Measuring and testing – Dynamometers – Responsive to torque
Reexamination Certificate
2000-07-27
2002-05-07
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to torque
C073S862333, C180S444000
Reexamination Certificate
active
06382034
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a torque sensing unit employed in a power steering mechanism of a car, etc. and, more particularly, a torque sensing unit for sensing a torque in a non-contact manner when an external force is applied to a rotation shaft and a method of manufacturing the same.
In the prior art, the power steering mechanism in which, when the driver steers the car by turning the steering wheel, the rotating force is applied from the motor to the steering mechanism in response to the torque applied to the steering wheel so as to assist the steering force mechanism has been employed.
In the power steering mechanism, in order to decide a power assisting amount, the torque applied to the steering wheel must be sensed. As the sensing unit, there is the torque sensing unit disclosed in the Unexamined Japanese Patent Application Publication No. Hei 6-174569, for example. The structure of this sensing unit will be explained with reference to FIG.
4
.
In
FIG. 4
, the steering wheel (not shown) is attached to a first shaft
1
, and the pinion gear (not shown) of the steering mechanism is attached to a second shaft
2
. Then, a torsion bar
3
is arranged on center shafts of the first shaft
1
and the second shaft
2
to connect elastically two shafts in the twisting direction. The first shaft
1
is supported rotatably to a cylindrical case
4
, which is fitted to the body of the car, etc., via a bearing
14
a
. A first sleeve
14
a
formed of non-magnetic material is secured to the first shaft
1
. A first cylindrical magnetic element
11
and a second cylindrical magnetic element
12
, both are formed of soft magnetic material, and are secured on an outer periphery of the first sleeve
14
a
at a predetermined interval.
The right end edge of the first magnetic element
11
is formed as a flat plane perpendicular to the shaft center of the first shaft
1
, and rectangular teeth portions
11
a
are formed on the left end edge at an equal pitch along the peripheral direction. The right end edge of the second magnetic element
12
, which opposes to the first magnetic element
11
, is formed as a flat plane perpendicular to the shaft center of the first shaft
1
, and rectangular teeth portions
12
a
are formed on the left end edge at an equal pitch along the peripheral direction. A teeth width dimension of the teeth portion
12
a
is set substantially equal to a width dimension of a notched portion of the teeth portion
12
a.
A second sleeve
14
b
formed of non-magnetic material is secured to the second shaft
2
, and a third cylindrical magnetic element
13
formed of non-magnetic material is secured to an outer periphery of the second sleeve
14
b
. A plurality of teeth portions
13
a
that have the same width, the same shape, and the same pitch as those of the teeth portion formed on the second magnetic element
12
are formed on the right end edge of the third magnetic element
13
.
Yokes
22
a
,
22
b
, which are formed to have a cup-shaped sectional shape having inner flanges and formed of soft magnetic material are secured onto the inside of the case
4
. The yoke
22
a
has a length to extend the first magnetic element
11
and the second magnetic element
12
such that the center portion in the axial direction can be arranged at a position opposing to the first magnetic element
11
and the second magnetic element
12
. Also, the yoke
22
b
has a length to extend the second magnetic element
12
and the third magnetic element
13
such that the center portion in the axial direction can be arranged at a position opposing to the second magnetic element
12
and the third magnetic element
13
.
A first coil
21
a
for temperature compensation and a second coil
21
b
for torque sense are wound on the yokes
22
a
,
22
b
along the peripheral direction respectively. Then, when the first coil
21
a
and the second coil
21
b
are connected to an oscillator (not shown), the yoke
22
a
together with the first magnetic element
11
and the second magnetic element
12
constitute a magnetic circuit, while the yoke
22
b
together with the second magnetic element
12
and the third magnetic element
13
constitute a magnetic circuit.
Next, an operation of the above torque sensing unit will be explained hereunder. When the torque is applied to the second shaft
2
from the steering wheel, twisted deformation is caused in the torsion bar
3
, so that a relative angular displacement is generated between the first shaft
1
and the second shaft
2
. Then, relative phase difference is generated in the peripheral direction between the second magnetic element
12
and the third magnetic element
13
, which are secured to respective shafts via the sleeves
14
a
,
14
b
respectively. Therefore, opposing areas between the teeth portions
12
a
and the teeth portions
13
a
provided to respective magnetic elements
12
,
13
to serve as magnetic paths are changed. Since the second coil
21
b
constitutes a part of the magnetic circuit which passes the yoke
22
b
, the second magnetic element
12
, and the third magnetic element
13
, the magnetic reluctance of this magnetic circuit is changed to then change the inductance when the opposing areas between the teeth portions
12
a
and the teeth portions
13
a
acting as the magnetic path is changed. Then, if the AC driving current of the frequency several kHz is supplied to the coil to sense the change in the inductance by the sensing circuit (not shown), the torque applied to the torsion bar
3
can be sensed.
Because the inductance of the second coil
21
b
is changed by not only the torque but also the temperature, the temperature compensation is needed. Since both the first magnetic element
11
and the second magnetic element
12
are secured to the first shaft
1
via the sleeve
14
a
, the relative angle between them is not changed by the application of the torque and thus the opposing areas between the teeth portions
11
a
and the teeth portions
12
a
are also not changed. Accordingly, the inductance of the first coil
21
a
which is wound at the middle position between the first magnetic element
11
and the second magnetic element
12
is not changed by the torque. However, since the first coil
21
a
can change its inductance in response to the change in temperature in the same fashion as the second coil
21
b
, the output which is not affected by the temperature and is in proportion to only the torque can be derived by sensing difference of the inductance between the first coil
21
a
and the second coil
21
b.
Next, the method of manufacturing the above torque sensing unit will be explained hereunder. The step of coupling the first shaft
1
and the second shaft
2
with the torsion bar
3
produces easily the angular error. For this reason, in order to fix precisely the rotational phase difference between the magnetic elements at the neutral position, first the first sleeve
14
having the magnetic elements
11
,
12
is secured to the first shaft
1
. Then, the second sleeve
14
b
having the third magnetic element
13
is not secured to the second shaft
2
but merely fitted to the second shaft
2
. After the first shaft
1
and the second shaft
2
are coupled together by the torsion bar
3
, the second sleeve
14
b
is adjusted such that the rotational phase difference between the first sleeve
14
a
and the second sleeve
14
b
is set to a predetermined angle, and then secured to the second shaft
2
.
Since the torque sensing unit in the prior art is fabricated as mentioned above, there are such problems that the manufacturing steps become complicated and a higher cost is brought about.
Also, in the variable reluctance type torque sensing unit in the prior art, since the first shaft and the second shaft are made of steel in normal case, the magnetic flux generated in the coils flow into the magnetic elements as well as the above shafts. However, there is such a problem that, since the magnetic characteristic of the shafts has large variation and also the temperature characterist
Ohashi Yutaka
Yasui Katsuaki
Allen Andre
Noori Max
LandOfFree
Torque sensing unit manufacturing method, sensor module, and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Torque sensing unit manufacturing method, sensor module, and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Torque sensing unit manufacturing method, sensor module, and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2835422