BACKGROUND ART A synchronizing ring intended to synchronize the rotation speed of two different transmission elements in a vehicle transmission comprises an annular part and a friction surface disposed on the annular part. The friction surface is often conical and it is this surface which, in the synchronization process, is brought into frictional engagement with a corresponding friction surface on another transmission element, for example a coupling ring. This document does not go into detail about the actual synchronization function with associated. transmission elements (for synchronization function, see also, for example, SE 0100453-0 or SE 514321).

The production of synchronizing rings for vehicle transmission purposes can be said to follow the following steps: 1. The starting point is a blank. The blanks can be, for example, conventionally forged, precision-forged, powder-forged or possibly sintered.

Rational blank production is realized with two tool halves which are axially pressed together. The final shape of the blank is determined by a cavity between these tool halves. Production materials for synchronizing rings are

normally steel or brass.

2. The blank might then be worked by, for example, milling, turning, drilling or the like.

3. The blank, which broadly has the appearance of the finished synchronizing ring, is next hardened.

4. Finally, the synchronizing ring is hard-worked (for example, ground) on exacting surfaces (such as, for example, friction surfaces).

At least the production methods comprising precision-forging, powder- forging, with possible sintering make it possible for step 2, i. e. working of the blank by, for example, milling, turning, drilling or the like, to be eliminated.

Elimination of production steps yields cost reductions.

SE 514231 shows a synchronizing ring 14 having an annular part, a friction surface 13 and grooves 32,34 for a pre-synchronizing member in the form of an annular spring 28. The synchronizing ring also exhibits a plurality of different radially projecting protrusions 36,37,30, each having different functions. The protrusions 36 and 37, viewed in the axial direction, are arranged directly in line. The protrusion 36, viewed axially, is defined as the outer protrusion, whilst the protrusion 37 is defined as the inner protrusion.

In order to be able to obtain the groove 32 on the synchronizing ring 14, either the pressing tool must consist of more than two pressing tool parts or there is a need for a subsequent working (according to step 2 above). This is not advantageous from a production viewpoint. More production steps incur increased costs.

The main object of the invention described below is to produce a synchronizing ring with lower production costs and maintained synchronizing

functions.

DISCLOSURE OF INVENTION The problem solution according to the invention, with due regard to the devices according to the invention, is described in Patent Claims 1 and 8.

The problem solution according to the invention, with due regard to the production method according to the invention, is described in Patent Claim 5. Patent Claims 2 to 4 plus 6 to 7 and 9 to 11 describe preferred modes and refinements of the devices according to the invention according to Claims 1 and 8 and the method according to Claim 5.

The first device according to the invention is based on a synchronizing ring of the type stated in the introduction but which is characterized in that the outer protrusions, viewed in the peripheral direction, are displaced relative to the inner protrusions so that the outer protrusions relative to the inner protrusions, viewed in the axial direction, are not arranged directly in line.

The production method according to the invention is based on methods of the type stated in the introduction, i. e. precision-forging and powder-forging.

The production methods encompass the steps: 1. filling of a tool half with metal powder or insertion in a tool half of a forging blank for the forming of the synchronizing ring; 2. pressing-together of the first tool half against a second tool half by means of a force, acting in the axial direction of the synchronizing ring, for forming and possible sintering of the synchronizing ring. The production method is characterized in that the pressing tool halves are produced so that the outer protrusions are not arranged along the same axial line as the inner protrusions, that is to say that the outer protrusions, viewed in the peripheral direction, are somewhat displaced relative to the inner protrusions.

The second device according to the invention is based on a pressing tool of the type stated in the introduction but which is characterized in that the moulds in the pressing tool for the outer protrusions, viewed in the peripheral direction, are displaced relative to the moulds for the inner protrusions so that the moulds for the outer protrusions relative to the moulds for the inner protrusions, viewed in the axial direction, are not arranged directly in line.

The foremost advantage with the first and second device and the method according to the invention is that the production costs are reduced. Another advantage is that the production becomes simpler and requires shorter production time. This is achieved with maintained functions of the synchronizing ring.

