CN100459406C - Brushless motor start method, drive device, and refrigerator - Google Patents

Abstract

The present invention discloses a brushless motor start method, which includes the following steps: an initial position moving step(ta to tc) for rotating/moving a rotor to a predetermined initial position by DC excitation; forcible commutation step(tc to td) for performing electrical connection according to a predetermined electrical connection pattern so as to rotate the rotor from the initial position; and a shift step(td) for shifting to the rotation control based on the estimated rotor rotation position. The initial position moving step includes a first step(ta to tb) for increasing the DC excitation current up to a first current value so that the rotor is rotated/moved to a preparatory excitation position apart from the initial position and a second step(tb to tc) for increasing the DC excitation current up to a second current value which is higher than the first current value so that the rotor is rotated/moved from the preparatory excitation position to the initial position.

Description

Starting method and driving device of brushless motor, and refrigerator

technical field

The present invention relates to a starting method and a driving device of a brushless motor including a stator having coils and a rotor having permanent magnets, and a refrigerator using the brushless motor as a driving unit of a compressor.

Background technique

Conventionally, reciprocating compressors have been used in refrigeration cycles such as refrigerators and air conditioners. Now it has become mainstream to drive such compressors with DC brushless motors.

This brushless motor consists of a stator wound with multi-phase coils, and a multi-pole rotor with permanent magnets. It is difficult to install a position sensor inside the compressor due to high temperature and high pressure. Therefore, a sensorless drive device is used which detects the rotational position of the rotor based on the current or voltage of the coil, and controls the rotation based on the detected position.

This sensorless drive device cannot detect the rotor position when the brushless motor is stopped. Therefore, the sensorless driving device does not use the position information when starting the brushless motor, but makes the current flow through the coil according to the preset energization mode, accelerates the rotor to a specified speed and then performs forced commutation. In this case, in order to prevent the rapid rotational movement of the rotor, for example, as disclosed in Japanese Laid-Open Patent Publication No. 1290, 1961, the forced commutation is performed after the rotor is rotationally moved to the initial position by DC excitation.

Specifically, the sensorless drive device gradually increases the DC excitation current to rotate and move the rotor to the initial position. Then, when it rises to a predetermined current value, it is considered that the rotor rotates and moves to the initial position, and the above-mentioned forced commutation is shifted to without changing the current value.

According to this starting method, since the sudden change of the current value can be reduced, the sudden rotational movement of the rotor can also be reduced, and it is possible to easily prevent out-of-synchronization at the time of starting.

However, when the stopped rotor is rotated to the initial position by DC excitation, sometimes it cannot be rotated to the initial position due to the direction of the generated magnetic field and the positional relationship between the magnetic poles, or it may not be rotated to the initial position when it is rotated from DC excitation. Shortly before the forced commutation, the rotor rotates sharply and loses synchronization. This phenomenon will be described below with reference to FIGS. 14 to 16 .

These figures schematically show the relationship between the piston position in the reciprocating compressor and the rotor position of the 4-pole brushless motor. A crankpin 202 is fixed to the rotor 201 at a position offset from the rotation axis. The crank pin is connected to a piston 205 in a cylinder chamber 204 via a connecting rod 203 .

The initial position X of the rotor 201 corresponds to the S pole of the rotor 201. The crank pin 202 installed on the rotor 201 is in the state of X1 or X2 in the figure. When the DC excitation of the stator coil generates an N-pole magnetic field along the X1 direction and the X2 direction, the rotor 201 turns to a certain direction of the positions X1 and X2. Rotating in the CW direction in FIG. 14, the position of the crank pin 202 (hereinafter referred to as "rotor position") moves to the initial position X1.

On the contrary, as shown in FIG. 15 , when the crank pin 202 corresponding to the S pole stops at the middle point Z between the positions X1 and X2, even if DC excitation is performed to increase the coil current to a predetermined current value, due to the magnetic force The balance rotor 201 cannot rotate and move.

Even in this case, when the sensorless drive device increases the DC field current to a predetermined current value, it assumes that the rotor 201 stops at the initial position X1 or X2, and shifts to forced commutation. Therefore, when using forced commutation to make the rotor 201 turn to the CW direction, for example, just after moving to the forced commutation, the magnetic field of the N pole is from the X1-X2 direction (indicated by a dotted line) to the X3-X4 direction (indicated by a two-dot dash line). ) moves, and the rotor 201 stopped at the intermediate point Z is momentarily drawn in the direction (CCW direction) of the position X2 (X4).

As a result, the rotation direction of the magnetic field is opposite to the rotation direction of the rotor 201 immediately after the forced commutation, and the synchronization is lost. In addition, even if there is no loss of synchronization, the rotor 201 vibrates due to a sudden change in speed, and an abnormal sound may be generated due to the collision of the frame (not shown) holding the rotor 201 and the airtight casing of the compressor.

