EP1368573A1

EP1368573A1 - Shaft comprising a part connected thereto by welding

Info

Publication number: EP1368573A1
Application number: EP02703386A
Authority: EP
Inventors: Oskar Kehrer
Original assignee: Magna Steyr Powertrain AG and Co KG
Current assignee: Magna Steyr Powertrain AG and Co KG
Priority date: 2001-03-07
Filing date: 2002-03-07
Publication date: 2003-12-10
Also published as: CA2440084A1; US7137897B2; JP2004522913A; WO2002070911A1; AT5144U1; US20040136776A1

Abstract

The invention relates to a shaft (1) comprising a rotating element (2) secured thereon, which comprises a solid surface perpendicular to the axis (3) of the shaft, whereby the welding is carried out in the groove formed between the bearing surface (4) of the shaft and the axis normal surface (6, 8) of the elements. In order to achieve a durable connection without impending the rotation thereof, a welding bead begins on a starting point (21) on the surface (6, 8) perpendicular to the axis (3) is guided towards the groove, whereupon it is re-guided to an end point (21') on the surface (6, 8) perpendicular to the axis of the shaft.

Description

SHAFT WITH MEANS OF WELDING WITH YOUR CONNECTED PART

The invention relates to a shaft with a co-rotating element mounted and fastened thereon, the shaft being cylindrical at least in the region in which the element is mounted, and the element having a cylindrical seat surface and at least one surface lying transversely to the seat surface, and wherein the welding takes place in the throat formed between the seat surface of the shaft and the surface of the element lying transversely to the seat surface. Region means the fastening point of the element and its surroundings in at least one longitudinal direction.

The shaft can be a drive shaft, gear shaft, crankshaft, camshaft or balance shaft of a piston machine, the co-rotating element thus any flange, a wheel or gear, part of a clutch, a cam or a balance weight. In particular, we are thinking of shafts that run at high speed and which therefore place high demands on accuracy and concentricity. Such shafts are usually made of tempered steel or case-hardened steel, the elements are often made of case-hardening steel or case-hardened steel and / or are forged investment castings or sintered parts. Materials which are advantageous and preferred for the rotating part are steels with a carbon content of less than 0.45% or cast iron or spheroidal cast iron, the matrix of the basic structure consisting of at least 40% ferrite, remainder pearlite, martensite or intermediate stage structure (bainite).

In the case of such pairings, it has so far been an article of faith that a direct weld connection - in particular by arc welding - must be avoided, apart from special solutions using friction welding or laser welding. There are two reasons for this: firstly, the heating of the shaft leads to its distortion, which affects the concentricity; Secondly, cracks develop at the beginning and / or end of the weld bead, which reduce the fatigue strength or lead to breakage soon. One of the reasons for the formation of the cracks is that the structure and breakdown of the arc cannot be synchronized with the melting of the weld.

It is therefore an object of the invention to make such pairings accessible for direct welding, in particular arc welding. The shaft and element should be welded in such a way that a permanent connection is created without compromising accuracy, concentricity or fatigue strength.

According to the invention this is achieved in that a welding bead starts at a starting point of the surface lying transversely to the seat surface, is led to the throat and is then guided again to an end point on the surface lying transversely to the seat surface. The start and end point of the weld bead are therefore away from the more sensitive part, usually the shaft. On the transverse surface of at least in the zone of this surface the beginning and / or end crater of the welding bead does not disturb less stressed element. The connecting part then lies in the throat. The welding bead can, but does not have to, follow the entire circumference of the shaft; it can remain limited to one part or to several parts of the circumference. The favorable load case of a weld seam made in such a throat allows a very slim and short weld bead. Due to this and the special shape of the welding bead, the heat input remains low and the shaft does not warp.

