WO2004091832A1

WO2004091832A1 - Composite body

Info

Publication number: WO2004091832A1
Application number: PCT/SE2004/000495
Authority: WO
Inventors: Dan Popescu
Original assignee: Volvo Construction Equipment AB
Current assignee: Volvo Construction Equipment AB
Priority date: 2003-04-16
Filing date: 2004-03-31
Publication date: 2004-10-28
Anticipated expiration: 2005-10-16
Also published as: SE525133C2; SE0301124L; SE0301124D0

Abstract

A composite body, comprising an annular liner (2) and a shell (3) cast on this liner, the liner (2) comprising a first material and the shell (3) comprising a second material which has a higher thermal expansion coefficient and a lower melting temperature than the first material, the liner (2) having an outer lateral surface (9) and an outwardly directed end surface (10) extending radially inward from said lateral surface (9), and the shell (3) being cast in one piece on the lateral surface (9) and the end surface (10). The liner (2) comprises a flange (11) which extends axially from the end surface (10) and is arranged radially inside said lateral surface (9) and against which the shell (3) is cast.

Description

Composite body

TECHNICAL FIELD

The present invention relates to a composite body, comprising an annular liner and a shell cast on this liner, the liner comprising a first material and the shell comprising a second material which has a higher thermal expansion coefficient and a lower melting temperature than the first material, the liner having an outer lateral surface and an outwardly (from the interior of the liner) directed end surface extending radially inward from said lateral surface, and the shell being cast in one piece on the lateral surface and the end surface.

The invention relates to composite bodies in general, but will for the purpose of exemplification be described with reference to a preferred application, in which it forms a transmission component, in particular a gear housing. The materials in question are preferably metals or metal alloys.

The invention relates in particular to composite components where the second material which is cast against the first material does not to any appreciable extent wet the surface of the first material, and where no strong bond, in particular metallic bond, arises in the interface between liner and shell.

Composite means that the body in question comprises two different materials. The term is not to be interpreted so narrowly that only plastics are a possibility; metals are also possible. An equivalent term in the context would be compound body. BACKGROUND OF THE INVENTION

In transmissions in which forces generated by an engine are transmitted to an output shaft, there are gear housings, the inner periphery of which is corrugated and forms splines with which sheet-metal disks engage in a rotationally locking manner.

In normal cases, the gear housing is, for weight-saving reasons, made of a light metal, preferably aluminum or an aluminum alloy. The disks which engage in the splines of the gear housing are preferably made of sheet steel and are each of relatively small thickness . In connection with, for example, braking, the disks are displaced in the axial direction of the gear housing in said splines until contact is brought about between the end wall of the housing and the brake disk lying closest, an in some cases extremely great torque then being transmitted between housing and disks.

It has been found that the disks in low gear housings of working machines of the dumper type in time wear grooves in or ^weat up" the splines of the gear housing owing to the great rotational forces which act between these bodies. The consequence is that there is a risk that the disks will jam in these grooves and therefore have problems with being displaced axially in said splines .

In order to avoid this problem, the prior art has included inter alia mounting a sheet-metal drum with splines in a cast housing made of aluminum. By selecting a material (steel) for the sheet-metal drum which corresponds to the disk material as far as mechanical strength is concerned, it has therefore been possible to avoid the problem of groove formation caused by the disks in the gear housing. As the shell of the housing still consists of aluminum, it has also been possible to keep the weight at a low level. A disadvantage has been that liner and shell have consisted of two separate components, which is disadvantageous in terms of inter alia stock-keeping and distribution. Moreover, an extra working operation is required for inserting the drum into the housing shell and bolting the drum in place.

Attempts have been made by the applicant to cast a body made of aluminum against a liner or a drum which is formed by a ring of corrugated sheet steel, the shell having been cast in one piece against both the outer lateral surface of the liner and a plane, annular end surface of the liner. The end surface extends in a plane essentially at right angles to the outer lateral surface of the liner and at right angles to the center axis of the liner. In this regard, it has been a problem to make the shell adhere to the liner along the entire interface between liner and shell. The cause would be that aluminum and steel have considerably different thermal expansion coefficients, which results in the shell coming away from the liner in particular in the region of the inner periphery of the end surface. Moreover, the liner and the shell have considerably different melting temperatures, for which reason no metallic bond arises during casting, which could counteract said coming-away.

