Note: Descriptions are shown in the official language in which they were submitted.
CA 02532490 2006-O1-10
ALL TERRAIN VEHICLES
FIELD OF THE INVENTION
The present invention relates to an improved all terrain vehicle.
BACKGROUND OF THE INVENTION
A known type of the all terrain vehicle includes a motor-driven power steering
apparatus disposed between an input shaft connected to an operating handlebar
and an output shaft connected to a wheel side. (See, for example, Japanese
Utility Model Laid-open No. Hei 3-1877.
Figs. 1 and 6 of Japanese Utility Model Laid-open No. Hei 3-1877 show the
following arrangements. Specifically, an input shaft 5 is installed on a lower
portion of an operating handlebar 3. An output shaft 11 is connected to the
input
shaft 5 via a motor-driven power steering apparatus. The motor-driven power
steering apparatus includes as part of components thereof a torsion bar 19
disposed between the input shaft 5 and the output shaft 11. There is included
a
stopper mechanism 101 disposed on the side of the input shaft 5. The stopper
mechanism 101 includes a lock member 103 protruded from the input shaft 5 and
a pair of stopper members 105 protruded from a chassis 37. The stopper
mechanism 101 restricts the maximum steering angle of the operating handlebar
3.
The motor-driven power steering apparatus includes a steering torque sensor 7
that includes the torsion bar 19, a reduction gear mechanism 9, a drive motor
17,
a control unit 15 shown in Fig. 3, and the like.
WH-12841 / cs
CA 02532490 2006-O1-10
-2-
The input shaft 5 is rotated with the operating handlebar 3 to twist the
torsion
bar 19. This produces a relative rotational angle in the input shaft 5 and the
output shaft 11. A potentiometer detects this relative rotational angle and a
signal corresponding to the detected relative rotational angle is applied to
the
control unit. Based on the signal, the control unit 15 controls the drive
motor 17
so as to give the side of the output shaft 11 a driving force corresponding to
a
steering torque detected by the steering torque sensor 7.
Figs. 5 and 8 of Patent Document 1 show a stopper mechanism 33 on the side of
the output shaft 11. The stopper mechanism 33 includes a lock member 35
protruded from the output shaft 11 and a pair of stopper members 39 mounted
on the chassis 37. The stopper mechanism 33 restricts a range of rotational
angles
of the output shaft 11.
Assume that the motor-driven power steering apparatus includes only the
stopper mechanism 101 on the side of the input shaft 5 as shown in Fig. 1.
Further assume a condition, in which the operating handlebar 3 is turned until
the lock member 103 contacts the stopper member 105 of the chassis 37. Even in
this condition, wheels of a vehicle can be forcibly turned clockwise or
counterclockwise by bumps and dents in a road surface. As the wheels are
turned clockwise and counterclockwise, the output shaft 11 can be rotated
through a rotational angle greater than the rotational angle of the input
shaft 5.
This produces a relative rotational angle in the input shaft 5 and the output
shaft
11, thus operating the drive motor 17 and increasing power consumption of the
drive motor 17.
Assume, on the other hand, that the motor-driven power steering apparatus
includes only the stopper mechanism 33 on the side of the output shaft 11 as
shown in Figs. 5 and 8. Further assume a condition, in which the wheels of the
vehicle are forcibly turned clockwise or counterclockwise by bumps and dents
in
the road surface, causing the stopper member 39 of the stopper mechanism 33 to
abut on the lock member 35. Even in this condition, as the wheels are turned
clockwise and counterclockwise, the input shaft 5 can be rotated through a
WH 12841/cs
CA 02532490 2006-O1-10
-3-
rotational angle greater than the rotational angle of the output shaft 11.
This
produces a relative rotational angle in the input shaft 5 and the output shaft
11,
thus operating the drive motor 17 and again increasing the power consumption
of the drive motor 17.
It is therefore an object of the present invention to improve the all terrain
vehicle
and to reduce load on a power assist motor included in the motor-driven power
steering apparatus.
SUMMARY OF THE INVENTION
To achieve the foregoing object, the present invention is, in all terrain
vehicle
having an input shaft disposed on the side of a handlebar and an output shaft
disposed on the side of left and right wheels, the input shaft and the output
shaft
being connected together via a motor-driven power steering apparatus, and
driving a power assist motor included in the motor-driven power steering
apparatus in accordance with a relative rotational angle in the input shaft
and the
output shaft, characterized by comprising a first lock member secured to the
input shaft; a first stopper secured to a vehicle body at a position
corresponding
to the first lock member, the first stopper for restricting a swing range of
the first
lock member; a second lock member secured to the output shaft; and a second
stopper secured to the vehicle body at a position corresponding to the second
lock member, the second stopper for restricting a swing range of the second
lock
member.
The first lock member secured to the input shaft and the first stopper secured
to
the vehicle body at the position corresponding to the first lock member
restrict a
rotational angle range of the input shaft. The second lock member secured to
the
output shaft and the second stopper secured to the vehicle body at the
position
corresponding to the second lock member restrict a rotational angle range of
the
output shaft.
