JPH076702Y2 - Electric motor - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to a DC brushless motor, and more particularly to a motor used for a blower, a compressor or the like that requires a large torque temporarily at the time of start-up or high load. is there.

(B) Conventional technology In general, a DC brushless motor is generally configured to detect the rotational position of the rotor with position detecting means and control the energization of the stator winding based on this rotational position. there were. Since the permanent magnet is used for the rotor in the structure thus configured, the output and efficiency of the motor are greatly influenced by the characteristics (magnetic flux density) of the permanent magnet. For example, in a small DC brushless motor of a certain size, in order to increase output and efficiency, rare earth cobalt or the like is used to form a permanent magnet of the rotor to increase the magnetic flux density, or the number of turns of the stator winding is increased. The motor output and efficiency were improved by increasing the rotating magnetic field generated by the stator windings. In this case, the rotor using rare earth cobalt was extremely expensive and could not be used for general purposes. Also, because a permanent magnet is used, this rotor's demagnetization measures,
In particular, it is necessary to design with sufficient margin in the operating vimance, taking into consideration the irreversible demagnetization at low temperature and the demagnetization that occurs in the stator winding at the time of starting and overloading. It was impossible.

Further, since the rotor is generally formed by adhering a plurality of permanent magnets, when the motor is rotated at high speed, the magnet may scatter, which is not suitable for high speed rotation.

In addition, when the number of windings of the stator winding is increased, the winding cannot be made thin due to the allowable energization amount of the winding, and the size of the motor needs to be designed large.

As described above, conventional DC brushless motors require the use of extremely expensive materials in order to improve output and efficiency without changing the size, and use conditions such as temperature, humidity, and rotation speed are limited. there were.

In order to solve such a problem, there is one as described in Japanese Patent Application No. 58-12202. What is described in this application is to provide a secondary winding connected to a rotor winding of a rotor in a DC brushless motor, and to induce electric power from the primary winding through the air gap in the secondary winding. The rotation of the motor was controlled by both the magnetic field from the stator windings of the brushless motor and the magnetic field from the stator windings.

(C) Problem to be Solved by the Invention In the conventional electric motor configured as described above, it was necessary to constantly energize the rotor winding of the rotor to magnetize the rotor. For this reason, it is necessary to energize the rotor winding even at light load, and if the induction rate of electric power between the primary winding and the secondary winding is poor, the operating efficiency of the entire motor, especially during light load operation It was inefficient.

In view of such a problem, the present invention provides an electric motor capable of preventing a decrease in efficiency under light load.

(D) Means for Solving the Problems The present invention has a rotor having a permanent magnet and a stator winding, and switches energization to the stator winding based on the rotational position of the rotor. In a DC brushless motor, a stator is provided with a first winding, and a periodic pulsed power in which the ratio of energized time and de-energized time is changed based on the size of a load driven by this motor. Is applied to the first winding, and the rotor is provided with a second winding provided at a position where AC power is induced by the application of the first winding and an AC induced in the second winding. It is provided with a rectifying element for rectifying electric power and a rotor winding wound so that output electric power from the rectifying element is energized to create a magnetic field having the same polarity as the permanent magnet.

(E) Action In the electric motor configured as described above, it is possible to stop the energization of the first winding and stop the induction of the electric power to the second winding when the load is light. That is, the energization of the rotor winding is stopped and the operation is performed using only the magnetic field of the permanent magnet of the rotor. When the load is heavy, the magnetic field from the permanent magnets and the magnetic field from the rotor windings can be used to perform high-power operation.

