Abstract:
This invention relates to a housing, preferably but not exclusively for use with a motor vehicle heater of the type employed to heat the passenger compartment of the motor vehicle. The housing has a unitary housing body formed by blow moulding and a structural frame is formed by injection moulding. The structural frame bears the load of internal components within the housing body, enabling the housing body to be made with very thin walls in order to reduce its weight. The housing body has integrally formed internal walls to guide the flow of air.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    This invention relates to a heater/evaporator unit for use with a motor vehicle passenger compartment.  
         BACKGROUND  
         [0002]    Motor vehicle passenger compartments are normally heated and/or cooled by a heater and/or evaporator unit, referred to herein for convenience simply as a “heater unit”. The heater unit normally comprises a housing body through which air is made to circulate. Internal walls and pivoting flaps are normally used to guide the air through the housing body, so that the air passes through an evaporator element and a heater element within the housing body.  
           [0003]    Because the housing body supports the evaporator and heater elements, as well as the axles for the pivoting flaps, the wall thickness of the housing must be about 2 mm in order to provide the required strength. This can make the housing unit heavy, whereas an important consideration in the design of vehicle is to keep the weight of component parts to a minimum.  
           [0004]    The housing body is conventionally made from injection moulded plastics material, and is usually made in two halves which then have to be screwed together. The halves will normally have one or more upstanding surfaces which meet to form interior walls when the halves are brought together. Due to tolerance limits, undesirably air leaks can result where the two halves meet, particularly along the line or lines between different sections of interior wall.  
         SUMMARY OF THE INVENTION  
         [0005]    According to the invention, there is provided a heater unit for a motor vehicle comprising a plastics material housing body and a structural frame surrounding and supporting the housing body, characterized in that the housing body is a unitary moulding having at least one air inlet and at least one air outlet with at least one chamber therebetween.  
           [0006]    The unitary moulding reduces the likelihood of a leak occurring at the junction where separate parts would otherwise be joined together to form the housing body.  
           [0007]    Preferably, the unitary moulding of the housing body is formed by blow moulding. Since the structural frame will provide support for the housing body, the wall thickness of the unitary can be reduced, for example by making it by blow moulding, thereby making the housing unit lighter.  
           [0008]    Preferably, the housing will comprise internal walls that are also part of the unitary moulding, for example being formed by blow moulding. These internal walls will help guide the movement of air as it passes through the housing body.  
           [0009]    The internal-facing ends of the internal walls will preferably be radiused in order to reduce the turbulence of the air as is passes through the housing body. Reducing turbulence reduces the pressure difference across the housing body and hence increases the air flow.  
           [0010]    As a further preference, the internal walls will be hollow. This will allow width of the internal walls to be increased (and thereby also increase the radius of curvature of their internal facing edges) without substantially increasing the weight of the internal walls.  
           [0011]    The internal walls will preferably be curved in one direction, such that the radius of curvature lies in a single plane. The direction of curvature can be chosen to be in the same direction as the air flow through the housing body in order to further reduce turbulence.  
           [0012]    The housing body will preferably comprise a plurality of openings. Such openings may be used to provide an inlet and outlet to the housing body, or may be used to insert internal components into the housing body, such as a heater.  
           [0013]    The frame will preferably comprise a plurality of receiving features for engaging or otherwise receiving the end portions of internal components located within the housing body and supporting the weight of the components. Such receiving features may take the form of a pair of shaped loops located on opposite sides of the frame. Alternatively, the receiving features may take the form of shaped portions or shaped covers removably attached to the frame.  
           [0014]    Some or all of the receiving features may take the form of a plurality of hollow shaft portions for pivotally securing one or more axles to the frame, so that the frame bears the load of the axle and therefore that of any components joined to the axle such as a door. Openings in the housing body will preferably be provided to pass the pivot axle through the external walls, such that the axle makes direct contact with the hollow shaft portion, whose inner surface will act as a bearing for the axle.  
           [0015]    However, where other components are received by a receiving feature in the frame, a portion of the external wall of the housing body make take the form of the receiving feature, such that when the internal component is received in the feature, the wall of the housing body is interposed between the receiving feature and the internal component. Such an arrangement will reduce the likelihood of an air leak.  
           [0016]    The housing body may be held within the frame by internal components within the housing body that are engaged with, received in or otherwise connected to the frame. However, the housing body will preferably be connected to the frame at one or more securing points. Screws or bolts may be used to secure the housing body to the frame at these points.  
           [0017]    Further objects, features and advantages of the invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    The invention will now be further described, by way of example, with reference to the accompanying drawings in which:  
         [0019]    [0019]FIG. 1 shows a perspective view of a heater unit according to a first embodiment of the invention;  
         [0020]    [0020]FIG. 2 shows a schematic side view of a housing body;  
         [0021]    FIGS.  3  to  7  show a sequence of steps in the blow-moulding of a hollow article;  
         [0022]    [0022]FIG. 8 shows a schematic cross sectional view though a heater unit according to a second embodiment of the invention; and  
         [0023]    [0023]FIG. 9 shows an exploded view of the region within the dotted circle in FIG. 8.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    The following description of the preferred embodiment is merely exemplary in nature, and is in no way intended to limit the invention or its application or uses.  
