Driver and a method and arrangement to produce it

1. Background

1.1 Technical field

The present invention relates to a driver according to the introductory part of the attached claim 1.

The invention also relates to a method for making a driver according to the introductory part of the attached claim 13.

The invention further relates to a device according to the introductory part of the attached claim 27.

1.2 State of the art

A propeller shaft is used for transmitting torque from a gearbox to a rear axle of a vehicle and comprises substantially a tubular element, the ends of which are usually provided with a splined journal driver and a tube yoke respectively. Drivers of this kind are fitted with a so-called joint cross to make it possible to transmit torque even with a certain amount of varying angular deviation between, for example, the axial direction of the gearbox and that of the propeller shaft.

Such drivers are currently made of steel which is forged, followed by machining in the form of turning, drilling and milling, resulting in a high article cost. The necessary high strength of the forged article entails a large amount of material and a consequently large weight.

An object of the present invention is to propose a propeller shaft driver which has the same strength as, but weighs less and can be made at lower cost than, known drivers.

A further object of the invention is to propose a method for making drivers according to the invention and a device for implementing the method.

2. Summary of the invention

The above objects are achieved by features in the characterising part of the attached independent claims 1, 13 and 27 respectively.

Further advantages are afforded by what is specified in the respective dependent claims.

3. Brief description of the drawings

The invention is described in more detail below in relation to embodiment examples and preferred embodiments, in which the same items are as far as possible designated by the same reference notations and in which

- Fig. 1 depicts a first embodiment of a driver according to the invention as seen in a perspective view, in which the upper portion is intended to support a joint cross and the lower portion to be fastened to a propeller shaft or a splined shaft,

- Figs. 2a-c depict views of the driver according to Fig. 1 as seen obliquely from the front, obliquely from the right and from above in Fig. 1 ,

- Fig. 3 depicts in a perspective view the driver according to Fig. 1 with its joint cross and closing cover fitted and propeller shaft connected,

- Figs. 4a-i depict schematically intermediate forms in the course of a first version of a method according to the invention for making a propeller shaft driver according to the invention,

- Fig. 4b 1 depicts schematically a blank which is intended for the making of two drivers and which by recessing in the wall of the blank constitutes two mutually opposite driver blanks at 90° to one another, showing one such driver blank on the right in the diagram,

- Fig. 5 depicts schematically in an axial section a first embodiment of a device according to the invention for implementing a first forming step concerning a tubular driver blank according to a first version of a method according to the invention,

- Fig. 6 depicts schematically the tool according to Fig. 5 in a different section from Fig. 5 for implementing a first forming step concerning a pretreated tubular driver blank according to a second version of a method according to the invention, showing on the right in Fig. 6 an axial section comprising a preformed lug portion and on the left an axial section comprising a preformed recess between mutually opposite lug portions, and also showing the hole in the lug portion, when the fastening portion has been formed, e.g. by welding, to a desired shape, and

- Fig. 7 depicts schematically a perspective view of a tool similar to that in Figs. 5 and 6 with mutually angled axial sections on each side of the centreline of the tool, showing preformed lug portions of the blank, with a cut lug portion in the left section and a portion between the lug portions in the section on the right.

4. Detailed description of preferred embodiments

The preferred embodiment depicted in Fig. 1 of a driver 1 according to the invention for a propeller shaft 2 (Fig. 3) comprises a substantially tubular fastening portion 3 adapted to being fastened to an element 4 in the form of a propeller shaft tube 4 or a splined sleeve 4, and two mutually opposite lug portions 6 each provided with a hole 5 which protrude from the fastening portion to constitute a driver fork 7 for supporting a joint cross 8 (Fig. 3). Fig. 2 depicts planar views of the driver according to Fig. 1.

The driver 1 is made from a substantially tubular blank 9 (Fig. 4a), the two lug portions being created by recesses 10 and holes 11 in the wall 12 of the blank, and the seats for the joint cross taking the form of a reinforcing bushing 13 in the hole of each lug portion.

It is preferred that the end shape of the fastening portion, e.g. as depicted in Figs. 1 and 2, be adapted to the element 4 to which the driver is to be fastened, which end shape is preferably formed by an operation of the form-pressing type, as described below, followed by turning. It is conceivable for turning to take place before forming in the tool. It is preferred that the driver be fastened to the element 4 by welding, preferably laser welding. Examples of other conceivable welding methods are arc welding and friction welding.

