Patent Abstract:
The invention relates to a swash drive for a high-pressure cleaning appliance, having a swash body which can be driven in rotation about an axis of rotation, and having a swash plate which is inclined in relation to the axis of rotation and on the face of which there can engage pistons of a piston-pump which are movable back and forth parallel to the axis of rotation, the swash body butting against a supporting plate via a supporting bearing and a swash-plate bearing being disposed between the swash body and the swash plate. In order to develop the swash drive such that it is possible to increase the inclination of the swash plate without any risk of damaging the supporting bearing, it is proposed according to the invention that the supporting bearing be configured as an angular-contact ball bearing, the swash body supporting the bearing balls of the supporting bearing on the outside.

Full Description:
[0001]     This application is a continuation of international application number PCT/EP2005/010998 filed on Oct. 13, 2005.  
         [0002]     The present disclosure relates to the subject matter disclosed in international application number PCT/EP2005/010998 of Oct. 13, 2005 and German application number 10 2004 056 019.6 of Nov. 16, 2004, which are incorporated herein by reference in their entirety and for all purposes.  
       BACKGROUND OF THE INVENTION  
       [0003]     The invention relates to a swash drive for a high-pressure cleaning appliance, having a swash body which can be driven in rotation about an axis of rotation, and having a swash plate which is inclined in relation to the axis of rotation and on the face of which there can engage the pistons of a piston-pump which are movable back and forth parallel to the axis of rotation, the swash body butting against a supporting plate via a supporting bearing and a swash-plate bearing being disposed between the swash body and the swash plate.  
         [0004]     Such swash drives are known from WO 00/08335. They are used in high-pressure cleaning appliances in order to convert the rotary movement of a motor shaft into a back and forth movement of the pistons. By means of the pistons, it is then possible, on a periodic basis, for cleaning liquid, preferably water, to be taken in, subjected to pressure and discharged via a pressure line. If the delivery capacity of the high-pressure cleaning appliance is to be changed, then the stroke of the pistons can be changed for this purpose. A change in stroke can be achieved by the pistons butting against the face of the swash plate at a different radial spacing relative to the axis of rotation. The greater the radial spacing between the pistons and the axis of rotation of the swash body, the greater is the stroke which can be achieved by the pistons, the inclination of the swash plate remaining the same. An increase in the radial spacing between the pistons and the axis of rotation, however, requires considerable constructional reconfiguration of the piston pump.  
         [0005]     As an alternative, for the purpose of changing the delivery capacity of the high-pressure cleaning appliance, the stroke of the pistons may be changed by altering the inclination of the swash plate, the radial arrangement in relation to the axis of rotation remaining the same. The greater the inclination of the swash plate in relation to the axis of rotation of the swash body, the greater is the piston stroke which can be achieved while the radial arrangement of the pistons remains the same. In the case of the inclination of the swash plate being changed, all that is required is for the construction of the piston pump to be adapted to the changed axial movements of the pistons. Such an adaptation can be carried out in a structurally straightforward manner. An increased inclination of the swash plate, requires however considerably greater tilting moments to be transmitted from the swash plate, via the swash bearing, to the swash body and from the latter, via the supporting bearing, to the supporting plate. The resulting radial forces can only be absorbed to a very limited extent by the conventional supporting bearings since there is a risk of the rolling-contact bodies of the supporting bearing yielding in the radial direction.  
         [0006]     In order to support a swash plate on a swash body which is mounted in a rotationally fixed manner on a drive shaft, GB 976,608 A proposes a ball bearing with an inner raceway and an outer raceway. The inner raceway is connected in a rotationally fixed manner to the swash plate and the outer raceway is connected in a rotationally fixed manner to the swash body. The inner raceway is configured as a single part and has two bearing-running surfaces, whereas the outer raceway is configured in two parts and comprises a front raceway half and a rear raceway half, each of which has a bearing-running surface for the bearing balls of the ball bearing. The two raceway halves are enclosed by a bearing-carrying ring and support the bearing balls on the outside by way of their bearing-running surfaces.  
         [0007]     Japanese specification JP 2002 147343 A discloses a swash plate which is supported on a housing wall via a rolling-contact bearing. The rolling-contact bearing has a front raceway and a rear raceway, as seen in the axial direction, each with a conical bearing-running surface for rolling-contact bodies disposed therebetween.  
         [0008]     It is an object of the present invention to develop a swash drive of the type mentioned in the introduction in such a way that the inclination of the swash plate may be increased without any risk of damaging the supporting bearing.  
