JPH01122352A - Synchronous ac servomotor - Google Patents

Abstract

PURPOSE:To increase the rate of effective utilization of a permanent magnet, by a method wherein the N-poles and the S-poles of permanent magnets of a rotor are formed so as to have different central angles respectively and a pair of armature windings, which are corresponding to the permanent magnets of a pair of N-pole and S-pole, are connected so that the winding directions of them are opposed to each other. CONSTITUTION:Permanent magnets 12, constituting the pair of poles of a rotor 5, are attached to the peripheral surface of the shaft of the rotor 5. AC control current is supplied to an armature winding 18 synohrcnizing with the timing signal of the rotating angle of the rotor 5. The permanent magnets 12 for the opposing N-poles and S-poles are formed so as to have different central angles respectively while at least one set of armature windings 18, which are corresponding to the N-pole and S-pole of permanent magnets 12, are connected so that the winding directions thereof are opposed to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a synchronous AC servo motor in which a permanent magnet is attached to the shaft circumferential surface of a rotor.

[Prior Art] Generally, in a synchronous AC servo motor, a sine wave control current is supplied to an armature winding wound around the throat of a stator.
It is also known that if the voltage induced in the armature winding by rotation of the rotor is a sinusoidal voltage, the torque of the rotor becomes constant and good rotation can be obtained. For this reason, conventionally, synchronous type AC servo motors have been proposed.

Among these, for example, as shown in Fig. 9, there is one in which four poles are formed in pairs of sector-shaped permanent magnets C having uniform thickness along concentric circles centered on the axis of rotor a. be.

This permanent magnet C magnetizes the fan-shaped central part to saturation magnetization,
It is considered that the degree of magnetization is gradually weakened from the center toward the outside so that the magnetic flux distribution in the air gap d becomes a sinusoidal distribution. Furthermore, as shown in FIG. 10, there is also a rotor f in which the circumferential end portions of the permanent magnets are thinner than the center portion by <(R>r). In this case, the permanent magnet is magnetized to saturation magnetization in all parts, but the center part is thicker than the circumferential ends, and the air gap i is narrower in the center and thicker in the circumferential ends. Since the air gap i is wide, the magnetic flux distribution at the air gap i becomes a sine wave distribution as in the case of FIG.

[Problems to be Solved by the Invention However, improvements in the margins were desired in the following points. Recently, as a permanent magnet for servo motors,
Rare earth magnets (for example, S m Co-based permanent magnets) have begun to be widely used because of their magnetic properties, but since rare earth magnets are scarce in resources and are expensive, it is extremely important to save them.

In the case of the permanent magnet C shown in Fig. 9, the central part of the fan-shaped permanent magnet C is magnetized to saturation magnetization, but as it moves toward the outside, the magnetization rate decreases to 100 [% Cor number [%]. Therefore, the effective utilization rate becomes very low. Therefore, no material savings can be made. Also, the 10th
In the case of the permanent magnet shown in the figure, the effective utilization rate is extremely good because all parts from the thick central part to the relatively thin ends are magnetized to saturation magnetization. Since the air gap l is wide, if the end portion is formed too thin, the permeance coefficient will decrease and the end portion will be demagnetized. Therefore, the end portions cannot be formed too thin, and the entire structure is formed thicker, resulting in a lower effective utilization rate and an ineffective way to save material.

Therefore, an object of the synchronous AC servo motor of the present invention is to make the voltage induced in the armature winding a sinusoidal waveform, increase the effective utilization rate of the permanent magnets, and save materials.

Nine pulses q lecture [Means for solving the problem] The synchronous AC servo motor of the present invention has a rotor in which permanent magnets constituting a pole pair are attached to the circumferential surface of the shaft, and a rotation angle of the rotor. a rotation angle detection unit that detects the rotation angle, and a rotation angle detection unit that is attached to a stator around the rotor to face the pole pair, and supplies an alternating current control current in synchronization with a rotation angle timing signal from the rotation angle detection unit. a synchronous AC servo motor, comprising: an armature winding in which at least one pair of N-pole and S-pole permanent magnets of the pole pair are formed with different center angle sizes; The present invention is characterized in that at least one set of the armature windings corresponding to the pole and south pole permanent magnets are connected so that the winding directions are opposite to each other.

[Function] In the synchronous AC servo motor of the present invention having the above configuration, at least one pair of N
The pole and south pole permanent magnets are formed with different center angle sizes, and at least one pair of the north pole and south pole permanent magnets are connected so that the winding directions of the armature windings are opposite to each other. When an alternating current control current is supplied to the armature winding in synchronization with the timing signal from the rotation angle detection section and the rotor rotates, the voltage induced in the stator armature winding has an approximately sinusoidal waveform. Torque fluctuations can be suppressed. The voltage induced in the armature winding at this time will be explained in detail with reference to FIG.

