GB2148419A - Transmission for a riding mower - Google Patents

Abstract

A transmission device having an input shaft 12 supporting a reverse drive sprocket 15 and a plurality of forward speed-change drive gears 161-165, and a speed-change shaft 17 supporting a reverse driven sprocket 19 and a plurality of forward speed-change driven gears 211-215, the input and speed-change gears being disposed parallel to each other. The reverse sprocket and forward speed-change gears on each of the input and speed-change gears are successively arranged in adjacent relation. Slide keys 23 are mounted on the speed-change shaft for selectively engaging inner peripheral edges of the driven sprocket and driven gears on the speed-change shaft for selectively transmitting rotation of the input shaft to the speed-change shaft, the driven gears and the reverse sprocket all being on the same side of sliding means 24 for supporting and moving the keys 23. <IMAGE>

Description

SPECIFICATION Transmission device BACKGROUND OF THE INVENTION 1. Field of the invention: The present invention relates to a transmission device for use in a working vehicle such as a riding mower.

2. Description of the Prior Art: Riding mowers have two rear wheels and are operated by an operator riding on the mower to run over and cut off grass. The riding mower requires a transmission identical to that employed in ordinary passenger cars for driving the mower at desired speeds. The transmission in the riding mower has a wide range of gear ratios since the mower is required to move at a low speed while cutting off grass and to run quickly at a considerably high speed when going to an area where grass is to be cut or after having cut off grass.

The riding mower is driven by a single operator, and hence has a small size with reduced longitudinal and transverse dimensions. Accordingly, the transmission for use therein is required to be small in size, and also simple in construction to meet a demand for low-cost working vehicles. Other requirements for the riding mower transmission are that it have sufficient functions and reliability.

One known riding mower transmission is disclosed in U.S. Patent No. 4,103,566 and the disclosed transmission will be described with reference to Fig. 8 of the accompanying drawings.

The prior art transmission has a transmission case 51 with a central input shaft 52 extending transversely therein. A speedchange shaft 53 is supported in the transmission case 51 in a front position therein, the speed-change shaft 53 extending parallel to the central input shaft 52. Drive axles 54, 55 for wheels are also supported in the transmission case 51 in rear position therein, the drive axles 54, 55 extending parallel to the central input shaft 52. A differential gear device 56 is interposed between confronting ends of the drive axles 54, 55. An input driven bevel gear 57 is splined to or otherwise fitted over an axially intermediate portion of the input shaft 52; and is driven by a drive bevel gear on a propeller shaft (not shown).A plurality of drive gears 58A through 58E are splined to or otherwise mounted on the input shaft 52 one side (righthand side, as shown) of the bevel gear 57 for rotation with the input shaft 52.

The drive gears 58A through 58E are progressively greater in diameter in a direction away from the bevel gear 57 toward a shaft end, the drive gear 58A closest to the bevel gear 57 being smallest in diameter.

Speed-change driven gears 59A through 59E are rotatably fitted over the speed-change shaft 53 and progressively greater in diameter in a direction from a shaft end toward a central portion of the shaft 53. The gears 59A through 59E are held in mesh with the corresponding gears 58A through 58E, respectively. Therefore, when the gear 57 is driven, the shaft 52 is rotated about its own axis to cause the gears 58A through 58E to rotate the gears 59A through 59E idly on the shaft 53. The speed-change driven gears 59A through 59E have engagement slots 59a in inner peripheral edges thereof. There are spacer rings 59b between the speed-change driven gears 59A through 59E.

A reverse driven sprocket 60 is loosely fitted over the speed-change gear 53 remotely from the speed-change driven gears 59A through 59E. An output gear 61 is splined to or otherwise mounted on the end of the shaft 53 and spaced from the reverse driven sprocket 60 with a sleeve boss 60a serving as a spacer between the reverse driven gear 60 and the output gear 61. The sprocket 60 is operatively coupled by a chain 63 to a driven sprocket 62 mounted for corotation on the input shaft 52 and spaced axially from the bevel gear 57. The output gear 61 is held in mesh with a larger-diameter driven gear 65 mounted on an end of a final gear 64 loosely fitted over an end portion of the input shaft 52 which extends outwardly of the sprocket 62. The final gear 64 is in mesh with a gear 67 on a differential cage 66 of the differential gear device 56.

