Abstract:
A method and device for assembling a composite housing fitted with a shaft and at least one associated mounted element are disclosed. The method may include the steps of: arranging the housing in a predetermined position with respect to an actuator; arranging the shaft in a predetermined position with respect to the housing and the actuator; selecting a mounting element to be mounted on the shaft; conveying the mounting element into a predetermined position within the housing; pushing the shaft via the actuator so that the shaft passes successively through an opening of the housing and an opening of the mounting element; and positioning the mounting element in a position adjacent to a heat source for a predetermined duration after the step of selecting the mounting element and prior to conveying the mounting element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to European Patent Application No. 13165768.6, filed Apr. 29, 2013, and International Patent Application No. PCT/EP2014/058123, filed Apr. 22, 2014, both of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a method and a device for assembling a composite housing fitted with a shaft and associated mounted elements. 
       BACKGROUND 
       [0003]    In various fields, notably the automotive field, it is necessary to equip a housing with a rotatable shaft on which have been located a number of mounted elements spaced along its length. In order for the shaft to be rotatably located in bearings arranged in the housing, it is necessary for the shaft to be successively driven through each bearing and each mounted element which has previously been located in position along the path of the shaft. 
         [0004]    In the case of such an assembly intended for an application in the automotive field, the composite housing can comprise a cylinder head cover of an automotive engine, the mounted elements being cam lobes for the operation of associated valve mechanisms in the engine. In addition, other elements such as balancing masses can be mounted in order to ensure vibration-free rotation of the shaft. 
         [0005]    A previously proposed method of assembling a composite housing fitted with a shaft and associated mounted elements is described in document EP 1 155 770 B. In this document, the described assembly process comprises the steps of: arranging the housing in a predetermined position with respect to an actuator, the housing having at least one opening adapted to receive a shaft; arranging the shaft in a predetermined position with respect to the housing and the actuator; selecting an element to be mounted on the shaft within the housing, the element having an opening adapted to receive the shaft; conveying the element into a predetermined position within the housing, and pushing the shaft by means of the actuator so that it passes successively through the opening in the housing and that in the element to be mounted. 
         [0006]    This previously proposed method of assembling a composite housing thus involved locating the elements which were to be mounted on the shaft in predetermined positions corresponding to those they would occupy in the assembled housing, locating the housing around the elements to be mounted on the shaft in a predetermined position corresponding to that it would occupy in the completed assembly, and then pushing the shaft through the openings in the walls of the housing and openings in the elements to be mounted on the shaft, which openings are arranged to be aligned when in the predetermined positions. 
         [0007]    In order to ensure a tight fit of the elements on the shaft once the assembly process has been completed, the elements can be heated to a predetermined temperature prior to assembly. This causes the opening in each element to expand and thus facilitate the passage of the shaft. Subsequent cooling causes the opening to contract and thus fix the mounted elements in position on the shaft. In this previously proposed method of assembling a composite housing fitted with a shaft and associated mounted elements, each element was located in its predetermined position some time before the shaft was driven into its assembled position in the housing. This feature presented the disadvantage that, if the elements were heated in advance of the assembly process, the time necessary to locate each element in its predetermined position, added to that required to locate the housing in its predetermined position relative to the elements to be mounted on the shaft, meant that the previously heated elements would have cooled before the assembly process began. The passage of the shaft through the openings in the elements to be mounted would thus be hindered, slowing the assembly process and possibly causing miss-alignment of the various components. 
       SUMMARY 
       [0008]    It is therefore an object of the present invention to provide a method and a device for assembling a composite housing fitted with a shaft and associated mounted elements in which the aforementioned disadvantages are overcome. 