Figure 1 (A) shows the S-pole and N-pole permanent magnets and a part of the armature windings facing them, and Figure 1 (B) shows the voltage induced in each armature winding. represents. As shown in the diagram
A pair of armature windings P and Q corresponding to the S and N poles are connected with the winding directions opposite to each other as shown by the arrows in the figure.

First, when the relative position between the permanent magnets of the rotating rotor and the armature winding P is as shown by the dashed line ■, the armature winding P
The winding part PL on one side is located opposite the N-pole permanent magnet and generates a large induced electromotive force, but the winding part PR on the opposite side is located in the gap between the N-pole permanent magnet and the S-pole permanent magnet. They are located opposite each other and generate almost no induced electromotive force. Next, when the relative position between the permanent magnet and the armature winding P advances to the state indicated by the solid line ■, the winding portion PL is located at the north pole, and the winding portion PR is at a position opposite to the south pole. At this time, large induced electromotive forces having the same phase are generated in the winding portions PL and PR, respectively. Furthermore, when the relative position between the permanent magnet and the armature winding P reaches the state shown by the broken line ■, the winding portion PL remains at the N pole, but the winding portion PR again becomes S.
Located in the gap between the pole and the N pole, almost no induced electromotive force is generated, and the induced electromotive force of the entire winding becomes small.

As a result, as shown in FIG. 1(B), the voltage waveform induced in the armature winding P becomes a convex voltage waveform Vρ1. As the relative position between the armature winding P and the permanent magnet further advances, the voltage induced in the armature winding P next becomes a convex voltage waveform Vρ2 with an inverted phase.

On the other hand, the armature winding Q is provided so as to face a permanent magnet having a polarity opposite to that of the facing permanent magnet of the armature winding P, and furthermore, the armature winding Q is provided so as to face a permanent magnet having a polarity opposite to that of the permanent magnet facing the armature winding P, and furthermore, the armature winding Q is provided so as to face a permanent magnet having a polarity opposite to that of the permanent magnet facing the armature winding P. Because it is wound, the induced voltage VQI is in the same phase as the voltage induced in the armature winding P.

Produces VO2. Therefore, the voltage induced from a pair of armature windings to which armature winding P and armature winding Q are connected has an overlapping convex voltage waveform, which is close to a sine waveform.

[Embodiment] An embodiment of the synchronous AC servo motor of the present invention will be described below. FIG. 2 schematically shows the structure around the rotor of a synchronous AC servo motor. FIG. 3 shows the overall structure of a synchronous AC servo motor. FIG. 4 shows the circuit of the drive section that supplies the control current to the armature winding.

As shown in the figure, the synchronous AC servo motor 1 is a synchronous type in which the rotor rotates according to the frequency and width of the control current, and is permanently mounted on a yoke 9 attached to the shaft 7 of the rotor 5. A magnet 12 is attached with four poles, and this permanent magnet 1
The armature winding 1 is placed in the slot of the stator 14 opposite to the armature winding 1.
It has a sun-wound structure. Further, a resolver 21 that detects the rotation angle is attached to one end of the rotor 5, and the drive giPJ 22, which is configured as a well-known inverter circuit, is connected to the armature winding. A sinusoidal control current is supplied per day.

The permanent magnets 12 of the rotor 5 form a pair of two poles with S and N poles facing each other with the yoke 9 in between, and the permanent magnets 12 are longitudinal along the axial direction of the shaft 7. , electric angle slightly less than 120° (center angle 60° when centering on the axis)
The S pole 12a has a uniform thickness with an electrical angle of just under 180° (
The N-pole 12b has a uniform thickness and a center angle of a little less than 90°. This permanent magnet 12 is magnetized to saturation magnetization in all parts.

Also, the stator 1 facing the S pole 12a and the N pole 12b
There are 24 number 4 slots provided.

In order to explain the winding direction of the armature winding 18 wound in each slot, the position of each slot is conveniently shown as U of the control current.
U1~U8, ■1~VB, W corresponding to phase, ■phase, W phase
1 to W8. The armature windings 18 are connected in a star shape with a neutral point as shown in Figure 4, and the armature windings 18 in electrically adjacent positions (see Figure 4) are connected in the winding direction. They are connected in series in reverse. In other words, slot U1. U2
The winding direction between the thrower and the winding direction between the thrower [J3.04 and the thrower [J3.04] are opposite to each other and are connected in series. Note that slot U1. U
2 winding and slot U3. The winding between U4 and the winding may be connected in parallel as long as the winding directions are opposite to each other.

