WO2015063450A2

WO2015063450A2 - Switching assembly for dual speed final drive

Info

Publication number: WO2015063450A2
Application number: PCT/GB2014/052719
Authority: WO
Inventors: Christopher Smith
Original assignee: Caterpillar Shrewsbury Ltd
Current assignee: Caterpillar Shrewsbury Ltd
Priority date: 2013-10-30
Filing date: 2014-09-09
Publication date: 2015-05-07
Anticipated expiration: 2016-04-30
Also published as: GB2519949A; GB201319146D0; WO2015063450A3

Abstract

The present disclosure relates to a switching assembly (138) for a dual speed final drive (100). Conventionally, the dual speed final drives include a switching assembly external to the to the dual speed final drive. However, the switching assembly (138) of the present disclosure is integral to the dual speed final drive (100) and also includes a locking assembly (196) to lock the dual speed final drive (100).

Description

SWITCHING ASSEMBLY FOR DUAL SPEED FINAL DRIVE Technical Field

[0001] Present disclosure relates to a dual speed final drive for a machine and more particularly to a switching assembly for the dual speed final drive.

Background

[0002] A final drive in a machine is configured to provide multiple speed ranges to assist the machine during various operations such as normal driving, digging, loading etc. Further, the machines have a gear selector to select one of the multiple speed ranges in the final drive assembly. For example, in a low speed range operation of the final drive, the machine travels at slow speed with high torque, which is required during, digging, earth moving, and the like. Alternatively, in a high speed range operation of the final drive assembly, the machine travels at higher speed, which is required during a normal driving or cruising.

[0003] A typical final drive assembly includes a pair of coupled epicyclic gear sets to selectively engage the final drive in one of the multiple speed ranges. Further, a switching assembly is provided to switch between the multiple speed ranges by engaging one or both of the epicyclic gear sets. The switching assembly is provided external to the final drives and operatively coupled to the epicyclic gear sets via a complex mechanism.

Summary

[0004] In one aspect, the present disclosure provides a switching assembly for a dual speed final drive. The dual speed final drive includes a drive shaft, a first epicyclic gear set, a second epicyclic gear set, and a driven shaft. The switching assembly includes a sleeve assembly movable between a first position and a second position corresponding to a high-speed range and a low-speed range of the dual speed final drive, respectively. The switching assembly further includes a groove disposed on a circumferential face of the sleeve assembly. The switching assembly further includes a displacement member disposed at least partway around the sleeve assembly. The displacement member having a follower and a first toothed portion, the follower being received in the groove on the circumferential face of the sleeve assembly. The switching assembly further includes an actuation means comprises a second toothed portion engaged with the first toothed portion of the displacement member.

[0005] In another aspect, the present disclosure provides a dual speed final drive for a machine. The dual speed final drive includes a first epicyclic gear set, and a second epicyclic gear set coupled to the first epicyclic gear set. The dual speed final drive further includes a drive shaft engaged to the first epicyclic gear set and a driven shaft engaged to the first epicyclic gear set. The dual speed final drive further includes a switching assembly configured to selectively operate the dual speed final drive in a high-speed range and a low-speed range. The switching assembly includes a sleeve assembly movable between a first position and a second position corresponding to the high-speed range and the low-speed range of the dual speed final drive, respectively. The switching assembly further includes a groove disposed on a circumferential face of the sleeve assembly. The switching assembly further includes a displacement member disposed at least partway around the sleeve assembly. The displacement member having a follower and a first toothed portion, the follower being received in the groove on the circumferential face of the sleeve assembly. The switching assembly further includes an actuation means comprises a second toothed portion engaged with the first toothed portion of the displacement member. The switching assembly further includes a locking assembly configured to lock the sleeve assembly in at least one of the first position and the second position.