       SUMMARY OF THE INVENTION  
       [0009]     This object is achieved according to the invention, in the case of a swash drive of the generic type, by the supporting bearing being configured as an angular-contact ball bearing, the swash body supporting the bearing balls of the supporting bearing on the outside.  
         [0010]     According to the invention, the supporting bearing is configured as an angular-contact ball bearing and the bearing balls of the supporting bearing are supported by the swash body on the outside, as seen in the radial direction. It has been found that such a construction of the swash drive also allows relatively large radial forces to be reliably absorbed without the supporting bearing, or any other components of the swash drive, being damaged, so that the inclination of the swash plate may be increased. For example, the angle of inclination of the swash plate may be more than 14° in relation to the axis of rotation of the swash body.  
         [0011]     The supporting plate preferably has a central opening which is bounded by a radially oriented inner flange which merges, via a cranked portion, into a radially oriented outer flange, the cranked portion forming, on the swash-body side, a bearing channel for the supporting bearing. This enables particularly cost-effective production of the swash drive since the supporting plate itself forms a bearing channel for the supporting bearing, so that it is possible to dispense with a separate manufacturing step for producing the bearing channel.  
         [0012]     It is advantageous if, in relation to the axis of rotation of the swash body, the inner flange is offset with respect to the outer flange in the direction of the swash body. This enables particularly straightforward assembly of the supporting bearing since the cranked portion between the projecting inner flange and the set-back outer flange forms a centering aid for the supporting bearing, so that the ball-bearing raceway of the supporting bearing may be positioned on the supporting plate without any assembly aid.  
         [0013]     The supporting plate may be configured, for example, as a sheet-metal part which is formed by deep drawing.  
         [0014]     In an advantageous embodiment, the swash body forms, on the supporting-plate side, a bearing channel for the supporting bearing and is followed by a collar which is oriented in the direction of the supporting plate and overlaps the bearing balls of the supporting bearing. The swash body engages over the bearing balls of the supporting bearing by means of its collar, so that these bearing balls cannot yield in the radial direction. Accordingly, high radial forces can be reliably absorbed by the supporting bearing and the swash body.  
         [0015]     It is particularly advantageous if the swash body forms a bearing channel on the swash-plate side and supporting-plate side in each case, the radial spacing between the base of the swash-plate-side bearing channel and the base of the supporting-plate-side bearing channel being smaller than the diameter of the bearing balls of the supporting bearing. The supporting surfaces which the swash body forms for the bearing balls of the swash-plate bearing and of the supporting bearing may have the same pitch-circle diameters. However, it may also be provided that the pitch-circle diameter of the supporting surface for the swash-plate bearing is smaller than the pitch-circle diameter of the supporting surface which the swash body forms for the supporting bearing. The difference in pitch-circle diameters is preferably selected such that the radial spacing between the bases of the bearing channels is smaller than the diameter of the bearing balls of the supporting bearing. This also makes it possible for the swash drive to be subjected to high mechanical loading in respect of radially oriented forces also.  
         [0016]     Moreover, such a configuration enables cost-effective production of the swash body since the latter may preferably be configured as a sheet-metal part produced by deep drawing, the arrangement of the bases of the bearing channels which has been explained enabling good flow behavior of the material of the swash body.  
         [0017]     It is advantageous if the bearing balls of the swash-plate bearing differ in diameter from the bearing balls of the supporting bearing. In particular, it may be provided that the diameter of the bearing balls of the swash-plate bearing is smaller than the diameter of the bearing balls of the supporting bearing.  
         [0018]     While the supporting bearing is configured as an angular-contact ball bearing, the swash-plate bearing may be in the form of an axial ball bearing.  
         [0019]     In a particularly preferred embodiment, however, it is provided that both the supporting bearing and the swash-plate bearing are in the form of angular-contact ball bearings. It is thus additionally easier to assemble the swash drive since the swash body forms a centering aid on which the ball-bearing raceway of the swash-plate bearing can be positioned without any assembly aid. Using two angular-contact ball bearings for the swash drive makes it possible, in combination with the bearing balls of the supporting bearing being supported on the outside by the swash body, for particularly large radial forces to be reliably absorbed, so that it is also possible to provide larger angles of inclination for the swash plate without the service life of the swash drive being adversely affected.  
         [0020]     It is preferable for the swash body, in respect of its radial extent, to be configured, in an outer region, as a collar which is directed toward the supporting plate and, in a central region, as a protrusion which is directed toward the swash plate, the swash body forming in the transition region between the collar and the protrusion, on the supporting-plate side, a bearing channel of the supporting bearing and, on the swash-plate side, a bearing channel of the swash-plate bearing.  
