GB2036208A - Countershaft gearing - Google Patents

Abstract

A multiple-ratio, manually-controlled, synchronized power transmission for an agricultural tractor wherein provision is made for reducing the rotating inertia mass of the torque delivery elements of the power transmission mechanism during speed ratio changes thereby simplifying the transmission ratio shifting sequence and improving the shift quality. Change-speed countershaft gearing comprises an input shaft 86 supporting an input gear 112 and two interconnected input gears 114, 118, having a synchronizer clutch means 124 for engaging gear 112 or 114; and a countershaft 146 supporting interconnected gears 160, 162 and a third gear 164, having a synchronizer clutch means 170 for engaging gear 162 or 164. The countershaft is coupled to an output shaft 192 by a range gearing providing high, low or reverse ranges. The countershaft gearing is preceded by a planetary reduction gearing providing either direct or reduced drive and itself preceded by a main clutch. <IMAGE>

Description

SPECIFICATION Transmission assembly This invention relates to transmission assemblies.

U.S. Patents Nos. 3,293,933; 3,542,176; 3,115,047; 3,173,303 and 3,886,815 disclose transmission assemblies suitable for use in tractors.

Tractor transmission assemblies normally include a main shaft and a countershaft arranged in parallel disposition. The countershaft is connected to an output shaft through drive range gearing so that the multiple ratio transmission gearing can operate either in a high drive range or a low drive range depending upon the output torque that is required.

The input shaft is connected to the tractor engine through a neutral clutch. A power gear for establishing a further speed reduction or a 1:1 driving ratio can be introduced between the torque output element of the neutral clutch and the input gear element of the multiple ratio transmission to provide an additional drive range.

According to the present invention, there is provided a transmission assembly comprising a power input shaft and a countershaft arranged in parallel disposition, a first input gear journalled for rotation about the input shaft, second and third input gears connected together and mounted for rotation about the input shaft, first, second and third driving gears mounted for rotation about the countershaft, said first and second driving gears being connected together, first synchronizer clutch means connected drivably to said input shaft for connecting together selectively said input shaft and said first and second input gears, second synchronizer clutch means carried by said countershaft for connecting together selectively said countershaft and said second and third driving gears, an output shaft and final drive means for connecting said countershaft to said output shaft, said first input gear being connected to said input shaft by said first clutch means during first and third speed ratio operation and said second input gear being connected to said input shaft by said first clutch means during second and fourth speed ratio operation, said third driving gear being connected to said countershaft by said second synchronizer clutch means during first and second speed operation and said second driving gear being connected to said countershaft by said second synchronizer clutch means during third and fourth speed operation.

By using a double acting synchronizer mounted concentrically on the power input shaft and a companion synchronizer mounted concentrically about the countershaft, the system can be fully synchronized. The synchronizers are arranged strategically soo that during a ratio change from the second ratio to the third ratio, the power input gear and the neutral clutch are disengaged from the rotating gear elements, and the rotating mass inertia is reduced accordingly. The same is true on a downshift from a third ratio to the second ratio.This synchronizer clutch arrangement and its shift pattern is distinguished from prior art designs in which the rotating mass is connected to the power input shaft and forms a part of the power delivery path at the instant the ratio change is made or prior to the ratio change thereby making shifting much more difficult if not impossible to achieve while the vehicle is moving.

Unlike many tractor transmissions of known design, the present invention makes it unnecessary for the tractor operator to bring the tractor to a stop prior to shifting from one ratio to another.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the drawings, in which Figure 1 is a cross-sectional assembly view of the main elements of a gear system of a tractor transmission assembly in accordance with the invention; Figure 2 is a diagram showing the shift pattern that is followed by the manually controlled gearshift linkage as the synchronizers shown in Fig. 1 are operated; Figure 3 is a cross-sectional view of a power gear which may be used between the tractor neutral clutch and the input element of the gear system of Fig. 1; and Figure 4 is a cross-sectional assembly view of a neutral clutch used to connect the tractor engine to the torque input side of the power gear of Fig. 3.

In Fig. 4 reference numeral 10 shows one end of the crankshaft of an internal combustion tractor engine. Crankshaft end 10 is connected to a flywheel 1 2. A neutral clutch 14 is adapted to connect respectively the flywheel 1 2 to a power sleeve shaft 1 6.

Clutch 1 4 comprises a clutch disc 1 8 carried by clutch disc hub 20 which, in turn, is splined to the shaft 1 6 at 22. A clutch housing 24 supports clutch release levers 26 which, when rotated in a counterclockwise direction as seen in Fig. 4, cause the clutch pressure plate 28 to disengage the disc 1 8.

Pressure plate 28 normally is pressed against the clutch disc by clutch apply spring 30.

The clutch is applied and released by the operator as he moves a clutch throw-out bearing hub 32 in one direction or the other.

