WO2015154696A1

WO2015154696A1 - Direct current brushless motor system for drain pump, and control method and control device thereof

Info

Publication number: WO2015154696A1
Application number: PCT/CN2015/076206
Authority: WO
Inventors: 王胜; 朋兴谱
Original assignee: 常州雷利电机科技有限公司
Priority date: 2014-04-11
Filing date: 2015-04-09
Publication date: 2015-10-15
Also published as: CN104980066B; CN104980066A

Abstract

A control method and control device of a direct current brushless motor for a drain pump, and direct current brushless motor system for the drain pump, the control method comprising: when the rotation speed of a direct current brushless motor reaches a first predetermined rotation speed, comparing the duty ratio of a voltage pulse supplying power for the stator winding of the direct current brushless motor with a first critical duty ratio; and when the duty ratio of the voltage pulse is lower than the first critical duty ratio, determining that the drain pump is in a half-water half-air operation state, and setting the target rotation speed of the direct current brushless motor as a second predetermined rotation speed, the second predetermined rotation speed being lower than the first predetermined rotation speed. The half-water half-air state of the drain pump is identified according to the duty ratio of the voltage pulse supplying power for the stator winding, and half-water half-air noise is reduced by reducing the target rotation speed of the direct current brushless motor in the half-water half-air state.

Description

DC brushless motor system for drain pump, control method and control device thereof

Technical field

The present invention relates to the field of drainage pump technology, and more particularly to a control method and control device for a DC brushless motor for a drainage pump of a household appliance, and a DC brushless motor system for a drainage pump of a household appliance.

Background technique

At present, single-phase AC permanent magnet synchronous motors are widely used in household appliances such as dishwashers and washing machines for their high energy efficiency and excellent steady-state characteristics. However, single-phase AC permanent magnet synchronous motors have certain limitations in terms of startup and operation performance.

For example, in the application of the washing machine drain pump, in order to solve the problem that the load of the drain pump is large and the motor is easily burned, it is necessary to add a starting device, which is mainly composed of a coupling provided with a starting rib and a starting cavity provided with a starting boss. In the instant of starting the motor, it is necessary to first idling a certain angle. When the starting rib turns to contact with the starting boss, the impeller can be driven to rotate, thereby achieving the effect of no-load starting, effectively solving the problem of burning the motor due to the large starting load. . In order to reduce the noise, a shock pad may be provided on both sides of the starting rib or on both sides of the starting boss in order to reduce the noise when the starting rib is in contact with the starting boss. The structure of the motor is relatively complicated, the assembly process is cumbersome, and the increase of the starting cavity and the cushion also greatly increases the cost, and the failure of the cushion is present after multiple starts.

Secondly, the single-phase AC permanent magnet synchronous motor itself cannot achieve directional rotation and speed regulation. It is necessary to add a non-return mechanism to the rotor structure to prevent the motor from rotating in reverse, and realize the single-phase AC permanent magnet synchronous motor by adjusting the frequency of the power supply voltage. The speed regulation is that the vibration, the noise is high and the temperature rise is high during the no-load operation, and in the later stage of the drainage process, a small amount of residual water is mixed with the air, so that the drainage pump is in a semi-aqueous and semi-air state, and the motor cannot recognize this. In the state, the impeller still rotates at high speed, producing half-water and half-air noise.

A technique for identifying such a semi-aqueous half-air state of a single-phase AC permanent magnet synchronous motor has been proposed. A method for controlling a household appliance discharge pump and a processing unit implementing the same are disclosed in the patent document of Chinese Patent Application Publication No. CN102444570A, which calculates a zero current platform of a motor phase current function and a counter electromotive force associated with the same phase. The phase difference between the zero crossings of the signal identifies the semi-aqueous, semi-air state of the single-phase AC permanent magnet synchronous motor. However, it only identifies the critical state of the single-phase AC permanent magnet synchronous motor entering the semi-water and semi-air operation, and cuts off the power supply to the motor. After the water level returns to a certain value, start the motor again. The disadvantage of this control method is that the residual water cannot be completely discharged through the motor, so the problem of half-water and half-air noise during the drainage process is not completely solved.

With the introduction of the concept of green household appliances and the enhancement of environmental awareness, the existing drainage pumps have been unable to meet the increasing requirements for the comfort of the living environment. Therefore, there is a need for a new type of drainage pump which is simple in structure, small in volume, high in efficiency, and low in operating noise.

Summary of the invention

In order to solve the above technical problem, according to an aspect of the present invention, a control method and a control device for a DC brushless motor for a drain pump, and a DC brushless motor system for a drain pump are provided, which can identify a half of a drain pump The water is in a semi-air state, and the half-water half-air noise is reduced by lowering the target rotational speed of the brushless DC motor in this state.

According to another aspect of the present invention, a control method of a DC brushless motor for a drain pump is provided, comprising: after the rotational speed of the DC brushless motor reaches a first predetermined rotational speed, the DC brushless motor is to be Comparing a duty cycle of a voltage pulse supplied by the stator winding with a first critical duty ratio; and determining that the drain pump enters if a duty cycle of the voltage pulse is lower than the first critical duty ratio a semi-aqueous half-air operating state, and setting a target rotational speed of the brushless DC motor to a second predetermined rotational speed, wherein the second predetermined rotational speed is lower than the first predetermined rotational speed.