A speed-change or shift control mechanism is operatively disposed between the gear 59A on the speed-change shaft 53 and the sprocket 60. The shift control mechanism is composed of a slider 68 axially slidably fitted over the shaft 53 between the gear 59A and the sprocket 60, engagement bars 69 mounted on one end of the slider 68 for radially swinging movement, and a projection 70 on the other end of the slider 68. The slider 68 is axially movable by a shift fork 61.

The sprocket 60 has a recess 60a defined in an inner end surface thereof for receiving the projection 70 therein. The projection 70 and the recess 60a jointly constitute a dog clutch.

The parts are shown as being in a neutral position in Fig. 8. By moving the shift fork 71 to the right in Fig. 8, engagement ends of the engagement bars 69 selectively engage in the slots 59a in the gears 59A through 59E dependent on the stroke of axial movement of the engagement bars 69. The shaft 53 is now driven to rotate at a given speed-change ratio, and the rotative power is transmitted through the gears 61, 65, 64 and the differential gear device 56 to the wheel axles 54, 55. The engagement bars 69 are allowed to swing radially in the slots 53a defined in the shaft 53. For a reverse movement of the vehicle, the slider 68 is moved leftward from the illustrated position to enable the projection 70 to engage in the recess 60a.Then, output power from the sprocket 62 is transmitted to the shaft 53, and rotative power from the shaft 53 is transmitted through the gears 61, 65, 64, 67 to the wheel axles 54, 55, which are turned in an opposite direction to reverse the vehicle.

With the foregoing prior art construction, the forward speed-change gears 59A through 59E are disposed on one axial end of the shaft 53 while the reverse sprocket 60 is mounted on the other axial end of the shaft 53, the shift control mechanism is positioned between the gears 59A through 59E and the sprocket 60, and the output gear 61 on the shaft 53 is disposed outwardly of the sprocket 60 to avoid interference with the shift control mechanism. Therefore, the gears and sprocket on the input shaft 52 are required to be positioned in radial alignment with the gears and sprocket on the shaft 53. The shafts 53, 52 should be of increased lengths to support these gears and sprockets. In addition, the gears 61, 65 are also mounted on the ends of the shafts 53, 52. As a result, the transmission device, including the transmission case 51, has an increased width.Since the gears 61, 65 are displaced toward the ends of the shafts 53, 52, the gear 67 of the differential gear device 56 should also be positioned closely to one end thereof. The design goes counter to a demand that the wheel axles 54, 55 be equal in length. The conventional layout is poor in space utilization since there is a dead space around the axle 55 near the gears 58A through 58E. The differential gear device 56 is located in axially spaced relation to the gears 58A through 58E, with the bevel gear 57 and other parts located adjacent to the differential gear device 56. The transmission case 51 is of an increased length.

The transmission device of the prior art is therefore large in size and heavy.

SUMMARY OF THE INVENTION With the conventional shortcomings in view, it is an object of the present invention to provide a transmission device which has reduced transverse and longitudinal dimensions, is compact and lightweight, and has a differential gear device located as closely to the longitudinal central axis of a vehicle as possible for driving wheels more efficiently.

To achieve the above object, there is provided according to the present invention a transmission device comprising a propeller shaft drivable by an engine, an input shaft disposed substantially perpendicularly to the propeller shaft and drivable thereby, the input shaft having first and second ends, a reverse drive rotatable member and a plurality of forward speed-change drive gears disposed on the input shaft and successively arranged from a position near the first end toward the second end, a speed-change shaft disposed adjacent and substantially parallel to the input shaft and having first and second ends and an intermediate portion, a reverse driven rotatable member and a plurality of forward speedchange driven gears disposed idly rotatably on the speed-change shaft and successively arranged from the intermediate portion toward the second end of the speed-change gear, the reverse driven rotatable member being operatively coupled by a chain to the reverse drive rotatable member on the input shaft, the driven gears being held in mesh respectively with the drive gears, an engagement member mounted corotatably and axially slidably on the speed-change shaft and selectively engageable with inner peripheral edges of the driven rotatable member and the driven gears on the speed-change shaft for selectively transmitting rotative power from the input shaft to the speed-change shaft, a slide member mounted on the speed-change shaft more closely than the reverse driven rotatable member to the first end of the speed-change shaft, the engagement member being supported by the slide member so as to be rotatable with and axially slidable on the speed-change shaft, a mechanism for moving the slide member in response to operation of external means, and an output member mounted on the speed-change shaft at the second end thereof beyond the driven gears, for transmitting rotation of the speed-change gear to a differential gear device.

