Note: Descriptions are shown in the official language in which they were submitted.
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Swash drive
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.
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.
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.
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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.
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.
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.
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,
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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.
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.
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.
The supporting plate may be configured, for example, as a sheet-metal
part which is formed by deep drawing.
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.
It is particularly advantageous if the swash body forms a bearing
channel on the swash-plate side and supporting-p(ate side in each case,
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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.
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.
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.
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.
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
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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.
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.
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.
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.
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.
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The swash plate may likewise be configured as a sheet-metal part
which is formed by deep drawing.
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.
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.
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.
It is particularly advantageous if the motor shaft is supported in a
rotatable manner only at one end, nameiy, via the supporting bearing,
on the supporting plate. Such a configuration dispenses with a second
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bearing for the motor shaft; rather, the latter is supported only at one
end and carries the rotor of the electric motor.
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.
A more detailed explanation will be given by the following description of
two preferred embodiments of the invention, in conjunction with the
drawing, in which:
figure 1 shows a schematic sectional view of a first embodiment of
a swash drive;
figure 2 shows a schematic sectional view of a swash unit of the
swash drive fro figure 1;
figure 3 shows a schematic sectional view of a second embodiment
of a swash drive; and
figure 4 shows a schematic sectional view of an alternative swash
unit for the swash drives from figures 1 and 3.
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Figure 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 figures 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.
As is clear from figure 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.
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
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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.
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 1800, 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.
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.
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.
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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 figure 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.
Figure 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 figure 3 by the
same reference numerals as in figures 1 and 2. In respect of these
components, in order to avoid repetition, reference is made to the
explanations above.
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 particulariy straightforward construction.
Figure 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 figure 1 and for the swash drive 70 which is
illustrated in figure 3. The swash unit 80 is constructed similarly to the
swash unit 17 which is illustrated in figures 1, 2 and 3, identical
components thus being designated by the same reference numerals as
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in figures 1, 2 and 3. In respect of these components, in order to avoid
repetition, reference is made to the explanations above.
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.
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.
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.
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
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channel 93 of the swash body 81. The bearing balls 94 are supported
by the collar 86 on the outside.
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.
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.
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.
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 14 in relation to the axis of rotation
33.