Restricting the rotational angle range of the input shaft prevents the input
shaft
from rotating in excess of a predetermined rotational angle range by handlebar
operation. Restricting the rotational angle range of the output shaft prevents
the
WH 12841/cs
CA 02532490 2006-O1-10
-4-
output shaft from rotating in excess of a predetermined rotational angle range
via wheels by a road surface having bumps and dents. Accordingly, the relative
rotational angle in the input shaft or the output shaft is kept within a
predetermined angle. Even when rotation of either the input shaft or the
output
shaft is restricted, therefore, an excessive torque can, for example, be
prevented
from being applied to a torque sensor portion. This reduces load being applied
to the power assist motor.
An aspect of the present invention is characterized in that the first stopper
and
the second stopper make a rotational range of the input shaft equivalent to a
rotational range of the output shaft.
The rotational range of the input shaft is made to be equal to the rotational
angle
of the output shaft by the first stopper and the second stopper. Accordingly,
when the rotational range of the input shaft is restricted by the first
stopper, the
same rotational range is also restricted for the output shaft by the second
stopper. When the input shaft and the output shaft are rotated through their
maximum rotational angles, the relative rotational angle in the input shaft
and
the output shaft becomes zero and the power assist motor is stopped.
Another aspect of the present invention is characterized in that the input
shaft
and the output shaft are connected via a torsion bar.
Rotation of the input shaft is transmitted to the output shaft via the torsion
bar.
If the rotational range of the input shaft is restricted by the first stopper
and the
rotational angle of the output shaft is restricted by the second stopper,
there is no
chance that the torsion bar will be twisted excessively.
A further aspect of the present invention is characterized in that the second
lock
member is disposed on a center arm that is mounted on the output shaft and
connected to left and right tie rods for steering the left and right wheels.
Since the second lock member is disposed on the center arm, the center arm
serves also as a supporting portion for the second lock member.
WH 12841/cs
CA 02532490 2006-O1-10
-5-
Yet another aspect of the present invention is characterized in that the first
lock
member is disposed upward of a bearing portion of the input shaft and the
second lock member is disposed downward of a bearing portion of the output
shaft.
The first lock member is disposed upward of the bearing portion of the input
shaft so as to be away from the torsion bar and the second lock member is
disposed downward of the bearing portion of the output shaft so as to be away
from the torsion bar. Even if, for example, the input shaft or the output
shaft
rotates more than the predetermined rotation range because of part-to-part
manufacturing variations involved in the position, at which the first lock
member
is locked by the first stopper or the second lock member is locked by the
second
stopper, torque transmitted from the side of the input shaft or the side of
the
output shaft to the torsion bar is made smaller by twist in a torque
transmission
path involved midway therebetween.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the drawings, wherein:
Fig. 1 is a side elevational view showing all terrain vehicle according to an
embodiment of the present invention.
Fig. 2 is a plan view showing the all terrain vehicle according to the
embodiment
of the present invention.
Fig. 3 is a side elevational view showing principal parts of a front portion
of the
all terrain vehicle according to the present invention.
Fig. 4 is a cross-sectional view showing an output shaft lower end support
portion according to the embodiment of the present invention.
Fig. 5 is a cross-sectional view taken along line 5-5 of Fig. 4.
WH 12841/cs
CA 02532490 2006-O1-10
-6-
Fig. 6 is a cross-sectional view taken along line 6-6 of Fig. 3.
Figs. 7(a) and 7(b) are side elevational views showing principal parts of an
input
shaft stopper mechanism according to other embodiments of the present
invention.
Fig. 8 is a perspective view showing a right side surface of the all terrain
vehicle
according to the present invention.
Fig. 9 is a perspective view showing principal parts indicating a manual
switch
for shutting down supply of an electric power to an electric motor of the
motor-
driven power steering apparatus according to the embodiment of the present
invention.
Fig. 10 is a perspective view showing principal parts indicating a manual
switch
for shutting down the supply of the electric power to the electric motor of
the
motor-driven power steering apparatus according to another embodiment of the
present invention.
Fig. 11 is a perspective view showing principal parts indicating a manual
switch
for shutting down the supply of the electric power to the electric motor of
the
motor-driven power steering apparatus according to still another embodiment of
the present invention.
Figs. 12(a), 12(b), and 12(C) are perspective views showing examples of the
manual switch according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The best mode for carrying out the present invention will be described below
with reference to the accompanying drawings. The drawings should be viewed
in the direction of reference numerals.
Fig. 1 is a side elevational view showing all terrain vehicle according to an
embodiment of the present invention. All terrain vehicle 10 is a four-wheel-
WH 12841/cs
CA 02532490 2006-O1-10
_7-
drive vehicle including front wheels 12, 13 (only reference numeral 12
representing the front wheel on a proximal side is shown), rear wheels 14, 15
(only reference numeral 14 representing the rear wheel on the proximal side is
shown), and a power unit 22. The front wheels 12, 13 are mounted on a front
portion of a vehicle body frame 11 via a suspension arm not shown. The rear
wheels 14, 15 are mounted on a rear portion of the vehicle body frame 11 via a
suspension arm not shown. The power unit 21 including an engine 17 and a
transmission 18 is mounted at a central portion of the vehicle body frame 11.
