Motor control method

Abstract

To provide a control method of a motor which can certainly stop the motor while suppressing vibration.SOLUTION: In a control method of a motor according to the present invention, when the fan motor 10 is stopped, a control board 20 performs: a first step of reducing drive voltage of a fan motor 10 which is used for an apparatus for a house facility to a voltage value (V3+ΔV) which is a voltage value equal to or more than an upper limit of tolerance of nominal voltage so that engine speed of the fan motor 10 becomes equal to or less than predetermined engine speed; and a second step of gradually reducing the drive voltage from the voltage value (V3+ΔV) .SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for controlling a motor used in a household appliance. [Background technology]

[0002] Conventionally, household equipment such as hot water heaters, washer-dryers, and outdoor units of air conditioners have fans installed inside the equipment. The fans are driven by motors and their rotation is controlled.

[0003] For example, the air conditioner of Patent Document 1 has a compressor, a pressure reducer, an indoor heat exchanger, an outdoor heat exchanger, and a four-way valve connected by piping. The compressor is equipped with a drive motor, which has a rotor. The indoor heat exchanger exchanges heat by air blown by an indoor fan.

[0004] In this air conditioner, when an instruction to stop operation is given, the compressor speed is changed to a compressor speed where the control amount of torque control is equal to or greater than a certain value, and then the compressor is stopped at the rotor position that is optimal for suppressing vibration when the compressor is stopped (Patent Document 1 / "Disclosure of the Invention", Figure 3A). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2004 / 083744 Summary of the Invention [Problem to be solved by the invention]

[0006] In the air conditioner described above, the motor rotation is stopped after the rotation speed is reduced to a predetermined value, but the threshold drive voltage at which the motor stops varies depending on the manufacturing process. Therefore, depending on the voltage characteristics of the motor, the predetermined rotation speed may remain relatively high, and if the drive is stopped from that state, the vibration suppression effect may be small.

[0007] In addition, motor output is generally controlled by PWM output voltage instructions from the product's control board.Due to its characteristics, PWM control causes the radio wave waveform to fluctuate within a certain range even at a constant instruction value, and when this range crosses the drive voltage threshold at which the motor stops driving, the motor repeatedly turns on and off, causing the problem of chattering.

[0008] The present invention has been made in view of the above background, and has as its object to provide a motor control method that can reliably stop the motor while suppressing vibration. [Means for solving the problem]

[0009] In order to achieve the above object, the motor control method of the present invention is a motor used in a household equipment device, and a method for controlling the rotation of the motor. PWM output voltage indication and a motor control means for controlling the motor, The motor control means includes a first step of lowering a drive voltage indicating the rotation speed of the motor to a voltage value of a first threshold value so that the rotation speed of the motor is lower than that during normal driving when stopping the motor; The driving voltage is decreased at a rate lower than that in the first step. and a second step of causing The first threshold value is set to a voltage value equal to or greater than the upper limit of the allowable nominal voltage of the drive voltage at which the motor stops driving.

[0010] When stopping the motor in the motor control method of the present invention, the motor control means reduces the drive voltage at which the motor stops driving to a voltage value of a first threshold (greater than or equal to the upper limit of the allowable nominal voltage) taking into account the allowable value of the nominal voltage (manufacturing variation) (first step). This causes the motor rotation speed to be lower than during normal driving.

[0011] Next, the motor control means gradually reduces the drive voltage from the first threshold voltage value (second step). As a result, the drive voltage at which the motor stops is passed while gradually reducing the rotation speed, so the motor can be stopped reliably while suppressing vibration.

[0012] In the motor control method of the present invention, In the first step, the motor control means preferably immediately reduces the drive voltage to the first threshold voltage value and maintains it there for a certain period of time.

[0013] In the first step, the motor control means immediately reduces the motor drive voltage to a first threshold voltage value to reduce the motor rotation speed and maintains that state for a certain period of time, thereby stabilizing the motor rotation at a low rotation speed, and then proceeds to the second step.

[0014] In addition, in the motor control method of the present invention, In the second step, the motor control means preferably reduces the drive voltage to a second threshold voltage value that is equal to or less than the lower limit of the allowable value of the nominal voltage.

[0015] In the second step, the motor control means gradually reduces the drive voltage of the motor until it reaches a voltage value of a second threshold (below the lower limit of the allowable nominal voltage). As a result, regardless of the drive voltage at which the motor stops driving within the allowable range, the output can be reduced to the drive voltage that is optimal for suppressing vibration, and then the motor can be stopped.

[0016] Furthermore, the PWM control allows for very short fluctuations in the drive voltage, which causes the motor to stop driving, and therefore vibrations and noise caused by chattering can be suppressed.

[0017] In addition, in the motor control method of the present invention, When the rotation of the motor stops or becomes equal to or lower than a predetermined number of rotations in the second step, the motor control means preferably turns off the drive voltage.