According to an embodiment of the present invention, when the DC brushless motor is in an idle operation state, a duty ratio of a voltage pulse for supplying power to a stator winding of the brushless DC motor is a first duty ratio; When the brushless motor is in the rated load operating state, the duty ratio of the voltage pulse for supplying power to the stator winding of the brushless DC motor is the second duty ratio; wherein the first critical duty ratio is greater than the first a duty cycle and less than the second duty cycle.

According to an embodiment of the present invention, when the duty ratio of the voltage pulse continues to decrease and is lower than the first critical duty ratio, it is determined that the drain pump enters a semi-aqueous half-air operating state, and the The target rotational speed of the brushless DC motor is set to a second predetermined rotational speed.

According to an embodiment of the present invention, after the speed of the DC brushless motor in the rated load operating state reaches the first predetermined speed, when the duty ratio of the voltage pulse is lower than the first critical duty ratio And determining that the drain pump enters a semi-aqueous half-air operating state, and setting a target rotational speed of the DC brushless motor to the second predetermined rotational speed.

Voltage pulse supplied by the stator winding of the brushless DC motor according to an embodiment of the invention The target rotational speed of the drain pump DC brushless motor is set to the third predetermined rotational speed when the duty ratio continues to decrease to the second critical duty ratio, wherein the second critical duty ratio is greater than The first duty cycle is less than the first threshold duty, and the third predetermined speed is higher than the second predetermined speed.

According to an embodiment of the present invention, the first predetermined rotational speed is equal to or lower than a rated rotational speed of the DC brushless motor, and the third predetermined rotational speed is equal to a rated rotational speed of the DC brushless motor; the first critical duty The ratio is equal to the second critical duty cycle.

According to still another aspect of the present invention, there is provided a control device for a DC brushless motor for a drain pump, comprising: a duty ratio comparing member that will give a speed after the speed of the DC brushless motor reaches a first predetermined speed Comparing a duty ratio of a voltage pulse supplied from a stator winding of the brushless DC motor with a first critical duty ratio, and obtaining a first comparison result; and a target rotation speed setting unit indicating the first comparison result In a case where the duty ratio of the voltage pulse is lower than the first critical duty ratio, it is determined that the drain pump enters a half-water half-air operating state, and the target rotating speed of the DC brushless motor is set to a second predetermined The rotational speed, wherein the second predetermined rotational speed is lower than the first predetermined rotational speed.

According to an embodiment of the present invention, after the rotational speed of the DC brushless motor in the rated load operating state reaches the first predetermined rotational speed, the target rotational speed setting unit indicates that the duty ratio of the voltage pulse is lower than the first comparison result. In the case of the first critical duty ratio, it is judged that the drain pump enters a half-water half-air operating state, and the target rotational speed of the direct current brushless motor is set to the second predetermined rotational speed.

According to an embodiment of the present invention, the duty ratio comparing unit compares a duty ratio of a voltage pulse for supplying power to a stator winding of the brushless DC motor with a second threshold duty ratio, and obtains a second comparison result; The target rotational speed setting unit further sets a target rotational speed of the DC brushless motor to the first in a case where the second comparison result indicates that a duty ratio of the voltage pulse is lower than a second critical duty ratio a predetermined rotational speed, wherein the second critical duty ratio is greater than the first duty cycle and less than the first critical duty cycle, the third predetermined rotational speed being higher than the second predetermined rotational speed speed.

According to still another aspect of the present invention, a DC brushless motor system for a drain pump is provided, comprising: a DC brushless motor comprising: a stator assembly and a rotor assembly, the stator assembly including a stator core and being wound in a stator core slot a stator winding, the rotor assembly includes a rotor pole; and a motor control system comprising: a drive module, a position detection module, and a control module, wherein the position detection module detects a position of a rotor pole in the DC brushless motor, The control module calculates an actual rotational speed of the rotor magnetic pole according to the position of the rotor magnetic pole detected by the position detecting module, and outputs the control according to the target rotational speed of the DC brushless motor and the actual rotational speed of the DC brushless motor. a control pulse signal of the driving module; wherein the control module further determines that the drain pump enters a semi-aqueous half-air state when a duty ratio of a voltage pulse output by the driving module is lower than a first critical duty ratio And reducing the target rotational speed of the brushless DC motor.

According to an embodiment of the invention, the number of stator core slots is the same as the number of rotor poles, and the radial air gap formed by the rotor poles and the stator core is a non-uniform air gap.

According to an embodiment of the invention, the driving module comprises an H-bridge inverter; and the control pulse signal output by the control module is a switch control pulse signal for controlling four switches in the H-bridge inverter.

According to an embodiment of the present invention, after the rotation speed of the DC brushless motor reaches a first predetermined rotation speed, the control module determines when the duty ratio of the voltage pulse outputted by the driving module is lower than the first critical duty ratio. The drain pump enters a semi-aqueous half-air state, and sets a target rotational speed of the direct current brushless motor to a second predetermined rotational speed, wherein the second predetermined rotational speed is lower than the first predetermined rotational speed.

According to an embodiment of the present invention, when the DC brushless motor is in an idle operation state, a duty ratio of a voltage pulse outputted by the driving module is a first duty ratio; and the DC brushless motor is at a rated load When in an operating state, a duty ratio of a voltage pulse output by the driving module is a second duty ratio; wherein the first critical duty ratio is greater than the first duty ratio, and is smaller than the second duty ratio Empty ratio.