[0006] Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

Brief Description of the Drawings

[0007] Figure 1 illustrates a schematic view of a dual final drive;

[0008] Figure 2 illustrates an exemplary front side view of the dual speed final drive;

[0009] Figure 3 illustrates a detailed view of a portion of a switching assembly of Figure 2;

[0010] Figure 4 illustrates an exemplary front side view of the dual speed final drive in the high mode of operation of the dual final drive; [0011] Figure 5 illustrates an exemplary front side view of the dual speed final drive in the low mode of operation of the dual final drive; and

[0012] Figure 6 illustrates an exemplary front side view of the dual speed final drive in the neutral mode of operation of the dual final drive.

Detailed Description

[0013] Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding or similar reference numbers will be used, when possible, to refer to the same or corresponding parts.

[0014] The present disclosure relates to a final drive of a machine, and more particularly to a dual speed final drive configured to operate the machine in a high-speed range and a low-speed range of operation. Figure 1 illustrates a schematic of an exemplary dual speed final drive 100, according to an embodiment of the present disclosure. The dual speed final drive 100 includes a coupled epicyclic gear set 102 disposed within an enclosure 104. The coupled epicyclic gear set 102 includes a first epicyclic gear set 106 and a second epicyclic gear set 108.

[0015] The first epicyclic gear set 106 includes a rotatable first sun gear 110, a plurality of first planet gears 112, a first planet carrier 114, and a first planet gears annulus 116. The first planet carrier 114 is attached to the first planet gears 112 which are engaged to rotate with the first sun gear 110. Further, the first planet gears annulus 116 rotatably supports the first planet gears 112 in the first epicyclic gear set 106. Similarly, the second epicyclic gear set 108 includes a rotatable second sun gear 118, a plurality of second planet gears 120, a second planet carrier 122, and a second planet gears annulus 124. The second planet carrier 122 is attached to the second planet gears 120 which are engaged to rotate with the second sun gear 118. The second planet carrier 122 is rigidly attached to the enclosure 104. Further, the second planet gears annulus 124 rotatably supports the second planet gears 120 in the second epicyclic gear set 108. As illustrated in Figure 1, the first planet gears annulus 116 is rotatably engaged with the second sun gear 118 to form the coupled epicyclic gear set 102. In an embodiment, the first epicyclic gear set 106 and the second epicyclic gear set 108 have different gear ratios.

[0016] The enclosure 104 includes a face plate 126 and a back plate 128. The face plate 126 includes a drive shaft opening 130 to receive a drive shaft 132 therein. The drive shaft 132 may be an engine output shaft, a transmission output shaft, or a torque converter output shaft and engaged to the first sun gear 110 of the first epicyclic gear set 106. The back plate 128 includes a driven shaft opening 134 to receive a driven shaft 136 therein. The driven shaft 136 may be a differential input shaft and the like and engaged to the first planet carrier 114.

[0017] According to an embodiment of the present disclosure, the dual speed final drive 100 includes a switching assembly 138 to selectively operate the dual speed final drive 100 in a high-speed range and a low-speed range. The switching assembly 138 includes a sleeve assembly 140. The sleeve assembly 140 is hydraulically controlled and movable between a first position (shown in Figure 1) and a second position (not shown). During the high-speed range of operation of the dual speed final drive 100, the sleeve assembly 140 is positioned in the first position to provide an output at the driven shaft 136 through the first epicyclic gear set 106 only. During the low-speed range of operation of the dual speed final drive 100, the sleeve assembly 140 is positioned in the second position to provide the output at the driven shaft 136 through the first epicyclic gear set 106 and the second epicyclic gear set 108 together. Various details of the switching assembly 138, according to various embodiments of the present disclosure, are now described in conjunction with Figures 2 to 6.

