GB2391592A

GB2391592A - A synchromesh with a conical ring biased away from engagement

Info

Publication number: GB2391592A
Application number: GB0315533A
Authority: GB
Inventors: Dennis James Redmond
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2002-07-17
Filing date: 2003-07-03
Publication date: 2004-02-11
Anticipated expiration: 2023-07-03
Also published as: GB0315533D0; GB0216591D0; GB2391592B

Abstract

A synchromesh, for a constant mesh gearbox, comprises a plurality of nestled together conical rings 51-53 arranged coaxially with a gear wheel 21 rotatably mounted on a gear shaft 13. The gear wheel 21 is coupled to the shaft 13 via a coupler 32 which is rotationally fast with the shaft 13. An inner conical ring 51 is biased away from a co-operating male cone 44 on the gear wheel 13 by a spring 64, eg a wavy spring. In use, the spring 64 bias must be overcome before the inner conical ring 51 frictionally engages the male cone 44, this prevents snicking an grating which may be experience by a driver. The rings 51-53 also comprise an intermediate ring 52 rotationally fixed to the male cone 44 and an outer ring 51 rotationally fast with the inner ring 53 and connected with limited angular rotation to the coupler 32.

Description

1 2391592

Synchromesh Device for a Gear Box Field This invention relates to gearboxes and in particular to gear boxes for motor vehicles.

Background of the Invention

The invention relates to multi-ratio gear boxes which are used on motor vehicles and in particular to manually operated gear boxes having synchromesh devices which are 10 used to simplify the change gear operation.

In some applications, a manually operated constant mesh gearbox may be provided with a synchromesh device comprising three pairs of conical surfaces which provides 15 a very powerful synchromesh device for fast changes during high torque transmission. However, during slow, or light gear changes which for example, may occur in heavy traffic, the driver may experience some feedback from the synchromesh through the gear lever. This feedback may 20 experienced by the driver as "sticking and grating" sensations and is due to very efficient workings of the triple cone synchromesh device. Such sensations are not in themselves damaging to the gearbox but may give rise some complains by vehicle divers.

It is the object of the present invention to provide a gear box triple cone synchromesh for change gear operations in which the above problems have been

l ameliorated. Statement of Invention

According to the present invention there is provided in a gear box, a synchromesh device comprising a plurality of 5 nestled together conical rings operable between a gear wheel rotatably mounted on a gear shaft and a synchronizer assembly rotationally fast with said shaft, characterized in that the inner of said rings is resiliently biased away from a cooperating male cone on the gear wheel, said bias 10 being overcome before the inner cone frictionally engages the male cone.

Preferably the synchromesh device has three conical rings, an inner ring rotatable relative to the male cone, an 15 intermediate ring rotationally fast with the male cone, and an outer ring rotational fast with the inner ring and connected to the synchronizer assembly. The outer of said rings is capable of limited angular rotation relative to the synchronizer assembly.

The inner cone is preferably resiliently biased from the male cone fly a coaxial annular spring located between the gear wheel and inner ring. The annular spring may be any suitable form of spring such as a wavy spring and 25 Belleville spring.

Also according to the present invention there is provided a motor vehicle constant mesh gearbox having a synchromesh

( device as described herein.

In a gear box having a synchromesh device comprising a plurality of nestled together conical rings arranged coaxially with a gear wheel rotatably mounted on a gear 5 shaft and a synchronizer assembly rotationally fast with said shaft, the invention also provides a method of engagement between the inner of said rings and a cooperating male cone on the gear wheel, wherein the inner ring is resiliently biased away from the male cone and 10 said bias is overcome before the surfaces on the inner cone frictionally engage like surfaces on the male cone.

Preferably, the inner ring is biased away from the male cone by a coaxial annular spring which reacts against an 15 annular flat face is provided on the gear wheel.

Description of the Drawings

The present invention will be described by way of Example and by reference to the accompanying drawings in which: 20 Fig. 1 is a longitudinal section through a gear box for a motor vehicle and which is in accordance with the present invention, and Fig. 2 is an enlarged portion of Fig.1 showing the synchromesh device located between a synchronizer assembly 25 and gear wheel.

Detailed Description of the Invention

With reference to Fig 1, there is shown a multi-ratio

( gearbox 10 for a motor vehicle, The gearbox 10 shown is a constant-mesh gearbox having the conventional gearbox input shaft 11 which is connected to a clutch driven plate (not shown)' a layshaft 12 off-set from the input shaft, 5 and main shaft 13, arranged coaxially of the input shaft.

The overall operation of the gear box is conventional and the gear arrangenent and gear change mechanisms form no part of the present invention and will not be described in lo detail.

The input shaft ll is integrally formed with a pinion 14 which meshes with a pinion 15 formed integrally with the one end portion of the layshaft 12. The layshaft 12 is 15 rotatably supported in the gearbox housing 18 and is constantly driven by the input shaft 11. An oil pump 16 is supported in a wall 17 of the gearbox housing 18 and is driven by the other end of the layshaft 12. The oil pump typically supplies oil to the main shaft 13 and to gear 20 wheels 21-25 mounted on the main shaft. The layshaft 12 has further pinions 26, 27 30 formed integrally on the shaft and has a splined outer surface 28 at its other end portion. A pair of gear wheels 29,31 have inner xplined surfaces which are engageable with like splines 28 on the 25 layshaft 12. In this instance the gear wheels are a reverse gear wheel 29 and 5th gear 31.

