Winding method and winding structure of stator for rotation detector, and electric motor comprising rotation detector

This application is a 371 application of PCT/JP2012/000075 having an international filing date of Jan. 10, 2012, which claims priority to JP2011-014960 filed Jan. 27, 2011, the entire contents of which are incorporated herein by reference.

The present invention relates to a winding method and winding structure of a stator for rotation detector, and an electric motor comprising the rotation detector.

A conventional winding method of a stator for rotation detector is disclosed in Patent Literature 1. FIG. 9 is a configuration of the winding method of a stator shown in Patent Literature 1. In this method, output winding 101 and output winding 102 , which are different in phase from each other, are wound around slots defined by the adjacent magnetic poles. Output winding 101 is wound around every other slot. Output winding 102 is wound around all slots over output winding 101 . Then, output winding 101 is wound over output winding 102 around the slots that do not have output winding 101 as the undermost layer. When the windings around the slots are viewed in cross section, the order of winding output windings 101 and 102 is alternated from one slot to the next. In FIG. 9 , the conventional stator for rotation detector includes stator core 103 .

According to this method, output windings 101 and 102 can be misaligned so as to reduce variation between output signal A from output winding 101 and output signal B from output winding 102 , thereby having high detection accuracy of a rotation angle.

There are, however, following problems with the aforementioned winding method of Patent Literature 1.

In the rotation detector of this type, in principle, the output signals have different amplitudes depending on their rotation angles. Therefore, the number of turns of the output windings around the slots needs to be varied sinusoidally. This causes the contribution to the flux linkage between these output windings to be different from slot to slot. As a result, the winding method of Patent Literature 1 has limitations in reducing the imbalance of contribution to the flux linkage between these output windings.

More specifically, assume that output winding 101 has the same number of turns in all slots, and output winding 102 also has the same number of turns in all slots. Then, the contribution to the flux linkage can be equalized between output windings 101 and 102 in all slots by alternating the order of winding them from one slot to the next, thereby reducing variation between the output signals. In the rotation detector of the present invention, however, the number of turns of each output winding around the slots needs to be varied sinusoidally as described above. Thus, since the number of turns of each output winding differs from slot to slot, it is difficult to equalize the contribution to the flux linkage between output windings 101 and 102 only by alternating the order of winding them from one slot to the next.

Patent Literature 1: Japanese Patent No. 3681167

In the winding method of a stator for rotation detector according to the present invention, the stator includes a stator core that is ring shaped and has a plurality of magnetic poles, which are arranged at regular intervals in the circumferential direction and project either to the inner diameter side or the outer diameter side of the stator core. The stator core has a first output winding and a second output winding, which are different in phase by 90 degrees from each other and are wound around slots defined by the adjacent magnetic poles. The first output winding has N 1 (s) turns, and the second output winding has N 2 (s) turns, each of the N 1 (s) turns and the N 2 (s) turns being varied sinusoidally through the slots. The N 1 (s) turns of the first output winding is divided by a split ratio α into N 1 a (s) turns and N 1 b (s) turns. A lower-layer first output winding having the N 1 a (s) turns is continuously wound, as the undermost layer, around all slots. The second output winding is continuously wound around all slots over the lower-layer first output winding. An upper-layer first output winding having the N 1 b (s) turns is continuously wound around all slots over the second output winding. The split ratio α is adjusted only in one or more given slots.

According to the present invention, the number of turns of the first output winding is divided by a given split ratio α, and the split ratio is adjusted in given slots. As a result, a balance is struck in the contribution to the flux linkage between the first output winding and the second output winding, thereby reducing variation between output signals A and B. This results in reducing variation between angular signals generated from output signals A and B, thereby achieving high angle detection accuracy.

FIG. 1 shows a stator for rotation detector according to a first embodiment of the present invention.

FIG. 2 shows the distributions of the numbers of turns of output windings in the stator for rotation detector according to the first embodiment.

FIG. 3 is a configuration of a winding method of the stator for rotation detector according to the first embodiment.

FIG. 4 is a cross sectional view of the stator for rotation detector taken along line 4 - 4 of FIG. 1 .

FIG. 5 shows the distributions of the numbers of turns of output winding 1 in the stator according to the first embodiment when the split ratio α of windings 1 is varied sinusoidally.

FIG. 6 is a cross sectional view of an electric motor according to the first embodiment.

FIG. 7 is a cross sectional view of output windings in the stator for rotation detector according to a second embodiment of the present invention.

FIG. 8 is a cross sectional view of output windings in the stator for rotation detector according to a third embodiment of the present invention.

FIG. 9 is a configuration of a winding method of a conventional stator for rotation detector.