The
power unit 21 drives the front wheels 12, 13 and the rear wheels T4, 15. T'he
alI
terrain vehicle 10 further includes a motor-driven power steering apparatus 22
and a manual switch 166. The motor-driven power steering apparatus 22
includes a power assist portion (not shown) for lightening a steering force
required for steering the front wheels 12, 13. The manual switch 166 allows
supply of an electric power to the motor-driven power steering apparatus 22 to
be shut down.
An input shaft 24 forming part of the motor-driven power steering apparatus 22
is a member that is rotated through operation of a handlebar 25 mounted on an
upper portion of the input shaft 24.
Reference numeral 26 represents an exhaust pipe extended from a front portion
of the engine 17 rearwardly. Reference numeral 27 represents a muffler
connected to a rear end of the exhaust pipe 26. Reference numeral 31
represents
a carburetor connected to a rear portion of the engine 17 via an intake pipe
32.
Reference numeral 33 represents an air cleaner connected to the carburetor 31
via
a connecting tube 34. Reference numeral 36 represents a front carrier.
Reference
numeral 37 represents a headlamp. Reference numeral 38 represents a radiator.
Reference numeral 41 represents a front fender. Reference numeral 43
represents
a fuel tank. Reference numeral 44 represents a seat that can be opened or
closed
by a simple operation, for example, by operating a Iever exposed from a
vehicle
body (to be described in detail later). Reference numeral 46 represents a rear
carrier. Reference numeral 47 represents a rear fender. Reference numeral 48
represents a step floor.
WH 12841/cs
CA 02532490 2006-O1-10
-g-
A battery 49 disposed downward of a rear portion of the seat 44 supplies the
motor-driven power steering apparatus 22 with electric power.
The vehicle body frame 11 includes a pair of left and right upper main frames
55,
56 (only reference numeral 55 representing the upper main frame on the
proximal side is shown), a pair of left and right lower main frames 57, 58
(only
reference numeral 57 representing the lower main frame on the proximal side is
shown), a pair of right and left L-shaped frames 62, 62 (only reference
numeral 62
representing the L-shaped frame on the proximal side is shown), a pair of left
and right upright frames 63, 63 (only reference numeral 63 representing the
upright frame on the proximal side is shown), and a pair of left and right
front
frames 64, 64 (only reference numeral 64 representing the front frame on the
proximal side is shown). The upper main frames 55, 56 are extended in the fore-
aft direction. The lower main frames 57, 58 are disposed downward of the upper
main frames 55, 56 and connected to front ends and rear ends of the upper main
frames 55, 56. The L-shaped frames 62, 62 having substantially an L shape are
mounted to a front portion of the upper main frames 55, 56 so as to support a
middle portion of the input shaft 24. The upright frames 63, 63 also support
the
middle portion of the input shaft 24. The front frames 64, 64 support the
front
carrier 36.
The vehicle body frame 11 further includes front portion inclined portions 66,
66
(only reference numeral 66 representing the front portion inclined portion on
the
proximal side is shown), a pair of left and right inclined frames 67, 67 (only
reference numeral 67 representing the inclined frame on the proximal side is
shown), a pair of left and right sub-inclined frames 68, 68 (only reference
numeral 68 representing the sub-inclined frame on the proximal side is shown),
a
pair of left and right curved frames 71, 71 (only reference numeral 71
representing the curved frame on the proximal side is shown), a pair of left
and
right rear first frames 72, 72 (only reference numeral 72 representing the
rear first
frame on the proximal side is shown), and a pair of right and left rear second
frames 73, 73 (only reference numeral 73 representing the rear second frame on
the proximal side is shown). The front portion inclined portions 66, 66 are
disposed at a front portion of the upper main frames 55, 56. The inclined
frames
WH 12841/cs
CA 02532490 2006-O1-10
-9-
67, 67 are mounted across the front portion inclined portions 66, 66 and the
lower
main frames 57, 58. The sub-inclined frames 68, 68 are mounted across the
inclined frames 67, 67 and the front portion inclined portions 66, 66 so as to
support a lower portion of the motor-driven power steering apparatus 22. The
curved frames 71, 71 are mounted to rear ends of the upper main frames 55, 56
and rear portions of the lower main frames 57, 58, respectively. The rear
first
frames 72, 72 are mounted to upper portions of rear end portions of the upper
main frames 55, 56 so as to support a front portion of the rear carrier 46.
The rear
second frames 73, 73 are mounted on the curved frames 71, 71 so as to support
a
rear portion of the rear carrier 46.
Fig. 2 is a plan view showing the all terrain vehicle according to the
embodiment
of the present invention. At a front portion of the all terrain vehicle 10,
the
vehicle 10 includes an output shaft 81, a center arm 82, and telescopic tie
rods 88,
89. The output shaft 81 is disposed downward of the input shaft 24. The center
arm 82 is mounted on a lower end of the output shaft 81 (to be described in
detail
later) so as to transmit rotation of the handlebar 25 as steer of the front
wheels 12,
13. One end each of the de rods 88, 89 is connected to the center arm 82 via a
corresponding one of ball joints 83, 83. The other end each of the tie rods
88, 89 is
connected to a corresponding one of knuckles 85, 86 on the side of the front
wheels 12, 13 via a corresponding one of ball joints 87, 87. The output shaft
81,
the center arm 82, the ball joints 83, 83, the tie rods 88, 89, and the ball
joints 87,
87 are included in the motor-driven power steering apparatus 22.