         [0009]    According to the invention, there is provided a method for assembling a composite housing fitted with a shaft and associated mounted elements which comprises the additional steps of, subsequent to selecting the element to be mounted on the shaft within the housing, and prior to conveying the element into a predetermined position within the housing, holding it in a position adjacent a heat source for a predetermined time; selecting at least one additional element and conveying it into a predetermined position within the housing, said element having an opening adapted to receive the shaft, and, subsequent to selecting the element to be mounted on the shaft within the housing, and prior to conveying the element into a predetermined position within the housing holding it in a position adjacent a heat source for a predetermined time; and pushing the shaft by means of the actuator so that it passes through the opening in the additional element to be mounted. 
         [0010]    By ensuring that each element to be mounted is maintained at a high temperature until its location within the housing, the present invention offers the advantage that the operation to drive the shaft into its assembled position is facilitated. Furthermore, the invention ensures that the risks of the mounted elements being miss-aligned in the assembled positions on the shaft are minimized. 
         [0011]    Preferably, the selected element is heated up to a predetermined temperature prior conveying it into its predetermined position. 
         [0012]    Preferably, the selected element is heated by an induction coil or in a separate oven. 
         [0013]    Preferably, the end of shaft is pushed to a predetermined position with respect to the housing after it passes the opening in the last element to be mounted and is held in this position for a predetermined time. 
         [0014]    According to a second aspect of the invention, there is provided a device for assembling a composite housing fitted with a shaft and associated mounted elements, the device comprising a support for receiving the housing, the housing having at least one opening adapted to receive a shaft, the device further comprising an actuator for pushing the shaft through said opening, at least one locating tool adapted to select at least one associated element to be mounted on the shaft and convey it to a predetermined position within the housing, the device further comprises at least one additional locating tool adapted to select at least one associated element to be mounted on the shaft characterized in that the at least one additional locating tool is moveable with respect to the at least one other additional locating tool. 
         [0015]    Preferably, the locating tools adapted to select an associated element are positioned in a predetermined, non-aligned position relative to each other before conveying the associated elements into their predetermined positions. 
         [0016]    Preferably, the device further comprises a heat source associated with the element to be mounted on the shaft, said heat source being arranged at predetermined point relative to the housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The present invention will now be described by way of example with reference to the accompanying drawings, in which: 
           [0018]      FIG. 1  is a schematic perspective view of a composite housing fitted with a shaft and associated mounted elements, assembled in accordance with the invention; and 
           [0019]      FIGS. 2 to 9  are similar views of the composite housing fitted with a shaft and associated mounted elements at various stages in the assembly process according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  shows a composite housing fitted with a shaft and associated mounted elements which has been assembled using the method of assembly according to the invention. 
         [0021]    The housing  10  which, in the illustrated example, is the cylinder head cover of an engine of a motor vehicle (not shown), comprises first and second end walls  12 ,  14  and at least one intermediate wall  16 . The housing  10  may alternatively be an open frame adapted to form part of a cylinder head of an engine. Additional intermediate walls  16  may be provided in accordance with the dimensions of the housing. In the example shown, a single intermediate wall is provided, arranged to be generally equidistant from the two end walls  12 ,  14 . 
         [0022]    The end walls  12 ,  14  and the or each intermediate wall  16  are fitted with generally annular bearings  18  which are preferably similar and which are together adapted to receive a shaft  20  as will be described herebelow. The shaft  20  is fitted with mounted elements  22 , four in the illustrated example, spaced along its length. In the illustrated example, the mounted elements are cam lobes which, when the housing is mounted upon a vehicle engine and the shaft is caused to rotate, are each adapted to operate an associated valve mechanism (not shown). 
         [0023]    The shaft  20  can project beyond the end walls  12 ,  14  of the housing  10 , preferably equidistantly, as shown, or, alternatively, may have its ends flush with the outer surface of the end walls. 
         [0024]    Other elements  22  can be mounted on the shaft  20 , whether further similar elements to those shown, or additional elements. In the case where the housing is a cylinder head cover of the engine of a motor vehicle the additional elements can comprise balancing masses to ensure vibration-free rotation of the shaft  20 , gear wheels, speed wheels, bearing rings, cams intended to operate pumps, or assembly supports. 