A method of winding a wire on a stator for rotation detector according to the present invention will now be described as preferred embodiments.

First Exemplary Embodiment

FIG. 1 shows a stator for rotation detector according to a first embodiment of the present invention. As shown in FIG. 1 , the stator for rotation detector according to the first embodiment includes stator core 3 , windings (not shown), and insulators 6 . Stator core 3 is ring shaped, and has magnetic poles 4 , which are arranged at regular intervals in the circumferential direction and project either to the inner diameter side or to the outer diameter side of stator core 3 . The windings are wound around slots 5 defined by adjacent magnetic poles 4 . Insulators 6 are arranged in such a manner as to cover stator core 3 from both sides in the axial direction, thereby electrically insulating between stator core 3 and the windings. The windings, which are not illustrated in FIG. 1 , consist of output winding 1 (first output winding) and output winding 2 (second output winding). Output winding 1 generates a sinusoidal output signal A according to the rotation angle. Output winding 2 generates a sinusoidal output signal B, which is different in phase by 90 degrees from the signal A. The number of turns of each of output windings 1 and 2 around the slots is varied sinusoidally, so that output windings 1 and 2 generate the output signals A and B, respectively. FIG. 2 shows the distributions of the numbers of turns of the output windings. These distributions are merely one example; output windings 1 and 2 have only to be different in phase by 90 degrees from each other.

FIG. 3 is a configuration of the winding method of the stator for rotation detector according to the first embodiment. As shown in FIG. 3 , output winding 1 has N 1 (s) turns, which is varied sinusoidally through the slots. The N 1 (s) turns is divided by a split ratio α into N 1 a (s) turns of output winding 1 a (lower-layer first output winding) and N 1 b (s) turns of output winding 1 b (an upper-layer first output winding). Output winding 1 a having the N 1 a (s) turns is continuously wound, as the undermost layer, around all slots. Output winding 2 is continuously wound around all slots over output winding 1 a . Output winding 1 b having the N 1 b (s) turns is continuously wound around all slots over output winding 2 . The end of output winding 1 a is electrically connected to the start of output winding 1 b.

FIG. 4 is a cross sectional view of the stator for rotation detector taken along line 4 - 4 of FIG. 1 . As shown in FIG. 4 , in the winding method of stator for rotation detector according to the first embodiment, output winding 1 b is disposed over output winding 2 , and output winding 1 a is disposed under output winding 2 in stator core 3 . Thus, output windings 1 a and 1 b sandwich output winding 2 therebetween. Between stator core 3 and output winding 1 a , there are disposed insulators 6 . The split ratio α is adjusted in the slots where the detection accuracy decreases, so that the ratio of the N 1 a (s) turns to the N 1 b (s) turns can be different from slot to slot.

FIG. 5 shows the distributions of the numbers of turns of output winding 1 when the split ratio α is varied sinusoidally. Varying the split ratio α sinusoidally as shown in FIG. 5 allows output winding 1 to be divided into output winding 1 a and output winding 1 b equally in all slots.

The aforementioned winding method and winding structure of the stator for rotation detector according to the present invention provide the following advantages. Adjusting the split ratio α results in adjusting the contribution to the flux linkage between output windings 1 and 2 , and the impedance of these windings. Thus, the split ratio α can be adjusted individually in the slots where the detection accuracy decreases. This can reduce variation between output signals A and B, thereby achieving high detection accuracy of the rotation angle.

FIG. 6 is a cross sectional view of an electric motor according to the first embodiment. The electric motor of the present embodiment includes the stator for rotation detector shown in FIG. 1 . As an example of the electric motor, the present embodiment will describe a brushless motor of inner rotor type, in which a rotor is rotatably disposed on the inner periphery side of the stator.

In FIG. 6 , the electric motor includes stator (stator for rotation detector) 10 having stator core 34 . Around stator core 34 , stator winding 35 is wound as an output winding via insulators 36 , which are resins to insulate stator core 34 . Stator core 34 is molded with insulating resin 33 as a molding material and with other fixing members. In the present embodiment, these components are integrally molded into stator 10 having a substantially cylindrical contour.

The electric motor further includes rotor 14 inserted into the inside of stator 10 via a gap. Rotor 14 includes disk-shaped rotation body 30 and shaft 37 . Rotation body 30 includes rotor core 31 . Shaft 37 penetrates through the center of rotation body 30 so as to fasten rotation body 30 . Rotor core 31 includes permanent magnets, which are arranged in the circumferential direction and are opposite to the inner periphery side of stator 10 . In the structure of FIG. 6 , rotor core 31 and ferrite resin magnets 32 as the permanent magnets are integrally molded. The inner periphery side of stator 10 and the outer periphery side of rotation body 30 are opposite to each other.