         [0021]     It has been found that this enables particularly cost-effective shaping of the swash body by means of deep drawing, the swash body being capable of being subjected to high mechanical loading and very good flow behavior of the material of the swash body being ensured during deep drawing.  
         [0022]     The swash body may be reinforced mechanically by being configured, in its central inner region, as a well-like depression with a base wall which is oriented parallel to the supporting plate and has a central opening. In such a configuration of the swash body, the base wall is surrounded, on the swash-plate side, by an annular protrusion which, on its outer periphery, forms a bearing channel of the swash-plate bearing and merges, via a bent-around portion, into the collar of the swash body, the bent-around portion forming, on the supporting-plate side, a bearing channel of the supporting bearing.  
         [0023]     The swash plate is preferably formed as a planar annular plate which merges, via a bent-around portion, into a collar which is directed toward the swash body, the bent-around portion forming, on the swash-body side, a bearing channel of the swash-plate bearing.  
         [0024]     The swash plate may likewise be configured as a sheet-metal part which is formed by deep drawing.  
         [0025]     In a particularly preferred embodiment of the swash drive according to the invention, mounted on the supporting plate is an electric motor, the motor shaft of which is mounted in a rotationally fixed manner on the swash body and is supported in a rotatable manner via the supporting bearing. The supporting bearing, in the form of an angular-contact ball bearing, in such an embodiment, does not just perform the function of supporting the swash body on the supporting plate; rather, in addition, the motor shaft of the electric motor is supported in a rotatable manner via the supporting bearing. This enables a particularly straightforward construction of the swash drive, which can be produced cost-effectively and can be assembled within a short period of time, because it is possible to dispense with a separate bearing for the motor shaft in the region of the supporting plate.  
         [0026]     It is particularly advantageous if the electric motor is configured as an external rotor motor with a stator, which is mounted on the supporting plate, and a rotor, which is fitted around the stator and is connected in a rotationally fixed manner to the motor shaft. Using an external rotor motor enables the construction of the swash drive to be simplified further, the stator being mounted on the supporting plate—for example by means of connecting screws. The supporting plate thus forms an end flange of the electric motor, and the motor shaft is supported via the swash body and the supporting bearing.  
         [0027]     It may be provided that the motor shaft is supported in a rotatable manner at two locations, namely, on the stator, via a motor bearing, and, via the supporting bearing, on the supporting plate. The support on the stator can be provided by means of a plain bearing or a rolling-contact bearing, in particular a ball bearing.  
         [0028]     It is particularly advantageous if the motor shaft is supported in a rotatable manner only at one end, namely, via the supporting bearing, on the supporting plate. Such a configuration dispenses with a second bearing for the motor shaft; rather, the latter is supported only at one end and carries the rotor of the electric motor.  
         [0029]     In a preferred embodiment, the electric motor is mounted on the supporting plate by the swash drive having a cup-like housing with a base wall and a circumferential wall projecting therefrom, the base wall having an opening and being clamped in between the supporting plate and the stator of the electric motor. In the case of such a construction, the supporting plate butts against the inside of the base wall and the stator of the electric motor butts against the outside of the base wall of the housing and, by virtue of the supporting plate being screw-connected to the stator, the base wall is clamped in between these two components, so that the latter are mounted on the housing of the swash drive in a releasably connectable manner. It is advantageous here if the supporting plate forms a positive fit with the housing by way of its outer periphery, because this allows the mechanical loading to which the swash drive can be subjected to be increased and simplifies assembly.  
