 |
Description  |
|
|
The present invention relates to the field of the multipolar resolver which
may employ either a sine or cosine coil for the rotor, or more in
particular to a novel and compact multipolar resolver requiring no coil on
the rotor.
Generally, the resolver is of dual polarity and has a stator wound with two
different types of coils, i.e., sine and cosine coils at an electrical
angle of 90 degrees. The rotor is also wound with sine and cosine coils.
In the case of the resolver used for position detection instead of
calculation, however, it often suffices if only one type of coil is wound
on either stator or rotor. Nowadays, the brushless resolver is widely used
which has only one type of coil on the rotor.
In these conventional resolvers, the rotor is required to be provided with
coil, and therefore the resolver having few poles, say, two poles accounts
for the greater proportion of the products. As a result, manufacture of
multipolar resolvers is limited greatly in regard to their structure. In
fact, the multipolar resolvers presently produced have at most four or six
poles.
As a rotational angle detector proposed by the present applicant, the
apparatus as disclosed in German Application Publication No. 2,301,483
granted to the present applicant is known. This rotational angle detector
utilizes the principle of the vernier scale and is constructed as briefly
described below. A coil is provided at substantially the central part of
the stator for generating magnetic fluxes, while a coil for detecting the
rotational angle of the rotor is provided on each of a plurality of stator
poles positioned along the circumference having the same axis as the
rotor. The plurality of coils are for detecting a digital angle.
An object of the present invention is to provide a multipolar resolver
which requires no coils on the rotor.
Another object of the present invention is to provide a multipolar resolver
utilizing the principle of the vernier scale, thus simplifying the general
configuration to facilitate production on the one hand and to reduce the
production cost on the other hand.
According to one aspect of the present invention, there is provided a
multipolar resolver comprising a substantially cylindrical rotor of
magnetic material with 5n rotor poles provided equidistantly on the outer
periphery thereof where n is a positive integer, a stator of magnetic
material with 4n stator poles provided equidistantly along the
circumference concentric with the axis of the rotor, a central coil
provided on the stator along substantially the same axis as the rotor
axis, and sine and cosine coils wound on the stator poles, the sine and
cosine coils being wound alternately on the stator poles, the sine coils
being connected in series with each other and wound in opposite directions
of winding alternately, and the cosine coils being connected in series
with each other and wound in opposite directions of winding alternately.
According to another aspect of the present invention, there is provided a
multipolar resolver comprising a substantially cylindrical rotor of
magnetic material with 3n rotor poles provided equidistantly on the outer
periphery thereof where n is a positive integer, a stator of magnetic
material with 4n stator poles provided equidistantly along the
circumference concentric with the axis of the rotor, a central coil
provided on the stator along substantially the same axis as the rotor
axis, and sine and cosine coils wound on the stator poles, the sine and
cosine coils being wound alternately on the stator poles, the sine coils
being connected in series with each other and wound in opposite directions
of winding alternately, and the cosine coils being connected in series
with each other and wound in opposite directions of winding alternately.
The above and other objects, features and advantages of the present
invention will be made more clear from the following description with
reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram showing the construction of a conventional
two-pole resolver;
FIG. 2 is a diagram for explaining the operating principle of the two-pole
resolver shown in FIG. 1;
FIGS. 3A and 3B are sectional and plan views respectively schematically
showing the construction of the rotational angle detector already proposed
by the present applicant;
FIGS. 4A and 4B are a plan view schematically showing the construction of
an embodiment of a multipolar resolver according to the present invention
and a sectional view taken in the line IVB--IVB respectively;
FIGS. 5A to 5E are diagrams for explaining the operation of the multipolar
resolver shown in FIGS. 4A and 4B;
FIG. 6 is a diagram for explaining the operating principle of the
multipolar resolver shown in FIGS. 4A and 4B;
FIG. 7 is a graph showing sin .theta..sub.E which is the sine component of
the output voltage of the multipolar resolver shown in FIGS. 4A and 4B;
and
FIG. 8 is a graph showing sin .theta..sub.E which is the sine component of
the output voltage of the multipolar resolver according to another
embodiment of the present invention.