According to an embodiment of the invention, after the speed of the brushless DC motor in the rated load operating state reaches a first predetermined speed, the duty ratio of the voltage pulse is lower than the first threshold In the case of the air ratio, the control module determines that the drain pump enters the semi-aqueous half air operating state, and sets the target rotational speed of the DC brushless motor to the second predetermined rotational speed.

According to an embodiment of the present invention, in a case where the duty ratio of the voltage pulse supplied from the stator winding of the brushless DC motor continues to decrease to the second critical duty ratio, the target rotational speed setting of the drain brush DC brushless motor is set. Is the third predetermined rotational speed, wherein the second critical duty ratio is greater than the first duty cycle and less than the second duty cycle, the third predetermined rotational speed being higher than the second predetermined Rotating speed.

According to an embodiment of the invention, the first predetermined rotational speed and the third predetermined rotational speed are equal to a rated rotational speed of the DC brushless motor; the first critical duty ratio is equal to the second critical duty ratio.

A control method and a control device for a DC brushless motor for a drain pump according to an embodiment of the present invention, and a DC brushless motor system for a drain pump, after the rotational speed of the DC brushless motor reaches a preset rotational speed, The duty ratio of the voltage pulse supplied by the stator winding of the DC brushless motor is compared with a preset critical duty ratio corresponding to the semi-aqueous half air state critical judgment point of the drain pump, and it is determined whether the drain pump enters a half a water semi-air state, and further reducing a target rotational speed of the DC brushless motor in a state where the drain pump is judged to enter a semi-aqueous half-air state, thereby reducing a half-water half-air noise generated by the drain pump, and simultaneously It also enables the drain pump to completely drain the remaining water.

Other features and advantages of the invention will be set forth in the description which follows, The objectives and other advantages of the invention may be realized and obtained by means of the structure particularly pointed in the appended claims.

DRAWINGS

The drawings are intended to provide a further understanding of the invention, and are intended to be a In the drawing:

1 is a schematic view showing the overall structure of a DC brushless motor system for a drain pump according to an embodiment of the present invention;

2 illustrates a schematic block diagram of a motor control system in a drain pump in accordance with an embodiment of the present invention;

3 is a block diagram showing a specific structure of a motor control system according to an embodiment of the present invention;

4 illustrates a control schematic diagram implemented by control module 22 in accordance with an embodiment of the present invention;

FIG. 5 illustrates an operation stage of a DC brushless motor for a drain pump according to an embodiment of the present invention. intention;

FIG. 6 illustrates a schematic flow chart of a method 600 of controlling a brushless DC motor in accordance with an embodiment of the present invention;

FIG. 7 illustrates a schematic block diagram of a control device 700 of a DC brushless motor for a drain pump according to an embodiment of the present invention.

detailed description

Various embodiments in accordance with the present invention will be described in detail with reference to the accompanying drawings. Here, it is to be noted that in the drawings, the same reference numerals are given to the components having substantially the same or similar structures and functions, and repeated description thereof will be omitted.

DC brushless motors have been widely used in various fields due to their small size, good dynamic response characteristics, large starting torque and strong overload capability. The brushless DC motor has the advantage that the single-phase AC permanent magnet synchronous motor can not be compared in terms of starting. It can provide a large starting torque in addition to the starting device. Therefore, in the present invention, a DC brushless motor is applied to the field of household appliance drainage pumps such as dishwashers and washing machines.

1 is a schematic view showing the overall structure of a DC brushless motor system for a drain pump according to an embodiment of the present invention. The DC brushless motor system for a drain pump shown in FIG. 1 includes a DC brushless motor 1 and a motor control system 2.

The brushless DC motor 1 includes a stator assembly including a stator core and stator windings wound in a stator core slot, and a rotor assembly including a rotor pole.

Specifically, the stator winding is a single-phase bipolar winding wound in a stator core slot according to a certain regularity. In the brushless DC motor 1, the radial air gap formed by the rotor pole and the stator core is a non-uniform air gap, a position where the air gap is large, a large magnetic resistance, a small air gap, and a small magnetic resistance.

With the rotation of the rotor pole, when the air gap between the rotor pole and the stator core gradually changes from large to small, that is, when the magnetic resistance of the rotor pole rotates from large to small, the running performance of the brushless DC motor 1 can be Get optimized.

The structure of the motor of the brushless DC motor is well known to those skilled in the art, and therefore, in order to avoid obscuring the present invention, the motor structure of the brushless DC motor will not be described herein.

FIG. 2 shows a detailed schematic of a motor control system 2 in accordance with an embodiment of the present invention.

As shown in FIG. 2, the motor control system 2 includes a drive module 21, a control module 22, and a position detection module 23 in accordance with an embodiment of the present invention.

The driving module 21 supplies power to the DC brushless motor, and the driving module 21 has two output terminals A and B. The output polarity is adjustable between the first output end A and the second output end B, and the width can be And a voltage pulse having a constant amplitude, the voltage pulse driving the DC brushless motor to rotate.

FIG. 3 shows a block diagram of a specific structure of a motor control system according to an embodiment of the present invention.

As shown in FIG. 3, the driving module 21 may include an H-bridge inverter circuit, and the driving module 21 receives a four-way switch control signal from the control module 22, and the switch control signal may be a PWM signal, and according to The received four-way switch control signals respectively control the conduction and disconnection of the switches of the four bridge arms of the H-bridge inverter circuit. In order not to obscure the present invention, the generation of the PWM signal is not specifically described herein.