The driver preferably has, inter alia to facilitate release during production, a shape which broadens somewhat towards the free ends 14 of the lug portions, this shape preferably being formed in an operation of the form-pressing type.

The blank has preferably a substantially circular cross-section transverse to its axial direction, while the driver has preferably a generally circular cross-sectional configuration transverse to its axial direction 15. The blank and hence the driver are preferably made of hardenable steel, the driver being hardened in a state of use.

The inside of the end 16 of the fastening portion which is directed towards the propeller shaft tube or the splined sleeve is preferably adapted to accommodating a sealing cover 16', which closes the interior of the driver relative to the element 4, to which the driver is intended to be fastened, as schematically depicted in, for example, Fig. 4h.

Fig. 4 depicts steps of making a driver according to the invention according to a first version of the method according to the invention. The method comprises the steps of

a) forming a substantially tubular blank 9, e.g. by cutting from a tube;

b) forming the blank in a tool, e.g. of the kind described further on and depicted in Figs. 5-7, in an operation similar to form-pressing whereby the fastening portion is given an externally somewhat chamfered configuration and the driver blank a configuration corresponding to the free ends of the remaining lug portions and broadening somewhat towards the opposite end from the fastening portion;

c) recessing, e.g. by laser cutting, two mutually opposite lug portions in the wall of the formed blank;

d) holing, e.g. by laser cutting or stamping, to create the holes in the lug portions;

e) imparting to the fastening portion, e.g. by turning, an external configuration adapted to the element to which the driver is to be fastened;

f) fitting a reinforcing bushing in the hole in each lug portion to serve as seats for the joint cross, said bushings preferably being fitted coaxially, followed by the bushings being firmly welded, e.g. by laser welding, and by the driver being thereafter hardened, e.g. by fixture hardening;

g) welding the resulting driver firmly to a propeller shaft tube or a splined sleeve;

h) fitting inside the end of the driver which is directed towards the propeller shaft tube or the splined sleeve a sealing cover which closes the interior of the driver relative to the element to which the driver is fastened; and

i) fitting the joint cross with associated bearings in the reinforcing bushings.

A second version of the method according to the invention for making a driver according to the invention comprises the steps of

a) forming a substantially tubular blank 9, e.g. by cutting from a tube;

bl) recessing (not depicted), e.g.. by laser cutting, two mutually opposite lug portions in the wall of the blank before further forming of the blank, whereby a preferred version (Fig. 4b 1) involves said recessing being done by laser cutting in a blank 9 intended for the making of two drivers in such a way that the laser cutting results in two mutually opposite driver blanks at 90° to one another, provided with lug portions, seen in the drawing as forming part of the common blank;

b2) forming the resulting blank (not depicted), possibly after some adjustment of the lug portions and the shape of other portions, in a tool as described in step b) above;

d)-i) creating the driver as described in steps d)-i) above.

According to a variant of this second version of the method according to the invention, the creation of holes in the lug portions in the tool takes place in association with the previously described forming in the tool, said tool comprising stamping means or the like. If, as preferred, the reinforcing bushings are to be laser-welded firmly in their respective holes, stamped holes have to be post-milled to achieve sufficient dimensional accuracy. It is preferred, however, that the holes be created by laser cutting before or after the forming in the tool.

The device depicted schematically in Fig. 5 represents a first embodiment as seen in a substantially axial section, by which device a tubular blank is intended to be initially formed in an operation of the form-pressing type. The device comprises two tool elements 17, 18, an upper element 17 and a lower element 18, arranged for mutual movement towards and away from one another by at least one of the tool elements, in the case depicted the upper element 17, being moved between a closed state (depicted in Fig. 5) and an open state (not depicted), the one tool element, here the lower element 18, supports a punch 19 and the other element supports a die 20, and the tool is adapted, when the two elements are in the open state, to accommodating the substantially tubular driver blank 9 and using the punch for internal form-pressing to convert the blank 9 to a driver element 9' between the punch and the die by mutual

movement of the tool elements to the closed state. In the version depicted in Fig. 5, the blank 9 is intended to be placed on the punch, which at least along a substantial portion of its axial extent has a diameter smaller than the inside diameter of the blank 9, and the forming is intended to be effected by movement of the die to the closed state of the tool elements.

