JPH04129594A - Washing machine - Google Patents

Abstract

PURPOSE:To prevent the breakdown of elements by concurrently turning on three switching elements connected to one arm among six switching elements when a DC brush-less motor is stopped, moving the motor to the brake mode at the time of the stop, and once turning off six switching elements when the motor is started. CONSTITUTION:When a pulsator is reversed, a stop signal is fed to transistors in the on-state by the output of a stop circuit 32 to once turn them off, and the stop mode is set. A brake signal is fed to transistors u2, v2, w2 of a lower arm by the output of a brake circuit 31 to concurrently turn them on, and a DC brush-less motor 8 is set to the brake mode and quickly stopped. The input DC voltage short circuit that all transistors of the upper and lower arms are concurrently turned on when the stop mode is set is prevented, the excessive short circuit current is prevented, and the breakdown of the transistors u1-w2 is prevented. When the pulsator is reversed after the motor 8 is stopped in the brake mode, the breakdown of the transistors u1-w2 is likewise prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Field of Industrial Application) The present invention relates to a washing machine, and more particularly to a washing machine in which a pulsator is driven by a direct current (DC) brushless motor.

(Prior Art) In recent years, various types of washing machines have been developed for the purpose of improving cleaning efficiency and reducing noise. Among them, washing machines that use a DCC brushless motor to drive the pulsator can freely vary the rotation speed of the pulsator, leading to improved cleaning efficiency, and since it is brushless, the motor itself has low noise and is quiet. It has the advantage of being configurable.

DCC brushless motors are generally equipped with three-phase armature windings, and are equipped with a rotor made of permanent magnets and a Hall element that detects the rotational position of the rotor. Furthermore, a three-phase full-wave bridge type inverter is generally used as a power source for driving this DC brushless motor. A three-phase full-wave bridge type inverter includes six transistors (switching elements) connected to three pairs of arms corresponding to three phases. The 3-phase full-wave bridge type inverter converts the input DC voltage into 3-phase AC synchronized with the rotor position detected by the Hall element, and supplies this to the 3-phase armature winding to rotate the DCC brushless motor. is set to continue.

At this time, among the three transistors of the three-phase aftereffect bridge type inverter connected to one arm and the other arm of the three pairs, one transistor in a required combination corresponding to the rotor position is turned on sequentially. do.

During the washing and rinsing processes of a washing machine, the DCC brushless motor that drives the pulsator rotates forward, stops, reverses, stops...
is repeated. To stop the DC brushless motor, it is possible to turn off all six transistors of the three-phase full-wave bridge inverter. This method attempts to stop the motor due to mechanical losses such as bearings, and electrically, energy remains in the armature windings to rotate the motor. For this reason, it takes a relatively long time for the motor to stop after all the transistors are turned off, and the motor rotates in a steady state (1500 rpm).
, 15 kg-cm), it will take about 1.2 seconds for the pulsator to stop after the stop command is issued.

In recent research, for example, the pulsator is rotated forward in short cycles, such as forward rotation for 1 second, stop for 0.5 seconds, reverse rotation for 1 second, and stop for 0.5 seconds.
It has been found that inversion increases the cleaning rate. but,
As described above, in the method of stopping the motor by turning off all six transistors, there is no stopping period in such short-cycle positive and reverse cycles, and no improvement in cleaning efficiency can be expected.

On the other hand, when the DCC brushless motor stops, it enters a brake mode that simultaneously turns on three transistors connected to one arm of each phase among the six transistors that make up the three-phase aftereffect bridge type inverter. It is considered to be set. In this braking mode, the motor rotation stops in a short time because the armature winding is short-circuited by the transistor and its freewheel diode, and electrical loss is added due to the resistance. . If this stopping method is adopted, even when a DC brushless motor is used, short-cycle forward and reverse rotation is possible, and the cleaning rate can be improved.

