JP3240789B2 - Brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit for driving a multi-phase brushless motor without a sensor.

[0002]

2. Description of the Related Art In recent years, small DC motors have been recognized for their good controllability not only in the field of sound but also in the field of information and industry, and their applications are expanding at an extremely rapid pace. Among them, a brushless motor has no contact portion such as a brush and a commutator and has an advantage of a long life, and therefore its use as an industrial motor in which reliability is particularly important is expanding.

Conventionally, a brushless motor has a sensor (magnetic detection element or the like) for detecting the rotational phase of a rotor, and an output signal of the sensor is electrically processed to select a driving coil to which a current flows and to supply an exciting current. In general, it is composed of a driving circuit. That is, a three-phase drive motor has three magnetic detection elements and a drive circuit, and a five-phase drive motor has five magnetic detection elements and a drive circuit (not shown). Also, reduce the number of magnetic sensing elements to 2
There is also a method of driving a three-phase motor by itself, or combining two outputs with appropriate coefficients to drive a multi-phase motor.

[0004]

However, in the former method in the above-mentioned prior art, the number of magnetic detecting elements increases in correspondence with the number of phases for a polyphase brushless motor, which is disadvantageous in cost. In the latter method, FIG.
As shown in the figure, the position detection signals A and B of a magnetic detection element such as a Hall element usually contain a third harmonic component of about 10% with respect to the fundamental sine wave, and the position synthesized by this influence is obtained. The signal waveform C is distorted, causing a phase error, resulting in a non-uniform phase difference between the phases, causing torque unevenness. In order to solve this, it is sufficient to reduce the third harmonic component of the position detection signal by sine-wave magnetizing the magnet, but there is a problem that the torque is reduced.

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a sensorless drive brushless motor capable of performing position signal processing in a circuit and simplifying wiring without causing torque reduction or torque unevenness. It is intended to provide.

[0006]

Means for Solving the Problems A substantially triangular two-phase FG
A line element, an FG signal amplifying circuit for amplifying an FG signal generated in the two-phase FG line element, a position signal synthesizing circuit for synthesizing the two-phase outputs of the FG signal amplifying circuit with appropriate coefficients. A distribution circuit for calculating the output of the position signal synthesis circuit and distributing it to each phase; a drive circuit for driving the motor winding; a start circuit for generating a start signal at the time of start; an output of the position signal synthesis circuit and the start And a switching circuit for switching the output of the circuit, and a position signal having a small third harmonic component is obtained by the above-described substantially triangular two-phase FG element.

[0007]

According to the above means, after being activated by the activation circuit, the position signal waveforms for the two phases having a small third harmonic component are calculated with appropriate coefficients, and the position signals for the remaining phases are synthesized. . The position signal synthesized in this manner does not include a phase error and prevents uneven torque. Further, it is not necessary to magnetize the magnet with a sine wave.

[0008]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the present invention. Reference numeral 1 denotes a starter circuit for forcibly sending a drive signal in the case of a motor having no active position detecting means such as a Hall element. is there. Numeral 2 denotes a two-phase FG, which is an FG pattern composed of two line elements having a phase difference and arranged opposite to the rotor magnet. Reference numeral 3 denotes an FG signal amplifying circuit for amplifying a signal induced in the two-phase FG disposed opposite to the rotor magnet to a predetermined level. Numeral 4 denotes a position signal synthesizing circuit for calculating the signals m and n obtained by the FG signal amplifying circuit by applying appropriate coefficients P and Q to synthesize position signals for driving all phases. Reference numeral 5 denotes a switching circuit. When the motor starts to rotate by the starting circuit and the signals m and n are induced in the two-phase FG and the output of the FG signal amplifying circuit reaches a predetermined value, the output from the position signal synthesizing circuit is output. Is a circuit that switches to drive the motor. Reference numeral 6 denotes a distribution circuit which appropriately distributes the position signal from the starting circuit or the position signal synthesizing circuit to each phase. 7 is a drive circuit for driving the 8 coils. Reference numeral 9 denotes a speed control circuit that controls the drive circuit using the output signal of the FG signal amplification circuit to maintain the rotation speed of the motor.

FIG. 2 is an expanded view of the two-phase FG2 of FIG.
A substantially triangular pattern m phase and n phase are arranged with a phase difference so as to face the magnetized surface of the magnet. n1
Ｎn5 indicates a state in which the n phase has a phase difference of 30 to 150 ° in electrical angle with respect to the m phase.

FIG. 3 shows an example of the configuration of the position signal synthesizing circuit 4 of FIG. 1. The m-phase and n-phase output signals of the FG signal amplifying circuit are appropriately represented by resistors (Table 1). The configuration is such that the coefficients P and Q are given, combined by an adder circuit, and drive signals for each phase are obtained.

[0012]

[Table 1]

For example, in the case of three-phase driving, the A-phase
The m-phase output signal of the signal amplifying circuit is directly connected to the resistors 40, 4
1 and 42 and an adder 43. In the case of the B-phase, m
When the phase and n-phase output signals are introduced into an addition circuit composed of resistors 44, 45, 46 and 47 and an adder 48, the resistances 44 and 45 are -2 times and 1.732 times the resistance 40. (In the case of a negative coefficient, an m-phase or n-phase negative-phase signal is used.) Similarly, in the case of the C-phase, when the m-phase and n-phase output signals of the FG signal amplifying circuit are introduced into an adding circuit composed of the resistors 49, 50, 51 and 52 and the adder 53, the resistors 49 and 50 is configured to have a value of 1 time and -1.732 times the value of the resistor 40. In this way, phase A, phase B and C
A drive signal having a phase difference of 120 ° is obtained for each phase.

