Transmission and method for producing such a transmission

A transmission includes a housing made from a metallic material and is provided with a cooling structure in the form of a cooling element made from open-cell metal foam. The cooling element can be secured on the housing, in particular on an outer surface of the housing, by a screw connection and/or adhesive bonding and/or magnetically.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of European Patent Application, Serial No. 18195645.9, filed Sep. 20, 2018, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates to a transmission and to a method for producing such a transmission.

A crucial factor in the transmission engineering sector involves dissipation of heat, generated in the transmission, from the transmission housing so as to ensure proper operation of the transmission for an extended period. For this purpose, the transmission can be provided with an active cooling device. As an alternative or in addition, a passive cooling system can be provided by increasing a housing surface area through the provision of cooling structures in the form of cooling fins, for example. However, housings with such cooling fins become very expensive when compared with housings without cooling fins. Moreover, the formation of cooling fins is associated with a relatively large increase in the dead weight of the housing, which is undesirable in many cases.

It would therefore be desirable and advantageous to provide an improved transmission which obviates prior art shortcomings and which can be produced in a simple and low-cost manner while still being reliable in operation and enabling flexible adjustment of the cooling capacity to suit any demand.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a transmission includes a housing made from a metallic material and including a cooling structure, the cooling structure including a cooling element made from open-cell metal foam and secured on the housing.

According to another advantageous feature of the present invention, the cooling element can be secured on an outer surface of the housing.

In the following description, the reference to “a cooling element” should not be limited to the presence of a single cooling element but is used in a generic sense and the principles described in the following description with respect to a cooling element are equally applicable to the presence of any number of such cooling elements.

A significant advantage of providing cooling elements made from open-cell metal foam over conventional cooling fins resides in a significantly larger surface area and improved cooling capacity associated therewith. Moreover, such cooling elements made from open-cell metal foam have a lower dead weight than cooling fins, so that the housing of a transmission according to the invention can be made lighter than a housing with cooling fins while still maintaining a comparable cooling capacity. Another advantage associated with the use of separate cooling elements made from open-cell metal foam is that the cooling elements can be secured later on to suit a demand at hand, for example a housing manufactured by casting. This allows simple and flexible adjustment of the cooling capacity to the demand at hand. In particular, such retrofitting of cooling elements makes it possible to achieve a wide range of cooling capacities on the basis of a standard housing, and this allows low-cost series manufacture when housings of essentially same design with different cooling capacity are required.

According to another advantageous feature of the present invention, the cooling element can be made of aluminum or copper. Using aluminum and copper has the benefits of good thermal conductivity, while at the same time being of low weight.

According to another advantageous feature of the present invention, the cooling element can have a plate-shaped configuration. This allows simple and flexible handling. For example, the shape of the underside can be matched to the shape of a region of the outer surface of the housing. Thus, the cooling element can have an underside in the form of a circular ring segment to enable its simple securement on a housing, the outer surface of which is likewise in the form of a circular ring segment, at least in one region thereof.

According to another advantageous feature of the present invention, an intermediate layer containing silicone and thermally conductive particles can be provided between the cooling element and the housing. This is advantageous especially when the surface of the housing on which the cooling element is to be arranged is uneven, as is often the case when the housing is produced by casting, for example.

According to another advantageous feature of the present invention, the cooling element can be secured on the housing by a screw connection and/or adhesive bonding. This allows very simple mounting of the cooling element on the housing. As an alternative or in addition, the cooling element can be secured on the housing by a magnet.

According to another aspect of the present invention, a method for producing a transmission includes securing on a housing made from a metallic material a cooling element made from open-cell metal foam to provide a cooling structure on the housing.

According to another advantageous feature of the present invention, an intermediate layer containing silicone and thermally conductive particles can be provided between the cooling element and the housing. As a result, irregularities in the housing surface in particular can be compensated.

According to another advantageous feature of the present invention, the cooling element can be secured on the housing by a screw connection and/or adhesive bonding and/or magnetically.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to the drawing, and in particular toFIG. 1, there is shown a schematic perspective view of a transmission according to present invention, generally designated by reference numeral1. In the non-limiting example shown here, the transmission1is embodied as a spur gear transmission configured as a bevel-and-spur gear train. However, it will be understood that the principles described in the following description with respect to the transmission1are equally applicable to any other type of transmission and the specific type of transmission is of no significance for the present invention.

The transmission1has a housing2, which is divided into a housing top part2aand a housing bottom part2b. In the present case, the housing top part2aand the housing bottom part2bare of symmetrical construction and can be cast in a same die, although this is not obligatory. The transmission1furthermore includes an input shaft3, via which the driving power enters the transmission1, and an output shaft4, which can be connected to a system (not illustrated), e.g. a conveyor belt system. Cooling structures in the form of a plurality of cooling elements5are arranged on the outside of the housing2, with each cooling element5being made from open-cell metal foam and secured as a separate component on the housing2. In the present case, each of the cooling elements5has a plate-shaped configuration and is manufactured from aluminum.

Provided between each of the cooling elements5and the housing2is an intermediate layer6which contains silicone and thermally conductive particles and is generally referred to as a “gap filler”. By way of example, the cooling elements5are secured here on the housing2using screws7. As an alternative or in addition, however, the cooling elements5can also be secured by adhesive bonding and/or using magnets. In the latter case, the cooling elements5, of course, must be provided with corresponding magnets, which are not illustrated here.

To produce the housing illustrated hi MG.1, the transmission1is assembled hi known manner in a first step. In a further step, the separate cooling elements5are then positioned and secured on an outer surface of the housing2. Here, the number and position of the individual cooling elements5can be chosen according to a desired cooling capacity. In order to ensure good thermal coupling of the cooling elements5to the housing2, despite the presence of uneven outer surface of the housing2produced by casting, an intermediate layer6which compensates irregularities in the outer surface of the housing2is positioned between each of the cooling elements5and the housing2.

A significant advantage of a transmission1according to the present invention over a conventional transmission of same construction but provided with cooling fins is that the transmission1according to the present invention has a lower dead weight as a result of the use of cooling structures in the form of one or more cooling elements5. Moreover, the production of the housing2or of the housing top and bottom parts2a,2bby casting is significantly cheaper due to the absence of cooling fins. Another advantage relates to the cooling capacity of the transmission1, which cooling capacity is realized by the presence of cooling elements5and can be adjusted in a manner which is flexible and best suited to the demand at hand through suitable choice of shape, number and position of the cooling elements5. Thus, it is also possible to provide transmissions of same construction with different cooling capacities using housings2of the same construction, so that series manufacture becomes much easier.

Although the invention has been illustrated and described more specifically in detail by means of a preferred illustrative embodiment, the invention is not restricted by the examples disclosed, and other variations can be derived by a person skilled in the art without departing in any way from the spirit and scope of the present invention. Thus, the cooling elements5can have a configuration that differs from a plate shape. It is also possible for the underside of the cooling elements5to be matched to a shape of the housing outer surface. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.