Reference numeral 93 represents a steering holder base portion placed across
the
L-shaped frames 62, 62 so as to rotatably support the input shaft 24.
Reference
numeral 94 represents a clutch lever. Reference numeral 95 represents a brake
lever for the front wheels. Reference numerals 96, 96 represent foot rests.
Reference numeral 97 represents a gear change pedal. Reference numeral 98
represents a brake pedal for the rear wheels.
Fig. 3 is a side elevational view showing principal parts of a front portion
of the
all terrain vehicle according to the present invention (an arrow (FRONT) shown
in Fig. 3 points toward front of the vehicle; the same applies hereunder). The
WH 12841/cs
CA 02532490 2006-O1-10
-10-
motor-driven power steering apparatus 22 includes a steering device 105, a
torque sensor portion 106, a power assist portion 107, and a control portion
110.
The steering device 105 steers the front wheels. The torque sensor portion 106
detects a steering torque. The power assist portion 107 generates a power
drive
for providing an assistive force with a steering force. The control portion
110
controls the power assist portion 107 based on the steering torque detected by
the torque sensor portion 106 or the like.
The steering device 105 includes the handlebar 25 (see Fig. 1), the input
shaft 24,
the output shaft 81 connected to the input shaft 24 via the torque sensor
portion
106, the center arm 82 mounted on a lower end portion of the output shaft 81,
the
ball joints 83, 83 (only reference numeral 83 representing the ball joint on
the
proximal side is shown), the tie rods 88, 89 (see Fig. 2), and the ball joints
87, 87
(see Fig. 2).
The input shaft 24 located downward of the handlebar 25 is rotatably supported
on an input shaft bearing portion 91.
The input shaft bearing portion 91 is formed as follows. Specifically, the
steering
holder base portion 93 placed across the left and right L-shaped frames 62, 62
(only reference numeral 62 representing the L-shaped frame on the proximal
side
is shown) is fastened to a holder tab 108 fitted to the steering holder base
portion
93 via a bushing (not shown). Reference numerals 111, 112 represent a bolt and
a
nut, respectively, for attaching the holder tab 108 to the steering holder
base
portion 93. There is provided a pair of left and right ones of bolts and nuts.
The L-shaped frames 62, 62 are connected together with a cross pipe 114. The
cross pipe 114 is a lock member including an upward protruding tab 115 that
runs substantially in parallel with the input shaft 24.
The upward protruding tab 115 is a member functioning as a stopper for
restricting a swing range of an arm tab 116 fitted to the input shaft 24.
Specifically, the upward protruding tab 115 is a stopper for restricting the
range
of the rotational angle of the input shaft 24.
WH 12841/cs
CA 02532490 2006-O1-10
-11-
The input shaft 24 and the output shaft 81 constitute a steering shaft 118.
The output shaft 81 is rotatably supported by an output shaft bearing portion
120
disposed downwardly of a sensor housing 119 included in the torque sensor
portion 106.
The output shaft bearing portion 120 is supported on a bottom plate 121
mounted on the left and right sub-inclined frames 68, 68 (only reference
numeral
68 representing the sub-inclined frame on the proximal side is shown). A
reduction gear 126 included in the power assist portion 107 is also supported
on
the bottom plate 121. Reference numeral 127 represents a bolt (showing only
one
of a plurality of bolts installed) for mounting the reduction gear 126 to the
bottom plate 121.
The torque sensor portion 106 is a torsion bar 123 disposed between the side
of
the input shaft 24 and the side of the output shaft 81. When the input shaft
24 is
turned through operation of the handlebar 25 (see Fig. 2), a relative
rotational
angle is produced in the input shaft 24 and the output shaft 81, which twists
the
torsion bar 123. An amount of this twist is translated to a corresponding
value of
torque to find the steering torque.
The power assist portion 107 includes an electric motor 125, a clutch (not
shown),
and the reduction gear 126. The clutch is inserted between an output shaft of
the
electric motor 125 and a middle portion of the output shaft 81. The reduction
gear 126 includes a worm gear and a worm wheel.
The control portion 110 controls the power assist portion 107 based on the
steering torque detected by the torque sensor portion 106, a steering angle of
the
handlebar 25 (see Fig. 1), a vehicle speed of the all terrain vehicle 10, and
other
process data available during running of the vehicle. Reference numeral 128
represents a bracket mounted on the L-shaped frame 62 so as to support the
control portion 110.