Depending on the position of the surface lying transversely to the seat surface, different shapes of the welding bead are advantageous. If the surface transverse to the seating surface of the shaft is essentially axially normal, in a first variant the welding bead is guided in a curve to the throat, this follows over an arch part and is then again rounded to the end point (claim 2). This ensures that the welding bead is pulled at a constant speed. If you made a corner, the arc would stay longer there and the workpiece would be warmed up more locally. In a second variant, the welding bead is guided in a straight line from the starting point to the end point and affects the throat in between (claim 3). This is particularly easy to manufacture, saves delivery time and ensures a constant welding speed. Because of the width of the welding bead, despite the guidance on the straight line, it captures an arc of finite length.

If the surface transverse to the seating surface of the shaft is essentially axially parallel, the welding bead is rounded from the starting point to the throat and back to the end point (claim 4). In one variant it is Welded bead guided from the start point to the end point in an arc tangent to the throat (claim 5).

In the case of axially parallel surfaces, these can also be distributed over the circumference several times and at equal angular intervals, each of which forms a throat which receives a welding bead with the shaft (claim 6).

The good fatigue strength of a connection designed in this way allows, and the striving for the lowest possible and only local heating makes it desirable, in a further development of the invention, the height of the weld bead with only a fifteenth (1/15) to a twenty-fifth (1/25) to measure the diameter of the shaft (claim 7). The height of the weld bead is defined for a fillet weld with the radius of the quarter circle that bounds it.

For thermal and metallurgical improvement of the weld seam, if no MIG welding is carried out, it is advantageous to carry out the welding (W (G, plasma or laser welding) under protective gas and with the supply of a cold filler wire (claim 8) and with certain base materials Welding with the supply of an austenitic additional wire (claim 9). The cold filler wire reduces the heat input. However, this is only possible if the filler wire is not live as in the MIG process. The austenitic filler wire improves the structure.

TIG or plasma welding is used when, with an undivided housing, the rotating machine element in the housing is to be connected to the already installed shaft, because no welding spatter occurs in these processes. It is particularly advantageous a pulsed welding current to achieve the lowest possible heat input with good penetration.

In a particularly advantageous application of the invention to a balancing shaft of an internal combustion engine, the element being a balancing weight with an eccentric center of gravity, the welding is arranged on the side of the shaft facing away from the center of gravity (claim 10). On this side, the mating surface of the element is pressed onto the shaft by centrifugal force, which results in a favorable stress condition.

A functionally and technically particularly favorable construction consists in that the counterweight is an eccentric ring with two end faces and a cutout with two inner end faces on the side of the shaft facing away from the center of gravity, so that it consists of two ring parts with mutually facing inner faces on both sides of the cutout and consists of a segment part on the side of the eccentric heavy point (claim 11). With this type of balance weight, a maximum of eccentricity of the center of gravity is achieved with a minimum of total mass. In extreme cases, this also provides four flat surfaces for the weld connection, which are located transversely to the axis of the shaft and two parallel to the axis, two of the transversely located surfaces only over part of the circumference.

An advantageous solution is that the welding beads are arranged only on the inner, axially normal inner surfaces (claim 12). They take up practically no installation space and are located on one Place of the shaft at which they are not under tension due to the supporting effect of the balance weight surrounding them.

A particularly beautiful solution is that the welding beads are arranged on the inner axially parallel inner surfaces (claim 13) and the two of which are diametrically opposite one another (claim 14). This means that any heat distortions are centric-symmetrical and cancel each other out.

The invention is described and explained below with the aid of figures. They represent:

Fig. 1: A longitudinal section through the subject matter of the invention, Fig. 2: A cross section according to BB in Fig. 1, Fig. 3: A cross section according to BB in Fig. 1 in a variant, Fig. 4: A cross section through a first other embodiment the invention analogous to FIG. 2, FIG. 5: a cross section through a second different embodiment of the invention analogous to FIG. 2, FIG. 6: a plan view of the object of FIG. 1 in another embodiment,

Fig. 7: A variant of Fig. 6.