According to an embodiment of the invention, each of the bridge arms of the H-bridge inverter circuit includes a controllable switch, and the controllable switch is, for example, a switching device such as a MOSFET or an IGBT.

As shown in FIG. 3, the H-bridge inverter circuit includes switches Q1, Q2, Q3, and Q4, wherein switches Q1 and Q3 are located in the upper arm, switches Q2 and Q4 are located in the lower arm, and switches Q1 and Q3 are The connection point between the two constitutes the first input terminal M, the connection point between the switch Q2 and the switch Q4 constitutes the second input terminal N, the connection point of the switch Q1 and the switch Q2 constitutes the first output terminal A, and the connection of the switch Q3 and the switch Q4 The dots constitute a second output terminal B.

The polarity and width of the voltage pulse applied between the first output terminal A and the second output terminal B can be controlled by controlling the on and off of the switches Q1, Q2, Q3 and Q4.

For example, assume that the voltage between the first input terminal M and the second input terminal N is positive, and when Q1 and Q4 are on, at the first input terminal A and the second input terminal The polarity of the voltage pulse between B is positive polarity. Conversely, when Q2 and Q3 are turned on, the polarity of the voltage pulse between the first input terminal A and the second input terminal B is negative polarity. .

Further, the drive module 21 may further include a level conversion circuit (not shown) that receives the four-way switch control signal from the control module 22 and receives the received four, as needed. The switch control signals are level-converted to obtain four-way switch drive signals for driving the switches Q1, Q2, Q3 and Q4 in the H-bridge inverter circuit, respectively. For example, the high level of the four-way switch control signal may be 5V, and the high level of the four-way switch drive signal may be 12V.

The position detecting module 23 may include a Hall sensor mounted on the stator core at a position close to the rotor through which the position of the rotor pole is sensed. For example, the rotor pole position signal obtained by the Hall sensor is in the form of high and low levels.

The control module 22 can receive the rotor magnetic pole position signal output by the position detecting module 23, and can calculate the rotor magnetic pole of the DC brushless motor according to the position of the rotor magnetic pole detected by the position detecting module 23. The actual rotational speed, and a control pulse signal for controlling the drive module, that is, the four-way switch control signal, is output according to a target rotational speed of the DC brushless motor and an actual rotational speed of the DC brushless motor.

4 shows a control schematic diagram implemented by control module 22 in accordance with an embodiment of the present invention.

As shown in FIG. 4, the control module 22 can include a speed outer loop control sub-module 221 and a current inner loop control sub-module 222.

The speed outer loop control sub-module 221 implements a closed loop control function of the speed outer loop, which calculates a speed difference between the current speed of the DC brushless motor and the target speed, and obtains a current inner loop based on the speed difference Current setpoint.

According to an embodiment of the present invention, the speed outer loop control sub-module 221 may include a speed PID controller, and the speed PID controller performs a PID (proportional-integral-derivative) operation on the speed difference to obtain the current. Desired point. The control performance of the DC brushless motor control system can be adjusted by adjusting the proportional coefficient, the integral coefficient, and the differential coefficient of the speed PID controller.

The current inner loop control sub-module 222 implements a closed loop control function of the current inner loop, which calculates a current between the current stator current of the brushless DC motor and the current set value provided by the speed outer loop control sub-module 221 And a duty ratio, and based on the current difference, controlling a duty cycle of a voltage pulse that the driving module supplies power to a stator winding of the brushless DC motor.

According to an embodiment of the invention, the current loop control sub-module 222 may include a current PID controller, and the current PID controller performs a PID (proportional-integral-derivative) operation on the speed difference to obtain the current Value. The control performance of the DC brushless motor control system can be adjusted by adjusting the proportional coefficient, the integral coefficient, and the differential coefficient of the current PID controller.

Further, according to an embodiment of the present invention, the motor control system may further include a current detector that detects a stator current of the DC brushless motor, and an AD converter that detects the current The analog signal of the stator current of the DC brushless motor detected by the device is converted into a digital signal.

According to an embodiment of the present invention, when the DC brushless motor is in an idle operation state, the target rotational speed of the DC brushless motor is its rated rotational speed. At this time, the driving module is given to the DC brushless motor. The duty ratio of the voltage pulse supplied by the stator winding is the first duty ratio; and when the DC brushless motor is in the rated load operating state, the target of the DC brushless motor is turned The speed is also its rated speed. At this time, the duty ratio of the voltage pulse supplied by the driving module to the stator winding of the brushless DC motor is the second duty ratio. According to the operating principle of the DC brushless motor, the second duty ratio is greater than the first duty ratio.

After the drain pump discharges part of the water, when the brushless DC motor is in the semi-aqueous half-air state, the load of the brushless DC motor is less than the rated load, if the target speed of the DC brushless motor is still rated The speed, the speed closed-loop control sub-module 221 will control the DC brushless motor to maintain its rotational speed constant, through the control of the speed closed-loop control sub-module 221 and the current closed-loop control sub-module 222, by adjusting the drive module a duty cycle of a voltage pulse for supplying power to a stator winding of the brushless DC motor to maintain a constant rotational speed of a rotor pole of the DC brushless motor, and at this time, a duty ratio of the voltage pulse is a third duty ratio . According to the operating principle of the DC brushless motor, the second duty ratio is greater than the third duty ratio, and the third duty ratio is greater than the first duty ratio.

As described above, if the DC brushless motor for the drain pump enters the semi-aqueous half-air operating state, the DC brushless motor still drives the impeller to rotate at a high speed, resulting in a large half-half air noise.

