JPH0336237Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention has a stator coil set to two or more phases and a rotor magnetic pole made of a permanent magnet, and energizes the stator coil based on the rotational position of the rotor. The present invention relates to a brushless motor that is controlled to selectively rotate a rotor in a forward direction and a reverse direction.

[Technical background of the invention]

For example, in a video tape recorder equipped with two reel motors consisting of brushless motors,
It is necessary to keep one of the reel motors in a locked state when loading and unloading the magnetic tape. For this reason, in the past, the reel motor was kept in a locked state by a mechanical locking means.

[Problems with background technology]

However, the mechanical locking means described above requires a large number of parts such as a locking member for applying mechanical braking force to the reel motor, an electromagnetic solenoid for driving this locking member, and a control circuit for this electromagnetic solenoid. There is a problem with high
Another problem was that reliability decreased as the structure became more complex.

[Purpose of invention]

The present invention was devised in view of the above circumstances, and its purpose is to obtain the function of keeping the rotor in a locked state with an extremely simple structure.
Therefore, it is an object of the present invention to provide a brushless motor that can reduce costs by reducing the number of parts and improve reliability.

[Summary of the idea]

The present invention provides a brushless motor configured to selectively rotate a rotor in a forward direction and a reverse direction, which is arranged to face the rotation locus of the rotor and periodically rotates as the rotor is rotated. a position detection element that outputs a position detection signal whose polarity is inverted;
and a signal generation circuit that outputs a rectangular pulse signal only during the period when the position detection signal is in one polarity, and when a lock state maintenance command is given from the outside, the output of the rectangular pulse signal is A switching circuit is provided to alternately generate torque in the forward and reverse directions between the stator coil and the rotor magnetic poles by switching the current direction of the stator coil when the stator coil is stopped. The rotor is electrically held in a locked state.

[Example of idea]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic layout of a three-phase eight-pole brushless motor applied in this embodiment. In this FIG. 1, 1 is an outer type rotor,
This rotor 1 has a structure in which permanent magnets 4 having eight rotor magnetic poles 3A to 3h at equal pitches are fixed to the inner peripheral surface of a cylindrical rotor yoke 2. 5 is a stator, and this stator 5 has a structure in which first phase stator coils 7a, 7a', second phase stator coils 7b, 7b', and third phase stator coils 7c, 7c' are arranged in a ring around a stator core 6. be. Further, 8, 9, and 10 are magnetic sensors made of Hall elements arranged so as to face the rotation locus of the rotor magnetic poles 3a to 3h, and these detect the rotational position of the rotor 1 based on the magnetic flux from the rotor magnetic poles 3a to 3h. Outputs position detection signals Sa, Sb, and Sc according to the
In this embodiment, the magnetic sensor 10 is also used as a position detection element according to the present invention.

FIG. 2 shows the electrical configuration of this embodiment, which will be described below. That is, Q ₁ to Q ₅
is a transistor, and a series circuit of transistors Q ₁ and Q ₆ , a series circuit of transistors Q ₂ and Q ₄ , and a series circuit of transistors Q ₃ and Q ₅ are connected between the DC power supply terminal +V and the ground terminal, respectively. . Also,
The stator coils 7a, 7a', 7b, 7b', 7
The transistors c and 7c' are connected in a star shape in which those having the same phase are connected in series, and are connected to the transistors Q ₁ to Q ₆ as shown in the figure. 11 is for example
A control circuit consisting of an IC, which controls transistors Q ₁ to Q ₅ based on the position detection signals Sa, Sb, and Sc.
Two of them are turned on in a predetermined order, thereby driving the stator coils 7a to 7c' in a so-called two-phase full-wave energization system.
In this case, the control circuit 11 has its select terminal S
When receiving a high level signal, the rotor magnetic poles 3a to 3h and the stator coils 7a to 7
Transistors Q ₁ to Q ₆ are turned on so that a positive torque is generated between the select terminal S and the select terminal S receives a low level signal.
so that the current direction of the stator coils 7a to 7c' is opposite to that when the positive torque is generated as described above.
In other words, the transistors _Q1 to _Q6 are turned on so that torque in the opposite direction is generated between the rotor magnetic poles 3a to 3h and the stator coils 7a to 7c'. The rotor 1 can be selectively rotated in a forward direction or a reverse direction depending on an input. on the other hand,
Reference numeral 12 denotes a comparator as a signal generating circuit, and this is provided so that the position detection signal Sc from the magnetic sensor 10 is applied between its non-inverting input terminal (+) and inverting input terminal (-). In this case, as shown in FIG. 3a, the polarity of the position detection signal Sc is periodically reversed each time rotor magnetic poles 3a to 3h of different polarity are opposed to the magnetic sensor 10 as the rotor 1 rotates. At this time, since the rotor magnetic poles 3a to 3h are at equal pitches, the comparator 12
A rectangular pulse signal Sp with a duty ratio of 50% as shown in FIG. b is output. 13 is an NPN that constitutes the switching circuit 14 together with the control circuit 11;
This transistor is configured to receive a rectangular pulse signal Sp from the comparator 12 at its base. The collector of the transistor 13 is connected to the select terminal S of the control circuit 11 via the lock switch 15, and the emitter is grounded. The locking switch 15 is turned on when an external command is received to keep the rotor 1 in a locked state. In addition, the select terminal S of the control circuit 11 is connected to the resistor 16.
Connected to the positive power supply terminal +Vcc via.