         [0025]    The method of assembling the composite housing fitted with a shaft and its associated mounted elements which is illustrated in  FIG. 1  will now be described with reference to  FIGS. 2 to 9 . 
         [0026]    The first stage of the method of assembling the composite housing fitted with a shaft and its associated mounted elements is shown in  FIG. 2 . The housing  10  has been located on a support (not shown) and has been fitted with bearings  18  but with no other components. The shaft  20  is located outside the housing, with one end  24  adjacent to the end wall  12  and is arranged coaxially with the bearings  18  and is mounted on supports (not shown) so that it is free to be displaced along the line of its longitudinal axis. 
         [0027]    The elements  22  which are to be mounted on the shaft  20  are each taken individually from a supply station (not shown) by an associated locating tool, shown generally  26 . Each locating tool  26  is adapted to select a given element  22  to be mounted on the shaft and convey it to a predetermined position within the housing  10  as will be described in greater detail hereafter. 
         [0028]    In the course of the method for assembling a composite housing fitted with a shaft and associated mounted elements in accordance with the invention, the shaft  20  will be driven, from its position illustrated in  FIG. 2  to that illustrated in  FIG. 1 , progressively through the three bearings  18  as well as through openings (not shown) in the various elements to be mounted on the shaft as will be described hereafter. 
         [0029]    The axial displacement of the shaft  20  is selectively controlled by an actuator  28  which is located adjacent the remote end  30  of the shaft  20 . In the illustrated embodiment, the actuator  28  comprises a hydraulic piston and cylinder in which an increase in internal hydraulic pressure in the cylinder  32  causes the piston  34  to extend and engage the remote end  30  of the shaft  20  and force it axially in the direction of arrow  36  towards the housing  10 . Other types of actuator  28  could of course be envisaged. 
         [0030]    In order to ensure a tight fit of the elements  22  on the shaft  18  once the assembly process has been completed, and in accordance with an aspect of the invention, the elements  22  to be mounted on the shaft  20  are heated to a predetermined temperature prior to assembly and are then maintained at this temperature until they are each conveyed to a predetermined position within the housing  10  by a respective locating tool  26 . By maintaining each element at the predetermined temperature until the moment when it is conveyed by the associated locating tool  26  into its position within the housing  10 , it is ensured that the passage of the shaft through the opening in each element is facilitated while ensuring that, upon cooling at the end of the assembly process, each such element will contract and become immovably fixed to the shaft. To this end, once each element  22  has been taken individually from a supply station by its associated locating tool  26 , it is held in the illustrated ready position adjacent an associated heat source shown generally  36 . Additional heat sources, not shown, are provided for each element  22 . The or each heat source may comprise an induction coil or a separate oven. 
         [0031]    The second stage of the method of assembling the composite housing fitted with a shaft and its associated mounted elements is shown in  FIG. 3 . The actuator  28  has been operated to displace piston  34  and engage the remote end  30  of the shaft  20  in order to drive it axially in the direction of arrow  36  so that end  24  of the shaft  20  is forced into the bearing  18  mounted in end wall  12 . At this point in the assembly process, the locating tools  26  are still in position adjacent their respective heat sources  36 , only one of which is shown. 
         [0032]      FIG. 4  illustrates the next stage in the method of assembling the composite housing in which actuator  28  has driven the end  24  of shaft  20  through the bearing  18  in end wall  12 . At this point, the locating tool  26  associated with the first element  22  to be mounted on the shaft  20  moves it from the ready position of  FIG. 3  adjacent its associated heat source  36  in the direction of arrow  38  towards a predetermined position within the housing  10 . 