In Fig. 1 and Fig. 2 is a shaft with 1, the axis of rotation with 3 and a fixed on the shaft 1 rotating element with 2. The shaft here is a balance shaft, the rotating element is a balance weight, which is attached to the cylindrical seat 4 of the shaft 1. The shaft 1 is cylindrical over its entire length, but could also be offset on one side of the element and enlarged in diameter so that it has a larger cylindrical seat 4 'there. The element 2, here a counterweight, has two outer surfaces 6 and a cutout 7 which extends only over part of its circumference and which forms two inner end surfaces 8. These end faces are generally transverse to axis 3, in the special case normal to it. Between the surfaces 6, 8 and the cylindrical seat surface 4 of the shaft, a right-angled throat is formed which is suitable for welding. The surfaces 6, 8 do not have to be axially normal; it is sufficient that the generatrix encloses an angle with the seat surface 4 of the shaft which is of the order of a right angle. In most cases, the surfaces are planes.

The balance weight 2 consists of two ring parts 9 and a segment part 10 with an eccentric center of gravity 11. The two ring parts with the cutout 7 in between thus form a “brace” which holds the segment part 10 in operation against the centrifugal force. The balance weight 2 has a cylindrical Seat 12, which fits for example with a sliding seat on the cylindrical seat 4 of the shaft.

The shaft consists of a tempered steel, for example hardened or tempered 42 CrMo4, which is not easy to weld under normal circumstances. The welding of parts with a hardened structure usually requires special measures, for example special welding consumables. The balance weight 2 consists of forged case-hardened steel, e.g. C15, but could also consist of cast steel or nodular cast iron (e.g. GGG40).

To fix the balance weight 2 on the shaft 1, a welding bead 20 is placed on each of the two inner surfaces 8. This runs from an initial point 21, the initial crater, via a curve 22 in an arcuate part 23, which represents the actual weld seam, again via a curve 22 to an end point 21 ', the final crater. The height 24 of the welding bead 20, here measured in the angular symmetry of the welded surfaces, can be small. For example, with a shaft diameter of 25 millimeters, it is 1.3 millimeters. Due to this thin welding bead, only little heat is supplied to the workpiece.

FIG. 3 is a variant of FIG. 2, which differs from it only in that the welding bead 30 runs in a straight line between the start and end craters 31, 31 '. The weld seam itself is then only the zone 33 in which the weld bead 30 touches the shaft 1.

Fig. 4 shows another application example. A hub 42 is seated on the shaft 1. Two welding beads 40, which lie opposite one another and whose course is identical to that shown in FIG. 2, are provided for connecting them. The advantage of the symmetrical arrangement of the welding beads with regard to possible heat distortion is obvious.

5 finally shows, as an application example, the attachment of a gear wheel 52 on a shaft 1. Here, three rectilinear welding beads 50 are provided, the starting crater 51 and end crater 51 'of which are again only on the gear wheel 52, away from the shaft 1. A weld connection according to the invention can be used all end faces, in this case also on the side of gear 52 that is invisible in the illustration. If it is case-hardened, it should be free of carburization in the area of the weld seam. The welding itself is preferably carried out in a TIG or MIG process under protective gas, with an austhenitic additional wire being fed in the example of material pairing. In order to minimize the heat input, the additional wire should be supplied cold, i.e. not preheated.

Fig. 6 shows another embodiment of the welded connection using the example of the balancer shaft of Fig. 1, which is not cut here, but is shown in view. This other embodiment can be used as an alternative or in addition to that of FIG. 1.

The rectangular cutout 7 in the development is delimited by the two inner surfaces 8 in axially normal planes and two further inner surfaces 60 in axially parallel planes. These two surfaces 60 also form grooves with the seating surface of the shaft, each of which in this embodiment receives a welding bead 61. This runs from an initial crater 62 in a fillet 63 to the straight part that creates the welded connection and again in a fillet to the end crater 62 '. The two craters 62, 62 'again lie only on the inner surfaces 60 of the counterweight 10. In the variant in FIG. 7, the welding bead 71 runs from the initial crater 72 in an arc, preferably an arc, to the end crater 72'. The arc-shaped welding bead 71 creates the connection between the shaft and the counterweight over a length 74.

