Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-09-14
2002-07-23
Ponomarenko, Nicholas (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06800R, C310SDIG006, C310S089000
Reexamination Certificate
active
06424061
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a stepping motor with a magnetic sensor—this stepping motor is widely used in information devices and the like—and more particularly, it relates to a mounting mechanism of the sensor.
BACKGROUND OF THE INVENTION
Recently, stepping motors are extensively used in various fields, such as information devices and audio equipment including, a printer, facsimile, image scanner, copying machine, laser beam printer, CD-ROM, DVC. Other fields including factory automation (FA) equipment such as machine tools, automotive components, and a field of home appliances also employs a large number of stepping motors. This extensive use of the stepper motors is mainly thanks to a low cost, and simple operation realizing a speed control or a positioning control.
Nowadays, a stepping motor coming with a sensor is widely available in order to improve the performance thereof.
A sensor mounting mechanism to the stepping motor is disclosed by the Japanese Patent Application Non-Examined Publication No. H09-253139 and Japanese Utility Model Application Non-Examined Publication No. S62-135558.
FIG.
10
and
FIG. 11
illustrate the construction of conventional stepping motors coming with a sensor.
FIG. 10
is a cross section illustrating a structure of a conventional stepping motor with a magnetic sensor.
In
FIG. 10
, driving coil
51
of the stepping motor is covered by yoke
52
, which is a comb-teeth-like pair of magnetic substance. Rotor
53
is disposed to face the inner wall of yoke
52
with a given space. Rotor
53
comprises output shaft
54
, magnet
55
which is magnetized to N and S polarities in pairs, and a resin-made coupler for coupling shaft
54
with magnet
55
. Magnetic sensor
56
is soldered to printed circuit board
57
attached independently to the stepping motor. With a given space, sensor
56
faces to a face-to-face type magnetic drum
58
mounted to shaft
54
and having pairs of polarities. The revolving of rotor
53
rotates drum
58
. At this time, a voltage corresponding to the magnetic force of the pairs of N and S polarities of drum
58
is tapped off from sensor
56
through a circuit printed on board
57
. Sensor
56
and drum
58
are, in general, protected by sensor cover
59
mechanically as well as electrically.
FIG. 11
is a cross section illustrating a structure of a conventional stepping motor with a photo sensor.
In
FIG. 11
, slit-disc
73
having a plurality of fine slits is disposed on output shaft
72
of rotor
71
. Photo sensor
74
either one of transparent or reflective type detects the slits on disc
73
, and outputs signals corresponding to the sensed result cyclically. Sensor
74
and disc
73
are, in general, protected by sensor cover
75
electrically and mechanically.
This sensor is generally called optical encoder, and used in various fields. The sensor features (a) easy mounting, (b) a large output signal, and (c) versatile output signals available depending on a slit-type on the slit-disc. However, it is difficult to adjust positioning between the slit-disc and rotor for obtaining an output signal from the sensor corresponding to the rotor. The sensor thus tends to produce dispersion in performance, and the optical encoder is generally expensive.
As such, the conventional sensor has both advantages and disadvantages in mounting thereof, a magnitude of an output, position adjustment, a resolution and a cost.
Both in FIG.
10
and
FIG. 11
, functions of sensing rotation of the output shaft are the same; however, in
FIG. 10
, a magnetic sensor may directly detects a polarity position of the magnet fixed to the rotor. Since the magnetic drum uses magnets, the magnet polarities of magnetic drum and those of rotor can be aligned depending on a way of magnetizing.
On the other hand, in
FIG. 11
, the slit-disc and the magnet polarities should be aligned at an independent process. Adjustable range of dimensions (or angle) decreases at a higher sensing resolution of the slit-disc, therefore, this alignment is substantially difficult, and adversely affects the cost and stableness in performance.
A problem common to these two instances is great influence of heat to the sensor because the stepping motor generates large amount of heat by itself. When a motor is controlled, a sensor signal should be stable, and influence by heat to the circuits around and a control IC should be also considered. In a conventional structure, only the sensor has been placed at a remote spot from the motor; however, this is not enough for the heat problem. When a sensing function and controlling function of the sensor are to be attached to a stepping motor or other motors generating great amount of heat by themselves, the sensor block should be positively kept away from the motor in order to avoid the heat influence to the sensor and the controlling IC. This structure needs compactness and efficiency in assembling as well.
In the conventional stepping motor having a general-use sensor as discussed above, it is difficult to keep a given space between the magnet and sensor and decrease heat influence to the sensor as well as to the control IC.
SUMMARY OF THE INVENTION
The present invention addresses the problems discussed above and aims to provide a new mounting mechanism of a sensor for improving a positioning accuracy of the sensor mounting position as well as decreasing influence by heat generated by a stepping motor to the sensor and a controller.
The stepping motor of the present invention comprises the following elements:
(a) a rotor driven by exciting a driving coil;
(b) a position detector including a magnetic flux generator for outputting a signal in the same phase as a polarity position of a magnet mounted to the rotor and a magnetic sensor receiving magnetic force from the magnetic flux generator;
(c) a controller for controlling a stepping motor responsive to a position detection signal from the position detector;
(d) a board on which the magnetic sensor and the controller are mounted; and
(e) a sensor cover for positioning the magnetic sensor, dissipating heat from the controller and covering at least parts of the position detector as well as the controller.
The stepping motor can be divided into two independent sub-assemblies, i.e. a motor sub-assembly including the driving coil, rotor, magnetic flux generator, and a sensor sub-assembly including the board and sensor cover.
This structure decreases degradation such as lowering an output to the sensor or the controller due to the heat generated by the stepping motor, and allows an assembly process to be divided into the sensor sub-assembly and the motor sub-assembly. As a result, the present invention contributes to improving the productivity as well as lowering material loss.
REFERENCES:
patent: 3809935 (1974-05-01), Kristen et al.
patent: 4988905 (1991-01-01), Tolmie, Jr.
patent: 5049769 (1991-09-01), Reinhardt et al.
patent: 5770900 (1998-06-01), Sato et al.
patent: 5932942 (1999-08-01), Patyk et al.
patent: 5969445 (1999-10-01), Horiuchi et al.
patent: 62-135558 (1987-08-01), None
patent: 09253139 (1997-09-01), None
Fukuda Yoshiaki
Kamogi Yutaka
Nakamura Yukio
Dinh Le Dang
Matsushita Electric - Industrial Co., Ltd.
Ponomarenko Nicholas
Ratner & Prestia
LandOfFree
Stepping motor with magnetic sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stepping motor with magnetic sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stepping motor with magnetic sensor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2908283