Abstract:
The invention relates to a method for producing a cooling body made of a good heat-conducting metal material, comprising the following steps; placing the metallic material ( 310 ) between a first die ( 315 ) and a second die ( 320 ), the dies are pressed against each other such that the metallic material adapts to the shape of the dies, the dies are separated from each other and the cooling body ( 100 ) is demoulded from the dies.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a cooling body and a method for producing the cooling body. The invention particularly relates to a cooling body on an electrohydraulic unit. 
       TECHNICAL FIELD 
       [0002]    A cooling body has the task of absorbing heat from an element to be cooled and releasing said heat to an ambient medium. As a result, a material having a high level of thermal conductivity, such as aluminum or copper, is generally used for the cooling body. 
         [0003]    A mass production of aluminum cooling bodies, in particular those in the form of which are adapted to a predetermined application, usually involves a die casting process. In such a process, heated aluminum in the liquid or pasty state is pressed under pressure into a preheated steel mold. After the aluminum has cooled, the cooling body can be removed from the mold. In so doing, the mold is exposed to considerable thermal stress so that said mold has to be replaced after a number of cooling bodies have been produced. The die casting process furthermore requires an extensive process control. In addition, the high-pressure die casting of aluminum is limited to the cold-chamber die casting process. Moreover, only certain alloys of aluminum are suited to aluminum high-pressure die casting and it can be difficult to produce the steel mold such that the workpiece has the appropriate degree of shrinkage after cooling. 
         [0004]    For certain applications, it is necessary to produce a specially molded cooling body. In order to cool an electrohydraulic actuator, for example to actuate a brake or a clutch, a cooling body can, for example, be required which can transport a considerable amount of waste heat, which accrues, for example, at electronic power components of an engine control system. If the electrohydraulic actuator is used in a safety related system, for example the braking system of a vehicle, the cooling body must also be designed such that the efficiency of the actuator is also ensured under unfavorable conditions. In addition, the cooling body at the actuator can also be used as a structural component which ensures a mechanical protection of the aforementioned electronic components. The cooling body can particularly be configured in the form of a housing cover, which, for example, is disposed in the axial extension of an electric motor. 
       SUMMARY OF THE INVENTION 
       [0005]    The aim of the present invention consists of specifying a cooling body and a method of production for the cooling body which are adapted to the needs of an electrohydraulic actuator, in particular on board of a motor vehicle. 
         [0006]    A cooling body according to the invention comprises a lower section having a contact surface for absorbing heat from an element to be cooled and an upper section comprising an upwardly extending projection for transferring heat to an ambient medium, wherein the cooling body is produced from a good heat-conducting metal material by means of impact extrusion. 
         [0007]    During impact extrusion of a component, in contrast to a die casting process, the metal material is brought to flow into a die by means of high pressure rather than heat. In so doing, the material begins, in a metallurgical sense, to flow without being heated into the range of the melting temperature thereof. As a result, the impact extrusion can also be carried out at room temperature. The temperatures reached during such a process fatigue the tool, particularly the die, to a lesser extent; thus enabling the die to be used over a longer production period or, respectively, for an increased number of pieces. The metal material can particularly comprise a good ferrous material or a non-ferrous material, wherein a good conductivity of the material is advantageous. In a preferred manner, the metal material comprises aluminum as a non-ferrous metal. 
         [0008]    Because a cooling process is not required for the workpiece, a higher rate of production can be achieved with the impact extrusion process than with, for example, high-pressure die casting. Impact extrusion can furthermore ensure a high degree of dimensional accuracy of the cooling body. A surface quality of the impact extruded cooling body can be so high that a post-processing of the workpiece can be omitted. In addition, the impact extrusion process tends only slightly to form ridges and cavities (cast hollow spaces). 
         [0009]    The contact surface of the cooling body preferably bears a profile. The profile can be provided during the same operation as for the rest of the cooling body and can facilitate the use of a thermal paste or a thermal pad. Heat of an object to be cooled, in particular an electronic component, can thus be better released to the cooling body. 