In addition, as shown in FIG. 16, there may be a case where the stop position of the rotor 201 is a position R near the middle point Z. As shown in FIG. In this case, the rotor 201 stops due to the magnetic force balance shortly after the DC excitation is started. But when the current is raised to 1.7A and above, the magnetic force acting between the magnetic field (N pole) at the position X1 and the S pole of the rotor 201 and the magnetic force acting on the magnetic field (N pole) at the position X2 and the S pole of the rotor 201 The difference in magnetic force between the poles becomes large. Therefore, the rotor 201 turns to the direction closer to the position X1 or X2 (the CW direction in FIG. 16 ). Since the current value at the start of this rotation is already large, the magnetic force acting on the magnetic poles of the rotor 201 is also large, and the rotor 201 rapidly rotates and moves. As a result, the rotor 201 may vibrate due to the rapid change in speed, and the machine frame holding the rotor 201 may collide with the airtight casing of the compressor to generate an abnormal sound.

The present invention is proposed to solve the above problems, and its purpose is to provide a starting method and a driving device of a brushless motor that can be reliably started, and to provide a refrigerator in which the starting method is applied to a brushless motor that drives a compressor. electric motor.

Contents of the invention

In order to solve the above problems, the starting method of a brushless motor of the present invention is a starting method of a brushless motor comprising a stator having coils and a rotor having permanent magnets, wherein the steps are as follows:

an initial position moving step of rotating and moving the rotor to a predetermined initial position by performing DC excitation on the coil;

a forced commutation step of rotating the rotor from the initial position by energizing the coils according to a predetermined energization pattern; and

transferring to a transfer step of rotation control based on the rotational position of the rotor estimated using the current or voltage of the coil,

The initial position moving step includes the following steps: a first step of increasing the current of the DC excitation to a first current value, so that the rotor is rotationally moved to a pre-excitation position deviated from the initial position; and

The second step of increasing the current of the DC excitation to a second current value greater than the first current value to rotate the rotor from the pre-excitation position to the initial position, wherein the output makes the When the current of the coil (49) rises to the DC excitation command current of the first current value, the region where the rotor (34) cannot be rotated and moved to the pre-excitation position lies in the output current of the coil (49). When the DC excitation command current reaches the second current value, the rotor (34) cannot be rotationally moved beyond the range of the initial position.

In addition, the refrigerator of the present invention includes: a brushless motor; and a refrigerator with a reciprocating compressor driven by the brushless motor, wherein,

A control unit is provided for performing DC excitation control to increase the current of the coil to a first current value when the brushless motor is started, so that the rotor is rotationally moved to a pre-excitation position deviated from a predetermined initial position. , thereafter, performing DC excitation control to increase the current of the coil to a second current value greater than the first current value, so that the rotor is rotationally moved from the pre-excitation position to the initial position, and thereafter, performing forced commutation control so that the rotor starts to rotate from the initial position,

Wherein, the region where the rotor (34) cannot be rotated and moved to the pre-excitation position in the direct current excitation control of increasing the current of the coil (49) to the first current value is located where the coil (49) The DC excitation control in which the current rises to the second current value cannot cause the rotor (34) to rotate and move beyond the range of the initial position.

According to the present invention, since it is possible to shift to forced commutation while the rotor is reliably rotated and moved to the initial position at the start of the brushless motor, it is possible to prevent vibration and out of step and start reliably.

Description of drawings

FIG. 1 is a flow chart showing a motor starting time according to the first embodiment.

Fig. 2 is a block diagram showing the structure of the driving device.

Fig. 3 is a longitudinal sectional view of the compressor.

Fig. 4 is a diagram schematically showing the positional relationship between the magnetic poles of the rotor and the stator coils.

Fig. 5 is a longitudinal sectional view of the refrigerator.

Fig. 6 is a vector diagram showing the relationship between three-phase currents and two-phase currents.

Fig. 7 is a vector diagram showing the relationship between the αβ-axis current and the dq-axis current.

Fig. 8 is a graph showing the relationship between the rotor stop position and the current value.

FIG. 9 is an explanatory view showing the range of pre-excitation positions of a four-pole motor.

Fig. 10 is an explanatory diagram showing a state in which the rotor is stopped at an intermediate point of the initial position.

Fig. 11 is an explanatory view showing a state in which the rotor is rotationally moved to a pre-excitation position.

Fig. 12 is an explanatory diagram showing a state in which the rotor is rotationally moved to an initial position.

FIG. 13 is a flowchart showing the timing of starting the motor according to Embodiment 2. FIG.

Fig. 14 is an explanatory view showing a state in which the rotor is rotationally moved to an initial position.

Fig. 15 is an explanatory diagram showing a state in which the rotor is stopped at an intermediate point of the initial position.

