1. Field of the Invention
The present invention relates to an electromagnetic brake which constrains a shaft to prevent the shaft from dropping, an electric motor, and a machine.
2. Description of the Related Art
To drive moving parts of a machine, robot, etc., an electric motor with a brake is used. For example, such a brake is an electromagnetic brake which holds a rotational position of the electric motor when stopping rotation of the electric motor and the supply of power to the electric motor is stopped. In general, an electromagnetic brake includes a hub which is arranged fastened around a shaft, a brake pad which engages with the hub by spline engagement and rotates together with it, a fixed end plate which is arranged at one side of the brake pad, an armature which is arranged at the other side of the brake pad, and a coil spring which biases the armature to the end plate.
In such an electromagnetic brake, at the time of brake release, the brake pad has to be kept from being pushed against the armature and end plate. In other words, it is necessary to provide a clearance at the engagement part between the hub and brake pad and make the brake pad move in the axial direction at the time of brake release. However, when providing a clearance at the engagement part, at the time of brake operation, the shaft becomes offset by exactly the amount of the clearance of the engagement part and the shaft can drop by a slight distance.
Further, in Japanese Unexamined Utility Model Publication No. 61-206136U, an elastic member is arranged between the engagement surface of the hub and the engagement surface of the brake pad. In other words, the engagement surface of the hub and the engagement surface of the brake pad are pushed by the elastic member to eliminate the clearance of the engagement part. Due to this, noise of the two engagement surfaces striking each other at the time of rotation is prevented from occurring.
However, with just arranging an elastic member, sometimes the center axis of the hub and the center axis of the brake pad become offset from each other. For this reason, if a load acts on the shaft at the time of brake operation due to gravity, the center axis of the brake pad will move slightly trying to return to its original position. As a result, in the electromagnetic brake of the prior art, there is the problem that slight dropping of the shaft cannot be prevented.
The present invention was made in consideration of such a situation and has as its object the provision of an electromagnetic brake which prevents a shaft from dropping slightly even at the time of brake operation and of an electric motor and machine which have such an electromagnetic brake built into them.
To achieve the above-mentioned object, according to a first aspect, there is provided an electromagnetic brake comprising a hub which is arranged fastened around a shaft, a brake pad which engages with the hub by spline engagement and rotates together with it, a fixed end plate which is arranged at one side of the brake pad, an armature which is arranged at the other side of the brake pad, a biasing member which biases the armature to the end plate, and a field core which has an electromagnetic coil which magnetically attracts the armature against the biasing force of the biasing member, the electromagnetic brake further comprising a plurality of elastic members which are arranged between an engagement surface of the brake pad and an engagement surface of the hub symmetrically with respect to a center of rotation of the shaft and wherein biasing directions of the plurality of elastic members are made the same rotational direction.
According to a second aspect, there is provided an electric motor with an electromagnetic brake comprising a built-in electromagnetic brake of the first aspect.
According to a third aspect, there is provided a machine wherein a shaft is rotated by a dropping portion which drops due to gravity, wherein an electromagnetic brake of the first or second aspect is arranged at the shaft so that a direction of rotation of the shaft when gravity causes the dropping portion to drop and a direction in which the hub is biased by the elastic member match.
According to a fourth aspect, there is provided the first aspect wherein the elastic members are leaf springs.
These and other objects, features, and advantages of the present invention will become clearer from the detailed description of typical embodiments of the present invention which are shown in the attached drawings.
Below, embodiments of the present invention will be explained with reference to the attached drawings. In the following figures, similar members are assigned similar reference notations. To facilitate understanding, these figures are suitably changed in scale.
As shown in
Referring again to
Further, if the electromagnetic brake 10 is supplied with power, the electromagnetic coil 16 is driven and the armature 15 is attracted to the field core 18 against the biasing force of the biasing member 17. In other words, the armature 15 separates from the brake pad 13, so the brake pad 13 is released from the end plate 14 and the armature 15. In other words, the electromagnetic brake 10 is unlocked in state.
In this regard,
As can be seen from
Further,
In this regard,
As can be seen from
As can be seen with reference again to
Furthermore, in the present invention, three leaf springs 25 are arranged point symmetrically with each other about the shaft 11. For this reason, even if these leaf springs 25 push the corresponding recessed parts, the pushing forces are balanced with each other and the hub 12 and brake pad 13 will never become offset from the shaft 11. Further, in the leaf springs 25, only the bent parts 25b contact the corresponding recessed parts, so movement of the brake pad 13 in the axial direction is not obstructed either.
As opposed to this, in
At the three circles A, B, and C which are shown in
In this regard,
In such a case, the front end of the leaf spring 25 pushes against the second slanted face 12c of the projecting part 12a. Therefore, a clearance is prevented from occurring between the first slanted face 12b of the projecting part 12a and the first slanted face 13b of the recessed part 13a. For this reason, it will be understood that even in the other electromagnetic brake which is shown in
In the present invention, a plurality of elastic members are arranged between the engagement surface of the brake pad and the engagement surface of the hub symmetrically with respect to the center of rotation of the shaft so that the biasing directions are the same rotational direction. For this reason, it is possible to eliminate in advance any clearance between the engagement surface of the brake pad and the engagement surface of the hub. For this reason, even when the shaft is subjected to a load, the shaft will not become offset and the shaft can be prevented from dropping slightly at the time of brake operation.
Typical embodiments were used to explain the present invention, but a person skilled in the art would understand that the above-mentioned changes and various other changes, deletions, and additions may be made without departing from the scope of the present invention.
Number | Date | Country | Kind |
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2013-022597 | Feb 2013 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
2438381 | Banker | Mar 1948 | A |
4445596 | Waters et al. | May 1984 | A |
20040154422 | Menjak et al. | Aug 2004 | A1 |
20090203453 | Heinrich | Aug 2009 | A1 |
Number | Date | Country |
---|---|---|
19855025 | Jun 2000 | DE |
102006019453 | Oct 2007 | DE |
61206136 | Dec 1986 | JP |
61206136 | Dec 1986 | JP |
02280644 | Nov 1990 | JP |
2003222153 | Aug 2003 | JP |
2008195310 | Aug 2008 | JP |
Entry |
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Partial Translation of Japanese Publication No. 61-206136, published Dec. 26, 1986, 1 page. |
English Translation of German Publication No. 102006019453, published Oct. 25, 2007, 18 pages. |
English Translation of German Publication No. 19855025, published Jun. 21, 2000, 11 pages. |
Number | Date | Country | |
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20140216867 A1 | Aug 2014 | US |