# US 7,612,477 B2 · Electromagnetic brake device for small-sized motor

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- Number: US 7,612,477 B2
- Document ID: US7612477B2
- Status: Granted
- Kind: B2
- Application number: 11/910,267
- Filed: 2005-04-22
- Published: 2008-08-14
- Granted: 2009-11-03
- Earliest claimed: 2005-04-22
- Assignees: Harmonic Drive Systems Inc.
- Inventors: Toshiyuki Abe; Kiyoto Kobayashi
- Web page: https://patentgrep.com/patent/US7612477B2

## CPC

- F16D 55/02: with axially-movable discs or pads pressed against axially-located rotating members
- F16D 2121/14: Mechanical
- F16D 2121/22: for releasing a normally applied brake
- F16D: COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES

## Abstract

An electromagnetic brake device (3) is assembled to a rear end section of a small-sized motor (1). The electromagnetic brake device (3) has a rotating disc (11) fixed to a motor rotation shaft (4), a sliding disc (12) slidable in an axial direction, a coil spring (13) pressing the sliding disc (12) to the rotating disc (11), and an electromagnet (14) capable of attracting the sliding disc (12) against spring force. A circular recess (16e) is formed in the center of a rear end surface of a yoke (16) of the electromagnet (14). In a state where the electromagnetic brake device (3) is assembled, a bearing (6) supporting a rear end shaft section (4b) of the motor rotation shaft is received in the circular recess (16e). As a consequence, no large circular dead space is produced at a portion on the outer periphery side of the bearing (6), which portion is between a motor end plate (5) and a rear end surface of the electromagnetic brake device (3). As a result, the length of the shaft of the small-sized motor (1) is suppressed from increasing.

## Claims

### Claim 1

An electromagnetic brake built-in type small-sized motor comprising:
an electromagnetic brake device for locking rotation of a motor rotation shaft; wherein
the electromagnetic brake device is assembled between a motor main section and a motor end plate, and a shaft end part of a rear end extension part of the motor rotation shaft is rotatably supported by the motor end plate via a bearing;
the electromagnetic brake device comprises:
a rotating disc fixed to the motor rotation shaft so as to rotate together with the motor rotation shaft;
a sliding disc that is slidable along an axial line of the motor rotation shaft so as to come close to and move away from the rotating disc;
a spring member that presses the sliding disc against the rotating disc; and
an electromagnet that is able to pull the sliding disc in a direction for moving away from the rotating disc while being against a spring force of the spring member; wherein
the electromagnet includes a yoke and an exciting coil;
the yoke includes an outer cylindrical part and an inner cylindrical part, both of which are formed so as to be concentric each other, and a circular end plate part that blockades a rear end of a circular space formed between the outer cylindrical part and the inner cylindrical part;
the exciting coil is installed in the circular space;
a circular recess with a specified depth is formed in the circular end plate part of the yoke by having an inner circumference side of the circular end plate part bend forward in a step form in a sectional shape cut along the axial line; and
the electromagnetic brake device is assembled to the rear end extension part of the motor rotation shaft in such a manner that a part of the bearing is housed in the circular recess of the electromagnetic brake device.

### Claim 2 (depends on 1)

The electromagnetic brake built-in type small-sized motor according to claim 1, wherein an inner end surface of the bearing facing the electromagnetic brake device is covered with a dust stringer.