JPH05227720A - Revolving magnetic field generator for electromagnetic rotary machine - Google Patents

Abstract

PURPOSE:To reduce the size and thickness of an electromagnetic rotary machine itself by winding at least two or more independent coil winding wires substantially in parallel, and coupling the wires in parallel to lower a resistance of the coil. CONSTITUTION:A coil 15 is coupled in parallel with a driving coil 10. The two coils are coupled in parallel to reduce a resistance between a power source voltage and a collector of a transistor 14, and the number of turns of the coil can be increased when a resistance between the power source voltage and the collector of the transistor 14 is set to the same resistance value. Then, when the connection of the coils at the time of starting is explained only with respect to a U-phase coil, a SW1 connects a terminal (a) of a coil 10C to a terminal (c) of a coil 15U, and a SW2 connects a terminal (b) of the coil 10U to a terminal (d) of the coil 15U. In the case of the connection of the coil at the time of rotation with a rated load, the SW1 is opened, and the SW2 connects the terminal (b) of the coil 10U to the terminal (c) of the coil 15U. Accordingly, the coils 10, 15 are connected from a parallel connection to a series connection to lower a driving current, thereby reducing power consumption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic rotating machine such as a motor used in, for example, a floppy disk drive, and more particularly to improvement of a rotating magnetic field generating means for increasing its starting torque.

[0002]

2. Description of the Related Art A conventional motor configuration will be described with reference to the drawings. FIG. 7 is a fragmentary plan view of a radial gap type three-phase brushless motor, and FIG. 8 is a sectional view taken along line XX of FIG. In such a conventional brushless motor, three magnetic circuits, namely, a magnetic circuit for generating a rotational driving force, a magnetic circuit for generating a rotation speed signal (this is referred to as an FG signal), and a rotating magnetic field are generated. A magnetic circuit for forming is formed.

First, the schematic structure of the three-phase brushless motor will be described with reference to FIG. 8. The substrate 7 is made of a magnetic material such as iron, and the oil-impregnated bearing 9 is press-fitted in the center thereof. Rotating shaft 5
Is integrally provided with a rotor yoke 4 via a shaft fixing member 6, and is further fitted to an oil-impregnated bearing 9. The rotor yoke 4, the drive magnet 1, and a rotation speed detection magnet (this is referred to as an FG magnet). An integrated object such as 2 freely rotates with respect to the substrate 7.

A drive magnet 1 (FIG. 7) is fixed to the outer edge portion of the rotor yoke 4, and as is well known, by applying a rotating magnetic field to the drive magnet 1 by using a plurality of drive coils 10, the rotor yoke is formed. 4 is driven to rotate. For this reason, the drive magnet 1 is magnetized to have 24 poles in the radial direction and is fixed to the inner side of the outer edge portion of the rotor yoke 4, as shown in FIG.

To actuate a rotating magnetic field, a plurality of drive coils 10 are provided wound around a stator yoke 11, while the stator yoke 11 is provided with a rotating shaft 5.
Radial around (18 slots in Figure 7)
A plurality of drive coils 10 are also provided on the yoke 11 in the circumferential direction. The stator yoke 11 is fixed on the iron substrate 7 by a fixing member such as a screw (not shown).

In the above structure, the stator yoke 11
Together with the drive magnet 1, the rotor yoke 4, and the drive magnet yoke 3 form a closed magnetic circuit.

As is apparent from FIGS. 7 and 8, in this embodiment, the Hall element for detecting the drive timing of the drive coil is not provided, and the excitation timing is known from the counter electromotive voltage of the drive coil. Is detected in.

A change in magnetic flux density from the drive magnet 1 is detected by a counter electromotive voltage detection circuit, and by a matrix circuit,
The phase difference of the magnetic field to be generated by the drive coil 10 of the stator 11 with respect to the magnetic field of the rotating drive magnet 1 is detected, and a current is passed through each phase of the drive coil at an appropriate timing to generate a rotating magnetic field. This rotating magnetic field rotates the rotor 4.

