Electrically actuated wheel hub clutch apparatus

An electrically actuated wheel hub clutch includes a clutch device. The clutch device alternately engages and disengages a wheel hub relative to an axle shaft. An electric motor actuates the clutch device. An electric circuit delivers electric current to the motor. The circuit includes a brush and a radially aligned slip ring arranged for relative rotation about an axis. The brush and slip ring are carried by respective holders. The brush holder includes at least one radial projection overlapping both the brush and slip ring to prevent relative axial disengagement therebetween.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an electrically actuated wheel hub clutch 
apparatus and more particularly to an electrically actuated wheel hub 
clutch apparatus for automobiles and other types of machines. 
2. Description of the Related Art 
A conventional electric wheel hub clutch apparatus is disclosed in Japanese 
Utility Model Laid Open Publication No. 63(1988)-52626 published without 
examination on Apr. 8, 1988. The clutch is adapted to convert from 
two-wheel drive to fourwheel drive by turning a switch. That clutch is 
shown in FIG. 5, herein where a wheel hub 19' is rotatably assembled on an 
outer peripheral surface of a stationary axle tube 14' by means of 
bearings 30', 31'. A cylindrical body 1' is fixed to a cover 2' by a bolt 
3'. A ring 4' is fixed to an inside portion of the cylindrical body 1' by 
a plate 9' and a snap ring 5'. An inner sleeve 6' which is rotated 
together with an axial shaft 8' is engaged with the snap ring 5a' and is 
rotatably supported by the ring 4'. A cam surface 12b' is formed on the 
outer peripheral surface of a boss 12a' of a handle 12'. 
A clutch member 7' is in contact with a cam follower 10' assembled in the 
boss 12a'. The outer peripheral surface of the clutch member 7' and the 
inner peripheral surface of the cylindrical body 1' are axially and 
slidably attached by a spline-connection. A tension spring 13' is 
provided, between the clutch member 7' and the cam follower 10' and a 
tension spring 11' is provided between the handle 12' and the cam follower 
10'. Furthermore, a motor 16' fixed in a lateral wall of the cylindrical 
body 1' has a shaft 16a' and a pinion gear 15' fixedly connected to a free 
end portion of the shaft member 16a'. Gear teeth 12c' are provided on the 
outer peripheral surface of the handle 12' so as to engage with the pinion 
gear 15'. 
A lock plate 32' is in spline-connection with the axle tube 14' and a lock 
nut 33' is connected to the lock plate 32' by means of a bolt 34'. A pair 
of slip rings 35' are assembled on the outer periphery of the lock nut 
32'. An electric cord 36' is inserted in a throughhole 14a' formed in the 
axle tube 14'. One end of the electric cord 36' is connected to a terminal 
of the slip ring 35', and other end of the electric cord 36' is connected 
to a control box (not shown), an electric source (not shown), and a switch 
of a driver's seat in the automotive vehicle. A brush case 37' is fixed to 
the wheel hub 19', and a pair of springs 38' are accommodated in the brush 
case 37'. A pair of brushes 39' are connected to ends of the springs 38' 
and are biased against the slip rings 35'. A convex terminal 16b' of the 
motor 16' is fixedly connected to a concave terminal 40' attached to other 
end of the springs 38'. 
In operation, assume that the clutch member 7' is disengaged from the inner 
sleeve 6' as shown in FIG. 5. After the switch (not shown) is turned on, 
electric current flows to the motor 16' through the slip rings 35', and 
the shaft 16a' is rotated in one direction. The handle 12' engaged with 
the pinion gear 15' is rotated into the one direction, and a pawl 10a' of 
the cam follower 10' is leftwardly cammed by a cam surface 12b' of the 
handle 12'. Accordingly, the clutch member 7' is leftwardly moved and is 
engaged with the inner sleeve 6' via splines 6a', 7a'. The axle shaft 8' 
is thereby connected to the wheel hub 19' to perform the four-wheel drive 
function. 
In the above-mentioned conventional free wheel hub apparatus, the lock 
plate 32' having the slip rings 35' is in spline-connection with the axle 
tube 14'. The brush case 37' having the brushes 39' contacted with the 
slip rings 35' is assembled in the wheel hub 19'. Thus, the lock plate 32' 
and the brush case 37' are separately provided so that the brushes 39' are 
influenced by the vibration of the condition of road surface through the 
wheel hub 19' and a wheel of the vehicle. Accordingly, there is the 
possibility that the brushes 39' may become shifted away from the 
contacting surface of the slip rings 35'. Furthermore, it is difficult to 
adjust the brushes 39' to the slip rings 35' upon assembling the brush 
case 37' and the slip rings 35', so that there is the possibility that the 
brushes 39' and the slip rings 35' become abnormally worn. As a result, 
there is a fear that the ability to transmit electric current is impaired 
due to the bad condition of the environment such as vibration and the 
presence of foreign materials, etc. 
