Measuring and testing – Dynamometers – Responsive to torque
Reexamination Certificate
1998-11-23
2001-05-01
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to torque
Reexamination Certificate
active
06223608
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a torque detector for detecting torque without direct contact when an external force is applied to the rotating shaft of an automobile power-steering mechanism, etc.
2. Description of the Related Art
In an automobile power-steering mechanism, it is necessary to detect the amount of torque being applied to the steering wheel to determine the amount of power assistance required. Torque detectors for this purpose have been proposed, such as that disclosed in Utility Model Laid Open No. 1-180737, for example.
As shown in
FIG. 6
, the torque detector comprises: an upper shaft
101
, which is attached to a steering wheel (not shown); a lower shaft
102
, which is attached to the pinion gear of a steering mechanism (not shown); a torsion bar
103
, which is disposed on the central axis of the upper shaft
101
and the lower shaft
102
and is connected to the two shafts so as to be elastic in the direction of twisting; a case
105
, which rotatably supports the upper shaft by means of a bearing
104
; a bobbin
106
, which is disposed within the case
105
; first and second movable magnetic cylinders
107
,
108
, which are composed of soft ferromagnetic material and are secured to the upper shaft; third and fourth movable magnetic cylinders
109
,
110
, which are composed of soft ferromagnetic material and are secured to the lower shaft; and first to fourth coils
111
,
112
,
113
,
114
, which are wound around the bobbin within the case
105
.
The first and third movable magnetic cylinders
107
,
109
sit side by side in the axial direction and first and third toothed portions
107
a
,
109
a
are disposed in the respective facing edges. The first coil
111
is disposed so as to surround these toothed portions. The second and fourth movable magnetic cylinders
108
,
110
also sit side by side in the axial direction and second and fourth toothed portions
108
a
,
110
a
are disposed in the respective facing edges. The second coil
112
is disposed so as to surround these toothed portions. The third and fourth coils
113
,
114
are disposed so as to surround the third and fourth movable magnetic cylinders
109
,
110
, which are secured to the lower shaft
102
.
Next, the operation of the above conventional example will be explained. When torque is applied to the upper shaft
101
by the steering wheel, torsional deformation occurs in the torsion bar
103
, and angular shear occurs between the first movable magnetic cylinder
107
and the third movable magnetic cylinder
109
and between the second movable magnetic cylinder
108
and the fourth movable magnetic cylinder
110
, which are attached to the upper shaft
101
and the lower shaft
102
, respectively.
Firstly, to explain the operation between the first and third movable magnetic cylinders
107
,
109
, the surface area of the overlap which forms a magnetic circuit between the first and third toothed portions
107
a
and
109
a
disposed on each of the movable magnetic cylinders changes, resulting in a change in the inductance in the first coil
111
. The torque can be determined by detecting the change in inductance by means of a detection circuit (not shown). However, the inductance in the first coil
111
is changed not only by torque but also by temperature, and temperature is compensated for by detecting the inductance in the third coil
113
, whose inductance is not affected by the twisting of the torsion bar
103
.
The operation between the second and fourth movable magnetic cylinders
108
,
110
is identical, so that the surface area of the overlap between the second and fourth toothed portions
108
a
and
110
a
changes, resulting in a change in the inductance in the second coil
112
. The torque is determined by detecting the change in inductance. Temperature is compensated for by detecting the inductance in the fourth coil
114
.
Thus, this dual construction comprising a first detection set comprising the first and third movable magnetic cylinders
107
,
109
and the first and third coils
111
,
113
, and a second detection set, which is capable of exactly the same measurements, comprising the second and fourth movable magnetic cylinders
108
,
110
and the second and fourth coils
112
,
114
, performs a dual safety function which enables the system to operate on the output of one of the detection sets when the other malfunctions, such as by wire breakage, etc.
The conventional torque detector requires a torsion bar
103
, which is an elastic member which deforms in proportion to the torque, in addition to the first to fourth movable magnetic cylinders
107
to
110
, which change the inductance in the first and second coils
111
,
112
, and the large number of parts makes the construction complicated.
Also, each of the toothed portions
107
a
to
110
a
on the first to fourth movable magnetic cylinders
107
to
110
are of complicated shape and require manufacture by cutting, and manufacture is therefore troublesome and expensive.
In addition, simultaneous provision of a temperature compensation function and a dual safety function, which guards against wire breakage in the coils, etc., basically requires four coils. The conventional example required two pairs of movable magnetic cylinders provided with toothed portions corresponding to the four coils.
SUMMARY OF THE INVENTION
The present invention aims to solve the above problems and an object of the present invention is to provide a torque detector which can detect torque by means of a simple construction.
To this end, according to the present invention, there is provided a torque detector comprising: a first shaft and a second shaft, which are acted on mutually by a torque; movable magnetic elements, each of which includes an element body, which spans a gap between the first shaft and the second shaft, is secured to the surface of the first shaft and the surface of the second shaft, and deforms elastically in response to the relative displacement between the surface of the first shaft and the surface of the second shaft, which arises as result of relative turning between the first shaft and the second shaft, and soft ferromagnetic wings, which are supported by the element body and change their inclination relative to the axial direction due to the elastic deformation of the element body; and coils which are disposed radially outwards from the wings of the movable magnetic elements, are spaced at specific intervals, and electromagnetically detect the inclination of the wings.
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patent: 5046372 (1991-09-01), Taniguchi et al.
patent: 5115685 (1992-05-01), Jorgensen et al.
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Aw-Musse Abdullahi
Mitsubishi Denki & Kabushiki Kaisha
Noori Max
Sughrue Mion Zinn Macpeak & Seas, PLLC
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