Motor vehicles – Steering gear – With electric power assist
Reexamination Certificate
2002-08-12
2004-03-16
Morris, Lesley D. (Department: 3611)
Motor vehicles
Steering gear
With electric power assist
Reexamination Certificate
active
06705422
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electric power steering device equipped with an anti-theft function and a method for manufacturing same.
DESCRIPTION OF THE RELATED ART
A conventional electric power steering device
101
equipped with an anti-theft function, which is illustrated in
FIG. 6
, comprises sensor housing
102
and a steering shaft
103
having a part which is surrounded by this sensor housing
102
. A lock member (omitted from the drawings), which is supported by a member fixed to the vehicle body side, is received by a receiving portion
104
provided on the outer circumference of the steering shaft
103
on the exterior of the sensor housing
102
. Thereby, the rotation of the steering shaft
103
is restricted to provide an anti-theft function. In this conventional example, a tubular member
109
is integrated with the steering shaft
103
on its outer circumference by press fitting, and the receiving portion
104
is constituted by the inner surface of a recessed portion formed on the tubular member. A torque sensor
105
having a magnetic flux generating coil
108
, which is provided so as to surround the steering shaft
103
, is provided within the sensor housing
102
. This torque sensor
105
has input and output shafts
111
,
112
which constitute the steering shaft
103
, and which are mutually connected so as to be capable of elastic relative rotation. The torque which is transmitted by the steering shaft
103
is detected on the basis of changes in the relative position in the circumferential direction of a first magnetic flux transmitting member
115
which is attached to the input shaft
111
and a second magnetic flux transmitting member
116
which is attached to the output shaft
112
. A driving gear
107
which meshes with a driven gear
106
provided on the outer circumference of the output shaft
112
is driven by an electric actuator (omitted from the drawings), and the auxiliary steering power generated by this electric actuator is transmitted to the steering shaft
103
. The coil
108
is disposed in a position between the receiving portion
104
and the driven gear
106
, in which the generated magnetic flux is transmitted through the two magnetic flux transmitting members
115
,
116
. The outer diameter D
1
of the receiving portion
104
is made smaller than the inner diameter D
3
of the coil
108
, and the outer diameter D
2
of the driven gear
106
is made larger than the inner diameter D
3
of the coil
108
. The steering shaft
103
has an upper shaft
113
which is a separate entity to the input and output shafts
111
,
112
, and the receiving portion
104
is provided on the outer circumference of this upper shaft
113
. The upper shaft
113
is connected via a pin
120
to the input shaft
3
so as to be capable of rotation in accompaniment therewith. Further, a tubular column
119
is provided surrounding the upper shaft
113
and disposed in a position which is unchanging with respect to the sensor housing
102
.
Conventionally, when manufacturing the aforementioned electric power steering device
101
, the input and output shafts
111
,
112
, the upper shaft
113
, the magnetic flux transmitting members
115
and
116
, and the driven gear
106
are formed into an assembly, and this assembly is inserted into the sensor housing
102
. Since the outer diameter D
2
of the driven gear
106
is larger than the inner diameter D
3
of the coil
108
, the driven gear
106
cannot be passed through the coil
108
. Therefore, the assembly is inserted into the sensor housing
102
from the upper shaft
113
side.
When the aforementioned electric power steering device
101
is used in a vehicle in which the outer diameter of the steering shaft
103
is large, the outer diameter D
1
of the receiving portion
104
provided on the outer circumference of the steering shaft
103
also becomes large. Moreover, when the receiving portion
104
is mounted onto the steering shaft
103
via a torque limiter, which prevents excessive torque from acting upon the steering wheel, so as to improve the anti-theft function by preventing damage of the receiving portion
104
or the lock member, the outer diameter D
1
of the receiving portion
104
becomes even larger. Hence, the outer diameter D
1
of the receiving portion
104
becomes larger than the inner diameter D
3
of the coil
108
. As a result, not only the driven gear
106
, but also the receiving portion
104
is unable to pass through the coil
108
, and therefore the assembly formed from the input and output shafts
111
,
112
, the upper shaft
113
, the magnetic flux transmitting members
115
and
116
, and the driven gear
106
cannot be inserted into the sensor housing
102
. Consequently, enlarging the inner diameter D
3
of the coil
108
has been considered. However, when the inner diameter D
3
of the coil
108
becomes larger, the entire device is increased in size, and problems arise in that the mounting of the steering device on the vehicle becomes difficult and costs increase.
An object of the present invention is to provide an electric power steering device equipped with an anti-theft function and a method for manufacturing same which can solve the aforementioned problems.
SUMMARY OF THE INVENTION
The electric power steering device equipped with an anti-theft function according to the present invention comprises a sensor housing, a steering shaft having a part which is surrounded by this sensor housing, and a torque sensor having a magnetic flux generating coil which is provided within the sensor housing so as to surround the steering shaft. This torque sensor has input and output shafts which constitute the steering shaft, and which are mutually connected so as to be capable of elastic relative rotation. The torque that is transmitted by the steering shaft is detected on the basis of changes in the output of the coil in response to changes in the relative position in the circumferential direction of a first magnetic flux transmitting member which is attached to the input shaft and a second magnetic flux transmitting member which is attached to the output shaft. An auxiliary steering power transmitting driven gear is provided on the outer circumference of the output shaft. The steering shaft has an upper shaft which is provided as a separate entity to the input and output shafts. A receiving portion is provided on the outer circumference of this upper shaft, and the coil is disposed in a position between the receiving portion and the auxiliary steering power transmitting driven gear in which the generated magnetic flux is transmitted through the two magnetic flux transmitting members. A lock member which is supported by a member fixed to the vehicle body side is received by the receiving portion, whereby the rotation of the steering shaft is restricted.
The manufacturing method of the present invention is characterized in that, upon manufacture of the electric power steering device equipped with an anti-theft function, the outer diameter of the receiving portion and the outer diameter of the auxiliary steering power transmitting driven gear are made to be larger than the inner diameter of the coil, and the sensor housing, coil, mutually connected input and output shafts, the two magnetic flux transmitting members and the driven gear are formed into an assembly, whereupon the upper shaft with the receiving portion provided on its outer circumference is connected to the input shaft so as to be capable of rotation in accompaniment therewith.
According to this method of the present invention, the outer diameter of the receiving portion and the outer diameter of the auxiliary steering power transmitting driven gear are made to be larger than the inner diameter of the coil, and hence this method can respond to such cases as when the receiving portion is provided on the outer circumference of a steering shaft with a large outer diameter, or when the receiving portion is mounted onto the steering shaft via a torque limiter in order to improve the anti-the
Jordan and Hamburg LLP
Koyo Seiko Co. Ltd.
Luby Matthew
Morris Lesley D.
LandOfFree
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