OBJECTS AND SUMMARY OF THE PRESENT INVENTION 
It is an object of the present invention to provide an electrically 
actuated wheel hub clutch apparatus wherein it is easy to adjust the brush 
and the slip ring upon assembling the brush case and the slip ring. 
It is another object of the present invention to provide an electrically 
actuated wheel hub clutch apparatus which minimizes the occurrence of wear 
between the brush case and the slip ring. 
It is still another object of the present invention to provide an 
electrically actuated wheel hub clutch apparatus wherein the ability to 
transmit electric current is maintained even under bad conditions of the 
environment such as vibration and the presence of foreign materials, etc. 
In order to accomplish the objects, the present invention provides a radial 
retainer which forms a part of either a brush holder or a slip ring holder 
and which radially overlaps the brush and its associated slip ring in 
order to resist axial dislodgement therebetween.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the present invention will hereinafter be described with 
reference to FIGS. 1 to 4 inclusive. In an electrically actuated wheel hub 
clutch apparatus according to the present invention, a cylindrical body 1 
is fixed by a bolt 3 to an external end of a wheel hub 19 which is 
rotatably installed on an external end of an axle tube 14. 
In the cylindrical body 1, a ring 4 is supportingly interposed between a 
plate 9 and a pair of snap rings 5, one of which snap rings is held by the 
cylindrical body 1 and the other of which is supported in the ring 4. The 
plate 9 is rotatably supported on the outer periphery of an inner sleeve 6 
adjacent the ends of a plurality of splines 6a on the sleeve 6. The inner 
sleeve 6 rotates together with an axle shaft 8 and is rotatably supported 
by the ring 4. A handle 12 is rotatably supported by a bush 17 fitted to a 
boss 2a of a cover 2 attached to the cylindrical body 1 by the bolt 3. A 
cam surface 12b is formed on a circumference of a boss 12a of the handle 
12. A cam follower 10 bears against the outer periphery of the boss 12a of 
the handle 12, with a pawl 10a of the cam follower 10 impinging upon the 
cam surface 12. 
A clutch member 7 is so provided as to impinge upon the cam follower 10. 
The clutch member 7 is installed so that it is axially slidable between 
its outer peripheral surface and the inner peripheral surface of the 
cylindrical body 1 while being prevented from rotating relative to the 
body 1 by splines 1a on the body inner surface. A tension spring 11 is 
attached to the cam follower 10 and the handle 12, and a tension spring 13 
is attached to the follower 10 and the clutch member 7. Splines 7a, 6a, 
which are capable of engaging with each other, are provided on the inner 
peripheral surface of the clutch member 7 and on the outer peripheral 
surface of the inner sleeve 6, respectively. 
A motor 16 including a shaft 16a is installed in the side wall of the body 
1. The free end of the shaft 16a is provided with a pinion gear 15. Gear 
teeth 12c are provided on the outer periphery of the handle 12 so as to 
mesh with the pinion gear 15. A lock plate 44 and a lock nut 42 are seated 
against the end surface of the bearing 31 with a view to preventing the 
bearings 31 from being removed therefrom. The lock nut 42 is screwed to 
the axle tube 14; the lock plate 44 is spline-joined to the axle tube 14; 
and they are mutually joined by a bolt 43. A pair of slip rings 41 are 
fixed to the outer periphery of the lock plate 44 through an insulating 
member 45, whereby the lock plate forms a slip ring holder. The axle tube 
14 is formed with a throughhole 14a in which an electric cord 36 is 
disposed. 
One end of the electric cord 36 is connected to terminals of the slip rings 
41 of the lock plate 44, and the other end thereof passes to a control box 
(not shown) within the car and is then branched off to an electric power 
source(not shown) and to a switch (not shown) in the proximity of the 
driver's seat. 
