JPS62285686A - Brushless motor - Google Patents

Abstract

PURPOSE:To eliminate the need for a position sensing element by obtaining a position sensing signal on the basis of voltage induced in a stator coil when turning a rotor magnet. CONSTITUTION:A switching circuit 1 is driven by an output from a driving-pulse generating logic 2, and conduction to stator coils La, Lb is controlled. The switching circuit 1 outputs pulse signals having edges corresponding to the zero-cross points of induced voltage each induced in the stator coils La, Lb. The pulse signals are inputted to D flip-flops 3, 4 and delayed at 45 deg., thus forming a pulse signal equivalent to an output signal from a position sensing element. The pulse signal is transmitted over the driving-pulse generating logic 2.

Description

[Detailed description of the invention] 3. Detailed description of the invention [Industrial application field] The present invention relates to a two-phase brushless smoke.

[Summary of the invention]

This invention provides a position detection element by forming a pulse signal similar to the output signal of the position detection element from the induced voltage induced in the first and second stator coils when the rotor magnet rotates. It conducts electricity in both directions in two phases without any need for a two-phase system.

[Conventional technology]

In a conventional two-phase bidirectional current-carrying brushless motor, two Hall elements are used to detect the position of the rotor magnet.
They are arranged with a phase difference of .degree. (electrical angle), and the drive current is controlled based on a predetermined timing formed from the output signal of this Hall element. However, providing a Hall element increases component costs, increases the number of wiring lines,
Installation is a factor in the complexity of position adjustment. Additionally, the space needed to install the Hall element has hindered the miniaturization of brushless motors.

Therefore, brushless motors that do not require a position detection element have been proposed, as shown in, for example, Japanese Patent Application Laid-Open No. 56-33953 and Japanese Patent Application Laid-Open No. 58-172994. In these prior art techniques, the timing of energization switching (phase switching) is defined based on the level relationship of three-phase induced voltages induced in the stator coil by the rotor magnet. In other words, it is necessary to use an induced voltage that is not affected by the voltage generated by the drive current, so the timing of the energized section of one phase is controlled by controlling the induced voltage of the stator coils of the other two phases that are not energized. This is done based on the level relationship being a predetermined level relationship.

[Problem that the invention seeks to solve]

The brushless motor shown in the prior art is of a unidirectional current supply type in which a drive current is supplied to each stator coil in only one direction in order to detect the mutual level relationship of induced voltages. Therefore, the utilization efficiency of the coil is lower than that in both directions, making it difficult to realize a small, high-output brushless motor.

Therefore, an object of the present invention is to provide a brushless motor that does not require a position detection element and is bidirectionally energized.

[Means for solving problems]

The present invention provides first and second fixation coils La arranged with a phase shift of 90'' in electrical angle.

In a brushless motor including Lb and a rotor magnet 23, the zero cross of the first and second induced voltages Ea and Eb induced in the first and second stator coils La and Lb, respectively, when the rotor magnet 23 rotates. first and second pulse signals Pa, Pb having edges corresponding to points, respectively;
and third and fourth pulse signals having a delay of 45 degrees in electrical angle at the steady rotational speed of the rotor magnet 23 with respect to the phases of the first and second pulse signals Pa and Pb, respectively. The pulse signal Ha.

Monomulti 6, D flip-flop 3 forming Hl)
, 4 and third and fourth pulse signals Ha, Hb, the switching is controlled by the first and second stator coils La.
2. Drive pulse generation logic for bidirectionally energizing Lb. This brushless motor includes a switching circuit 1 and a starting pulse generation circuit 7 that generates a pulse signal for the switching circuit 1 at the time of starting.

