WO2005103520A1

WO2005103520A1 - Synchroniser

Info

Publication number: WO2005103520A1
Application number: PCT/GB2005/001502
Authority: WO
Inventors: Graeme Andrew Jackson
Original assignee: Eaton Corporation
Priority date: 2004-04-21
Filing date: 2005-04-19
Publication date: 2005-11-03
Also published as: GB0408808D0

Abstract

A synchroniser ring and method for the manufacture thereof for a multi-ratio transmission is described, the synchroniser ring being produced from tube by machining.

Description

SYNCHRONISER

The present invention relates to a synchroniser and synchroniser rings for transmissions.

Co-pending European patent application number 02749140.6 of common ownership herewith discloses a synchroniser assembly for a multi-ratio transmission. The content of EP 02749140.6 is incorporated herein by reference.

Synchronisers for use in multi-ratio transmissions are well known and may be of the single or double acting type. Generally, such synchronisers include: a pair of friction surfaces for each gear ratio in order to equalise the angular velocity of the required gear and that of the gearbox main/output shaft in response to an input by, for example, a driver moving a gear shift lever towards a desired gear; a shaft; a fixed hub member axially and rotationally fixed to the shaft, the hub member being generally annular and having axially directed splines teeth on the outer periphery thereof; a sliding shift sleeve having internal splines teeth which co-operate with and are slidable relative to the teeth of the fixed hub. The sliding shift sleeve may also incorporate a toothed annular member which eventually engages with co-operating teeth on the gear to be selected so as to couple the shaft and gear together. The synchroniser also includes baulking or blocking means whereby axial sliding of the shift sleeve is arrested until the angular velocities of the gear and the shaft are equalised.

The baulking or blocking means may be separate features formed on a synchroniser ring or may be included in mechanisms known as pre-energisers and/or self-energisers which, in effect, increase the force applied to the friction surfaces which bring the gear and shaft to a synchronous speed allowing the gear flange of the gear and the sliding sleeve to couple the gear to the shaft so that the gear cannot rotate relative to the shaft . An example of such a synchroniser arrangement is shown in EP-A-0 663 541, of common ownership herewith.

The pre-energiser generally works in co-operation with a synchroniser ring which possesses one of the pair of friction surfaces referred to above, the second friction surface being associated with the gear to be selected. The pre-energiser, self-energiser mechanisms are located by the fixed hub and by the sliding shift sleeve, the energiser mechanisms being permitted a limited degree of axial and rotational movement relative to the fixed hub and the sliding shift sleeve. The pre-energiser mechanism also locates the synchroniser ring in the rotational and axial directions and, apart from the same limited degree of movement in the rotational direction, constrains the synchroniser ring to move with the pre-energiser mechanism.

An improved example of a synchroniser assembly is described in WO 03/004892-A also of common ownership herewith.

In known synchroniser assemblies, each synchroniser ring is machined from a single, individual basic ring which is generally formed by casting or forging, for example. Such synchroniser rings are costly to produce as the basic cast or forged ring is expensive and the added value in the many diverse machining operations is considerable. Figure 11 which shows a perspective view of a prior art synchroniser ring produced -from a forged ring 200 which then requires complex and diverse processing operations to produce a synchroniser ring have closely controlled tolerances .

It is an object of the present invention to reduce the cost of manufacture of synchroniser assemblies.

According to a first aspect of the present invention there is provided a method for the production of an annular metal member for a synchroniser ring for a synchroniser assembly for a multi-ratio transmission characterised in that the annular member is formed by machining from a tubular member.

In this specification the terms "synchroniser ring", "baulk ring" are essentially synonymous.

The annular member of the present invention may also be machined on all surfaces thereof. Prior art synchroniser rings may generally possess surfaces which remain in the as-cast or as-forged condition, i.e. possess un-machined surfaces .

In the manufacture and machining of prior art cast or forged synchroniser rings much time and skilled expertise is expended in providing various complex features on the ring relating to the blocking and pre-energising functions, manufacturing tolerances for such features being very small and which features are not amenable by machining operations. However, in the present invention where the ring is machined from tube, the axis of rotation of the tube itself may provide the main datum from which all other dimensions may be largely automatically gauged, allowing machining to be used for the complex features. Thus, the machining process may be automated and the degree of skilled expertise by human intervention considerably reduced with consequent economic benefits .