However, when stopping a DCC brushless motor in forward or reverse rotation mode in brake mode, in a three-phase full-wave bridge type inverter, one of the three transistors connected to one arm and the other arm is first transferred to the rotor position. The state is switched from a state in which each of the corresponding required combinations is turned on to a state in which three transistors connected to one or the other arm are simultaneously turned on. At this time, the time it takes for the transistor to actually turn on or off after an on/off signal is applied to the transistor is delayed due to the storage time of the transistor. Therefore, during a switching transient state, one of the three transistors in one arm and the three transistors in the other arm turn on at the same time when the rotor is rotated. If a short circuit occurs, an excessive short circuit current as shown in FIG. 4 may flow, and the transistor may be destroyed. This DC power supply short-circuit phenomenon also occurs when the DCC brushless motor is restarted from the brake mode to the normal rotation or reverse rotation state.

In addition to bipolar transistors, MOSFETs are also used as switching elements that constitute a three-phase full-wave bridge type inverter.
Even when ET, IGBT, etc. are used, the same phenomenon as described above occurs because off-time is generally delayed longer than on-time.

(Problem to be solved by the invention) Conventionally, when all six transistors of a three-phase full-wave bridge type inverter were turned off to stop the DCC brushless motor, short-cycle forward and reverse operations were not possible, resulting in a reduction in cleaning efficiency. I can't raise it. Also, DC in positive and inverted states
When the brushless motor is stopped in the brake mode or restarted from the brake mode, there is a problem in that a DC power supply short circuit may occur and the transistor may be destroyed.

Therefore, the present invention achieves noise reduction by using a DC brushless motor, and also prevents the switching element from being destroyed when stopping in brake mode or restarting from brake mode. An object of the present invention is to provide a washing machine that can increase the cleaning rate by rotating a pulsator between positive and reverse directions in a short period of time.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a DC brushless motor having a three-phase armature winding and driving a pulsator;
The armature winding of the DC brushless motor is equipped with six switching elements each connected to three pairs of arms corresponding to three phases, and converts the input DC voltage into three-phase AC synchronized with the rotor position of the DC brushless motor. A three-phase full-wave bridge type inverter supplies power to the line, and when the DC brushless motor is stopped, three switching elements connected to one arm of one of the six switching elements in each phase are simultaneously activated. and a motor driving means for setting the six switching elements to a brake mode to be turned on and turning off the six switching elements -H when transitioning to the brake mode at the time of stopping and when transitioning from the brake mode to starting. This is the summary.

(Function) When the DC brushless motor is stopped and transferred to the brake mode, and when started from the brake mode, the six switching elements in the three-phase full-wave bridge type inverter are set to the stop mode in which -H is turned off. . This eliminates the input DC voltage short-circuit condition in which two switching elements connected to the arms of the same phase are turned on at the same time, preventing excessive short-circuit current from flowing to the switching elements, and ensuring that the switching elements are not destroyed. is prevented. The off time width of the stop mode, which turns off the six switching elements -H, should exceed the storage time of the switching elements such as transistors (it can be shortened to the order of ms, so the stop mode is set The DC brushless motor can be stopped in a short period of time, and the pulsator can be turned forward and reverse in a short period of time, making it possible to increase the cleaning rate.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3.

First, the general structure of a washing machine will be described using FIG.

In the figure, 1 is the main body of the washing machine, 2 is the suspension 4
3 is a dehydration tank which doubles as a washing tub for washing and dehydrating laundry, and a large number of holes 6 for draining water are bored in the side surface of the peripheral wall thereof. A pulsator 5 is provided at the bottom of the dehydration tank 3 for stirring the laundry and water during the washing and rinsing processes. The mechanism unit that drives the pulsator 5 is composed of a mechanical case 7 containing a brake, clutch mechanism, etc., and a DC brushless motor 8. DCC brushless motor and mechanical case 7
The motor boot and the driven boot on the mechanical case side are connected to each other by a belt 9 that is passed between them. D.C.C.
A three-phase full-wave bridge inverter 10, which is a power source, is connected to the brushless motor. In addition, the rotation speed control, forward and reverse control of the DCC brushless motor, and when the DCC brushless motor is stopped +L in brake mode and restarted from brake mode.
In order to turn off all the transistors in the phase full-wave bridge type inverter 10 and set it to the stop mode, a motor drive circuit 20 as a motor drive means is connected to the three-phase full wave bridge type inverter 10, and the motor A microcomputer 30 for issuing stop mode commands, brake mode commands, etc. is connected to the drive circuit 20. The three-phase full-wave bridge type inverter 10, the motor drive circuit 20, the microcomputer 30, etc. are built into an electronic circuit unit, etc. installed under a control panel (not shown) placed on the top of the washing machine main body 1. There is.