[0018] Figure 2 illustrates an exemplary front side view of the dual speed final drive 100. As illustrated, a front cover of the dual speed final drive 100 is removed to illustrate the switching assembly 138. The switching assembly 138 is mounted on the face plate 126 such that the sleeve assembly 140 is disposed in the drive shaft opening 130 of the face plate 126. In an embodiment, as illustrated in detailed view in Figure 2, the sleeve assembly 140 may include a first sleeve 142 and a second sleeve 144. The first sleeve 142 includes splines 146 on an inner face 148 and an outer face 150 of the first sleeve 142. The sleeve assembly 140 may further include a split bearing 152. The split bearing 152 is configured to couple the first sleeve 142 to the second sleeve 144. The second sleeve 144 includes a circumferential face 154. In an embodiment, the circumferential face 154 may include one or more grooves 156 which may be at least partially helical, and key-ways 158 disposed thereon. As illustrated in Figure 2, the switching assembly 138 further includes a rotation member 160. In an embodiment, the rotation member 160 is a key-plate and includes keys 162 corresponding to the key-ways 158 on the second sleeve 144. The keys 162 on the rotation member 160 are engaged with the key- ways 158 provided on the second sleeve 144.

[0019] According to an embodiment of the present disclosure, the switching assembly 138 further includes an actuation means 164 configured to axially move the sleeve assembly 140 between the first position and the second position. In an aspect of the present disclosure, the actuation means 164 is a fixed-piston and movable-cylinder type actuation means. The actuation means 164 includes a first piston 166 and a second piston 168 disposed at opposite ends of a movable- cylinder 170. In an embodiment, the actuation means 164 includes a second toothed portion 172 attached to a first surface 174 of the movable-cylinder 170. The first piston 166 and the second piston 168 are rigidly attached to the face plate 126 through a first set of fasteners 176 and a second set of fasteners 178 respectively. Alternatively, in other embodiments, the actuation means 164 may include only one fixed-piston received in the movable-cylinder and the fixed- piston rigidly attached to the face plate 126.

[0020] In an embodiment, the switching assembly 138 includes a valve assembly 180 attached to the face plate 126. The valve assembly 180 may be hydraulically and/or electronically coupled to one or more interface devices (not shown) located in an operator station of the machine. In an embodiment, the operator interface devices may include a parking brake, a selector switch, and the like. The valve assembly 180 includes a first fluid valve 182, and a second fluid valve 184. As shown in Figure 2, the first piston 166 and the second piston 168 are fluidly coupled to the first fluid valve 182 through a first fluid line 186 and a second fluid line 188, respectively. [0021] Figure 3 illustrates a detailed view of a portion of the switching assembly 138 of Figure 2. In an embodiment, the switching assembly 138 includes a displacement member 190 disposed around the sleeve assembly 140 (see Figure 2) and includes followers 192. The followers 192 are slidably received within the grooves 156 of the second sleeve 144 (see Figure 2). In an embodiment as shown in Figure 3, the displacement member 190 further includes a first toothed portion 194. The first toothed portion 194 is engaged with the second toothed portion 172 provided on the movable-cylinder 170 to form a rack and pinion arrangement.

[0022] In an embodiment, the switching assembly 138 further includes a locking assembly 196. The locking assembly 196 includes a locking plate 198. The locking plate 198 is attached to a second surface 200 of the movable-cylinder 170 and extends therefrom. The locking plate 198 includes a hole 202 therein. As shown in Figure 2, the locking plate 198 includes a first end 204 and a second end 206. In an embodiment, the locking assembly 196 includes a housing 208. The housing 208 is hydraulically coupled to the second fluid valve 184, through a third fluid line 210. A locking member 212 extends from the housing 208 towards the locking plate 198. The locking member 212 is movable between an extended position and a retracted position. A hydraulic pressure from the second fluid valve 184 may bias the locking member 212 in the extended position. The housing 208 may further include a spring 214 operably coupled to the locking member 212 and configured to bias the locking member 212 in the retracted position.

