JPH02179249A - Small-sized motor - Google Patents

Abstract

PURPOSE:To obtain sufficient starting torque as an induction motor in case of starting and to make it possible to operate efficiently with a magnet as a synchronous motor in case of operation by providing both cage type secondary conductors and the magnet to a rotor of a small-sized motor. CONSTITUTION:A composite rotor 1 is constituted of a rotor core 2 of a layer- built electromagnetic steel plate, cage type conductors 3 of aluminum die-casting, a magnet 4a, a rotor yoke 5 which is a path of a magnet flux and notches 6 provided to the rotor core to prevent the magnet flux from short-circuiting. The torque is generated in the cage type conductors 3 by rotating magnetic field of frequency to be oscillated by a self-excited inverter, the rotor 1 starts to revolve, a revolution speed increases, and when it reaches a sufficient level, it is pulled into the synchronous torque between the magnet 4 and the rotating magnetic field to make the synchronous rotation.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a small electric motor that is driven by an alternating current generated by a self-excited oscillation circuit, and that is inexpensive, highly efficient, and can obtain a wide rotational speed control range. be.

Conventional technology In recent years, as the performance of small electric motors used in blowers, pumps, etc. has improved, the number of revolutions has been increasingly controlled. Efficient and inexpensive products are required.

Hereinafter, an example of the conventional small electric motor mentioned above will be explained with reference to the drawings.

FIGS. 3 and 4 show an example of a conventional driving method for controlling the rotation speed of a small electric motor.

In FIG. 3, 8 is a stator core made of laminated electromagnetic steel sheets. 9 is a shaded wire ring which generates a rotating magnetic field from an alternating magnetic field. 10 is a stator winding, which also functions as a transformer for a driving inverter circuit. Reference numerals 11 and 12 are base bias and feedback resistors of switching transistors for driving the inverter circuit. 13 and 1
3' is a driving switching transistor, 14 is an output shaft attached to the rotor, and 15 is a rotor made of a squirrel-cage-shaped secondary conductor and laminated electromagnetic steel plates.

The operation of the small electric motor configured as described above will be described below.

First, when the DC power supply voltage V is applied between the +V and GND terminals, the current flows from the stator winding 10.10' to the resistor 11.1.
1'→resistor 12, 12', the current flows to the left and right, and generates a base voltage in each of the two switching transistors 13, 13'.

Since this current increases over time due to the inductance of the stator winding 10.10', it causes the current to appear across the resistor 12.12' of the transistor 13.12'.
The same applies to the base voltage of transistor 13', and the transistor whose base voltage reaches the conduction level first (temporarily referred to as 13) becomes conductive, and the other transistor 13' becomes conductive.
Since the base of the transistor 13 is connected to the collector of the conductive transistor 13 via the resistor 11, the transistor 13 is kept in a cut-off state. Further, since the induced voltage generated between the stator windings 10 and 10' is applied in the forward direction to the base of the transistor 13 which is in the conductive state, the transistor 13 enters the conductive state more deeply.

Next, after a certain period of time, when the collector current of the transistor 13 that has become conductive reaches a certain value that is limited by the supplied base current, the collector current will no longer increase. When the collector current no longer increases, the stator winding 10
．． The induced voltage that had been generated between 10' and 10' becomes zero, and the base current decreases, and as a result, the collector current begins to decrease, and between stator winding 10 and 10', the base current decreases. An induced voltage is generated and the collector current further decreases.By applying feedback between the collector and the base in this way, the transistor 13, which has been in a conductive state until now, suddenly becomes cut off.

On the other hand, the transistor 13', which has been in a cut-off state until now, becomes conductive as the collector voltage of the transistor 13 increases, and the same phenomenon as when the transistor 13 becomes conductive occurs, increasing the collector current. Then, when the collector current reaches a certain value, it suddenly becomes cut off.

In this way, current flows alternately through the stator windings 10 and 10', and the magnetic fields generated thereby are connected so that their directions are opposite to each other, so that an alternating magnetic field is generated in the stator core 8. Supplied. A rotating magnetic field is generated by this alternating magnetic field and the corner control ring 9, and the rotor 4 is rotated by generating an induced current in the cage-shaped secondary conductor.