OBJECT OF THE INVENTION

The object of the present invention is to provide a composite body of the kind referred to in the introduction, in which a stable and overall connection between shell and liner is obtained by casting the shell against the liner. The object of the invention is therefore, on the basis of the specific problem with the shell and liner of a gear housing, to provide a solution which is generally valid for casting composite bodies in general of a design corresponding to that described in the preamble of patent claim 1. A secondary object of the invention is to provide a transmission component, in particular a gear housing, which is light and is provided with internal splines which are well suited for taking up great rotational forces from disks positioned therein without said disks eating up the liner/splines of the housing, the transmission component being designed as said composite body. One object of the invention is in this regard to design said liner in such a way that a sufficiently strong connection is obtained between liner and shell only by casting the shell against the liner.

Another object of the invention is to propose a cost- effective method of producing a composite body, in which finishing of the body and costly working operations are minimized.

SUMMARY OF THE INVENTION

The object of the invention is achieved with a composite body of the kind referred to in the introduction, which is characterized in that the liner comprises a flange which extends axially from the end surface and is arranged radially inside said lateral surface and against which the shell is cast.

It has been found that very good adhesion between the shell and the liner is achieved along the entire interface between shell and liner when such a flange as indicated above is arranged on the liner. Such a flange presumably functions as a support for aluminum which solidifies in the region of the inner periphery of the end surface, and in this way prevents the shell coming away from the liner in this region in connection with solidification after casting. It should be mentioned that the flange and the lateral surface extend in opposite directions in the axial direction from the end surface. According to a preferred embodiment of the invention, the composite body is characterized in that the flange has a radially outer peripheral surface which forms an acute angle, that is to say smaller than 90°, relative to the end surface in a region where the outer peripheral surface of the flange and the end surface meet. In this way, the shell is further prevented from coming away from the liner in said region in connection with solidification and cooling. The angle between the outer peripheral surface of the flange and the end surface in said region is preferably smaller than or equal to 85°. It is suitably greater than 45°. The transition between the outer peripheral surface of the flange and the end surface can, but does not have to, be sharp and distinct. It can also be rounded to some extent, but said angular relationship should still be sought .

It is preferred, at least in a case when the composite body forms a gear housing, that the end surface of the liner extends in a plane which is at right angles to the lateral surface and to a center axis of the liner.

According to a preferred embodiment, the flange is annular and coaxial with the lateral surface. It is possible for the flange to be divided into a number of discrete, separate segments which together form a ring or circle around a center axis through the liner, but it is preferred that it is continuous.

A prerequisite for the invention working to advantage is that the liner is thin-walled, with a considerably smaller wall thickness than the shell lying outside. This is in particular the relationship which prevails between a liner made of steel and a shell made of aluminum, as proposed for a transmission component in the form of a gear housing with splines according to the invention. According to the invention, the shell forms a housing with a wall thickness which is 5-15, preferably 8-12, times greater than the wall thickness of the liner. The wall thickness of the liner is essentially the same throughout .

Further features of the invention emerge from the independent claims 8-10.

The invention also relates to a method for production of a composite body, which comprises an annular liner and a shell arranged on the liner, the liner comprising a first material and the shell comprising a second material which has a higher thermal expansion coefficient and a lower melting temperature than the first material, the liner having an outer lateral surface and an outwardly directed end surface extending radially inward from said lateral surface, characterized in that the liner comprises a flange which extends axially from the end surface and is arranged radially inside said lateral surface, and in that the shell is cast in one piece against the lateral surface, the end surface and the flange.

It is preferred that the liner is placed in and forms part of a casting mold and that the material which forms the shell is cast in said mold.

The invention also relates to a method for production of such a composite body, where the body comprises a gear housing for a power transmission device, the gear housing comprising the liner (2), which is provided with splines and adapted to engage in a rotationally fixed manner with a disk (5) arranged in it, and the shell (3) surrounding the liner (2).

