JPH0534897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of winding a brushless motor, particularly suitable for driving small, labor-saving equipment.

[Background technology of the invention and its problems]

DC servo motors have traditionally been widely used to drive various labor-saving devices such as electric robots. However, DC servo motors are equipped with a mechanical commutator consisting of a commutator and brushes, and are plagued with problems such as lack of reliability due to wear of the brushes, so recently brushless motors that use electronic commutators have been There is a tendency to switch to the adoption of

Furthermore, the development of equipment to which servo motors are applied is increasingly focused on smaller size and higher performance. In other words, the technical means required for an extremely small brushless motor include being small and lightweight, having excellent controllability, and having a simple structure and being able to provide it at low cost. To achieve this, the following measures must be implemented across both the driving torque generating section and the rectifying rotation angle detecting section, which are the constituent elements of the brushless motor.

First, in order to reduce the size and weight, it is necessary to apply a motor type that enables high efficiency and a high torque-to-weight ratio to the torque generating section.

Next, in order to improve controllability, the torque ripple caused by the configuration of the torque generating part is kept as small as possible to avoid irregular rotation of the rotor, which is usually called cogging, and the rectification sensor also has high precision. The objective is to enable accurate rotation angle detection.

Furthermore, in order to simplify the structure, instead of being bound by the conventional method of mechanically connecting the motor, which is the torque generating part, and the sensor for rectification via a coupling, we decided to use a built-in sensor type. Furthermore, it is necessary to pursue a simple construction method that integrates a motor and a sensor into a sensor body.

As a concrete example of the above-mentioned measures, a brushless motor (unexamined patent application Showa 58
-73477)" is proposed.

This proposal uses a permanent magnet synchronous machine as the type of torque generator, so it has excellent efficiency and torque-to-weight ratio, making it suitable for compactness and weight reduction. In addition to applying a child-shaped rotation angle detection device, this and the torque generating section are combined by electromagnetic action rather than mechanical coupling means, making it possible to assemble the motor and sensor using the conventional mechanical coupling method. This has the advantage that not only can torque ripple caused by errors be avoided, but the structure is simple and manufacturing is easy.

With the sensor combination brushless motor that has already been proposed, two of the above-mentioned main requirements for brushless motors, namely, reduction in size and weight and simplification of structure, are almost solved. However, one more item remains,
In other words, in terms of the pursuit of controllability, as will be described in detail below, sufficient measures have not been taken, and moreover, simply addressing this point will neglect responding to other requirements. This caused a delay in its practical application due to its unique characteristics.

First, let us consider the torque ripple of a motor according to the prior art in the case of a four-pole motor with reference to FIG. This motor consists of a stator core 1, an armature winding 2 consisting of U, V, and W phase armature windings 2a, 2b, and 2c wound in its slots, and U, V, and W phase armature windings 2a, 2b, and 2c wound in the same slots. The detection winding 3 includes V and W phase detection windings 3a, 3b, and 3c.

FIG. 2 shows the mutual relationship between the stator and rotor. The rotor arranged inside the stator core 1 consists of a shaft 4b and a magnetic body 4 supported by the shaft 4b.
a, and a permanent magnet 4c attached to the magnetic body 4a.

The third torque ripple when the magnetic fluxes of the gap planes located symmetrically with respect to the center 0 of the cross section are equal is
As shown in the figure. In Figure 3, 5 is a magnetic charge and 6
represents the permeance change, and 7 represents the force acting on the magnetic charge 5. This makes it possible to know the torque ripple when the rotor is rotated assuming that a pair of magnetic charges are fixed on the rotor. In addition, in this case, there is a permeance ripple of 12 cycles per rotor rotation corresponding to the number of slots 12, so this brushless motor with 12 slots is
Torque ripple occurs due to magnetic permeance changes 12 times per revolution.

This torque ripple occurs in extremely small motors.
Since the inertia of the rotor is small, there is little inertial damping, and torque ripple appears almost unchanged on the output shaft, so reducing this is essential for motors used in servo applications.

Conventionally, various measures have been taken to improve this torque ripple. Examples include skewing of the stator core or rotor field, the use of magnetic wedges or fully closed slots, the rotor field structure configured to smoothly change the magnetic flux distribution at the change of poles, and the number of slots designed to cancel out torque ripple. This includes selection, etc.

