JPH01255494A - Method of driving three-phase dc motor - Google Patents

Abstract

PURPOSE:To generate great torque at the time of starting and improve rise characteristics, by driving with the electrical conduction of 120 degrees at the time of starting, and by switching it to the electrical conduction of 180 degrees to perform steady-state operation when a device comes to have a previously set rotational frequency. CONSTITUTION:A three-phase DC motor is composed of the stator of 12 poles and the rotor of 8 poles, and the stator is wound up with a winding 4 to form a Y- connection. The rotor consists of permanent magnets, and three Hall elements Hu-Hw which are rotatable at intervals at the electrical angle of 120 degrees are arranged. The driving circuit of the motor consists of comparators C1-C3, exclusive OR gates X1-X3, try state buffers B1-B9, and the like, and each output from the Hall elements Hu-Hw is compared with each other by the comparators C1-C3, and specified signal processing is performed and after that, the output of driving current to the winding 4 is generated. In this case, a device is driven with the conduction of 120 degrees which can obtain great torque at the time of starting, and when the device comes to previously set rotational frequency, then the conduction is switched to the conduction of 180 degrees. As a result, even if great current is not permitted to flow at the time of starting, rise can be quickly performed with the great torque.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for driving a three-phase DC motor suitable for devices that perform steady rotation at high speed in a short period of time, such as hard disk drives and optical disk drives. .

[Conventional technology]

Three-phase DC motors are available in 120-degree energization and 180-degree main energization drive systems, and among these, the 120-degree energization drive method is generally adopted in hard disk drives. This is because 120 degree energization allows a large torque to be obtained with a small current.

In other words, the rotation speed Ω and torque T of the three-phase DC motor are: Well, - g-kKt It is known that there is a relationship between

In addition, if the magnetic flux density distribution of the drive magnet (rotor) has a sinusoidal shape, a three-phase DC motor with the same windings
When energized at 20 degrees and 180 degrees, the ratio of torque constant K and winding resistance R1 is (hereinafter subscripted 120, 1
80 indicates 120 degree energization and 180 degree energization), K7°. : Kt+s. -1: δ/2 Ralt. It is also known that :R08°=1:3/4. Then, the relationship between the motor rotation speed Ω and torque T in 120-degree energization and 180-degree energization is Trto "Ky + zo 1° TI * o - KrIto' In. Therefore, in the case of 180-degree energization,
At maximum rotation, which is steady operation, torque T1. . -〇, so Ω+11. = (2/fJ)Ω16. This shows that the maximum rotation is 2/A times as high when energized at 180 degrees as compared to when driven at 120 degrees.

On the other hand, torque 'T'+s. For the same drive current, T, 110. w (δ/2)TI□.

Therefore, it can be seen that only 672 times the torque can be obtained.

[Problem to be solved by the invention]

By the way, as mentioned above, in the conventional hard disk drive, the rotor is driven by the 180" energization method.
This energization method has the characteristic that maximum rotation increases, but torque is low. Therefore, in order to improve the startup characteristics at startup, it is necessary to flow a large startup current.

However, as the starting current increases, there is a problem in that power consumption increases, and it is also necessary to increase the wire diameter of the winding to accommodate the large current. Increasing the wire diameter of the winding not only increases costs, but also increases the
In order to secure the required number of turns, it becomes difficult to downsize the three-phase DC motor.

This invention was made in view of the actual state of the prior art as described above, and its purpose is 6. The object of the present invention is to propose a method for driving a three-phase DC motor with good startup characteristics and low power consumption.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a driving method for driving a three-phase DC motor having a stator provided with three-phase windings and a rotor that rotates in response to switching of the excitation phase of the stator. Sometimes it is driven by 120' energization, and after starting, it turns 180° when the preset rotation speed is reached.
It is configured to be driven by switching to energization.

[Effect]

According to the above means, a large torque can be obtained at the time of startup.
20 @ Driven by energization 7, preset rotation speed,
For example, the maximum steady rotation speed with 120° energization is 18
Since the energization is switched to 0°, it is possible to quickly start up with a large torque and obtain high-speed rotation after that, without having to flow a large current especially at the time of starting.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a circuit diagram showing a drive circuit of a three-phase DC motor according to an embodiment, FIG. 2 is an explanatory diagram showing a schematic configuration of a three-phase DC motor according to an embodiment, and FIG. 3(a).

