JPH05111286A - Driver for brushless motor - Google Patents

Abstract

PURPOSE:To obtain a correct position detection signal even when a voltage induced in the stator winding of a brushless motor is shifted from the rotational position of stator. CONSTITUTION:A position detection signal is obtained based on comparison of terminal voltages UV, VV, WV of the stator windings 32U, 32V, 32W in a brushless motor 31 with a reference voltage VR in a reference voltage generating circuit 44 connected with a variable resistor 47. When vibration and noise levels of the brushless motor 31 are high, the variable resistor 47 is operated to regulate the reference voltage VR.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor driving device for obtaining a position detection signal based on an induced voltage induced in a stator winding.

[0002]

2. Description of the Related Art For example, as a drive motor for a compressor of a refrigerator or an air conditioner, a brushless motor has come to be adopted because of its ease of controlling the rotation speed in the case where the capacity of the compressor needs to be varied. In particular, the relative position of the stator winding and the permanent magnet type rotor is induced in the stator winding without using a position sensor such as a Hall element because of the characteristics such as a small number of drawn wires. A position sensorless system that uses an induced voltage for detection has been adopted.

FIG. 6 shows a conventional brushless motor driving device of this type.

That is, 1 is a DC power source, 2 is a drive circuit for energizing the stator windings 3U, 3V and 3W of the brushless motor 3, and 4 is terminal voltages UV and VV of the stator windings 3U, 3V and 3W. And 5 is a detection circuit for detecting WV, 5 is a reference voltage generation circuit having a reference voltage VR which is 1/2 the voltage E of the DC power supply 1, and 6 is a control circuit.

The control circuit 6 compares the terminal voltages UV, VV and WV from the detection circuit 4 with the reference voltage VR from the reference voltage generation circuit 5 to determine the stator windings 3U and 3V.
And a zero cross point of the induced voltage induced in 3 W is detected to obtain a phase signal, these phase signals are phase-shifted by a predetermined angle to form a position detection signal, and the transistor of the drive circuit 2 is based on these position detection signals. It is designed to output an energization timing signal to be applied to the base.

[0006]

In the conventional structure, the stator windings 3U, 3V and 3W are formed due to variations in the magnetic flux of permanent magnets in the permanent magnet type rotor 3R, variations in assembly, or differences in the characteristics of the transistors in the drive circuit 2. When the waveform of the induced voltage induced in the control circuit 6 varies, the control circuit 6 controls the terminal voltages UV, VV and WV and the reference voltage VR.
When and are compared, the correct zero-cross point of the induced voltage cannot be detected.

As a result, the obtained phase signal is the rotor 3R.
Therefore, the position detection signal also shifts, so that the energization timing of the transistors of the drive circuit 2, that is, the stator windings 3U, 3V and 3
The energization timing for W is shifted.

If the energization timings for the stator windings 3U, 3V and 3W are deviated, the torque ripple becomes large and the vibration and noise unsuitable for the compressor drive motor become large.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve torque even if the permanent magnets of the rotor have magnetic flux variations or assembly variations or the switching elements of the output means have different characteristics. It is an object of the present invention to provide a drive device for a brushless motor that can reduce ripples and thus vibration and noise as much as possible.

[0010]

SUMMARY OF THE INVENTION The present invention provides a brushless rotor having a permanent magnet type rotor and a stator having a plurality of phases of stator windings that act a magnetic field to impart a rotational force to the rotor. In the motor, detection means for detecting the terminal voltages of the stator windings of the plurality of phases are provided, reference voltage generation means for generating a reference voltage is provided, and the reference voltage from the reference voltage generation means and the detection means are provided. Control means for obtaining a position detection signal based on a comparison with a terminal voltage from the controller and outputting an energization timing signal based on the position detection signal, and energizing the stator winding based on the energization timing signal from the control means. Is characterized in that it is provided with an output means for controlling the control voltage and an adjusting means for adjusting the reference voltage of the reference voltage generating means.