According to the embodiment of the present invention, the half-water and half-air operating state of the DC brushless motor is identified according to the duty ratio of the voltage pulse supplied by the driving module to the stator winding of the brushless DC motor, and is recognized Reducing the target rotational speed of the DC brushless motor after the semi-aqueous and semi-air operating state, that is, reducing the target rotational speed of the DC brushless motor in the semi-aqueous and semi-air operating state, thereby reducing the half-water and half-air noise. And the DC brushless motor continues to operate at a reduced rotational speed to drive the impeller portion to discharge all of the remaining water.

Fig. 5 is a view showing the working phase of a DC brushless motor for a drain pump according to an embodiment of the present invention.

First, in the startup phase S1, the switches Q1 and Q4 in the H-bridge inverter circuit are turned on, and are output between the first output terminal A and the second output terminal B of the H-bridge inverter circuit. The polarity of the voltage pulse is positive polarity. In other words, the stator winding of the brushless DC motor is pre-energized in the A→B direction, and then the switches Q2 and Q3 in the H-bridge inverter circuit are turned on. And disconnecting the switches Q1 and Q4 in the H-bridge inverter circuit, at this time, outputting a voltage pulse between the first output terminal B and the second output terminal B of the H-bridge inverter circuit The polarity is negative polarity, in other words, the stator winding of the brushless DC motor is pre-energized in the B→A direction. The magnetic field formed by pre-energizing the stator winding of the brushless DC motor can form a magnetic field with the magnetic pole of the rotor Repulsive force or suction, thereby driving the rotor pole to rotate a slight angle, and enabling the position sensing module to determine the position of the rotor pole at this time.

After the position sensing module is capable of determining the position of the rotor pole of the DC brushless motor, the speed outer loop control sub-module 221 and the current inner loop control sub-module 222 in the control module 21 control the control The DC brushless motor is accelerated until the target speed (eg, rated speed) is reached.

Then, the DC brushless motor enters the stable operation phase S2 under the control of the control module 21.

After the drain pump begins to drain, there is a case where water and air are mixed, the load of the brushless DC motor is reduced, and correspondingly through the speed outer loop control sub-module 221 and the control unit 22 in the control module 22 The control of the current inner loop control sub-module 222 adjusts the duty cycle of the voltage pulse supplied by the drive module to the stator winding of the brushless DC motor, thereby maintaining the rotational speed of the brushless DC motor substantially constant. Specifically, the duty cycle of the voltage pulse that the drive module supplies power to the stator windings of the brushless DC motor is reduced.

As the displacement of the drain pump increases, more and more air enters, at which point the drain pump enters the semi-aqueous half-air operating phase S3. In this stage, especially in the later stage of the drainage process, a small amount of water remains mixed with the air. If the brushless DC motor still rotates the impeller portion at a high speed, the drain pump will generate a larger half-water half. Air noise.

The control method of the DC brushless motor according to the embodiment of the present invention will mainly be directed to the identification of the semi-aqueous half-air stage and the subsequent processing, and the control method of the DC brushless motor according to the embodiment of the present invention will be specifically described below with reference to FIG. .

Then, when the drain pump drains water, the drain pump enters the water emptying stage S4, and accordingly the DC brushless motor becomes idling.

Next, depending on actual needs, there may be a water recovery phase S5, or there may be no water recovery phase S5.

FIG. 6 illustrates a schematic flow diagram of a method 600 of controlling a brushless DC motor in accordance with an embodiment of the present invention.

In step S610, the actual rotational speed of the brushless DC motor is compared with a preset first predetermined rotational speed.

In step S620, it is determined whether the actual rotational speed of the DC brushless motor is greater than the first predetermined rotational speed.

In the case where the actual rotational speed of the DC brushless motor is greater than the first predetermined rotational speed, the control method of the DC brushless motor according to the embodiment of the present invention proceeds to Step S630.

At step S630, the duty cycle of the voltage pulse that supplies power to the stator windings of the brushless DC motor is compared to the first threshold duty cycle.

In step S640, it is determined whether the duty ratio of the voltage pulse is lower than the first critical duty ratio.

In the case where the duty ratio of the voltage pulse is lower than the first critical duty ratio, the control method of the DC brushless motor according to the embodiment of the present invention proceeds to step S650.

In step S650, it is determined that the drain pump enters a semi-aqueous half-air operating state, and the target rotational speed of the direct current brushless motor is set to a second predetermined rotational speed, and the second predetermined rotational speed is lower than the first predetermined rotational speed.

In the control method of the brushless DC motor according to the embodiment of the present invention, the comparison of the duty ratios of the voltage pulses is performed after the rotation speed of the DC brushless motor reaches a preset first predetermined rotation speed. The preset first predetermined rotational speed may be a target rotational speed of the DC brushless motor operation and may be the rated rotational speed, or may be a rotational speed lower than the target rotational speed, for example, the target rotational speed or the rated rotational speed. 90%.

Then, after the drain pump starts to drain, there is a case where there is a mixture of water and air, and the load of the brushless DC motor is reduced, correspondingly through the speed outer ring control sub-module 221 in the control module 22. Controlling, by the current inner loop control sub-module 222, adjusting (specifically, reducing) a duty cycle of a voltage pulse that the drive module supplies power to a stator winding of the brushless DC motor, such that the DC The actual speed of the brush motor is basically the same as the target speed.