[0023] In an embodiment, the switching assembly 138 is configured to switch the dual speed final drive 100 into a high-speed range, a neutral- speed range, and a low-speed range. The high-speed range disclosed herein refers to an operation of the machine while travelling on-road and off-road, and the low-speed range disclosed herein refers to operation of the machine while performing operations such as digging, earth moving and the like. In neutral-speed range no torque is transmitted from the dual speed final drive 100 to the machine. Hence in an exemplary embodiment, the neutral- speed range may be engaged when the machine is receiving torque/power from external sources such as but not limited to an exemplary situation of towing of the machine through a tow vehicle.

[0024] In an aspect of the present disclosure, the first fluid valve 182 is configured to selectively supply a fluid to the actuation means 164 to selectively move the movable-cylinder 170 to move the second toothed portion 172 and the locking plate 198 attached thereto. In an embodiment, the movable-cylinder 170 is selectively movable between a high-speed position, a neutral-speed position, and a low-speed position. In an exemplary embodiment, the high-speed position of the movable-cylinder 170 is indicative of a movement of the movable-cylinder 170 towards the first piston 166, and the low-speed position of the movable- cylinder 170 is indicative of the movement of the movable-cylinder 170 towards the second piston 168. The neutral-speed position of the movable-cylinder 170 is indicative of a position of the movable-cylinder 170 substantially midway to the first piston 166 and the second piston 168.

[0025] In an embodiment, movement of the second toothed portion 172 initiates a rotation in the displacement member 190 via the first toothed portion 194. The second sleeve 144 is restricted from a rotational movement due to the inter-engagement of the key 162 at the key- ways 158. During rotation of the displacement member 190, the followers 192 ride along the grooves 156 on the second sleeve 144 to axially move the sleeve assembly 140. Thus disposing the second sleeve 144 in the first position or the second position. In an exemplary embodiment, the high-speed range, the low-speed range and the neutral-speed range are selected by the positioning of the second sleeve 144 of the sleeve assembly 140. The high speed range, the low speed range and the neutral speed range at the driven shaft 136 are achieved though the first epicyclic gear set 106, both the first and second epicyclic gear sets 106, 108, and neither of the first or the second epicyclic gear sets 106, 108 respectively.

[0026] In an aspect of the present disclosure, the locking assembly 196 is configured to lock the switching assembly 138 in at least one of the high-speed range, the neutral-speed range and the low-speed range. The second fluid valve 184 is configured to selectively supply the fluid to the housing 208 of the locking assembly 196 to bias the locking member 212 into the extended position. In the extended position, the locking member 212 extends towards the locking plate 198 and may be received in the hole 202 of the locking plate 198, or abut the first end 204, or abut the second end 206 to restrict the movement of the locking plate 198 therefrom. Restricting the movement of the locking plate 198 locks the switching assembly 138 in the high-speed range, the neutral-speed range, or the low-speed range based on the position of the locking plate 198. The spring 214 is configured to bias the locking member 212 in the retracted position upon loss of fluid in the housing 208 such that the locking plate 198 is unlocked and the movable-cylinder 170 may be moved in any of the high-speed position, a neutral- speed position, and a low-speed position. The operator may then choose to operate the dual speed final drive 100 in any of the high-speed range, the neutral- speed range, and the low-speed range.

Industrial Applicability

[0027] The industrial applicability of the switching assembly 138 in the dual speed final drive 100 described herein will be readily appreciated from the foregoing discussion. In an embodiment, the dual speed final drive 100 may be used in a machine such as a wheeled or tracked military vehicle. Alternatively, the machine may be any wheeled or tracked machine that performs at least one operation associated with for example mining, construction, and other industrial applications, for example, backhoe loaders, skid steer loaders, wheel loaders, motor graders, tracked -type tractor, and many other machines.

[0028] For the operation of the dual speed final drive 100, the first fluid valve 182 and the second fluid valve 184 is hydraulically coupled to the selector switch and parking brake lever located in the operator cabin respectively. When the machine is not operating, there is a loss of hydraulic pressure in the actuation means 164, and the locking assembly 196. The locking member 212 associated with the locking assembly 196 is in the retracted position such that the actuation means 164 is movable in any of the high-speed range, the neutral-speed range, and the low-speed range.