[0018] When the drive voltage is gradually decreased in the second step, the rotation of the motor stops during the process, in which case the motor control means can turn off the drive voltage to prevent a load from being applied to the motor. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram of a fan device according to an embodiment of the present invention. [Figure 2] 5A and 5B are diagrams illustrating a method for controlling (stopping) a motor of a fan device. [Figure 3] 10 is a flowchart of a motor stop process. DETAILED DESCRIPTION OF THE INVENTION

[0020] A fan device 1 according to a motor control method of the present invention will be described below with reference to the drawings.

[0021] Figure 1 shows a schematic diagram of a fan device 1. The fan device 1 includes a fan motor 10 for a fan and a control board 20 that controls the rotational drive of the fan motor 10. The fan device 1 is used in household equipment such as heaters, water heaters, washer-dryers, and outdoor units of air conditioners.

[0022] The fan motor 10 is composed of a motor drive circuit 11, a coil 13, and a Hall element 15. The motor drive circuit 11 receives a voltage signal (output command value Vsp) from a control board 20 and passes a current through the coil 13. This generates an electromotive force in the coil 13, causing the fan to rotate.

[0023] The Hall element 15 is a sensor that detects the number of rotations (rotational speed) of the fan. Information on the number of rotations is output to the control board 20. Note that instead of the Hall element 15, a sensor such as a rotary encoder or a resolver may be used.

[0024] The control board 20 is equipped with a controller 21. The controller 21 is an electronic circuit unit composed of a CPU, memory, various interface circuits, etc., and controls the operation of the fan motor 10 by executing a control program for the fan motor 10 stored in the memory with the CPU.

[0025] Next, a method for controlling the fan motor 10 of the fan device 1, particularly a process for stopping the fan motor 10, will be described with reference to FIG.

[0026] When stopping a motor, if the drive voltage (output command value Vsp) is immediately cut off, the motor's rotation speed drops sharply. This causes vibrations in the motor, which are then transmitted to surrounding components, causing abnormal noise. In particular, with sinusoidal drive motors, a back electromotive force is generated when the drive voltage is cut off, which can cause large vibrations due to the braking force.

[0027] As explained in the background art, one possible approach is to reduce the motor rotation speed to a certain extent before cutting off the voltage. However, because the drive voltage (nominal voltage) at which the motor stops has a tolerance (manufacturing variation), it is difficult to accurately set the optimal drive voltage that can suppress vibration.

[0028] Therefore, in this embodiment, the motor drive voltage is controlled as described below. The dashed line in Figure 2 indicates the Vsp command value (set value) of the drive voltage. The drive voltage V2 is the nominal voltage (e.g., 2.1 V) at which the fan motor 10 stops.

[0029] 2, the motor stop process starts at time T=t1 [s]. First, the control board 20 (controller 21) reduces the drive voltage of the fan motor 10 to a voltage V3 that exceeds the nominal voltage V2, or to a value just above that (V3+ΔV), taking into account manufacturing variations in the nominal voltage (the "first threshold" of the present invention).

[0030] By setting voltage V3 to the upper limit of the allowable nominal voltage of fan motor 10 (for example, 2.3 [V]), fan motor 10 can be driven at a lower speed than during normal operation, with little effect from errors in nominal voltage V2.

[0031] In FIG. 2, the control board 20 immediately reduces the drive voltage to (V3 + ΔV) and then maintains it for a certain period of time (time T = t1 to t2). After reducing the drive voltage to V3, it may also be maintained for a certain period of time. This allows the fan motor 10 to stabilize at a lower rotation speed than during normal operation, before proceeding to the next step. The rotation speed of the fan motor 10 is indicated by a thin solid line in FIG. 2.

[0032] Next, from time T=t2 onwards, the drive voltage is gradually reduced from (V3+ΔV). Here, the control board 20 reduces the drive voltage to drive voltage V1, which is lower than nominal voltage V2, or to a voltage (V1-ΔV') lower than that (the "second threshold" of the present invention).

[0033] By setting voltage V1 to a voltage value (e.g., 1.9 V) that is below the lower limit of the allowable nominal voltage of fan motor 10, there is little effect from errors in nominal voltage V2. In FIG. 2, control board 20 (controller 21) gradually reduces the drive voltage to (V1-ΔV'). At this time, the waveform of the Vsp command value gradually decreases, and the rotation speed of fan motor 10 also gradually decreases. Then, by the time T=t3, the drive voltage falls below the voltage at which fan motor 10 stops, and drive of fan motor 10 stops.

[0034] Thereafter, at time T=t3, the drive voltage is turned off (shut off). In this way, when stopping fan motor 10, a step is provided in which the drive voltage (waveform of Vsp command value) is gradually reduced so that the rotation speed gradually decreases, preventing abnormal noise and chattering when stopping fan motor 10 and ensuring that fan motor 10 is stopped reliably.