The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevational view of a riding mower in which a transmission device of the present invention is incorporated; Figure 2 is an enlarged cross-sectional view taken along line 2-2 of Fig. 1; Figure 3 is an enlarged fragmentary crosssectional view of a support construction for a bevel pinion gear for picking up engine output power; Figure 4 is an enlarged cross-sectional view of the transmission device shown in Fig. 2; Figure 5 is a cross-sectional view of a separate gear on an input shaft; Figure 6 is a cross-sectional view taken along line 6-6 of Fig. 4; Figure 7 is a cross-sectional view taken along line 7-7 of Fig. 4; and Figure 8 is a cross-sectional view of a prior art transmission device.

DESCRIPTION OF THE PREFERRED EMBODI MENT Fig. 1 schematically shows a riding mower 1 as an example of a working vehicle to which the present invention is applied. The riding mower 1 has a body 2 having a front portion accommodating an engine 3 and a rear portion with a driver's seat 4 mounted thereon. The body 2 supports two front wheels 5 serving as steerable wheels on the front portion of the body 2 and two rear wheels 6 serving as drive wheels on the rear end of the body 2. A housing 8 covering grass cutter blades 7, 7 is attached to a central lower portion of the body 2. The grass cutter blades 7, 7 are arranged tandemly in a longitudinal direction of the body 2, and driven by a belt driven mechanism 9 composed of a drive pulley mounted on a front end of the engine 3, a directional pulley, a driven pulley, a belt trained therearound, and other pulleys and belt.

The rear wheels 6, 6 are driven through a transmision device 11 by a propeller shaft 10 extending rearwardly from a rear end of the engine 3 and inclined slightly downwardly toward a rear end of the propeller shaft 10.

To the rear end of the propeller shaft 10 is coupled a gear shaft 102 having an integral bevel pinion gear 101 for supplying an engine power output, as shown in Fig. 2. A transmission mechanism including the bevel pinion gear 101 and a differential gear device are enclosed by a protective transmission case 111. The transmission case 111 is composed of transversely separate case members 112, 11 3 joined together, with the gear shaft 102 covered by a cover 114.

As clearly illustrated in Fig. 3, the transmission case 111 has a hole 103 through which the bevel pinion gear 101 extends. The gear shaft 102, integral with the pinion gear 101, is rotatably supported by a bearing 104 disposed in the hole 103. The bearing 104 has an inner race 1 04b mounted on the gear shaft 102 and axially positioned with respect to the gear shaft 102 by being clamped between a step 102a of the pinion gear 101 and a bearing retainer 107 such as a lock nut threaded over the gear shaft 102. The bearing 104 also has an outer race 1 04a mounted in the hole 103 and axially positioned with respect thereto by being clamped between a shim 106 on a step 105 of the transmission case 111 and a bearing retainer 108 such as a lock nut threaded in the hole 103.The bevel pinion gear 101 is held in mesh with a bevel gear 14 adjustably dependent on the thickness of the shim 106, the bevel gear 14 being rotatably supported in the transmission case 111. For replacing the shim 106, the bearing retainer 108 is detached to allow the pinion gear 101, the bearing inner race 107 thereon, and the bearing 104 to be pulled out of the hole 103. Then, the shim 106 is replaced with a new one through the hole 103. Thereafter, the piniòn gear 101, the bearing inner race 107 thereon, and the bearing 104 are inserted into the hole 103, and then the bearing retainer 108 is fastened in place to press the bearing outer race 104a against the step 105 through the shim 106.

As shown in Fig. 2, an input shaft 1 2 is disposed rearwardly of the gear shaft 102 in a perpendicular relation thereto, and mounted in the transmission case 111 transversely of the riding mower 1. The input shaft 1 2 has opposite ends rotatably supported by bearings 13, 1 3 on the case members 112, 113, respectively. The bevel gear 14, serving as a transmission mechanism input (driven) gear, is splined to or otherwise mounted on an end of the input shaft 1 2 which is close to the bevel gear 101, the bevel gear 14 meshing with the bevel gear 101 as described above.The input shaft 1 2 has a reverse drive sprocket 1 5 located axially adjacent to the gear 14 and remote from the bearing 1 3. A forward drive gear assembly 1 6 is mounted on the input shaft 1 2 on a side of the reverse drive sprocket 1 5 remote from the gear 14. The forward drive gear assembly 1 6 comprises five, axially arranged, forward drive gears 1 61 through 165 in the illustrated embodiment.

