5.

First dog clutch C1: first speed-change shaft12+1st- and 3rd-speed drive gears13

Other dog clutches: disengaged

In this arrangement, the rotation inputted to the first speed-change shaft12is transmitted to the speed-changing idle shaft8via the pathway described below. The power transmission pathway is shown by a solid line inFIG. 5. The rotation transmission pathway of the second transmission mechanism4in this case is indicated by a dotted line. The pathway indicated by the dotted line is the rotation transmission pathway of second speed and indicates that pre-shifting has been performed.

Forward Second Speed

In the case of the forward second speed, the forward clutch F and the second snap clutch SC2are engaged and the reverse clutch R and the first snap clutch SC1are disengaged. In this case, the rotation in the second direction is inputted to the second speed-change shaft20as described above. In forward second speed, the dog clutches are controlled so that the following members are engaged (linked) with each other, as shown inFIG. 6.

First dog clutch C1: first speed-change shaft12+1st- and 3rd-speed drive gears13

Other dog clutches: disengaged

In this arrangement, the rotation inputted to the second speed-change shaft20is transmitted to the speed-changing idle shaft8via the following pathway. The power transmission pathway is shown by a solid line inFIG. 6. The rotation transmission pathway of the first transmission mechanism3in this case is indicated by a dotted line. The pathway indicated by the dotted line is the rotation transmission pathway of third speed and indicates that pre-shifting has been performed.

Forward Third Speed

In the case of the forward third speed, the forward clutch F and the first snap clutch SC1are engaged and the reverse clutch R and the second snap clutch SC2are disengaged. In this case, the rotation in the second direction is inputted to the first speed-change shaft12as described above. In forward third speed, the dog clutches are controlled so that the following members are engaged (linked) with each other, as shown inFIG. 7.

First dog clutch C1: first speed-change shaft12+1st- and 3rd-speed drive gears13

Seventh dog clutch C7: second driven gear27+speed-changing idle shaft8

Other dog clutches: disengaged

In this arrangement, the rotation inputted to the first speed-change shaft12is transmitted to the speed-changing idle shaft8via the following pathway. The power transmission pathway is shown by a solid line inFIG. 7. The rotation transmission pathway of the second transmission mechanism4in this case is indicated by a dotted line. The pathway indicated by the dotted line is the rotation transmission pathway of fourth speed and indicates that pre-shifting has been performed.

Forward Fourth Speed

In the case of the forward fourth speed, the forward clutch F and the second snap clutch SC2are engaged and the reverse clutch R and the first snap clutch SC1are disengaged. In this case, the rotation in the second direction is inputted to the second speed-change shaft20as described above. In forward fourth speed, the dog clutches are controlled so that the following members are engaged (linked) with each other, as shown inFIG. 8.

Seventh dog clutch C7: second driven gear27+speed-changing idle shaft8

Other dog clutches: disengaged

In this arrangement, the rotation inputted to the second speed-change shaft20is transmitted to the speed-changing idle shaft8via the following pathway. The power transmission pathway is shown by a solid line inFIG. 8. The rotation transmission pathway of the first transmission mechanism3in this case is indicated by a dotted line. The pathway indicated by the dotted line is the rotation transmission pathway of fifth speed and indicates that pre-shifting has been performed.

Forward Fifth Speed

In the case of the forward fifth speed, the forward clutch F and the first snap clutch SC1are engaged and the reverse clutch R and the second snap clutch SC2are disengaged. In this case, the rotation in the second direction is inputted to the first speed-change shaft12as described above. In forward fifth speed, the dog clutches are controlled so that the following members are engaged (linked) with each other, as shown inFIG. 9.

Other dog clutches: disengaged

In this arrangement, the rotation inputted to the first speed-change shaft12is transmitted to the speed-changing idle shaft8via the following pathway. The power transmission pathway is shown by a solid line inFIG. 9. The rotation transmission pathway of the second transmission mechanism4in this case is indicated by a dotted line. The pathway indicated by the dotted line is the rotation transmission pathway of sixth speed and indicates that pre-shifting has been performed.

Forward Sixth Speed

In the case of the forward sixth speed, the forward clutch F and the second snap clutch SC2are engaged and the reverse clutch R and the first snap clutch SC1are disengaged. In this case, the rotation in the second direction is inputted to the second speed-change shaft20as described above. In forward sixth speed, the dog clutches are controlled so that the following members are engaged (linked) with each other, as shown inFIG. 10.

Seventh dog clutch C7: first and second driven gears26,27+speed-changing idle shaft8

Other dog clutches: disengaged

In this arrangement, the rotation inputted to the second speed-change shaft20is transmitted to the speed-changing idle shaft8via the following pathway. The power transmission pathway is shown by a solid line inFIG. 10. The rotation transmission pathway of the first transmission mechanism3in this case is indicated by a dotted line. The pathway indicated by the dotted line is the rotation transmission pathway of seventh speed and indicates that pre-shifting has been performed.