Shaft 37 of rotor 14 is supported by two bearings 15 , which are cylindrical and includes iron balls. The inner rings of bearings 15 are fixed to shaft 37 . In FIG. 6 , shaft 37 is supported by bearing 15 a on the output side on which shaft 37 projects from the body of the brushless motor, and is supported by bearing 15 b on the other side. The outer ring of bearing 15 a on the output side is fixed with conductive metal bracket 17 . The outer ring of bearing 15 b on the side opposite to the output side is fixed with insulating resin 33 , which is molded with the other components. Thus, shaft 37 is supported by two bearings 15 so as to rotate rotor 14 .

Second Exemplary Embodiment

FIG. 7 is a cross sectional view of output windings in the stator for rotation detector according to a second embodiment of the present invention. As shown in FIG. 7 , in the winding method of the stator for rotation detector according to the second embodiment, output winding 11 (first output winding) has N 11 (s) turns, and output winding 12 (second output winding) has N 12 (s) turns, each of the N 11 (s) turns and the N 12 (s) turns being varied sinusoidally through the slots. The N 11 (s) turns is divided by the split ratio α into N 11 a (s) turns of output winding 11 a (lower-layer first output winding) and N 11 b (s) turns of output winding 11 b (upper-layer first output winding). The N 11 a (s) turns is larger than the N 11 b (s) turns. Output winding 11 a having the N 11 a (s) turns is continuously wound, as the undermost layer, around all slots of stator core 13 via insulators 16 . Output winding 12 is continuously wound around all slots over output winding 11 a . Output winding 11 b having the N 11 b (s) turns is continuously wound around all slots over output winding 12 . The end of output winding 11 a is electrically connected to the start of output winding 11 b.

When output winding 12 has a larger contribution to the flux linkage than output winding 11 , output winding 11 is wound a large number of turns at the undermost layer. This reduces the contribution of output winding 11 a to the flux linkage, thereby equalizing the contribution between output windings 11 and 12 . This results in reducing variation between output signals A and B, thereby achieving high detection accuracy of the rotation angle.

Third Exemplary Embodiment

FIG. 8 is a cross sectional view of the output windings in the stator for rotation detector according to a third embodiment of the present invention. As shown in FIG. 8 , in the winding method of the stator for rotation detector according to the third embodiment, output winding 21 (first output winding) has N 21 (s) turns, and output winding 22 (second output winding) has N 22 (s) turns, each of the N 21 (s) turns and the N 22 (s) turns being varied sinusoidally through the slots. The N 21 (s) turns is divided by the split ratio α into N 21 a (s) turns of output winding 21 a (lower-layer first output winding) and N 21 b (s) turns of output winding 21 b (upper-layer first output winding). The N 21 a (s) turns is smaller than the N 21 b (s) turns. Output winding 21 a having the N 21 a (s) turns is continuously wound, as the undermost layer, around all slots of stator core 23 via insulators 26 . Output winding 22 is continuously wound around all slots over output winding 21 a . Output winding 21 b having the N 21 b (s) turns is continuously wound around all slots over output winding 22 . The end of output winding 21 a is electrically connected to the start of output winding 21 b.

When output winding 21 has a larger contribution to the flux the linkage than output winding 22 , output winding 21 is wound a large number of turns at the third layer. This increases the contribution of output winding 21 a to the flux linkage, thereby equalizing the contribution between output windings 21 and 22 . This results in reducing variation between output signals A and B, thereby achieving high detection accuracy of the rotation angle.

The first to third embodiments are merely exemplary; the present invention is not limited to these embodiments and can be properly modified.

For example, the stator in the first to third embodiments is inner rotor type having stator teeth (magnetic poles) on the inner circumference surface side of the stator core. Alternatively, the stator may be outer rotor type having the stator teeth on the outer circumference surface side of the stator core.

The number of the stator teeth in the stator core in the first to third embodiments is not limited to 12; it may be more or less than 12.

In the stator in the first to third embodiments, only output windings are wound; alternatively, excitation windings for generating excitation signals may be wound under the output windings as in variable reluctance resolvers.

As described hereinbefore, in the winding method of the stator for rotation detector according to the present invention, the stator includes stator core 3 that is ring shaped and has magnetic poles 4 , which are arranged at regular intervals in the circumferential direction and project either to the inner diameter side or to the outer diameter side of stator core 3 . Stator core 3 has output winding 1 and output winding 2 , which are different in phase by 90 degrees from each other and are wound around slots 5 defined by adjacent magnetic poles 4 . Output winding 1 has N 1 (s) turns, and output winding 2 has N 2 (s) turns, each of the N 1 (s) turns and the N 2 (s) turns being varied sinusoidally through the slots. The N 1 (s) turns of output winding 1 is divided by a split ratio α into N 1 a (s) turns and N 1 b (s) turns. Output winding 1 a having the N 1 a (s) turns is continuously wound, as the undermost layer, around all slots. Output winding 2 is continuously wound around all slots over output winding 1 a . Output winding lb having the N 1 b (s) turns is continuously wound around all slots over output winding 2 . The split ratio α is adjusted only in one or more given slots.