Upon movement in a left-hand direction (as seen in Fig. 4) the clutch throw-out bearing 32 engages clutch release ring 34 which engages the operating ring of the clutch release levers 26.

The driver-operated, clutch operating mechanism for moving the clutch throw-out bearing is shown generally at 36. Lever 36 is pivoted on the transmission housing, and the driver controlled clutch pedal is connected to the operating end of the lever 36 as shown at 38.

The end 40 of the lever 36 is connected to the clutch throw-out bearing sleeve 42.

A power takeoff shaft 44 is splined at 45 to the engine crankshaft to provide a direct driving connection between the engine and the output end of the PTO shaft, which will be described with reference to Fig. 1.

Fig. 3 shows a power gear which may be used between the neutral clutch of Fig. 4 and the gearing system of Fig. 1. The power gear is enclosed within a gear housing 46 which may, as shown, form part of a main transmission housing or which may be bolted or otherwise connected directly to it. A forward stationary support wall 48, which is bolted at its margin to power gear housing support 50, forms a support for clutch throw-out bearing support sleeve 52.

The power gear housing support 50 is bolted to the housing 46. A planetary reduction gear assembly 54 is located within the support 50. It includes a ring gear 56 connected to the neutral clutch output sleeve 1 6.

sun gear 58, which is splined to disc clutch cylinder 60 and planet pinions 62, mesh with ring gear 56 and sun gear 58. Pinions 62 are carried by carrier 64 which is splined to power gear output shaft 66.

The clutch cylinder 60 and sun gear 58 can be braked by multiple disc brakes 68. This includes brake discs carried by the clutch member 60 which are clamped into braking engagement with brake ring 70 when fluid pressure is applied behind annular piston 72.

The end of the piston 72 cooperates with the housing support 50 to define a pressure chamber 74 to which pressure may be admitted when brake application is desired.

A multiple disc clutch asembly 76 is adapted to connect the clutch cylinder 60 with the carrier 76 when fluid pressure is admitted behind annular piston 78. This piston cooperates with cylinder 60 to define a pressure cavity 80 to which pressure may be admitted when clutch application is desired.

The clutch piston 78 normally is urged to a clutch release position by clutch piston return spring 82.

When the brake shown in part at 68 is applied, the planetary reduction gear unit provides an increased torque ratio as the sun gear 58 serves as a reaction member. When the brake 68 is released and the clutch shown in part at 76 is applied, the elements of the planetary gear system 54 are locked together and a 1:1 driving relationship exists between sleeve 16 and power gear output sleeve 66.

As swwn in Fig. 1, power input sleeve shaft 86 serves as a torque input element for the multiple ratio gear system. Sleve shaft 86 is splined by means of internal spline teeth 88 to external spline teeth on the sleeve shaft 66.

A power takeoff shaft 44 extends through the sleeve 86, and its right-hand end is journalled in bearing 90 in a bearing opening formed in end plate 92 secured to the main transmission housing 94. The end of the power takeoff shaft 44 extends outwardly, as shown at 96, to permit a driving connection with tractor power implements.

Sleeve shaft 86 is journalled at its righthand end by needle bearings 98 which are supported by bearing race 100 which, in turn, is journalled by bearings 102 and bearing support wall 104 of the housing 94. The lefthand end of the sleeve shaft 86 is journalled by tapered roller thrust bearings 106 in bearing wall 108 carried by another internal bearing support wall 110 of the housing 94.

A first torque input gear 11 2 is supported on the sleeve shaft 86. A second torque input gear 114 is formed on or supported by sleeve 116. Gear 114 is part of a cluster gear which includes also gear 11 8. Sleeve 11 6 is supported on the sleeve 86 by needle bearings 120 and 122.

A double acting synchronizer clutch assembly 1 24 is adapted to connect selectively sleeve shaft 86 with either one or the other of the gears 11 2 or 114. The clutch assembly 1 24 includes a hub 126 which is externally splined to an axially movable internally splined clutch actuator 1 28. When the actuator 1 28 is moved in a lefthand direction, the internal spline teeth formed in it drivably engage external spline teeth 1 30 formed on the gear 11 2. When it is shifted in a righthand direction, as seen in Fig. 1 it drivably engages external splines 1 32 formed on the gear 114.Cone clutch elements 1 34 and 1 36 are carried respectively by the gears 12 and 114 and rotate with them. Internal cone clutch surfaces are formed in clutch elements 1 34 and 1 36 which are adapted to engage external cone clutch surfaces formed on clutch elements 138 and 140. Elements 138 and 140 are connected together by cross shafts 142.The shafts 142 are formed with cam grooves which register with openings 144 in the clutch actuator 1 28 when the rotation of the hub 1 26 is out of synchronism with one gear or the other depending upon the direction of movement of the actuator 1 28. The calmed edges of the groove in the shafts 142 will register with corresponding cam surfaces on the margins of the openings 144 thereby creating a cone clutch engaging force that tends to force one gear or the other to rotate in synchronism with the hub 1 26. After synchronism is established, thee actuator 1 28 can be moved in a righthand direction or a lefthand direction depending upon the speed ratio that is desired.