Prior to explanatin of the preferred embodiments of the present invention,
the above-mentioned prior art will be described again with reference to
the companying drawings.
The construction of the above-mentioned conventional two-pole resolver is
schematically shown in FIG. 1. In this diagram, reference numeral 1 shows
a rotor, numeral 2 a stator, numeral 3 a stator pole, numeral 4 a single
rotor coil, numeral 5 a sine coil provided on the stator, and numeral 6 a
cosine coil provided on the stator. If the number of the resolver poles is
increased to four or six in this conventional construction, the number of
stator poles is increased to twice or thrice accordingly and the rotor
geometry is increasingly complicated, so that the general configuration is
complicated on the one hand and the dimension thereof are increased on the
other hand.
The operating principle of the two-pole resolver of FIG. 1 will be seen
from FIG. 2. When the rotor coil 4 is excited with the exciting frequency
of sin .omega.t, the outputs of sin .theta..multidot.sin .omega.t and cos
.theta..multidot.sin .omega.t are produced respectively from the stator
coils 5 and 6, where .theta. is the rotational angle of the rotor.
The above-mentioned rotational angle detector suggested by the present
applicant is shown in FIGS. 3A and 3B. It will be seen that the disc-like
rotor 30 of magnetic material includes radially equidistantly-provided
eleven arms 30A to 30K and a rotational shaft 31. The protrusion 33
provided at the central part of the stator 32 of magnetic material is
wound with a primary coil 34. The stator 32 has ten stator poles 35A to
35J provided on the circumferential periphery thereof, and the stator
poles thereof are wound with secondary coils 36A to 36J respectively. Upon
application of the exciting voltage to the primary coil 34, the magnetic
fluxes 37 generated by the primary coil 34 pass through the rotor 30,
rotor arms, stator poles 35 and stator 32, thus producing an induced
voltage in the stator coil 36. If the difference between the number of
stator poles and the number of rotor arms is one as in the above-mentioned
construction, only one of the stator poles is opposed to or aligned with
only one of the arms all the time according to the principle of the
vernier scale. Therefore, by detecting the stator coil from which an
induced voltage is generated, the rotational angle of the rotor is
detected.
The rotational angle detector of this construction, however, is unable to
display the functions of the resolver of the present invention.
An embodiment of the multipolar resolver according to the present invention
will be described below with reference to FIGS. 4A and 4B. In the
drawings, the substantially cylindrical rotor 11 made of a magnetic
material such as ferrite requiring no coils includes a rotor shaft 19 and
ten rotor poles 12 designated by B.sub.1 to B.sub.10 equidistantly
arranged on the outer periphery thereof. The substantially disc-shaped
stator 13 of magnetic material such as ferrite includes a protrusion 13A
at substantially the central part thereof and eight stator poles 14
designated by P.sub.1 to P.sub.8 arranged substantially equidistantly on
the outer periphery and extending in the same direction as the axis 19 of
the rotor. The stator protrusion 13A is wound with the central coil 15,
and the bases of the stator poles P.sub.2, P.sub.4, P.sub.6 and P.sub.8
are wound with sine coils 16, while the poles P.sub.1, P.sub.3, P.sub.5
and P.sub.7 are wound with cosine coils 17. As apparent from the drawings,
the poles P.sub.2, P.sub.4, P.sub.6, P.sub.8 wound with the sine coils 16
are arranged on the outer periphery of the stator 13 alternately with the
poles P.sub.1, P.sub.3, P.sub.5, P.sub.7 wound with the cosine coils 17.
