Measuring and testing – Dynamometers – Responsive to torque
Reexamination Certificate
2000-12-20
2002-04-02
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to torque
Reexamination Certificate
active
06363797
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rotational angle detecting device for detecting a rotational angle, a torque detecting device for detecting a torque applied to an input shaft through a torsional angle generated on a connecting shaft for connecting the input shaft and an output shaft, and a steering apparatus for an automobile comprising the torque detecting device.
In an electric power steering apparatus having such a construction that a steering auxiliary motor is driven based on a detection result of a steering torque applied to a steering wheel for steering and the rotating force of the motor is transmitted to a steering apparatus to assisting in steering, there is an advantage that an auxiliary force characteristic corresponding to a running state such as a vehicle speed or a steering frequency can be controlled more easily than a hydraulic power steering apparatus using a hydraulic actuator as a source for generating steering auxiliary force. In recent years, therefore, the coverage of the device has tended to be enlarged.
In the electric power steering apparatus described above, a torque detecting device for detecting a steering torque is required. Therefore, there has been used a torque detecting device having such a construction that an input shaft on the steering wheel side and an output shaft on the steering mechanism side of the steering shaft for connecting the steering wheel and the steering mechanism a re connected to each other through a torsion bar having a small diameter, a relative angular displacement generated in the connecting portion of both shafts is detected with the torsion of the torsion bar through the action of a steering torque and the steering torque (rotational torque) is calculated based on the detection result.
FIG. 1
is a schematic view showing an example of the construction of a torque detecting device applied to a steering apparatus for an automobile which has been proposed in Japanese Patent Application No. 2000-49912 by the present applicant. In the steering apparatus, a steering shaft
3
has such a construction that an input shaft
31
having an upper end connected to a steering wheel
30
and an output shaft
32
having a lower end connected to a pinion
33
of a steering mechanism are connected coaxially through a torsion bar
34
having a small diameter and the steering wheel
30
connects with the steering mechanism. The torque detecting device has the following construction in the vicinity of the connecting portion of the input shaft
31
and the output shaft
32
.
A disk-shaped target plate
2
is externally fixed coaxially to the input shaft
31
in the vicinity of an end portion for connecting the output shaft
32
, and a plurality of targets
20
(ten targets in the drawing) are parallelly disposed on the outer circumferential surface of the target plate
2
. These targets
20
are protrusions formed of a magnetic material which have a partial spiral configuration inclined at almost equal angles with respect to the axial direction of the input shaft
31
to which the target plate
2
is attached as shown in the development view of
FIG. 2
in which the outer circumferential surface of the target plate
2
is developed.
The same target plate
2
as that described above is also fixed externally to the output shaft
32
in the vicinity of the end portion for connecting the input shaft
31
, and a plurality of targets
20
inclined at almost equal angles are matched and arranged in a circumferential direction with the targets
20
on the input shaft
31
side in the axial direction of the output shaft
32
to which the target plate
2
is attached on the outer periphery thereof.
Two sensor boxes
1
a
and
1
b
are provided on the outside of the target plates
2
to face the outer edges of the targets
20
on the outer circumferential surface periphery in the circumferential direction. The sensor boxes
1
a
and
1
b
are fixed and supported in a portion such as a housing which bears the input shaft
31
and the output shaft
32
and does not move. The sensor box
1
a
contains a magnetic sensor
1
A opposed to the target
20
on the input shaft
31
side and a magnetic sensor
2
A opposed to the target
20
on the output shaft
32
side with circumferential positions aligned accurately. Similarly, the sensor box
1
b
contains a magnet sensor
1
B opposed to the target
20
on the input shaft
31
side and a magnetic sensor
2
B opposed to the target
20
on the output shaft
32
side with circumferential positions aligned accurately.
The magnetic sensors
1
A,
1
B,
2
A and
2
B are constituted by using elements having such a property that an electric characteristic (resistance) is changed by the action of a magnetic field, for example, a magnetoresistance effect element (MR element) so that a detection signal can be varied depending on the close portions of the opposed targets
20
. Detection signals V
1
A, V
1
B, V
2
A and V
2
B of the magnetic sensors
1
A,
1
B,
2
A and
2
B are given to a operating unit
4
using a microprocessor provided on the outside of the sensor boxes
1
a
and
1
b.
In the torque detecting device having such a construction, the targets
20
opposite to the magnetic sensors
1
A,
2
A,
1
B and
2
B are protrusions formed of a magnetic material which are arranged with predetermined inclinations in the axial direction on the outer circumferential surfaces of the input shaft
31
and the output shaft
32
. Accordingly, when the input shaft
31
and the output shaft
32
rotate therearound, the magnetic sensors
1
A,
2
A,
1
B and
2
B output detection signals which are varied proportionally depending on a change in the rotational angles of the input shaft
31
and the output shaft
32
while the corresponding targets
20
pass through positions opposed thereto.
At this time, the detection signals of the magnetic sensors
1
A and
1
B correspond to the rotational angle of the input shaft
31
where the targets
20
opposite to the magnetic sensors
1
A and
1
B are provided, and the detection signals of the magnetic sensors
2
A and
2
B correspond to the rotational angle of the output shaft
32
where the targets
20
opposite to the magnetic sensors
2
A and
2
B are provided. Accordingly, the operating unit
4
can calculate the rotational angle of the input shaft
31
from the detection signals of the magnetic sensors
1
A and
1
B, so that the operating unit
4
and the magnetic sensors
1
A and
1
B operate as a rotational angle detecting device for the input shaft
31
. Moreover, the operating unit
4
can calculate the rotational angle of the output shaft
32
from the detection signals of the magnetic sensors
2
A and
2
B, so that the operating unit
4
and the magnetic sensors
2
A and
2
B operate as a rotational angle detecting device for the output shaft
32
.
A difference between the detection signal of the magnetic sensor
1
A and that of the magnetic sensor
2
A or a difference between the detection signal of the magnetic sensor
1
B and that of the magnetic sensor
2
B corresponds to a difference (relative angular displacement) in a rotational angle between the input shaft
31
and the output shaft
32
. The relative angular displacement corresponds to a torsional angle generated on the torsion bar
34
connecting the input shaft
31
and the output shaft
32
under the action of a rotational torque applied to the input shaft
31
. Accordingly, the rotational torque applied to the input shaft
31
can be calculated based on the difference in the above mentioned detection signal.
In the torque detecting device described above, the detection signals of the magnetic sensors
1
A,
2
A,
1
B and
2
B have unstable peak values because a great non-linearly change region is generated in the vicinity of both ends of the target
20
and a relatively small linearly change region is changed proportionally to a change in the rotational angles of the input shaft
31
and the output shaft
32
as shown in the waveform chart of
FIG. 3
, and it is difficult to calcula
Koyo Seiko Co. Ltd.
Noori Max
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