         [0010]    The projection can have the shape of a conical section. As a result, a relatively large surface can be combined with a good stability of the projection. 
         [0011]    In another embodiment of the invention, the projection has the shape of a cylinder. The durability of the projection can be further increased by means of the cylindrical shape. In still a further embodiment of the invention, the projection can also be cuboid-shaped, wherein one of the dimensions of the cuboid is preferably small with respect to the other dimensions. 
         [0012]    The cuboid-shaped projection can particularly form a large surface area at a low volume. 
         [0013]    In a preferable manner, a plurality of projections is provided, wherein projections having different shapes can be combined with one another. 
         [0014]    In one embodiment of the invention, the cooling body has a substantially circular base area. As a result, the cooling body is particularly suitable for installation in the axial extension of a cylindrical electric motor. 
         [0015]    A cuboid-shaped projection can particularly extend in the radial direction. A plurality of cuboid-shaped, radial projections can be formed as a type of annulus around the geometric center of the cooling body. 
         [0016]    In a further preferred embodiment of the invention, the lower section of the cooling body has a planar sealing surface for engagement with a seal. As a result, the cooling body can, for example, be used as an axial closure of a housing. On account of the impact extrusion process, the sealing surface can have a high quality without a post-processing step. 
         [0017]    In one embodiment of the invention, a retaining element is provided on the upper section for engaging a hook element which is designed to press the cooling body downwards. By means of the hook element, the cooling body can be provided for a screwless mounting, for example, on the aforementioned electrohydraulic actuator. A post-processing step for the impact extruded cooling body, for example for inserting a screw thread, can be omitted. The cooling body can therefore be configured for a cost effective and simple installation. 
         [0018]    A method according to the invention for producing a cooling body, in particular the cooling body mentioned above, made of a good heat-conducting metal material comprises the following steps: placing the metallic material between a first die and a second die, pressing the dies against each other such that the metallic material adapts to the shape of the dies, separating the dies from each other and demolding the cooling body from the dies. The metal material preferably comprises aluminum. 
         [0019]    By producing the cooling body in an impact extrusion process, the features of the cooling body mentioned above can be advantageously formed. The method allows for a cost effective production of the cooling body, in particular in large quantities. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The invention is now described in greater detail with reference to the attached drawings. In the drawings: 
           [0021]      FIG. 1  shows a cooling body for an electrohydraulic unit; 
           [0022]      FIG. 2  shows the cooling body from  FIG. 1  from a different perspective, and 
           [0023]      FIG. 3  shows a flow diagram of a method for producing the cooling body of the  FIGS. 1 and 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 1  shows a cooling body  100  for an electrohydraulic unit. The cooling body  100  is particularly designed to axially close off an electric motor of the electrohydraulic unit. An element to be cooled by the cooling body  100  can, for example, be an electronic component which is axially disposed between the cooling body  100  and the electric motor. The cooling body  100  has, in the depiction of  FIG. 1 , a substantially circular base area, from which an upper section  110  and a lower section  115  extend in the axial direction. One or a plurality of contact surfaces  120  is configured on the lower section  115  for engaging the element  105 . At least one of the contact surfaces  120  preferably bears a profile  125 . The profile  125  can, for example, comprise one or a plurality of grooves which are introduced axially into the lower section  115  in the region of the contact surfaces  120  in a grid- or diamond-shaped manner. The lower section  115  can also have a recess  130  which is introduced in the axial direction of the upper section  110 . By means of the recess  130 , space can be made available for an element lying in the proximity of the cooling body  100 , in particular an electrohydraulic actuator. The recess  130  can also be entirely or partially delimited by a contact surface  120 , against which an element to be cooled  105  can rest. One or a plurality of other contact surfaces  120  can be disposed away from the upper section  110  in the axial direction. 
