Motor vehicles – Having four wheels driven
Reexamination Certificate
2001-03-30
2003-03-11
Hurley, Kevin (Department: 3611)
Motor vehicles
Having four wheels driven
C192S044000
Reexamination Certificate
active
06530447
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a two-wheel drive/four-wheel drive switching device for a vehicle.
2. Description of Background Art
A vehicle which is capable of running while switching between two-wheel drive and four-wheel drive has previously been known.
FIGS. 4 and 5
illustrate an example of such a vehicle. In both figures, the vehicle, indicated by reference numeral
1
, is substantially composed of a body frame
3
with an engine
2
mounted centrally thereon. Front wheels
4
and rear wheels
5
are disposed on both sides of front and rear portions of the body frame
3
. A steering handle
6
is disposed at a front upper position of the body frame
3
to steer the front wheels
4
. A fuel tank
7
is mounted to the body frame
3
above the engine
2
. Furthermore, a seat
8
is mounted behind the fuel tank
6
.
As shown in
FIG. 5
, the front wheels
4
are supported vertically movably by suspension systems
9
disposed on both sides of the front portion of the body frame
3
. Likewise, the rear wheels
5
are supported vertically movably by suspension systems
10
disposed on both sides of the rear portion of the body frame
3
.
A final reduction gear
13
for the front wheels
4
and a final reduction gear
14
for the rear wheels
5
, respectively, are mounted in front and rear central portions of the body frame
3
. The final reduction gears
13
and
14
are connected to the engine
2
through propeller shafts
11
and
12
, respectively. The right and left front wheels
4
and the right and left rear wheels
5
are connected respectively to the final reduction gear
13
for the front wheels
4
and the final reduction gear
14
for rear wheels
5
.
For example, between the final reduction gear
13
for the front wheels
4
and the propeller shaft
11
is disposed a two-wheel drive/four-wheel drive switching device which makes and breaks the transfer of power to the front wheels
4
, thereby switching between a rear-wheel drive mode and a four-wheel drive mode.
Alternatively, the two-wheel drive/four-wheel drive switching device is disposed between the rear propeller shaft
12
and the final reduction gear
14
for the rear wheels
5
to switch over between a front-wheel drive mode and a four-wheel drive mode.
This switching between a front-wheel drive mode and a four-wheel drive mode is conducted by the driver, as necessary, according to the state of the road surface and the running mode of the vehicle.
For example, a switching device of such a structure as shown in
FIG. 6
has been proposed to be used as the two-wheel drive/four-wheel drive switching device of the background art.
Also in
FIG. 6
, a two-wheel drive/four-wheel drive switching device, indicated by reference numeral
15
, is made up of two input shaft halves
16
a
and
16
b
. The input shaft halves
16
a
and
16
b
are formed by axially bisecting an input shaft
16
of the final reduction gear
13
for the front wheels
4
and butting the input shaft halves
16
a
and
16
b
in alignment with each other. Furthermore, a switching unit
17
is provided for connecting and disconnecting the input shaft halves
16
a
and
16
b
from and to each other.
To be more specific, a cylindrical positioning protrusion
18
is formed centrally on an end face of the input shaft half
16
a
, which is positioned on the final reduction gear
13
side. Furthermore, a positioning recess
19
for rotatably fitting with the positioning protrusion
18
is formed centrally on an end face of the input shaft half
16
b
, which is positioned remote from the final reduction gear side. Both input shaft halves
16
a
and
16
b
are in butting relationship with each other and the positioning protrusion
18
and the positioning recess
19
are fitted together, whereby both input shaft halves
16
a
and
16
are aligned and connected with each other so as to be relatively rotatable with respect to each other.
Outer peripheral surfaces of the abutting portions of both input shaft halves
16
a
and
16
b
are splined (not shown) and the switching unit
17
is disposed so as to surround the abutting portions.
The switching unit
17
has a splined inner surface and is slidably fitted to the abutting portions of both input shaft halves
16
a
and
16
b
. The switching unit
17
is made up of a switching ring
20
adapted to be engaged with and disengaged from each of the splines and a drive mechanism
21
constituted by a solenoid. The drive mechanism
21
causes the switching ring
20
to slide axially with respect to both input shaft halves
16
a
and
16
b
to selectively move to a position where the switching ring
20
is brought into engagement with the spline of only one input shaft halve
16
a
and a position where the switching ring is brought into engagement with the splines of both input shaft halves
16
a
and
16
b.
In the two-wheel drive/four-wheel drive switching device
15
, the switching ring
20
is moved in one direction by the drive mechanism
21
and is brought into engagement with only one input shaft half
16
a
to cut off the transfer of driving force to the front wheels
4
, affording a two-wheel drive mode of driving only the rear wheels. Furthermore, the switching ring
20
, in an engaged state thereof with one input shaft half
16
a
, is slid into engagement with the other input shaft half
16
b
to connect both input shaft halves
16
a
and
16
b
with each other, thereby transmitting the driving force to the front wheels
4
and thus affording a four-wheel drive mode in which the front and rear wheels
4
and
5
are driven simultaneously.
In the two-wheel drive/four-wheel drive switching device
15
of the background art, there remains the following problems to be solved.
In the case where a braking operation is performed with the rear brake in a two-wheel drive mode, for example, a braking force is exerted on the rear wheels
5
and not on the front wheels
4
, so that a difference in brake feeling between two- and four-wheel drive modes occurs. The same problem occurs under the action of engine braking as well.
For solving such a problem with the background art device, it is necessary to construct a brake setting which is consistent in both two-wheel drive and four-wheel drive modes. This can be done by using a complicated control mechanism, which, however, results in an increase of cost.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above-mentioned problems of the background art, and it is an object of the present invention to provide a two-wheel drive/four-wheel drive switching device capable of exerting both rear braking and engine braking on the front and rear wheels.
According to a first aspect of the present invention, there is provided a two-wheel drive/four-wheel drive switching device for a vehicle which is capable of running while switching between two-wheel drive and four-wheel drive, wherein when the rear wheel speed becomes lower than the front wheel speed in a two-wheel drive mode, switching is made to the four-wheel drive mode.
According to a second aspect of the present invention, there is provided a two-wheel drive/four-wheel drive switching device for a vehicle, wherein a switching unit is provided in a power transfer mechanism disposed between an engine and front wheels or between the engine and rear wheels. The switching unit functions to make and break the transfer of power in the power transfer mechanism, and comprises a drive shaft connected to a drive side, a driven shaft fitted to the drive shaft with an annular clearance therebetween, a plurality of engaging and disengaging members disposed within the clearance between the drive shaft and the driven shaft and brought into engagement with and disengagement from opposed surfaces of both drive and driven shafts to connect and disconnect the shafts from and to each other, a switching mechanism for positioning the engaging/disengaging members selectively at a connecting position and a disconnecting position for the drive shaft and the driv
Seki Bunzo
Suzuki Hideaki
LandOfFree
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