The operation of the present invention configured as described above will be described. Since the motor of the present invention does not have an active position detecting means such as a Hall element, the motor is forcibly started by the starting circuit 1 at the time of starting. Starting circuit 1
As a result, the rotation speed gradually increases, and when the rotation speed reaches a certain predetermined rotation speed, the switching circuit 5 operates to cut off the position signal from the starting circuit 1 and switch to the position signal from the FG.

When the motor is rotating, an induced voltage is generated in the FG wire element facing the rotor magnet. At this time, the output of the FG pattern includes the third harmonic when the magnet is fully magnetized in order to enhance the efficiency of the motor, since the magnetized pattern of the magnet is almost faithfully reflected in the normal rectangular pattern. Therefore, the third harmonic was removed by forming a substantially triangular pattern as shown in FIG. That is, since the substantially triangular pattern includes a component having a phase opposite to the third harmonic with respect to the basic sine wave, the third harmonic of the fully magnetized magnet can be canceled. Further, in the case of a two-phase arrangement in a rectangular pattern, two
Although a large output cannot be obtained because of the arrangement in stages, it is possible to arrange them in an approximately triangular pattern as shown in FIG. It fits in an arc and gives a large output.

The two-phase sine wave FG signal (m-phase, n-phase) obtained in this manner is amplified by the FG signal amplifier circuit 3 and guided to the position signal synthesis circuit 4. In the position signal synthesizing circuit 4, as shown in FIG. 3, the m-phase and n-phase output signals are given an appropriate coefficient represented by (Table 1) by a resistor and synthesized by an adder circuit. That is, for example, when the phase difference between the two-phase FG is 30 ° in electrical angle in the three-phase drive, the B-phase is (Equation 1) for the resistor 40 in the circuit for synthesizing the A-phase drive signal.
The resistance C is obtained by adding the resistance 44 to −2 times and the resistance 45 to 1.732 times, and adding the resistance 49 to 1 time and the resistance 50 to −1.732 times by the adders 48 and 53. (At this time, in the case of a negative coefficient in the equation, an m-phase or n-phase reverse-phase signal is used.) Similar results can be obtained with other phase numbers and phase differences by using the coefficients shown in Table 1.

[0017]

(Equation 1)

The sinusoidal position signal obtained in this manner is introduced into the distribution circuit 6 and allocated as a position signal corresponding to each phase, and the drive circuit 7 for driving the coil is provided.
To drive the motor.

Further, a speed control circuit for controlling the driving circuit by frequency-to-voltage conversion (FV conversion) of the signal from the FG signal amplification circuit 3 may be provided.

FIG. 4 shows an embodiment for preventing a problem such as step-out when the starting circuit 1 sends a drive signal independently of the movement of the motor at the time of starting. Reference numeral 10 denotes a voltage controlled oscillator (VCO) which oscillates at a frequency proportional to a given voltage. Reference numeral 11 denotes a ring counter which outputs a phase shift in a ring shape by the oscillation pulse of the VCO. 12 is frequency-voltage conversion (FV
The conversion circuit converts the signal from the FG signal amplification circuit 3 into a frequency-voltage conversion (FV conversion) to control the VCO. At startup, the VCO is biased to oscillate at a frequency that the motor can follow. Therefore, the motor starts to rotate at this frequency upon receiving a drive signal via the ring counter, and the two-phase FG2
, An induced voltage is generated in the FG signal amplification circuit 3. This voltage is subjected to FV conversion by the FV conversion circuit to control the VCO.

[0021]

As described above, according to the present invention, a position detecting element such as a Hall element is used by selecting a phase difference and a coefficient of a substantially triangular two-phase FG as shown in Table 1. The number of wirings is reduced, the number of parts is reduced, the space can be secured, and the motor can be downsized, and stable rotation without phase error of the position signal can be obtained. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram of a drive circuit of a brushless motor according to an embodiment of the present invention.

FIG. 2 is a pattern explanatory view of a two-phase FG of a brushless motor according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a position signal synthesizing circuit of a brushless motor according to an embodiment of the present invention.

FIG. 4 is a block diagram of a starting circuit of the brushless motor according to one embodiment of the present invention.

FIG. 5 is an explanatory diagram of position signal synthesis in a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 start circuit 2 two-phase FG 3 FG signal amplifier circuit 4 position signal synthesis circuit 5 switching circuit 6 distribution circuit 7 drive circuit 8 coil 9 speed control circuit

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02P 6/16

Claims (3)

(57) [Claims] 1. A two-phase FG line element having a substantially triangular shape, an FG signal amplifier circuit for amplifying an FG signal generated in the two-phase FG line element, and a two-phase output of the FG signal amplifier circuit having an appropriate coefficient. A position signal synthesizing circuit, a distribution circuit for calculating the output of the position signal synthesizing circuit, and distributing the signals to the respective phases; a driving circuit for driving the motor winding; and a starting circuit for generating a starting signal at the time of starting. And a switching circuit for switching between the output of the position signal synthesizing circuit and the output of the starting circuit. 2. A voltage controlled oscillator (VCO) for generating a start signal at the time of start, a ring counter for converting an output of the VCO into a drive signal, and a frequency-voltage (FV) conversion circuit. The brushless motor according to claim 1. 3. The brushless motor according to claim 1, wherein the rotation direction is detected using an FG signal (90-degree phase) generated in the two-phase FG wire element.