         [0025]    In one embodiment of the invention, a planar sealing surface  135  is provided on the lower section  115 , which is provided for engagement with a seal, for example made from rubber, plastic or paper. The sealing surface  135  preferably encompasses an area of the lower section  115  or, respectively, the base area of the cooling body  100 . In the embodiment depicted, in which the cooling body  100  has a substantially circular base area, it is preferred that the sealing surface  135  runs in a radially outer region. 
         [0026]    The lower section  115  can bear one or a plurality of extensions  140  which extend away from the upper section  110  in the axial direction. The extensions  140  can keep the cooling body  100  from twisting by virtue of the fact that they are designed to engage in corresponding grooves of a component, to which the cooling body  100  is to be attached. In a preferred manner, the cooling body  100  can, for example, be mounted in only one rotatory position, for example on a housing. A web  145  can be provided in one exemplary embodiment, which passes around the outside of the base area at least in some sections. In so doing, the cooling body  100  can be placed in a cup-like manner over a proximate element and be mounted to the same. 
         [0027]    The cooling body  100  is designed to be demolded from the dies in the axial direction, as is described below in greater detail with reference to  FIG. 3 . To this end, it is preferred that the cooling body  100  does not have any undercuts. It is furthermore preferred that delimiting structures of the cooling body  100  do not extend exactly in the axial direction but rather slightly obliquely thereto to the greatest possible extent. 
         [0028]      FIG. 2  shows the cooling body  100  from  FIG. 1  in a view from the upper section  110 . One or a plurality of projections  205  extend axially in a direction away from the lower section  115 . The projection  205  can assume different forms. In a preferred embodiment, a multiplicity of projections  205  is provided which can have the same or different shapes. A first projection  210  can, for example, have the shape of a conical section. A cone that is rounded off at the top or, respectively, a frustum comprising a convex top surface is preferred in this case. A second projection  215  has the shape of a cylinder. A third projection  220  is cuboid-shaped. A multiplicity of third projections  220  is disposed on a periphery about a geometric center of the circular base area of the cooling body  100 , wherein the cuboids are oriented in a radial direction. An annulus of third projections  220  is thereby formed in a radial outer region of the cooling body  100 . A retaining element  225  for engaging a hook element is preferably provided, which is designed to press the cooling body  100  downwards, i.e. in the direction of the lower section  115 . The hook element can, for example, comprise a spring clip, a hook plate or a spring wire. 
         [0029]    The upper section  110  is also designed to be demolded from a die. For that reason, delimiting structures that extend axially are also preferably omitted here if possible. 
         [0030]      FIG. 3  shows a flow diagram of a method for producing a cooling body, in particular those of  FIGS. 1 and 2 . 
         [0031]    In a first step  305 , a metallic material  310  is placed between a first die  315  and a second die  320 . The aluminum material  310  can comprise pure aluminum or a suitable alloy. The aluminum can, for example, be alloyed with silicon, copper, manganese or iron. The dies  315  and  320  are preferably made from steel. The first die  315  has a mold which corresponds to the negative mold of the upper section  110 , and the mold of the second die  320  corresponds to the negative mold of the lower section  115 . 
         [0032]    In a following step  325 , the dies  315  and  320  are pressed under high pressure against one another. The pressure exerted by the dies  315  and  320  on the metallic material  310  is so great that the metallic material  310  begins to flow in a metallurgical sense without being heated into the range of the melting temperature thereof. This process is also known as cold extrusion. In said process, the metallic material  310  adapts to the shape of the dies  315  respectively  320  so that the cooling body  100  is formed. 
         [0033]    In a following step  330 , the dies  315  and  320  are separated from each other, wherein the cooling body  100  is usually demolded from at least one of the dies  315 ,  320 . 
         [0034]    In a concluding step  335 , the cooling body  100  is completely demolded so that said body is free from both dies  315 ,  320 . A cooling process of the cooling body  100  is usually not required and said cooling body  100  can immediately be further processed. A surface processing of the cooling body  100  is usually no longer required because the extrusion process can ensure a high degree of dimensional accuracy and high quality surfaces. The dies  315  and  320  are immediately ready for the method to be rerun with a new metallic material  310 .