On the other hand, the FG magnet 2 is fixed to the outermost peripheral edge portion of the rotor yoke 4, and is magnetized for 120 poles in total. The surface of the iron substrate 7 facing the FG magnet 2 has a comb-shaped bent pattern 120.
The power generating line element 7a of the book is formed by etching with a copper pattern or the like.

With the above configuration, when the rotor yoke 4 is started to rotate, a sine wave having a frequency corresponding to the rotation speed of the rotor yoke 4 is generated from the power generating line element. Therefore, a constant speed rotation control is performed by a control circuit (not shown). To do.

Next, the connection state of the three-phase coil and the obtained torque will be described.

First, a method of connecting the coils will be described.

In FIG. 10, three-phase coils 10U and 10
V and 10 W are Y-type connected, and the other ends are Tr1 to T
The timing circuit 12 should be connected by r6 to either the power supply voltage side, the ground side, or the open side.
Controlled by. Here, Tr1 to Tr6 correspond to the sink transistor or the source transistor of the output circuit. Reference numeral 13 is a feedback resistor, which is used for current detection and current limitation for constant speed rotation control.

FIG. 9 shows an equivalent circuit of the output stage of FIG.
The resistance value of the phase coil 10 is R coil, and the number of turns is n turns. The transistor 14 corresponds to both the sink transistor and the source transistor in FIG. 10, and controls the coil current by the control signal Vin. The resistance value of the feedback resistor 13 is R.

When the starting torque Ts generated at the time of starting the motor is calculated, from FIG. 9, Ts = Kt (Vcc-Vce) / (Rcoil + R) (1) = Kt · Imax (2) where Kt is a torque constant, Imax Is a starting current and is proportional to the number of turns n of the drive coil.

Assuming that the coil space of the conventional example shown in FIGS. 7 and 8 is within the range of the broken line shown in FIG. 11, if the starting torque is designed to show the maximum value, as shown in FIG.
The wire diameter is 0.14mm (outer diameter is 0.167mm), the number of turns is 64, and the coil resistance for one slot is 0.6.
It becomes 03Ω (3.62Ω for one phase of the coil). For convenience,
The torque constant at this time is defined as 1, and the starting torque is also defined as 1.

The relationship between the rotational speed and torque and the current and torque in this conventional example is shown by the solid line in FIG.

[0018]

However, the structure of the conventional rotating magnetic field generating means described above has the following problems. That is, 1) As the motor becomes smaller and thinner, the space around the coil winding becomes smaller and the starting torque cannot be earned. If the magnetic head is attracted to the magnetic disk media, the motor cannot be started and the information However, there is a problem in that the recording and reproduction of is impossible.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to realize a compact and thin motor without reducing the starting torque.

[0020]

In order to solve the above-mentioned problems and to achieve the object, the rotating magnetic field generating means of an electromagnetic rotating machine according to the present invention has at least two independent coil windings for driving coils. Are wound substantially in parallel and connected in parallel, thereby increasing the number of turns of the drive coil, that is, the torque constant Kt, without increasing the coil resistance value, that is, without lowering the starting coil current Imax. The starting torque Ts (= Kt · Imax) is obtained.

Further, when the motor approaches the target number of revolutions, a switching circuit for connecting the parallel connection to the serial connection is constructed to reduce the total drive current and reduce the power consumption at the rated rotation.

[0022]

According to the present invention, the coil for generating the rotating magnetic field is
By winding at least two or more independent coil windings substantially in parallel and connecting them in parallel to reduce the coil resistance and increase the starting torque, the electromagnetic rotating machine itself can be made smaller and thinner. By providing a switching circuit that can be connected in series at the rated speed, low power consumption is achieved.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a spindle motor having a rotating magnetic field generator will be described below with reference to the accompanying drawings. First Embodiment FIG. 1 shows an equivalent circuit diagram for explaining the present invention. The difference from FIG. 9 is that the coil 15 is connected in parallel to the drive coil 10. By connecting the two coils in parallel, the resistance between the power supply voltage and the collector of the transistor 14 becomes low. In contrast to FIG. 9, when the resistance between the power supply voltage and the collector of the transistor 14 is set to the same resistance value, The number of turns of the coil can be increased.