Among the above-mentioned improvement measures, taking stator core skew as an example, the problems are described below: (a) Processes such as stator core assembly and armature winding work become complicated.

(b) Since thrust is generated in the axial direction, it can cause vibration in servo motors used in applications where the direction of rotation is frequently changed.
Bearing reliability decreases.

(c) The effective magnetic flux φ is expressed by the following equation (1).

φ=φ ₀ ×sin α/2/α/2 (1) where α=πx/τ, φ ₀ is the magnetic flux when there is no skew, x is the skew amount, and τ is the pole node.

As is clear from the above equation (1), the effective component of the magnetic flux decreases to the skew amount x. To compensate for this decrease, the number of turns must be increased. Furthermore, since the effective area of the slot is reduced, the diameter of the conductor used for the winding must be reduced. In addition, it can be seen from the equation shown below that the length of the coil side also increases.

Δl _c =√ _c ² + ² −l _c ………(2) However, Δ _c is the increase in the length of the coil side, and _c is the original length of the coil side.

For the reasons mentioned above, the resistance of the winding increases and the efficiency decreases.

(d) The inductance L of the coil can be determined by the following equation (3).

L=Λ・n ² ………(3) However, Λ==μ・S/l _n is permeance, μ is magnetic permeability, S is magnetic flux linkage area, _n is magnetic path length,
n is the number of turns.

In the above equation, as the number of turns n increases, the inductance L increases in proportion to its square.

Furthermore, since the effective width of the slot decreases, the term l _n in the equation for Λ becomes smaller, and inversely proportional to this, the slot leakage magnetic flux increases and the inductance increases.

The power factor decreases due to the increase in inductance due to these causes, which causes an increase in the drive power supply capacity and imposes a burden on control.

As mentioned above, on the one hand, skew has the advantage of reducing torque ripple and improving control performance, but on the other hand, it causes problems in terms of control, such as increasing power supply capacity and imposing a burden on control. Not only do they exhibit contradictory behavior, but they also lead to numerous problems such as complicating the manufacturing process, lowering reliability, and lowering efficiency, resulting in many sacrifices.

Such problems occur not only in the status queue but also in almost the same way in all cases, except for those that are addressed by selecting the number of slots.

Now, let us consider the problem when trying to deal with torque ripple by selecting the number of slots.

In order to deal with torque ripple by changing the number of slots, it is conceivable to adopt so-called fractional slots. For example, when taking measures against torque ripple by increasing the number of slots in the example shown in FIG. 1, if the target motor is extremely small, the number of slots cannot be significantly increased due to processing constraints.
Therefore, as shown in FIG. 4, an appropriate number of slots to reduce torque ripple, for example, 15 slots, will be considered.

In the case of 15 slots, in the same way as when considering the torque ripple for 12 slots in Figure 3, consider the behavior of a set of magnetic charges located symmetrically with respect to the center O in Figure 5. Make it. To avoid confusion, if we assume that the distribution of changes in permeance is sinusoidal, as can be seen from Figure 5, forces act on this pair of magnetic charges in a direction that weakens each other's forces. , the distribution of permeance changes is sinusoidal, and the center O
Under the condition that the magnetic fluxes on the gap surfaces at points symmetrical with respect to each other are equal, there is no torque ripple at all.

However, this has been done conventionally for this stator core. An example of so-called fractional slot winding is fractional slot (slot #1 to #15) winding as shown in Figure 6.
The magnetomotive force vector diagram of each slot is shown in Figure 7 (magnetomotive force vector diagram of conventional fractional slot winding).
It can be seen that this results in an imbalance as shown in the figure. This increases the harmonic magnetomotive force, which increases the torque ripple during operation.
Torque ripple countermeasures, such as selecting the number of slots to deal with torque ripple and applying conventional winding to this, on the one hand reduce torque ripple due to slot permeance, but on the other hand, harmonics There is a contradictory behavior in that the torque ripple increases due to the increase in magnetomotive force.

The problems of the prior art have been described above, but in short, it has been found that when countermeasures against cogging are taken using the prior art, other problems are induced.