The coils S.sub.1, S.sub.2, S.sub.3 and S.sub.4 of the poles P.sub.2,
P.sub.4, P.sub.6 and P.sub.8 are connected in series with each other. The
coils C.sub.1, C.sub.2, C.sub.3 and C.sub.4 of the poles P.sub.1, P.sub.3,
P.sub.5 and P.sub.7 are also connected in series with each other. The sine
coils 16 are connected in series with each other in opposite directions of
winding in such a manner that the polarity of the output voltage may be
reversed at the electrical angle of 180 degrees. In other words, the sine
coils are wound in the counterclockwise direction on the stator poles
P.sub.2 and P.sub.6 and in the clockwise direction on the poles P.sub.4
and P.sub.8. In similar fashion, the cosine coils 17 are wound on the
stator poles P.sub.1 and P.sub.5 in the counterclockwise direction and on
the poles P.sub.3 and P.sub.7 in the clockwise direction. The
substantially cylindrical rotor 11 is rotatably arranged in a
substantially concave cylindrical space formed by the side walls of the
stator protrusion 13A and a plurality of stator poles 14. The side wall of
the stator protrusion 13A is thus arranged in proximity to the side
surface of the rotor perpendicular to the rotor shaft 19. Also, the rotor
pole 12 and the stator pole 14 are arranged in proximity to each other.
The stator 13 is preferably formed integrally with the stator poles 14.
The magentic fluxes 18 generated by the excitation of the central coil 15
are thus passed through the stator protrusion 13A, stator 13, stator pole
14, rotor pole 12 and rotor 11 as shown in FIG. 4B. Although every coil
has the same number of turns, the induced voltage of each coil varies
depending on the degree of proximity between rotor pole 12 and stator pole
14, i.e., the degree of magnetic coupling therebetween. The total of the
voltages induced in the coils S.sub.1, S.sub.2, S.sub.3 and S.sub.4 shown
in the drawing is produced at the sine coil 16. In similar manner, the
total of the voltages induced in the shown coils C.sub.1, C.sub.2, C.sub.3
and C.sub.4 is obtained at the cosine coil 17.
Next, explanation will be made of the operation for producing an output
voltage with the rotation of the resolver upon excitation of the central
coil with reference to FIGS. 5A to 5E and FIG. 7.
(1) In the case where the rotor pole B.sub.1 is opposed to or aligned with
the stator pole P.sub.1 (FIG. 5A);
The rotor pole B.sub.6 and the stator pole P.sub.5 are also aligned with
each other so that the degree of magnetic coupling between coils C.sub.1
and C.sub.3 is maximum, thus producing the maximum voltage. On the other
hand, the magnetic coupling between coils C.sub.2 and C.sub.4 is small,
thus producing a minimum voltage. The coils C.sub.2 and C.sub.4 are wound
in the direction opposite to the coils C.sub.1 and C.sub.3, so that the
cosine coil 17 produces the voltage cos .theta..sub.E .multidot.sin
.omega.t which is equal to the sum of the voltage across coils C.sub.1 and
C.sub.3 less the sum of the voltages across the coils C.sub.2 and C.sub.4.
The degree of magnetic coupling between poles P.sub.2 and B.sub.2, between
poles P.sub.4 and B.sub.5, between poles P.sub.6 and B.sub.7 and between
poles P.sub.8 and B.sub.10 are substantially equal to each other.
Therefore, the sum of the voltages across coils S.sub.1 and S.sub.3 less
the sum of the voltages across the coils S.sub.2 and S.sub.4 is
substantially zero, so that the output voltage sin .theta..sub.E
.multidot.sin .omega.t of the sine coil 16 is zero.
Referring to FIG. 7 showing the value of sin .theta..sub.E which is the
sine component of the rotational angle of the rotor, the value of sin
.theta..sub.E of the voltage sin .theta..sub.E .multidot.sin .omega.t
obtained from the sin coil 16 when the rotor pole B.sub.1 is aligned with
stator pole P.sub.1 is zero as shown by point A.
(2) In the case where the rotor pole B.sub.2 is aligned with stator pole
P.sub.2 (FIG. 5B):
In FIG. 5A, the angular displacement between stator pole P.sub.2 and rotor
pole B.sub.2 is 1/40 (=1/8-1/10) of a rotation, i.e., 9 degrees (=45-36
degrees). Thus when the rotor 11 makes 1/40 of a rotation, i.e., 9 degrees
from the position shown in FIG. 5A, it achieves the state shown in FIG.