[0029] Figure 4 illustrates an exemplary front side view of the dual speed final drive 100 in the high-speed range of the dual speed final drive 100. When the operator selects the high-speed range through the selector switch, the first fluid valve 182 supplies the fluid in the first fluid line 186. The first piston 166 receives the fluid from the first fluid line 186 and supplies the fluid into the movable-cylinder 170 initiating a movement of the movable-cylinder 170 along the first piston 166. Hence, the second toothed portion 172 and the locking plate 198 attached to the movable-cylinder 170 are displaced towards the first set of fasteners 176. The second toothed portion 172 rotates the first toothed portion 194 associated with the displacement member 190 in a clockwise direction. The followers 192 associated with the displacement member 190 traverse in the grooves 156 to displace the sleeve assembly 140 in the first position. The splines 146 on the outer face 150 of the first sleeve 142 are engaged with the second sun gear 118 and the second planet gears annulus 124 of the second epicyclic gear set 108. Therefore, the second epicyclic gear set 108 remains stationary and the torque/power is transmitted through the first epicyclic gear set 106 only. The operator may then release a parking brake by operating the parking brake lever. The second fluid valve 184 then supplies fluid to the housing 208 such that the locking member 212 is biased in the extended position to abut the first end 204 of the locking plate 198. As shown in Figure 4, the extended position of the locking member 212 restricts the movement of the locking plate 198 attached to the movable-cylinder 170 and locks the switching assembly 138 locking the dual speed final drive 100 in the high-speed range.

[0030] Figure 5 illustrates an exemplary front side view of the dual speed final drive 100 in the low-speed range of the dual speed final drive 100. When the operator selects low-speed range, the first fluid valve 182 supplies the fluid in the second fluid line 188. The second piston 168 receives the fluid from the second fluid line 188 and supplies the fluid into the movable-cylinder 170 initiating a movement of the movable-cylinder 170 along the second piston 168. Hence, the second toothed portion 172 and the locking plate 198 attached to the movable-cylinder 170 are displaced towards the second set of fasteners 178. The second toothed portion 172 rotates the first toothed portion 194 associated with the displacement member 190 in an anti-clockwise direction. The followers 192 associated with the displacement member 190 traverses in the grooves 156 to displace the sleeve assembly 140 in the second position. The splines 146 on the outer face 150 of the first sleeve 142 are engaged with the second planet gears annulus 124 of the second epicyclic gear set 108 and the splines 146 on the inner face 148 are engaged with the first planet carrier 114 of the first epicyclic gear set 106. Therefore, the torque/power is transmitted through both the first epicyclic gear set 106 and the second epicyclic gear set 108. The operator may then release the parking brake by operating the parking brake lever. The second fluid valve 184 then supplies fluid to the housing 208 such that the locking member 212 is biased in the extended position to abut the second end 206 of the locking plate 198. As shown in Figure 5, the extended position of the locking member 212 restricts the movement of the locking plate 198 attached to the movable-cylinder 170 and locks the switching assembly 138 locking the dual speed final drive 100 in the low-speed range.

[0031] Figure 6 illustrates an exemplary front side view of the dual speed final drive 100 in the neutral-speed range of the dual speed final drive 100. When the operator selects the neutral- speed range, the first fluid valve 182 supplies the fluid in both the first fluid line 186, and the second fluid line 188. The movable-cylinder 170 remains midway to the first piston 166 and the second piston 168. The splines 146 of the first sleeve 142 are disengaged from both the first epicyclic gear set 106 and the second epicyclic gear set 108. Therefore, no torque/power is transmitted through the coupled epicyclic gear set 102. The operator may then release the parking brake by operating the parking brake lever. The second fluid valve 184 then supplies fluid to the housing 208 such that the locking member 212 is biased in the extended position and located in the hole 202 disposed on the locking plate 198. As shown in Figure. 5, the extended position of the locking member 212 restricts the movement of the locking plate 198 attached to the movable-cylinder 170 and locks the switching assembly 138 locking the dual speed final drive 100 in the neutral- speed range.