More recently, synchroniser assemblies have incorporated the blocking function and pre-energising function together in a single unified mechanism which co-operates with the synchroniser ring where separate, circumferentially spaced-apart so-called blocking ramps, in addition to so-called pre-energising lugs, are no longer incorporated on the synchroniser ring per se but on separate components. Modern methods of production of complex components from metal powders have enabled the economic production and provision of many features of pre-energiser, self-energiser and blocker mechanisms to be moved from the synchroniser rings themselves to such components made by powder metallurgy techniques such as conventional metal powder pressing and sintering or the relatively new technique of metal injection moulding, the latter technique being preferred due to the better resulting material properties. Thus, it is sufficient for relatively simple machined features to be provided on the synchroniser ring itself in order to locate the synchroniser ring on the blocking and pre-energising mechanism.

The machining operations on the basic tube may be largely carried out by a sequence of turning steps. However, some relatively very simple milling and/or grinding steps may be required. An example of a synchroniser ring according to one embodiment of the present invention is a fully turned form on all outer surfaces except for a small number of axially directed grooves formed by milling of the outer surface, the grooves being for the other components of the pre-energiser, self-energiser blocking mechanism to locate with. Such milled grooves may be formed on the base tube and may be of sufficient axial length thereon such that a single sequence of milling operations on the base tube may provide the location features for a plurality of synchroniser rings as they are parted off the tube during subsequent turning operations .

In the present invention a single tube may provide a plurality of synchroniser ring annular members which may be produced automatically by a programmed sequence of machining operations.

According to a second aspect of the present invention, there is provided an annular member for a synchroniser ring for a synchroniser assembly of a multi-ratio transmission characterised in that all external surfaces of the annular member are machined.

One machined surface of the annular member may be of frusto-conical form and may form one of the friction surfaces of the pair of friction surfaces referred to above. However, the machined frusto-conical surface may be provided with a coating or lining of a different, enhanced friction material such as pyrolytic carbon, for example, as is known in the art.

In the present invention, the majority of the machined external surfaces and area of the annular member- are surfaces of revolution, i.e. surfaces formed by cutting or abrading when rotating about an axis.

Suitable location means for preventing relative angular rotation between the annular member and a co-operating blocking and energising mechanism may be provided by simple slots or grooves cut into the outer, axially directed surface, for example.

The tube from which the synchroniser ring annular member may be formed may be made of steel of a suitable grade . The steel tube may be formed by extrusion or by any suitable forming process where the quality may be maintained at a sufficiently high level for the intended use as synchroniser rings.

In preferred embodiments of annular members of the present invention, all external surfaces, except for location slots, for example, may be surfaces of revolution.

According to a third aspect of the present invention there is provided an annular member according to the second aspect of the present invention with a co- operating blocking and energising mechanism for a multi- ratio transmission.

According to a fourth aspect of the present invention there is provided a multi-ratio transmission having the annular member of the second aspect of the present invention or the annular member and blocking and energising mechanisms of the third aspect. According to a fifth aspect of the present invention there is provided a vehicle having a transmission according to the fourth aspect of the present invention.

In order that the present invention may be more fully understood, an example will now be described with reference to the accompanying drawings, in which:

Figure 1 shows a partial cross section above an axis of gear rotation through a double acting synchroniser in the neutral position;

Figure 2 shows a sectional view of a portion of the synchroniser looking along line 2-2 of Figure 1;

Figure 3 shows a so-called "insert" member from the synchroniser of Figures 1, 2 and 4;

Figure 4 shows a perspective view of the pre-energising, self-energising and blocker of the synchroniser of Figures 1 and 2 ;

Figures 5A to 5C show various perspective views of a so- called "blocker" member which co-operates with the insert member of the synchroniser;

Figure 6 shows an end elevation of a synchroniser or baulk ring for the synchroniser of the preceding Figures according to the present invention;

Figure 7 shows a perspective view of the baulk ring of Figure 6 ; Figure 8 shows a detail of the outer surface of the baulk ring of Figures 6 and 7;

Figure 9 shows an axially exploded perspective view of some of the major components of the synchroniser assembly of the present invention;

Figure 10 shows a detail of the pre-energiser, self- energising blocker mechanism; and

Figure 11 which shows a perspective view of a prior art synchroniser ring.

Referring now to the drawings and where the same features are denoted by common reference numerals.

The term "synchroniser" denotes a clutch mechanism which matches the rotational angular velocities of a selected desired ratio gear with an output shaft so as to non- rotatably couple the selected gear with the shaft to provide drive from the gear to the shaft. The term "pre- energiser" denotes a mechanism whereby a friction clutch is brought into engagement with the desired gear in response to a driver, for example, initially attempting to engage said gear by a shift lever, for example. The term "self-energising" shall denote a mechanism whereby the engaging force of the friction clutch may be increased proportionally to the synchronising torque of the friction clutch.