Forward Seventh Speed

In the case of the forward seventh speed, the forward clutch F and the first snap clutch SC1are engaged and the reverse clutch R and the second snap clutch SC2are disengaged. In this case, the rotation in the second direction is inputted to the first speed-change shaft12as described above. In forward seventh speed, the dog clutches are controlled so that the following members are engaged (linked) with each other, as shown inFIG. 11.

Seventh dog clutch C7: first and second driven gears26,27+speed-changing idle shaft8

Other dog clutches: disengaged

In this arrangement, the rotation inputted to the first speed-change shaft12is transmitted to the speed-changing idle shaft8via the following pathway. The power transmission pathway is shown by a solid line inFIG. 11. The rotation transmission pathway of the second transmission mechanism4in this case is indicated by a dotted line. The pathway indicated by the dotted line is the rotation transmission pathway of eighth speed and indicates that pre-shifting has been performed.

First speed-change shaft12→third dog clutch C3→7th- and 9th-speed drive gears15→first and second driven gears26,27→seventh dog clutch C7→speed-changing idle shaft8.

Forward Eight Speed

In the case of the forward eighth speed, the forward clutch F and the second snap clutch SC2are engaged and the reverse clutch R and the first snap clutch SC1are disengaged. In this case, the rotation in the second direction is inputted to the second speed-change shaft20as described above. In forward eighth speed, the dog clutches are controlled so that the following members are engaged (linked) with each other, as shown inFIG. 12.

Eighth dog clutch C8: fourth and fifth driven gears29,30+speed-changing idle shaft8

Other dog clutches: disengaged

In this arrangement, the rotation inputted to the second speed-change shaft20is transmitted to the speed-changing idle shaft8via the following pathway. The power transmission pathway is shown by a solid line inFIG. 12. The rotation transmission pathway of the first transmission mechanism3in this case is indicated by a dotted line. The pathway indicated by the dotted line is the rotation transmission pathway of ninth speed and indicates that pre-shifting has been performed.

Forward Ninth Speed

In the case of the forward ninth speed, the forward clutch F and the first snap clutch SC1are engaged and the reverse clutch R and the second snap clutch SC2are disengaged. In this case, the rotation in the second direction is inputted to the first speed-change shaft12as described above. In forward ninth speed, the dog clutches are controlled so that the following members are engaged (linked) with each other, as shown inFIG. 13.

First dog clutch C1: 1st- and 3rd-speed drive gears13+5th-speed drive gear14

Other dog clutches: disengaged

In this arrangement, the rotation inputted to the first speed-change shaft12is transmitted to the speed-changing idle shaft8via the following pathway. The power transmission pathway is shown by a solid line inFIG. 13. The rotation transmission pathway of the second transmission mechanism4in this case is indicated by a dotted line. The pathway indicated by the dotted line is the rotation transmission pathway of tenth speed and indicates that pre-shifting has been performed.

Forward Tenth Gear

In the case of the forward tenth speed, the forward clutch F and the second snap clutch SC2are engaged and the reverse clutch R and the first snap clutch SC1are disengaged. In this case, the rotation in the second direction is inputted to the second speed-change shaft20as described above. In forward tenth speed, the dog clutches are engaged and disengaged in the same manner as forward ninth gear.

In this arrangement, the rotation inputted to the second speed-change shaft20is transmitted to the speed-changing idle shaft8via the following pathway. The rotation transmission pathway of the first transmission mechanism3in this case is the same as that of forward ninth gear.

In the case of reverse travel, the situation is different in that the forward clutch F is disengaged and the reverse clutch R is engaged. Therefore, in the case of reverse travel, rotation in the opposite direction of that of forward travel is inputted to the first speed-change shaft12and the second speed-change shaft20, but control of the dog clutches and the power transmission pathway at each speed step is exactly the same as that that of each speed-change step for forward travel.

Power Transmission Pathway: Output-Side Shared Pathway

The rotation outputted to the speed-changing idle shaft8in each speed-change step in the manner described above is transmitted to the output gear42via the first output idle gear35, the output idle shaft9, and the second output idle gear36, and is further outputted to the axle via the output shaft7and the output flanges40,41. The first output idle gear35meshes with the third driven gear28of the speed-changing idle shaft8.

Concerning Synchronization During Speed Change

In the present embodiment, rotation is inputted to the first transmission mechanism3in odd-numbered speed-change steps, and rotation is inputted to the second transmission mechanism4in even-numbered speed-change steps, as described above. Pre-shifting is carried out in the transmission mechanism for moving to the next speed-change step when the speed is changed one speed at a time, and the dog clutches are smoothly meshed using the synchronizing mechanism24when a speed change is made to the next speed-change step.

The pre-shift operation will be described below with reference toFIG. 6using, e.g., the case in which the speed is changed from sixth speed to fifth speed and then to fourth speed.

In sixth speed, power is transmitted along a pathway such as that shown by the solid line ofFIG. 14(same asFIG. 9). In the sixth speed, the rotation transmission pathway (the pathway indicated by the dotted line inFIG. 14) of fifth speed is prepared by the first transmission mechanism3. In other words, a pre-shift is performed. Therefore, a speed change can be executed by merely disengaging the second snap clutch SC2and engaging the first snap clutch SC1when a change is made from sixth speed to fifth speed. The rotation transmission pathway in fifth speed is shown by a solid line inFIG. 15.