The punch is so dimensioned relative to the inside diameter of the blank 9 that either the blank is accommodated, before the forming, against an end-stop 21 running in the circumferential direction of the punch and arranged at the portion of the punch which is directed away from the die, or the blank only moves to the end-stop during the forming.

Preferably, the punch has a configuration which narrows somewhat towards the die and the die has a substantially corresponding configuration narrowing somewhat from its aperture 22, so that the resulting narrow forming space 23 close to the bottom end- stop 23' of the die for the upper end 24 of the blank 9' and the free end 25 of the punch is adapted to forming a driver portion 26 on which the fastening portion of the driver is intended to be based.

The construction of the device is described in more detail in relation to Fig. 6.

Fig. 6 depicts schematically the tool with a blank which is preformed in such a way that the lug portions are cut out before the blank is placed in the tool, showing on the right a lug portion in axial section and on the left a lug portion with its hole and turned fastening portion in axial section. According to the version depicted, as schematically illustrated in Figs. 5 and 6, the tool comprises inter alia a bottom plate 27 in which the punch is fastened, a lower ejector 28 also constituting an end-stop 21, an upper ejector 28' also constituting an end-stop 23', an upper fastening plate 29 for applying the upper tool element 17 to a power source, e.g. a hydraulic press (not depicted), various spacing elements 30 for control of stroke length etc., lower ejector pins 31 for movement of the lower ejector, upper ejector pins 32 for movement of the upper ejector, and divided die supports 33 retaining the die in both axial and radial directions.

Embodiments (not depicted) are also conceivable in which the lug portions are provided with their holes by stamping in the tool, as indicated in Fig. 6, in which the tool comprises stamping means adapted, when the tool is in the closed state, to stamping out holes in the lug portions. The stamping elements, with advantage two mutually opposite ones, may be arranged in the punch or in the die, and dollies (dies) for stamping may correspondingly be arranged in the die or in the punch.

A forming cycle with the tool described comprises the steps of raising the die upwards and uncovering the punch, inserting the blank over the conical punch, pressing the die down against the punch to form the blank, raising the die and using the ejectors to eject the formed blank from the tool.

In cases where stamping of the holes is to take place in the tool, the tool comprises with advantage guide means (not depicted) for the punch and/or the die for cooperation with the preformed lug portions and the mutually opposite recesses between them so that the lug portions are positioned in the circumferential direction so that stamping of the holes takes place at desired predetermined points in the lug portions.

It is preferred that the driver according to the invention be hardened before use, although applications are conceivable in which drivers according to the invention are used in an unhardened state.

Where hardening is intended, it can be effected in association with the forming in the tool used or in a hardening fixture after the forming.

In the case of hardening in the tool, it is preferred that turning of the fastening portion 3 and, where applicable, post-milling of stamped holes for the bushings 13 take place before the forming and the hardening.

In the case of hardening in a fixture, it is likewise preferred that turning of the fastening portion 3 and, where applicable, post-milling of stamped holes for the bushings 13 take place before the hardening.

The method and the function of the device and the driver according to the invention are probably substantially indicated above.

The invention is described above in relation to embodiment examples and preferred embodiments. Further versions and also minor modifications and additions are of course conceivable without departing from the fundamental concept of the invention.

Thus dimensions of the tubular blank may be changed depending on the desired performance of the driver. According to preferred embodiments, the wall thickness of the blank is about 10-25 mm, preferably about 15-22 mm. The length of the tubular blank is preferably 100-200 mm.

The form-pressing of the blank 9 may be effected warm but may also be effected cold, thereby reducing the cost of the driver production process.

A suitable steel for making drivers according to the invention is so-called boron steel, which hardens to about 43-51 HRC, but other hardenable grades of steel are of course also conceivable.

Minor modifications and additions to the tool without altering its function are conceivable.

Thus it is possible, in cases where the driver is to be fitted to a splined shaft and is consequently intended during use to engage with a splined sleeve portion, for a splined sleeve portion to be formed during the forming in the tool, in which case the punch comprises spline elements running axially for internal shaping of the blank to form a splined sleeve portion (not depicted).

The invention is thus not to be regarded as limited to the embodiments and versions indicated above but may be varied within its scope indicated by the attached claims.