Figure 1 shows a partial cross section through an axially directed plane above an axis of rotation of a synchroniser assembly 10 embodying two baulk rings according to the present invention. The synchroniser 10 is a double acting assembly providing synchronisation for two gears 12, 14 by moving to the right (gear 14) or to the left (gear 12) . The two gears 12, 14 and the synchroniser assembly 10 form part of a larger, multi- ratio transmission unit and may contain further pairs of gears (not shown) of different ratios to gears 12, 14 having their own dedicated synchroniser assembly (not shown) . However, any such additional synchroniser assembly and gear ratio pairs will operate in essentially the same manner as in the example to be described with reference to Figures 1 to 10. The provision of a single acting synchroniser assembly acting on only a single gear ratio is not precluded from the present invention.

The two gears 12, 14 shown in Figure 1 have their radial extents curtailed in the drawing as also do the cooperating gear flanges to be described in greater detail hereinbelow. However the operation of the gears and gear flanges is well known in the transmissions art and such an omission in the drawings will not hinder the understanding thereof by the skilled person. Figure 9 shows the full radial extent of the gear flanges which are permanently coupled with the gears themselves.

The gears 12, 14 are axially spaced-apart on a shaft 16 and, before selection and engagement, are able to rotate relative to the shaft 16 and about the axis 18 thereof. The gears 12 , 14 are constrained by known means so as not to be slidable axially relative to the shaft 16 and to each other. Situated between the gears 12, 14 is a hub member 20 which is fixed both axially and non-rotatably to the shaft 16. The hub member 20 has a plurality of axially directed splines 22 distributed around the outer periphery thereof, the splines being equally spaced apart from. each other in the circumferential direction but, in this case, omitted at three circumferential, equally spaced-apart radially and axially relieved portions 24. The relieved portions 24 accommodate the pre-energising, self-energising blocker mechanisms which form part of the synchroniser assembly and which are seen in greater detail with reference to Figures 2 to 10.

Adjacent each gear 12, 14 is a gear flange 28, 30, respectively. The gear flanges are non-rotatably coupled to the gears by splines 32, 34 on an inner periphery of the gear flanges and co-operating splines 36, 38 on shoulders 40, 42 of the gears 12, 14, respectively. Disposed around the outer periphery of the hub member 20 is a sliding sleeve member 44 which is in axial sliding engagement with the hub member via internal splines 46 which co-operate with the external splines 22 of the hub member (see Fig. 9) . Thus, the sliding sleeve member 44 is able to move axially relative to the hub member 20 but cannot move rotationally relative to the hub member. The axial position of the sliding sleeve member 44 is determined partly by the position of a gear shift lever (not shown) for example, which is in operable engagement with gear selector forks (not shown) which are received in a circumferential recess 45 in the outer periphery of the sliding sleeve member 44, the shift lever being actuated by a driver, for example, and partly initially by the pre-energising, self-energising blocker mechanisms in conjunction with baulk rings. The baulk rings operate, as will be explained in detail below, to match the angular velocities of the gears 12 or 14 with the shaft 16 such that the internal splines 46 of the sliding sleeve member 44 are able to engage with external teeth 50, 52 on the appropriate gear flange 28 or 30 so as to non-rotatably couple gear 12 or 14 with the shaft 16.

The gear flanges 28, 30 have axially directed flange portions 54, 56 of frusto-conical form in cross section, the sloping surfaces 58, 60 co-operating with similarly angled internal frusto-conical surfaces 62, 64 on baulk rings 66, 68. The frusto-conical surfaces 62, 64 may be lined or coated with suitable material (not shown) having enhanced frictional characteristics as is known in the art and will not be explained further herein. The baulk rings 66 , 68 are provided with axially directed grooves 70 which co-operate with features on the blocker member 82, described below, such that the baulk rings are constrained to rotate with the hub member 20 and sliding sleeve member 44.

The three circumferentially spaced-apart recesses 24 in the hub member 20 each house integrated pre-energising, self-energising blocker mechanisms 72. Each recess 24 is bounded at each circumferential end 74, 76 thereof by self-energising or boost ramp surfaces 74a, 74b and 76a, 76b. Features of the pre-energising, self-energising blocker assemblies 72 co-operate with the grooves 70 so as to transmit an axially directed shifting force from the selector/sliding sleeve member 44 to bring the friction surfaces 54, 62 or 56, 64 into engagement as appropriate whilst preventing rotation of the baulk ring relative to the pre-energising, self-energising blocker mechanisms 72.

