Resolver integrated type motor

Details Resolver integrated type motor Resolver integrated type motor

2002-09-27

2004-08-17

Ponomarenko, Nicholas (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S216006, C310S0400MM

Reexamination Certificate

active

06777843

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resolver integrated type motor, more specifically a motor to which is integrated a resolver for detecting an angular position or speed around a shaft.
2. Related Art
There is a great demand for improvement of driving performance, reduction of size, and reduction of cost of motors, especially for those used as a power source in various types of machines. In order to improve the driving performance of a motor, it is effective to dispose a resolver or an equivalent detector (hereinafter referred to as the “resolver”) for detecting an angular position or a speed around a motor shaft or of a rotor and to feedback the resolver output to control and drive systems so to make feedback control of a rotation position and speed of the motor. In one known structure adopted to dispose a resolver on a motor, a resolver shaft is attached to the motor shaft, as shown in FIG.
3
and FIG.
4
. In another type of known structure, a resolver rotor is fitted to a single shaft shared by the motor and the resolver, as shown in FIG.
5
. It should be noted that, with the exception of
FIG. 2
, the drawings of the present application show the structure in the vicinity of the non-load side end of the motor shaft, because in general the resolver is disposed on the non-load side end opposite to the loaded side end. The loaded end, to which a load to be rotated is connected, is not shown in the drawings.
A resolver
201
shown in FIG.
3
and
FIG. 4
has a structure in which the center of its shaft, hereinafter referred to as the “resolver shaft
202
”, and of a shaft of a motor
203
, hereinafter referred to as the “motor shaft
204
”, are aligned and directly connected with a bolt
205
, as shown in
FIG. 3
which shows an axial cross section. Therefore, when the motor shaft
204
rotates, the resolver shaft
202
also rotates at the same rate. A resolver rotor
206
is fixed to an end of the resolver shaft
202
. The resolver rotor
206
has a radial non-uniformity around the resolver shaft
202
as shown in
FIG. 4
which shows a plan view of
FIG. 3
observed from above. In an example of a 6-pole synchronous motor, the resolver rotor
206
has a shape which has a concavity and a convexity repeated at a cycle of 2&pgr;/3 [rad], namely the contour of an equilateral triangle having rounded corners, as shown in FIG.
4
. The resolver rotor
206
is configured by vertically stacking silicon steel plates as shown in FIG.
3
and caulking at the points indicated by
218
a
,
218
b
and
218
c
as shown in FIG.
4
. The resolver rotor
206
is positioned and affixed to the resolver shaft
202
during production of the resolver
201
in such a manner that the center of rotation of the resolver shaft
202
and the shape center of the motor shaft
204
coincide with that shown by the broken chain line
208
in FIG.
3
. Therefore, the resolver rotor
206
accurately synchronizes with the rotation of the motor to which it is coaxially connected.
The loaded end of the motor shaft
204
is supported by a motor bracket
213
through an unshown load side bearing, and the non-load end is supported by the motor bracket
213
through a non-load side bearing
216
. The resolver shaft
202
is supported by a housing
211
of the resolver
201
through bearings
207
a
,
207
b
. The housing
211
is tightened to a coupling
212
at a point which is not shown. In addition, the coupling
212
is fixed to the motor bracket
213
with bolts
215
a
,
215
b
. Therefore, the housing
211
does not rotate when the motor shaft
202
rotates. A stator yoke (hereinafter referred to as the “resolver stator yoke”)
210
of the resolver
201
is fixed to the housing
211
with pan-head machine screws
217
a
,
217
b
,
217
c
,
217
d
so that the inner circumferential surface of the housing
211
is opposite to the periphery section of the resolver rotor
206
, and the shape center of the resolver rotor
206
and the center of a circular curve formed by a pole tooth edges of the resolver stator yoke
210
agree with each other. The resolver stator yoke
210
is also formed by vertically stacking silicon steel plates as shown in
FIG. 3
so as to create a structure corresponding to that of the resolver rotor
206
. Pole teeth are formed in a circumferential direction on the inner circumferential surface of the resolver stator yoke
210
. The pole teeth are tooth-shaped pits and projections on which a resolver stator winding
209
is wound, and, when the motor
203
is a 6-pole synchronous motor, 12 pole teeth are formed as shown in FIG.
4
. The above structure is further covered with a cover
214
for protection.
In the structure described above, when the resolver rotor
206
rotates with the rotation of the motor, a gap between the curved side surface of the resolver rotor
206
and the pole teeth of the resolver stator yoke
210
varies. As a result, a change in inductance caused in each winding can be electrically detected from outside. From the detected result, a rotation position of the resolver rotor
206
can be detected within a range of 2&pgr;/3 [rad]. A rotation speed can be detected by monitoring the detected rotation position in time sequence and determining its change with time. Thus, a magnetic position and a speed of the motor
203
can be detected by the resolver
201
.
However, the resolver
201
shown in FIG.
3
and
FIG. 4
has a disadvantage in that accurate detection requires that the positional relationship between the resolver rotor
206
and the resolver stator yoke
210
be precisely set at the time of production. Among various type of errors, a connection error between the motor shaft
204
and the resolver shaft
202
can be absorbed by the coupling
212
, but the bearings
207
a
,
207
b
, the coupling
212
and the shaft
202
designed specifically for the resolver
201
are required. This results in increased size and cost of the motor.
To solve the above problems, a resolver
401
, which is shown its cross section taken in its axial direction in
FIG. 5
, may adopt a structure of normal fitting to use a common shaft for both the motor and the resolver, so to eliminate the coupling and the bearings, thereby decreasing motor size and reducing manufacturing costs.
In the resolver
401
shown in
FIG. 5
, a resolver shaft
402
and a motor shaft
403
are integrally formed, so that their centers coincide, as shown in the figure by the broken chain line
404
. A resolver rotor
406
is formed of silicon steel plates, which have an equilateral triangle form (six poles) with rounded corners having a radial irregular shape, by stacking the plates in a vertical direction as shown in
FIG. 3
, and then fixing them to the resolver shaft
402
via a spacer
411
. Specifically, the resolver
406
is securely adhered to the outer circumferential surface of the spacer
411
so that the center of the inner diameter of the spacer
411
and the shape center of the irregular shape of the resolver rotor
406
agree with each other, and the spacer
411
is inserted on the resolver shaft
402
by faucet joint type normal fitting. The spacer
411
is fixed to the resolver shaft
402
with a nut
405
. The spacer
411
is fitted between the resolver rotor
406
and the resolver shaft
402
to prevent an unexpected stress applied to the resolver rotor
406
from disturbing magnetic detection, as would occur should the resolver rotor
406
be directly attached onto the resolver shaft
402
or attached via a normal faucet joint fitting or the like.
Meanwhile, a resolver stator yoke
412
is fixed to a housing
414
with pan head machine screws
410
a
,
410
c
so that the center of the outer circumferential surface of the housing
414
and the center of the circular shape formed by the pole tooth edges of the resolver stator yoke
412
coincide. A motor bracket
415
has a section in which a bearing
407
is placed and a section in which the outer circumference of the housing
414
is inserted, so that the coaxiality or

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