JPH0628915Y2 - Brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a brushless motor, and more particularly to overheat protection thereof.

[Prior Art] A rotational position detection element such as a Hall element detects a change in a magnetic field due to rotation of a rotor magnet, and a detection signal from the rotation position detection element sequentially turns on transistors connected in series to a plurality of stator coils. Therefore, in the so-called brushless motor that switches and supplies the energizing current to the coils to rotate the rotor magnet, as a protection when the rotation of the rotor magnet is locked for some reason, conventionally, For example, as disclosed in Japanese Utility Model Laid-Open No. 60-198885, a thermosensitive resistance element is inserted in series with a stator coil to detect an abnormal temperature rise of the stator coil when the rotor is locked, and to detect a coil passing current. It was common to limit

[Problems to be Solved by the Invention] As described above, in the conventional brushless motor, since the heat sensitive resistance is connected in series to the stator coil for overheat protection by the rotor lock, current always flows through this heat sensitive resistance. The efficiency of the motor decreases due to the unnecessary power consumption and the voltage drop to the stator coil due to the voltage drop.
Even if the rotor remains locked, the coil current will not be interrupted unless the stator coil overheats, so current may flow only to the transistor in series with the specific coil, which may damage the transistor. There was a point.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain a brushless motor capable of efficiently performing effective overheat protection.

[Means for Solving Problems] A brushless motor according to the present invention comprises a rotation detection circuit for detecting a rotation speed of a rotor magnet which is equal to or lower than a predetermined value, and a stator coil series transistor according to a low rotation speed detection by this circuit. A switch circuit for turning off the application of the ON drive signal to the
A restart timer circuit that resets the rotation detection circuit after a predetermined time from the low rotation speed detection by the rotation detection circuit and turns on the switch circuit, and is arranged in proximity to each of the stator coil series transistors. It is provided with a temperature sensor for detecting the temperature and an overheat protection circuit for turning off the switch circuit when the detected temperature of any of the temperature sensors is a predetermined value or more.

[Operation] In the present invention, when the rotation of the rotor magnet is locked, the rotation detection circuit detects this, turns off the switch circuit, and shuts off the ON drive signal to the stator coil series transistor, thereby fixing the stator. The energizing current to the coil is cut off.
On the other hand, after a lapse of a predetermined time from the detection of the rotor lock of the rotation detection circuit, the rotation detection circuit is reset by the signal from the restart timer circuit and the switch circuit is turned on to re-energize the stator coil. At this time, if the locked state is released, the motor starts normal operation, but if the locked state continues, the above operation is repeated.

If such repetitive operation is continued for too long, the stator coil series transistor becomes overheated, and this is detected by the overheat protection circuit by the temperature signal from the temperature sensor arranged close to each transistor. The switch circuit is turned off, the transistor drive signal is turned off, and the energizing current to the stator coil is cut off. In this way, the rotor lock is quickly detected to shut off the stator coil energizing current, and the transistor is automatically restarted until it overheats, and the overheat protection operation is extremely effective. It is performed with high efficiency without wasteful power consumption.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. The figure is a circuit diagram showing an embodiment of the present invention. In the figure, (1) is arranged near the magnetic pole surface of a rotor magnet (not shown) magnetized with a plurality of magnetic poles in the circumferential direction, A Hall element that outputs a positive signal when the adjacent rotor magnetic poles are N poles, for example, a positive signal when the rotor magnetic poles are S poles, (2) is an amplifier that amplifies the detection AC signal due to the rotation of the magnet from this Hall element (1), (3) is this amplifier (2)
Waveform shaping circuit that converts the AC signal from the device into a rectangular wave, (4)
Is a switch circuit that is a buffer amplifier that amplifies or blocks the signal from this circuit (3), (5) is an inverter, and (6a) (6
b) is a two-phase stator coil, (7a) and (7b) are transistors, and (8
a) (8b) is a temperature sensor arranged near these transistors (7a) and (7b), and (9) is a rotation detection circuit for detecting a rotation speed of the rotor magnet or less, which is L in the reset state. (Low)
Is output, and when the number of pulses from the waveform shaping circuit (3) within a fixed time is less than or equal to a predetermined value, H (High) is output,
The set state is maintained until the power is turned off or the reset pulse is applied. (10) is a restart timer circuit, which is reset by the rise of the H output from the rotation detection circuit (9), and is set after the elapse of a predetermined time, and the rotation detection circuit is set.
Output a reset pulse to (9). Reference numeral (11) is an overheat protection circuit, which outputs an H signal when the temperature signals detected by the temperature sensors (8a) and (8b) from the OR element (12) exceed a predetermined value. (13) is an OR element, which outputs H and turns off the switch circuit (4) when either the rotation detection circuit (9) or the overheat protection circuit (11) outputs H. Note that R ₁ is a resistor, D ₁ is a diode, and Vcc is a DC power source.