[Purpose of the invention]

The purpose of the present invention is to reduce torque ripple, which is an important issue in improving controllability, which is one of the requirements for brushless motors, without impairing the detection function, and to reduce the torque ripple, which is an important issue in improving controllability, which is one of the requirements for brushless motors. It is an object of the present invention to provide a winding method for a brushless motor that can be constructed so as to satisfy the requirements of simplicity at the same time.

[Summary of the invention]

The winding method for the brushless motor of the present invention is such that the rotor is equipped with a permanent magnet in the field and the number of slots is an integral multiple of the number of phases, and the value divided by the number of poles of the field is a fraction. A method of winding a brushless motor consisting of an armature winding in which each phase winding is divided into a plurality of phase conductors, and a stator in which a detection winding for detecting the rotation angle of the rotor is inserted into a slot. A first step in which axes in both positive and negative directions are drawn for each phase in the radial direction from the center point on the plane, with an angular difference corresponding to the phase difference between each phase of the winding; The second step is to draw a unit vector toward each of the slot positions set on the circumference of the radius, and decompose each unit vector into the directions of both adjacent axes to obtain component vectors for each phase (positive and negative). and a third step of determining the number of conductors on each coil side for each phase (positive, negative, negative) to be inserted into each slot based on the ratio of the magnitude of each component vector determined in the second step, and inserting the conductors into each slot. Connect the coil sides inserted in step 3 to each other.
How can a coil with a phase difference of 180° and an equal number of conductors form one coil, and a fourth step in which coils of the same phase are connected to form each phase winding, and the number of stator slots is set as a field? At least one detection coil is inserted in each slot near the slot pitch corresponding to the quotient when divided by the number of magnetic pole pairs, and each detection coil is arranged at equal pitches in the circumferential direction corresponding to the number of phases of the armature winding. and a fifth thread for deriving a rotation angle detection terminal from each output end and a neutral point of the detection winding. .

[Embodiments of the invention]

An embodiment in which the present invention is applied to a four-pole brushless motor will be described below. It has already been explained that when the number of slots is set to 15, the torque ripple due to slot permeance is canceled out and eliminated.

Therefore, in this case, it is assumed that a three-phase armature winding according to the present invention is applied. In this case, the vector of the ampere conductor in each slot, that is, the slot magnetomotive force, must have a direction that corresponds to the position angle of each slot and be equal in magnitude, as shown in Figure 8 (current vector diagram). If it is possible to do so, it would be ideal because torque ripple caused by harmonic components in the rotational magnetomotive force can be substantially eliminated.

These conditions are determined so that, assuming that coil sides belonging to two phases are accommodated in each slot, the vector of the combined magnetomotive force due to them matches the magnetomotive force vector of each slot in Fig. 8. It can be achieved if you try. To do this, as shown in Figure 9 (current vector diagram of the winding to generate a balanced three-phase magnetomotive force), first, from the center point O on the circular vector plane, point U, V, W in the radial direction. With an angle difference (120°) corresponding to the phase difference of each phase winding, the axes OU, OU′, OV,
Draw OV′, OW, OW′. Furthermore, unit vectors are drawn toward each of the slot positions #1 to #15 set on the circumference of a predetermined radius from the same center point O, and each unit vector is decomposed into the directions of both axes adjacent to it. Find component vectors for each phase, positive and negative. In the example shown in Figure 9, the U-phase axis is located near slot position #1, that is, slightly closer to the V-phase side.
OU is set, and the unit vector toward slot position #1 is the two axes adjacent to it.
Two component vectors U→ ₂ , V→ in the directions of OU and OV′
It is decomposed into ₃ ′. The number of conductors on each side of the coil for each positive and negative phase to be inserted into each slot is determined at a ratio corresponding to the magnitude of each component vector determined as described above. Thus, component vectors U ₁ to U ₅ and U ₁ ' to which correspond to the current vectors of the U, V, and W phases.
_U5 ', _V1 to V5 and _{V1 '} to _V5 ', and _W1 to _W5 and _W1 ' to _W5 ' can be determined.