As described above, since the load of the DC brushless motor becomes smaller as the displacement of the drain pump increases, the duty of the voltage pulse supplied by the drive module to the stator winding of the brushless DC motor is The ratio is also reduced.

By setting a predetermined first critical duty ratio, when the duty ratio of the voltage pulse supplied by the driving module to the stator winding of the brushless DC motor is gradually reduced to the first critical duty ratio, The control module 22 can determine that the DC brushless motor enters a semi-aqueous half-air state, and at this time, the target rotating speed of the drain brush DC brushless motor can be reduced, thereby reducing the half-water and half-air noise of the drain pump. The first critical duty ratio here is only a set value, in fact, as long as the drain pump starts to drain, the DC brushless motor enters a water and air mixed state, but at this time the proportion of air is small and the said The noise generated by the drain pump is within the allowable range. For example, the predetermined first critical duty ratio may be selected according to the noise generated by the drain pump, or may be The proportion of air is chosen.

As described above, when the DC brushless motor is in an idle operation state, the duty ratio of the voltage pulse for supplying power to the stator winding of the brushless DC motor is the first duty ratio; When the brush motor is in the rated load operating state, the duty ratio of the voltage pulse for supplying power to the stator winding of the brushless DC motor is the second duty ratio, and the second duty ratio is greater than the first duty ratio . As an example, the first threshold duty ratio may be selected as a value between the first duty ratio and the second duty ratio, for example, 70% of the second duty ratio, ie, The first critical duty ratio is greater than the first duty cycle and less than the second duty cycle.

When the duty ratio of the voltage pulse for supplying power to the stator winding of the brushless motor of the DC brushless motor is between the first threshold duty ratio and the second duty ratio, the DC is still considered The brushless motor does not enter the semi-aqueous half air state, and the target rotational speed of the DC brushless motor remains unchanged.

Determining that the drain pump DC brushless motor enters a half when the duty ratio of the voltage pulse supplied by the driving module to the stator winding of the brushless DC motor is reduced to be equal to or lower than the first threshold duty ratio a water semi-air state, and at this time, lowering a target rotational speed of the drain pump DC brushless motor, for example, setting a target rotational speed at this time to the second predetermined rotational speed, the second predetermined rotational speed being, for example, the 40% to 60% of the rated speed.

Thus, by reducing the target rotational speed of the drain brush DC brushless motor after entering the semi-aqueous half-air state, the semi-aqueous half-air noise generated by the drain pump in the semi-aqueous half-air state in the late stage of drainage can be reduced, and The remaining water can still be completely drained.

As a specific application, when the DC brushless motor is stably operated under a rated load, after the rotation speed thereof reaches a first predetermined rotation speed, the duty ratio of the voltage pulse is lower than the first critical duty ratio. In the case, the control module 22 determines that the drain pump enters the semi-aqueous half-air operating state, and sets the target rotational speed of the DC brushless motor to the second predetermined rotational speed.

In addition, according to an embodiment of the present invention, not only a critical duty ratio but also two critical duty ratios may be set, for example, the first duty ratio < the lower critical duty ratio < the upper critical duty ratio < the second occupied a ratio of a target speed of the brushless DC motor to a first intermediate speed when the duty ratio of the voltage pulse decreases to be equal to or lower than the upper threshold duty ratio, and the voltage pulse is When the duty ratio is reduced to be equal to or lower than the lower critical duty ratio, the target rotational speed of the brushless DC motor is reduced to a second intermediate rotational speed, and the first intermediate rotational speed is greater than the second intermediate rotational speed.

Furthermore, in the control method of the brushless DC motor according to the embodiment of the present invention, a predetermined second critical duty ratio may be set, and the second critical duty ratio is lower than the first critical duty ratio, And the first critical duty ratio and the second critical duty ratio constitute a duty cycle interval of the semi-aqueous half air operating state. When the duty ratio of the voltage pulse for supplying power to the stator winding of the brushless motor of the DC brushless motor is reduced to be equal to or lower than the second critical duty ratio, the drain pump drainage may be substantially considered to be completed, and The original target speed of the brushless DC motor can be recovered. At this time, the drain pump can enter the water emptying stage S4.

Specifically, the control method 600 of the brushless DC motor according to the embodiment of the present invention may further include step S660 (not shown) after step S650.

In step S660, comparing the duty ratio of the voltage pulse supplied by the driving module to the stator winding of the brushless DC motor to the second threshold duty ratio, the duty ratio of the voltage pulse is lower than In the case of the second critical duty ratio, the control unit 22 sets the target rotational speed of the brushless DC motor to a third predetermined rotational speed, wherein the second critical duty ratio is greater than the first duty cycle And smaller than the first critical duty ratio, the third predetermined rotational speed being higher than the second predetermined rotational speed.

In a specific application, the first predetermined rotational speed may be equal to or lower than a rated rotational speed of the brushless DC motor, and the third predetermined rotational speed may be equal to a rated rotational speed of the DC brushless motor.

Fig. 7 shows a schematic block diagram of a control device 700 for a DC brushless motor for a drain pump according to an embodiment of the present invention.

As shown in FIG. 7, the control device 700 for a DC brushless motor for a drain pump according to an embodiment of the present invention may include a duty ratio comparison unit 710 and a target rotation speed setting unit 720.

The duty ratio comparing unit 710 compares the duty ratio of the voltage pulse for supplying the stator winding of the brushless DC motor with the first critical duty ratio after the speed of the brushless DC motor reaches the first predetermined speed. And get the first comparison result.