Thus, adjusting the split ratio α results in adjusting the distance between each of output windings 1 , 2 and the magnetic flux flowing through the magnetic poles, thereby adjusting the contribution to the flux linkage between output windings 1 and 2 . As a result, the contribution to the flux linkage can be equalized between output windings 1 and 2 in all slots, thereby reducing variation between the output signal A from output winding 1 and the output signal B from output winding 2 . According to the detection principle, the detection accuracy varies depending on the machining accuracy and assembly accuracy. This allows the contribution to the flux linkage between output windings 1 and 2 to be minutely adjusted by adjusting the split ratio α only in the slots corresponding to the angle at which the detection accuracy decreases. This results in reducing variation between output signals A and B, thereby achieving high angle detection accuracy.

Furthermore, it is preferable that the split ratio α be varied sinusoidally through slots 5 . It is also preferable that the distribution of the N 1 (s) turns of output winding 1 through slots 5 be equal to the change in the split ratio α through the slots.

The N 1 (s) turns of output winding 1 is varied sinusoidally through slots 5 . Therefore, if the N 1 (s) turns is divided by a constant value in all slots 5 , the positional relationship between magnetic pole 4 and each of output windings 1 a , 1 b differs from slot to slot. This causes the contribution to the flux linkage between output windings 1 a and 1 b to be different from slot to slot, thereby having higher variation between output signals A and B. To overcome this problem, the distribution of the N 1 (s) turns of output winding 1 through slots 5 is made equal to the change in the split ratio α through slots 5 . As a result, output windings 1 a and 1 b can be in the same proportion in all slots 5 . This allows the contribution to the flux linkage between output windings 1 and 2 to be minutely adjusted so as to reduce variation between output signals A and B, thereby achieving high angle detection accuracy.

Furthermore, it is preferable that output winding 1 be wound in such a manner that the N 1 a (s) turns is larger than the N 1 b (s) turns.

When output winding 1 has a smaller contribution to the flux linkage than output winding 2 , output winding 1 is wound in such a manner that the N 1 a (s) turns can be larger than the N 1 b (s) turns. As a result, output winding 1 can be wound a large number of turns in a position near magnetic poles 4 . This increases the contribution of output winding 1 to the flux linkage, thereby being balanced with the contribution of output winding 2 . This results in reducing variation between output signals A and B, thereby achieving high angle detection accuracy.

It is preferable that output winding 1 be wound in such a manner that the N 1 a (s) turns is smaller than the N 1 b (s) turns.

When output winding 1 has a larger contribution to the flux linkage than output winding 2 , output winding 1 is wound in such a manner that the N 1 a (s) turns can be smaller than the N 1 b (s) turns. As a result, output winding 1 can be wound a larger number of turns in a position distant from magnetic poles 4 . This reduces the contribution of output winding 1 to the flux linkage, thereby being balanced with the contribution of output winding 2 . This results in reducing variation between output signals A and B, thereby achieving high angle detection accuracy.

In the winding structure of the stator for rotation detector according to the present invention, the stator includes stator core 3 that is ring shaped and has a plurality of magnetic poles, which are arranged at regular intervals in the circumferential direction and project either to the inner diameter side or the outer diameter side of stator core 3 . Stator core 3 has output windings 1 and 2 , which are different in phase by 90 degrees from each other and are wound around slots 5 defined by adjacent magnetic poles 4 . Output winding 1 has N 1 (s) turns, and output winding 2 has N 2 (s) turns, each of the N 1 (s) turns and the N 2 (s) turns being varied sinusoidally through slots 5 . The N 1 (s) turns of output winding 1 is divided by a split ratio α into N 1 a (s) and N 1 b (s). The winding structure includes output winding 1 a , output winding 2 , and output winding 1 b . Output winding 1 a having the N 1 a (s) turns is continuously wound, as the undermost layer, around all slots. Output winding 2 is continuously wound around all slots over output winding 1 a . Output winding 1 b having the N 1 b (s) turns is continuously wound around all slots over output winding 2 . The split ratio α is adjusted only in one or more given slots.

The present invention provides a stator for rotation detector which has output signals with low variation. The stator can be mounted on various electrical devices such as resolvers for detecting the rotation angle of the shaft of an electric motor.