WO2005092600A1

WO2005092600A1 - Metal-plastic composite part having compensation for shrinkage

Info

Publication number: WO2005092600A1
Application number: PCT/EP2005/050443
Authority: WO
Inventors: Hans-Juergen Oberle
Original assignee: Robert Bosch Gmbh
Priority date: 2004-03-24
Filing date: 2005-02-02
Publication date: 2005-10-06
Also published as: DE102004014363A1

Abstract

The invention relates to a composite part comprising a metal element (2) and a plastic element (3). The metal element (2) has a contact surface (8a, 8b, 8c), and the plastic element (3) has a contact surface (3c, 3d, 3e). The contact surfaces of the metal element and of the plastic element are situated opposite one another and form a contact area between the metal element and the plastic element. The contact surface (8a, 8b, 8c) of the metal element and the contact surface (3c, 3d, 3e) of the plastic element are situated at an angle (α, β, δ) to at least one direction of shrinkage (R, A, T).

Description

Metal-plastic composite part with shrinkage compensation

State of the art

The present invention relates to a metal-plastic composite part according to the preamble of claim 1.

Composite parts, comprising a metal element and a plastic element, are known from the prior art. If the plastic element is to be injection molded onto the metal element, the problem arises with such composite parts that after the plastic element has solidified, the plastic element shrinks. This results in problems on the one hand with regard to the external dimensions of the plastic element and, on the other hand, also problems in the connection area between the metal and the

Plastic element. In particular, a gap can occur between the plastic element and the metal element after the plastic element has solidified. As a result, play can occur between the two elements of the composite part, which, for example when used as a toothed wheel, can lead to undesirable noise development. Furthermore, when the direction of rotation changes, an impact can occur between the metal and the plastic element. Another problem with the shrinkage of the Plastic element can occur if a tension is introduced into the plastic element due to the shrinkage. These tensions can lead to premature fatigue of the plastic element, so that such composite parts can only have a short service life.

Advantages of the invention

A composite part according to the invention with the features of claim 1 has the advantage that it can provide a play-free and tension-free metal-plastic connection. According to the invention, the influences of the shrinkage of the plastic part are used for this. For this purpose, the metal element and the plastic element of the composite part each have a contact surface, the contact surfaces of the two elements lying opposite one another and forming a contact area between the metal element and the plastic element. Here, the contact surfaces of the metal element and the plastic element are arranged at an angle to at least one direction of shrinkage of the plastic element. The shrinkage direction of the plastic element can be axial, radial or tangential or in the circumferential direction. Due to the shrinkage of the plastic element there are nevertheless areas (gaps) between the metal element and the plastic element, which, however, have no effects due to the contact between the two elements on the contact surfaces inclined to the directions of shrinkage. If extreme loads such as a hard stop on the composite part can be initiated due to the

Elasticity of the plastic allows a small relative movement between the plastic element and the metal element due to the gaps, so that the plastic element comes into contact with the metal element somewhat delayed and thus damping the hard stop is feasible. Thus, on the one hand, an improved noise behavior and, on the other hand, a better durability of the composite part is achieved.

The subclaims show preferred developments of the invention.

The contact area between the metal and the plastic element is preferably formed by tapering areas on the two elements. As a result, especially if the composite component is a rotating part, such as e.g. is a gear, a play and tension-free metal-plastic connection can be realized in both directions of rotation.

In order to avoid play in all directions between the metal element and the plastic element, the metal element and the plastic material element each have at least one contact surface at an angle to the radial, axial and tangential direction of the composite part. In other words, there are at least three contact surfaces on the metal and plastic element, which are not arranged parallel to one another.

The angle between the contact surface of the metal element and a direction of shrinkage and the angle between the contact surface of the plastic element and the direction of shrinkage are preferably the same. As a result, the contact area between the metal element and the plastic element can be formed not only as a line but as a surface.