When the coil resistance of the present invention is R'coil, the number of turns is n ', the torque constant is K't, and the starting coil current is I'max, Rcoil to R'coil, n <n', Kt <K. 'T,
Since Imax to I'max, the starting torque T's is Ts <T's. However, since the drive current is connected in parallel, it tends to be higher than in the conventional example. This measure will be described later.

When the present invention is applied to the winding space of the conventional example shown in FIG. 11, the calculation result of how much the starting torque increases is shown in the lower part of FIG. Wire diameter 0.11
mm (outer diameter 0.135 mm), the number of turns is 78, and the coil resistance is 0.603 Ω (3.62 Ω per phase). The torque constant becomes 1.22 times, and the starting torque also becomes 1.22 times because the coil resistance value does not change.

The rotation speed vs. torque and the coil current vs. torque characteristics of the embodiment of the present invention are shown by broken lines in FIG. The dotted line in the figure is the sum of the coil currents flowing through the coils 10 and 15 in FIG. 1, which is twice the current-torque curve of the present invention shown by the broken line. It is about 1.6 times that of the conventional example (solid line in FIG. 13).

FIG. 2 shows an embodiment in which the present invention is applied to a three-phase brushless motor. Conventional example is different from FIG.
That is, two drive coils 10 and 15 having a wire diameter as thin as 0.14 mm to 0.11 mm are connected in parallel. With the above configuration, the torque constant can be increased without increasing the coil resistance value, and thus the starting torque can be increased.

As can be seen from the torque current characteristic of FIG. 13, in the embodiment of FIG. 2, the coil current decreases in inverse proportion to the increase of the torque constant (1 / 1.22 =
0.82), the driving current is twice the coil current (0.82 × 2 = 1.64) because the coils are connected in parallel.
Therefore, at the rated load rotation, a driving current about 1.6 times that of the motor shown in the conventional example is required, and the power consumption is about 1.
It is not preferable because it increases 6 times. Second Embodiment Therefore, in particular, in a motor requiring low power consumption, in order to obtain a starting torque at the time of starting, the rotating magnetic field generating means shown in FIG. 2 is used. , 15 is changed from parallel connection to series connection,
A structure capable of reducing the drive current is proposed, and its operation will be described with reference to FIGS. 3 and 4.

FIG. 3 is a diagram showing a method of connecting the coils at the time of start-up only for the U-phase coil, which is equivalent to FIG.
SW1 and SW2 are formed between the coils 10 and 15,
SW1 is a terminal a of the coil 10U and a terminal c of the coil 15U
SW2 is connected to the terminal b of the coil 10U and the coil 1
The terminal d of 5U is connected. SW1 and SW2 can be constituted by semiconductor switches such as power MOSFETs having low on-resistance.

FIG. 4 is a diagram showing a method of connecting the coils at the time of rated load rotation. The coils 10U and 15U are S
They are connected in series by W2. Only U-phase coils are shown. SW1 is open and SW2 is coil 10U
The terminal b of the coil is connected to the terminal c of the coil 15U, SW
As a signal for controlling the connection method of 1 and SW2, although not shown, a rotation speed lock signal output from a rotation speed control circuit or the like can be used.

With the above configuration, when the motor approaches the rated speed, the coils 10 and 15 are changed from parallel connection to series connection, and the drive current is reduced, whereby low power consumption of the motor can be realized. Third Embodiment The above-described embodiment is further possible without departing from the spirit of the present invention.