[0011]

According to the brushless motor driving apparatus of the present invention, the adjusting means adjusts the reference voltage of the reference voltage generating means when vibration and noise are large. When the deviation is adjusted, the current flowing in each stator winding in each energization time period becomes substantially constant, and therefore the torque ripple due to the variation in energization timing is reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will now be described with reference to FIGS.
Will be described.

First, the overall structure will be described with reference to FIG. The positive and negative terminals of the DC power supply 11 are connected to the input terminals 14 and 15 of the drive circuit 13 via the current detection resistor 12 on the negative terminal side.

The drive circuit 13 serving as output means has an input terminal 1
NPN type transistors 16 to 18 and 19 to 21 which are switching elements are connected between 4 and 15 by three-phase bridge connection. Diodes 23 to 27 are connected in parallel to the transistors 16 to 21, respectively. The common connection point of the transistors 16 and 19 is connected to the output terminal 28, the common connection point of the transistors 17 and 20 is connected to the output terminal 29, and the transistor 1
The common connection point of 8 and 21 is connected to the output terminal 30.

The brushless motor 31 includes a stator 3 having U, V and W phase stator windings 32U, 32V and 32W.
2 and a permanent magnet type rotor 33. Then, one terminal of the stator windings 32U, 32V, and 32W is commonly connected, and each of the other terminals is the output terminal 2 of the drive circuit 13.
8, 29 and 30, respectively.

The voltage dividing circuit 34 serving as detecting means is composed of resistors 35 to 40. Between the output terminals 28, 29 and 30 and the negative terminal of the DC power source 11, a series circuit of resistors 35 and 36 and a resistor are provided. Series circuit of 37 and 38 and resistors 39 and 4
It is configured by connecting a series circuit with 0. Then, the resistors 35 and 36, the resistors 37 and 38, and the resistors 39 and 40
The respective common connection points are used as detection terminals 41, 42 and 43.

Reference voltage generating circuit 4 serving as reference voltage generating means
4 has resistors 45 and 46 for voltage division. And
Between the positive terminal and the negative terminal of the DC power supply 11, a series circuit of a resistor 45, a variable resistor 47 and a resistor 46 which are adjusting means is connected.

The resistors 35, 37 and 3 of the voltage dividing circuit 34 are
The resistance value ratio between 9 and the resistances 36, 38 and 40 is set to K: 2 (where K is a natural number), and the resistance value ratio between the resistance 45 and the resistance 46 of the reference voltage generating circuit 44 is (K + 1): 1. Is set to.

The control circuit 48 as a control means is constituted by including a microcomputer, and its three input ports are connected to the detection terminals 41 to 43, and the other one input port is connected to the mover 47a of the variable resistor 47. , The other input port is connected to the input terminal 15, and the six output ports are connected to the bases of the transistors 16 to 21, respectively.

Next, the operation of this embodiment will be described with reference to FIGS.
It will be explained with reference to also.

(1) Stator windings 32U, 32V and 32
When the induced voltage induced in W is normal.

While the rotor 33 is rotating, the terminal voltages of the stator windings 32U, 32V and 32W are as shown in FIG.
As shown in (a), (b) and (c), UV, VV and WV are obtained, and these are divided by the voltage dividing circuit 34 and detected as detection voltages UVa, VVa and WVa, and these are detected. It is input to the control circuit 48. The power supply voltage E of the DC power supply 11 is divided by the reference voltage generation circuit 44 and output as the reference voltage VR, which is the control circuit 48.
Entered in.

The control circuit 48 controls these detection voltages UV.
a, VVa and WVa are compared with the reference voltage VR to detect the zero cross point of the induced voltage induced in the stator windings 32U, 32V and 32W. In this case, the resistors 35 and 37
Since the resistance value ratio between the resistors 39 and 39 and the resistors 36, 38 and 40 is K: 2, the detection voltages UVa, VVa and WVa are 2UV / (K + 2), 2VV / (K + 2) and 2WV, respectively.
/ (K + 2). Further, since the resistance value ratio between the resistors 45 and 46 is (K + 1): 1, the reference voltage VR is E /
(K + 2). Therefore, the control circuit 48 consequently has the terminal voltages UV, VV and WV and 1/2 of the power supply voltage E.
Will be compared with the reference voltage VR (= E / 2).