A countershaft 146 is mounted in the transmission assembly in parallel disposition with respect to the shaft 44 and is journalleld at its lefthand end in bearing 148 formed in a bearing opening in a bearing support wall 1 50 which is joined to the transmission housing 94. The righthand end of the shaft 1 46 is supported by bearing 1 52 in a bearing opening formed in the previously described transmission bearing support wall 1 04.

A cluster gear assembly 1 54 is journalled on the countershaft 146 by bearings 1 56 and 1 58. It includes the first gear element 1 60 and a second gear element 1 62 which respectively engage the gears 11 2 and 11 4. Also supported by the countershaft 1 46 is drive gear 1 62 which meshes with gear 11 8.

The countershaft 146 and the hub 166 are splined at 168. Hub 166 forms a part of a second synchronizer clutch assembly 170, which is substantially the same construction as the previously described synchronizer clutch assembly 1 24. The synchronizer clutch assembly 1 70 includes an actuator 1 72 which can be shifted in the lefthand direction or the righthand direction depending upon the ratio that is desired.When it is shifted in the lefthand direction, clutching engagement occurs between the internal splines 1 74 carried by the cluster gear assembly 1 54. When the actuator 1 74 is shifted in the righthand direction, it engages drivably external splines 1 76 carried by the gear 1 64.

Countershaft 1 46 carries at its righthand end drive gear 1 78 which meshes with larger diameter drive gear 1 80. This gear 1 80 forms a part of an output cluster gear assembly 182, which is journalled at its righthand end by bearing 1 84 supported in the bearing opening formed in bearing support 92. The lefthand end is supported by the bearing 102 previously described, the bearing race 100 being formed as a part of the cluster gear assembly 182.

Cluster gear assembly 1 82 includes also the reverse drive gear 1 86 and a low drive gear 188, the latter meshing with low drive range output gear 1 90 rotatably supported on output shaft 1 92. The shaft 192 is journalled at its righthand end by bearing 1 94 positioned in bearing support 196, and its lefthand end is journalled in bearing 1 98 in bearing recess formed in the righthand end of the countershaft 146.

A reverse drive range gear 200 is rotatably supported on the shaft 192. It is adapted to engage a reverse drive pinion, not shown, which in turn engages the reverse gear 186.

A reverse-and-low clutch sleeve 202 is slidably supported and drivably connected to clutch hub 204 on the output shaft 1 92. It may be shifted in a righthand direction to drivably engage external clutch teeth 206 carried by the gear 1 90 to establish a low drive range. It can be shifted in a lefthand direction to drivably engage external clutch teeth 208 formed on reverse drive range gear 200.

Clutch hub 210 carries a second internally splined clutch sleeve 21 2 which is adapted to drivably engage external clutch teeth 214 on gear 1 78 when it is shifted in a lefthand direction thereby establishing a direct connection between shaft 146 and output shaft 192.

This would correspond to the high drive range position. When the sleeve 212 is moved to the position shown in Fig. 1, the transmission may be conditioned for low drive range operation provided the sleeve 202 also is shifted in a righthand direction.

In Fig. 2 there is shown the gear shift linkage motion pattern for a shift linkage that would be adapted for controlling the synchronizer clutches of Fig. 1. It forms generally an "H" pattern. The line 216 is the line of motion for the actuator 1 28 for the synchronizer assembly 124. Line 218 is the line of motion for actuator 1 72 of the synchronizer clutch assembly 1 70.

To establish low speed ratio operation the actuator 1 28 is shifted in a lefthand direction, and the actuator 1 72 of the clutch assembly 1 70 is shifted in a righthand direction. Both synchronizers must be engaged to effect a complete torque flow path through the gearing. When the synchronizers are engaged in this fashion, torque is delivered from the output element of the power drive unit of Fig.

3 and through the synchronizer clutch hub 1 28 and then is distributed to gear 11 2. This drives the cluster gear assembly 1 54. Torque then is transferred directly from the cluster gear assembly 1 54 through the engaged clutch teeth 1 74 and the actuator 1 72 to the countershaft 146. If it is assumed that the sleeve 212 is shifted in a lefthand direction, torque is distributed then directly to the output shaft 1 92 from the countershaft 146.

A ratio change from the first speed ratio to the second speed ratio requires actuation only of one synchronizer clutch assembly; namely, synchronizer clutch assembly 1 24. The other synchronizer clutch assembly remains in the position it assumed during first speed ratio operation. Actuator 1 28 is shifted in a righthand direction thereby establishing a driving connection between the hub 1 26 and the gear 114. The same torque flow path exists although the driving gear now is gear 114 rather than gear 112. Thus the overall ratio is increased because of the larger pitch diameter of the gear 114.