WH 12841/cs
CA 02532490 2006-O1-10
-12-
Fig. 4 is a cross-sectional view showing an output shaft lower end support
portion according to the embodiment of the present invention. The output shaft
bearing portion 120 includes a shaft support member 132, a bearing 133, and
sealing members 134, 135. The shaft support member 132 is mounted at a central
portion of the bottom plate 121. The bearing 133 is mounted on the shaft
support
member 132 so as to support rotatably the output shaft 81. The sealing members
134, 135 protect the bearing 133 from dust and the like. Reference numeral 137
represents a snap ring for preventing the bearing 133 from coming off the
shaft
support member 132. Reference numeral 138 represents a collar.
The shaft support member 132 includes a downward protrusion portion 132a.
The downward protrusion portion 132a is formed on a forward side of the
vehicle so as to protrude downwardly substantially along the output shaft 81.
Female splines 82a formed in the center arm 82 are in splined connection with
male splines 81a formed on the lower end portion of the output shaft 81.
The ball joint 83 is a member mounted to a rear portion of the center arm 82
with
a bolt portion 83a disposed on an end portion of the ball joint 83 and a nut
141.
Fig. 5 is a cross-sectional view taken along line 5-5 of Fig. 4. The center
arm 82 is
a member integrating side protrusion portions 82b, 82c with tie rod connection
portions 82d, 82e. The side protrusion portions 82b, 82c are disposed leftward
and rightward, respectively, of the female splines 82a. The tie rod connection
portions 82d, 82e are connected to the tie rods 88, 89 via the ball joints 83,
83,
respectively.
When the center arm 82 is rotated as the output shaft 81 rotates, either one
of the
side protrusion portions 82b, 82c abuts on the downward protrusion portion
132a of the shaft support member 132 (see Fig. 4) so that a rotation range is
restricted. The center arm 82 is positioned as shown in Fig. 5 when the
handlebar
25 (see Fig. 2) is in a position equivalent to the vehicle's traveling in a
straight
ahead direction. 01 represents a swing angular range of the center arm 82
rotating in the clockwise and counterclockwise directions from the position
WH 12841/cs
CA 02532490 2006-O1-10
-13-
equivalent to the vehicle's traveling in the straight ahead direction. The
swing
angular range also represents a rotational angular range of the output shaft
81.
The side protrusion portions 82b, 82c and the downward protrusion portion 132a
form part of an output shaft stopper mechanism 143.
Fig. 6 is a cross-sectional view taken along line 6-6 of Fig. 3. When the arm
tab
116 is swung as the input shaft 24 rotates, side protrusion portions 116a,
116b of
the arm tab 116 abuts on the upward protruding tab 115 on the side of the
cross
pipe 114 so that the swing range is restricted. The arm tab 116 is positioned
as
shown in Fig. 6 when the handlebar 25 (see Fig. 2) is in the position
equivalent to
the vehicle's traveling in the straight ahead direction. 82 represents a swing
angular range of the arm tab 116 rotating in the clockwise and
counterclockwise
directions from the position equivalent to the vehicle's traveling in the
straight
ahead direction. The swing angular range also represents a rotational angular
range of the input shaft 24. The side protrusion portions 116a, 116b and the
upward protruding tab 115 form part of an input shaft stopper mechanism 145.
As described with reference to Figs. 3, 5, and 6 in the foregoing, the present
invention is applied to the all terrain vehicle 10 (see Fig. 1) having the
input shaft
24 disposed on the side of the handlebar 25 and the output shaft 81 disposed
on
the side of the front wheels 12, 13 (see Fig. 1) as left and right wheels.
More
specifically, the input shaft 24 and the output shaft 81 are connected
together
through the torque sensor portion 106 of the motor-driven power steering
apparatus 22 and the electric motor 125 as the power assist motor included in
the
motor-driven power steering apparatus 22 is driven in accordance with the
relative rotational angle in the input shaft 24 and the output shaft 81. The
present invention is characterized by comprising: the side protrusion portions
116a, 116b functioning as a first lock member secured to the input shaft 24;
the
upward protruding tab 115 functioning as a first stopper secured the vehicle
body at positions corresponding to the side protrusion portions 116a, 116b so
as
to restrict the swing range of the side protrusion portions 116a, 116b; the
side
protrusion portions 82b, 82c functioning as a second lock member secured to
the
output shaft 81; and the downward protrusion portion 132a functioning as a
WH 12841/cs
CA 02532490 2006-O1-10
-14-
second stopper secured the vehicle body at positions corresponding to the side
protrusion portions 82b, 82c so as to restrict the swing range of the side
protrusion portions 82b, 82c.
The all terrain vehicle 10 includes the side protrusion portions 116a, 116b on
the
side of the input shaft 24, the upward protruding tab 115 on the side of the
vehicle body, the side protrusion portions 82b, 82c on the side of the output
shaft
81, and the downward protrusion portion 132a on the side of the vehicle body.
This means that the upward protruding tab 115 and the downward protrusion
portion 132a are disposed on an upstream side and a downstream side,
respectively, in transmission of the steering force of the motor-driven power
steering apparatus 22. This allows the rotational range of the input shaft 24
through operation of the handlebar 25 to be restricted. Accordingly, even when
the vehicle negotiates a road surface having bumps and dents, it is possible
to
restrict the rotational range of the output shaft 81 that can be varied by the
front
wheels 12, 13 turned forcibly clockwise or counterclockwise by the road
surface.