[Operation] The zero-crossing point of the induced voltage is detected during a period in which no drive current is supplied. The pulse signals Pa and Pb having edges at the detected zero crossing points are transferred to the D flip-flop 3.
．． 4, pulse signals Ha and Hb equivalent to the output signal of the position detection element are formed by delaying the output signal by 45 degrees, and the switching transistors are driven based on the pulse signals Ha and Hb to perform bidirectional conduction. The timing of switching drive is determined by detecting the zero-crossing point of the induced voltage. Near the zero-cross point of the induced voltage, no drive current flows through the stator coil, and timing can be accurately detected from the induced voltage of one stator coil. Further, at startup, since the rotor magnet 23 is stationary, no induced voltage is generated. Therefore, a drive current is forcibly generated by the activation pulse.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, La and Lb indicate stator coils arranged to have a phase difference of 90 degrees in electrical angle. An example of a planar brushless motor to which the present invention can be applied will be described with reference to FIGS. 4 to 7.

In FIG. 4, 21 indicates a rotation axis, and this rotation axis 21
A rotor yoke 22, a rotor magnet 23, and a back yoke 24 are provided, which rotate together with the rotor yoke 22, rotor magnet 23, and back yoke 24. The rotor magnet 23 is magnetized with eight poles, as shown in FIG. 25 and 26 indicate bearings, and 27 indicates a sleeve for arranging the bearings and the stator.

Attach the stator coil La to the sleeve 27 with screws 28 and 29.
.

Lb can be attached. The stator coils La and Lb are laminated, and for example, the stator coil La has the configuration shown in FIG. 6.

The stator coil La consists of eight coils Lal to La8 shaped to have a mechanical angle distribution of 45 degrees. The winding directions of these coils Lal to La8 are aligned so that the radial sides have the same current direction as the adjacent coils, so the torque generation sides are combined to form 8.
There are edges. Although not shown, the other stator coil Lb has the same configuration as the stator coil La, and is disposed below the stator coil La. However, a phase difference of 90° in electrical angle (22.5° in mechanical angle) is provided between stator coils La and Lb. In the conventional brushless morph, in FIG.
0b was required.

In addition to the configuration shown in FIG. 6, the stator coil includes a stator coil La consisting of coils L al and L a2, and coils L b1 . The stator coil Lb consisting of Lb2 may be arranged in the same plane.

Further, in the present invention, the rotor magnet is not limited to the 8-pole magnetized rotor magnet, and a 6-pole magnetized rotor magnet may be used.

At the time of this six-pole magnetization, as shown in FIG. 7B, each coil Lal has a distribution of 120 degrees in mechanical angle.

La2. A stator coil consisting of Lbl and Lb2 is used. Furthermore, the present invention can also be applied to brushless morphs of the same type as cylinders, which are limited to plane-opposed types.

Stator coil La of the brushless morph described above.

Lb is connected to the switching circuit 1 as shown in FIG. As will be described later, the switching circuit 1 is constituted by switching transistors, and the on/off of the switching transistors is controlled by drive pulses P1 to P8 from the drive pulse generation logic 2. Further, the switching circuit 1 is provided with a level comparator, and the level comparator allows the stator coils La, Lb
The levels of the induced voltages Ea and Eb induced in each of the two and the common potential are compared, and when the induced voltage becomes larger than the level of the common potential, it becomes "H" (high level), and when the level relationship is opposite, it becomes "L". Pulse signals Pa and Pb (low level) are generated from the switching circuit 1.

Pulse signals Pa and Pb from the switching circuit l are supplied to the D flip-flop 3.4 as respective data inputs, and an EX-OR gate (exclusive OR gate)
5. The output signal of the EX-OR gate 5 is supplied to the monomulti 6, and the negative output signal of the monomulti 6 is supplied as the clock input of the D flip-flop 3.4. The output terminal of the monomulti 6 is connected to a period of T from the rising edge of the output signal of the EX-OR gate 5.
Thus, a pulse signal with a duty ratio of 50% is obtained.

This time T is set equal to a period of 45° (electrical angle) during steady rotation.