Next, the synchronizing mechanism24must perform synchronization when the speed is changed from fifth speed to fourth speed. In this situation, the fifth dog clutch C5that had been linking the second speed-change shaft20and the 6th-speed drive gear22is first disengaged when fifth speed is selected, as shown inFIG. 16. The cone clutch24cof the synchronizing mechanism24is thereafter moved to the input side, as shown inFIG. 17, and the second speed-change shaft20and the first synchronizing gear24aare momentarily linked. At this point, the first synchronizing gear24ais meshing with the first intermediate gear46a, and the rotation of the first transmission mechanism3is therefore transmitted to the second speed-change shaft20via the first intermediate gear46aand the first synchronizing gear24a. Here, each speed-change step is set so that the difference in step intervals between the speeds is constant, and the difference in step interval is set by the gear ratio between the first intermediate gear46aand the first synchronizing gear24a, or by the number of gear teeth of the gears so as to establish the same gear ratio as the gear ratio between the second intermediate gear46band the second synchronizing gear24b. Therefore, the fifth dog clutch C5is disengaged and the synchronizing mechanism24is momentarily engaged in the state in which the fifth speed has been selected, whereby the rotational speed of the second speed-change shaft20is brought to the same or nearly the same level as the rotational speed maintained when the fourth speed has been selected.

After such synchronization has been carried out, the fourth dog clutch C4is engaged, and the second speed-change shaft20and the 2nd- and 4th-speed drive gears21are linked, as shown inFIG. 18(the synchronizing mechanism24is already off). At this point, the fourth dog clutch C4can be made to smoothly mesh because the rotational speed of the second speed-change shaft20is controlled by the synchronization carried out by the synchronizing mechanism24as described above. The first snap clutch SC1is subsequently disengaged and the second snap clutch SC2is engaged, as shown inFIG. 19. Power is thereby transmitted via the pathway shown by the solid line inFIG. 19, and the change to fourth speed is completed.

Synchronization is carried out by essentially the same operation as that described above during other speed change operations, and smooth speed changing is made possible.

Effects of the Present Embodiment

With this device, ten speed-change steps can be obtained during forward travel as well as during reverse travel using a single set of transmission mechanisms3,4by providing the pre-stage of the transmission mechanism with two snap clutches SC1, SC2and a single pair of clutches F, R for switching between forward and reverse travel.

In this case, it is also possible to consider providing the pre-stage of the transmission mechanism with a planetary gear mechanism for switching the direction of rotation as a mechanism for obtaining a plurality of speed-change steps in forward and reverse travel, but the present embodiment provides a configuration in which less space can be used in the axial direction and the size of the overall device can be reduced in comparison with the case in which a planetary gear mechanism is provided. This device can be made the same size as a conventional transmission without increasing the size in the lateral and vertical directions (the directions orthogonal to the shafts). In other words, a conventional transmission has an input shaft, a first speed-change shaft, and a second speed-change shaft, and each of the shafts has a hydraulic clutch. In the present device, however, space in the lateral and vertical directions is not increased because the input shaft and the second speed-change shaft are each merely provided with a coaxially disposed clutch mechanism.

Since the first and second transmission mechanisms3,4are configured using dog clutches rather than hydraulic clutches such as in a conventional device, the configuration is simplified in comparison with a conventional transmission.

In the present embodiment, each forward and reverse speed-change step can be smoothly and rapidly changed because pre-shifting is performed during each speed change, and synchronization is carried out by the synchronizing mechanism24.

In this device, the forward clutch F and the first snap clutch SC1are coaxially arranged as the first clutch pair5F, and the reverse clutch R and the second snap clutch SC2are coaxially arranged as the second clutch pair5R. Therefore, the clutch case as a component of the clutches can be shared and the configuration can be simplified.

In this device, the engine and the transmission are linked using a hydraulic clutch rather than a torque converter. Therefore, the power of the engine can be transmitted with good efficiency.

Other Embodiments

(a) In the embodiment described above, an example of ten steps in forward and reverse travel was described, but the number of speed-change steps is not limited to the one specified in the embodiment.

(b) The presence of a synchronizing mechanism and the configuration of the clutches including the dog clutches are not limited to those specified in the embodiment described above.

(c) In the embodiment described above, the forward clutch F and the first snap clutch SC1are coaxially arranged, and the reverse clutch R and the second snap clutch SC2are coaxially arranged, but any combination of these may be selected.

(d) In the embodiment described above, the first clutch pair5F is disposed coaxially with the input shaft2, and the second clutch pair5R is disposed coaxially with the second speed-change shaft20, but the configuration of the present invention is not limited to this option alone. For example, the second clutch pair5R may be disposed coaxially with the input shaft, and the first clutch pair5F may be disposed coaxially with the first speed-change shaft12or the second speed-change shaft20.

In accordance with the embodiments described above, a transmission for an industrial vehicle that has a simple configuration and good efficiency can be obtained.