Figure 4 shows an example in which a synchronous motor is driven by a self-excited inverter, the rotor is a magnetic rotor, there is no corner control ring, and a wide gap 16 for starting is provided on the inner circumference of the stator. , the other configurations are the same as in FIG.

Problems to be Solved by the Invention However, with the above configuration, the efficiency is as low as 5% to 15% in the example shown in FIG. 3, and the efficiency is as low as 5% to 15% in the example shown in FIG. (Almost no starting torque (
, there were problems such as the direction of rotation was not determined.

In view of the above problems, the present invention has sufficient starting torque,
The purpose of the present invention is to provide, at low cost, a small-sized electric motor that has a stable rotational direction, high efficiency, and excellent controllability.

Means for Solving the Problems In order to solve the above problems, the small electric motor of the present invention has a structure in which the rotor is provided with both a squirrel-cage secondary conductor and a magnet.

According to the above-described structure, the present invention performs stable starting as an induction motor using the squirrel cage secondary conductor during startup, and operates as an efficient synchronous motor using the magnet during operation.

EXAMPLE Hereinafter, a small electric motor according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a rotor of a small electric motor according to a first embodiment of the present invention. (a) is a sectional view thereof, and (b) is a half sectional view. In Fig. 1, 1 is a composite rotor, 2
is a rotor core made of laminated electromagnetic steel sheets, 3 is a cage-shaped secondary conductor formed by aluminum die-casting, 4a is a magnet, 5 is a rotor yoke made of laminated electromagnetic steel sheets that serves as a path for the magnetic flux of the magnet, and 6 is a short-circuit for the magnetic flux of the magnet. The notch 7 is a protrusion on the rotor yoke provided for positioning the magnet. Squirrel cage secondary conductor 3. Magnet 4a, rotor yoke 5. Notch 6. A composite rotor 1 is constructed from the projections 7.

Regarding the small electric motor configured as above, the following is the first part.
The operation will be explained using FIG.

First, FIG. 2(a) shows the entire embodiment of the present invention, and the drive self-excited inverter and stator are the same as in the conventional example shown in FIG. Omitted. A rotating magnetic field having a frequency oscillated by a self-exciting inverter is applied to the composite rotor 1 . This rotating magnetic field generates an induced current in the cage-shaped secondary conductor 3, which generates torque in the direction of rotation of the magnetic field, and the rotor 1 starts rotating. The rotational speed of the rotor 1 increases and when it reaches a sufficient level, the rotor 1 starts to rotate synchronously due to the synchronous torque between the magnet 4 and the rotating magnetic field. The torque characteristic showing this state is shown in FIG. 2(b). In this state, the oscillation frequency of the inverter changes accordingly to a certain degree of load, allowing stable and efficient operation.

Effects of the Invention As described above, according to the present invention, since the rotor is equipped with both a squirrel-cage secondary conductor and a magnet, it has stable starting characteristics and efficient operating characteristics, and has a simple configuration and a long life. A small electric motor with excellent lifespan and controllability can be provided.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are cross-sectional views of the rotor of a small electric motor according to the first embodiment of the present invention, and FIGS. 2(a) and 2(b) are
(b) shows the overall diagram of Fig. 1, the drive circuit diagram, and the torque characteristic diagram, Fig. 3 shows the circuit configuration diagram of a conventional small electric motor, and Fig. 4 (a)
) is a circuit configuration diagram of a conventional small electric motor, and (b) is its characteristic diagram. 1...Composite rotor, 2...Rotor core, 3...Secondary conductor, 4, 4a...Magnet, 5...・Rotor yoke, 6...
・Rotor core notch, 7... Rotor yoke protrusion,
8... Stator core, 9... Shaded wire ring,
10... Stator winding, 11.12...
Resistor, 13...Switching transistor,
14...Output shaft, 15...Induction rotor, 16...Stator inner periphery notch. Fig. F Leq Special r11 Rotating bed (r pm) Fig.

Claims (1)

[Claims] In a motor having a stator with a shaded wire ring and a self-excited oscillation type inverter circuit, the transformer portion of the inverter circuit is also used as the stator winding and stator core of the shaded type motor. A small electric motor with a rotor having a secondary conductor, a magnet, and a laminated core made of magnetic steel strip.