The composite part is preferably a gearwheel, the plastic element being arranged inside the gearwheel and has a through opening for receiving a shaft or the like. In order to enable a rotationally fixed connection between the through opening and the shaft, the through opening is designed, for example, as a square or an internal toothing is provided on the through opening and the shaft is designed in each case in accordance with the shape of the through opening. In order to be able to insert the shaft into the through opening, a small amount of play must be provided between the two elements.

In order to also obtain a play-free connection between the shaft and the plastic element, the through opening in the plastic element preferably has a region that tapers in the axial direction of the composite part.

The plastic element further preferably has a collar which has a larger diameter than an inner diameter of the metal element. Axial securing of the plastic element on the metal element can thereby be obtained.

The contact area between the metal element and the plastic element is preferably formed by two mutually opposite and converging areas. The two regions converging towards one another particularly preferably have the same angle relative to a direction of shrinkage of the plastic element, only the signs of the angles being different.

The metal element of the composite part is particularly preferably produced by means of sintering and the plastic element is injection-molded onto the metal element. A composite part according to the invention is preferably used as a gear in an electrical machine, in particular on the output. As a result, a large variety of variants can be obtained by means of the composite part according to the invention, since only a different plastic element can be injection molded onto a predetermined standardized metal element, which can be designed in accordance with an output shaft. This can be achieved, for example, simply by changing inserts in the plastic injection mold using the same insert made of metal. By using the plastic, the noise level at the output area of the electrical machine can be further improved. The electrical machine is particularly preferably an electric motor which is used in a vehicle. For example, electric motors of this type can be used in vehicles for adjusting seats and / or backrests and / or other devices in the interior of the vehicle, in which special requirements with regard to low noise of the electric motor are required.

drawing

A preferred embodiment of the invention is described below with reference to the accompanying drawings. In the drawing is:

FIG. 1 shows a schematic sectional view of a composite part designed as a gearwheel according to an exemplary embodiment of the present invention,

FIG. 2 shows a detailed sectional view of the gearwheel shown in FIG. 1, Figure 3 is a side view of the composite part from the left in Figure 2 and

FIG. 4 shows a partial sectional view along the line C-C in FIG. 2.

Description of the embodiment

As shown in particular in FIG. 1, a composite part 1 according to the invention comprises a metal element 2 and a plastic element 3. The plastic element 3 is essentially tubular and is arranged in a through opening of the metal element 2. In the plastic element 3 there is also a through opening 4, which in this exemplary embodiment has a

Cross-section in the form of a square (see FIGS. 3 and 4). A toothing 5 is provided on an outer circumference of the metal element 2, so that the composite part 1 shown in the exemplary embodiment is a gearwheel for an electric motor. In the

Through opening 4 of the plastic element 3, a shaft 6 can be introduced (see FIG. 2), via which the power of the electric motor can be delivered.

According to the invention, a play-free connection is now formed between the metal element 2 and the plastic element 3, which can in particular compensate for any shrinkage of the plastic element after the injection molding onto the metal element 2. In Figures 2, 3 and 4, the shrinkage is exaggerated to better illustrate the invention. Figure 2 is a section along the line AA of Figure 3. As can be seen from Figure 2, the shrinkage between the metal element 2 and the plastic element occurs in the radial direction R, in the axial direction A and in the tangential direction or Circumferential direction T on. As shown in FIG. 2, this results in a shrinkage SR along the outer circumference of the plastic element 3 and a shrinkage SA in the axial direction. As shown in FIG. 2, the shrinkage SA occurs both on the left and on the right side of the plastic element 3. Due to the radial shrinkage SR, there is an annular gap between the metal element 2 and the plastic element 3, due to which, in the prior art, noise can occur during operation. Furthermore, in the prior art, stresses in the plastic element can occur due to the axial shrinkage, since the plastic element contracts in the axial direction and thus a tension occurs between its axial stops. The tangential shrinkage ST can be seen in FIGS. 3 and 4.