Each mechanism 72 includes an insert member 80 (see Fig.3) which co-operates with a blocker member 82 (see Fig.5) to form the principal components of the pre- energising, self-energising blocker mechanism 72. Each insert member 80 has circumferentially spaced-apart end portions 84, 86 and an intervening body member 88 which has a radially outwardly extending circumferentially directed spine portion 90 which is received in a cooperating circumferentially directed slot 92 in the sliding sleeve member 44. The relative slot 92 and spine 90 dimensions are such that a pre-determined, limited degree of relative circumferential movement between the slot 92 (and, therefore, between the insert member 80 and the hub 20 and sliding sleeve member 44) and insert member 80 is permitted. The end portions 84, 86 are defined by angled self-energising or boost ramps 84a, 84b and 86a, 86b which react against the boost ramps 74a, 74b and 76a, 76b, respectively of the hub member as appropriate. The end portions 84, 86 also possess blocker ramp surfaces 84c, 84d and 86c, 86d which react against co-operating ramp portions 94a, 94b and 96a, 96b of the blocker member 82 as appropriate according to the circumstances. The grooves 70 on the baulk rings cooperate with lugs 97a, 97b and 98a, 98b on the blocker member 82. The grooves 70 and these lugs are always engaged so as to prevent relative rotation between the baulk ring and blocker 82 but some relative axial movement is permitted within predetermined limits.

Sandwiched between the insert 80 and the blocker member 82 is a strut member 100. The strut member 100 is received in a depression 102 in the radially upper surface of the blocker member 82 and in a recess 104 between the ends 84, 86 on the radial underside of the insert member 80. The strut is resiliently biased in a radially outwardly direction by a spring member 106 such that the insert member 80 is held in resiliently biased manner in the slot 92 of the sliding sleeve member 44, the spring member 106 being held in a cavity 108 in the depression 102 of the blocker member 82. The strut oo has a raised centre portion 110 which is initially resiliently held in a depression 112 on the radial underside of the insert member 80 within the recess 104, this arrangement providing a detent function when the gearbox is in neutral. However, due to the resilient biasing of the insert 80, blocker 82 and strut 100 together, the insert 80, blocker 82 and strut 100 are able to move relative to each other within predetermined limits under the actions of torque and axially directed forces as will be explained in detail below.

As may readily be seen from Figures 1 and 9, friction surfaces 58, 62 and 56, 64 pair up to form friction clutches when moved axially together. All of the normal considerations relating to gear transmissions are incorporated into the transmission according to the present invention, such considerations including lack of significant free play between mating gear teeth and sliding spines, appropriate forms on the ends of splines to define jaw teeth and on gear teeth to enable smooth engagement therebetween to provide positive driven engagement between the gear flanges 28, 30 and the sliding sleeve member 44 after operation of the synchroniser 10.

The operation of the above described gear and synchroniser assembly will now be described with reference to a desired shift, from neutral into driving engagement with gear 12. A vehicle driver moves a shift lever (neither shown) , for example to select gear 12. A gear selector (not shown) in the outer circumferential channel 45 of the sliding sleeve member 44 applies a force in the leftward direction as seen in Figure 1. The sliding sleeve member 44 acting through the pre-energising, self-energising blocker mechanism 72 moves the baulk ring 66 in the leftward direction to take up the wear gap tolerance until the frusto-conical friction face 62 of the baulk ring is brought into rubbing engagement with the cooperating frusto-conical friction face 58 of the gear flange 28. The initial result of this contact is for the oil film between the surfaces 58, 62 to be wiped away and for a torque reaction to be established between the gear flange member 54 and the sliding sleeve member 44 and blocker mechanism 72. The torque reaction may be in either rotational direction depending upon whether the gear shift is an upward or downward shift in ratio. Continued shift force in the leftward direction causes the sliding sleeve 44 to move further leftward, initially with the pre-energising, self-energising blocker mechanism 72 with the raised portion 110 of the strut 100 still retained within the depression 112 of the insert member 80. However, the insert 80 moves slightly leftward and causes the boost ramp surface 84a of the insert and 74a of the hub member to engage (if the gear being selected is gear 14 then boost ramp surfaces 74b, 84b would engage; furthermore, if the torque reaction were in the reverse rotational direction, 76a, 86a would engage when selecting gear 12) . An axially directed leftwards force dependent upon the magnitude of the torque reaction is generated due to the engagement of the angled boost ramp surfaces 74a, 84a. The spine 90 of the insert 80 slides in the slot 92 in the sliding sleeve 44 (depending upon the rotational direction of the torque reaction) . This generated axial force is additional to the driver initiated shift force and assists the friction faces 58, 62 in being brought together with increased force . The detent load function created between ramp 114 and ramp 116 is used initially to transfer the axial force to the friction cone to generate a pre-energising torque between the synchroniser ring 66 and flange 28. This torque rotationally indexes the two parts, including the mating components, i.e. the insert 80 and blocker 82. The indexing movement assures that the blocking ramps 84d contacts 94b and as appropriate 84c, 86c and 86d will contact one of faces 94a, 96a, 96b depending upon the relative speeds of the gear and the gear to be synchronised. The effect of the insert 80 moving axially is to bring the blocking ramps 86c, 86d, 84c and 84d of the insert member 80 into contact with the ramps 94a, 94b, 96a, 96b as appropriate to prevent the sliding sleeve member 44 and insert 80 from moving further leftward, i.e. fulfilling a blocking function stopping attempted engagement of teeth 50 of the gear flange 28 with the splines 46 of the sliding sleeve member 44 until the angular rotational velocities of the gear flange 28 and sliding sleeve 44/hub member 20 are synchronised. The faces 74a and 84a continue to engage at this stage and generate additional axial force to assist synchronisation. As the angular speeds of the gear 12 and shaft 16 converge to synchronous, the torque due to the interaction of the blocking faces 84d, 94b overcomes the synchronising torque and the faces 84d, 94b disengage and allow the insert 80 to index leftwards relative to the blocker member 82. When the faces 84d, 94b disengage the sliding sleeve 44 is free to move leftwards since the angular velocities of the gear 12 and shaft 16 are now synchronised thus enabling the internal splines 46 on the sliding sleeve to engage with the teeth 50 on the gear flange 28 to provide positive driven engagement between the gear 12 and shaft 16.