Next, the operation of the above circuit will be described. During normal operation, the Hall element (1) detects an AC signal with a frequency proportional to the rotation speed of the rotor according to the rotation of the rotor magnetic pole, is amplified by the amplifier (2), and is square-wave pulsed by the waveform shaping circuit. Is converted to and applied to the switch circuit (4). During normal operation, both the rotation detection circuit (9) and the overheat protection circuit (11) are in the reset state and both are L outputs, so the switch circuit (4) is in the ON state and the rectangular wave pulse from the circuit (3) Is the transistor whose polarity is inverted by the transistor (7a) and the inverter (5).
Applied to the base of (7b), these transistors (7a) (7b)
Is alternately turned on, and the energizing currents are alternately switched and supplied to the two-phase stator coils (6a) and (6b). In this way, the rotation of the DC two-phase brushless motor is maintained.

Next, suppose that the rotation of the rotor magnet is locked for some reason. At this time, the rotation speed decreases, so the rotation detection circuit (9)
Is set and its H output is applied to the switch circuit (4) through the OR element (13) to turn it off. Therefore, the rectangular wave pulse from the waveform shaping circuit (3) is cut off, the drive signal is not applied to any base of the transistors (7a) and (7b), and it turns off, and the stator coils (6a) and (6b) are heated. The current is cut off. On the other hand, the restart timer circuit (10) is reset by the rise of the H output of the rotation detection circuit (9), and is set after a certain period of time, the rotation detection circuit (9) is reset by the output pulse of the restart timer circuit (10), and the switch circuit (4) Turn on as stator coil again
(6a) Energize (6b) to restart the motor. If the locked state is released within the fixed time until this restart, then normal operation starts, and if the locked state is not released, the above operation is repeated and the stator coils (6a) (6b) The energization interruption of is repeated. The normal rotor lock failure is released by the above several restarts, and the stator coils (6a) (6b),
This prevents the transistors (7a) and (7b) from overheating, but if the lock state is still not released, the transistors (7a) and (7b) will overheat, and the temperature sensor
The overheat protection circuit (11) is detected by the temperature signals from (8a) and (8b) and set, and outputs an H signal to apply to the switch circuit (4) via the OR element (13) to turn it off. To do. As a result, the drive signal to the transistors (7a) and (7b) is cut off, and both of these transistors are turned off.

Although the example of the brushless motor having a two-phase coil is shown in the above-described embodiments, it goes without saying that a brushless motor having a three-phase coil may be used.

[Effect of the Invention] Since the brushless motor of the present invention is configured as described above, it has the effect of being able to effectively perform complete overheat protection without wasted power consumption and voltage drop.

[Brief description of drawings]

The figure is a circuit diagram showing an embodiment of the present invention.
(1) Hall element, (4) switch circuit, (6a) (6b) stator coil, (7a) (7b) transistor, (8a) (8b) temperature sensor, (9) rotation detection Circuit, (10) is a restart timer circuit, and (11) is an overheat protection circuit.

Continuation of front page (56) References JP-A-48-38420 (JP, A) JP-A-51-55940 (JP, A) JP-A-52-54146 (JP, A) JP-A-58-51793 (JP , A) JP 61-189187 (JP, A) Actually opened 61-108084 (JP, U) Actually opened 62-168743 (JP, U) Actually opened 62-178799 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A brushless motor for detecting rotation of a rotor magnet and sequentially turning on a transistor connected in series to each of a plurality of stator coils to switch and supply an energizing current to them. , A rotation detection circuit for detecting a rotation speed of the rotor magnet below a predetermined value, a switch circuit for turning off the signal application for turning on the transistor in response to detection of a low rotation speed by this circuit, and a rotation detection circuit for lowering the rotation speed. A restart timer circuit that resets the rotation detection circuit and turns on the switch circuit after a predetermined time from the detection of the number of revolutions, a temperature which is arranged near the transistor connected to the stator coil and detects the temperature of the transistor. A sensor and an overheat protection circuit that turns off the switch circuit when the detected temperature of any of these temperature sensors is equal to or higher than a predetermined value. Brushless motor according to symptoms.