Further features and advantages of the invention emerge from the detailed description below and from the other dependent patent claims . BRIEF DESCRIPTION OF FIGURES

Preferred embodiments of the invention will, for the purpose of exemplification, be explained in greater detail with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of a composite body according to a first illustrative embodiment of the invention;

Fig. 2 is a cross section from the side of the composite body according to Fig. 1;

Fig. 3 is a sectional perspective view of the composite body according to Fig. 1 and Fig. 2 ;

Fig. 4 is a cross section of the composite body according to Figs 1-3, and

Fig. 5 is a partly cut-away view from the side of a power transmission device, in which a composite body according to the invention forms a gear housing.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows a composite body 1 according to a first illustrative embodiment of the invention. According to a preferred application shown in Fig. 5, the composite body 1 forms a gear housing which comprises a liner 2 and a shell 3 surrounding the liner. The liner 2 has an inner periphery which is corrugated and forms splines 4 inside the gear housing 1, said splines being adapted to engage in a rotationally fixed manner with disks 5 arranged in the gear housing 1.

With reference to Fig. 5, the gear housing 1, formed by a composite body 1 according to the invention, forms part of a power transmission device 6 which comprises an automatic gearbox with planetary gears. To be precise, the gear housing 1 forms the low gear housing of the transmission device, where the greatest torques will occur. However, the possibility of other gear housings in the transmission device 6, such as an intermediate housing 7, also being formed by a composite body designed in accordance with the invention should not be excluded.

The disks 5 are arranged to engage in said splines 4 at the same time as they are axially displaceable in a translatory movement along these in a direction toward and away from an end wall 8 in the gear housing 1. The individual disk 5 has a relatively small material thickness, that is to say is thin-walled, and is preferably made of steel . In order to counteract the disks wearing grooves and in this way "eating up" the inner periphery of the gear housing 1, the liner 2 is also made of a metal with corresponding mechanical strength, this metal preferably and mainly also consisting of steel. For the purpose of restricting the total weight of the gear housing 1, however, the shell 3 consists mainly of a light metal, preferably aluminum.

The shell 3 is cast directly in one piece against the liner 2, both radially outside that portion of the liner 2 which comprises said splines 4 and has a corrugated outer lateral surface 9 and axially outside the end wall 8 or, to be precise, an external end surface 10 of the wall. In the case of a low gear housing in a working machine of the dumper type with a weight over 60 tons, the liner 2 is thin-walled and has a thickness of the order of 1-3 mm, while the shell has a wall thickness of the order of 20-30 mm, that is to say roughly ten times greater than the wall thickness of the liner 2. The liner 2 is annular, with a center axis XX, about which said ring is essentially rotationally symmetrical. The liner 2 is designed in a way which allows the shell 3, although it mainly comprises a material with an entirely different thermal expansion coefficient, to be cast against the liner 2 and, even after solidification and cooling, to bear closely against the liner 2 along the entire outer periphery thereof, against both the lateral surface 9 and the end surface 10. To this end, the liner 2 comprises a flange

11 which extends in an axial direction (see axis XX) from the outer end surface 10 of the end wall 8. In this context, it should be noted that axial direction means a direction parallel to said center axis, and radial direction means a direction radially out from and at right angles to said axis XX.

The end surface 10 extends in a plane which is essentially at right angles to the center axis XX as it is to the outer, corrugated lateral surface 9 of the liner. In this regard, it forms a plane annular surface. However, it is not excluded that the end surface extends in a different plane and thus has an extension which corresponds to the outer surface of a truncated cone, and that, in the radially inward direction, it also extends axially away from the corrugated main portion of the liner.

The flange 11 is arranged at the radial inner periphery of the end wall 8. It has an outer peripheral surface

12 which forms an acute angle a relative to the end surface in a region where the outer peripheral surface 12 of the flange and the end surface 10 meet, a is preferably smaller than or equal to 85°. This can be brought about either by the outer peripheral surface 12 of the flange 11 having an inclination in relation to the center axis XX or by the end surface 10 having an inclination other than 90° relative to said axis XX. For example, the liner 2 can be Z-shaped in cross section in the region where flange 11, end wall 8 and outer lateral surface 9 meet. In the illustrative embodiment shown, said inclination is achieved by the flange 11 having an increasing thickness in the direction from the end surface 10 at the same time as its radial inner periphery is parallel to the center axis XX. Owing to the angle a being acute, favorable fixing of the shell 3 against the liner 2 is achieved, which counteracts the shell 3 being displaced out of engagement with the liner 2 in the direction of the center axis XX.

The flange 11 should have a length in the direction of the axis XX which is adapted to the thickness of that part of the shell 3 which covers the end surface 10 and also to the material the shell 3 mainly comprises . The outer peripheral surface 12 of the flange 11 should have a length of at least 5 mm in the direction of the axis XX in the case represented.