11 is a water supply mechanism with a built-in water supply valve, 12 is a water supply hose, 13 is a drain valve, 14 is a drain hose, and the drain valve 1
3 is closed during the water supply process, washing process, and rinsing process.

In the washing machine of this embodiment, a variable rotation speed DC brushless motor 8 is used as the drive motor for the pulsator 5, so the pulsator 5 is rotated according to the amount of laundry etc. during the washing process, rinsing process and spin-drying process. The speed can be freely varied, and the cleaning rate, dewatering rate, etc. can be improved.

Next, the internal configuration of the three-phase full-wave bridge type inverter 10, motor drive circuit 20, etc. will be described using FIG.

Reference numeral 16 in the three-phase full-wave bridge type inverter 10 is a commercial AC power source, and the commercial AC power source 16 is connected to a rectifier bridge 18 via a reactor]7. After the AC voltage from the commercial AC power supply 16 is rectified by a rectifier bridge 18, it is smoothed by a smoothing capacitor 19 to obtain a human-powered DC voltage. This human-powered direct current voltage is then converted into three-phase alternating current at the three-phase full-wave bridge section. That is, in the three-phase full-wave bridge part,
Six transistors u1u2, v11v2, WIX as switching elements are installed in three pairs of arms corresponding to three phases.
W2 is connected.

Hereinafter, for convenience of explanation, the three arms on the side to which the transistors u1 and vIW are connected will be referred to as the upper arm, and the three arms on the other side to which the other transistors 02, V2, and W2 are connected will be referred to as the lower arm. 6 each transistor uI-W
Freewheel diodes 21 are connected in parallel to each of 2 and 3, and the three connection points of the upper arm and the lower arm are connected to the DCC
3-phase armature winding U, V, W in brushless motor
It is connected to the.

In addition to the armature windings u1v and w, the DCC brushless motor includes a rotor (not shown) made of permanent magnets, and three Hall elements 2 for detecting the rotational position of this rotor.
2a, 22b, and 22c are provided. Hall element 2
2a, 22b.

The rotor position detection output 22c is given to the motor control circuit 23 in the motor drive circuit 20. The output of the motor control circuit 23 is a photocoupler 27a-27f.
and each transistor u via drive circuits 28a to 28f.
It is given as a drive signal to the bases LIIB to W2B of l'=W2. The rotor position detection outputs of the Hall elements 22a, 22b, and 22c are logically converted by the motor control circuit 23, and corresponding to the rotor position, for example, the transistor ul in the upper arm and the transistor v2 in the lower arm, as well as the transistors v1 and W2. , a drive signal that sequentially turns on each combination of transistors WI and u2 is output. By switching on this transistor, the input DC voltage is converted to three-phase AC, and current flows sequentially through the armature windings u-vSv-w and w-u of the DCC brushless motor, causing the DC brushless motor 8 to rotate in one direction. It looks like this.

The forward rotation and reversal of the DC brushless motor 8 are performed by reversing the order of the currents flowing through the armature winding port, y, and W, and this forward and reverse rotation is controlled by the output of the forward rotation/reversal circuit 24. It will be done. In addition, in order to vary the rotational speed of the DCC brushless motor, the PWM duty variable circuit 25 and P
A WM oscillation circuit 26 is provided, and a signal whose pulse width is modulated is output from the PWM oscillation circuit 26 based on the output of the PWM duty variable circuit 25, and the on period of the three transistors ul VIWl of the upper arm is variable by this PWM signal. It is now possible to do so.

That is, the shorter the on-period duty of the transistors uI, vl, wI, the slower the rotation speed of the DC brushless smoke 8 becomes.

31 is a brake circuit for setting the DCC brushless motor in brake mode, 32 is a stop circuit for setting it in stop mode, and the output of the brake circuit 31 causes the three transistors u2 and v2 in the lower arm to be connected.
, w2 are set to on at the same time. Furthermore, all the transistors u1 to w2 that are in the on state are set to off by the output of the stop circuit 32.