This makes it possible to maintain positively the relative rotational angle in
the
input shaft 24 and the output shaft 81 within a predetermined angle or less.
Accordingly, it is possible, for example, to prevent an excessive torque from
being applied to the torque sensor portion and thus reduce load on the
electric
motor 125.
The present invention is also characterized in that the upward protruding tab
115
and the downward protrusion portion 132a make the rotational range of the
input shaft 24 equivalent to the rotational range of the output shaft 81, or
more
specifically, 01 = 02.
The rotational range of the input shaft 24 is made to be equal to the
rotational
range of the output shaft 81 because of the upward protruding tab 115 and the
downward protrusion portion 132a. Accordingly, when the side of the input
shaft 24 is locked on the upward protruding tab 115, the side of the output
shaft
81 is invariably locked on the downward protrusion portion 132a. This
eliminates difference in the relative rotational angle in the input shaft 24
and the
output shaft 81, which keeps the electric motor 125 inactive. As a result,
power
WH 12841/cs
CA 02532490 2006-O1-10
-15-
consumption of the electric motor 125 can be reduced and the amount of
discharge from the battery 49 can be suppressed.
The present invention is further characterized in that the input shaft 24 and
the
output shaft 81 are connected via the torsion bar 123.
The input shaft 24 is connected to the output shaft 81 through the torsion bar
123.
Accordingly, the torsion bar 123 can be prevented from being excessively
twisted
by restricting the rotational range of each of the input shaft 24 and the
output
shaft 81 using the upward protruding tab 115 and the downward protrusion
portion 132a, respectively.
As described with reference to Figs. 2 and 5 in the foregoing, the present
invention is further characterized in that the side protrusion portions 82b,
82c are
disposed on the center arm 82 that is mounted on the output shaft 81 and that
connects to the left and right tie rods 88, 89 for steering the right and left
front
wheels 12, 13.
The center arm 82 includes the side protrusion portions 82b, 82c. This allows
the
center arm 82 to serve also as a supporting member for the side protrusion
portions 82b, 82c. The number of parts used can thereby be reduced for the
reduced cost.
As described with reference to Figs. 3 and 5 in the foregoing, the present
invention is further characterized in that the side protrusion portions 116a,
116b
are disposed upward of the input shaft bearing portion 91 and the side
protrusion portions 82b, 82c are disposed downward of the output shaft bearing
portion 120.
The side protrusion portions 116a, 116b on the side of the input shaft 24 and
the
side protrusion portions 82b, 82c on the side of the output shaft 81 are
arranged
away from the torsion bar 123. This helps make it more difficult for a large
torque to be transmitted from the side of the input shaft 24 or the side of
the
WH 12841/cs
CA 02532490 2006-O1-10
-16-
output shaft 81 to the torsion bar 123. As a result, the torsion bar 123 can
be
further prevented from being twisted excessively.
Figs. 7(a) and 7(b) are side elevational views showing principal parts of the
input
shaft stopper mechanism according to other embodiments of the present
invention. Like parts are identified by the same reference numerals as in the
embodiment of the present invention shown in Figs. 3 and 6 and descriptions
therefor will be omitted.
Fig. 7(a) is a view showing an arrangement, in which a cross pipe 114 includes
a
downward protrusion tab 151 and an arm tab 116 is mounted at a position
downward from a holder tab 108 of an input shaft 24, thereby allowing the
downward protrusion tab 151 to restrict the swing range of the arm tab 116.
Side protrusion portions 116a, 116b (only reference numeral 116a representing
the side protrusion portion on the proximal side is shown) of the arm tab 116
and
the downward protrusion tab 151 constitute an input shaft stopper mechanism
153.
Fig. 7(b) is a view showing an arrangement, in which a steering holder base
portion 93 includes an upper protrusion tab 155 disposed on an upper portion
thereof and the upward protrusion tab 155 restricts the swing range of an arm
tab 116.
Side protrusion portions 116a, 116b (only reference numeral 116a representing
the side protrusion portion on the proximal side is shown) of the arm tab 116
and
the upward protrusion tab 155 constitute an input shaft stopper mechanism 156.
It is appropriate that a bracket (not shown) be disposed on an L-shaped frame
62
ahead of the input shaft 24 and the bracket have a protrusion tab so that the
protrusion tab and the arm tab 116 constitute the input shaft stopper
mechanism.
If priority is given to assemblability of the input shaft stopper mechanisms
145
(see Fig. 6), 153 (see Fig. 7(a)), 156 (see Fig. 7(b)) and the output shaft
stopper
mechanism 143 (see Fig. 5) described in the foregoing, the input shaft stopper
WH 12841/cs
CA 02532490 2006-O1-10
-17-
mechanisms 145, 153, 156 and the output shaft stopper mechanism 143 may not
function at the same time.
In this case, by making the input shaft stopper mechanisms 145, 153, 156
function
prior to the output shaft stopper mechanism 143, it is possible to prevent an
excessive torque based on operation of the handlebar by an occupant from
acting
on the torsion bar 123 (see Fig. 3). By making the output shaft stopper
mechanism 143 function prior to the input shaft stopper mechanisms 145, 153,
156, on the other hand, it is possible to prevent an excessive torque based on
a
reaction force of a tire occurring from bumps and dents on the road surface
from
acting on the torsion bar 123.
