JPH0527358B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for driving a DC brushless motor.

(Prior Art) The structure of a conventional DC brushless motor is shown in FIGS. 1a, b, and c. Reference numeral 1 denotes a stator, and a substrate 4 is disposed on a stator yoke 2 made of a magnetic material with an insulating plate 3 interposed therebetween. The board 4 has six armature coils 5-
1,5-2,5-3,5-1',5-2',5-
3' are connected in three phases (φ ₁ , φ ₂ , φ ₃ ) as shown in FIG. Further, a speed detection pattern 7 (hereinafter abbreviated as FG pattern) is provided around the periphery. 8 is a bearing. 9 is a rotor;
A rotor yoke 10 made of a magnetic material has a magnet 1 magnetized into 8 equal parts in a fan shape with alternating N and S poles.
1 and a ring-shaped magnet 12, which is divided at the same intervals as the pitch of the FG pattern 7 and magnetized alternately in N and S poles, is attached to the stator 1 by a shaft 13. To briefly explain the principle of operation, the position of the rotor 9 is detected by the detection outputs of the three Hall elements 6, and when the current at that position is applied to the armature coil 5, the armature coil 5 operates according to Fleming's left-hand rule. However, since the armature coil 5 is fixed, the magnet 1
A reaction force acts on the rotor 1, causing the rotor 9 to rotate. When the rotor 9 rotates, the ring-shaped magnet 12
An alternating current is induced in the FG pattern 7. By converting it into a pulse and measuring the pulse width, that is, the period of the induced current, acceleration, deceleration, and constant speed control become possible. Therefore, since there are position detection and speed detection, there are four types of signals, the number of circuit components increases, and problems arise such as variations in the Hall elements 6 and installation errors during assembly. In addition, since the Hall element 6 is placed in the center of the armature coil 5, it becomes impossible to wrap the coil sufficiently inside the armature coil 5, making it difficult to generate sufficient torque and complicating assembly. There were flaws.

(Object of the Invention) In order to eliminate these drawbacks, the present invention provides a method for driving a DC brushless motor in which the position detection element is removed and the motor is controlled only by the speed detection element.

(Structure of the Invention) The present invention provides a rotor having rotor magnets that are magnetized in alternating N and S segments in the circumferential direction, and a row of rotor magnets provided concentrically along the outer circumference on the outer circumference of the rotor. a predetermined number of slits, a first sensor that detects the presence or absence of the slits according to the rotation of the rotor, a second sensor that is arranged 90 degrees electrically offset from the first sensor; In a method for driving a DC brushless motor having a counter that counts output pulses from the first and second sensors as the rotor rotates, at startup, after passing current through one excitation phase for a predetermined period of time, Similarly, current is passed through an excitation phase adjacent to the excitation phase for a certain period of time to position the rotor at a predetermined position;
After the rotor is positioned at a predetermined position, the rotor is rotationally driven by sequentially switching the current flowing through each excitation phase layer according to the count value of the counter, and will be described in detail below. do.

(Example) An example of the present invention is shown in FIG. Items that are the same as before are expressed using the same numbers.

The rotor 9 has a rotor yoke 10 and a magnet 11
, a speed detection slit 14 and a shaft 13. The stator 1 is the same as the one shown in FIG. 1 with the Hall element 6 and FG pattern 7 removed, so the illustration is omitted here. FIG. 3 is a simplified circuit diagram of a three-phase motor, 15 to 20 are transistors, 21 to 23 are armature coils, 21 is the armature coil 5-1, 5-1' shown in FIG. 1, and 22 is also 5- 2,5-2',23 are also 5-3,5-
Corresponds to 3'. 24a is the positive terminal of the power supply, 24
b is the negative terminal of the power supply. Armature coil 21~
In the case of two-phase excitation, the direction of the current flowing through 23 is as shown in Figure 3, and -1 and -2 in the opposite direction.
, -3, and each armature coil 21,
Arrows at 22 and 23, -1, -2,
Figure 4 shows the output torque waveform when a constant current in the −3 direction is applied. In Figure 4, a, b,
c, d, e, f, a' are each output torque waveform and dotted line P
−P′ and is the intersection point A, B, C, D, E, F,
A' is the rotor 9 position that generates the torque at the points a, b, c, d, e, f, and a'.

The six types of waveforms are similar shapes shifted by 60 degrees in electrical angle, -3 from point a to point b in the figure, and from point b to c.
If the direction of current flow is changed every 60 degrees from point c to point d, etc., the dotted line P
The output torque with the least ripple is obtained above -P', and the rotor 9 rotates in the normal direction (clockwise when viewed from the direction of the arrow in FIG. 2a). For reverse rotation (counterclockwise), use the area below the dotted line Q-Q'.

If the current is switched every 60 degrees of electrical angle as described above, it will be switched six times in one cycle (a to a'). Also, this one cycle is the N.
This is the pitch of the south pole, and as is clear from FIG. 2b, there are four periods per rotation of the rotor 9, so current switching is required 6×4=24 times per rotation of the rotor 9. At this time, speed detection slit 1
If 4 is divided into 96 parts, in one energizing period, for example from point a to point b in Fig. 4, 96÷24=4 pulses or 8 pulses, which is twice as many if the bit information is 0 or 1. The condition is revealed.

At startup, the magnet 1 which is the rotor 9
The relative positional relationship between the armature coils 1 and the armature coils 21 to 23 is between points A and A' in FIG.