Next, the operation of the washing machine configured as described above will be explained using FIG. 3.

As shown in FIG. 3(A), the pulsator 5 is in a forward rotation state based on the output of the motor control circuit 23, and a pair of transistors ul and Vl in the upper and lower arms,
It is assumed that Vl and W2, and WI and u2 are turned on in sequence ((a) in the same figure). When the valseter 5 is inverted, a stop signal is applied to all the transistors that are in the on state by the output of the stop circuit 32, so that they are temporarily turned off and set to the stop mode ((C) in the same figure). Next, a brake signal is applied to the three transistors u2, v2, and w2 of the lower arm based on the output of the brake circuit 31, and they are turned on at the same time, and the DCC brushless motor is set to the brake mode and stops rapidly (see Figure (b))
. During the output period of the stop signal, the transistors u1 to w2
Photocoupler 27g-27f, drive circuit 2
8a to 28f, for example, 1.
It is defined as approximately 0 ms. As a result, the DC brushless motor 8 can be stopped in a short time of about 0.2 seconds. Then, by setting the stop mode, there is no longer a manual DC voltage short circuit in which transistors of the same phase in the upper and lower arms, for example uI and u2, are turned on at the same time, and an excessive short circuit current is prevented from flowing through the transistors. Destruction of u1 to w2 is prevented. After the DCC brushless motor has stopped in the brake mode, when restarting the DC planless motor 8 in the opposite direction in order to reverse the rotation of the pulsator 5, the transistor u1 is activated once the stop mode has been set. ~
A drive signal for reverse rotation is given to w2. This prevents the transistors u1 to w2 from being destroyed in the same way as described above.

FIG. 3(B) shows a modification of the control mode, in which two brake signals are used (FIG. 3(b)) to reliably stop the DCC brushless motor. Even if such a control mode is used, the output period of the stop signal is
As mentioned above, since the short length can be specified, DC
It becomes possible to stop the C brushless motor in almost the same short time as described above.

FIG. 3(C) is shown as a comparative example, and DC
This shows a control mode in which the motor is stopped only in the C brushless motor brake mode.

[Effects of the Invention] As explained above, according to the present invention, when the DC brushless motor is stopped and transferred to the brake mode, and when the DC brushless motor is restarted from the brake mode, the Since the motor is equipped with a motor drive means that temporarily turns off two switching elements, the input DC voltage short-circuit condition in which two switching elements connected to the arms of the same phase are turned on at the same time is eliminated, and an excessive short-circuit current flows. It is possible to reliably prevent damage to the switching element due to In addition, the off-time width for once turning off the six switching elements only needs to exceed the storage time of the switching elements such as transistors (this off-time width can be set to 111 ms of ms). Even if a DCC brushless motor is installed, it can be stopped in a short time, and the pulsator can be turned forward and reverse in a short period of time, increasing the cleaning rate.Furthermore, by using a DCC brushless motor, the washing machine becomes quieter. can be appropriately achieved.

[Brief explanation of drawings]

Figures 1 to 3 show an embodiment of the washing machine according to the present invention. Figure 1 is a cross-sectional view of the overall configuration, and Figure 2 is a three-phase full-wave bridge type inverter and motor drive. FIG. 3 is a timing chart showing a stop signal, a brake signal, etc., and FIG. 4 is a current waveform diagram showing an excessive short-circuit current flowing through a transistor in a conventional example. 5: Pulsator, 8: DC brushless motor, 10:
3-phase full-wave bridge type inverter, 20: Motor drive circuit (motor drive means), 22a to 22c: Pole element for detecting rotor position, 31 Nibble switch circuit, 32 Nistop circuit, 3-phase armature winding,

Claims (1)

[Claims] A DC brushless motor is equipped with a 3-phase armature winding and drives a pulsator, and is equipped with 6 switching elements each connected to 3 pairs of arms corresponding to 3 phases. a three-phase full-wave bridge type inverter that converts the AC into three-phase AC synchronized with the DC brushless motor and supplies it to the armature winding of the DC brushless motor; The three switching elements connected to one of the arms are set to a brake mode that turns them on simultaneously, and the six switching elements A washing machine comprising a motor drive means for temporarily turning off the switching element of the washing machine.