Motor vehicles – Steering gear – With electric power assist
Reexamination Certificate
2001-09-24
2003-04-29
Morris, Lesley D. (Department: 3618)
Motor vehicles
Steering gear
With electric power assist
C180S443000, C180S444000
Reexamination Certificate
active
06554096
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a torque detecting apparatus comprising, for each of an input shaft and an output shaft that are connected with a torsion bar, a rotor; a plurality of targets provided on the rotor so that a region to be detected changes periodically and continuously with rotation of the rotor; and one or a plurality of detecting means for detecting regions of the targets; whereby detecting a torque applied to the input shaft, based on a difference between the regions detected by the detecting means resulting from twist of the torsion bar, and also relates to a steering apparatus for driving an electric motor based on the result of detection of the torque detecting apparatus so as to generate a steering assist force.
There is a type of steering apparatus for automobile, which assists steering by driving the electric motor so as to reduce the driver's load. This steering apparatus comprises an input shaft connected to a steering wheel; an output shaft connected to a steering control wheel through a pinion and a rack; and a torsion bar connecting the input shaft and output shaft together, detects a steering torque applied to the input shaft with a detecting apparatus based on twist generated on the torsion bar, and drives and controls the steering assist electric motor interlocked with the output shaft, based on the steering torque detected by the torque detecting apparatus.
FIG. 1
is a schematic view illustrating schematically an example of the structures of essential portions of a torque detecting apparatus according to a proposal made in Japanese Patent Application Laid-Open No. 2000-352502 (U.S. patent application Ser. No. 09/719003) filed by the present applicant.
FIG. 1
shows an application of this torque detecting apparatus to a steering apparatus, wherein, for example, eight protruding objects (targets)
7
formed of a magnetic material are provided at equal intervals and at a predetermined angle of inclination along a circumferential surface of an intermediate portion (rotor)
6
of an upper shaft (input shaft)
23
of a steering shaft whose upper end is connected to a steering wheel
4
and lower end is connected to a torsion bar
5
. Moreover, in order to detect the approaching position of the protruding object
7
that moves in the axial direction of the upper shaft
23
upon rotation of the upper shaft
23
, an MR sensor
1
(magneto-resistance effect element, that is detecting means) is provided parallel to the intermediate portion
6
with an appropriate space therebetween and fixed to an immovable portion of the body of vehicle.
The upper end of a lower shaft (output shaft)
18
of the steering shaft is connected to the torsion bar
5
, and the lower end thereof is connected to a pinion
10
. Like the upper shaft
23
, eight protruding objects (targets)
9
formed of magnetic material are provided at equal intervals and at a predetermined angle of inclination along a circumferential surface of an intermediate portion (rotor)
8
of the lower shaft
18
. Moreover, in order to detect the approaching position of the protruding object
9
that moves in the axial direction of the lower shaft
18
upon rotation of the lower shaft
18
, an MR sensor
2
(magneto-resistance effect element, that is detecting means) is provided parallel to the lower shaft
18
with an appropriate space therebetween and fixed to an immovable portion of the body of vehicle.
The MR sensor
1
incorporates therein sensors
1
A and
1
B whose electric angle difference is 180° (i.e., for detecting the approaching positions of adjacent different protruding objects
7
) so as to construct a dual system, and detection signals V
1
A and V
1
B indicating the approaching positions of the protruding objects
7
detected by the sensors
1
A and
1
B are respectively supplied to a calculating unit
3
.
The MR sensor
2
incorporates therein sensors
2
A and
2
B whose electric angle difference is 180° (i.e., for detecting the approaching positions of adjacent different protruding objects
9
) so as to construct a dual system, and detection signals V
2
A and V
2
B indicating the approaching positions of the protruding objects
9
detected by the sensors
2
A and
2
B are respectively supplied to the calculating unit
3
.
The MR sensors
1
and
2
are provided so that the detection signals V
1
A and V
2
A are in phase and the detection signals V
1
B and V
2
B are in phase in a condition where no steering torque is applied to the steering wheel
4
and the torsion bar
5
is not twisted.
The twist angle of the torsion bar
5
is at most several degrees, and the calculating unit
3
calculates a steering torque, based on the difference between the detection signals V
1
A and V
2
A or between the detection signals V
1
B and V
2
B, and outputs the torque signal.
In the torque detecting apparatus having such a structure, whenever the upper shaft
23
and the lower shaft
18
rotate 45°, the protruding objects
7
and
9
closest to the detection faces of the respective sensors
1
A,
1
B and sensors
2
A,
2
B reciprocate in the axial direction of the upper shaft
23
and lower shaft
18
. It is possible to arrange the positions of the protruding objects
7
and
9
closest to the detection faces of the respective sensors
1
A,
1
B and sensors
2
A,
2
B, in the axial direction of the upper shaft
23
and lower shaft
18
, to correspond to the rotational angles of the upper shaft
23
and lower shaft
18
.
Therefore, if the detection signals of the sensors
1
A,
1
B and sensors
2
A,
2
B are set to have a linear relation with every 45° rotational angle of the upper shaft
23
and lower shaft
18
, it is possible to detect the rotational angles of the upper shaft
23
and lower shaft
18
based on the respective detection signals of the sensors
1
A,
1
B and sensors
2
A,
2
B by using counting of the number of times of up and down in the detection signals of the sensors
1
A,
1
B and sensors
2
A,
2
B. In addition, it is also possible to discriminate whether the sensors
1
A,
1
B and sensors
2
A,
2
B have detected the approaching positions of the respective protruding objects
7
and
9
.
For example, in the case where the detection signals of the sensors
1
A,
1
B and sensors
2
A,
2
B are set to have a similar relation with the rotational angle (steering angle) of the upper shaft
23
and lower shaft
18
, when the upper shaft
23
and lower shaft
18
are rotated, the detection signals of the sensors
1
A,
1
B and sensors
2
A,
2
B show voltage waveforms of a cycle of 45°, and the rotational angles of the upper shaft
23
and lower shaft
18
can be detected by the detection signals of the sensors
1
A,
1
B and sensors
2
A,
2
B, respectively.
Here, if a steering torque has been applied to the steering wheel
4
and the torsion bar
5
has a twist angle, the detection signals of the sensors
1
A and
2
A and the detection signals of the sensors
1
B and
2
B have a voltage difference &Dgr;V according to the twist angle, and therefore it is possible to obtain the twist angle by calculating the voltage difference &Dgr;V with the calculating unit
3
and to output a torque signal representing the steering torque.
The above-described torque detecting apparatus is constructed by providing the rotor
6
on the upper shaft
23
of the steering shaft as an intermediate portion thereof and providing the rotor
8
on the lower shaft
18
as an intermediate portion thereof, but it is difficult to provide the rotors
6
and
8
by precisely keeping a coaxial relation between their rotation axes and the upper shaft
23
and lower shaft
18
, and if their relation is illustrated in an emphasized manner, as shown in
FIG. 2
, the rotation axes of the rotors
6
and
8
are mutually deflected.
Therefore, the positional relation between the MR sensor
1
and the protruding objects
7
and the positional relation between the MR sensor
2
and the protruding objects
9
are not the same depending on the rotations of the rotor
6
and rotor
8
, and, if the de
Birch Stewart Kolasch & Birch, LLP.
Koyo Seiko Co. Ltd.
Morris Lesley D.
Yeagley Daniel
LandOfFree
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