Fig. 16 is an explanatory diagram showing a state where the rotor is stopped near the initial position.

Detailed ways

Embodiment 1

Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 12 .

Fig. 5 is a longitudinal sectional view of the refrigerator. The refrigerator main body 1 is configured such that a refrigerator compartment 3 , a vegetable compartment 4 , a switch compartment 5 , and a freezer compartment 6 are provided in this order from the upper stage in the heat insulating box 2 . On the front opening portion of the refrigerator body 1, the doors 7-10 of the storage compartments 3-6 are arranged successively from the upper floor. In addition, although it is not shown in a drawing, an ice making chamber is also installed in the switch chamber 5 together.

On the back side of the refrigerating room 3 and the back side of the freezing room 6, a refrigerating room cooler 12 (hereinafter abbreviated as R cooler) and a freezing room cooler 14 (hereinafter referred to as an F cooler) constituting a refrigerating cycle are arranged respectively. The fan 11 for refrigerator compartments and the fan 13 for freezer compartments are installed in the upper part respectively. When the fans 11 and 13 are in operation, the cold air generated by the R cooler 12 and the F cooler 14 is supplied to each room, and controlled according to the set temperature of each room.

At the back bottom of the refrigerator body 1, a machine room 15 is provided. A reciprocating compressor 16, a driving device 18 for controlling and driving a brushless motor 17 for the compressor (hereinafter simply referred to as a motor), and the like are provided inside.

FIG. 3 is a longitudinal sectional view of the reciprocating compressor 16 . Hereinafter, the configuration of the compressor 16 will be described.

The frame 20 is elastically supported by springs 21 at substantially the middle of the airtight casing 19 of the compressor 16 in the vertical direction. In addition, a main shaft supporting hole 23 is provided at the center of the machine frame 20, and the main shaft, that is, a rotating shaft 24 is fitted therein so as to be freely rotatable.

A flange portion 25 is integrally formed on an upper end portion of the rotating shaft 24 . A crank pin 26 is fixed to an upper portion of the flange portion 25 in a state of being eccentric with respect to the central axis of the rotary shaft 24 . When the rotating shaft 24 rotates, the flange portion 25 rotates while sliding on the upper surface of the machine frame 20 , and the crank pin 26 rotates eccentrically with respect to the rotating shaft 24 .

The cylinder 27 is provided in the compressor mechanism part 22 , and the reciprocating piston 29 is installed in the cylinder chamber 28 . The piston 29 and the above-mentioned crank pin 26 are connected by a connecting rod 30 . That is, the piston 29 is connected to one end of the connecting rod 30 through the ball joint mechanism part 31 , and the other end 30 a of the connecting rod 30 is connected to the crank pin 26 so as to be rotatable. With this configuration, when the crank pin 26 rotates eccentrically, the connecting rod 30 swings around the ball joint mechanism portion 31 as a fulcrum, and the piston 29 reciprocates in the cylinder chamber 28 .

In addition, a valve mechanism 33 is provided at the inner end portion (left end in FIG. 3 ) of the air cylinder 27 . The valve mechanism 33 sucks refrigerant gas through a suction chamber not shown in the figure, and discharges the high-pressure gas compressed in the cylinder chamber 28 into the refrigeration cycle through a discharge chamber not shown in the figure.

The electric motor 17 is composed of a rotor 34 and a stator 35 fitted on a rotating shaft 24 protruding downward from the machine frame 20 . Permanent magnets 32 are embedded in a rotor 34 . A narrow gap is provided between the outer peripheral surface of the rotor 34 and the inner peripheral surface of the stator 35 . FIG. 4 is a diagram schematically showing the positional relationship between the magnetic poles of the rotor 34 and the coils 49 of the stator 35 of the motor 17 . The motor 17 is a brushless motor, and in this embodiment is a three-phase, six-slot, four-pole internal type motor.

Next, the operation of the compressor 16 will be described.

When the rotation shaft 24 is rotated by energizing the electric motor 17 , the crank pin 26 rotates eccentrically together with the rotation shaft 24 . This eccentric rotation is converted into reciprocating motion of the piston 29 in the cylinder chamber 28 by the connecting rod 30 and the ball joint mechanism part 24 .

In the airtight cabinet 19, the refrigerant gas evaporated in the R cooler 12 or the F cooler is introduced. This refrigerant gas is drawn into the cylinder chamber 28 through the valve mechanism 33 when the piston 29 moves to the bottom dead center (suction step).

On the contrary, when the piston 29 moves to the top dead center (compression step), the refrigerant gas is compressed and introduced into the refrigeration cycle from the discharge pipe through the valve mechanism 33 . In this way, the compression step and the suction step are repeatedly performed by the rotation of the motor 17 to circulate the refrigerant in the refrigerating cycle to cool the storage chambers 3 to 6 .