         [0030]     A more detailed explanation will be given by the following description of two preferred embodiments of the invention, in conjunction with the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]      FIG. 1  shows a schematic sectional view of a first embodiment of a swash drive;  
         [0032]      FIG. 2  shows a schematic sectional view of a swash unit of the swash drive fro  FIG. 1 ;  
         [0033]      FIG. 3  shows a schematic sectional view of a second embodiment of a swash drive; and  
         [0034]      FIG. 4  shows a schematic sectional view of an alternative swash unit for the swash drives from  FIGS. 1 and 3 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]      FIG. 1  illustrates, schematically, a swash drive  10  for a high-pressure cleaning appliance. It comprises an electric motor  11  which is configured as an external rotor motor and has a stator  12  and a rotor  13  which is fitted around the latter and is mounted in a rotationally fixed manner on a motor shaft  14 , which is fitted through the stator  12 . The swash drive  10  also comprises a swash unit  17  which is surrounded by a cup-like housing  19  and has a swash body  21 , which is connected in a rotationally fixed manner to the motor shaft  14 , and a swash plate  23 . The swash body  21  butts, via a supporting bearing  25  configured as an angular-contact ball bearing, against a supporting plate  28 , which is screw-connected to the stator  12 . The swash plate  23  is supported on the swash body  21  via a swash-plate bearing  31  configured as an axial ball bearing. In the embodiments which are illustrated in FIGS.  1  to  3 , the swash plate is in the form of a planar, annular plate and is inclined in relation to the axis of rotation  33  of the motor shaft  14 . Pistons  36  of an axial piston pump, which is known per se and has thus not been illustrated in the drawing, butt against a face  35  of the swash plate  23 . The pistons  36  are mounted such that they can be displaced axially, that is to say parallel to the axis of rotation  33 , in a cylinder head  37  and are biased in the direction of the swash plate  23  by means of springs which surround the pistons  36  and are known per se, and, for reasons of clarity, have thus not been illustrated in the drawing either.  
         [0036]     As is clear from  FIG. 2  in particular, the supporting plate  28  has a central opening  39  which has the motor shaft  14  fitted through it and is bounded by a radially oriented inner flange  40  which, via a cranked portion  41 , merges into a radially oriented outer flange  42 . In relation to the axis of rotation  33 , the inner flange  40  is offset with respect to the outer flange  42  in the direction of the swash body  21 , and the cranked portion  41  forms, on the swash-body side, that is to say directed toward the swash body  21 , a first bearing channel  44  for the supporting bearing  25 , so that bearing balls  45  of the supporting bearing  25  can roll on the bearing channels  44 .  
         [0037]     On the rear side of the supporting plate  28 , this rear side being directed away from the first bearing channel  44 , the stator  12  butts with surface contact against the supporting plate  28  in the region of the inner flange  40  and is screw-connected to the supporting plate  28  by means of connecting screws  46 .  
         [0038]     The swash body  21  has a central opening  48  which has the motor shaft  14  fitted through it and is bounded by a radially oriented inner flange  49 , which is followed by an annular raised portion  50  which, via a bent-around portion  51 , merges into a collar  52  which is directed toward the supporting plate  28 . The raised portion  50  extends in the circumferential direction only over part of the swash body  21 , its height increasing continuously in the axial direction from a 0 value, over an angle range of 180°, to a maximum value, in order then to drop back to the 0 value again over a further angle range of 180°. The raised portion  50  forms, on the swash-plate side, a bearing surface  54  which is in the form of a circular disc, is inclined obliquely in relation to the axis of rotation  33  and is oriented parallel to the swash plate  23 , and in which a first bearing channel  55  of the swash-plate bearing  31  is formed, so that bearing balls  56  of the swash-plate bearing  31  can roll on the bearing channels  55 . A corresponding second bearing channel  58  is formed in the swash plate  23  on the swash-body side.  
         [0039]     The bent-around portion  51  of the swash body  21  forms, on the supporting-plate side, a second bearing channel  60  for the supporting bearing  25 . The bearing balls  45  are supported on their outside, directed away from the axis of rotation  33 , by the collar  52  of the swash body  21 . On the inside, they are supported on the cranked portion  41 .  
         [0040]     The housing  19  of the swash drive  10  has a base wall  62  with a central opening  63 , and a sleeve-like circumferential wall  64  projects from the base wall  62 . The base wall  62  is clamped in between the outer flange  42  of the supporting plate  28  and the stator  12  of the electric motor  11 . In the transition region between the base wall  62  and the circumferential wall  64 , the housing  19  forms a reception  65  for receiving the supporting plate  28  in a positive manner.  
         [0041]     As has already been explained, the electric motor  11  is configured as an external rotor motor, the rotor  13  being fitted around the stator  12  and being connected in a rotationally fixed manner to the motor shaft  14 . In the exemplary embodiment which is illustrated in  FIG. 1 , this motor shaft is supported in a rotatable manner on the one hand on the supporting plate  28 , via the swash body  21  and the supporting bearing  25  in the form of an angular-contact ball bearing, and on the other hand on the stator  12 , via a ball bearing  67 . In addition to performing the function of supporting the swash body  21  in a rotatable manner, the supporting bearing  25  thus also performs the function of supporting the motor shaft  14  in a rotatable manner.  