[0035] In the step of gradually decreasing the drive voltage, the software is set so that the waveform of the Vsp command value is stepped. Of course, a curved (downward convex) Vsp waveform may also be used. The control board 20 may change the rate at which the drive voltage is reduced midway based on information about the rotation speed of the fan motor 10.

[0036] Next, a flow chart of the motor stop process of the fan device 1 will be described with reference to FIG.

[0037] First, the control board 20 of the fan device 1 reduces the voltage until the drive voltage of the fan motor 10 reaches (V3+ΔV) (STEP 01, the "first step" of the present invention). This causes the fan motor 10 to rotate at a lower speed than during normal operation. Then, the process proceeds to STEP 02.

[0038] Next, the control board 20 determines whether the drive voltage has reached (V3+ΔV) (STEP 02). If the drive voltage has reached (V3+ΔV), the process proceeds to STEP 03. If the drive voltage has not yet reached (V3+ΔV), the voltage is reduced until it reaches (V3+ΔV).

[0039] When the drive voltage reaches (V3+ΔV) ("YES" in STEP 02), the control board 20 determines whether a predetermined time has elapsed (STEP 03). The predetermined time is the time required to stabilize the fan motor 10 at a lower rotation speed than during normal operation. If the predetermined time has elapsed, the process proceeds to STEP 04; if not, the process waits until the time has elapsed.

[0040] Instead of determining whether a predetermined time has elapsed, it may be determined whether the rotation speed of the fan motor 10 has decreased to a predetermined rotation speed. If the rotation speed has decreased to the predetermined rotation speed, the process proceeds to STEP 04, and if the rotation speed has not yet reached the predetermined rotation speed, the process waits until it reaches the predetermined rotation speed.

[0041] 2. The Vsp command value from time T=t1 to time T=t2 is not limited to the dashed line. For example, it may be a linear or curved waveform that is reduced to the drive voltage (V3+ΔV) in a short time and maintained until time T=t2, as long as the rotation of fan motor 10 is stable at the low rotation speed at time T=t2.

[0042] Next, the control board 20 gradually reduces the drive voltage of the fan motor 10 until it reaches (V1-ΔV') (STEP 04). This is the gradual reduction of the drive voltage that occurs from time T=t2 to time T=t3 in FIG. 2 (the "second step" of the present invention). As a result, regardless of the drive voltage at which the fan motor 10 stops driving or stopping within the allowable range, it is possible to reduce the output to a drive voltage that is optimal for vibration suppression while preventing chattering. Therefore, it is possible to reliably stop the fan motor 10 while suppressing vibration. Then, proceed to STEP 05.

[0043] Next, the control board 20 determines whether the drive voltage has reached (V1-ΔV') (STEP 05). If the drive voltage has reached (V1-ΔV'), the process proceeds to STEP 06. If the drive voltage has not yet reached (V1-ΔV'), the voltage is reduced until it is reached.

[0044] Here again, instead of determining whether the drive voltage has reached (V1-ΔV'), it may be determined whether the rotation speed of the fan motor 10 has decreased to a predetermined rotation speed. If the rotation speed has decreased to the predetermined rotation speed, the process proceeds to STEP 06, and if the predetermined rotation speed has not yet been reached, the process waits until it is reached.

[0045] Finally, when the drive voltage reaches (V1-ΔV') or drops to a predetermined rotation speed (YES in STEP 05), the control board 20 turns off the drive voltage (STEP 06).

[0046] As described above, the present invention is not limited to the above-described embodiment and modifications, and can be embodied in various forms without departing from the spirit of the present invention.

[0047] The tolerance for the nominal voltage V2 is usually about ±10%, but the voltages V1 and V3 may be determined to be ±5 to 15%. Also, ΔV and ΔV' may be set to 5% or less of the nominal voltage V2. [Explanation of symbols]

[0048] 1 Fan unit 10 Fan motor 11 Motor drive circuit 13 Coil 15 Hall element 20 Control board 21 Controller

Claims

1. The device comprises a motor used in a household equipment device and a motor control means for controlling the rotational drive of the motor by a voltage command of a PWM output, When the motor control means stops the motor, a first step of reducing a drive voltage indicating a rotation speed of the motor to a voltage value of a first threshold value so that the rotation speed of the motor is lower than that during normal driving; a second step of reducing the driving voltage from the first threshold voltage value at a rate lower than the rate of reduction of the driving voltage in the first step; A motor control method, characterized in that the first threshold value is set to a voltage value equal to or greater than an upper limit of the allowable nominal voltage of the drive voltage at which the motor stops driving.

2. 2. The motor control method according to claim 1, wherein in the second step, the motor control means reduces the drive voltage to a second threshold voltage value that is equal to or lower than a lower limit of the allowable value of the nominal voltage.

3. 3. The motor control method according to claim 1, wherein if the rotation of the motor stops or the rotation speed drops below a predetermined number in the second step, the motor control means turns off the drive voltage.

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