Next, the configuration of the driving device 18 for the rotation control motor 17 will be described.

FIG. 2 is a block diagram showing the configuration of the driving device 18 . The drive unit 18 is a sensorless drive unit that detects a rotational position based on the current flowing through the motor 17 . The drive device 18 has an inverter circuit 36, a rectification circuit 37, a PWM forming unit 38, an A/D conversion unit 39, a dq conversion unit 40, a speed detection unit 41, a speed command output unit 42, a speed PI control unit 43, a d-axis A current PI control unit 44 , a q-axis current PI control unit 45 , a three-phase conversion unit 46 , and an initial mode output unit 47 .

In the driving device 18, parts other than the inverter circuit 36 and the rectification circuit 37, and a main control unit 48 which will be described later are all constituted by a microcomputer. In addition, the d-axis current PI control unit 44 , the q-axis current PI control unit 45 , the three-phase conversion unit 46 , and the PWM forming unit 38 constitute a current control unit 55 (current control means).

When the inverter circuit 36 rotates the motor 17 , three-phase drive currents flow to the three-phase (u-phase, v-phase, w-phase) stator coils 49 u , 49 v , 49 w of the motor 17 . The inverter circuit 36 has a configuration in which transistors Tr1 to Tr6 (IGBTs in this embodiment) serving as power semiconductor elements are bridge-connected between DC power supply lines 50p and 50n. Between the transistors Tr4, Tr5, Tr6 on the side of the lower arm and the DC power supply line 50n, shunt resistors R1, R2, R3 (current detectors) for current detection are respectively connected.

The rectification circuit 37 rectifies the AC voltage of the AC power supply 51 of commercial power (for example, AC100V), and supplies it to the inverter circuit 36 .

The PWM forming unit 38 performs pulse width modulation based on three-phase voltages Vu, Vv, and Vw described later, and outputs a PWM signal (commutation signal) to each gate of the transistors Tr1 to Tr6 .

The A/D converter 39 inputs the respective voltages of the shunt resistors R1, R2, R3, converts them from analog to digital, and detects phase currents Iu, Iv, Iw from the A/D converted values.

The dq conversion unit 40 converts the phase currents Iu, Iv, and Iw output from the A/D conversion unit 39 into current components corresponding to magnetic flux, that is, current Id on the d-axis (direct axis), and current components corresponding to torque, That is, the current Iq of the q axis (quadrature axis). In this case, the three-phase-to-two-phase conversion shown in equation (1) is first performed to convert the three-phase currents Iu, Iv, and Iw into two-phase currents Id, Iq. Fig. 6 is a vector diagram showing the relationship between three-phase currents and two-phase currents.

Formula 1)

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; I\&alpha;</span>}\\ \mathrm{<span\; class="notranslate">\; I\&beta;</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}}\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}& <span\; class="notranslate">\; -</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; Iu</span>}\\ \mathrm{<span\; class="notranslate">\; IV</span>}\\ \mathrm{<span\; class="notranslate">\; Iw</span>}\end{array}\right]<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

The dq coordinate conversion shown in the formula (2) is continued, and the two-phase currents Iα, Iβ are converted into d-axis current Id and q-axis current Iq. Fig. 7 is a vector diagram showing the relationship between the two-phase currents Iα, Iβ, the d-axis current Id, and the q-axis current Iq. In addition, the calculations shown in formula (1) and formula (2) may be collectively performed at one time.

Formula (2)

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; ID</span>}\\ \mathrm{<span\; class="notranslate">\; Iq</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{cc}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}& \mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}& \mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; I\&alpha;</span>}\\ \mathrm{<span\; class="notranslate">\; I\&beta;</span>}\end{array}\right]<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

The speed detector 41 detects the rotation angle θ of the rotor 34 of the motor 17 based on the detected d-axis current Id and q-axis current Iq. Then, the rotation speed ω is obtained by differentiating the rotation angle θ.

The main control part 48 performs the control of the whole refrigerator, such as temperature control of each store room 3-6. The main control unit 48 outputs a speed command signal S based on the q-axis current Iq sent from the dq conversion unit 40 .

The speed command output unit 42 generates an output reference rotational speed ωref based on the speed command signal S output from the main control unit 48 and the rotational speed ω output from the speed detection unit 41 . The reference speed ωref performs scale conversion and limit processing on the speed command signal S. The subtracter 52 subtracts the current rotation speed ω from the reference rotation speed ωref, and outputs the difference (rotational speed deviation).

The speed PI control unit 43 inputs the above-mentioned rotational speed deviation, performs PI calculation, and outputs a reference d-axis current Idref and a reference q-axis current Iqref. The subtracter 53 subtracts the detected d-axis current Id from the reference d-axis current Idref to output a d-axis current deviation. The subtracter 53 subtracts the detected q-axis current Iq from the reference q-axis current Iqref to output a q-axis current deviation.