The target rotation speed setting unit 720 determines that the drain pump enters the semi-aqueous half air operation state in a case where the first comparison result indicates that the duty ratio of the voltage pulse is lower than the first critical duty ratio, and The target rotational speed of the brushless DC motor is set to a second predetermined rotational speed, wherein the second predetermined rotational speed is lower than the first predetermined rotational speed.

According to an embodiment of the present invention, when the DC brushless motor is in an idle operation state, a duty ratio of a voltage pulse for supplying power to a stator winding of the brushless DC motor is a first duty ratio; When the brushless motor is in the rated load operating state, the duty ratio of the voltage pulse for supplying power to the stator winding of the brushless DC motor is the second duty ratio; wherein the first critical duty The ratio is greater than the first duty cycle and less than the second duty cycle.

According to an embodiment of the present invention, after the rotational speed of the brushless DC motor in the rated load operating state reaches the first predetermined rotational speed, the target rotational speed setting unit 720 indicates that the duty ratio of the voltage pulse is low at the first comparison result. In the case of the first critical duty ratio, it is determined that the drain pump enters a half-water half-air operating state, and the target rotating speed of the DC brushless motor is set to the second predetermined rotational speed.

Further, the duty ratio comparison section 710 compares the duty ratio of the voltage pulse supplied to the stator winding of the brushless DC motor with the second critical duty ratio, and obtains a second comparison result. In this case, the target rotational speed setting unit 720 further targets the DC brushless motor if the second comparison result indicates that the duty ratio of the voltage pulse is lower than the second critical duty ratio. The rotation speed is set to the third predetermined rotation speed, wherein the second critical duty ratio is greater than the first duty ratio and is less than the first critical duty ratio, the third predetermined rotation speed being higher than the The second predetermined rotational speed, and the first critical duty ratio and the second critical duty ratio constitute a duty cycle interval of the semi-aqueous half air operating state.

A control method and a control device for a DC brushless motor for a drain pump and a DC brushless motor system for a drain pump according to an embodiment of the present invention, which pass the speed of the DC brushless motor, have been described with reference to FIGS. After the preset rotational speed is reached, the duty ratio of the voltage pulse for supplying power to the stator winding of the brushless DC motor is compared with a preset critical duty ratio corresponding to the semi-aqueous half air state critical judgment point of the drain pump Determining whether the drain pump enters a semi-aqueous half-air state, and further reducing a target rotational speed of the DC brushless motor in a case where the drain pump is judged to enter a semi-aqueous half-air state, thereby reducing the generation of the drain pump The semi-aqueous half-air noise, and at the same time, also enables the drain pump to completely drain the remaining water.

Various embodiments of the present invention have been described in detail above. However, it will be understood by those skilled in the art that various modifications, combinations and sub-combinations of the embodiments may be made without departing from the spirit and scope of the invention.

This application claims priority from China Priority Application filed on April 11, 2014, with the application number "CN 201410147211.8" and the invention name "DC brushless motor system for drain pump, and its control method and control device". The entire content is incorporated herein.

Claims

A control method for a DC brushless motor for a drain pump, comprising: after the rotational speed of the DC brushless motor reaches a first predetermined rotational speed,

Comparing a duty cycle of a voltage pulse that supplies power to a stator winding of the brushless DC motor to a first critical duty cycle;

In a case where the duty ratio of the voltage pulse is lower than the first critical duty ratio, determining that the drain pump enters a semi-aqueous half-air operating state, and setting a target rotating speed of the DC brushless motor to a first Two predetermined speeds,

Wherein the second predetermined rotational speed is lower than the first predetermined rotational speed.
The control method according to claim 1, wherein

When the DC brushless motor is in an idle operation state, a duty ratio of a voltage pulse for supplying power to a stator winding of the brushless DC motor is a first duty ratio;

When the DC brushless motor is in a rated load operating state, a duty ratio of a voltage pulse for supplying power to a stator winding of the brushless DC motor is a second duty ratio;

Wherein the first critical duty ratio is greater than the first duty cycle and less than the second duty cycle.
The control method according to claim 1, wherein

Determining that the drain pump enters a semi-aqueous half-air operating state when the duty ratio of the voltage pulse continues to decrease and is lower than the first critical duty ratio, and targets the DC brushless motor The rotational speed is set to a second predetermined rotational speed.
The control method according to claim 1, wherein

After the speed of the DC brushless motor in the rated load operation state reaches the first predetermined rotation speed, the drainage is determined only when the duty ratio of the voltage pulse is lower than the first critical duty ratio. The pump enters a semi-aqueous half air operating state, and sets a target rotational speed of the direct current brushless motor to the second predetermined rotational speed.
The control method of claim 4, further comprising:

Setting a target rotational speed of the drain pump DC brushless motor to the third predetermined in a case where a duty ratio of a voltage pulse supplied from a stator winding of the brushless DC motor continues to decrease to a second critical duty ratio Speed, where,

The second critical duty ratio is greater than the first duty cycle and is less than the first critical duty ratio,

The third predetermined rotational speed is higher than the second predetermined rotational speed.
The control method according to claim 5, wherein