According to the invention, contact surfaces are therefore provided on the metal element 2 and on the plastic element 3, which are arranged at an angle to at least one direction of shrinkage R, A and T. In the left part of Figure 2 is the

Contact area K between the metal element 2 and the plastic element 3 is shown. Here, a contact surface 8a is provided on the metal element 2, which is arranged at an angle α to the axial direction of shrinkage A. A surface 3c is also arranged on the plastic element 3 at an axial end, which due to the shrinkage is arranged at a somewhat larger angle than the angle α to the axial shrinkage direction A (cf. FIG. 2). It should be noted that after the spraying, the angle of the metal element and the angle of the plastic element are initially the same, since the plastic initially lies directly against the metal contour during spraying. The larger angle results from the shrinkage of the plastic element. This results in a contact area K between the metal element and the Plastic element. As can be seen from FIG. 3, there are four arcuate contact areas K. It should be noted that the areas 8a and 3c can also be conical areas, so that the contact area would be a circle. This measure can thus be used to prevent

Occurrence of shrinkage on the plastic element 3, rattling or similar noises occur between the plastic element 3 and the metal element 2, since the shrinkage is compensated for by the fact that the contact area K lies further inward in the composite part in accordance with the shrinkage in the axial direction A.

At the right end of the plastic element 3 shown in FIG. 2, projecting areas 3b are formed on the cylindrical main area 3a. This

Areas 3b serve as axial securing of the plastic element on the metal element. The protruding regions 3b are arranged in recesses 7 formed in the metal element 2. In Figure 4, this axial securing is shown in detail on a protruding area 3b. FIG. 4 shows a partial sectional view along the line C-C of FIG. 2. A total of four projecting regions 3b are provided, each of which is inserted into correspondingly formed recesses 7. The recesses 7 have at their ends in the circumferential direction contact surfaces 7a and 7b which are arranged at an angle β to the radial direction of shrinkage R (cf. FIG. 4). Contact areas 3f and 3g are also provided on the protruding areas 3b, which due to the shrinkage are at a somewhat larger angle than the angle β to the radial

Shrinkage direction R are arranged. The surfaces 7a and 7b or 3f and 3g taper towards one another. If a shrinkage occurs in the radial direction R and / or in the tangential direction T after the hardening of the plastic, a contact area K between the surfaces 7a and 3g or 7b and 3f is placed further towards the center of the plastic element 3, so that there is no play between the two elements 2 and 3 is present. Therefore, the occurring at the plastic element 3 shrinkage has no effect on the connection between the metal member 2 and the plastic element 3. The shrinkage in the tangential direction, in figure 4 b on the basis of the width _M of the recess in the

Metal element and the width b _{k of} the plastic element can be recognized after the shrinkage. In Figure 4, the shrinkage SR is drawn in relation to the length X _{3 of} the contact surfaces 3f, 3g and 7a, 7b of the plastic or metal element. The length X ₃ must always be greater than the maximum shrinkage that occurs in order to ensure a contact area between the plastic element 3 and the metal element 2.

FIG. 3 shows a left side view of the composite part 1 from FIG. 2. As can be seen from FIG. 3, four projecting areas with contact surfaces 3 c are also provided in order to compensate for any shrinkage that may occur on the plastic element 3. The protruding areas of the plastic element 3 are arranged in recesses 8 of the metal element 2. Here is between one

Radial direction R and the tapered areas 8b and 8c provided an angle δ. The shrinkage SR in the radial direction is again smaller than a length X _{2 of} the surfaces 8b and 8c in the radial direction. The shrinkage ST in the tangential direction can be recognized on the basis of the maximum width b _{M of} the metal part relative to the width b _{κ of} the hardened plastic element 3. Thus, the four projections formed on the plastic element 3 can shrink in the radial direction R, axial direction A and tangential direction Compensate T, the three surfaces 8a, 8b, 8c and 3c, 3d, 3e are provided.

