JPH0260493A - Dc brushless motor - Google Patents

Abstract

PURPOSE:To improve the efficiency of drive and controllability by a method wherein the terminal voltage of each phase armature winding and neutral-point voltage are compared, to output a square wave, and the square wave is phase- shifted to produce a rotor-position detecting signal. CONSTITUTION:A DC brushless motor 2 is driven through an inverter 1 from a DC power 12. A plural resistor group 5 are connected in parallel among each phase terminal of said motor 2 and a neutral point, and winding terminal voltage acquired by dividing each phase terminal voltage is input to comparator 7a-7c through semiconductor analog switches 6a-6c. The rectangular wave output of the selected compared neutral-point potential is delayed at an electrical angle 30 deg. by a phase shifting means 8, and changed into a position detecting signal. A first logical operation means 9 preparing the input selecting signals of said switches 6a-6c in response to the position detecting signal and a second logical operation means 10 preparing the drive signal of the inverter 1 are provided. Accordingly, the DC brushless motor is supplied with power through the inverter 1 driven by a driver circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC brushless motor, and more particularly to a DC brushless motor that detects the position of a rotor using the induced voltage of an armature winding.

[Conventional technology]

FIG. 7 shows a conventional DC brushless motor described in, for example, Japanese Unexamined Patent Publication No. 54-136615.

In the figure, (1) is an inverter that converts direct current to pseudo three-phase alternating current, and is connected in parallel to six switching elements connected in a three-phase full bridge (Sirisk in the example in figure 1) and each switching element. It consists of a freewheeling diode. (2) is a DC brushless motor with a synchronous motor structure, consisting of a three-phase armature winding (3) and a permanent magnet rotor (4).

(Ij is a low-pass filter, consisting of a 2 (vA) resistor connected in series to each phase section and a capacitor connected in parallel to one of the resistors.

The armature terminal voltage and neutral point voltage of each phase are connected to inputs of comparators (14a) to (14c) via low-pass filters. Logic circuit (I is a comparator (1)
The comparison results of 4a) to (14c) are input to create a control signal for the inverter (1). ti is a switching element drive circuit, which is configured to perform 0N10FF control of the switching element of the inverter (1) according to the output of the logic circuit α9.

Next, the operation will be explained using FIG. 8.

FIG. 8 is a timing diagram showing operating waveforms of the DC brushless motor shown in FIG. 7.

In FIG. 8, the dot indicates the output waveform of one phase of the inverter (1).

This waveform includes commutation spikes that occur when switching elements switch. Qυ is a voltage waveform induced in the armature winding (3) when the rotor (4) rotates with this drive waveform. The voltage waveform observed at the terminal of the armature winding (3) is a combination of these, and is as shown in (c). This terminal voltage waveform passes through a low-pass filter α and becomes a waveform as shown in (c). (23a) ~
(23c) is the terminal voltage of each phase, and (23a) is the waveform of the neutral point voltage passed through the low-pass filter 03. The switching frequency of this low-pass filter α rise is set sufficiently low with respect to the output fundamental frequency of the inverter, and the terminal voltage waveform becomes approximately sinusoidal and the phase is delayed by 90°. (
The waveforms of each of 23a) to (23c) and (23d) are compared with comparator 04) and the result of waveform shaping is (24a).
) to (24c). This 120°
From the rectangular waves with different phases, the logic circuit α9 generates a drive signal (25a) for the switching element of the inverter (1).
(25f) is created. (25a) to (25c) are 6
Of the switching elements, three drive signals are used for the upper arm, and (25CL) to (25f) are three drive signals used for the lower arm. Based on this drive signal, the switching element drive circuit (II) drives the switching element of the inverter (1), and the voltage waveform shown in (2) is again applied to the DC brushless motor (2), so that the motor continues to rotate.

[Problem to be solved by the invention]

Conventional DC brushless motors are configured as described above, so the time at which the induced voltage of the winding crosses the neutral point potential is delayed by 90 degrees due to the filter, but the crossing occurs due to rotational fluctuations of the single rotor. If the phase of the motor changes frequently, detection cannot be performed in a timely manner, resulting in inaccurate position detection and reduced motor drive efficiency.

In addition, since the waveform that is the combination of the induced voltage and the inverter output voltage is passed through a low-pass filter, the phase of the position detection signal is affected by the phase of the inverter output voltage, and in particular, the commutation spike voltage that occurs when switching elements changes. This is known to be significantly affected, as well as resulting in inaccurate position detection and reduced motor drive efficiency and controllability.

This invention was made to solve the above-mentioned problems, and it is possible to more quickly detect changes in the cross phase due to rotation fluctuations of the two rotors, and the position detection phase is not affected by the output voltage of the inverter itself. The object of the present invention is to obtain a DC brushless motor that enables accurate position detection and improves drive efficiency and controllability of the motor.