A starting pulse from a starting pulse generation circuit 7 is supplied to the set terminal and reset terminal of the D free knob flops 3 and 4, respectively. When starting the motor, a starting pulse is supplied from the starting pulse generation circuit 7 to the set terminal and reset terminal of the D flip-flops 3 and 4 for a predetermined period of time (for example, 0.1 sec) from the time of hitting and starting. When a starting pulse is supplied to the set terminal of the D flip-flop 3.4, the output signal becomes high level, and when a starting pulse is supplied to the reset terminal, the output signal becomes low level. The starting pulse generation circuit 7 is configured by a logic circuit or a microprocessor.

In the D flip-flop 3.4, the pulse signals Pa,
Pb is delayed by a time T, respectively, and pulse signals Ha and Hb are output from the D flip-flops 3 and 4. This pulse signal Ha and Ha force are supplied to the pulse generation logic 2 for one section. The drive pulse generation logic 2 generates drive pulses P1 to P8 synchronized with the pulse signals Ha and Hb.

FIG. 2 shows an example of the switching circuit 1. As shown in FIG.

Switching circuit 1 includes a PNP transistor and an NP transistor.
N) Four pairs of transistors are provided.

The emitters of the PNP transistors 11, 13, 15, 17 are connected to a power supply terminal 10 to which a positive DC voltage is supplied,
NPN) The emitters of transistors 12, 14, 16, and 18 are grounded. PNP) transistors 11, 13, 1
5.17 base drive pulse PI, P3. P5. P7
are supplied, respectively, and NPN) transistors 12, 14, 16
．． Drive pulse P2.18 is applied to the base of P2. P4. P6. P8 is supplied respectively.

The collector of the PNP transistor 11 and the collector of the NPN transistor 12 are commonly connected, and the common connection point is connected to one end of the stator coil La.

The collector of the PNP transistor 13 and the collector of the NPN transistor 14 are commonly connected, and the common connection point is connected to the other end of the stator coil La.

The collector of the PNP transistor 15 and the collector of the NPN transistor 16 are commonly connected, and the common connection point is connected to one end of the stator coil Lb. .

The collectors of the PNP transistor 17 and the NPN transistor 18 are commonly connected, and the common connection point is connected to the other end of the stator coil Lb.

Drive pulse Pi, P3. P5. During the period when P7 is "L", PNP L-transistors 11, 13, 15.17 are ONL, and drive pulses P2, P4, P6 and P8 are "L", respectively.
H' period NPN) transistors 12.14, 16.1
8 turns on. 0N1 of this switching transistor
The 0FF state defines the current path of the drive current flowing through the stator coils La, La.

Also, both ends of the stator coil La are connected to the level comparator 1.
9, and both ends of the stator coil Lb are connected to the input terminals of the level comparator 20. A pulse signal Pa is obtained from the level comparator 19, and a pulse signal pb is obtained from the level comparator 20.

FIG. 3 shows waveforms of various parts of an embodiment of the present invention. Third
FIG. A shows waveforms of induced voltages induced in stator coils La and Lb, respectively, when the rotor magnet is at a steady rotation speed. This induced voltage waveform is induced by the sinusoidally magnetized rotor magnet 23 and does not include a voltage component generated by the drive current. In FIG. 3A, the solid line waveform shows the waveform of the induced voltage Ea induced in the stator coil La, and the broken line waveform shows the waveform of the induced voltage Eb induced in the stator coil Lb. These induced voltages Ea, E
b has a phase corresponding to the rotational phase of the rotor magnet 23, and also has a phase difference of 90° from each other.

Induced voltages Ea and Eb from level comparators 19 and 20
Pulse signals Pa and Pb (FIG. 3B) having edges coinciding with the respective zero crossing points of are obtained. These pulse signals Pa and Pb are supplied to the EX-OR gate 5,
The OR gate 5 generates the pulse signal shown in FIG. 3C. The level of this pulse signal is inverted every 90°. The monomulti 6 is triggered by this pulse signal, and as shown in the third diagram, a pulse signal whose level is inverted every period T corresponding to 45° is obtained from the negative output terminal of the monomulti 6.