         [0025]    [0025]FIGS. 1 and 2 show a heater unit  10  with a plastics material blow moulded housing body  12  surrounded by a plastic material injection moulded structural frame  14 . Fresh air enters the heater unit  10  through an inlet opening  16 , and is guided (in part) by internal walls  18 , 20 , 21  formed integrally with the housing body  12  to one or both of two outlets  30 , 130 . The air entering the heater unit  10  is first dried by passing through an evaporator  24  shown in dashed outline, and is subsequently directed by a pivoting main door  22  either to a heater  26  shown in dashed outline, or directly to one of the outlet openings  30 , 130 , depending on the position of the main door  22 . Other outlet section doors  122 , 222  are used to select one or both of the two outlets  30 , 130 .  
         [0026]    The shape of the air chamber within the heater unit  10  is defined by the internal walls of the heater unit  12 , the locations of the inlet and outlets openings  16 , 30 , 130  and the positions of the pivoting doors  22 , 122 , 222 .  
         [0027]    As will be shown below, the frame  14  is adapted to bear the weight of the main internal components within the heater unit  10 , such as the doors  22 , 122 , 222  the heater  26  and the evaporator  24 . The external walls of the housing body  12  are about 0.6 mm in thickness, and are consequently relatively weak.  
         [0028]    The frame comprises two pairs of loops  27 , 127  one loop from each pair on each opposite side of the frame  14 , such that the evaporator  24  and the heater  26  are each supported by the frame when these are placed within the housing body between the loops  27 , 127 . The housing body has on one or both sides two apertures  124 , 126  to allow for respectively the evaporator  24  and the heater  26  to be inserted into the housing body. These apertures  124 , 126  are then covered by sealing plates  7 , 107  affixed to the frame  14 . The ends of the evaporator  24  and heater  26  passing through the loops  27 , 127  are retained by cupped projections formed by the sealing plates  7 , 107  and by similar projections integral with the housing body  12  on the far side of the housing as viewed in FIG. 1.  
         [0029]    Each door  22 , 122 , 222  has a pivot axle  19 , 119 , 219  that runs through openings in the housing body  12  and is received at each end within a hollow cylindrical bearing  17 , 117 , 217  within the frame  14 , such that each pivot axle  19 , 119 , 219  is able to rotate between the bearings  17 , 117 , 217  in order allow the door to pivot. In this way, the weight of each door  22 , 122 , 222  is born by the frame  14  rather than the housing  12 , which as mentioned above, is relatively weak.  
         [0030]    Each axle  19 , 119 , 219  is prevented from moving laterally with respect to the frame  14  by a bolt  15 , 115 , 215  at one end and at the other end by a lever  13  (only one of which is shown) that has a hollow shaft  113  attached to the axle  19 . The bolts  15 , 115 , 215  and the levers  13  are situated on the outside of the frame  14 . Since the axles  19 , 119 , 219  run through openings in the housing, this method of securing the axles to the frame also serves to secure the housing body  12  to the frame  14 .  
         [0031]    The internal walls  18 , 20 , 21  each have two surfaces, denoted with the suffix a or b respectively. The surfaces do not touch each other and in this example the walls are hollow, the gap within each wall being denoted by the suffix c.  
         [0032]    The frame  14  and the housing body  12  are formed separately, the frame being formed by injection moulding, in two parts which are subsequently assembled around the housing  12  and held together at a plurality of fixing points  32 .  
         [0033]    The housing is formed by a blow moulding process that is adapted for the formation of internal walls. An example of this process will now be described with reference to FIGS.  3  to  7 , where the formation of an article shaped in only two directions is shown.  
         [0034]    [0034]FIG. 3 shows a parison  40  which has been pre-blown to a generally cylindrical form and which is arranged between two mould parts  42  and  44  which are in an open, spaced apart, position. At either side of the mould there are retractable cores  46  and  48  in the form of flat plates with rounded leading edges  49 .  
         [0035]    In the second step shown in FIG. 4, the parison  40  is fully blown into contact with the internal surfaces of the mould parts  42  and  44 . The spacing between the mould parts at this time and the thickness of the parison walls will be chosen so that this position can be reached without the unsupported parts of the parison walls over inflating. It will be seen that in this position the parison walls make light, but not complete, contact with the mould parts and that there are void areas (indicated at  50 ) where the parison has not yet fully taken up the form of the mould parts.  
         [0036]    Between the mould parts  42 , 44  the parison walls are also supported by contact against the leading edges  49  of the retractable cores  46 ,  48 .  
         [0037]    In the next stage shown in FIG. 5 the mould parts  42 ,  44  have begun to close and the retractable cores  46 ,  48  have begun to approach one another. These movements are synchronized with one another, and as this movement takes place internal pressure within the parison is maintained. As the internal volume within the parison is decreasing, the pressure exerted on the parison walls will increase and the parison walls will now take up the form of the internal surfaces of the mould parts  42 ,  44 .  