When a control current is supplied from the drive section 22 to the equal amount AC servo motor 1 having such a configuration, the rotor 5 rotates. At this time, FIG. 5 shows the voltage induced in the armature winding per day when the rotor rotates 50 times.

This will be schematically explained using FIGS. 6 and 7.

Fig. 5 shows the arrangement of permanent magnets attached around the rotor axis developed in a linear manner, and Fig. 6 shows the arrangement of the armature windings facing the permanent magnets developed in a linear form. . Since the armature windings facing the S and N poles are wound in opposite directions, the voltages induced in the armature windings when the rotor rotates are as shown in Figure 7, respectively. It is a superposition of the voltages induced in the armature winding. Therefore, the voltage induced in the armature winding has a stepped waveform, which is close to a sine waveform.

FIG. 8 shows the results of actually measuring the voltage waveform induced in the armature winding in one day. In addition to the effect of leakage magnetic flux from the end of the permanent magnet 12, the induced voltage waveform does not have a step-like waveform, but has an almost perfect sinusoidal waveform with rounded corners. Since the permanent magnet 5 with the N pole of 180° electrical angle and the S pole of 120° electrical angle is magnetized to saturation magnetization over all parts, the effective utilization rate is at least 0.8 [=(6
0+60)/(90+60) or more, which is larger than the conventional effective utilization rate of 0.64. Actually, the induced voltage constant of the permanent magnet 12 of this embodiment and the induced voltage constant when the permanent magnet C shown in FIG. 9 is magnetized to saturation magnetization over all parts are found to be 59.9. [mm
V/rpm, 61.5 [mmV/rpm,
The effective utilization rate is 0.974 (=59.9/61.5), which is an extremely large value.

As shown above, according to the equal quantity type AC servo motor 1 of this embodiment, the effective utilization rate of the magnet is increased and the material is You can save money.

In addition, the permanent magnet can be made in a simple shape, and all parts need to be magnetized to saturation magnetization, so the number of manufacturing steps can be reduced.

Furthermore, the inertia of the rotor 5 can be reduced, and the responsiveness of the servo motor in starting, accelerating, decelerating, stopping, etc. can be improved.

Note that the synchronous AC servo motor of the present invention is not limited to these embodiments; for example, a rotary encoder may be used instead of a resolver as the rotation angle detection section, or a rotor may have four permanent magnets. Of course, it can be implemented in various forms such as not only the pole structure but also two-pole and six-pole structures.

As described in detail above, according to the synchronous AC servo motor of the present invention, the effective utilization rate of the magnets is increased without impairing the sinusoidal waveform of the voltage induced in the armature windings. This has the excellent effect of reducing the amount of waste.

In addition, the permanent magnet can be made in a simple shape, and all parts need to be magnetized to saturation magnetization, so the number of manufacturing steps can be reduced.

Furthermore, the inertia of the rotor can be reduced, and the responsiveness of the servo motor, such as starting, accelerating, decelerating, and stopping, can be improved.

[Brief explanation of the drawing]

Figure 1 (A) is an explanatory diagram showing the S-pole and N-pole permanent magnets and a part of the armature winding facing them.
B) is an explanatory diagram showing the voltage induced in each armature winding, Fig. 2 is an explanatory diagram schematically showing the structure around the rotor of the synchronous AC servo motor of the example, and Fig. 3 is an explanatory diagram showing the structure around the rotor of the synchronous AC servo motor. An explanatory diagram showing the overall structure of an AC servo motor. Figure 4 is a circuit diagram showing the drive unit that supplies control current to the armature winding. Figure 5 is the arrangement of permanent magnets attached around the rotor shaft. Figure 6 is a developed diagram showing the arrangement of the armature windings of the stator in a straight line. Figure 7 is a graph showing the time change of the voltage induced in the armature windings. FIG. 8 is a graph showing the actual measured change in voltage induced in the armature winding over time, and FIGS. 9 and 10 are explanatory diagrams showing the structure of a conventional rotor. 1... Synchronous AC servo motor 5... Rotor 12... Permanent magnet 1 day... Armature winding 21... Resolver 22... Drive section

Claims (1)

[Scope of Claims] A rotor in which permanent magnets constituting a pair of poles are attached to a circumferential surface of a shaft; a rotation angle detection unit that detects a rotation angle of the rotor; Installed opposite to the pole pair,
A synchronous AC servo motor comprising: an armature winding to which an AC control current is supplied in synchronization with a rotation angle timing signal from the rotation angle detection section; Pole and S pole permanent magnets are formed with different center angle sizes, and at least one set of armature windings corresponding to the N and S pole permanent magnets have winding directions opposite to each other. A synchronous AC servo motor characterized by being connected as follows.