Further advantageous modes of the invention can be seen from the contingent patent claims following the main claims (Claims 2-4,6-7,9-11).

BRIEF DESCRIPTION OF DRAWINGS The present invention will be described in greater detail below with reference to the appended drawings showing, by way of example, further preferred modes of the invention.

Figure 1 shows a partial diagrammatic representation of a"rolled-out periphery"or side view of a mode of the synchronizing ring according to the invention.

Figure 2 shows a diagrammatic representation of a section A-A of the mode according to Figure 1.

Figure 3 shows a diagrammatic representation of a section B-B of the mode according to Figure 1.

MODE (S) FOR CARRYING OUT THE INVENTION Figure 1 shows a part of a mode of a synchronizing ring, which synchronizing ring is universally denoted by 14. The synchronizing ring 14 exhibits three different types of radial protrusions 30,36,37. All types of protrusions are necessary for the functioning of the synchronizing ring in the synchronization process. The number of protrusions for respective types of protrusion can, however, be varied. In Figure 1, the protrusions 36 are designated as the outer protrusions whilst the protrusions 37 are designated as the inner protrusions.

According to the background art (see, for example, SE 514231, Figure 4, figure reference 36 and 37), corresponding radial protrusions are arranged directly in line (viewed in the axial direction, for example from the right in Figure 4 in SE 514231).

The production of a synchronizing ring of this type (i. e. of the type shown in SE 514231 and according to the present invention) is realized with two pressing tool halves (not shown), which are pressed together in the axial direction, i. e. from the right and left respectively in Figure 1. The dividing line, i. e. where the pressing tool halves meet, is in Figure 1 indicated by a dotted line 38. The mould for forming a synchronizing ring and its parts is constituted by cavities in the respective tool half. The invention ensures that the axial compression forces from the respective tool half manage to compress the metal powder (in powder-forging) or the blank (in precision- forging) in all parts of the synchronizing ring 14. This is achieved by the fact that none of the details of the synchronizing ring 14 are arranged directly in line, viewed in the axial direction. The synchronizing ring 14 is thereby, in principle, ready-made after the form-pressing and a working step which might be present in the production can be eliminated. The protrusions 36

and 37, viewed in the peripheral direction, are therefore arranged in a displaced position relative to each other (see Figure 1).

In order to produce, as in SE 514231, a recessed groove having two plateaux (32,34 in SE 514231) for a pre-synchronizing member in the form of an annular spring, the plateaued groove must be additionally worked, for example by milling, or additionally pressed with at least a third pressing tool part, in addition to the two pressing tool parts needed to produce the actual annular part of the synchronizing ring with its possible protrusions.

According to the present invention, corresponding plateaued grooves are produced without an extra working step or an extra pressing tool part. This is possible because no details on the synchronizing ring are arranged directly in line, viewed in the axial direction of the synchronizing ring. Corresponding grooves in the synchronizing ring 14 according to the invention are formed by the surfaces 32,34 and 40 (see Figures 1,2 and 3). Preferably, the surfaces 34 and 40 are chosen such that they end up on the same radius measured out from the centre axis of the synchronizing ring (not shown). For maintained functioning, however, the surfaces 32 must be positioned somewhat higher (greater radius) than the two surfaces 34 and 40 (see Figures 2 and 3). The tops of the protrusions 30,36 and 37 are situated highest relative to the surfaces 32,34 and 40 (see Figures 2 and 3). A pre- synchronizing member in the form of an annular spring (not shown) will be able to be arranged either in a higher position on the surfaces 32 or a lower position on the surfaces 34 or 40, depending on which of the surfaces 34 or 40 is situated highest.

The cavities, i. e. the mould in the respective halves of the pressing tool, are configured such that they correspond to the synchronizing ring 14 shown by the Figures 1,2 and 3. The invention is not limited to use in any specific gearing arrangement, but can advantageously be disposed in different types of gearing arrangements, such as, for example, split gears, basic gearboxes or ordinary synchronized gearboxes.