The gear 1 61 which is closest to the sprocket 1 5 has a smallest diameter, and the other gears are progressively greater in diameter in a direction away from the sprocket 1 5 toward an end of the input shaft 12. The gear 165 which is closest to the case member 112 is of a greatest diameter. In the illustrated embodiment, the gear 1 61 which is a 1st-speed gear is integrally formed with the input shaft 12, and the gears 162, 163, 164, 165 which are 2nd-, 3rd-, 4th-, and 5th-speed gears are splined separately to the input shaft 1 2.

As shown in Fig. 5, the 2nd-speed gear 1 62 has a clear recess 1 62a of a relatively larger diameter defined in an end surface facing the 1st-speed gear 1 61. When the gear 1 62 is splined to the input shaft 12, rising edges 1 61 a of spline grooves 121 defined in the input shaft 12, adjacent to the gear 161, are positioned in the clear recess 162a. Therefore, the gear 1 62 can be held in intimate contact with the gear 1 61 without being caught by the rising edges 161a (Fig. 4).

A rotative output from the propeller shaft 10 is transmitted through the bevel pinion gear 101 and the bevel gear 14 to the input shaft 1 2 to drive the sprocket 1 5 and the gears 161 through 165.

A speed-change shaft 1 7 is disposed behind the input shaft 1 2 parallel thereto. The speed-change shaft 1 7 is longer than the input shaft 1 2 and has a lefthand (as shown) end 171 rotatably supported by a bearing 18 on a shaft support 112 of the lefthand (as shown) case member 11 2 and a righthand end 1 72 projecting laterally beyond the righthand end of the input shaft 1 2. The righthand case member 11 3 has an outwardly bulging portion 11 3b including a shaft sup port 11 3a on which the projecting righthand end 1 72 of the shaft 1 7 is rotatably supported by a bearing 18.

A reverse driven sprocket 1 9 is loosely fitted over the speed-change shaft 1 7 on a substantially central portion thereof in alignment with the sprocket 1 5. A neutral collar 20 having a smallest diameter is loosely fitted over the shaft 1 7 adjacent to a side of the sprocket 1 9 which is remote from the righthand end 1 72. A forward driven speed change gear assembly 21 is loosely fitted over the shaft 1 7 adjacent to the collar 20 and comprises first through fifth, or 1 st- through 5th-speed, successive driven gears 211 through 21 5. The first driven gear 211 closest to the collar 20 has a largest diameter and is in mesh with the smallest-diameter drive gear 1 61 to provide a greatest speed reduction ratio. The second through fifth gears 212-125 have progressively smaller diameter. The endmost fifth gear 215 has a smallest diameter among the gears 211 through 215, and is held in mesh with the largest-diameter drive gear 165 to provide a smallest speed reduction ratio. The other driven gears 212-214 are held in mesh with the drive gears 162-164, respectively. Washers 22 are interposed between the gears 211-21 5, the sprocket 19, and collar 20 on the shaft 17.The gears 211-215, the collar 20, and the sprocket 1 9 have key slots 211a-215a, 20a, 19a, respectively, defined in inner peripheral surfaces thereof.

In the illustrated embodiment, the 2ndspeed drive gear 162 is slightly wider than the driven gear 212 meshing therewith, and the 4th speed drive gear 1 64 has bosses 1 64 formed on inner peripheral portions thereof and projecting axially away from each other to provide clearances between the drive gear 164 and the drive gears 163, 165. This gear arrangement allows the 1 st- through 5thspeed driven gears 211-215 to be axially spaced with certain clearances therebetween.

A pair of axially elongate slide keys 23, 23 is disposed in inner holes in the gears, the collor, and the sprocket on the shaft 1 7, the slide keys 23, 23 being spaced 180 from each other. The slide keys 23, 23 are rotatable with the shaft 1 7 and axially slidable along the shaft 17. The shaft 1 7 has key slots 173, 173 cooperating with the key slots 211a-215a, 20a, 19a in the gears 211-21 5, the collar 20, and the sprocket 19 in axially receiving the slide keys 23, 23. Fig.