         [0038]    [0038]FIG. 6 shows the stage in which the moulding is nearly completed. The mould parts  42 ,  44  have approached one another still further and the retractable cores  46 ,  48  have also approached one another still further. It will be seen that the cores  46 ,  48  are in the form of plates that flare out with radiused shoulders  56 , 57  towards bases  52 ,  54 . When the mould is fully shut, as can be seen in FIG. 7, the mould parts  42 ,  44  seat against the bases  52 ,  54  and the radiused shoulders  56 , 57  between the plates and the bases  52 , 54  form the junction between the cores  46 , 48  and the internal mould surfaces.  
         [0039]    [0039]FIG. 7 shows the last stage in moulding where the product has two chambers  58 ,  59  which are separated by what has become a single internal moulded wall  34 .  
         [0040]    In FIGS.  3  to  7 , the internal form of the mould parts is a very simple shape. To form the housing  12  of the heater unit in FIGS. 1 and 2, three or more mould parts will be used and the mould parts will have a more complicated internal shape necessary to form the shape of the housing  12 . During the moulding process, the cores  46 , 48  will be inserted and retracted in a direction that is normal to the page in FIG. 2. Because the internal walls  18 , 20 , 21  are curved, the cores will also be curved, the curvature being in a direction normal to the direction in which the cores move during the moulding process.  
         [0041]    Each internal wall  18 , 20 , 21  is formed by two cores that move towards one another from opposite sides of the housing  12  as it is being formed. The rounded leading edges of the cores will not be straight, and when the cores meet, a narrow gap will remain between the leading edges over most of their length. This results in a web  18   d , 20   d , 21   d  of plastics material remaining between the leading edges of the cores during the formation of each respective internal wall  18 , 20 , 21 . The webs extend perpendicularly between the two sides  18   a , 18   b ;  20   a , 20   b ;  21   a , 21   b  of each respective internal wall. Close to the outside ends of the internal walls, the leading edges of the cores come into direct contact when they meet, thereby clipping off the ends of the webs  18   d , 20   d , 21   d.    
         [0042]    The webs  18   d , 20   d , 21   d  provide some structural linkage between portions of the housing separated by an internal wall. A hole can be provided in one or more of the webs in order to provide one or more securing points for one or more arms  33  of the frame  14  extending into the hollow area of the internal walls.  
         [0043]    During fabrication, the housing body  12  will be moulded with a closed exterior surface having protrusions known as lost heads extending across areas for evaporator and heater openings  124 , 126 , the inlet opening  16 , the outlet openings  30 , 130  are to be made in the housing  12  body. The openings will then be formed by cutting away these protrusions, either when the housing  12  is within the moulds  42 , 44  or after the housing  12  has been removed from the moulds. Thus, a unitary housing body  12  for a motor vehicle heater can be formed.  
         [0044]    In FIG. 8, a heater unit  10  is shown schematically in cross section. An expanded view of the region within the dotted circle is shown in FIG. 9. The cross section of the heater unit in FIG. 8 displays different aspects of the heater unit of FIGS. 1 and 2 in a single cross section, and does not represent a planar cross section through FIGS. 1 and 2.  
         [0045]    As can be seen from FIG. 8, the frame  14  had a shaped feature  65  to receive one end  24   a  of an elongate evaporator  24 , and the other end of the evaporator  24   b  is held in place by a cover  7 , shaped so that its internal face accepts the end  24   b  of the evaporator. A sheet of foam  51  is located between the ends  24   a,b  of the evaporator and the frame/cover in order to prevent significant vibration of the evaporator  24  when it is in place in the heater unit  10 . An opening  124  is provided in the housing body  12  to insert the evaporator during fabrication.  
         [0046]    Only one opening  124  in the housing body  12  is provided to insert the evaporator  24 . On the opposite side of the housing body  12 , the housing body  12  has a shaped portion  9  which conforms to the shape of one end  24   a  of the evaporator  24 . The shaped portion  9  of the housing body  12  is received in the receiving feature  65  of the frame  14 , so that when the end  24   a  of the evaporator  24  is received by the receiving feature  65 , the shaped portion  9  of the housing wall is interposed between receiving feature  65  and the evaporator end  24   a . This removes the(need for an additional opening in the wall of the housing body  12 .  
         [0047]    As described above, an internal wall  20  is shown, with surfaces  20   a  and  20   b , separated by a gap  20   c . A web  20   d  extends between the two wall surfaces  20   a  and  20   b . As can be seen more clearly in FIG. 9, arms  33  of the frame  14  extend into the gap  20   c  from both sides of the web  20   d , and the ends of the arms  33  are secured together though a hole  68  in the web  20   d , by a bolt  61  such that the hole  68  in the web  20   d  provides a securing point where the housing body  12  is secured to the frame  14 .  
         [0048]    In the lower part of FIG. 8, the door axle  19  is shown extending into a bearings  17  formed integrally with the casing. The axis is secured at each end by a bolt  15  and a lever  17  respectively.  
         [0049]    As can be appreciated from the above description, the invention provides a heater unit with a strong but light weight housing.  
         [0050]    The foregoing discussion discloses and describes a preferred embodiment of the invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that changes and modifications can be made to the invention without departing from the true spirit and fair scope of the invention as defined in the following claims.