Therefore, if you first apply a current in the direction, leave enough time for the magnet 11 to stop, then apply a current in the same direction, and leave a sufficient time as well, then
When a current flows in the direction, point A (or point A')
Even if the rotor does not move in a balanced state, by applying a current in the next direction, the rotor will leave the balanced state and become locked at point E, completing the rotor's home positioning at startup. .

In this way, no matter where the magnet 11 is at the time of startup, the position of the magnet 11 can be set to point E by flowing current in the order of →, so when driving forward rotation from then on, -
When driving in the order of 1 → -2 → -3 →→→→ -1 ... or in the opposite direction, -3,
The current can be passed in the order of −2, −1 →→→→ −3, and so on. At this time, the timing of switching the current direction may be changed when four pulses or eight states of the output from the speed detection slit 14 are detected, as described above.

Next, a method for both forward and reverse rotation will be explained.
In order to detect the direction of rotation, if the detection sensors of the speed detection slit 14 are set to be shifted by 90 degrees in electrical angle, the detection outputs φA and φB at that time will be as shown in FIG. The φA, φB2 bits (φB: upper bit,
The value shown at the bottom of FIG. 5 is a digital representation of the sensor output using φA (lower bit). Therefore, the digital output value of the sensor changes from 0 → 2 → 3
→ When 1 → 0... rotates forward, 0 → 1 → 3 → 2 → 0
...is a reverse rotation. Therefore, if the speed detection slit 14 is the same, the above-mentioned current switching timing will be determined by 16 sensor output values, which are four times as many as four pulses. Now, regarding the driving method, the initial settings are the same as those described above, so a description thereof will be omitted.

The method of switching the rotation direction will also be explained with reference to FIG. Now, if driving is started in the forward rotation direction, the current direction in the forward rotation direction and the current direction in the opposite direction are prepared as information for the reverse rotation direction. For example, when a current in the direction is flowing as a forward rotation direction, it is sufficient to prepare a current direction of -2 as a reverse rotation direction.

It also counts the output of the sensor, increments it when the rotation direction is forward, returns it to 0 when the count value reaches 16, decrements it when it rotates in the reverse direction, and sets it to 16 when the count value reaches 0. I'll do it like that.

If the direction of rotation is switched at point F in Figure 4, a current in the direction flows at point D, and only the sensor is detected after that, and at point E, the current in the forward rotation direction -1 and the current in the reverse rotation direction. We only prepare the current information and leave the actual current flowing as is. Then, if it becomes locked at point F and stops,
All you have to do is to supply a current in the reverse rotation direction that is provided and drive it. If the output of the sensor is detected reliably even after passing point F, the information of −2 for the next forward rotation direction and −2 for the reverse rotation direction will be prepared, so no phase shift will occur.

By performing these steps continuously, the position of the rotor can be controlled even without the Hall element 6.

The speed control method may be performed in the same manner as in the past.

(Effects of the Invention) As explained in detail above, at startup, after passing current through one excitation phase for a predetermined period of time,
Similarly, a current is passed through an excitation phase adjacent to the excitation phase for a certain period of time to position the rotor at a predetermined position, and after positioning the rotor at a predetermined position,
Since the rotor is rotated by switching the current flowing through each excitation phase in sequence according to the count value of the counter, it is possible to control the drive of a DC brushless motor, which has a simple structure with only a row of slits provided in the rotor. This has the effect of making it possible to eliminate the need for a Hall element for position detection, which was conventionally required in DC brushless motors. Furthermore, since there is no need to provide a space for the Hall element at the center of the armature coil, it becomes possible to increase the number of turns of the coil and increase the power of the motor.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of a conventional DC brushless motor, in which a is a plan view of a rotor, b is a sectional view, c is a plan view of a stator, and d is a diagram showing connections of armature coils. FIG. 2 is a structural diagram of the DC brushless motor of the present invention, in which a is a sectional view of the rotor portion and b is a plan view of the rotor. FIG. 3 is a simplified circuit diagram of a three-phase motor, FIG. 4 is an output torque waveform, and FIG. 5 is a diagram explaining the operation of the slit. 1...Stator, 2...Stator yoke, 3...
...Insulating plate, 4...Substrate, 5-1, 5-2, 5-
3, 5-1', 5-2', 5-3'... Armature coil, 6... Hall element, 7... FG pattern, 8
... bearing, 9 ... rotor, 10 ... rotor yoke, 11 ... magnet, 12 ... ring-shaped magnet, 13 ... shaft, 14 ... speed detection slit, 15-20 ... transistor, 21 ...
23...Coil, 24a...Positive side terminal of power supply, 2
4b... Negative terminal of power supply.

Claims (1)

[Scope of Claims] 1. A rotor having rotor magnets divided and magnetized alternately in N and S directions in the circumferential direction, and a row of predetermined magnets provided concentrically along the outer circumference on the outer circumference of the rotor. a first sensor that detects the presence or absence of the slit according to the rotation of the rotor; a second sensor that is arranged 90 degrees electrically offset from the first sensor; In a method for driving a DC brushless motor having a counter that counts output pulses of the first and second sensors as the motor rotates, at startup, after passing a current through one excitation phase for a predetermined period of time, the excitation The rotor is positioned at a predetermined position by similarly passing a current through an excitation phase adjacent to the phase for a certain period of time, and after positioning the rotor at a predetermined position, the current flowing through each excitation phase layer is determined by the count value of the counter. A method for driving a DC brushless motor, characterized in that the rotor is rotationally driven by switching sequentially according to the following.