If we assume that the coil sides determined as above and inserted into each slot have a phase difference of 180° and have the same number of conductors to form one coil, then as shown in Fig. 10. A spatial arrangement as shown in FIG. 1 can be obtained, and from this, the winding width of each coil, that is, the coil pitch can also be determined. Therefore, as shown in Fig. 11, these coil groups in the same phase are interconnected to form armature wires 2a, 2b, 2c for each phase, and by connecting them in a star shape, a balanced three-phase armature winding is created. can be obtained.

As is clear from the above description, according to the present invention, it is possible to obtain an ideal armature winding in which the occurrence of torque ripple is suppressed as much as possible.

As mentioned above, in order to improve the control performance of a brushless motor, it is important to not only suppress torque ripple but also to improve the accuracy of the rotation angle detection section.

By the way, as already proposed, this brushless motor has an unbalanced rotor in which the magnetic poles of the permanent magnet 4c and the magnetic poles of the magnetic body 4a are mutually arranged along the gap circumference as shown in FIG. It consists of a permanent magnet field, and the permeance distribution of the rotor generated between it and the stator has a fundamental wave wavelength that is equal to the wavelength of the fundamental wave of the main magnetic field, making it suitable for rectifying sensors. Then, the rotation angle is detected by electromagnetically converting and detecting it using this as a rotation angle detection signal source. To put this principle into practice, it is necessary to devise a detection winding that is sensitive to the signal source but insensitive to noise.

In the present invention, at least one detection coil is installed in a slot near an equal dividing point (points separated from each other by 71/2 slot pitches) obtained by dividing the gap circumference of the brushless motor by the number of pole pairs of the main magnetic field (2 in this example). For example, as shown in Figure 12 (detection coil permeance signal waveform diagram), detection coils aa ₁ to a ₄
Deploy.

In this example, the detection coil _a1 is placed in slots 2 and 4.
Insert detection coil _A2 into slots 9 and 10, and into slot 1.
A total of four detection coils are arranged, _A3 in slots 0 and 11, and detection coil _A4 in slots 11 and 12.To help with the discussion, the arrangement of these detection coils is arranged according to the spacing of one pole of the rotor. It is shown in conjunction with the changes in the permeance signal before and after the rotation (from 0° (Fig. 12a) to 180° (Fig. 12b) in electrical angle).

As is clear from this figure, the palm ances of the magnetic paths interlinked with each detection coil change significantly as the rotor rotates, so using this group of detection coils allows for highly sensitive It can be seen that a detection winding is formed.

Here, noise resistance, which is another requirement for the detection winding, must also be addressed. In particular, this brushless motor is a sensor combination type, and the detection coil is placed in the main magnetic field for torque generation. , so-called speed electromotive force (hereinafter referred to as induced voltage) may be mixed into the detection signal and impair the rotation angle detection function, and countermeasures against this are essential.

Regarding this induced voltage, as shown below, we carefully investigated the number of windings of each detection coil and the influence of the mutual connection method, and decided to minimize the winding coefficient of the detection winding with respect to the main magnetic field. Therefore, this can be an effective countermeasure.

Figure 13 (Detection winding induced voltage vector diagram)
For the coil arrangement example shown in Fig. 12, the induced voltage of each detection coil is illustrated using vectors, and with the induced voltage vector E ₃ of detection coil a ₁ as a reference vector, the other detection coils a ₁ ′, a ₂ ′ , a ₂ ″, a ₄ , the phase and magnitude of the induced voltage vectors E ₁ , E ₂ ′, E ₂ ″, E ₄ are compared. Here, as shown in FIG. 12, the number of turns of each detection coil is set to coil a ₁
(In principle, this is equivalent to connecting two coils a ₁ ′, a ₁ ″ in series, and for convenience of explanation, we will treat them as two coils.)
A ₂ and Coil A ₄ have 1 turn each, Coil A ₃ has 3 turns
An example is shown in which the coil _a3 has a different polarity from the other coils. In this way, the winding pitch of each coil, that is, the coil pitch, is all the same value (1 slot pitch), so the magnitude of the induced voltage in each coil is proportional to the number of windings (number of turns), making quantitative handling easy. Become.

The winding configured as described above is used as a unit detection coil in the detection winding, and is arranged at equal pitches in the circumferential direction to correspond to the number of phases (three phases in this example) of the armature windings 2a, 2b, and 2c. Detection sensitivity and noise resistance are improved by arranging the detection windings 3a, 3b, and 3c by connecting them in a star shape, and by leading out rotation angle detection terminals from each output end and neutral point of the detection windings. An excellent detection winding can be constructed.

