JPH0488860A - Brushless motor - Google Patents

Abstract

PURPOSE:To decrease the effect of the dispersion of BW of a magnetic sensor by equipping it with a start control circuit which turns on a switching element for a certain time at power on, and turns off it for a certain time after that, and further becomes independent of the control of the switching element after that until power off. CONSTITUTION:A start control circuit 18 turns on or turns off a switching element 19, and controls a switching element 11, and also turns on or turns off a switching element 20 to control the operation of a magnetic sensor 7. By this circuit, by turning on the switching element 11 for a certain time, the brake works on the rotor 2, even if it is in rotating condition beforehand, by the attraction of a coil 5, and it stops. By the switching element 11 becoming off then for a certain time, the attraction of the coil vanishes, and the rotor inverts by the repulsion of the magnet 6 for initial positioning of the rotor, and stops at the balanced point. Further, thereafter, power is applied so that it may do usual operation. Hereby, the effect of the dispersion of BW of the magnetic sensor can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a brushless motor for controlling rotation of a vehicle motor.

BACKGROUND OF THE INVENTION Conventionally, this type of brushless motor has been constructed as shown in FIGS. 4 to 6. Note that FIGS. 4 and 5 are diagrams showing the arrangement of parts of a conventional brushless motor.
FIG. 6 is a block circuit diagram of the brushless motor. In the figure, 1 is a case consisting of a lower case IA and an upper case IB, and a rotor 2 is rotatably supported in the case 1. Furthermore, permanent magnets 3.4 are attached to the lower part of the rotor 2 at symmetrical positions with respect to the center. Reference numeral 5 denotes a coil attached to the lower case IA. When this coil 5 is energized, a magnetic field generated attracts the permanent magnets 3 and 4, causing the rotor 2 to rotate. 6 is a magnet for positioning the rotor 2 at the initial position between the permanent magnets 3 and 4, and is disposed in the lower case IA, and when the power is off, the magnet for positioning the rotor 2 at the initial position. Since the polarities of the permanent magnets 6 and the permanent magnets 3 and 4 are the same, they repel each other, and the rotor 2 is stopped at a balanced position. 7
is a magnetic sensor such as a Hall element, which is mounted on a board 9 together with other electronic components 8, and is disposed in the lower case IA. In addition, this magnetic sensor 7 is connected to the rotor 2 in the initial state.
It is placed at a position where it is affected by the permanent magnet 3°4. Further, the board 9 on which this component is mounted is covered with a resin 10 after being placed on the lower case IA. Further, in FIG. 6, a switching element 11 such as a transistor is inserted and connected between the coil 5 and the power source.

The output terminal of the magnetic sensor 7 is connected to the switching element 11 via a current limiting element 12 such as a resistor.

That is, the magnetic sensor 7 detects the positions of the permanent magnets 3 and 4, and the switching element 11 that controls the energization of the coil 5 is switched based on the signal from the magnetic sensor 7.

In addition, in FIG. 6, 13 is a constant voltage diode, and 14 is a constant voltage diode.
is resistance.

In such a configuration, when the permanent magnet 3 is located on the magnetic sensor 7, the output of the magnetic sensor 7 is turned on, the switching element 11 is turned on, and the coil 5 is turned on.
A current flows through the magnet, generating torque to attract the permanent magnet 4, and the rotor 2 rotates. When the permanent magnet 4 moves close to the top of the coil 5, the permanent magnet 3 moves from above the magnetic sensor 7, so the output of the magnetic sensor 7 turns off, the switching element 11 turns off, and current flows to the coil 5. stops flowing, the attractive force between the permanent magnet 4 and the coil 5 is lost, and the rotor 2 continues to rotate due to inertia.After that, the permanent magnets 3 and 4 continue to move in the same way as described above, with the opposite state. .

Here, a force that resists the movement of the rotor 2 to continue rotating due to inertia exists as a repulsive force between the magnet 6 for initial positioning of the rotor 2 and the permanent magnets 3 and 4 of the rotor 2, and The magnetic sensor 7 has a hysteresis width (hereinafter referred to as BW) between the detection level from detection off to on (hereinafter referred to as BH-L) and the detection level from detection on to off (hereinafter referred to as BL-H). , if the rotor 2 loses the attractive force of the coil 5 at BL-H and then succumbs to the repulsive force of the magnet 6 for initial positioning of the rotor 2 and rotates in the opposite direction, the rotor 2 is at BH.
-L, the magnet 6 for initial positioning of the rotor 2 is rotated again using the attractive force of the coil 5, and after repeating several times, the acceleration obtained between BH-L and BL-H It means overcoming and overcoming the repulsive force.