In FIG. 1, since the coil currents of the collector coils 10 and 15 of the output transistor 14 flow in, the collector current is doubled as compared with the conventional example shown in FIG.
Therefore, the emitter-collector saturation voltage of the transistor 14 increases, the voltage applied to the coil decreases, and the starting torque may not increase as expected, as can be seen from the formula shown in FIG.

FIG. 5 shows another embodiment of the present invention for solving the above problem. The first embodiment is different from FIG. 1 in that a transistor 16 for driving the current of the coil 15 is newly added. The transistor 16 has the same characteristics as the transistor 14, and also has the same base input signal.

FIG. 6 is a diagram in which the above embodiment is applied to a three-phase brushless motor, and in order to drive the coil currents of the coils 15U, 15V and 15W, a source is newly added as compared with the first embodiment. Transistors (Tr7, Tr9, T
r11) and sink transistors (Tr8, Tr10, T)
r12) is added to each.

With the above structure, the emitter-collector voltage does not increase, so that the starting current does not decrease and a sufficient starting torque can be obtained.

[0036]

As described above, since the rotating magnetic field generator for an electromagnetic rotating machine according to the present invention can increase the torque constant without reducing the starting current, a sufficient starting torque can be obtained and the electromagnetic rotation can be improved. The machine itself can be made smaller and thinner. Furthermore, at the rated load rotation,
By changing the connection of the coils from parallel connection to series connection, the drive current can be reduced without lowering the torque constant, so that low power consumption can also be realized.

Further, although the radial gap motor has been described in the embodiment of the present invention, it is obvious that it can be applied to an axial gap motor.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram for explaining a rotating magnetic field generator that is a first embodiment of the present invention.

FIG. 2 is a circuit diagram when the first embodiment of the present invention is applied to a three-phase brushless motor.

FIG. 3 is a block diagram showing a starting state of the rotating magnetic field generator which is the second embodiment of the present invention.

FIG. 4 is a block diagram showing a state of the rotating magnetic field generator according to the second embodiment of the present invention when rotating at a rated load.

FIG. 5 is an equivalent circuit diagram for explaining a rotating magnetic field generator that is a third embodiment of the present invention.

FIG. 6 is a block diagram when a third embodiment of the present invention is applied to a three-phase brushless motor.

FIG. 7 is a plan view illustrating the structure of a conventional three-phase brushless motor.

8 is a partial cross-sectional view of the motor shown in FIG.

FIG. 9 is an equivalent circuit diagram for explaining a rotating field generator of a first conventional technique.

FIG. 10 is a block diagram for explaining a rotating field generator of a first conventional technique.

FIG. 11 is a diagram for explaining a winding space of a coil.

12 is a table showing design values in the case of designing in the winding space shown in FIG. 5 in the conventional example and the example of the present invention.

13 is a rotational speed-torque characteristic of the design example shown in FIG.
Graph of current-torque characteristics.

[Explanation of symbols]

 1 Drive Magnet 2 FG Magnet 4 Rotor Yoke 10 Coil 11 Stator 15 Coil Tr1 to Tr2 Coil Drive Transistor SW1, SW2 Coil Connection Switching Switch

Claims (3)

[Claims] 1. An electromagnetic rotating machine comprising a rotor, a stator, a coil for generating a rotating magnetic field, and a drive circuit, wherein the coil is formed by winding at least two independent coil windings substantially in parallel. A rotating magnetic field generator for an electromagnetic rotating machine, which is configured to be connected in parallel. 2. The rotating magnetic field generator according to claim 1, wherein at least two coil windings constituting the coil are connected in parallel when the electromagnetic rotating machine is started or stopped. A rotating magnetic field generator for an electromagnetic rotating machine, comprising switching means for connecting the electromagnetic rotating machine in series when the approximate rotating speed is reached. 3. The rotating magnetic field generator for an electromagnetic rotating machine according to claim 2, wherein the switching means is a semiconductor switch.