Next, the operation of the above configuration will be explained. The transistor 13 that receives the rectangular pulse signal Sp from the comparator 12 is turned on when the rectangular pulse signal Sp is at a high level and turned off when it is at a low level. Therefore, the locking switch 15 is turned on. In this state, a high level signal and a low level signal are alternately applied to the select terminal S of the control circuit 11.
Therefore, when the control circuit 11 receives a high level signal at its select terminal S (when the pulse signal Sp is output), the control circuit 11 generates a torque in the positive direction between the rotor magnetic poles 3a to 3h and the stator coils 7a to 7c'. Then, when a low level signal is received at the select terminal S (the output of the pulse signal Sp is stopped), a torque in the opposite direction is generated between the rotor magnetic poles 3a to 3h and the stator coils 7a to 7c'. That is, the fourth
If, for example, torque is generated in the direction of arrow A in a state where the N-pole rotor magnetic poles 3a, 3c, 3e, and 3g are opposed to the magnetic sensor 10 as shown in FIG. As shown in the figure, when the S-pole rotor magnetic poles 3h, 3d, 3f, 3h are opposed to the magnetic sensor 10, torque in the direction of arrow B is generated, and such torques in different directions are generated. When the state in which these occur alternately is repeated, a state as shown in FIG.
The rotor 1 is locked in a state in which the magnetic neutral points between the two rotors are opposed to each other, and this locked state is maintained until the locking switch 15 is turned off.

In the above embodiment, the rectangular pulse signal Sp is obtained based on the position detection signal Sc from the magnetic sensor 10, but it is needless to say that the present invention is not limited to this. Further, in the above embodiment, a 3-phase 8-pole brushless motor was described as an example, but the present invention is not based on this.
The present invention can also be applied to phase or multiphase brushless motors.

[Effect of idea]

As explained above, the present invention includes a position detection element disposed opposite to the rotation locus of the rotor, a signal generation circuit that outputs a rectangular pulse signal based on a signal from the position detection signal, and a duty cycle of the rectangular pulse signal. The rotor is brought into a locked state by a simple configuration that includes a switching circuit that switches between the rotor magnetic poles and the stator coil so that torques in the forward and reverse directions are alternately generated at a period corresponding to the ratio. Since it can be held electrically, the number of parts can be significantly reduced compared to the conventional method, thereby reducing costs and improving reliability due to the simplified structure. .

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a cross-sectional view, FIG. 2 is an electric circuit diagram, FIG. 3 is a diagram showing waveforms of a position detection signal and a rectangular pulse signal, and FIG. 4 is a diagram showing waveforms of a position detection signal and a rectangular pulse signal. FIG. 3 is a diagram for explaining the operation, showing a part of the rotor magnetic poles in an expanded state. In the figure, 1 is a rotor, 3a to 3h are rotor magnetic poles, 4 is a permanent magnet, 5 is a stator, 7a, 7a',
7b, 7b', 7c, 7c' are stator coils, 8,
9 is a magnetic sensor, 10 is a magnetic sensor (position detection element), 12 is a comparator (signal generation circuit), 14
is a switching circuit.

Claims (1)

[Claims for Utility Model Registration] 1. A stator coil set to two or more phases, a rotor magnetic pole made of a permanent magnet, and the rotor by controlling the energization timing of the stator coil according to the rotational position of the rotor magnetic pole. In a brushless motor configured to selectively rotate the rotor in a forward direction and a reverse direction, the position detection device is arranged to face the rotation locus of the rotor and whose polarity is periodically reversed as the rotor is rotated. a position detection element that outputs a signal; a signal generation circuit that outputs a rectangular pulse signal only during the period when the position detection signal is in one polarity; A switching circuit is provided to alternately generate torque in the forward and reverse directions between the stator coil and the rotor magnetic poles by switching the current direction of the stator coil between when outputting and when outputting is stopped. A brushless motor featuring: 2. The brushless motor according to claim 1, wherein the position detection element is constituted by a magnetic sensor that detects magnetic flux from the rotor magnetic poles.