(b) is an explanatory diagram showing the connection state of the three-phase windings and the flow of the t current, and Figures 4 (a) and (b) are each 12
It is a timing chart showing the detection output of the Hall element, the output applied to the stator, and the state of excitation of the U, V, and W phases in 0-degree energization and 180-degree energization.

In FIG. 2, a three-phase DC motor 1 consists of a 12-pole stator 2 and an 8-pole rotor 3, and a winding 4 is wound around the stator 2, as shown in FIG. 3(a).

As shown in (b), they are Y-connected. Rotor 3 is S
It consists of a permanent magnet formed by alternately magnetizing poles and north poles, and is rotatably arranged on the outer circumferential side of the stator 2. Further, directly below the rotor 3, three Hall elements (6°Hv, Hw) are arranged for each two phases of the stator 2 at an interval of 60 degrees mechanically, that is, 120 degrees electrically.

The drive circuit shown in FIG. 1 includes comparators C+ and Cz.

C2, exclusive ○Rage-X+, X2, Xz, tri-state buffer B, or B, output terminal T, TV, T, 4, tri-state buffer B+, Bz, Bs, Bt, Bs.

B, switching terminal 5, and Hall element Hu.

The outputs from H, , H, are compared by comparators C+, Cz, and C3, and after predetermined signal processing is performed, a drive current to the winding 4 is output.

Specifically, driving of a three-phase DC motor in 120-degree energization and 180-degree energization will be explained. In the case of 120 degree conduction, the tri-state buffers B+ and B2 of the drive circuit
, Bs are ON, and BT, Be, and B9 are OFF.

In this case, the terminals Tu, Tv, Tu are respectively vu-hu (h,=hv) Open (hu-hv) v, -hv (hv=h,) Open (hvxll,) V,=h, ( h, #h,) Open (h,=hu). Here, hu, hv, h are the inputs from the Hall elements HII, Hv, Hw, respectively, to the comparators C,,C,
, C3, a logical value l or 0 is output, and the outputs from the output terminals Tu, Tv, T, and I are ■. +V
V+VP also outputs a logic value level 1 or O, or its output is disconnected (open state). Example: Yo,
Output 1. If rU is 1 and ■9 is 0, a current flows from terminal T toward Tv as shown in FIG. 3(a), and the U phase becomes the S pole and the ■ phase becomes the N pole. At that time, output ■1 is 0p
In en, the W phase cannot become a magnetic pole. Here, h,=hv
When ■. Outputting -hu means that when hu has a logical value of 1, vU also has a logical value of 1, and when hu has a logical value of O, VU also outputs a logical value of 0, so hu=
hv, vU is 0pen means that the comparator output hu(
! : When hv becomes equal, the output of VU becomes Qp
It means to become en (separated).

Therefore, the comparator CI from the Hall elements Hu, I4v, and Hw, which are arranged 120 degrees apart in electrical angle.

When the comparison values output via Ct and Cs are output with a 120 degree phase shift as shown in Figure 4(a), the first 12
At 0 degrees, the output VU is 1, at the next 120 degrees, the output Vv is 1, and at the next 120 degrees, the outputs V and I are switched, and so on. On the other hand, for the first 60 degrees, the output ■9 is 01 order 1
20 degrees is the output ■.

is 0, and the next 120 degrees is ■. becomes O, so that the excitation pole is switched every 60 degrees as shown in FIG. 4<a>, and the rotor 3 rotates.

On the other hand, in the case of 180 degree energization, the tri-state buffers B to B6 of the drive circuit are turned off.