         [0033]    The next stage of the method of assembling the composite housing is shown in  FIG. 5 . The first element  22  has been located in its predetermined position within the housing  10 . In this position, locating tool  26  engages with positioning lugs on the inner surface of the housing  10  (not shown) in order to retain it in position when subjected to loads in the direction of arrow  36 . As the shaft  20  is forced further through the bearing  18  towards a position in which it will engage an opening  40  in element  22 , the second locating tool  26  associated with the second element  22  to be mounted on the shaft  20  moves it from the ready position of  FIG. 5  adjacent its associated heat source  36  in the direction of arrow  38  towards its predetermined position within the housing  10 . 
         [0034]    As shown in  FIG. 6 , the shaft  20  has been driven through the opening  40  of the first element  22  and is about to engage a similar opening in the second element. At this point, the third locating tool  26  associated with the third element  22  to be mounted on the shaft  20  moves it from the ready position of  FIG. 6  adjacent its associated heat source  36  in the direction of arrow  38  towards its predetermined position within the housing  10 . As with the previous locating tools, in this position, locating tool  26  engages with positioning lugs on the inner surface of the housing  10  (not shown) in order to retain it in position when subjected to loads in the direction of arrow  36 . The other locating tools remain in their located positions in order to maintain their associated element  22  in position while the shaft  20  continues to advance through the housing. 
         [0035]    The method of assembling the composite housing continues in a similar manner until it reaches the position shown in  FIG. 7 . In this position all four elements  22  have been located in their predetermined positions by their respective locating tools  26 . Shaft  20  has been driven by piston  34  of actuator  28  in the direction of arrow  36  until it has traversed the first three elements  22  and is about to engage the opening  40  of the final element  22 . 
         [0036]    In  FIG. 8  is shown the position of the shaft  20  once it has been driven through the openings  40  in all the elements  22  in their predetermined positions inside the housing  10 . The end  24  of shaft  20  is about to engage with the interior of the final bearing  18  located in end wall  14  of housing  10 . 
         [0037]    The final position of the shaft  20  is shown in  FIG. 9 . In this position, the end  24  of shaft  20  has been driven by the actuator  28  through the bearing  18  in end wall  14  of the housing  10  and a predetermined distance beyond the end of wall  14 . In this position, end  30  of shaft  20  projects a generally equal distance beyond end wall  12  of housing  10  in a similar way to that shown in  FIG. 1 . In this position, additional components, for example, drive wheels or balancing elements (not shown) can be mounted on the free ends  24  and  30  of the shaft  20 . Once the position illustrated in  FIG. 9  has been reached, the locating tools  26  can be removed and the completed housing can be conveyed to a subsequent assembly point. 
         [0038]    From the position of the housing, the actuator and the shaft shown in  FIG. 2  to that shown in  FIG. 9 , the shaft  20  is in continuous movement. The actuator is arranged to advance the shaft, preferably at a constant speed, and the locating tools  26  are controlled so that they deliver their associated elements  22  in such a way and at such a time that they are in position within the housing  10  when the end  24  of the shaft  20  reaches them. 
         [0039]    At the end of the assembly process, the shaft has reached a pre-determined position with respect to the housing and the completed housing is left immobile for a predetermined time in order to allow the various components to cool and so become fixed in their positions on the shaft. 
         [0040]    It is further envisaged that the bearings  18  in the walls  12 ,  14  and  16  of the housing  10  be heated immediately prior to the commencement of the assembly process in order to facilitate the passage of the shaft  20 . 
         [0041]    The speed of advance of the actuator and the shaft  20  is optimized as a function of the delivery of the elements  22  by their associated locating tools  26 : the shorter the time required to locate each element  22  in its predetermined position, the faster the speed of advance of the shaft. Clearly, a high speed of advance of the shaft  20  is desirable as it will ensure that the bearings  18 , if heated, and the elements  22  will remain at a high temperature throughout the assembly process, thus facilitating the advance of the shaft therethrough. 
         [0042]    Preferably, the locating tools  26  adapted to select an associated element are positioned in a predetermined, non-aligned position relative to each other before conveying the associated elements into their predetermined positions.