JP2002345289A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain mechanical non-contact between the sleeve which has a dynamic pressure bearing inside and the rotating shaft of a brushless motor by generating a holding force by the magnetic action between a stator core and a field magnet arranged in a rotor yoke, by exciting a plurality of stator windings in the same direction (pole) so as to avoid the mechanical contact between the sleeve and rotating shaft. SOLUTION: The brushless motor is driven by the magnetic action between the stator core which has the plurality of stator windings, is fixed on a circuit board, and held by the sleeve and the field magnet held by the rotating shaft and arranged in the rotor yoke. The motor is provided with a dynamic pressure fluid bearing means interposed between the sleeve and rotating shaft, on either one of which a dynamic pressure bearing groove is formed, and uses a dynamic pressure generating fluid. The holding force is continuously generated by conducting stator windings in a plurality of phases by means of a motor stop signal so as to avoid the mechanical contact between the sleeve and rotating shaft even when the motor is in a stop.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a brushless motor having a fluid dynamic bearing.

[0002]

2. Description of the Related Art In a brushless motor provided with a hydrodynamic bearing means by a hydrodynamic fluid generated between a sleeve having a hydrodynamic bearing groove formed on an inner periphery thereof and a rotating shaft,
When the motor is stopped, the load of the rotor yoke having the rotating shaft causes an inclination, and mechanical contact occurs between the rotating shaft and the sleeve in which the dynamic pressure bearing groove is formed on the inner periphery. The dynamic pressure bearing groove may be formed not on the sleeve but on the outer periphery of the rotating shaft.

[0003]

As a result, when the motor is started and stopped, the sleeve and the rotating shaft are started and stopped with the mechanical contact between the sleeve and the rotating shaft. I was letting it.

According to the present invention, even when the motor is stopped, a plurality of stator windings are all arranged in the same direction (same pole) in order to avoid mechanical contact between a sleeve having a dynamic pressure bearing formed on the inner periphery and a rotating shaft. To maintain a non-mechanical contact state by generating a holding force due to a magnetic action with a field magnet disposed on a rotor yoke.

[0005]

In order to achieve the above-mentioned object, the present invention provides a stator core fixed to a circuit board by exciting all of a plurality of stator windings in the same direction (the same polarity). And a brushless motor that generates a holding force due to a magnetic action between a field magnet disposed on a rotor yoke and non-mechanical contact even when the motor is stopped.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows that when the motor is stopped, when all phases (three phases) of the stator windings (coils) 3, 4, and 5 are energized, they are fixed to the circuit board having the stator windings 3, 4, and 5. FIG. 3 shows the magnetic action between the stator core 2 and the field magnet 1 arranged on the rotor yoke, and the arrows in the figure indicate the direction of the magnetic flux.

[0007] That is, by the magnetic action acting between the coils 3, 4, 5 and the field magnet 1, the stator core 2 and the field magnet are held concentrically, and the sleeve holding the coils 3, 4, 5 is held. (Not shown) and field magnet 1
Is held in a non-mechanical contact state.

FIG. 2 is a circuit diagram of the brushless motor shown in FIG. In FIG. 2, when a motor stop signal is input from the CPU 11 to the motor control driver IC 10, all phases are energized by the switching elements 6, 7, 8, 9 to excite the stator core, and the stator core is excited by the magnetic field. Due to the magnetic action with the field magnet, the sleeve and the rotating shaft are brought into a non-mechanical contact state, and the state tends to be maintained.

[0009] That is, in the rotation driving of the normal brushless motor, a motor drive signal (low state of the On / Off signal) and Vcc are output from the CPU 11, and the switching elements 6, 7, 8, 9 are turned on by the On / Off signal. And
The current flows through the switching elements 6, 7, 8 and the two current paths of the coils 3, 4, 5 and the switching element 9, which are sequentially selected by the motor control driver IC 10. The switching elements (transistors) 6, 7,
In each of the collectors 8, a current sufficient for rotating the brushless motor is supplied to a switching element (transistor) 6.
Power supply (not shown) that supplies enough voltage to flow through 7 and 8
Is connected.