6 shows the relationship of the key slots 211a,--173 in the first driven gear 211 and the shaft 17, and the slide keys 23. Each of the slide keys 23, 23 comprises a body 231 having a length which is substantially the same as the total axial length of the gears 215-211, the collar 20, and the sprocket 19, an engagement projection 232 projecting radially outwardly from a distal end of the slide key 23, and a proximal portion 233 projecting radially outwardly from a proximal end of the body 231.The proximal portion 233 is inserted in a recess in an end 241 of a slider 24 rotatable with the shaft 1 7 and axially slidably fitted over the shaft 1 7. The proximal portion 233 is pivotably supported by a pin 242 on the slider 24, so that the body 231 will be angularly movable toward and away from the shaft 1 7 in the radial direction. The slider 24 has hollow cylindrical portions 243, 243 projecting radially outwardly in diametrically opposite relation from a central portion of the slider 24. The cylindrical portions 243, 243 have openings 244, 244 defined in lower front walls thereof and in which there are freely movable disposed extensions 234, 234 from the proximal portions 233, 233 of the slide keys 23, 23.Balls 246, 246 normally urged radially inwardly by springs 245, 245 are fitted in the cylindrical portions 243, 243 and held against the extensions 234, 234, respectively. The extensions 234, 234 are therefore normally urged resiliently radially inwardly to cause the distal projections 232, 232 to be lifted radially outwardly resiliently.

Stops 247 are fastened to the cylindrical portions 243 for the springs 245, 245.

The slider 24 has an annular groove 249 defined in an outer peripheral surface of an end of the slider 24. Pins 252 (only one shown in Figs. 2 and 4) mounted on distal ends of legs 251 of a shift fork 25 engage in the annular groove 249. The shift fork 25 has a proximal portion 253 fastened to a support shaft 254 which can be operated by an external shift control mechanism such for example as a gear shift lever.

Drive power from the drive gears 1 61-1 65 and the sprocket 1 5 is transmitted to the driven gears 221-215 and the sprocket 19 but in a neutral gear position, the gears 211-215 and the sprocket 19 rotate idly on the shaft 1 7. The illustrated gear position is a 5th-speed position in which the speed reduction ration is the smallest. In this position, the projections 232 of the slid keys 23 engage in the key slots 21 5a in the fifth driven gear 215, allowing drive power to be transmitted from the drive gear 1 65 to the speed-change gear 1 7 to rotate the same at a high speed.

The other gears 211-214 and the sprocket 1 9 rotate idely on the shaft 1 7 since they are not in engagement with the slide keys 23.

When the shift fork 25 is turned clockwise upon rotation of the support shaft 254, the slider 24 is moved to the right on the shaft 17, and slant surfaces 232a of the projections 232 of the slide keys 23 slide radially inwardly against the washers 22 to enable the projections 232 to move radially inwardly against the resilient forces of the springs 245.

As the projections 232 ride over the washers 22 into the next key slots 214a, a next gear position or 4th-speed gear position is selected.

Continued rightward movement of the slider 24 causes the projections 232 to move successively through the key slots 213a-211a until finally the projections 232 engage in the key slots 20a in the neutral collor 20, whereupon drive power from the shaft 1 2 the shaft 1 7 is cut off. When the shift fork 25 is moved in an opposite direction, slant surfaces 232b of the projections 232 slide against the washers 22 to cause the projections 232 to move radially inwardly over the washers 22 into desired ones of the key slots 211 a-215a to select one of the 1 sot through 5th speeds.Upon further rightward movement of the projections 232 from the neutral collar 20, the projections 232 engage in the key slots 1 9a in the reverse sprocket 19, and drive power is now transmitted through the chain 26 and the sprocket 1 9 to the shaft 1 7 to rotate the same in an opposite direction to move the riding mower 1 backwardly.

The neutral collar 20 is supported on the shaft 1 7 by at least one of the washers 22 on axial ends of the collar 20, for example the washer 22 disposed between the collar 20 and the driven sprocket 1 9 and having a shoulder engaging in a recess 20b defined in the collar 20.As shown in Fig. 7, the collar 20 has an inner circular hole having a diameter larger than that of the shaft 1 7 to define an annular gap between the collar 20 and the shaft 17, the gap corresponding the depth of the key slots 21 1a-21 5a in the gears 211-21 -215.1f the collar 20 had an inner peripheral shape with key slots as shown in Fig. 6, the slide keys 23 would interfere with the edges of the key slots at the time of moving the slide keys 23 to the neutral position corresponding to the collar 20, failing to allow the slide keys 23 to slide smoothly.