Problems to be Solved by the Invention However, with such conventional brushless motors, there was a problem in that under the worst conditions (when the BW was narrow) the motor could not rotate due to variations in the BW of the magnetic sensor. .

Furthermore, current technology has a limit in suppressing variations in BW of magnetic sensors, and it has not been possible to solve the problem.

Furthermore, in very rare cases, the permanent magnets 3 or 4 of the rotor 2 may maintain balance and stop right above the magnet 6 for initial positioning of the rotor 2, resulting in a problem that the rotor cannot be started.

In addition, starting problems occur in the case of small brushless motors where methods such as installing a starting coil or starting by detecting the rotating state of the rotor using a stator winding that forms a rotating magnetic field are not possible. This was a problem that was difficult to solve.

In view of the current situation, it is an object of the present invention to provide a brushless motor that is not affected by variations in BW of magnetic sensors and that can be started reliably.

Means for Solving the Problems In order to solve these problems, the present invention provides a rotor having permanent magnets, a coil for rotating this rotor, and a rotor that is inserted and connected between this coil and a power source. a switching element; a magnetic sensor that detects the position of the permanent magnet of the rotor and controls switching of the switching element; and independent of the control of the magnetic sensor, the switching element is made conductive for a certain period of time when the power is turned on, and then the switching element is made conductive for a certain period of time, and then The device is equipped with a start-up control circuit that causes the device to be non-conductive for a period of time, and thereafter becomes unrelated to the control of the switching device until the power is turned off.

Operation This configuration ensures that if power is applied while the rotor is reversing between the point at which the coil loses attraction at BL-H and the rotor's initial positioning magnet, the rotor's permanent magnets will In either case, when the power is turned on while the rotor is stopped directly above the initial positioning magnet, the rotor is first set to a rotating state by conducting the switching element for a certain period of time (approximately 10 seconds). Even if there is, the coil's attractive force will apply the brakes and bring it to a complete stop.Then, the switching element will become non-conductive for a certain period of time (approximately 2 seconds), and the coil's attractive force will disappear, and the rotor will move to the rotor's initial positioning magnet. It reverses itself due to the repulsive force of , and comes to a complete stop at the equilibrium point.

Furthermore, after that, power is applied to enable normal operation, so it becomes possible to eliminate the influence of variations in the BW of the magnetic sensor, and it becomes possible to start up reliably.

EXAMPLE Hereinafter, an example of the present invention will be explained using the drawings of FIGS. 1 to 3.

FIG. 1 shows a block circuit of a brushless motor according to an embodiment of the present invention, FIG. 2 shows a diagram explaining the operating principle of the motor, and FIG. 3 shows a specific circuit. In FIGS. 4 to 3, the same parts as those of the conventional motor shown in FIGS. 4 to 6 are designated by the same numbers. In the figure, reference numeral 18 denotes a starting control circuit, which controls the switching element 11 by turning on and off the switching element 19, and also controls the operation of the magnetic sensor by turning on and off the switching element 20. This control circuit 18 is
Comparator ICI as shown in FIG.

IC2 and diodes DI-1, D2-2.11°D3
-2, resistors R1 to R8, and capacitors C2 and C3. In this Figure 3, when power is applied, capacitor C2 is connected to resistor R6 and diode D3-1.
A charging current flows through the resistor R7 and the voltage across the capacitor C2 gradually rises. Comparator ICI, IC
A reference voltage determined by the voltage division ratio of the resistors R3 and R4 is applied to each terminal of the comparator IC2, and one terminal of each of the comparators ICI and IC2 rises together with the voltage across the capacitor C2. When the reference voltage is exceeded, the output terminal of the comparator IC2 changes from high level to low level. At this time, the switching elements 19 and 20 change from on to off. When the switching element 19 is on, the switching element 11 is turned on because a drive current flows through the current limiting element 12, and is forced on regardless of the magnetic sensor 7. Furthermore, when the switching elements 19 and 20 are off, they are forced off regardless of the magnetic sensor 7. Therefore, after power is applied, the switching element 11 is forcibly turned on until one terminal of the comparator TC2 exceeds the reference voltage, and when one terminal of the comparator IC2 exceeds the reference voltage, the switching element 11 is forcibly turned off. When the capacitor C2 is further charged and one terminal of the comparator ICI exceeds the reference voltage, the output terminal of the comparator ICI changes from high level to low level. At this time, a voltage is applied to one terminal of the comparator IC2 at the voltage division ratio of the resistors R5 and R6, and since this voltage value is set in advance to be smaller than the reference voltage value, the output of the comparator IC2 is The terminal changes from low level to high level. At this time, the switching element 20 changes from off to on, and the switching element 19 changes from the diode D3-
It stays off because it goes to a low level through 1. Therefore, the switching element 11 is released from the forced on/off state and performs an operation consistent with the on/off state of the magnetic sensor 7. In FIG. 3, the constant voltage diode 13 is connected for stable operation of the control circuit 18, and power is applied through the resistor 15. The diodes 16 and 17 are connected for surge resistance of the magnetic sensor 7, and the surge protection circuit 21 protects circuits other than the switching element 11. The resistor 14 is connected to a power supply line for driving the magnetic sensor 7 for current limitation. C4
, C5 is a transistor, Dl is a diode, RO, R9
, R.I.O.