The d-axis current PI control unit 44 inputs a d-axis current deviation, performs PI calculation, and outputs a reference d-axis voltage Vd. Similarly, the q-axis current PI control unit 45 inputs the q-axis current deviation, performs PI calculation, and outputs the reference q-axis voltage Vq.

The three-phase converting unit 46 converts the reference d-axis voltage Vd and the reference q-axis voltage Vq into three-phase voltages Vu, Vv, Vw, and outputs them to the PWM forming unit 38 . In this case, dq coordinate conversion shown in equation (3) is first performed to convert reference d-axis voltage Vd and reference q-axis voltage Vq into two-phase voltages Vα, Vβ.

Formula (3)

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; V\&alpha;</span>}\\ \mathrm{<span\; class="notranslate">\; V\&beta;</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{cc}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}\\ \mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}& \mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; Vd</span>}\\ \mathrm{<span\; class="notranslate">\; wxya</span>}\end{array}\right]<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

The three-phase-to-two-phase conversion shown in formula (4) is continued to convert the two-phase voltages Vα, Vβ into three-phase voltages Vu, Vv, Vw.

Formula (4)

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; Vu</span>}\\ \mathrm{<span\; class="notranslate">\; Vv</span>}\\ \mathrm{<span\; class="notranslate">\; Vw</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}}\left[\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}& \sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}& <span\; class="notranslate">\; -</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; V\&alpha;</span>}\\ \mathrm{<span\; class="notranslate">\; V\&beta;</span>}\end{array}\right]<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

The starting mode for starting the compressor 16 (electric motor 17) is set on the initial mode output unit 47 (current command means). When the motor 17 is started, the driving device 18 starts to run according to the preset starting mode. The so-called starting mode here refers to the used starting d-axis current Idinit2 and the starting q-axis current Idinit2 (forced current Iqinit2) used in the initial position moving step that will be described later. commutation command current), duration, rate of change and other data related to start-up.

Hereinafter, the activation of the motor 17 controlled by the driving device 18 when the compressor 16 in a stopped state starts to operate will be described with reference to FIGS. 1 and 8 to 12 . 10 to 12 schematically show the relationship between the position of the piston 29 in the cylinder chamber 28 of the compressor 16 and the position of the rotor 34 of the electric motor 17 .

In order to start the motor 17 in the stopped state and transfer it to the normal speed control state, the initial position moving step, the forced commutation step, and the speed control transfer step are sequentially executed according to the starting mode set by the initial mode output unit 47 .

The initial position moving step is a step of rotationally moving the rotor 34 stopped at an arbitrary position to the initial position X (see FIGS. 10 to 12 ). The forced commutation step is a step in which the motor 17 is rotated by forced commutation without using the rotation position information, and the motor 17 is accelerated to a rotational speed capable of position detection. The speed control transfer step is a step of switching from the forced commutation control to the commutation control according to the position signal.

The initial position moving step will be described later. First, the forced commutation procedure will be described.

FIG. 1 is a start-up time chart of the motor 17 . The driving device 18 accelerates the motor 17 at a predetermined acceleration, for example, 150 Hz/s ² after the end time tc of the initial position moving step. Specifically, current control is performed so that a constant starting d-axis current Idinit2 flows through the coil 49 , and a PWM signal for forced commutation is output to the inverter circuit 36 as if the rotor 34 is normally rotating. The reason for the forced commutation is that the position detection cannot be performed in the low speed area when starting. At this time, the q-axis current Iq is controlled without speed control, and the starting q-axis current Iqinit2 is zero.

The drive device 18 continues to perform forced commutation until the rotor 34 reaches a switching speed predetermined according to the above-mentioned starting mode, for example 10 Hz/s (=600 rpm) at time td. Then, the forced commutation step is switched to the speed control transfer step at time td.

The driving device 18 detects the rotational speed ω and the rotational position θ of the rotor 34 based on the detected d-axis current Id and q-axis current Iq after the time td when it shifts to the speed control transfer step, and outputs the output to the inverter circuit 36 according to the rotational speed ω. and the PWM signal generated by the reference speed ωref. The inverter circuit 36 switches the transistors Tr1 to Tr6 according to the PWM signal, and outputs three-phase voltages to the coil 49 of the motor 17 . In this way, speed control (feedback control) is performed so that the motor 17 rotates at the rotation speed ω that matches the reference rotation speed ωref.

Hereinafter, the initial position moving procedure will be described.

