Reduction gears-integrated actuator

Details Reduction gears-integrated actuator Reduction gears-integrated actuator

2002-04-05

2004-03-09

Ho, Ha (Department: 3681)

Machine element or mechanism

Gearing

Reexamination Certificate

active

06701803

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an inexpensive reduction gears-integrated actuator that is capable of shortening the length of the entire actuator in its axial direction and increasing a drive torque without running counter to downsizing and lightening of its weight.
(2) Description of the Related Art
Conventionally, an actuator used for a robot, a machine tool, etc., in which harmonic reduction gears and an electric motor are integrated together is constructed as shown in FIG.
3
.
FIG. 3
is a side sectional view of a prior art reduction gears-integrated actuator.
In the drawing,
30
denotes an actuator,
31
a
denotes a load side bracket,
31
b,
31
c
and
31
d
denote actuator frames,
31
e
denotes an anti-load side bracket,
32
denotes an output shaft,
33
denotes a rotation shaft,
34
denotes an electric motor,
35
denotes astator,
36
denotes a stator core,
37
denotes an armature winding,
38
denotes a rotor,
39
denotes a yoke,
40
denotes a permanent magnet,
41
denotes harmonic reduction gears,
42
denotes a circular spline,
43
denotes a flexible spline,
44
denotes a wave generator,
45
,
46
,
47
48
, and
49
denote bearings,
50
and
51
denote elastic members,
52
denotes a rotation position detector,
53
denotes a rotation disk,
54
denotes a fixed slit,
55
denotes alight emitting element,
56
denotes a light receiving element, and L
0
indicates a length of the actuator
30
in its axial direction.
Such a reduction gears-integrated actuator
30
has a structure in which the harmonic reduction gears
41
, electric motor
34
, and rotation position detector
52
are coupled to each other in a series in the axial direction in order from the load side to the anti-load side. Also, these devices are fixed inside hollow cylindrical actuator frames
31
b,
31
c
and
31
d,
and both end portions are covered by the load side bracket
31
a
and the anti-load side bracket
31
e.
Of these, the harmonic reduction gears
41
are composed of a circular spline
42
which is fixed on the inner circumference of the actuator frame
31
b,
and at the same time is annular and has inner teeth, the flexible spline
43
which is attached to the inside of the circular spline
42
, coupled to an output shaft
32
, is cup-shaped and has outer teeth, and an elliptically shaped wave generator
44
which is attached to the inside of the flexible spline
43
via a bearing
47
and coupled to a rotation shaft
33
. Also, the bearings
45
and
46
support the output shaft
32
and are given a preload by an elastic member
50
. And, the bearings
48
and
49
support the rotation shaft
33
and are given a preload by an elastic member
51
.
Further, the electric motor
34
is provided with a rotor
38
composed of a yoke
39
fitted to the rotation shaft
33
and a permanent magnet
40
that becomes a magnetic pole, and at the same time a stator
35
composed of a stator core
36
secured opposite to the outer circumferential side of the rotator
38
via a gap and an armature winding
37
that generates a rotation magnetic field at the stator core
36
.
Further, the rotation position detector
52
is composed of an optical type encoder including a rotation disk
53
that becomes a rotation portion fixed at the rotation shaft
33
, a fixed slit
54
that becomes a fixing portion of the rotation position detector, which is opposed to the rotation portion, a light emitting element
55
, and a light receiving element
56
. When light from the light emitting element
55
is projected onto the rotation disk
53
, the light receiving element
56
repeats receiving and non-receiving of light via the fixed slit and detects the receiving and non-receiving of light as ON and OFF electric signals. After that, an angle of the rotor is calculated by a calculation circuit (not illustrated).
Next, a description is given of the actions thereof.
When a current flows from a drive circuit (not illustrated) into the armature winding
37
of the stator
35
, a drive torque is generated in the permanent magnet
40
of the rotor
38
, and the rotor
38
rotates at a high speed by the drive torque. Next, since the wave generator
44
coupled to the rotation shaft
33
of the rotor rotates, the flexible spline
43
is elliptically flexed via the bearing
47
and is engaged with the circular spline
42
at both end positions in the long axis direction of an ellipse in the wave generator
44
. At this time, relative rotation is generated between the flexible spline
43
and the circular spline
42
, wherein a remarkably reduced rotation force is transmitted from the flexible spline
43
to the output shaft
32
and is outputted therefrom.
However, in the prior art, since the harmonic reduction gears, electric motor and rotation position detector are coupled to each other in a line in a series, the length in the axial direction is made longer especially between the harmonic reduction gears and the electric motor, and between the electric motor and the rotation position detector. Further, the space of the rotation position detector disposed in the axial direction is increased, and this becomes a problem in view of downsizing and lightening of the weight thereof.
Also, since the harmonic reduction gears, electric motor and rotation position detector are, respectively, fixed at three actuator frames, the number of components is increased, resulting in an increase in the number of assembling steps, wherein another problem occurs, resulting in an increase in production costs thereof.
Further, there is a request for improving a torque capacity of an actuator in addition to a request of attempting downsizing and lightening of weight of the actuator. For this reason, it is necessary to make large the outer diameter of the rotor at a position where the permanent magnet thereof is installed, and to increase a drive torque of the rotor. However, in a structure in any of the prior arts, the outer diameter of the stator and actuator frame is increased if the outer diameter of the rotor is increased. Therefore, the cubic volume and weight of the entire electric motor are incidentally increased, and there is a problem which runs counter to the downsizing, lightening of weight and increasing of the torque in an actuator.
The present invention was developed to solve these and other problems, and it is therefore an object of the invention to provide an inexpensive reduction gears-integrated actuator that is capable of shortening the length of the entire actuator in its axial direction and increasing a drive torque without running counter to downsizing and lightening of its weight.
BRIEF SUMMARY OF THE INVENTION
In order to solve the above-described problems, the invention is constructed as described below.
A reduction gears-integrated actuator according to the first aspect of the invention comprises a hollow cylindrical actuator frame; a circular spline that is fixed on the above-described actuator frame and has inner teeth on the inner circumference thereof; a cylindrical flexible spline that has outer teeth engageable with the inner teeth of the above-described circular spline, and has an output shaft of the actuator coupled to the end face thereof; a elliptical wave generator attached on the inner circumference of the above-described flexible spline; a rotation shaft for driving to rotate the above-described wave generator; an electric motor including a rotor provided with a magnetic pole consisting of a permanent magnet and stator provided with an armature winding for generating a rotation magnetic field at a stator core opposed to the outer circumferential side of the above-described rotor via a gap; a rotation portion of a rotation position detector fixed on the above-described rotation shaft; and a fixing portion of the rotation position detector, which is opposed to the rotation portion of the above-described rotation position detector; wherein the above-described rotor constitutes a cup-shaped rotation yoke integrally mounted at the center thereof

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