When B or B is turned on, the output terminals Tu, Tv,
The output to Tw,V,,V,,V,is,v,−h,.

v-hll v, -hv. That is, as shown in FIG. 4(b),
For the first 180 degrees, the comparison output is 1, and the output ■9 is 1.
Comparison output from 120 degrees to 300 degrees, output at 1■
8 is 1. From 240 degrees to 420 degrees, the comparison output is 1.
Output with■. changes to 1, and outputs at the first 180 degrees ■When 9 is 1, outputs ■ at the first 60 degrees. is 1,
Since ■1 is O, current flows from U phase and ■ phase to W phase, and U
The phase and V phase become the small excitation pole s, and the W phase becomes the large excitation pole N.

Also, for the next 60 degrees, ■9 is 1 as shown in Figure 3 (b).
Since VLl and V are O, the ■ phase is the large excitation pole S.

The U phase and W phase are small excitation poles n, and the next 60 degrees are V.

Since and v, , are 1 and vlj is O, the U phase is switched to the large auxiliary magnetic pole N, and the V and W phases are switched to the small excitation %s, thereby causing the rotor 3 to rotate.

In this embodiment, the 120 degree energization and the 1
An "L" signal is output to the switching terminal 5 for 80-degree energization. As a result, as mentioned above, the tristate buffer B+,
Bh, Bi is 0NXBt.

Ba and B are turned off and driving is performed by 120 degree energization. In this way, it is started by 120 degrees of energization, and when steady rotation is reached, the switching terminal 5 becomes "H" by the output from the rotation speed detection means (not shown), and this summer, the tri-state buffer B or B is turned off. BT
, Ba and BT are turned on. As a result, the drive circuit becomes 1
Switched to 80 degree energization state, 3-phase DC motor 1
It is driven by 80-degree energization, and as mentioned above, steady operation is performed at the maximum rotation speed of 27 fJ, which is the maximum rotation speed of 120-degree energization.

In addition, the Hall element H arranged to correspond to 120 degree energization
When a, Hv, Hi= are used with 180 degrees of current, some torque ripple will occur, but the 3-phase DC motor l has reached steady rotation, and the inertia of the disk and rotor 3 is effective, such as in a hard disk drive. If so, it falls within a range that does not pose a problem in use.

In this way, in the above embodiment, especially when a DC motor for a hard disk drive requires a large torque at startup and a high rotational speed during steady rotation, 120° current is applied at startup and during steady rotation. By switching the energization angle such as 180" energization, startup can be performed quickly, and steady rotation can therefore be achieved in a short time. Also, the winding 2 is common and has a large diameter. Since this is not necessary, it can be made smaller, and since there is no need for a large current to flow at startup, it is possible to reduce power consumption.

In addition, the torque capacity does not change even if the conduction angle is changed, so if the current is passed even if the rotation speed increases, it is possible to respond to changes in load torque. The resistance to is well maintained.

〔Effect of the invention〕

As is clear from the above explanation, this invention is set to drive with 120 degree energization at startup, and switch to 180 degree energization when a preset rotation speed is reached for steady operation. The large torque improves the start-up characteristics and allows the rotation to quickly increase to steady rotation, resulting in high-speed steady rotation. Furthermore, since there is no need to flow a large current at this time, operation with less power consumption is possible.

[Brief explanation of the drawing]

All figures are for detailed explanation of this invention.
The figure is a circuit diagram showing the drive circuit of a three-phase DC motor, Figure 2 is an explanatory diagram showing the schematic configuration of the three-phase DC motor, and Figure 3 (a)
, (b) is an explanatory diagram showing the connection state of the windings and the flow of current, and FIG. 4 (a). (b) shows the detection output of the Hall element, the applied output to the stator, and U and V at 120-degree energization and 180-degree energization, respectively.
, is a timing chart showing the excitation state of the W phase. l...3-phase DC motor, 2...
...Stator, 3...Rotor, 4...
......Winding, 5......Switching terminal. Figure 2 v'S Figure 3 tbino
(b) Tt
Tw Tw
Tu figure 4 and σ no Buri work 1

Claims (1)

[Claims] In a driving method for driving a three-phase DC motor, which includes a stator having three-phase windings and a rotor that rotates in response to switching of the excitation phase of the stator, one
A method for driving a three-phase DC motor, characterized in that the motor is driven by 20-degree energization, and after starting, when a preset rotation speed is reached, the motor is switched to 180-degree energization.