The initial position moving step has a first step and a second step. When the main control unit 48 outputs a drive command for the compressor 16 to the initial mode output unit 47 at time ta, the initial mode output unit 47 outputs the rotation initial position currents Idinit1 and Iqinit2 to the speed PI control unit 43 every predetermined time, for example, 3 seconds. (step 1). This current is a DC excitation current for rotationally moving the rotor 34 to the pre-excitation position Y (Y1 or Y2 shown in FIG. 11 ). The rotation initial position current Idinit1 is a current that gradually increases from zero to a first current value I1 , for example, 1A. The rotation initial position current Iqinit1 is set to zero.

When the rotation initial position current Idinit1 reaches the first current value I1 at time tb, the initial mode output unit 47 temporarily makes the DC field current zero. Thereafter, the rotation initial position currents Idinit1 and Iqinit1 are output again to the speed PI control unit 43 every predetermined time, for example, 3 seconds (second step). This current is a DC excitation current for rotating and moving the rotor 34 to the initial position X. As shown in FIG. The rotation initial position current Idinit1 is a current that gradually increases from zero to a second current value I2 , for example, 2A. The rotation initial position current Iqinit1 is set to zero. The second current value I2 is set to be larger than the above-mentioned first current value I1. On the other hand, when the rotation initial position current Idinit1 reaches the second current value I2 at time tc, the process goes to the above-mentioned forced commutation step.

Here, the reason for providing the first step will be described.

The inventors of the present application appropriately changed the stop position of the rotor 34 from the initial position, and measured the current value required to rotationally move the rotor 34 from each stop position to the initial position by DC excitation. In addition, when rotating from each stop position to the initial position X, the current value at which the frame 20 collides with the airtight casing 19 and produces an abnormal sound due to the sudden change of the rotor 34 is also measured. Here, the stop position of the rotor 34 is, for example, the S pole position of the permanent magnet 32 , and the initial position X ( X1 , X2 ) is, for example, the N pole position of the magnetic field generated by DC excitation.

Fig. 8 shows the results of this experiment. The solid line shows the relationship between the stop position and the current value required for rotational movement, and the dotted line shows the relationship between the stop position and the current value for generating abnormal sound. The horizontal axis is the angle (mechanical angle) from the initial position X, and the vertical axis is the current value. It can be seen from FIG. 8 that the closer the stop position of the rotor 34 is to the initial position X, the more the rotor 34 can be rotated and moved with a smaller current. In addition, the closer the stop position of the rotor 34 is to the initial position X, the larger the current value at which the abnormal sound is generated.

However, when the stop position of the rotor 34 is near the middle point Z of the initial positions X1 and X2 as shown in FIG. To move the rotor 34 rotationally out of this equilibrium requires a larger field current. In addition, since the rotation distance to the initial position X is long, the acceleration of the rotor 34 by DC excitation tends to cause a sudden change in the rotational speed, and the current value at which the abnormal sound is generated decreases. Therefore, the current value at which the abnormal sound is generated near the middle point Z is lower than the current value required for rotation.

In view of the characteristics shown in FIG. 8 , when it is desired to prevent out of step or abnormal noise, the rotor 34 cannot be rotated and moved though DC excitation is performed with a current value of 1.7 A or less. In addition, if a current value of 1.7 A or more is passed, although the rotor 34 can be rotated and moved, abnormal noises or out-of-synchronization will be generated as described above.

9 shows the relationship between the initial position X (X1, X2), the pre-excitation position Y (Y1, Y2), and the initial position non-rotatable area Z1-Z2 (described later) for the four-pole motor 17 . The angles shown in the figure are mechanical angles. When the stop position of the rotor 34 is within a range of 5 degrees around 90 degrees (intermediate point Z) (a range of 85 degrees to 95 degrees in the CW direction or CCW direction based on X1), the above problem does not occur. Taking into account factors such as errors, the range where abnormal sounds or out-of-synchronization will occur (hereinafter referred to as the initial position non-rotatable area Z1-Z2) is set at a range of 10 degrees before and after the center of 90 degrees (the middle point Z) ( From 80 degrees to 100 degrees based on X1), this setting is appropriate.

Therefore, in order to prevent out-of-step or abnormal sound, the rotor 34 is reliably rotated and moved to the initial position X by DC excitation, and as a preparatory step, the first step of rotating the rotor 34 to the pre-excitation position Y (Y1 or Y2) is provided. . By doing this, it is possible to prevent the rotor 34 from continuing to stop in the initial position non-rotatable area Z1-Z2 at the time of start-up.

The setting range of the pre-excitation position Y needs to be set such that the rotor 34 can rotate and move away from the initial position non-rotatable area Z1-Z2 before the DC excitation current reaches the first current value I1 smaller than the second current value I2. When the range of 0° to 20° too close to the initial position X is used as the pre-excitation position Y, the rotor 34 stopped in the initial position non-rotatable area Z1-Z2 may not be able to rotate and move in the first step. On the other hand, when the range of 80° to 100° of the intermediate point Z too close to the initial position X is used as the pre-excitation position Y, the rotor 34 is stopped in the initial position non-rotatable area Z1-Z2 in the first step. Therefore, the pre-excitation position Y in the CW direction or the CCW direction is set within a range of 20 degrees to 80 degrees based on the initial position X (X1, X2). Also, considering factors such as errors, it is best to set it within the range of 30 degrees to 70 degrees.

