Construction of a motor with a built-in sensor

Details Construction of a motor with a built-in sensor Construction of a motor with a built-in sensor

1999-06-29

2001-05-01

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S06800R, C310S089000, C310S090000

Reexamination Certificate

active

06225715

ABSTRACT:

FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a construction of a motor which a sensor for detecting position or speed thereof is built in. More particularly, it relates to a construction of a hybrid type stepping motor, a VR type stepping motor, and a DC brushless motor, for example, which the aforesaid sensor is built in, or a motor in which a sensor is made function as a resolver.
As a construction of a motor with a built-in sensor of this type relating to the present invention, regarding a motor which a sensor such as a variable magnetic resistance resolver is built in, there is disclosed a motor in which a motor portion and a sensor portion for detecting position or speed of the motor are arranged in line in the axial direction, and are contained in one housing with their rotating shafts are made in common (Japanese Patent Provisional Publication No. 1-164298(No. 164298/1989): same as U.S. Patent application No. 096522 filed on Sep. 15, 1987).
When a sensor for detecting position and speed, such as a general encoder or resolver, is built in a motor, a motor construction as shown in
FIG. 2
has been used.
In
FIG. 2
, a motor
101
is made up of a stator
102
and a rotor
103
rotatably disposed on the axis of the stator
102
. The stator
102
has windings
105
wound on a stator core
104
to form a rotating magnetic field. The rotor
103
, consisting of a rotor core
106
and a rotor shaft
107
, is rotatably supported on frames
109
,
109
via bearings
108
,
108
.
General methods for detecting the position of motor rotor includes a method, being used for a DC motor etc., in which a magnetic flux of a permanent magnet fixed to the rotor is detected by a magnetic sensor such as a Hall effect element, and a method, being seen in a servomotor etc., in which a position sensor
110
such as an optical encoder etc. is disposed on the opposite side of the output shaft side of the motor (for example, Japanese Patent Provisional Publication No. 8-168210 (No. 168210/1996).
However, a construction of such a conventional motor, for example, a construction of a motor which a sensor such as a variable magnetic resistance type resolver or an optical encoder is built in has a problem in that the size of the whole motor is lengthened because the size of the aforesaid encoder portion serving as a sensor is added.
In this case, if an attempt is made to keep the total length of motor the same size as that of the conventional motor, the total length of the rotor is inevitably shortened, which causes the output to decrease as compared with the motor of the same size.
On the other hand, for the motor disclosed in aforesaid Japanese Patent Provisional Publication No. 1-164298(No. 164298/1989), the motor portion and the sensor portion have the same outside diameter, so that this motor has an advantage of the common use of iron plate for forming the core. However, the sensor portion is subject to the effect of magnetic flux generated on the motor portion, so that some degree of distance is needed between the motor portion and the sensor portion. Therefore, this motor has a problem in that the total length of motor is increased.
OBJECT AND SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems, and accordingly an object thereof is to provide a construction of a motor with a built-in sensor, in which the total length of the motor is not increased, and can be made approximately equal to the total length of the conventional motor which has no built-in sensor.
To achieve the above object, in a motor comprising a rotor having a rotor core and a stator in which windings are wound on a stator core to form a rotational magnetic field,
(1) A substantially cylindrical recess with a diameter smaller than the outside diameter of the rotor is formed at the end face portion of the rotor core, and in a space which communicates with the recess, including the recess, and reaches the windings end face of the stator, a part of a motor frame to which a bearing for rotatably supporting a rotor shaft while passing through it is fitted and a sensor, on the outside of the bearing, for detecting the position or speed of the motor are disposed.
(2) In item (1), the sensor consists of a fixed portion and a movable portion, the fixed portion and the bearing are disposed on one frame of the motor, and the movable portion is fixed to the rotor shaft so as to operate in cooperation with the fixed portion.
(3) In items (1) and (2), a step portion having an outer peripheral surface parallel and concentric with the axis of the bearing is formed on the inside of motor frames disposed at both ends of the stator core, and the rotor is positioned by fitting the motor frames to the inner peripheral surface of the stator core via the each step portion.
In the construction of a motor with a built-in sensor configured as described above, the inside of the rotor core, which faces the end portion and does not contribute to the development of torque of the motor, is cut out, and a part of the motor frame to which the bearing for the rotor shaft is fitted is disposed in this cut-out recess, and also the sensor is disposed in the space reaching the winding end face of stator on the outside of the bearing. By housing the bearing and the sensor in the recess and the space, the motor construction is made thin.
According to the construction of the present invention, the total length of the motor is not increased, and can be made approximately equal to the total length of the conventional motor which has no built-in sensor. Therefore, the motor portion can be made thin, and at the same time, the output and characteristics that the motor inherently has are not decreased as compared with the motor of the same size.
Thereupon, the total length of the motor can be shortened as compared with the conventional motor for controlling position or speed. Also, since the inertia of the rotor can be decreased, the acceleration and deceleration characteristics of the motor can be increased.
Further, the gap portion between the fixed portion and the movable portion of sensor, which detects the magnetic resistance, separates from the gap between the stator and the rotor of the motor, where the magnetic flux density is high, toward the inner periphery where the magnetic flux density is low, so that the distance between the rotor of the motor and the sensor can be decreased.
At the same time, since the bearing is interposed between the rotor of the motor and the sensor, a certain shield effect can be anticipated.
Further, since the fixed portion of the sensor is assembled to the motor frame, the construction of the motor is simple, which permits easy assembly. At the same time, since the motor frame is assembled while being fitted on the inner peripheral surface of the stator core, the rotor can be positioned easily.


REFERENCES:
patent: 3790832 (1974-02-01), Patel
patent: 3873861 (1975-03-01), Halm
patent: 4110676 (1978-08-01), Edick et al.
patent: 4429242 (1984-01-01), Layh
patent: 4772815 (1988-09-01), Harned et al.
patent: 4910790 (1990-03-01), Kershaw
patent: 4952830 (1990-08-01), Sirakawa
patent: 4955128 (1990-09-01), Sogabe et al.
patent: 5369322 (1994-11-01), Maruyama et al.
patent: 5434463 (1995-07-01), Horski
patent: 5614775 (1997-03-01), Horski et al.
patent: 5617241 (1997-04-01), Kitazawa
patent: 5780946 (1998-07-01), Nakamura et al.
patent: 5786646 (1998-07-01), Newberg et al.
patent: 5864182 (1999-01-01), Nagate et al.
patent: 5955807 (1999-09-01), Kajiura et al.
patent: 5977671 (1999-11-01), Kim
patent: 8-168210 (1996-06-01), None
Merriam Webster's Collegiate Dictionary, tenth edition, p. 150, 1997.

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