(F) Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a top view of the rotor as seen from the rotary shaft side, and FIG. 2 is a front view showing a state in which a second winding and its wiring are provided on the rotor. In these figures, reference numeral 1 is a rotary shaft, which is press-fitted into the rotor core 2. The rotor core 2 is formed by laminating a plurality of electric iron plates and crimping them. Reference numerals 3 and 4 are arcuate permanent magnets, which are attached to the outer circumference of the rotor core 2 with an adhesive. Reference numeral 5 denotes a non-magnetic (stainless steel or the like) metal cylinder, which is attached so as to cover the outer circumferences of the permanent magnets 3 and 4. Reference numerals 6 and 7 denote rotor windings, which are wound around the outer periphery of the rotor core 2, the gaps between the permanent magnets 3 and 4, and the space formed by the metal cylinder 5 while avoiding the rotating shaft 1. The metal cylinder 5 may not be provided when the rotor does not rotate at a high speed and the permanent magnets 3 and 4 are not separated by centrifugal force when the rotor rotates. At this time, it is necessary to shape the coil ends of the rotor windings 6 and 7 so that the coil ends do not come out from the outer circumferences of the permanent magnets 3 and 4. 8, 9 and 10 are three-phase (U-phase, V-phase, W-phase) stator windings that generate a rotating magnetic field in the inner circumference of the rotor insertion hole. 8, 9 and 10 are arranged so that the electrical angle is shifted by 120 degrees. 11,12,13 are position detectors (Hall IC, Hall element, magnetic diode, search coil, etc.)
Output appears in response to the magnetic fields of the permanent magnets 3 and 4 of the rotor,
The output is used to determine the rotational position of the rotor. Energization of the stator windings 8, 9 and 10 is controlled by the control circuit shown in FIG. 3 (described later). That is, the position detector
The energizing direction of the stator windings 8, 9 and 10 and the combination thereof are sequentially changed so that the rotor continuously rotates based on the outputs of 11, 12, and 13. Incidentally, as the energization switching method of such a stator winding, a generally used method can be used, and thus detailed description thereof will be omitted. In addition, the change of the induced voltage generated in the stator windings 8, 9 and 10 may be used for this energization switching without using the position detectors 11, 12 and 13. Reference numeral 14 shown in FIG. 2 is a ferrite bobbin, which is inserted in the rotary shaft 1
The winding 15 is wound. Further, 16 is a ferrite core, around which the first winding 17 is wound. Bobbin 14 and core
16 has a small air gap, and when the first winding 17 is turned ON / OFF, electric power is induced in the second winding.

FIG. 3 is a main part electric circuit diagram showing the main parts of the stator windings 8, 9, 10 and the rotor windings 6, 7 and the control circuit. In this figure, 18 is a control circuit (microcomputer), which is mainly a stator winding
Controls energization of 8, 9, 10 and rotor windings 6, 7. An inverter circuit 19 connects six switching elements (transistors, FETs, etc.) in a three-phase bridge shape, and the stator windings 8, 9 and 10 are connected to the output of this bridge.
The switching element of the inverter circuit is
It operates in response to an ON / OFF signal and controls energization of the stator windings 8, 9 and 10 so that a rotating magnetic field is obtained. The microcomputer 18
Is to generate and output an ON / OFF signal based on the rotational position of the rotor detected by the position detecting elements 11, 12, and 13. 2
Reference numerals 0 and 21 respectively denote a rectifying element and a smoothing capacitor, which rectify and smooth the electric power of the AC power supply 22 and then supply it to the inverter circuit 19. 23 is a current detector (current transformer, etc.),
The amount of current supplied from the AC power supply 22 (substantially equal to the amount of current flowing through the stator windings 8, 9, 10) is detected. The detected value of the current detector 23 is converted into an analog voltage by the converter 24 and then given to the microcomputer 18. 25 is a PWM controller (a controller that controls the ON time in one cycle), and controls the ON time in one cycle from 0 (all OFF) to 50% based on the signal given from the terminal S of the microcomputer 18. To do. still,
This ON / OFF cycle is repeated at approximately 20 KHz (10 KHz to 100 KHz is suitable). Therefore, the ferrite material of the bobbin 14 and the ferrite material of the core 16 shown in FIG.
High frequency characteristics that do not saturate even above are required. (Soft ferrite etc.), 26 is a switching element (transistor, FET etc.), ON / OFF is controlled by the output signal of the PWM controller 25. This switching element 26 is ON / O
The energization of the first winding 17 is controlled by the FF operation. Reference numeral 27 denotes a diode, which discharges the electric charge accumulated in the switching element 26.