A speed ratio change from the second speed ratio to the third speed ratio requires actuation of both synchronizer clutches. After initiation of this speed change, synchronizer clutch assembly 1 24 is moved to the neutral position shown in Fig. 1; and synchronizer clutch assembly 1 70 is shifted in a righthand direction thereby establishing a connection between the countershaft 146 and the gear 1 64. After this shift is completed, synchronizer clutch assembly 1 24 is shifted in a lefthand direction thereby again connecting drivably gear 11 2 to the torque input sleeve shaft 86.During that ratio change the synchronizer clutch aassembly 1 70 establishes synchronism in the torque delivery elements while the mass associated with the power gear and the input clutch of Fig. 4 is disconnected from the rotating mass. Thus synchronization occurs relatively easily. The same reduced inertia shift occurs when the transmission mechanism shifts to a lower ratio; namely, from the third ratio to the second ratio. In that case the synchronizer clutch assembly 1 24 is moved initially to the neutral position, thereby disconnecting the rotating masses on the torque input side of the sleeve shaft 86 as the synchronizer clutch 1 70 again establishes a synchronized driving connection between the countershaft 146 and the cluster gear assembly 1 54.

A ratio change from a third ratio to a highspeed, fourth driving ratio is achieved by maintaining the synchronizer clutch assembly 1 70 in a lefthand position, which it assumes during third-speed ratio operation. Thus it is necessary to actuate only one synchronizer clutch assembly; namely, synchronizer clutch assembly 1 24. This is done by moving the actuator ring 1 28 in a righthand direction to establish a driving connection between the sleeve shaft 86 and the gear 11 4. Torque is then delivered from the input shaft to the gear 114 and hence to the gear 162. Torque is delivered then to the engaged clutch 1 70 to the countershaft 146 and then to the output shaft.

The final drive gear assembly found in the previously described patent for example, is capable of establishing either a high drive range or a low drive range depending upon the position of the sleeves 212 and 202.

During the previous description it has been assumed that the final drive gearing assembly of Fig. 1 is in the high speed drive range.

However, if the sleeve 212 is shifted in a righthand direction and the sleeve 202 is shifted in a righthand direction, and additional torque multiplication occurs because the gear 1 78 now becomes connected to the cluster gear assembly 1 82 of which gear 1 88 is a part. Gear 1 88 drives gear 1 90 which, in turn, is connected through the sleeve 202 to the output shaft 1 92.

Reverse drive is achieved by moving the sleeve 202 in a lefthand direction to establish a driving connection between the reverse gear 200 and the output shaft 1 92 as the low speed drive gear is connected.

Claims (5)

1. A transmission assembly comprising a power input shaft and a countershaft arranged in parallel disposition, a ffirst input gear jour nalled for rotation about the input shaft, second and third input gears connected together and mounted for rotation about the input shaft, first, second and third driving gears mounted for rotation about the countershaft, said first and second driving gears being connected together, first synchronizer clutch means connected drivably to said input shaft for connecting together selectively said input shaft and said first and second input gears, second synchronizer clutch means carried by said countershaft for connecting together selectively said countershaft and said second and third driving gears, an output shaft and final drive means for connecting said countershaft to said output shaft, said first input gear being connected to said input shaft by said first clutch means during first and third speed ratio operation and said second input gear being connected to said input shaft by said first clutch means during second and fourth speed ratio operation, said third driving gear being connected to said countershaft by said second synchronizer clutch means during first and second speed operation and said second driving gear being connected to said countershaft by said second synchronizer clutch means during third and fourth speed operation.

2. An assembly according to Claim 1 wherein said second and third input gears form a first cluster gear assembly and said first and second driving gears form a second cluster gear assembly, said first synchronizer clutch means being disposed between said first gear and said second input gears and said second synchronizer clutch means being disposed between said second driving gear aand said third driving gear.

3. An assembly according to Claim 1 wherein said final drive means comprises a third cluster gear assembly mounted for rotation about the axis of said input shaft and output gear mounted for rotation about the axis of said countershaft and first and second final drive output gears, said first final drive output gear being connected to said countershaft, each final drive output gear meshing drivably with a separate gear element of said third cluster gear assembly.

4. An assembly according to Claim 1 wherein said final drive means comprises a third cluster gear assembly mounted for rotation about the axis of said input shaft and output gear mounted for rotation about the axis of said countershaft and first and second final drive output gears, said first final drive output gear being connected to said countershaft, each final drive output gear meshing drivably with a separate gear element of said third cluster gear assembly.

5. A transmission assembly substantially as hereinbefore described, and as illustrated in the drawings.