         [0042]      FIG. 3  illustrates a second embodiment of a swash drive according to the invention and is designated  70  overall. This embodiment is largely identical to the swash drive  10  which has been described above. Identical components have thus been designated in  FIG. 3  by the same reference numerals as in  FIGS. 1 and 2 . In respect of these components, in order to avoid repetition, reference is made to the explanations above.  
         [0043]     The swash drive  70  differs from the swash drive  10  in that use is made of an electric motor  71  with a motor shaft  72  which is supported only at one end. The bearing mounting at one end of the motor shaft  72  is effected by means of the supporting bearing  25 , as has already been described above. The rotor  73  of the electric motor  71  is secured in a rotationally fixed manner on the motor shaft  72  and is fitted around the stator  74  of the electric motor  71 . The swash drive  70  is thus distinguished by a particularly straightforward construction.  
         [0044]      FIG. 4  illustrates an alternative embodiment of a swash unit which is designated  80  overall and can be used both for the swash drive  10  which is illustrated in  FIG. 1  and for the swash drive  70  which is illustrated in  FIG. 3 . The swash unit  80  is constructed similarly to the swash unit  17  which is illustrated in  FIGS. 1, 2  and  3 , identical components thus being designated by the same reference numerals as in  FIGS. 1, 2  and  3 .. In respect of these components, in order to avoid repetition, reference is made to the explanations above.  
         [0045]     The swash unit  80  differs from the swash unit  17  in that both the supporting bearing and the swash-plate bearing are configured as angular-contact ball bearings. The swash unit  80  comprises a supporting plate  28  like that which has already been explained above. In addition, it has a swash body  81  and a swash plate  82 . The swash body  81  is supported on the supporting plate  28  via a supporting bearing  83  configured as an angular-contact ball bearing, and a swash-plate bearing  84  likewise configured as an angular-contact ball bearing is disposed between the swash plate  82  and the swash body  81 .  
         [0046]     The swash body  81  forms, on its outer circumference, a collar  86  which is directed toward the supporting plate  28  and, in a radially central region, the swash body  81  is in the form of an annular protrusion  87  which is directed toward the swash plate  82 . In the circumferential direction, this protrusion does not have a uniform axial height; rather, the height of the protrusion  87  increases continuously from a minimum height, over an angle range of 180°, to a maximum height, in order to drop back to the minimum height again over a further angle range of 180°. The protrusion  87  has a planar end surface  88  which is inclined in relation to the axis of rotation  33  in a manner corresponding to the swash plate  82 . The protrusion  87  encloses a central well-like depression with a base wall  89  which has a central opening  90  and is oriented parallel to the supporting plate  28 .  
         [0047]     On the outside, the end surface  88  is followed, in a transition region between the protrusion  87  and the collar  86 , by a bearing channel  91  for bearing balls  92  of the swash-plate bearing  84 . The bearing balls  92  are thus supported by the protrusion  87  on the inside.  
         [0048]     Offset radially outward with respect to the bearing channel  91 , the bearing body  81  forms, on the supporting-plate side, a bearing channel  93  for bearing balls  94  of the supporting bearing  83 . The bearing channel  44  of the supporting plate  28  corresponds with the bearing channel  93  of the swash body  81 . The bearing balls  94  are supported by the collar  86  on the outside.  
         [0049]     The swash plate  82  is configured as a planar annular plate which is oriented obliquely in relation to the axis of rotation  33  and merges, via a bent-around portion  96 , into a collar  97  which is directed toward the swash body  81 , and the bent-around portion  96  forms, on the swash-body side, a bearing channel  98  which corresponds with the bearing channel  91  of the swash body  81 .  
         [0050]     Both for the swash unit  17  and for the swash unit  80 , the supporting plate  28  forms an alignment aid for assembling the swash drive, since the supporting bearings  25  and  83 , respectively, can be positioned on the cranked portion  41  of the supporting plate  28  without any further assembly aid.  
         [0051]     For the swash unit  80 , the swash body  81  forms a further alignment aid for assembly purposes, since the swash-plate bearing  84  can be positioned on the protrusion  87  without any further assembly aid.  
         [0052]     The spacing between the base of the bearing channels  55  and  91  of the swash-plate bearings  31  and  84 , respectively, and the base of the bearing channel  60  or  93  of the supporting bearing  25  or  83 , respectively, is less than the diameter of the bearing balls  45  and  94  of the supporting bearings  25  and  83 , respectively. This allows the swash units  17  and  80  to be subjected to particularly high loading. This makes it possible, in particular, to orient the swash plates  23  and  82  at an angle of inclination of more than  140  in relation to the axis of rotation  33 .

Technology Classification (CPC): 5