[Failure to solve the problem]

The DC brushless motor according to the present invention includes an inverter,
Compare the terminal voltage of the motor driven by this inverter, the terminal voltage of each phase armature winding of this motor, and the neutral point voltage.
After commutation spikes occur in the switching elements of the inverter, each phase armature winding outputs a square wave whose polarity is inverted in the section where it is open from the inverter, and this square wave is phase-shifted to position the rotor. a rotor position detection signal generating means including a first logic operation means for generating a detection signal and a signal for distinguishing between an energized state and an open state of the armature winding from the rotational position detection signal; The apparatus is equipped with a second logic operation means for generating a control signal for the inverter from the position detection signal.

Another method is to provide a filter circuit at the output end of the armature winding of each phase of the motor and compare the filtered terminal voltage with the neutral point voltage.

[Effect]

The DC brushless motor of the present invention generates a signal that distinguishes between a state in which each phase armature winding is disconnected from the inverter after commutation spikes occur in the switching elements of the inverter, and an energized state that includes the commutation spikes. Based on this, a single rotor position signal is generated.
This eliminates the influence of commutation spikes and reduces the phase delay in rotor position signal detection.

By filtering the terminal voltage of each phase armature winding, stable position detection is possible without being affected by harmonics, even in the case of an inverter drive system that includes harmonics, such as PWM.

[Embodiments of the invention]

An example will be described with reference to the drawings. In FIG. 1, (1) is an inverter, and (2) is a DC brushless motor, the basic structure of which is the same as the conventional example explained in FIG. (A bipolar transistor is shown as an example of an inverter switching element.)

(5) is a group of resistors connected in parallel between each phase terminal and the neutral point of the DC brushless motor (2), and divides each phase terminal voltage. (6a) to (6C) are resistance groups (
It is a semiconductor analog switch that uses the winding terminal voltage divided by 5) as one input, and the outputs of the comparators (7a) to (7c) as the other input, and selects and outputs these. Comparators (7a) to (7C) compare the output selected by the semiconductor analog switches (6a) to (6C) with the neutral point potential of the armature winding (3), and output the results in the form of a rectangular wave. . (8) is this comparator (7
It is a phase shift means for delaying the outputs of a) to (7C) by 30 electrical degrees.

This becomes the position detection signal. (9) responds to this position detection signal to the semiconductor analog switches (6a) to (6C).
) first logical operation means for creating an input selection signal of Q
Similarly, l is the inverter (1) according to the position detection signal.
This is second logic operation means for creating a drive signal for the switching element. 0υ is a drive circuit that drives the switching element of the inverter (1) based on the output of the second logical calculation means Ql. α2 is a DC power supply p, an inverter (
1) Supplies power to a DC brushless motor via.

αe is resistance group (5), semiconductor analog switch (6a)
~(6c), Comparator (7a) ~(7c)
, a phase shifting means (8), and a first logical operation means.

Next, the operation will be explained using FIG. 2.

FIG. 2 is a timing diagram showing operating waveforms of the DC brushless motor control device according to the present invention. In FIG. 2, waveforms (1) to (1) are similar to the operating waveforms of the conventional example shown in FIG.

The terminal voltage waveform (c) passes through the resistor group (5) and is divided, but the waveform does not change. Now, if the semiconductor analog switches (6a) to (6C) select the divided terminal voltage waveform in the interval T1, their outputs are inverted during this period as shown in the comparator output waveform (7).

When the selection is switched to the outputs of the comparators (7a) to (7c) in the interval T2, positive feedback is applied, and the comparators (7a) to (7C) maintain their output states.

Furthermore, if the divided terminal voltage waveform is selected again in one section T6, the output is inverted again within this section. That is, semiconductor analog switches (6a) to (6C
) selects the output of the comparators (7a) to (7c) when the output of the inverter (11) is applied to each phase, and selects the terminal voltage waveform when the armature winding terminal is open. If it is controlled as follows, the comparator (7a
) to (7C), the non-inverted input waveform of one phase looks like a wire, and the output looks like (to). Comparator (7a)
The output waveform of ~(7C) is converted to an electrical angle of 3 by the phase shifting means (8).
Waveforms delayed by 0° are shown in (51a) to (31c).

Based on the waveforms (31a) to (31c), the first logic operation means (9) creates selection signals for the semiconductor analog switches (6a) to (6c), such as (32a) to (32c). When the waveform is at the 1-H level, select the divided winding terminal voltage.

When at rLJ level, comparators (7a) to (7c)
Select the output of

FIG. 3 shows an example of the circuit of the logic operation means (9).

For example, to obtain waveform (32a), waveform (51a) and (3
11)) In order to obtain a delay for the time required for the commutation spike to disappear, the inverter (6) is
You can reshape the waveform with . Waveforms (62b) and (32c) are similarly obtained.

Returning to FIG. 2, input selection signals (52a) to (32c)
The input selected by is connected to the comparators (7a) to (7
In the output of C), the section where the armature winding terminal is open is the divided armature winding terminal voltage, which does not contradict the above assumption.