Numerals 28 and 29 are diodes connected between the second winding 15 and the rotor windings 6 and 7, respectively, for rectification and discharging the electric charge remaining in the rotor windings 6 and 7. The rotor windings 6 and 7 are connected in series (may be parallel), and when the electric power induced in the first winding 15 is rectified by the diode 28 and flows, the polarity of the magnetic field is the permanent magnets 3 and 4 of the rotor. It is wound to match the polarity of. For example, in FIG. 1, the outer circumference of the permanent magnet 3 is N
When the outer circumference of the pole and the permanent magnet 4 is the S pole, the A side of the stator core is the N pole and B when the current flows in the direction of the solid arrow in FIG.
The rotor windings 6 and 7 are wound so that the side becomes the S pole.

In the motor configured as above, the stator windings 8, 9, 10
Is sequentially switched on the basis of the rotational position of the rotor to generate a continuous rotating magnetic field to continuously rotate the rotor. At this time, a signal is output from the terminal S of the microcomputer 18 to the PWM controller 25 to turn on / off the switching element 26.
Then, electric power is induced in the second winding 15. This induced power is rectified by the diode 28 and then applied to the rotor windings 6 and 7. Therefore, the magnetic field generated by the rotor windings 6 and 7 and the magnetic field of the permanent magnets 3 and 4 are combined to increase the output of the electric motor. That is, the state is substantially the same as when the permanent magnet is magnetized. This amount of increase in magnetism is increased by increasing the ON / OFF ratio of the PWM controller 25, and decreased by decreasing it.

For example, when such an electric motor is used as a motor for a refrigerant compressor, the rotor is magnetized at the time of starting the compressor to improve the starting characteristics, and the rotation efficiency is improved for each rotation speed. Adjust the amount of magnetization of the child. When the current detected by the current detector 23 is large (when the motor is overloaded), the rotor is magnetized, and when the current is small (light load), the rotor is demagnetized (permanently). When operated only with the magnetic flux of the magnets 3 and 4, the SEER of the refrigerator (such as an air conditioner) equipped with this compressor is also improved, and the efficiency of the entire device is improved.

(G) Effect of the Invention The present invention has a rotor having a permanent magnet and a stator winding, and switches the energization to the stator winding based on the rotational position of the rotor, which is a DC brushless motor. At
The stator is provided with a first winding, and a periodic pulsed power whose ratio of energized time and de-energized time is changed based on the size of a load driven by this motor is applied to this first winding. A second winding, which is energized and is provided at a position where AC power is induced by energization of the first winding, and a rectifying element that rectifies the AC power induced in the second winding, are provided in the rotor. Since the rotor winding is wound so that the output power from the rectifying element is energized to form a magnetic field having the same polarity as the permanent magnet, an increase in the magnetism generated in the rotor based on the size of the load. You can change the amount. That is, when the load is large or when a large output is required, the output of this motor increases because the permanent magnet of the rotor is magnetized, and when the load is light, a small output operation is performed only by the permanent magnet, and Since the operation is performed according to the magnitude of the load, the operating efficiency of the electric motor is improved.

[Brief description of drawings]

FIG. 1 is a top view of the rotor as seen from the side of the rotary shaft, FIG. 2 is a front view of the rotor shown in FIG. 1 with a second winding wound, and FIG. 3 is a stator winding. It is a control circuit diagram which controls the electricity supply to a wire and a rotor winding. 1 ... Rotary axis, 2 ... Rotor core, 3,4 ... Permanent magnet,
6,7 …… Rotor winding, 8,9,10 …… Stator winding, 15 …… Second winding, 17 …… First winding.

Claims (2)

[Scope of utility model registration request] 1. A DC brushless type electric motor comprising a rotor having a permanent magnet and a stator winding, wherein energization of the stator winding is switched based on a rotational position of the rotor. Is provided with a first winding, and the periodic pulsed power whose ratio of energization time and non-energization time is changed based on the size of the load driven by this motor is energized to this first winding. At the same time, the rotor has a second winding provided at a position where AC power is induced by energization of the first winding, a rectifying element for rectifying the AC power induced in the second winding, and An electric motor, comprising: a rotor winding wound so that an output power from a rectifying element is energized to create a magnetic field having the same polarity as the permanent magnet. 2. The electric motor according to claim (1), characterized in that the electric motor is provided with a control unit for cutting off the energization to the first winding when the load of the electric motor is light.