Initializing drive apparatus

Details Initializing drive apparatus Initializing drive apparatus

2002-11-18

2004-09-28

Ro, Bentsu (Department: 2837)

Electricity: motive power systems

Positional servo systems

With particular motor control system responsive to the...

C116S284000

Reexamination Certificate

active

06798164

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an initializing drive apparatus, particularly to an initializing drive apparatus for resetting an out-of-phase state of a stepping motor.
Conventionally, as a vehicular indicating apparatus using a stepping motor, an indicator instrument as shown by
FIG. 1
is known. In the drawing, the indicator instrument includes a stepping motor
1
, an indicator
2
moved in cooperation with rotation of the stepping motor
1
and a drive apparatus
4
for the stepping motor which regularly and reversely rotates the stepping motor
1
. The above-described stepping motor
1
includes two excitation coils
1
a
1
and
1
a
2
, a rotor
1
b
in which N and S poles are alternately magnetized by respective three poles and rotated in response to changes in excited states of the excitation coils
1
a
1
and
1
a
2
and gears id for transmitting drive force of the rotor
1
b
to the indicator
2
.
The stepping motor
1
includes a piece
1
e
as a driven member provided on a rear side of the gear
1
d
on which the indicator
2
is provided and which is moved in cooperation with rotational movement of the rotor
1
b
, and a stopper
1
f
for mechanically stopping rotation of the rotor
1
b
by being brought into contact with the piece
1
e
which is provided at a containing case, not illustrated, the containing case contains the excitation coils
1
a
1
and
1
a
2
, the rotor
1
b
, the gears
1
d
and the piece
1
e.
Rotation of the stepping motor
1
to direct the piece
1
e
to the stopper
1
f
is defined as reverse rotation. A rotational direction of the indicator
2
rotating reversely is defined as a reverse rotational direction Y
4
. In contrast thereto, rotation of the stepping motor
1
to separate the piece
1
e
from the stopper
1
f
is defined as regular rotation. A rotational direction of the indicator
2
rotating regularly is defined as regular rotational direction Y
3
. The stopper
1
f
is provided to indicate a graduation of, for example, 0 km/h on a dial when the stopper
1
f
is brought into contact with the piece
1
e.
Here, an explanation will be given of the principle of operating to rotate the stepping motor
1
in reference to
FIG. 7
showing an example of a relationship between excited states of the excitation coils
1
a
1
and
1
a
2
and rotation of the rotor
1
b
as follows. First, when the stepping motor
1
is controlled to bring about an excited state determined in excitation step (1), that is, such that a side of the excitation coil
1
a
1
becomes S pole and b side of the excitation coil
1
a
2
becomes nonexcited, N pole of the rotor
1
b
is attracted to the a side of the excitation coil
1
a
1
and stabilized.
Next, when the operation proceeds to excitation step (2) and the stepping motor
1
is controlled such that the a side of the excitation coil
1
a
1
becomes S pole and the b side of the excitation coil
1
a
2
becomes S pole and magnetic forces of the two excitation coils
1
a
1
and
1
a
2
become equal to each other, the rotor
1
b
is stopped at a position rotated from a position of the rotor
1
b
of excitation step (1) by 15 degrees in an arrow mark Y
2
direction. In accordance with rotation of the rotor
1
b
in the arrow mark Y
2
direction, the indicator
2
is rotated in the arrow mark Y
4
direction (refer to FIG.
1
).
In the following, when the stepping motor
1
is controlled such that the a side of the excitation coil
1
a
1
and the b side of the excitation coil
1
a
2
respectively become nonexcited, S pole (excitation step (3))→N pole, S pole (excitation step (4))→N pole, nonexcited (excitation step (5))→N pole, N pole (excitation step (6))→nonexcited, N pole (excitation step (7))→S pole, N pole (excitation step (8)), the rotor
1
b
is rotated by respective 15 degrees in the arrow mark Y
2
direction by following the change in the excited state. Further, in the excitation steps (2), (4), (6) and (8) in which both of the exciting coils
1
a
1
and
1
a
2
are magnetized, the stepping motor
1
is controlled such that the magnetic forces of the two excitation coils
1
a
1
and
1
a
2
become equal to each other.
When the stepping motor
1
is controlled to the excited state prescribed at excitation step (1) again from the excitation step (8), the rotor
1
b
is rotated by 15 degrees further in the arrow mark Y
2
direction and stabilized. Therefore, by controlling the excited states of the excitation coils
1
a
1
and
1
a
2
by repeating a plurality of excitation steps (1) through (8) which differ from each other in accordance with a regular excitation pattern constituted by aligning excitation steps in a previously determined order (1)→(2) . . . →(8), the rotor
1
b
is rotated by respective 15 degrees in the arrow mark Y
2
direction at respective steps. Hereinafter, notation of the rotor
1
b
in the arrow mark Y
2
direction is referred to as reverse rotation.
In order to rotate the rotor
1
b
in the arrow mark Y
1
direction, the excited states of the excitation coils
1
a
1
and
1
a
2
may be controlled in accordance with a reverse excitation pattern in which excitation steps constituting the regular excitation pattern are aligned in a reverse order such as excitation steps (8)→(7)→ . . . →(1). In accordance with rotation of the rotor
1
b
in the arrow mark Y
1
direction, the indicator
2
is moved in the arrow mark Y
3
direction (refer to FIG.
1
). Hereinafter, rotation of the rotor
1
b
in the arrow mark Y
1
direction is referred to as regular rotation.
Further, in order to change the excited states of the excitation coils
1
a
1
and
1
a
2
such as excitation steps (8)→. . . →(1), the drive apparatus
4
respectively inputs excitation pulses as shown by
FIG. 8
to the a and b sides of the excitation coils
1
a
1
and
1
a
2
.
Next, an explanation will be given of operation when the indicating apparatus is used in, for example, a vehicle speed meter as follows. The drive apparatus
4
is supplied with angle data D
1
indicating a rotational angle of the rotor
1
b
in correspondence with a moving amount &thgr;-&thgr;′ which is a difference between a target position &thgr; which is an indicating position of the indicator
2
calculated based on vehicle speed information measured by a vehicle speed meter and a current position &thgr;′. By controlling the excited states of the excitation coils
1
a
1
and
1
a
2
in accordance with the angle data D
1
by the drive apparatus
4
, the indicator
2
is moved by the moving amount &thgr;-&thgr;′ and indicates the target position &thgr;.
Meanwhile, there is a case in which the indicating apparatus becomes out of phase in which the moving amount &thgr;-&thgr;′ of the indicator
2
to be moved inherently and an actual moving amount differ from each other owing to input of the angle data D
1
superposed with vibration or noise of the vehicle. Further, when the out-of-phase is repeated, there is brought about a difference between the speed indicated by the indicator
2
and the speed information measured by the speed sensor and the indicating apparatus cannot indicate accurately.
Hence, in order to resolve such a problem, the drive apparatus
4
is made to carry out initializing operation, mentioned later. In the initializing operation, the drive apparatus
4
rotates the stepping motor
1
reversely such that the piece
1
e
is directed to move to the side of the stopper
1
f
at each time of making an ignition switch ON. When the piece
1
e
is brought into contact with the stopper
1
f
and the indicator
2
is mechanically stopped at a contact position which is at graduation of 0 km/h on the dial, the drive apparatus
4
holds the excitation coils
1
a
1
and
1
a
2
in a previously determined initial excited state and electrically stops rotation of the stepping motor
1
. By carrying out the above-described initializing operation, there is carried out resetting operation for resetting the difference between the speed indicated

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