Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
2001-02-22
2003-03-25
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
C073S118040, C318S432000, C180S415000, C701S048000, C324S207210, C342S442000
Reexamination Certificate
active
06539329
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotational angle detecting apparatus and, more particularly, to a rotational angle detecting apparatus coupled to a rotating member, such as an automotive-steering shaft, to cause two or more detection signals, which are based on the rotational angle and the rotational direction of a steering wheel, to be output so as to detect the rotational angle of the rotating member by employing the detection signals.
2. Description of the Related Art
In a conventional rotational angle detecting apparatus, a rotation detector employs a rotary sensor. As an example of the rotary sensor, the following rotary sensor will be described (this rotary sensor will be hereinafter referred to as “the conventional rotary sensor”).
The proposed rotary sensor is constructed by a fixed base member, a rotor rotatable with respect to the base member, and a rotation detector that outputs a first sinusoidal detection signal and a second sinusoidal detection signal that are disposed between the base member and the rotor, and have a predetermined amplitude, the same cycle, and a phase difference of a quarter wavelength, and a third detection signal that maintains the same cycle over the whole rotational range of the rotor, and linearly increases in voltage value. During an operation, the rotor is coupled to a rotating member, e.g., an automotive steering shaft. In this case, the rotation detector is constituted by a first magnet and a second magnet disposed on the base member, a first Hall element and a second Hall element disposed such that they oppose the first magnet and are arranged with an angle of approximately 90 degrees, and a third Hall element disposed to oppose the second magnet, the three Hall elements being provided in the rotor.
In such a construction, when the steering wheel is turned to rotate the steering shaft connected thereto, the rotor coupled to the steering shaft rotates. This causes the rotation detector to generate the first detection signal, the second detection signal, and the third detection signal based on the rotational angle and the rotational direction of the steering shaft.
The first detection signal, the second detection signal, and the third detection signal that have been generated are supplied to a control unit mounted on a car. Based on the supplied third detection signal, the control unit detects a coarse rotational angle and the rotational direction of the steering wheel or the steering shaft from a neutral position. Based on the first detection signal and the second detection signal that have been supplied, the control unit further detects the fine rotational angle of the steering wheel or the steering shaft from the neutral position. The detected rotational angle and the rotational direction of the steering wheel or the steering shaft from the neutral position are supplied as detection information to a controller. Based on the supplied detection information, the controller decides on and detailedly carries out suspension control or traction control of the car.
FIG. 7
is a characteristic chart illustrating the relationship between the rotational angle of the steering wheel and the output voltages of the first detection signal, the second detection signal, and the third detection signal.
Referring to
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. The chart illustrates the changes in the output voltages of the first through third detection signal
71
through
73
in the range of the rotational angle from 0 degrees to +225 degrees with respect to the rotational angle 0 degrees (neutral position) of the steering wheel.
In this case, the first detection signal
71
and the second detection signal
72
are composed of sine waves that share the same amplitude and the same cycle but are different in wavelength phase by a quarter. The voltage values of both the first detection signal
71
and the second detection signal
72
are 4.5 V at a maximum amplitude, and 0.5 V at a minimum amplitude. The first detection signal
71
reaches its minimum amplitude (voltage value: 0.5 V) at the rotational angles of +67.5 degrees and +157.5 degrees. The second detection signal
72
reaches its minimum amplitude (voltage value: 0.5 V) at the rotational angles of 0 degrees, +90.0 degrees, and +180.0 degrees. The voltage value of the third detection signal
73
linearly increases until the rotational angle reaches +225 degrees from zero degrees. The voltage value is 2.5 V when the rotational angle is zero degrees, and 3.0 V when the rotational angle is +180 degrees.
Referring to the characteristic chart shown in
FIG. 7
, the operation for detecting the rotational angle and the rotational direction of the steering wheel that is performed in the control unit will be described.
First, the control unit detects the direction in which the steering wheel is rotating with respect to the neutral position (rotational angle: 0 degrees) by means of the voltage value of the third detection signal
73
that has been supplied. More specifically, if the voltage value of the third detection signal
73
exceeds 2.5 V, then the control unit detects that the steering wheel is rotating in one direction, namely, the direction of a positive rotational angle. If the voltage value of the third detection signal
73
is below 2.5 V, then the control unit detects that the steering wheel is rotating in the other direction, namely, in the direction of a negative rotational angle.
Next, as shown in
FIG. 7
, the overall rotational angle of the steering wheel, e.g., 1440 degrees (±720 degrees), is divided into sections of angles (e.g. 90 degrees), each of which being equivalent to one wavelength of the first detection signal
71
and the second detection signal
72
, . . . , N−1, N, N+1, . . . , thereby making it possible to detect, based on the voltage values of the supplied third detection signal
73
, the coarse rotational angles that indicate the correspondence between the rotational angles of the steering wheel and the sections of angles. For example, if the control unit detects 2.8 V as the voltage value of the third detection signal
73
, then an angle segment N is detected as the one that corresponds to the voltage value.
Subsequently, the control unit determines a first voltage value V
1
and a second voltage value V
2
at which the voltage values of the supplied first detection signal
71
and the second detection signal
72
agree in the detected angle segment N. The control unit then employs the determined first voltage value V
1
and second voltage value V
2
to identify one detection signal lying outside the range of the first voltage value V
1
and the second voltage value V
2
and the other detection signal lying within the range of the first voltage value V
1
and the second voltage value V
2
.
The control unit then determines whether the other detection signal lying within the range of the first voltage value V
1
and the second voltage value V
2
is the first detection signal
71
or the second detection signal
72
. At the same time, the control unit determines whether the one detection signal lying outside the range of the first voltage value V
1
and the second voltage value V
2
is smaller than the first voltage value V
1
or larger than the second voltage value V
2
. The control unit further determines whether the other detection signal lying within the range of the first voltage V
1
and the second voltage value V
2
lies in a first divided angle segment H
1
, a second divided angle segment H
2
, a third divided angle segment H
3
, or a fourth divided angle segment H
4
(angle segments H
1
through H
4
are formed by dividing the single angle section N into four segments). Thus, the fine rotational angle of the steering wheel is detected by determining in which of the divided angle segments H
1
through H
4
in the
Hoshi Toshiyuki
Kato Hironori
Ogawa Toshio
Okumura Hirofumi
Sanpei Yoshio
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Le John
LandOfFree
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