[0032] From the foregoing it will be appreciated that, although specific embodiments have been described herein for purposes of illustration, various modifications or variations may be made without deviating from the spirit or scope of inventive features claimed herein. Other embodiments will be apparent to those skilled in the art from consideration of the specification and figures and practice of the arrangements disclosed herein. It is intended that the specification and disclosed examples be considered as exemplary only, with a true inventive scope and spirit being indicated by the following claims and their equivalents.

Claims

Claims What is claimed is

1. A switching assembly for a dual speed final drive having a drive shaft, a first epicyclic gear set, a second epicyclic gear set, and a driven shaft, the switching assembly comprising: a sleeve assembly movable between a first position and a second position corresponding to a high-speed range and a low- speed range of the dual speed final drive, respectively; a groove disposed on a circumferential face of the sleeve assembly; a displacement member disposed at least partway around the sleeve assembly and having a follower and a first toothed portion, the follower being received in the groove on the circumferential face of the sleeve assembly; and an actuation means including a second toothed portion engaged with a first toothed portion.

2. The switching assembly of claim 1, wherein the sleeve assembly includes: a first sleeve having splines on an inner face and an outer face; a second sleeve defining the circumferential face; and a split bearing coupling the first sleeve and the second sleeve.

3. The switching assembly of claim 1 further including at least one key-way disposed on the circumferential face of the sleeve assembly.

4. The switching assembly of claim 1 further including a valve

assembly, wherein the valve assembly including a first fluid valve and a second fluid valve.

5. The switching assembly of claim 4, wherein the valve assembly is fluidly coupled to the actuation assembly.

6. The switching assembly of claim 1, further including a rotation member configured to restrict rotational movement of the sleeve assembly relative to the switching assembly.

7. The switching assembly of claim 6, wherein the rotation member is a key-plate.

8. The switching assembly of claim 7, wherein the key-plate includes a key.

9. The switching assembly of claim 1, wherein the actuation means is a fixed-piston and a moving cylinder type actuation means, wherein the second toothed portion is defined on the moving cylinder.

10. The switching assembly of claim 1 further comprising a locking assembly configured to lock the sleeve assembly in at least one of the first position and the second position.

11. The switching assembly of claim 10, wherein the locking

assembly includes a locking plate.

12. The switching assembly of claim 11, wherein the locking plate including a hole therein.

13. The switching assembly of claim 12, wherein the locking

assembly comprises a locking member configured to lock the switching assembly in one of the high-speed range, the low-speed range and a neutral- speed range.

14. The switching assembly of claim 13, wherein the locking member is biased in an extended position to engage the locking plate and thus to lock the switching assembly in one of the high-speed range, the low-speed range and the neutral-speed range.

15. A dual speed final drive for a machine comprising: a first epicyclic gear set; a second epicyclic gear set coupled to the first epicyclic gear set; a drive shaft engaged to the first epicyclic gear set; a driven shaft engaged to the first epicyclic gear set; and a switching assembly configured to selectively operate the dual speed final drive in a high-speed range and a low-speed range, the switching assembly comprising: a sleeve assembly movable between a first position and a second position corresponding to a high-speed range and a low-speed range of the dual speed final drive, respectively; a groove disposed on a circumferential face of the sleeve assembly; a displacement member disposed around the sleeve assembly and having a follower and a first toothed portion, the follower received in the groove on the circumferential face of the sleeve assembly; a actuation means comprises a second toothed portion engaged with the first toothed portion of the displacement member; and a locking assembly configured to lock the sleeve assembly in at least one of the first position and the second position.