Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
2000-12-07
2002-09-24
Strecker, Gerard R. (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207200, C702S001000
Reexamination Certificate
active
06456065
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotational angle detecting device, and, more particularly, to a rotational angle detecting device which is connected to a rotary member, such as a steering shaft of an automobile, and which outputs two or more detection signals which are in correspondence with the rotational angle and the rotational direction of the steering wheel in order to detect the rotational angle of the rotary member using these detection signals.
2. Description of the Related Art
Hitherto, a rotary sensor has been used to form a rotation detecting section. As an example of such a rotary sensor, the following rotary sensor will be described. (This rotary sensor will hereinafter be referred to as “conventional rotary sensor.”)
The conventional rotary sensor comprises a fixed base member, a rotor which can rotate with respect to the base member, and a rotation detecting section disposed between the base member and the rotor. The rotation detecting section outputs a sinusoidal first detection signal, a sinusoidal second detection signal, and a third detection signal. The first and second detection signals have constant amplitudes and the same periods, and are out of phase by ¼ wavelength. The third detection signal has the same period in the entire rotational range of the rotor and increases linearly. When the rotary sensor is used, the rotor is connected to a rotary member such as a steering shaft of an automobile. Here, the rotation detecting section comprises first and second magnets, and first to third Hall elements. The first and second magnets are disposed at the base member. The first and second Hall elements are disposed at the rotor so as to oppose the first magnet at an angle of substantially 90 degrees. The third Hall element is disposed so as to oppose the second magnet.
In this structure, when the steering wheel is rotated in order to rotate the steering shaft connected to the steering wheel, the rotor connected to the steering shaft rotates, causing the rotation detecting section to generate the first to third detection signals which are in correspondence with the rotational angle and the rotational direction of the steering shaft.
The generated first to third detection signals are supplied to a controlling section installed in the automobile. Based on the supplied third detection signal, the controlling section detects the rotational direction and the rough rotational angle from the neutral position of the steering wheel (or the steering shaft). Similarly, based on the supplied first and second detection signals, the controlling section detects the very small rotational angle from the neutral position of the steering wheel (or the steering shaft). The detected rotational direction and rotational angles from the neutral position of the steering wheel (or the steering shaft) are supplied to a controller as detection information. Based on the supplied detection information, the controller carefully controls the traction and the suspension of the automobile.
FIG. 7
is a graph showing the relationship between the angle of rotation of the steering wheel and the output voltage of each of the first, second, and third detection signals.
In
FIG. 7.
, reference numeral
71
denotes the first detection signal, reference numeral
72
denotes the second detection signal, and reference numeral
73
denotes the third detection signal.
FIG. 7
shows the variations in the output voltages of the first to third detection signals
71
to
73
with respect to a rotational angle of zero degrees (that is, the neutral position) of the steering wheel, within a rotational angle range of from 0° to +225°.
Here, the first detection signal
71
and the second detection signal
72
are sinusoidal, have the same amplitudes and periods, and are out of phase by ¼ wavelength. For both of these signals
71
and
72
, the voltages are 4.5 V at maximum amplitude, and 0.5 V at minimum amplitude. For the first detection signal
71
, when the rotational angles are +67.5° and +157.5°, the amplitude thereof is a minimum (voltage=0.5 V). For the second detection signal
72
, when the rotational angles are 0°, +90.0°, and +180.0°, the amplitude thereof is a minimum (voltage=0.5 V). The third detection signal increases linearly from a rotational angle of 0° to +225°, and has a voltage of 2.5 V when the rotational angle is 0° and a voltage of 3.0 V when the rotational angle is +180°.
Hereunder, using the graph of
FIG. 7
, the detection of the rotational direction and rotational angle of the steering wheel carried out at the controlling section will be described.
First, when the controlling section is to detect the rotational direction of the steering wheel from the neutral position (which corresponds to an angle of rotation of 0°) of the steering wheel, it detects the rotational direction by the voltage value of the supplied third detection signal
73
which has been supplied. More specifically, when the voltage value of the third detection signal
73
is more than 2.5 V, the controlling section detects that the rotational direction of the steering wheel corresponds to one direction (that is, the positive rotational angle direction). On the other hand, when the voltage value of the third detection signal
73
is less than 2.5 V, the controlling section detects that the rotational direction of the steering wheel corresponds to the other direction (that is, the negative rotational angle direction).
Then, as shown in
FIG. 7
, the controlling section divides the entire rotational angle range of the steering wheel, such as a rotational angle range of 1440° (±720°), into angle (such as 90°) divisions which correspond to one wavelength of each of the first detection signal
71
and the second detection signal
72
. These divisions are represented as . . . , N−1, N, N−2, . . . Then, based on the voltage value of the supplied third detection signal
73
, the controlling section detects a rough rotational angle which indicates to which angle division the rotational angle of the steering wheel corresponds. For example, if the controlling section detects that the voltage value of the third detection signal
73
is 2.8 V, the angle division N is detected as the angle division corresponding to this voltage value.
Thereafter, the controlling section determines a first voltage value V
1
and a second voltage value V
2
when the voltage values of the supplied first and second detection signals
71
and
72
are the same in the detected angle division N. Using the obtained first and second voltage values V
1
and V
2
, one detection signal which has a voltage value outside the voltage range of the first and second voltage values V
1
and V
2
, and the other detection signal which has a voltage value within the voltage range of the first and second voltage values V
1
and V
2
are determined.
After the determination, the controlling section determines whether the other detection signal whose voltage value lies within the voltage range of the first and second voltage values V
1
and V
2
is the first detection signal
71
or the second detection signal
72
. At the same time, the controlling section determines whether the one detection signal whose voltage value lies outside the voltage range of the first and second voltage values V
1
and V
2
has a voltage value which is less than the first voltage value V
1
or greater than the second voltage value V
2
, and whether the other detection signal whose voltage value lies within the voltage range of the first and second voltage values V
1
and V
2
exists in any one of four division portions of the one angle division N, that is, in any one of first to fourth angle division portions H
1
to H
4
of the one angle division N. Accordingly, by finding out whether the other detection signal exists in any one of the first to fourth angle division portions H
1
to H
4
of the one angle section N, the controlling section detects the very small
Hoshi Toshiyuki
Kato Hironori
Ogawa Toshio
Okumura Hirofumi
Sanpei Yoshio
Alps Electric Co. ,Ltd.
Strecker Gerard R.
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