However, the arrangement shown in Fig. 7 permits the slide keys 23 to slide smoothly to the neutral position.

A drive gear 27 is mounted for corotation on the shaft 1 7 adjacent to the end 1 71 thereof, and is held in mesh with a largerdiameter gear 281 on an end of an intermediate shaft 28 extending parallel to the shaft 1 7 on the rear side thereof. The intermediate shaft 28 has a final output gear 282 on an axially central portion thereof, and includes opposite ends 283, 284 rotatably suported by bearings 29, 29 on shaft supports 112c, 11 3c, respectively, of the case members 112, 113.

The transmission case 111 has a rearward extension 111 a on which a pair of rear wheel axles 30, 31 is supported parallel to the input shaft 12 and the speed-change gear 1 7. The axles 30, 31 are supported in the following manner: The case members 112, 11 3 of the transmission case 111 are separably joined together across a plane lying perpendicularly to the axes of the axles 30, 31. The case members 112, 113 have integral tubular portions 112d, 113d, respectively, on a rear end thereof which project away from each other in the directions of the axes of the axles 30, 31.

A differential gear device 33 is disposed axially between the axles 30, 31 and includes a differential cage 331 having an integral gear 332 meshing with the final output gear 282 of the intermediate shaft 28, and integral sleeves 335 confronting each other in alignment with the axes of the axles 30, 31 and through which inner ends of the axles 30, 31 extend respectively. The tubular portions 112d, 11 3d have bearings 32 mounted in inner ends thereof with the sleeves 335 rotatably supported in the bearings 32. The tubular portions 112d, 11 3d also have bearings 35 mounted in outer ends thereof and directly supporting the axles 30, 31 rotatably therein and seal rings 36 mounted in the outer ends of the tubular portions 112d, 11 3d axially outwardly of the bearings 35.Each of the axles 30, 31 is therefore supported at two axially spaced locations by the transmission case 111 with sufficiently high rigidity.

Pinions 334, 334 are housed in the differential cage 331 and loosely fitted over a pinion shaft 333 extending centrally through the differential cage 331. The pinions 334, 334 are held in mesh with side gears 301, 311 mounted on the confronting ends of the axles 30, 31. Therefore, rotative power from the shaft 1 7 is transmitted through the gears 27, 281, 282,332,334,301,311 to the axles 30, 31.

In operation, drive power from the propeller shaft 10 is transmitted to the input shaft 1 2 to drive the sprocket 1 5 and the gears 161-165, and drive power is then transmitted through a selected one of the gears 211-125 and the sprocket 19, the shaft 17, the intermediate shaft 18, the differential gear device 33 to the axles 30, 31.

In the transmission device as described above, the gear assemblies 16, 21 and the reverse sprockets 15, 1 9 are located adjacent to each other on the shafts 12, 1 7. According to this layout, the transmission case 111 has a width much smaller than the width of the conventional transmission case, with only the gear shift components 23, 24, 25 projectable laterally. Therefore, the overall side of the transmission device is reduced. Since the gears and reverse sprockets are not divided on axially opposite sides on the shafts 12, 17, the shafts 12, 1 7 are short and are not required to be supported on intermediate portions thereof. The shafts 12, 1 7 are therefore of a reduced diameter and weight. Due to the fact that the gear assemblies 16, 21 and the sprockets 15, 1 9 are disposed closely to each other, the differential gear device can be located in the vicinity of these gears and sprockets. This arrangement is effective to reduce the longitudinal dimension of the overall transmission device, and achieves a more compact and lightweight construction of the overall transmission device while at the same time maintaining a desired gear shifting capability. The transmission device of the invention has another functional advantage in that the differential gear device can be located closely to the longitudinal axis of the vehicle.

Although there has been described what is at present considered to be the preferred embodiment of the present invention, it will be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all aspects as illustrative, and not restrictive. The cope of the invention is indicated by the appended claims rather than by the foregoing description.