The welded connections described have achieved exceptionally good fatigue strength values with undiminished running precision of the shafts.

Claims

Patent claims

1. shaft (1) with attached and attached co-rotating element (2), the shaft being cylindrical at least in the region in which the element is mounted, and the element having a cylindrical seat surface (12) and at least one transverse to it Has seat surface, and wherein the welding takes place in the throat formed between the seat surface of the shaft and the surface of the element lying transversely to the seat surface, characterized in that a welding bead (20; 30; 40; 50; 61; 71) on one Starting point (21; 31; 41; 51; 62; 72) begins on the surface (6; 8; 60) lying transversely to the seating surface of the shaft (1), leads to the throat and then again to an end point (21 '; 31' ; 41 '; 51'; 62 '; 72') is guided on the surface (6; 8; 60) lying transversely to the seat surface.

2. Shaft according to claim 1, wherein the surface (6; 8) lying transversely to the seating surface of the shaft is substantially axially normal, characterized in that the welding bead (20; 40;) leads from the starting point (21; 41) to the throat is, this follows over a curved part (23) and is then guided with a curve (22) to the end point (21 '; 41').

3. Shaft according to claim 1, wherein the transverse to the seat surface of the shaft surface (6; 8) is substantially axially normal, characterized in that the welding bead (30; 50) straight from Starting point (31; 51) to the end point (31 ';51') is guided and the throat is tangent in between.

4. Shaft according to claim 1, characterized in that the transverse to the seat surface (12) surface (60) is substantially axially parallel and that the welding bead (61) from the starting point (62) in a curve (63) to the throat and on End point (62 ') is guided.

5. Shaft according to claim 1, characterized in that the transverse to the seat surface (12) surface (60) is substantially axially parallel and that the welding bead (71) from the starting point (72) to the end point (72 ') in one throat tangent arc (74) is guided.

6. Shaft according to claim 4, characterized in that the element has a plurality of axially parallel surfaces distributed at equal angular distances from one another over the circumference, each of which forms a throat receiving a welding bead with the shaft.

7. Shaft according to claim 1, characterized in that the height (24) of the welding bead is 1/15 to 1/25 of the diameter of the shaft (1).

8. Shaft according to claim 1, characterized in that the welding is carried out under a protective gas and with the supply of a cold filler wire.

9. Shaft according to claim 1, characterized in that the welding is carried out under a protective gas and with the supply of an austenitic additional wire.

10. Shaft according to claim 1, wherein the shaft (1) is a balancing shaft of an internal combustion engine and the element (2) is a balancing weight with an eccentric welding point (11), characterized in that the welding on the side of the center of gravity (1) facing away Shaft (1) is arranged.

11. Shaft according to claim 10, characterized in that the counterweight is an eccentric ring with two axially normal outer surfaces (6) and a cutout (7) on the side of the shaft (1) facing away from the center of gravity (11), so that it consists of two Ring parts (9) with mutually facing inner surfaces (8) on both sides of the cutout (7) and ordered from a segment part (10) on the side of the eccentric center of gravity.

12. Shaft according to claim 11, wherein the inner surfaces (8) are axially normal, characterized in that the welding beads (20; 30) are arranged on the axially normal inner surfaces (8).

13. Shaft according to claim 11, wherein the inner surfaces (60) are axially parallel, characterized in that the welding beads (61; 71) are arranged on the axially parallel inner surfaces (60).

14. Shaft according to claim 13, wherein the inner surfaces (60) are axially parallel, characterized in that the axially parallel inner surfaces (60) opposite each other and each of which receives a welding bead (61; 71).