The different gear ratios are selected through operation of synchronizer assemblies 32,33,34. The synchr-oniser

assemblies 32-34 each include a respective synchroniser sleeve 38-41 and respective hub which is rigidly mounted on the mainshaft 13 and is made rotationally fast therewith. Each annular synchroniser sleeve 38-41 is 5 slidably mounted for axial movement on its respective hub and is rotationally fast therewith. The synchroniser sleeves 38-41 are moved axially by respective selector forks 35-37 and each synchroniser assembly 32-34 is operable between respective pair of gear wheels 14 & 21, 10 22 & 23, and 24 & 25 to make one gear wheel of said pairs rotationally fast with the shaft 13.

Each sleeve 38-41 has an annular array of axial splines in its inner surface that engage like-splines on the outer 15 surface of the respective hub and which are also engageable with dog teeth on the respective pairs of gear wheel. The sleeves 38-41 are axially slidable within the respective synchroniser assembly 32-36 to lock one of the pair of gear wheels to said synchroniser assembly as is 20 known in the art.

Referring also to Fig.2, there is shown in enlarged section the third gear wheel 21, fourth gear pinion 14, and respective synchroniser assembly 32. The gear wheel 2S 21 has dog teeth 45 forming a gear dog ring around its outer peripheral margin facing the synchroniser assembly 32. The inner peripheral margin of the gear wheel 21 has a male cone 44 formed thereon extending towards the

synchronizer assembly 32 with a conical outer surface 46.

A synchromesh device 50 is located on the male cone 44 and comprises a three synchromesh cones 51-53 which nestle 5 together coaxially of the gear wheel 21 having matching conical surfaces. The inner cone 51 is formed from brass and has conical inner surface which is frictionally engageable with the opposed surface 46 on the gear wheel 21. The intermediate ring 52 is formed from steel and has 10 conical surfaces that are frictionally engageable with opposed surfaces on the other two rings. The outer ring 53 is also formed from brass and has a conical inner surface that frictionally engages the opposed surface on the intermediate ring 52.

The inner ring 51 is free to rotate about the male cone 44 and has lugs 54 on its outer periphery that engage with notches 55 in the outer ring 53 so that the inner and outer rings 51 & 53 are rotationally fast with each other.

20 The intermediate ring 52 has lugs 56 on its inner periphery that engage in notches 57 in the end of the cone 44 on the gear wheel making the intermediate ring 52 rotationally fast with the gear wheel 21. The outer ring 53 has teeth 58 on its outer periphery that match with the 25 teeth 45 on the gear wheel 21. The ring 53 is also provided with three circumferentially spaced raised abutments ( not shown) and three circumferentially spaced notches 59 on its radially outer surface. The abutments

( engage in cooperating apertures and the notches 59 accommodate axial struts 62 all located in the outer peripheral margin of the synchronizer assembly hub. The abutments and struts 62 are loosely accommodated in the 5 co-operating apertures so that there is a small amount of circumferential play to allow for alignment of the teeth 58 with the teeth 45, as is known in the art.

The gearwheel 21 is provided with a flat annular face 63, 10 which may be machined flat, opposite to the inner ring 51.

A coaxial annular spring 64 is located around the cone 44 between the annular face 63 and the ring 51 to bias the ring 51 away from the cone 44. The spring 64 may be any suitable spring, preferably a spring steel wavy washer, or 15 Belleville spring and reacts against the face 63 to bias the ring 51 away from the gear wheel 21.

In use when changing gear, in this example changing into third gear, the synchronizer sleeve 38 moves axially 20 towards the gear wheel 21. The three rings 51,52,53 are pushed together and the opposed conical surfaces between the rings begin to frictional engage with each other. The spring 64 prevents full frictional engagement between the rings and the gear until the bias in the spring 64 has 25 been overcome. The synchromesh device 50 may allow the sleeve 38 to slide over the teeth 58 and 45 to connect the gear wheel 21 rotationally fast with the shaft 13, whether or not the inner ring 51 is fully engaged with the cone

44. The full engagement will occur during fast high: torque gear changes, but not necessarily during slow, low torque changes.

Claims

1. In a gear box, a synchromesh device comprising a plurality of nestled together conical rings arranged coaxially with a gear wheel rotatably mounted on a gear 5 shaft and a synchroniser assembly rotationally fast with said shaft, characterized in that the inner of said rings is biased away from a co-operating male cone on the gear wheel, said bias being overcome before the inner conical ring frictionally engages the male cone.

2. A synchromesh device as claimed in Claim 1 comprising three conical rings, an inner ring rotatable relative to the male cone, an intermediate ring rotationally fixed relative to the mate cone and an outer ring rotationally 15 fast with the inner ring and connected to the synchronizer assembly.

3. A synchromesh device as claimed in Claim 1 or Claim 2 having the outer of said rings is capable of limited 20 angular rotation relative to the synchronizer assembly.

4. synchromesh device as claimed in any one of Claims 1 to 3 wherein inner cone is resiliently biased from the male cone by a coaxial annular spring located between the 25 gear wheel and inner ring.

5. A synchromesh device as claimed in Claim 4 wherein the annular spring is a wavy spring.

6. A synchromesh device substantially as described herein and with reference to the accompanying drawings.

5

7. A synchromesh device for a motor vehicle gear box and which is substantially as described herein.

8. A motor vehicle constant mesh gear box having a synchromesh device as claimed in any one of Claims 1 to 7.

9. In a gear box having a synchromesh device comprising a plurality of nestled together conical rings arranged coaxially with a gear wheel rotatably mounted on a gear shaft and a synchronizer assembly rotationally fast with 15 said shaft, there is provided a method of engagement between the inner of said rings and a cooperating male cone on the gear wheel, wherein the inner ring is biased away from the male cone and said bias is overcome before the surfaces on the inner cone frictionally engage like 20 surfaces on the male cone.

10. A method as claimed in Claim 9 wherein the inner ring is biased away from the male cone by a coaxial annular spring which reacts against an annular flat face is 25 provided on the gear wheel.