Claims (10)

1. A transmission device comprising: (a) a propeller shaft drivable by an engine; (b) an input shaft disposed substantially perpendicularly to said propeller shaft and drivable thereby, said input shaft having first and second ends; (c) a reverse drive rotatable member and a plurality of forward speed-change drive gears disposed on said input shaft and successively arranged from a position near said first end toward said second end; (d) a speed-change shaft disposed adjacent and substantially parallel to said input shaft and having first and second ends and an intermediate portion; (e) a reverse driven rotatable member and a plurality of forward speed-change driven gears disposed idly rotatably on said speed-change shaft and successively arranged from said intermediate portion toward said second end of said speed-change shaft;; (f) said reverse driven rotatable member being operatively coupled by a chain to said reverse drive rotatable member on said input shaft, said driven gears being held in mesh respectively with said drive gears; (g) an engagement member mounted corotatably and axially slidably on said speedchange shaft and selectively engageable with inner peripheral edges of said driven rotatable member and said driven gears on said speedchange shaft for selectively transmitting rotative power from said input shaft to said speedchange shaft; (h) a slide member mounted on said speedchange shaft more closely than said reverse driven rotatable member to said first end of said speed-change shaft, said engagement member being supported by said slide member so as to be rotatable with and axially slidable on said speed-change shaft;; (i) a mechanism for moving said slide member in response to operation of external means; and (j) an output member mounted on said speed-change shaft at said second end thereof beyond said driven gears, for transmitting rotation of said speed-change shaft to a differential gear device.

2. A transmission device according to claim 1, wherin said speed-change shaft is longer at said first end thereof than said input shaft.

3. A transmission device according to claim 1, wherein said forward speed-change drive gears are progressively greater in diameter from one of them positioned adjacent to said reverse drive rotatable member toward said second end of said input shaft, and said forward speed-change driven gears are progressively smaller in diameter from one of them positioned adjacent to said reverse driven rotatable member toward said second end of said speed-change shaft.

4. A transmission device according to claim 1, wherein said reverse driven rotatable member on said speed-change shaft is disposed axially closely to said forward speedchange driven gears with a collar interposed therebetween, said engagement member being engageable with said collar to select a neutral position.

5. A transmission device according to claim 1, wherein said forward speed-change drive gears on said input shaft include an integral gear integral with said input shaft and a plurality of seperate gears splined to said input shaft, said input shaft having spline grooves terminating in rising edges at one side of said integral gear, one of said separate gears adjacent to said integral gear having a clear recess defined in an end surface facing said integral gear and receptive of said rising edges of said spline grooves so as to be in intimate contact with said integral gear.

6. A transmission device according to claim 1, including a drive bevel gear coupled with one end of said propeller shaft, said input shaft having on said first end thereof a driven bevel gear held in mesh with said drive bevel gear.

7. A transmission device according to claim 6, including a case accommodating at least said input shaft therein, said case having a hole through which said drive bevel gear extends, said drive bevel gear having a gear shaft of its own and rotatably supported in said hole by a bearing on said gear shaft, said bearing having an inner race mounted on said gear shaft and an outer race disposed in said hole, further including a shim interposed between an axial end surface of said outer race on the side of said drive bevel gear and a surface defining said hole and confronting said axial end surface.

8. A transmission device comprising: (a) an input shaft; (b) a transmission gear mechanism; (c) an output shaft operatively coupled to said input shaft through said transmission gear mechanism; (d) a differential gear device operatively coupled to said output shaft; (e) a pair of axles extending in opposite directions from said differential gear device; (f) a transmission case housing therein said input shaft, said output shaft, and said axles in parallel relation to each other; (g) said transmission case being composed of two case members separated by a plane lying substantially perpendicular to axes of said axles; and (h) said case members having respective tubular portions projecting away from each other along said axes of said axles, said axles being supported by said tubular portions, respectively.

9. A transmission device according to claim 8, wherein each of said axles is supported at two axially spaced locations by one of said tubular portions of said case members.

10. A transmission device including an input shaft mounting a plurality of forward speed-change drive gears and a reverse drive rotary member, a speed-change shaft disposed adjacent and parallel to said input shaft, said speed-change shaft having a plurality of forward speed-change driven gears and a reverse driven rotary member mounted for idle rotation thereon, an engagement member mounted axially slidably on said speed-change shaft for rotation therewith and selectively engageable with means disposed peripherally inwardly of said forward driven gears and said reverse driven member so as selectively to transmit drive from said input shaft to said speed-change shaft, and a slide member supporting said engagement member and being operable to select a transmission ratio, said reverse driven rotary member being mounted on said speed-change shaft between said forward driven gears and said slide member.