Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
2002-07-23
2004-08-17
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
C702S163000, C324S207200, C324S207250, C701S041000, C180S422000
Reexamination Certificate
active
06778939
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotational angle detector, and particularly to a rotational angle detector which prevents a controlled system from being improperly controlled by promptly identifying an abnormality of a detected angle detection signal or by promptly outputting an angle set signal with an abnormality signal added, when the rotational state of a rotor such as the steering shaft of a vehicle is detected as an angle detection signal, an angle set signal is generated based on the result of the detection and the controlled system is controlled using the angle set signal.
2. Description of the Related Art
Generally a rotational angle detector is designed to detect the rotational angle of a rotor to control a controlled system according to the result of the detection. It comprises at least the following: a rotational angle detecting section which detects the rotational state of the rotor, generates an angle detection signal and sends the angle detection signal to a control section; a control section which generates an angle set signal by performing calculation on the received angle detection signal in a prescribed manner and sends the angle set signal to a bus line; and a controller which receives the angle set signal sent through the bus line and controls the controlled system in response to the received angle set signal.
When this rotational angle detector is to be used to detect the rotational angle of the steering shaft of a vehicle, the detector is mounted in the vehicle with its rotational angle detection section connected to the steering shaft of the vehicle.
Various types of rotary sensors are available for use in the rotational angle detecting section of a rotational angle detector mounted in a vehicle. One such rotary sensor will be described next.
FIG.
10
A and
FIG. 10B
are sectional views showing an example of the structure of one of the above-said rotary sensors;
FIG. 10A
is a transverse sectional view and
FIG. 10B
is a sectional view taken along the line
10
B—
10
B of FIG.
10
A.
As illustrated in FIG.
10
A and
FIG. 10B
, this rotary sensor comprises: a case
71
, a rotor
72
, a rotary shaft
73
, a bearing
74
, a worm gear
75
, a slider
76
, a first magnet
77
1
, a second magnet
77
2
, a first Hall element
78
1
, a second Hall element
78
2
, a third Hall element
78
3
, and a circuit board
79
. In this case, the rotor
72
is connected with the steering shaft of the vehicle at its center and there are many gear teeth on its circumference. The rotary shaft
73
, around which the worm gear
75
is fitted, rotates in conjunction with the worm gear
75
. The screw grooves in the outer surface of the rotary shaft
73
engage with the screw grooves in the inner surface of the slider
76
so that the slider
76
slides in the axial direction of the rotary shaft
73
as the rotary shaft
73
turns. When the worm gear
75
and the gear teeth of the rotor
72
engage with each other and the rotor
72
turns, the rotary shaft
73
also turns by the mediation of the worm gear
75
at a prescribed rotation ratio with respect to the rotor
72
. The worm gear
75
has a cylindrical magnet holder
75
A at one end of it and the cylindrical first magnet
77
1
is fitted on the circumference of the magnet holder
75
A. The slider
76
has a planar second magnet
77
2
attached on its outer surface. Attached on the circuit board
79
, which is arranged in parallel to the rotary shaft
73
, are the first Hall element
78
1
, the second Hall element
78
2
and the third Hall element
78
3
. The first Hall element
78
1
and the second Hall element
78
2
are located adjacent to the outer surface of the first magnet
77
1
, forming an angle of approximately 90 degrees with respect to the central axis of the first magnet
77
1
. The third Hall element
78
3
is located adjacent to the outer surface of the second magnet
77
2
.
As the rotor
72
turns, a sinusoidal waveform first angle detection signal and a sinusoidal waveform second angle detection signal are issued with a quarter-wave phase difference from the first Hall element
78
1
and the second Hall element
78
2
respectively, with a constant maximum amplitude and the same cycle. At the same time, the third Hall element
78
3
issues a third angle detection signal which increases linearly with the full rotation range of the rotor
72
constituting one cycle.
The first angle detection signal, second angle detection signal and third angle detection signal from the rotary sensor are sent to the control section. The control section roughly determines the rotational angle and direction with respect to the neutral position of the steering wheel (steering shaft) according to the received third angle detection signal and finely determines the rotation angle with respect to the neutral position of the steering wheel according to the received first and second angle detection signals. The control section generates an angle set signal based on the result of detection of the rotational angle and direction with respect to the neutral position of the steering wheel, and sends the generated angle set signal through the bus line to the controller. According to the angle set signal it has received, the controller accurately controls a controlled system such as the suspension system or traction control system of the vehicle.
FIG. 8
is a characteristic graph showing the relation between the steering wheel rotational angle and the voltage of each of the first to third angle detection signals, which are all sent from the rotary sensor, in a rotational angle detector based on the above-said rotary sensor.
In
FIG. 8
, reference numeral
51
represents the first angle detection signal,
52
the second angle detection signal and
53
the third angle detection signal; this graph shows changes in the voltage of each of the first to third angle detection signals
51
,
52
,
53
in the whole range of steering wheel rotation (±720 degrees from the neutral position).
Here, the first angle detection signal
51
and the second angle detection signal
52
are sinusoidal waveform signals with the same maximum amplitude and the same cycle, between which there is a quarter-wave phase difference, where they both have a maximum voltage of 4.5 V and a minimum voltage of 0.5 V. For the first angle detection signal
51
, the voltage is the minimum (0.5 V) at a rotational angle of −22.5 degrees from the neutral position (0 degree) and rotational angles decreasing from −22.5 degrees in decrements of −90 degrees, and at a rotational angle of +67.5 degrees and rotational angles from +67.5 degrees in increments of +90 degrees. For the second angle detection signal
52
, the voltage is the minimum (0.5 V) at a rotational angle of 0 degree (neutral position) and rotational angles decreasing from 0 degree in decrements of −90 degrees and rotational angles increasing from 0 degree in increments of +90 degrees. For the third angle detection signal
53
, the voltage linearly increases over the rotational angle range from −720 degrees to +720 degrees, with the minimum voltage (0.5 V) at −720 degrees of rotational angle and the maximum voltage (4.5 V) at +720 degrees of rotational angle.
FIG. 9
is a fragmentary view of the characteristic graph in
FIG. 8
where the part ranging from −90 degrees to +90 degrees is enlarged.
In
FIG. 9
,
51
U represents a virtually linear leading edge (gradient) for the first angle detection signal
51
,
51
D a virtually linear trailing edge (gradient) for the first angle detection signal
51
,
52
U a virtually linear leading edge (gradient) for the second angle detection signal
52
, and
52
D a virtually linear trailing edge (gradient) for the second angle detection signal
52
. The same other elements as those shown in
FIG. 8
are designated with the same reference numerals.
Next, how the rotational direction and angle of the steering wheel are detected by the control sectio
Kato Hironori
Sanpei Yoshio
Alps Electric Co. ,Ltd.
Barlow John
Vo Hien
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