The baulk rings 66, 68 are essentially identical to each other .

In the present invention, the baulk rings 66, 68 are produced from steel tube . All of the external surfaces : outer diameter 120, front face 122, inner frusto-conical surface 62, 64, rear face 124 are formed by turning operations without the need to remove from a turning machine so obviating the need to find new datums for measurement. The rear face 124 may be formed by a parting-off operation to sever the baulk ring from the base tube. The rotational axis 130 generated by the turning machine itself (not shown) effectively produces its own datum from which all machining measurements may be established. The grooves 70 may be produced by indexing around the axis 130 by 120° and bringing an integrated milling cutter into cutting engagement. Alternatively, the base tube may be grooved for a length such that a single grooving operation on the base tube may suffice for a plurality of separate baulk rings. If desired the front 122 and rear faces 124 may be ground to ensure parallelism. However, it will be apparent that the machining operations to produce the baulk rings of the present invention are far simpler and more economic than those required on the prior art baulk ring of Figure 11.

The insert 80 and blocker member 82 may be formed by the recently introduced technique of metal injection moulding. This technique permits economic production of complex shapes from strong materials such as highly alloyed steels or carbon steels and any desired heat treatments .

Thus, modern production techniques allowing the transfer of complex shape features to other components which may be produced economically has allowed great cost reductions in the manufacture of baulk rings having less complex shapes and resulted in an overall cost reduction whilst allowing technical advances in synchroniser assemblies .

Claims

1. A method for the production of an annular metal member for a synchroniser ring for a synchroniser assembly for a multi-ratio transmission characterised in that the annular member is formed by machining from a tubular member.

2. A method according to claim 1 wherein the annular member is machined on all surfaces.

3. A method according to either claim 1 or claim 2 wherein all external faces of the annular member may be turned.

4. A method according to any one preceding claim wherein a single tube member provides a plurality of annular members .

5. A method according to any one preceding claim wherein all machining measurements are taken from an axis of rotation of the tube being machined.

6. A method according to any one preceding claim wherein all external faces of the annular member are surfaces of revolution.

7. An annular member for a synchroniser ring of a synchroniser assembly for a multi-ratio transmission wherein all external surfaces are machined .

8. An annular member according to claim 7 wherein all external surfaces are initially turned surfaces .

9. An annular member according to either claim 7 or claim 8 wherein an inner, generally axially directed face, is of frusto-conical form.

10. A multi-ratio transmission having an annular member according to any one of preceding claims 7 to 9.

11. A vehicle having a transmission according to claim 10.

12. A method for the manufacture of an annular member for a synchroniser ring of a multi-ratio transmission substantially as hereinbefore described with reference to the accompanying description and Figures 1 to 10 of the drawings.

13. An annular member for a synchroniser ring of a multi-ratio transmission substantially as hereinbefore described with reference to the accompanying description and Figures 1 to 10 of the drawings .