The first predetermined rotational speed is equal to or lower than a rated rotational speed of the brushless DC motor, and the third predetermined rotational speed is equal to a rated rotational speed of the DC brushless motor.
A control device for a DC brushless motor for a drain pump, comprising:

a duty ratio comparison component that performs a duty cycle of a voltage pulse for supplying power to a stator winding of the brushless DC motor and a first critical duty ratio after the rotation speed of the DC brushless motor reaches a first predetermined rotation speed Compare and get the first comparison result;

a target rotation speed setting unit that determines that the drain pump enters a half-water half air operation state in a case where the first comparison result indicates that a duty ratio of the voltage pulse is lower than the first critical duty ratio, and Setting a target rotational speed of the brushless DC motor to a second predetermined rotational speed,

Wherein the second predetermined rotational speed is lower than the first predetermined rotational speed.
The control device according to claim 7, wherein

When the DC brushless motor is in an idle operation state, a duty ratio of a voltage pulse for supplying power to a stator winding of the brushless DC motor is a first duty ratio;

When the DC brushless motor is in a rated load operating state, a duty ratio of a voltage pulse for supplying power to a stator winding of the brushless DC motor is a second duty ratio;

Wherein the first critical duty ratio is greater than the first duty cycle and less than the second duty cycle.
The control device according to claim 7, wherein

After the speed of the DC brushless motor in the rated load operating state reaches the first predetermined speed, the target speed setting component indicates that the duty ratio of the voltage pulse is lower than the first threshold in the first comparison result. In the case of the air ratio, it is judged that the drain pump enters a half-water half air operation state, and the target rotation speed of the DC brushless motor is set to the second predetermined rotation speed.
The control device according to claim 9, wherein said duty ratio comparing means compares a duty ratio of a voltage pulse for supplying power to a stator winding of said brushless DC motor with a second critical duty ratio, and Obtaining a second comparison result;

The target rotational speed setting unit further sets a target rotational speed of the DC brushless motor to the first in a case where the second comparison result indicates that a duty ratio of the voltage pulse is lower than a second critical duty ratio Three predetermined speeds, of which

The second critical duty ratio is greater than the first duty cycle and is less than the first critical duty cycle,

The third predetermined rotational speed is higher than the second predetermined rotational speed.
The control device according to claim 10, wherein

The first predetermined rotational speed is equal to or lower than a rated rotational speed of the brushless DC motor, and the third predetermined rotational speed is equal to a rated rotational speed of the DC brushless motor.
A DC brushless motor system for a drain pump, comprising:

A brushless DC motor comprising: a stator assembly and a rotor assembly, the stator assembly including a stator core and stator windings wound in the stator core slots, the rotor assembly including rotor poles;

a motor control system comprising: a drive module, a position detection module and a control module,

The position detecting module detects a position of a rotor magnetic pole in the DC brushless motor, and the control module calculates an actual rotational speed of the rotor magnetic pole according to the position of the rotor magnetic pole detected by the position detecting module, and according to a target rotational speed of the brushless DC motor and an actual rotational speed output of the DC brushless motor for controlling a control pulse signal of the driving module;

Wherein, when the duty ratio of the voltage pulse outputted by the driving module is lower than the first critical duty ratio, the control module determines that the drain pump enters a semi-aqueous half air state, and lowers the DC brushless motor The target speed.
A DC brushless motor system for a drain pump according to claim 12, wherein

The number of stator core slots is the same as the number of rotor poles, and the radial air gap formed by the rotor poles and the stator core is a non-uniform air gap.
A DC brushless motor system for a drain pump according to claim 12, wherein

The drive module includes an H-bridge inverter;

The control pulse signal output by the control module is a switch control pulse signal for controlling four switches in the H-bridge inverter.
A DC brushless motor system for a drain pump according to claim 12, wherein a duty of a voltage pulse outputted by said control module at said drive module after said rotational speed of said brushless DC motor reaches a first predetermined rotational speed When the ratio is lower than the first critical duty ratio, determining that the drain pump enters a semi-aqueous half air state, and setting a target rotational speed of the DC brushless motor to a second predetermined rotational speed,

Wherein the second predetermined rotational speed is lower than the first predetermined rotational speed.
A DC brushless motor system for a drain pump according to claim 15, wherein

The output of the driving module when the DC brushless motor is in an idle operation state The duty cycle of the pressure pulse is a first duty cycle;

When the DC brushless motor is in a rated load operating state, a duty ratio of a voltage pulse output by the driving module is a second duty ratio;

Wherein the first critical duty ratio is greater than the first duty cycle and less than the second duty cycle.
A DC brushless motor system for a drain pump according to claim 15, wherein

After the speed of the DC brushless motor in the rated load operating state reaches the first predetermined speed, the control module is only when the duty ratio of the voltage pulse is lower than the first threshold duty ratio. It is judged that the drain pump enters a half-water half-air operating state, and the target rotational speed of the DC brushless motor is set to the second predetermined rotational speed.
A DC brushless motor system for a drain pump according to claim 15, wherein

In a case where the duty ratio of the voltage pulse supplied by the stator winding of the brushless DC motor continues to decrease to the second critical duty ratio, the control module sets the target rotational speed of the drain brush DC brushless motor to Said third predetermined rotational speed, wherein

The second critical duty ratio is greater than the first duty cycle and is less than the first critical duty cycle,

The third predetermined rotational speed is higher than the second predetermined rotational speed.
A DC brushless motor system for a drain pump according to claim 18, wherein

The first predetermined rotational speed is equal to or lower than a rated rotational speed of the brushless DC motor, and the third predetermined rotational speed is equal to a rated rotational speed of the DC brushless motor.