As shown in FIGS. 2A, 2B and 2C, the control circuit 48 detects a cross point between the terminal voltages UV, VV and WV and the reference voltage VR (= E / 2). By detecting the zero crossing point of the induced voltage induced in the stator windings 32U, 32V, and 32W, the phase signal DSU, as shown in (d), (e), and (f) of FIG. Obtain DSV and DSW. Then, the control circuit 48 calculates a time corresponding to an electrical angle of 30 degrees from the phase signals DSU, DSV, and DSW, and shifts the phase signals DSU, DSV, and DSW by that amount, and thus, FIG.
Position detection signals PSU, PSV and PSW are obtained as shown in (g), (h) and (i).

The control circuit 48 receives these position detection signals P
SU, PSV and PSW are logically converted to obtain six base signals which are energization timing signals, and these are supplied to the drive circuit 13
To turn on and off the transistors 16 to 21 in order, and the stator winding 3
Energize 2U, 32V and 32W to rotate the rotor 33.

In this case, the currents flowing through the stator windings 32U, 32V and 32W are as shown in FIGS. 2 (j), (k) and (l).
As shown in FIG. 2, IU, IV, and IW, and the torque generated by the stator windings 32U, 32V, and 32W of each phase is as shown in FIG. 2 (m). The ripple of the instantaneous torque is small. Then, when the waveform of the current flowing through the input terminal 14 of the drive circuit 13 at this time is measured, it becomes as shown in FIG. 4, and the time during which the current corresponding to each stator winding 32U, 32V and 32W flows (energization time) is It is substantially constant at T0, and the crest value is also constant below the predetermined level L.

(2) Stator windings 32U, 32V and 32
When the induced voltage induced in W is in an abnormal state.

When the magnetic fluxes of the permanent magnets in the rotor 33 are varied, or the assembling is varied, or the characteristics of the transistors 16 to 21 are varied, the terminals of the stator windings 32U, 32V and 32W are changed. The voltages (induced voltages) UV, VV and WV are as shown in FIG.
As shown in FIGS. 2B and 2C, the waveforms in the normal state shown in FIGS. 2A, 2B and 2C are different.

Therefore, even if the terminal voltages UV, VV and WV are compared with the reference voltage VR, the respective stator windings 32U, 32
The zero cross point of the induced voltage induced in V and 32 W cannot be correctly detected, and the phase signal DSU,
As shown in FIGS. 3D, 3E, and 3F, DSV and DSW are deviated from the normal state shown in FIGS. 2D, 2E, and 2F, and the position detection signal PSU, P
SV and PSW are also deviated from the normal state shown in FIGS. 2 (g), (h) and (i) as shown in FIGS. 3 (g), (h) and (i).

As a result, the position detection signals PSU, PSV and PSW deviated from the rotational position of the rotor 33 in this way.
When the transistors 16 to 21 of the drive circuit 13 are turned on and off by the energization timing signal formed based on (FIGS. 3 (g), (h) and (i)), the stator windings 32U, 32V of each phase and The currents IU, IV and IW flowing through 32W are out of the position of the rotor 33 as shown in FIGS. 3 (j), (k) and (l). Therefore, the torque generated by each of the stator windings 32U, 32V, and 32W is as shown in FIG. 3 (m), and the instantaneously generated torque has a large ripple as shown in FIG. 3 (m). It may cause vibration and noise.

In this case, when the current flowing through the input terminal 14 of the drive circuit 13 is measured, it becomes as shown in FIG. 5, and the current flowing time corresponding to each stator winding 32U, 32V and 32W is T1, T2, As T3, T4, ... differ, the crest values also vary, and there are cases in which the level is above the predetermined level L. When the current flowing through the input terminal 14 becomes equal to or higher than the predetermined level L, a limiter (not shown) acts to limit the current to the predetermined level L.
Therefore, when the limiter acts in this way, the maximum generated torque becomes small, and it becomes necessary to design the drive circuit 13 in a large size in order to obtain the required torque.