Fig. 8 is a perspective view showing a right side surface of the all terrain
vehicle
according to the present invention. Fig. 8 shows that the all terrain vehicle
10
includes an opening portion 161 for maintenance disposed downwardly of a side
portion of the seat 44 between the front fender 41 and the rear fender 47.
Fig. 8
also shows that there is a removable vehicle body side cover 162 that forms a
trailing end of the opening portion 161.
Fig. 9 is a perspective view showing principal parts indicating the manual
switch
for shutting down supply of the electric power to the electric motor of the
motor-
driven power steering apparatus according to the embodiment of the present
invention. Fig. 9 shows a condition, in which the seat 44 has been removed
from
the all terrain vehicle 10. Fig. 9 shows that the manual switch 166 (indicated
by a
black dot in Fig. 9), which can shut down the supply of the electric power
from
the battery 49 (see Fig. 1) to the electric motor 25 (see Fig. 3) of the motor-
driven
power steering apparatus 22 (see Fig. 3), is disposed at a cross pipe 165
mounted
across the left and right upper main frames 55, 56 of the vehicle body frame
11,
downward of the seat 44 when the seat 44 is mounted in place.
The seat 44 is installed as follows. Specifically, a protrusion portion (not
shown)
disposed at a front portion on the bottom of the seat 44 is inserted in the
vehicle
body side to lock the seat 44 in position. Then, a hook disposed in a rear
portion
WH 12841/cs
CA 02532490 2006-O1-10
-18-
on the bottom of the seat 44 is locked into the vehicle body side so that the
seat 44
is locked in place.
The seat 44 is opened as follows. Specifically, the hook locked in place in
the
vehicle body side is swung by operating a lever 167 disposed in the rear
portion
of the seat 44. The hook is thereby unlocked from the vehicle body side and
the
rear portion of the seat 44 is opened. In this condition, the protrusion
portion
locked to the vehicle body side is pulled so that the front portion of the
seat 44 is
unlocked. Reference numerals 171, 172 represent cushion rubbers for supporting
the bottom of the rear portion of the seat 44. The cushion rubbers are
disposed
on the side of the vehicle body frame 11.
As described in the foregoing, the manual switch 166 that can shut down the
supply of the electric power to the electric motor 125 is disposed downward of
the seat 44. This arrangement allows the occupant (a rider or a passenger) of
the
vehicle to arbitrarily turn off the manual switch 166 to shut down the supply
of
the electric power to the electric motor 125. The arrangement also allows the
seat
44 to protect the manual switch 166. The manual switch 166 is not therefore
exposed to rainwater, mud, or the like and can be prevented from operating
erratically due to interference from an external environment.
In addition, the battery 49 (see Fig. 1) is disposed at a position (see Fig. 2
also), at
which a maintenance service job is performed by opening the seat 44. This
allows the manual switch 166 to be operated as part of a series of operations
performed for servicing the battery 49, for example, for recharging the
battery 49
or the like. This ensures good operability for the occupant.
Fig. 10 is a perspective view showing principal parts indicating the manual
switch for shutting down the supply of the electric power to the electric
motor of
the motor-driven power steering apparatus according to another embodiment of
the present invention. Fig. 10 shows a condition, in which the vehicle body
side
cover 162 has been removed from the all terrain vehicle 10. Fig. 10 shows that
the engine 17 includes a recoil starter 175 for manually starting the engine
17.
The recoil starter 175 is disposed in a rear portion of the engine 17 inside
the
WH 12841/cs
CA 02532490 2006-O1-10
-19-
vehicle body side cover 162 when the vehicle body side cover 162 is mounted in
place. Fig. 10 further shows that the recoil starter 175 includes a knob 176
mounted on a leading end of a wound rope. Further, there is disposed near the
knob 176, or more specifically, on a bracket 177 mounted on the side of the
vehicle body frame 11 a manual switch 178 (indicated by a black dot in Fig.
10)
that can shut down the supply of the electric power from the battery 49 (see
Fig.
1) to the electric motor 125 (see Fig. 3) of the motor-driven power steering
apparatus 22 (see Fig. 3). Reference numerals 181 to 183 represent cover
mounting portions for removably attaching the vehicle body side cover 162. The
cover mounting portions 181 to 183 are disposed on the side of the vehicle
body
frame 11.
When the engine 17 (see Fig. 1) becomes difficult to start with a starter,
causing
the occupant (the rider or the passenger) to determine that there is a drop in
the
terminal voltage of the battery 49, the vehicle body side cover 162 is removed
and the manual switch 178 is turned off. The knob 176 is then pulled to
operate
the recoil starter 175 and the engine 17 is thereby started.
As described above, operating the manual switch 178 and operating the
knob 176 can be a continuous and successive sequence of operations with
substantially no time intervals therebetween. This contributes to good
operability and ease of use.