On the other hand, a motor stop signal (On /
When the OFF signal (high state of the Off signal) and Vcc are output, the switching elements 6, 7, and 8 are turned off, and the current supplied through the switching elements 6, 7, and 8 is cut off. For example, coils 3, 4,
The switching element (transistor) is kept on by applying a voltage applied to the collector of the switching element (transistor) through a resistor (not shown) connected between the collector and the base. Since the switching element 9 is maintained in the ON state, a current of a magnitude necessary to maintain a non-mechanical contact state between the sleeve and the rotating shaft is generated by the signal Vc.
and flows through the switching element 9 through all the coils 3, 4, 5. At this time, the rotation is braked by the generation of the holding force, and the stop time is reduced.

FIG. 3 is a time chart showing the relationship between the motor drive signal On / Off and the current I. The current I1 is a current flowing at time t1 at the time of rotational driving, and is a value of a magnitude necessary for rotational driving (that is, a current value flowing through a current path including a selected switching element and a coil. Yes) and the current I2 is a current flowing at the time t2 when the rotation is stopped, and is a value large enough to generate a holding force (that is, a current value flowing through each coil).

[0012]

As described above, according to the present invention,
When the motor is stopped, a stator core having a plurality of stator windings and fixed to a circuit board is excited to avoid mechanical contact between the sleeve having a dynamic pressure bearing groove formed on one side and the rotating shaft. As a result, non-mechanical contact is caused due to the magnetic action with the field magnet arranged on the rotor yoke, and wear of the sleeve caused by mechanical contact between the sleeve and the rotating shaft can be prevented.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment according to the present invention, showing a magnetic action with a magnet when a magnetic field is generated in a stator core.

FIG. 2 is a circuit diagram of the brushless motor shown in FIG. 1;

FIG. 3 shows a time chart of the embodiment.

[Explanation of symbols]

 Reference Signs List 1 field magnet 2 stator core 3 coil (U phase) 4 coil (V phase) 5 coil (W phase) 6 switching element (transistor) 7 switching element (transistor) 8 switching element (transistor) 9 switching element (transistor) 10 motor Control driver IC 11 CPU

Claims (3)

[Claims] Claims: 1. A motor having a plurality of stator windings, which is rotationally driven by a magnetic action of a stator core fixed to a circuit board and held by a sleeve and a field magnet held by a rotating shaft and arranged on a rotor yoke. In a brushless motor provided with a hydrodynamic bearing means for generating dynamic pressure fluid interposed between a sleeve having a dynamic pressure bearing groove formed in one of the sleeves and a rotating shaft, the machine is operated even when the sleeve and the rotating shaft are stopped. A brushless motor characterized in that a plurality of phases of stator windings are energized by a motor stop signal so as to prevent contact, and continue to generate a holding force. 2. The brushless motor according to claim 1,
A brushless motor characterized in that a holding force is generated immediately after a motor stop signal is input, thereby providing a braking effect and shortening a stop time. 3. A stator having a plurality of stator windings, a stator core held by a sleeve, and a field magnet held by a rotating shaft and arranged on a rotor yoke, wherein the rotating shaft is provided in the sleeve. In a brushless motor arranged and having a dynamic pressure bearing groove formed in one of the sleeve and the rotating shaft, a voltage necessary for rotating the brushless motor is connected in series to each stator winding, and A switching element connected to a power supply for supplying the motor; a CPU for outputting a motor drive signal for turning on the switching element and a motor stop signal for turning off the switching element; and a response to the motor drive signal from the CPU. Sequentially selecting the stator winding and a switching element connected thereto in series to excite the stator winding with a current required for rotational driving; A motor drive driver that excites all of the stator windings with a current necessary to maintain the sleeve and the rotating shaft in a non-mechanical contact state in response to a motor stop signal from U. And a brushless motor.