FIG. 14 shows the armature windings 2a, 2b, 2c and the detection winding 3 described with reference to FIGS. 7 to 13.
FIG. 12 is a winding diagram of a brushless motor according to an embodiment of the present invention having coils a, 3b, and 3c, in which the numbers of individual coils correspond to those in FIGS. 10 and 11. FIG. In the same figure, a shows the configuration of each winding, b shows the number of turns of the detection winding, and c shows the number of turns of the armature winding.

〔Effect of the invention〕

As is clear from the above explanation, the winding direction of the brushless motor according to the present invention not only makes it possible to counter torque ripple, which was difficult in the past, without sacrificing efficiency or power factor, but also enables high It is also possible to include a rotation angle detection section for rectification that is sensitive and resistant to noise, and it is possible to realize a sensor-combined brushless motor that has a simple structure, is suitable for small size and weight reduction, and has excellent control performance.

[Brief explanation of drawings]

Figure 1 shows the developed winding diagram of the stator in a conventional 4-pole brushless motor, and Figure 2 shows its rotor and winding diagram.
Figure 3 is a front view of the 12-slot stator core. Figure 3 is a waveform diagram showing the cogging situation when there are 12 slots.
The figure shows a cross-sectional view of the 4-pole rotor and the 15-slot stator core. Figure 5 is a waveform diagram showing how cogging is reduced with the 15-slot. Figure 6 is the developed winding diagram of the conventional fractional slot. Fig. 7 is a magnetomotive force vector diagram of a conventional fractional slot winding, Fig. 8 is a magnetomotive force vector diagram of a fractional slot winding according to an embodiment of the present invention, and Fig. 9 is a magnetomotive force vector diagram for generating a balanced three-phase magnetomotive force. A vector diagram for explanation, FIG. 10 is an armature winding diagram of this embodiment, FIG. 11 is a balanced three-phase winding diagram thereof, and FIG. A waveform diagram showing when the rotation for one pole interval is 0 degrees in electrical angle, Figure 12b is a waveform diagram similarly showing when it is 180 degrees, Figure 13 is a vector diagram of the induced voltage in the detection winding, Figure 14a
14 is a developed winding diagram of the armature winding and the detection winding in this embodiment, FIG. 14b is a diagram of the number of turns of the detection winding, and FIG. 14c is a diagram of the number of turns of the armature winding. 1... Stator core, 2... Armature winding, 2a, 2
b, 2c...U phase, V phase, W phase armature winding, 3...
Detection windings, 3a, 3b, 3c...U phase, V phase, W phase detection windings, _a1 to _a4 ...coils.

Claims (1)

[Scope of Claims] 1. A rotor with a permanent magnet in the field, and slots selected such that the number of slots is an integral multiple of the number of phases and the value divided by the number of poles of the field is a fraction, A brushless motor winding method consisting of an armature winding in which each phase winding is divided into multiple phase conductors, and a stator in which a detection winding for detecting the rotation angle of the rotor is inserted, the winding being centered on a vector plane. From the point in the radial direction, the positive and negative axes 0U, 0U'; 0V, 0V,
First step is to draw 0V'; A second step involves decomposing the vector into the directions of both adjacent axes to obtain component vectors for each phase (positive and negative), and each component vector is inserted into each slot at the ratio of the magnitude of each component vector determined in the second step. The third step is to determine the number of conductors on each coil side for each phase (positive and negative) and insert them into each slot, and to connect the coil sides inserted in the third step to each other.
One coil is formed by having a phase difference of 180° and the same number of conductors, and a group of coils of the same phase are connected to each phase armature winding 2a, 2b,
For each phase, at least one detection coil is inserted into the slot near the slot pitch corresponding to the quotient of the number of stator slots divided by the number of pole pairs of the field. The detection coils are arranged at equal pitches in the circumferential direction and correspond to the number of phases of the armature winding, and are connected in a star shape to form detection windings 3a, 3b, and 3c. 1. A method of winding a brushless motor, comprising: a fifth step of deriving a rotation angle detection terminal from a positive point.