Specifically, as shown in FIG. 9 , the pre-excitation position Y ( Y1 , Y2 ) is set at a position away from the initial position X, for example, 45 degrees, and DC excitation is performed to move the rotor 34 to the pre-excitation position Y. In this way, it is assumed that even if the rotor 34 stops in the initial position non-rotatable area Z1-Z2, it can still rotate and move to the pre-excitation position Y from the initial position non-rotatable area by the first step. And continuing to use the second step can reliably rotate and move from the pre-excitation position Y to the initial position X.

In addition, when the rotor 34 stops at the intermediate point O of the pre-excitation positions Y1, Y2 or its vicinity O1-O2, under the DC excitation in the first step, when it rises to the second current value I2 as in the second step, even if Even the first step will produce abnormal sound or lose synchronization. On the other hand, in the first step, only the first current value I1 smaller than the second current value I2 used in the second step is increased. By doing so, the rotor 34 can be prevented from rapidly rotating and moving, and the above-mentioned problem can be solved.

In the first step, since the direct-current excitation current is raised only to the first current value I1, the regions O1 to O2 in which rotational movement is impossible are enlarged. However, even if the rotor 34 is stopped in this area, since this area is outside the initial position non-rotatable area Z1-Z2, the rotor 34 can be reliably rotated and moved to the initial position X in the second step.

As described above, in this embodiment, the initial position movement step at the time of startup is constituted by the first step and the second step. In the first step, DC excitation is performed up to the first current value I1, and the rotor 34 is rotated to the pre-excitation position Y, and thereafter, in the second step, DC excitation is performed up to the first current value I2 greater than the first current value I1, so that The rotor 34 is turned to the initial position X. In this way, the rotor 34 can be reliably rotated and moved to the initial position X in the second step, and the continuous execution of the forced commutation step after the initial position moving step can prevent out-of-step reliable start.

In addition, by applying the above-described starting method to the electric motor 17 for starting the compressor 16 of the refrigerator, the speed of the rotor 34 can be prevented from changing rapidly. As a result, the compressor 16 can be reliably started without abnormal sound.

Embodiment 2

Hereinafter, Embodiment 2 of the present invention will be described with reference to FIG. 13 .

In Embodiment 1, since the current is raised only to the first current value I1 smaller than the second current value I2 in the first step, when the rotor 34 stops at the middle point Z of the initial position X and its vicinity Z1 to Z2 Sometimes it is difficult to rotate and move. In this embodiment, in order to reliably move the rotor 34 in the first step, it is designed to continue energizing at the first current value I2 only for a predetermined time after the DC exciting current rises to the first current value I1.

Specifically, as shown in FIG. 13 , the drive device gradually increases the current value from time te to rotate the rotor 34 to the pre-excitation position (current increase step). Then, when the DC excitation current reaches the first current value I1 at time tf, the first current value I1 is kept unchanged for a predetermined time, here two seconds, and DC excitation is continued (current holding step). Then, the th current value returns to zero at a time after a predetermined time elapses, and then the process proceeds to the second step.

With this configuration, even if the rotor 34 stops at a place where it is difficult to rotate, that is, the non-rotatable area Z1-Z2 in the initial position, it can reliably rotate and move to the pre-excitation position in the first step, and in the second step thereafter, it will be forced to commutate The steps enable the motor 17 to be started reliably.

Also, as shown by the dotted line in FIG. 13 , from time tg between time tf and time th, DC excitation may be performed with a third current value I3 smaller than the first current value I1 thereafter. By doing so, it is possible to prevent the rotation of the th rotor 34 just before the transition to the second step.

other implementations

In addition, this invention is not limited to each embodiment mentioned above and shown in drawing, For example, the following deformation|transformation or expansion are possible.

In each embodiment, a 4-pole motor 17 will be described as an example. However, the situation that the rotor 34 cannot rotate due to the magnetic force balance is a problem that also occurs in motors with other numbers of poles such as a 2-pole motor and a 6-pole motor. The present invention is similarly applicable to these motors. However, since the angles above or shown in the figures are mechanical angles, the values will be different for motors with other numbers of poles. For example, in the case of a 2-pole motor, the pre-excitation position Y is set in the angle range of 40 degrees to 160 degrees (mechanical angle and electrical angle) along the CW direction or CCW direction based on the initial position X. Considering factors such as errors, It is best to set it within the range of 60 degrees to 140 degrees.