The output pulse signal of the monomulti 6 causes the D flip-flop 3.4 to output a pulse signal Pa.

pb is delayed by a time T, and pulse signals Ha and Hb shown in FIG. 3 are formed. These pulse signals Ha, Hb
is supplied to the drive pulse generation logic 2, and the drive pulse P
1 to P8 are obtained from the drive pulse generation logic 2.

FIG. 3F shows drive pulses P1 to P8. During a period in which the induced voltage Ea is at a high level in the positive direction, the drive pulses P1 and P4 turn on the transistors 11 and 14, and current flows through the stator coil La.

Next, during a period in which the induced voltage Eb is at a high level in the positive direction, the drive pulses P5 and P8 turn on the transistors 15 and 18, and current flows through the stator coil Lb. Next, during a period in which the induced voltage Ea is at a high level in the negative direction, the drive pulses P2 and P3 turn on the transistors 12 and 13, and current flows through the stator coil La. Next, during a period when the induced voltage Eb is at a high level in the negative direction, the drive pulses P6 and P7 turn on the transistors 16 and 17, and the stator coil Lb
A current flows through. In this way, the drive current sequentially flows through the stator coils, and bidirectional energization is performed. The range (±90°) centered on the zero-crossing point of each of the induced voltages Ea and Eb shown in FIG. 3A is a period in which no drive current flows through the corresponding stator coil. Therefore, the rotational phase of the rotor magnet 23 can be accurately detected from the zero cross point. Furthermore, the pulse signals Ha and Hb respectively obtained from the D flip-flops 3.4 are signals equivalent to the output signals of the Hall elements for position detection in a conventional brushless morph.

In addition, when the rotor magnet 23 is stationary, the induced voltages Ea and Eb are not generated, so at startup, a startup pulse is generated for a predetermined period of time to form a two-phase pulse signal similar to the pulse signals Ha and Hb. It is generated from the starting pulse generating circuit 7. This activation pulse forces the rotor magnet 23 into a predetermined rotational phase and sets the rotational direction to a predetermined direction.

〔Effect of the invention〕

According to this invention, a drive signal can be generated without providing a magnetic or optical position detection element. Therefore, the various problems that arise when installing a position detection element (increase in parts cost, increase in the number of wiring, complicated adjustment of position 1, securing space for installation of position detection element) can be solved. .

Further, since the present invention uses a bidirectional energization method, a small-sized, high-output brushless morph can be realized.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of this invention, Fig. 2 is a connection diagram of an example of a switching circuit in an embodiment of this invention, and Fig. 3 is a waveform of each part used to explain the operation of an embodiment of this invention. 4 is a sectional view of an example of a brushless morph to which the present invention can be applied, FIG. 5 is a plan view of an example of a rotor magnet, and FIGS. 6 and 7 are plan views used to explain the stator coil, respectively. It is. Explanation of main symbols in the drawings La, Lb: Stator coil, 1 Niswitching circuit, 2: Drive pulse generation logic, 3.4: D flip-flop, 6: Monomulti, 7: Starting pulse generation circuit, 2
3: Rotor magnet, 19°20 two-level comparator. Agent: Patent Attorney Masatoshi Sugiura, 1-acting circuit Figure 2-7-1 Figure 4

Claims (1)

[Claims] In a brushless motor having first and second stator coils arranged with a phase shift of 90 degrees in electrical angle and a rotor magnet, when the rotor magnet rotates, the first and second stator coils are arranged with a phase shift of 90 degrees in electrical angle. first and second electrodes having edges respectively corresponding to zero-crossing points of first and second induced voltages respectively induced in the second stator coil;
means for forming a pulse signal of 45° in electrical angle at a steady rotational speed of the rotor magnet with respect to the phase of the first and second pulse signals;
means for forming third and fourth pulse signals each having a delay of A brushless motor comprising: a switching circuit; and means for generating a pulse signal to the switching circuit upon startup.