R11 is a resistor, and C1, C, and 3 are capacitors.

With this configuration, as shown in FIG. 2, when the permanent magnet 4 is located on the magnetic sensor 7, the output of the magnetic sensor 7 is turned on, and the switching element 1 is turned on.
1 is turned on, current flows through the coil 5, a torque is generated to attract the permanent magnet 3, and the rotor 2 rotates. When the permanent magnet 3 moves close to the top of the coil 5, the permanent magnet 4 moves from above the magnetic sensor 7.
The output of is turned off, the switching element 11 is turned off, current no longer flows through the coil 5, the attraction between the permanent magnet 4 and the coil 5 disappears, and the rotor 2 continues to rotate by inertia.

Thereafter, the permanent magnets 3 and 4 continue to move in the same manner as described above in opposite states.

Here, a force that resists the movement of the rotor 2 to continue rotating due to inertia exists as a repulsive force between the magnet 6 for initial positioning of the rotor 2 and the permanent magnets 3 and 4 of the rotor 2. 2
There is a risk that the permanent magnet 3 or 4 of the rotor 2 will stop directly above the magnet 6 for initial positioning of the rotor 2. However, in this embodiment, when the power is applied, the switching element 11 is held for a certain period of time (approximately 10 seconds> Since it is forcibly turned on, if the permanent magnet 3 or 4 of the rotor 2 is stopped directly above the magnet 6 for initial positioning of the rotor 2, or if the rotor 2 is Even when the rotor 2 is rotating in the opposite direction due to repulsive force, the permanent magnet 3 or 4 of the rotor 2 is attracted by the attractive force of the coil 5, and the rotor 2 stops with the magnet 3 or 4 of the rotor 2 directly above the coil 5. After that, the switching element 11
is forcibly turned off for a certain period of time (approximately 2 seconds), the rotor 2 rotates in the opposite direction due to the repulsive force of the initial positioning magnet 6 of the rotor 2, and the permanent magnet of the rotor 2 or 4 is directly above the magnetic sensor 7. Stop. If the switching element 11 starts to rotate under the control of the magnetic sensor 7 while the rotor 2 is stopped at the initial position, the magnetic sensor 7 is turned on when the rotor 2 is at the initial position. When the rotor 2 rotates and the magnetic sensor 7 detects it from ON to OFF, the rotor 2
Sufficient rotational torque is obtained, and the rotor 2 can continue to rotate by overcoming the repulsive force of the initial positioning magnet 6.

Effects of the Invention As described above, according to the present invention, since the rotor can start rotating from the initial position after power is applied, the rotor can be rotated without succumbing to the repulsive force of the magnet for initial positioning of the rotor. Therefore, it is possible to provide a brushless motor that is not affected by variations in the BW of the magnetic sensor.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a brushless motor according to an embodiment of the present invention, FIG. 2 is an explanatory diagram explaining the operating principle of the motor, FIG. 3 is a circuit diagram showing a specific circuit of the motor, and FIG. 4 and 5 are a sectional view and an exploded perspective view showing the arrangement of parts of a conventional brushless motor, and FIG. 6 is a block circuit diagram of the motor. 1...Rotor, 3.4...Permanent magnet,
5... Coil, 6... Magnet, 7...
...Magnetic sensor, 11°19.20...Switching element, 12...Current limiting element, 18.
...Start control circuit. Name of agent: Patent attorney Shigehi Awano and one other person 1st Ward Atsushi Figure 1 Case 70 Case 1b Figure 5 1A, lower case

Claims (1)

[Claims] A rotor having a permanent magnet, a coil for rotating this rotor, a switching element inserted and connected between this coil and a power supply, and a switching element that detects the position of the permanent magnet of the rotor and switches the switching element. and a magnetic sensor that controls the magnetic sensor, and independently of the control of the magnetic sensor, the switching element is made conductive for a certain period of time when the power is turned on, and thereafter is made non-conductive for a certain period of time, and thereafter becomes unrelated to the control of the switching element until the power is turned off. A brushless motor equipped with a starting control circuit.