The rate of increase of the DC exciting current in the initial position moving step does not have to be constant. The rotational position of the rotor 34 can be estimated using the voltage of the coil 49 .

In each embodiment, although the brushless motor for refrigerators was demonstrated, this invention is not limited to this, It is suitable also as the starting method of the brushless motor used for various equipment. In addition, although vector control is used as an example to describe, the same effect can be obtained by normal inverter control. In addition, the magnetic poles of the rotor, the current value, and the DC excitation position can be appropriately changed without changing the spirit of the present invention.

Industrial Applicability

As described above, the method for starting a brushless motor according to the present invention can be used not only for starting a brushless motor for a refrigerator but also for starting a brushless motor for various other devices.

Claims (5)

1. the startup method of a brushless motor, this brushless motor (17) comprising: the rotor (34) that has the stator (35) of coil (49) and have permanent magnet (32) is characterized in that having following steps:

By described coil (49) is carried out DC excitation, the initial position that makes described rotor (34) rotation move to predetermined initial position moves step;

By described coil (49) is switched on the forced commutation step that makes described rotor (34) begin to rotate from described initial position according to predetermined powered-on mode; And

The position of rotation of the described rotor (34) of inferring according to the curtage that utilizes described coil (49) is transferred to the transfer step of Spin Control,

Described initial position moves step and may further comprise the steps:

Make the electric current of described DC excitation rise to the 1st current value, so that described rotor (34) rotation moves to the 1st step of the preparation on-position that departs from described initial position; And

Make the electric current of described DC excitation rise to 2nd current value bigger than the 1st current value, so that described rotor (34) rotates the 2nd step that moves to described initial position from described preparation on-position,

Wherein, can't rotate the zone that moves to described preparation on-position at rotor (34) described in described the 1st step is located at described the 2nd step rotor (34) and can't rotates beyond the zone that moves to described initial position.

2. the startup method of brushless motor as claimed in claim 1 is characterized in that,

When described brushless motor (17) was 4 utmost points, it was that 20 of benchmark is spent in the angular range of～80 degree that described preparation on-position is set in described initial position, and wherein said angle is a mechanical angle.

3. the startup method of brushless motor as claimed in claim 1 is characterized in that,

Described the 1st step has following steps:

Make the electric current of described DC excitation rise to the electric current up step of described the 1st current value; And

In the stipulated time after this, the electric current that described coil (49) upper reaches is crossed less than the electric current of the DC excitation that equals described the 1st current value keeps step.

4. the drive unit of a brushless motor, this brushless motor (17) comprising: the rotor (34) that has the stator (35) of coil (49) and have permanent magnet (32) is characterized in that having

According to change of current signal, the inverter circuit (36) that described coil (49) is switched on;

Detect the current detector (R1, R2, R3) of the electric current that flows through on the described coil (49);

Generate change of current signal according to instruction current and described detection electric current, export the current control unit (55) of this change of current signal to described inverter circuit; And

Current-order unit (47), this current-order unit (47) is used for when starting, to described current control unit (55), output makes the electric current of described coil (49) rise to the DC excitation instruction current of the 1st current value, so that described rotor (34) rotation moves to the preparation on-position that departs from predetermined initial position, after this, output makes the electric current of described coil (49) rise to the DC excitation instruction current of 2nd current value bigger than described the 1st current value, so that described rotor (34) moves to described initial position from described preparation on-position rotation, after this, output forced commutation instruction current, so that described rotor (34) begins rotation from described initial position

Wherein, the zone that can't make described rotor (34) rotation move to described preparation on-position when output makes the electric current of described coil (49) rise to the DC excitation instruction current of the 1st current value is located at when electric current that output makes described coil (49) rises to the DC excitation instruction current of the 2nd current value described rotor (34) rotation is moved to outside the zone of described initial position.

5. refrigerator, the reciprocating compressor (16) that has brushless motor (17) and drive by brushless motor (17), described brushless motor (17) comprising: have the stator (35) of coil (49), and the rotor (34) with permanent magnet (32), it is characterized in that

Has control unit (18), when this control unit (18) starts at described brushless motor (17), make the electric current of described coil (19) rise to the DC excitation control of the 1st current value, so that described rotor (34) rotation moves to the preparation on-position that departs from predetermined initial position, after this, make the electric current of described coil (49) rise to the DC excitation control of 2nd current value bigger than the 1st current value, so that described rotor (34) moves to described initial position from described preparation on-position rotation, after this, carry out forced commutation control, so that described rotor (34) begins rotation from described initial position

Wherein, rising to the zone that can't make described rotor (34) rotation move to described preparation on-position in the DC excitation control of the 1st current value at the electric current that makes described coil (49) is located in the DC excitation control that the electric current that makes described coil (49) rises to the 2nd current value described rotor (34) rotation is moved to outside the zone of described initial position.

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