A brush holder in the form of a case 47, including an integral wall 47a and 
plate 51, is axially supported by an arrangement comprising a spacer 49, a 
connecter 53 and a snap ring 50. The spacer 49 and the snap ring 50 are 
adjacently disposed and mounted to the lock plate 44. The brush case 47 is 
rotatable relative to the lock plate 44. The connector 53 is received in a 
lug 51a of plate 51. A radial inward projection portion 52 provided on the 
brush case 47 (FIG. 4) extends axially between a pair of brushes 46 
disposed in the brush case 47 and between the slip rings 41, so that the 
brushes 46 may be supported with respect to the slip rings 41 only for 
rotational movement about the axle shaft 8 while in continuous contact 
with the slip rings 41. Thus, the projection 52 radially overlaps the 
brushes and slip rings to prevent axial disengagement therebetween. This 
function is also performed by the portions 47a, 51 of the brush case 47. 
Thus, the projection 52 and portions 47a, 51 constitute axial retainers 
for the brushes and slip rings. Alternatively, radial outward projections 
(not shown) could be provided on the insulating member 45 and extended 
radially outwardly for retaining the slip rings 41 and the brushes 46. 
The brushes 46 are fitted to the ends of a pair of springs 48 to be biased 
against the slip rings 41. Other ends of the springs are connected to the 
connecter 53 by a flexible printed circuit 61 deposited on the plate 51 
(FIG. 3). 
A convex terminal of the motor 16 is designed to fit in a concave terminal 
of the brush case 47 when the cylindrical body 1 is fastened to the wheel 
hub 19, whereby the circuit extending from the motor 16 to the wheel hub 
19 can be created by a one-touch operation. 
The operation of the electrically actuated a wheel hub clutch apparatus 
will be explained below. 
When a switch (not shown) is turned on at a time when the clutch member 7 
is separated from the inner sleeve 6, (depicted in the upper half of FIG. 
1), the motor 16 is charged with electricity through the brushes 46 and 
slip rings 41. As a result, the shaft 16a rotates in a first direction for 
a preselected angular distance, and concomitantly the handle 12 engaging 
the pinion gear 15 rotates in a second direction opposite to the first 
direction. Subsequently, the pawl 10a of the cam follower 10 is cammed in 
the axial direction, (i.e., it is shifted to the left as viewed in FIG. 1) 
by the cam surface 12b of the handle 12. This causes the clutch member 7 
to move in the same direction and engage splines 6a of the inner sleeve 6, 
thereby establishing a four-wheel drive function by linking the axle shaft 
8 to the wheel hub 19 as shown in the bottom half of FIG. 1. This movement 
of the clutch member 7 causes the tension spring 11 to be stretched. 
When it is desired that the above-described clutch member 7 be disengaged 
from the inner sleeve 6, and assuming the vehicle is stopped, the switch 
(not shown) is turned off, at which time the shaft 16a rotates to its 
original position and rotates the handle 12 in the direction opposite to 
the direction of rotation of the shaft 16a. Since the pawl 10a of the cam 
follower 10 is biased by spring 11 in the axial direction (to the right as 
viewed in FIG. 1) against the cam surface 12b of the handle 12, the cam 
follower 10 will be displaced to the right as the handle 12 rotates. 
However, the clutch member 7 will resist such movement, due to frictional 
contact with the sleeve 6 and resistance of spring 13. Accordingly, the 
pawl 10a comes to a stop just when the force of the tension spring 11 is 
equalized by the counter force of friction and the tension spring 13. 
Thereafter, when the vehicle moves, cooperative rotation is made between 
the axle shaft 8 and the wheel hub 19, thereby producing cooperative 
rotation between the inner sleeve 6 and the clutch member 7. When this 
occurs, frictional force between the inner sleeve 6 and the clutch member 
7 is reduced to the point where the clutch member 7 can be pulled in the 
axial direction (to the right in FIG. 1) under the urging of the tension 
spring 11 to become separated from the inner sleeve 6. Therefore, the 
two-wheel drive function is eliminated. 
It will be appreciated that the part 47a, 51, and the part 52, which parts 
radially overlap the brushes and slip rings, constitute retainers which 
prevent relative axial movement of the brushes relative to the slip rings. 
While those retainers have been depicted as connected to the brush case 
47, they could, in the alternative, be connected to the structure holding 
the slip rings, e.g., the insulation 45. Such retainers also resist the 
influx of foreign matter such as dust between the brushes and slip rings. 
Such protection is easy to achieve during assemblage of the clutch 
apparatus. 
The above-described apparatus is only exemplary of a preferred embodiment 
of the invention. Modifications thereof are possible without departing 
from the scope of the appended claims.