The composite part according to the invention can thus be used to achieve zero-backlash compensation between the metal and the plastic element. The choice of the different angles of the contact surfaces of the metal element or of the plastic element relative to a direction of shrinkage thus results in linear contact areas K. This also enables the

Damping properties of the composite element, especially under extreme loads, such as hard stops in the system can be improved, since a small relative movement between the plastic element and the metal element is possible. The angle α, which defines the inclination of the contact surface 8a relative to the axial direction of shrinkage A, can be determined as follows:

tanα> dl - (dl -dY) '2 - SA

where dl is the diameter of the plastic part before the shrinkage, dl 'is the diameter of the plastic part after the shrinkage and SA is the shrinkage of the plastic part in the axial direction.

The other angles β and δ can also be determined in a corresponding manner.

Since in this exemplary embodiment the angles of the contact surfaces of the metal element are different from those of the plastic element, there are always linear contact areas K. In this exemplary embodiment, conical surfaces 4a are also formed on the passage opening 4. Since the shaft 6 is a square shaft, four surfaces 4a 5 inclined to the axial direction A are accordingly provided. At the end of the shaft 6 there are also four surfaces 6b inclined to the axial direction A, which are formed at the end of the main region 6a of the shaft 6. As a result, a play-free connection between the shaft 6 and the plastic element 3 can still be obtained.

L0 An angle δ is formed between the surface 4a and the axial direction A and the angle between the surface 6b of the shaft and the axial direction is again somewhat larger, so that again linear contact areas between the shaft 6 and the

L5 plastic element 3 result.

It should also be noted that it is also possible to replace the contact area shown on the left in FIG. 2 at the other end of the composite part

10 recess 7 and the projecting element 3b. However, since the metal element 2 is preferably produced in the sintering process, it is advantageous in terms of production technology if the conical regions are only attached to one end of the composite part and to the other end of the in

-5 Figure 2 area shown on the right side is provided for axial securing. As a result, the composite part according to the invention can be produced particularly inexpensively without reworking.

Claims

Expectations

1. Composite part comprising a metal element (2) and a plastic element (3), characterized in that the metal element (2) has a contact surface (8a, 8b, 8c) and the plastic element (3) has a contact surface (3c, 3d, 3e ), the contact surfaces of the metal element and the plastic element lying opposite one another and forming a contact area (K) between the metal element and the plastic element, and wherein the contact surface (8a, 8b, 8c) of the metal element and the contact surface (3c, 3d, 3e) of the plastic element are arranged at an angle (α, β, δ) to at least one direction of shrinkage (R, A, T) of the plastic element.

2. Composite part according to claim 1, characterized in that at least one contact area (K) between the metal element (2) and the plastic element 3 is formed by tapering areas on the metal element (2) and on the plastic element (3).

3. Composite part according to one of the preceding claims, characterized in that the metal element (2) and the plastic element (3) each have at least one Have contact surface at an angle (α, ß, δ) to the radial, axial and tangential direction (R, A, T) of the composite part.

4. Composite part according to one of the preceding claims, characterized in that the angle (α, β, δ) of the contact surface of the metal element (2) and the angle of the contact surface of the plastic element (3) is the same.

5. Composite part according to one of the preceding claims, characterized in that the plastic element (3) is arranged within the metal element (2) and has a through opening (4) for receiving a shaft (6).

Composite part according to claim 5, characterized in that the through opening (4) on the plastic element (3) has a region (4a) which tapers in the axial direction of the composite part.

7. Composite part according to one of the preceding claims, characterized in that the plastic element (3) has a projecting area (3b) for axial securing in the metal element, the projecting area (3b) having a larger diameter than an inner diameter of the metal element (2) ,

8. Composite part according to one of the preceding claims, characterized in that the contact area (K) between the metal element (2) and the plastic element (3) is formed by two mutually opposite and converging areas.

9. Composite part according to one of the preceding claims, characterized in that the composite part is a gear.

10. Electrical machine comprising a composite part according to one of the preceding claims.