5B. Since the pole B.sub.7 is aligned with pole P.sub.6 and the coils
S.sub.1 and S.sub.3 are coupled magnetically to the greatest degree, a
maximum voltage is produced. The coils S.sub.2 and S.sub.4 are
magnetically coupled with each other to the lowest degree, and therefore a
minimum voltage is produced therefrom. The coils S.sub.2 and S.sub.4 are
wound in the direction opposite to the coils S.sub.1 and S.sub.3 as
described above, so that the sine coil 16 produces an output voltage sin
.theta..sub.E .multidot.sin .omega.t which is equal to the sum of the
voltages across the coils S.sub.1 and S.sub.3 less the sum of the voltages
across coils S.sub.2 and S.sub.4. The value of sin .theta..sub.E is shown
by point B in FIG. 7. The degree of magnetic coupling between poles
P.sub.1 and B.sub.1, between P.sub.3 and B.sub.3, between P.sub.5 and
B.sub.6 and between P.sub.7 and B.sub.8 are substantially equal to each
other, with the result that the sum of the voltages across the coils
C.sub.1 and C.sub.3 less the sum of voltages across the coils C.sub.2 and
C.sub.4 is substantially zero. Thus the output voltage cos .theta..sub.E
.multidot.sin .omega.t of the cosine coil 17 is substantially zero.
(3) In the case where the rotor pole B.sub.3 is aligned with stator pole
P.sub.3 (FIG. 5C):
When the rotor 11 makes 1/40 of a rotation or 9 degrees from the position
of FIG. 5B, the state shown in FIG. 5C is attained. The pole B.sub.8 is
also aligned with the pole P.sub.7, and the degree of magnetic coupling
between coils C.sub.2 and C.sub.4 is maximum, thus producing the maximum
voltage. On the other hand, the degree of magnetic coupling between coils
C.sub.1 and C.sub.3 is lowest and therefore a minimum voltage is produced.
Since the coils C.sub.1 and C.sub.3 are wound in the direction opposite to
the direction of coils C.sub.2 and C.sub.4, the cosine coil 17 produces an
output voltage cos .theta..sub.E .multidot.sin .omega.t which is equal to
the sum of the voltages across the coils C.sub.2 and C.sub.4 less the sum
of the voltages across the coils C.sub.1 and C.sub.3. In this case, the
phase of the output voltage is displaced by 180 degrees from that in the
case of FIG. 5A. The degree of magnetic coupling between poles P.sub.2 and
B.sub.2, between P.sub.4 and B.sub.4, between P.sub.6 and B.sub.7 and
between P.sub.8 and B.sub.9 are substantially the same. The sum of the
voltages across the coils S.sub.2 and S.sub.4 less the sum of the voltages
across the coils S.sub.1 and S.sub.3 is zero, so that the output voltage
sin .theta..sub.E .multidot.sin .omega.t of the sine coil 16 is
substantially zero. The value of sin .theta..sub.E is indicated by point C
in FIG. 7.
(4) In the case where rotor pole B.sub.4 is aligned with stator pole
P.sub.4 (FIG. 5D):
When the rotor 11 makes 1/40 of a rotation from the position of FIG. 5C,
the state of FIG. 5D is attained. The pole B.sub.9 is also aligned with
pole P.sub.8 and the degree of magnetic coupling between coils S.sub.2 and
S.sub.4 is maximum, thus producing a maximum voltage. On the other hand,
the degree of magnetic coupling between coils S.sub.1 and S.sub.3 is
lowest, and therefore both S.sub.1 and S.sub.3 produce a minimum voltage.
The coils S.sub.1 and S.sub.3 are wound in the direction opposite to that
of the coils S.sub.2 and S.sub.4, and therefore the sine coil 16 produces
an output voltage sin .theta..sub.E .multidot.sin .omega.t which is the
sum of the voltages across the coils S.sub.2 and S.sub.4 less the sum of
voltages across coils S.sub.1 and S.sub.3. In this case, however, the
phase of the output voltage is displaced by 180 degrees from that in the
case of FIG. 5B. The value of sin .theta. .sub.E is indicated by point D
in FIG. 7. The degree of magnetic coupling between P.sub.1 and B.sub.10,
between P.sub.3 and B.sub.3, between P.sub.5 and B.sub.5 and between
P.sub.7 and B.sub.8 are substantially equal to each other. The sum of the
voltages across the coils C.sub.2 and C.sub.4 less the sum of the voltages
across the coils C.sub.1 and C.sub.3 is substantially zero, so that the
output voltage cos .theta..sub.E .multidot.sin .omega.t of the cosine coil
17 is substantially zero.