Fig. 11 is a perspective view showing principal parts indicating the manual
switch for shutting down the supply of the electric power to the electric
motor of
the motor-driven power steering apparatus according to still another
embodiment of the present invention. Fig. 11 shows that the rear fender 47
made
of resin includes a switch mounting portion 47a disposed on an upper portion
thereof downward of the seat 44. Fig. 11 further shows that a manual switch
186
(indicated by a black dot in Fig. 11), which can shut down the supply of the
electric power to the electric motor 125 (see Fig. 3) of the motor-driven
power
steering apparatus 22 (see Fig. 3), is mounted on the switch mounting portion
47a
via a rubber 185.
WH 12841/cs
CA 02532490 2006-O1-10
-20-
The manual switch 186 is disposed near the lever 167 for opening and closing
the
seat 44. This arrangement allows the manual switch 186 to be operated easily
when the seat 44 is opened. In addition, the manual switch 186 is disposed
downward of the seat 44. This arrangement allows the seat 44 to protect the
manual switch 186.
Moreover, the rubber 185 helps prevent vehicle body vibration from being
easily
transmitted to the manual switch 186. This extends the service life of the
manual
switch 186.
Figs. 12(a), 12(b), and 12(C) are perspective views showing examples of the
manual switch according to the present invention.
The manual switch 166 (or the manual switch 178 (see Fig. 10) or the manual
switch 186 (see Fig. 11)) shown in Fig. 12(a) is a rocker switch including an
operated portion 187 that can be rocked back and forth to select a switch
position
of ON or OFF.
The manual switch 166 (or the manual switch 178 (see Fig. 10) or the manual
switch 186 (see Fig. 11)) shown in Fig. 12(b) is a slide switch including an
operated portion 188 that can be slid into an ON or OFF position, or a snap-
action switch including an operated portion 188 that can be lowered into an ON
or OFF position.
The manual switch 166 (or the manual switch 178 (see Fig. 10) or the manual
switch 186 (see Fig. 11)) shown in Fig. 12(c) is a rotary switch including an
operated portion 189 that can be rotated through a predetermined angle to
select
an ON or OFF position.
In the embodiment of the present invention, the center arm 82 includes the
side
protrusion portions 82b, 82c and the shaft support member 132 includes the
downward protrusion portion 132a as shown in Figs. 4 and 5. The present
invention is not limited to these arrangements. Rather, it is appropriate that
the
side of the output shaft 81 be arranged to include a pair of protrusion
portions
WH 12841/cs
CA 02532490 2006-O1-10
-21-
and a case of the reduction gear 126 be arranged to include a protrusion
portion
functioning as a stopper for restricting the swing range of the pair of the
protrusion portions.
In the present invention, the all terrain vehicle includes the first lock
member on
the side of the input shaft, the first stopper on the side of the vehicle
body, the
second lock member on the side of the output shaft, and the second stopper on
the side of the vehicle body. This means that the first stopper and the second
stopper are disposed on an upstream side and a downstream side, respectively,
in transmission of a steering force of the motor-driven power steering
apparatus.
This allows the rotational range of the input shaft through operation of the
handlebar to be restricted. Accordingly, even when the vehicle negotiates a
road
surface having bumps and dents, it is possible to restrict the rotational
range of
the output shaft that can be varied by the wheels turned forcibly clockwise or
counterclockwise by the road surface. This makes it possible to maintain
positively the relative rotational angle in the input shaft and the output
shaft
within a predetermined angle or less. Accordingly, it is possible, for
example, to
prevent an excessive torque from being applied to the torque sensor portion
and
thus reduce load on the power assist motor.
In an embodiment of the present invention, the first stopper and the second
stopper make the rotational range of the input shaft equivalent to the
rotational
range of the output shaft. Accordingly, when the input shaft is locked on the
first stopper, the output shaft is invariably locked on the second stopper. As
a
result, the power assist motor is not started. Accordingly, power consumption
of
the power assist motor can be reduced and the amount of discharge from the
battery can be suppressed.
In another embodiment of the present invention, the input shaft and the output
shaft are connected via the torsion bar. Accordingly, the torsion bar can be
prevented from being excessively twisted by restricting the rotational range
of
each of the input shaft and the output shaft using the first stopper and the
second
stopper, respectively.
WH 12841/cs
CA 02532490 2006-O1-10
-22-
In another embodiment of the present invention, the second lock member is
disposed on the center arm. This allows the center arm to serve also as the
supporting member for the second lock member. The number of parts used can
thereby be reduced for the reduced cost.
In another embodiment of the present invention, the first lock member is
disposed upward of the bearing portion of the input shaft and the second lock
member is disposed downward of the bearing portion of the output shaft. The
first lock member and the second lock member are arranged away from the
torsion bar. This helps make it more difficult for a large torque to be
transmitted
from the side of the input shaft or the side of the output shaft to the
torsion bar.
As a result, the torsion bar can be further prevented from being twisted
excessively.
The present invention is preferably applicable to all terrain vehicle having a
motor-driven power steering apparatus.
Although various preferred embodiments of the present invention have been
described herein in detail, it will be appreciated by those skilled in the
art, that
variations may be made thereto without departing from the spirit of the
invention or the scope of the appended claims.
WH 12841/cs