Further, from the waveforms (31a) to (51c), the second logical operation circuit a1 creates drive signals for the switching elements of the inverter fl) such as (55a) to (33f). (5
5a) to (35c) are the signal waveforms that drive the switching elements of the upper arm, and (XSa) to (s3f) are the signal waveforms that drive the switching elements of the lower arm, and the elements are turned on when the level is "H".

It shows that it is OFF when it is at rLJ level.

FIG. 4 shows an example of the circuit configuration of the second logic operation means 01.

For example, to obtain the waveform (+5a), the logic of the waveform (31b) may be inverted with an inverter (to), and the logical product of this output and (51a) may be taken. Waveforms (s3b) to (ssr) are obtained in the same manner.

FIG. 5 is a circuit configuration diagram of a DC brushless motor showing another embodiment of the present invention, where αη represents a resistor connected in parallel between each phase terminal and the neutral point of the DC brushless motor (2), and This is a filter circuit connected in parallel with one resistor, which divides and filters each phase terminal voltage. The cutoff layer wave number of this filter circuit is set so as to have sufficient attenuation with respect to the carrier frequency of the PWM waveform, and to have no phase lag with respect to the output fundamental frequency of the inverter.

FIG. 6 is a timing diagram showing the operating waveforms of the control device for the DC brushless motor shown in FIG. 5, and ① to (c) in FIG.
A case where the drive is performed using a PWM type inverter is shown. The waveform obtained by combining these terminal voltage waveforms and passing through the filter circuit αη is (to), the harmonics caused by the PWM signal are almost removed, and the waveforms after t23 are the same as those shown in FIG.

In addition, in the above two embodiments, a bipolar transistor is shown as the switching element of the inverter (1), but
In addition to MOS-FETs and IGBTs (7), X switching elements may also be used. In addition, as an example of the first and second logic operation means, a circuit configured with hardware using logic operation elements etc. is shown, but it is also possible to realize it with software using a microcomputer etc., and the above implementation is possible. The same effect as the example can be obtained.

〔Effect of the invention〕

This invention compares the terminal voltage and neutral point voltage of an inverter, an electric motor driven by this inverter, and each phase armature winding of this motor, and calculates the voltage of each phase after a commutation spike occurs in a switching element of the inverter. A square wave with inverted polarity is output in the section where the armature winding is open from the inverter.

A first logic operation means for phase-shifting this square wave to make a rotor position detection signal, and generating a signal for distinguishing between an energized state and an open state of the armature winding from this rotor position detection signal. a second rotor position detection signal generating means for generating a control signal for the inverter from the rotor position detection signal;
Since the configuration is equipped with a logic operation means, the influence of the voltage output by the inverter itself can be removed to obtain the position detection signal.The position detection accuracy is improved, and the delay is reduced, so the rotational fluctuation of the rotor is reduced. Even if the cross phase between the armature winding terminal voltage and the neutral point potential changes, a position detection signal that more quickly follows the change can be obtained, improving position detection accuracy and, in turn, improving motor drive efficiency and controllability. Effects can be obtained.

In addition, by providing a filter circuit at the output end of each phase armature winding and comparing the filtered terminal voltage with the neutral point voltage, even if the inverter uses a PWM drive waveform, the filter circuit provides a carrier. This has the effect of stably detecting the position of the rotor.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing a DC brushless motor according to an embodiment of the present invention, FIG. 2 is a timing diagram showing operating waveforms of a DC brushless motor control device according to an embodiment of the invention, and FIG. FIG. 4 is a circuit diagram showing an embodiment of the first logic operation means, and FIG. 4 is a circuit diagram showing an embodiment of the second logic operation means. FIG. 5 is a circuit configuration diagram showing a DC brushless motor according to another embodiment of the present invention, FIG. 6 is a timing diagram showing operating waveforms of the control device, and FIG. 7 is a circuit configuration diagram showing a conventional DC brushless motor. , FIG. 8 is a timing diagram showing operating waveforms of a conventional DC brushless motor control device. In the figure, (1) is an inverter, (2) is an electric motor, (
3) is the armature winding, (9) is the first logic operation means, OI
(US is rotor position signal generating means. αη is a filter circuit. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) Compare the terminal voltages and neutral point voltages of the inverter, the motor driven by this inverter, and the armature windings of each phase of this motor, and determine the A square wave with inverted polarity is output in the section where each phase armature winding is open from the inverter, and this square wave is phase-shifted to become a rotor position detection signal, and from this rotor position detection signal. Rotor position detection signal generation means including a first logic operation means for generating a signal to distinguish between an energized state and an open state of the armature winding; A DC brushless motor equipped with two logical calculation means. (2) A DC brushless motor according to claim 1, characterized in that a filter circuit is provided at the output end of the armature winding of each phase of the motor, and the filtered terminal voltage and neutral point voltage are compared.