Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
2003-02-27
2004-04-13
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207250
Reexamination Certificate
active
06720762
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to rotation-angle detecting devices, and more particularly, to a low-profile and compact rotation-angle detecting device having a simple configuration.
2. Description of the Related Art
A known type of rotation-angle detecting device will be described with reference to
FIGS. 7 and 8
.
FIG. 7
is a plan view showing the inner configuration of the rotation-angle detecting device, and
FIG. 8
is an explanatory view showing the output characteristics of the rotation-angle detecting device with respect to the rotation angle.
Referring to
FIG. 7
, a rotating member
23
is mounted inside a case body
22
made of insulating resin. The rotating member
23
is made of insulating resin, is shaped like a cylinder, and is rotatably supported by the case
22
. A shaft of a steering wheel of an automobile extends through the rotating member
23
so that the rotating member
23
is rotated clockwise and counterclockwise together with the steering wheel. A helical gear
23
a
having a plurality of teeth is formed on the entire outer peripheral surface of the rotating member
23
.
A rotation shaft
29
is rotatably provided inside the case body
22
. A driving gear
28
is fixed to the rotation shaft
29
. A helical gear
28
a
having a plurality of teeth is formed on the entire outer peripheral surface of the driving gear
28
, and is meshed with the helical gear
23
a
of the rotating member
23
. A first ring-shaped magnet
25
A having a pair of magnetic poles on its outer peripheral surface is provided adjacent to the driving gear
28
so that it is coaxial with the rotation shaft
29
. The rotation shaft
29
is made of metal such as brass or aluminum, and has a spiral screw groove
29
a
formed from the center to one end. A moving member
24
is engaged with the screw groove
29
a.
The moving member
24
has a through hole extending from one end face to the other end face in the moving direction. The through hole has, on its inner peripheral surface, an internal thread (not shown) to be meshed with the screw grove
29
a
formed on the rotation shaft
29
. A second magnet
25
B having a pair of magnetic poles is fixedly attached to the lower surface of the moving member
24
. The moving member
24
is guided inside the case body
22
so as to linearly move in the axial direction of the rotation shaft
29
. When the rotating member
23
rotates and the driving gear
28
and the rotation shaft
29
also rotate, the moving member
24
and the second magnet
25
B reciprocally move in the axial direction of the rotation shaft
29
.
A substrate
30
on which first and second Hall elements (detection means)
26
A and
26
B are mounted is fixed in the lower part of the case body
22
. A pair of first Hall elements
26
A face the first magnet
25
A, and the second Hall element
26
B faces the second magnet
25
B. When the rotation shaft
29
rotates, the first Hall elements
26
A detect the magnetic displacement of the first magnet
25
A, and output predetermined sinusoidal waves
101
and
102
shown in
FIG. 8
as first detection signals in response to the rotation. When the second magnet
25
B is reciprocally moved in the axial direction of the rotation shaft
29
along the screw groove
29
a
, the second Hall element
26
B detects the magnetic displacement of the second magnet
25
B, and outputs a signal
103
, which linearly changes over the entire rotation angle range of the steering wheel, as a second detection signal. The absolute angle of the rotation angle (steering angle) of the steering wheel can be detected on the basis of the first and second detection signals output from the first and second Hall elements
26
A and
26
B.
In the above-described known rotation-angle detecting device, however, a driving gear with a helical gear to be meshed with the helical gear on the outer peripheral surface of the rotating member must be provided, and the driving gear and the rotating member are arranged so that their rotation axes are orthogonal to each other. Consequently, the thickness and size of the rotation-axis detecting device are increased by of the diameter of the driving gear.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a low-profile compact rotation-angle detecting device that can measure the absolute angle with a simple configuration.
In order to achieve the above object, according to an aspect, the present invention provides a rotation-angle detecting device including a rotor, a first output mechanism for outputting a first detection signal in response to the rotation of the rotor, and a second output mechanism for outputting a second detection signal in response to the rotation of the rotor, wherein a first transmission gear and a second transmission gear having intermittent teeth are arranged along the rotation axis on an outer peripheral surface of the rotor, the first output mechanism includes a first output gear that is meshed with the first transmission gear and that rotates on an axis in parallel with the axis of the rotor, and a first output section for outputting the first detection signal in response to the rotation of the first output gear, the second output mechanism includes a second output gear that is meshed with the second transmission gear and that rotates on an axis in parallel with the axis of the rotor, and a second output section for outputting the second detection signal in response to the rotation of the second output gear, and the rotation angle of the rotor is detected as an absolute angle on the basis of the first detection signal and the second detection signal.
The above features make it possible to provide a low-profile compact rotation-angle detecting device that can measure the absolute angle with a simple configuration.
Preferably, the first detection signal has a predetermined period and continues within the rotation range of the rotor, and the second detection signal rises or falls stepwise within the rotation range of the rotor.
This allows the rotation-angle detection device to measure the absolute angle with high precision.
Preferably, the second output gear includes upper and lower tooth segments arranged vertically and alternately, the upper tooth segment is meshed with the second transmission gear, and the lower tooth segment engages with the outer peripheral surface of the rotor after the upper tooth segment is rotated by a predetermined angle in engagement with the second transmission gear, thereby preventing the second output gear from returning.
In this case, the second output gear can be prevented from returning with a simple structure, and the accuracy in detecting the rotation angle can be increased.
Preferably, each of the first output section and the second output section includes a permanent magnet with different magnetic poles opposing each other with the rotation axis therebetween, and a magnetoresistive element whose resistance varies depending on the direction of a magnetic field of the permanent magnet.
In this case, the rotation angle can be detected in a non-contact manner. Moreover, since the magnetoresistive element is used, the detection accuracy can be increased, regardless of assembly accuracy.
Preferably, the first output mechanism is a non-contact magnetic output means, and the second output mechanism is a contact output means.
In this case, since the second output mechanism is less expensive than the first output mechanism, the cost can be reduced. Moreover, since the number of revolutions of the second output mechanism is smaller than that of the first output mechanism, the second output mechanism can stand long use.
Preferably, the second output mechanism is a rotary variable resistor.
Since the second output mechanism can be thereby made even less expensive, the rotation-angle detecting device can be provided at a lower price.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with referen
Alps Electric Co. ,Ltd.
Beyer Weaver & Thomas LLP
Patidar Jay
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