The composite body 1 is manufactured by means of casting the shell 3 in a sand mold in which the already finished liner 2 is also placed. The liner 2 then forms part of the casting mold. The liner 2 is preferably produced by means of cold-working, for example pressing, an annular blank made of steel.

In the preferred illustrative embodiment, the liner 2 comprises mainly steel, and the shell 3 comprises mainly aluminum. The invention of course also includes other composites, which comprise entirely different materials, where corresponding adhesion problems between liner and shell can be expected to arise owing to different thermal expansion temperatures and melting temperatures of the component materials.

It will be understood that a large number of variants of the invention will be obvious to an expert in the field without departing from the scope of protection of - li the invention as defined in the accompanying patent claims supported by the description and the drawings .

Generally, the invention can be applied in all power transmission cases where disks (for brake or clutch) exert great torques on a liner in which they engage in a rotationally locking manner.

Claims

PATENT CLAIMS

1. A composite body, comprising an annular liner (2) and a shell (3) cast on this liner, the liner (2) comprising a first material and the shell (3) comprising a second material which has a higher thermal expansion coefficient and a lower melting temperature than the first material, the liner (2) having an outer lateral surface (9) and an outwardly directed end surface (10) extending radially inward from said lateral surface (9), and the shell (3) being cast in one piece on the lateral surface (9) and the end surface (10), characterized in that the liner (2) comprises a flange (11) which extends axially from the end surface (10) and is arranged radially inside said lateral surface (9) and against which the shell (3) is cast.

2. The composite body as claimed in claim 1, characterized in that the flange (11) and the lateral surface (9) extend in opposite directions in the axial direction from the end surface (10) .

3. The composite body as claimed in claim 1 or 2, characterized in that the flange (11) has an outer peripheral surface (12) which forms an acute angle relative to the end surface (10) in a region where the outer peripheral surface (12) of the flange (11) and the end surface (10) meet.

4. The composite body as claimed in claim 3, characterized in that the end surface (10) extends in a plane which is at right angles to the lateral surface (9) and to a center axis of the liner (2) .

5. The composite body as claimed in either of claims 2 and 3, characterized in that the flange (11) is annular and coaxial with the lateral surface (9) .

6. The composite body as claimed in any one of claims 1-5, characterized in that the flange (11) has the shape of a truncated cone.

7. The composite body as claimed in any one of claims 1-6, characterized in that the liner (2) is thin- walled, with a considerably smaller wall thickness than the shell (3) lying outside.

8. The composite body as claimed in claim 7, characterized in that the wall thickness of the shell (3) is 5-15, preferably 8-12, times greater than the wall thickness of the liner (2) .

9. The composite body as claimed in any one of claims 1-8, characterized in that the liner (2) is formed by an annular plate, and in that the annular plate has a corrugated outer periphery, which forms said outer lateral surface (9), and, located directly in front of the latter, a correspondingly corrugated inner periphery (4) .

10. The composite body as claimed in any one of claims 1-9, characterized in that it forms a transmission component (1) for transmitting a turning moment.

11. The composite body as claimed in claim 10, characterized in that it forms a gear housing (1) , the liner (2) having an inner periphery (4) which is arranged to engage in a rotationally locking manner in a disk (5) arranged in it.

12. A gear housing, characterized in that it comprises a composite body as claimed in any one of claims 1-11.

13. A method for production of a composite body, which comprises an annular liner (2) and a shell (3) arranged on the liner, the liner (2) comprising a first material and the shell (3) comprising a second material which has a higher thermal expansion coefficient and a lower melting temperature than the first material, the liner (2) having an outer lateral surface (9) and an outwardly directed end surface (10) extending radially inward from said lateral surface (9), characterized in that the liner (2) comprises a flange (11) which extends axially from the end surface (10) and is arranged radially inside said lateral surface (9) , and in that the shell is cast in one piece on the lateral surface (9) and the end surface (10) and the flange (11) .

14. The method for production of a composite body as claimed in claim 13, characterized in that the liner (2) is placed in and forms part of a casting mold and in that the material which forms the shell (3) is cast in said mold.

15. The method for production of a composite body as claimed in either of claims 13-14, characterized in that the body comprises a gear housing for a power transmission device, the gear housing comprising the liner (2), which is provided with splines and adapted to engage in a rotationally fixed manner with a disk (5) arranged in it, and the shell (3) surrounding the liner (2) .