(5) In the case where the rotor pole B.sub.5 is aligned with stator pole
P.sub.5 (FIG. 5E):
When the rotor 11 makes 1/40 of a rotation from the position of FIG. 5D,
the state of FIG. 5E is attained. The pole B.sub.10 is aligend with the
pole P.sub.1, which is quite the same electrical situation as that shown
in FIG. 5A. In other words, the rotor 11 returns to quite the same state
electrically as the original state after making 1/10 (=1/40.times.4) of a
rotation as shown progressively in FIGS. 5A, 5B, 5C, 5D and 5E in that
order, the 1/10 rotation of the rotor 11 being equivalent to the
electrical angle of 360 degrees. The value of sin .theta..sub.E is
indicated by point E in FIG. 7.
In the above-mentioned embodiment, the rotor has ten poles, and therefore
one mechanical rotation of the rotor 11 corresponds to ten times the
electrical angle of 360 degrees, thus indicating a resolver of 20 poles.
It is seen from the diagram of FIG. 6 for explaining the operating
principle that upon excitation of the central coil 15 by the sine wave of,
say, 10 KHz, the rotation of rotor 11 by the mechanical angle of
.theta..sub.M causes the output wave forms of cos .theta..sub.E
.multidot.sin .omega.t and sin .theta..sub.E .multidot.sin .omega.t to be
produced from the cosine coil 17 and the sine coil 16 respectively. The
character .theta..sub.E shows an electrical angle, and there is a
well-known relation shown below between the mechanical angle .theta..sub.M
and the number of poles N.
##EQU1##
In the foregoing embodiment of the present invention, the central coil 15
is used as the primary coil and the sine coil 16 and the cosine coil 17 as
the secondary coil. They may of course be used in reverse way.
Further although the above-mentioned embodiment of the present invention
employs eight stator poles and ten rotor poles, it is not limitative but
only illustrative. In other words, the number of stator poles n times 4
and the number of rotor poles n times 5 or 3 may be used alternatively as
shown in Table 1 below. It is in order to obtain sine and cosine outputs
that the number of stator poles n times 4 is employed.
TABLE 1
__________________________________________________________________________
Number of
Number of
Number of
Number of
Number of
Number of
n stator poles
rotor poles
resolver poles
stator poles
rotor poles
resolver poles
__________________________________________________________________________
1 4
5 10 4
3 6
2 8
10 20 8
6 12
3 12
15 30 12
9 18
4 16
20 40 16
12 24
5 20
25 50 20
15 30
. . . . . . .
. . . . . . .
. . . . . . .
__________________________________________________________________________
An output waveform in a multipolar resolver according to another embodiment
is shown in FIG. 8. This voltage waveform represents a sine component of
the rotor rotational angle produced by a 12-pole resolver having eight
stator poles and 6 rotor poles. As explained above, the multipolar
resolver according to the present invention has a coil only on the stator
but not on the rotor. This eliminates the need of the slip ring on the one
hand and simplifies the general construction on the other hand, leading to
many advantages in cost and maintenance.
Furthermore, by introducing the vernier concept, the fabrication of a
multipolar resolver having 20 or more poles is greatly facilitated,
resulting in the conspicuous dual advantages of a greater number of
divisions available for each rotor rotation and a higher accuracy of each
rotor rotation without structural or dimensional limitations. The higher
accuracy means that it is no longer necessary to drive the resolver at
high speed by raising the gear ratio, leading to the advantage that the
resolver may be directly coupled to the motor shaft in numerically
controlled machine tool field. Since the resolver according to the present
invention is adapted to be directly coupled to the motor shaft without
sacrificing the required accuracy, the resolver may be constructed
integrally with the motor, thus greatly contributing to a simplified
detecting mechanism. Also, the availability of an increased number of
divisions makes possible reliable detection of a speed component.
* * * * *
|
|
 |
|
 |
Description |
|