Thus, as shown in FIG.
When the induced voltage induced in U, 32V, and 32W is in an abnormal state, the brushless motor 31 is driven at a constant torque and a constant speed, the current flowing through the input terminal 14 of the drive circuit 13 is measured, and the reference voltage is measured. The movable element 47a of the variable resistor 47 connected to the generation circuit 44 is operated to adjust the reference voltage VR up and down, and the current flowing through the input terminal 14 is changed as shown in FIG.
4 to the state of FIG. 4, that is, the current flowing times to the stator windings 32U, 32V and 32W of the respective phases are substantially constant and the crest values are substantially constant and equal.

As described above, according to this embodiment, since the variable resistor 47 is connected to the reference voltage generating circuit 44 so that the reference voltage VR can be changed and adjusted, the magnetic flux is generated in the permanent magnet of the rotor 33 of the brushless motor 31. There is a variation or an assembly variation, or the drive circuit 13
Even if the induced voltage induced in the stator windings 32U, 32V and 32W is deviated from the rotational position of the rotor 33 due to the difference in the characteristics of the transistors 16 to 21 of FIG. It can be adjusted by the operation of.

Therefore, the stator windings 32U, 32V of each phase are
The current flowing during each energization time period of 32 W and 32 W is substantially constant and the torque ripple is reduced, so that the generation of vibration and noise can be minimized, and the peak value of each current is equal to or higher than a predetermined level L. Therefore, there is no problem that the maximum generated torque becomes small due to the action of the limiter in a specific energization time zone.

In the above embodiment, the reference voltage generating circuit 4
4 is connected to the variable resistor 47 as the adjusting means, but instead, the reference voltage may be adjusted by software inside the control circuit 48. In this case, the control circuit 48 causes the adjusting means to adjust. Will also serve.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and it is needless to say that the present invention can be appropriately modified and implemented without departing from the scope of the invention.

[0037]

As described above, the brushless motor driving apparatus of the present invention obtains the position detection signal based on the comparison between the reference voltage from the reference voltage generating means and the terminal voltage of the stator winding. In this case, since the adjusting means for adjusting the reference voltage of the reference voltage generating means is provided, the torque ripple can be reduced even if the induced voltages induced in the stator windings are different. It has an excellent effect that the generation of vibration and noise can be minimized.

[Brief description of drawings]

FIG. 1 is an electrical configuration diagram showing an embodiment of the present invention.

[Figure 2] Waveform diagram of each part in normal state

FIG. 3 is a waveform diagram of each part in an abnormal state

[Fig. 4] Current waveform diagram in normal state

FIG. 5: Current waveform diagram in abnormal state

FIG. 6 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

In the drawing, 11 is a DC power supply, 13 is a drive circuit (output means), 16 to 21 are transistors (switching elements), 31 is a brushless motor, 32 is a stator, 32
U, 32V and 32W are stator windings, 33 is a rotor, 3
4 is a voltage dividing circuit (detection means), 44 is a reference voltage generation circuit (reference voltage generation means), 47 is a variable resistance (adjustment means),
Reference numeral 48 represents a control circuit (control means).

Claims (1)

[Claims] 1. A brushless motor comprising: a permanent magnet type rotor; and a stator having stator windings of a plurality of phases that act a magnetic field to give a rotational force to the rotor.
Detection means for detecting the terminal voltage of each of the stator windings of the plurality of phases, reference voltage generation means for generating a reference voltage, and comparison of the reference voltage from the reference voltage generation means with the terminal voltage from the detection means. A control means for obtaining a position detection signal based on the position detection signal and outputting an energization timing signal based on the position detection signal; an output means for controlling energization of the stator winding based on the energization timing signal from the control means; An apparatus for driving a brushless motor, comprising: an adjusting unit that adjusts the reference voltage of the reference voltage generating unit.