JP2971112B2 - Washing machine - Google Patents

Description

Description: Object of the Invention (Industrial application field) 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 washing machines have been developed for the purpose of improving the washing rate and reducing noise. Among them, a washing machine that uses a DC brushless motor to drive the pulsator can freely change the rotation speed of the pulsator, leading to an improvement in the cleaning rate.In addition, the brushless motor reduces the noise of the motor itself. It has the advantage of being able to reduce noise.

As the DC brushless motor, a motor having a three-phase armature winding is generally used. The DC brushless motor is provided with a rotor formed of a permanent magnet and a Hall element for detecting the rotational position of the rotor. As a power supply for driving the DC brushless motor, a three-phase full-wave bridge type inverter is generally used. The three-phase full-wave bridge type inverter includes six transistors (switching elements) respectively connected to three pairs of arms corresponding to three phases. The three-phase full-wave bridge type inverter converts an input DC voltage into a three-phase AC synchronized with the rotor position detected by the Hall element, and supplies the AC to a three-phase armature winding. The rotation continues. At this time, among the three transistors connected to one and the other arms of the three pairs of arms, the transistors of the three-phase full-wave bridge type inverter each have a required combination corresponding to the rotor position one by one. Turn on.

During the washing and rinsing steps of the washing machine, the DC brushless motor that drives the pulsator repeats forward rotation, stoppage, reverse rotation, and stoppage. Stopping the DC brushless motor is considered to turn off all six transistors of the three-phase full-wave bridge inverter. In this method, the motor is stopped by a mechanical loss of a bearing or the like. Electrically, energy for rotating the motor remains in the armature winding. Therefore, it takes a relatively long time from turning off all the transistors to stopping the motor, and the motor rotates in a steady state (1500 rpm, 15 kgcm)
In this case, it takes about one or two seconds from the stop command to the stop of the pulsator.

Recent studies have shown that when the pulsator is turned forward and reverse in a short cycle, for example, 1 second forward, 0.5 second stop, 1 second reverse, 0.5 second stop, the cleaning rate increases. However, as described above, in the method in which all six transistors are turned off to stop the motor, there is no longer a period in which the motor is stopped in such a short-period positive / reverse operation, and an improvement in the cleaning rate can be expected. Absent.

On the other hand, when the DC brushless motor is stopped, of the six transistors constituting the three-phase full-wave bridge type inverter, a brake that simultaneously turns on three transistors connected to any one arm in each phase. It is considered to set the mode. In this brake mode, not only the mechanical loss of the bearing and the like, but also the armature winding is short-circuited by the transistor and its free-wheel diode and the electrical loss due to the resistance is added, so that the rotation of the motor is stopped in a short time. When this stopping method is adopted, even when a DC brushless motor is used, short-period positive and reverse can be performed, and the cleaning rate can be improved.

However, when stopping the DC brushless motor in the normal rotation or the reverse rotation in the brake mode, in the three-phase full-wave bridge type inverter, first, the rotor position of each of the three transistors connected to one and the other arm is determined. Is switched from the state in which each of the required combinations corresponding to the above is turned on to the state in which three transistors connected to one or the other arm are simultaneously turned on. At this time, the time from when the on / off signal is applied to the transistor until the transistor is actually turned on / off is delayed when the transistor is turned off due to the accumulation time of the transistor. For this reason, a DC power supply in which one of the three transistors in one of the arms for rotating the rotor and the three transistors in the other of the other arms are simultaneously turned on during the transitional state of switching. There is a possibility that a short circuit occurs and an excessive short circuit current as shown in FIG. 4 flows to destroy the transistor. This phenomenon of the DC power supply short-circuit also occurs when the DC brushless motor is restarted from the brake mode to the normal rotation or the reverse rotation.

As switching elements that make up a three-phase full-wave bridge inverter, besides bipolar transistors, MOSFE
Even when T, IGBT, or the like is used, the same phenomenon as described above occurs because OFF is generally delayed from ON.

(Problems to be Solved by the Invention) Conventionally, if a method of stopping all six transistors of a three-phase full-wave bridge type inverter to stop the DC brushless motor is used, short-period positive / inverting cannot be performed and cleaning is performed. I can't raise the rate. Further, when the DC brushless motor in the normal or reverse state is stopped in the brake mode or restarted from the brake mode, there is a problem that a short circuit of the DC power supply occurs and the transistor may be destroyed.

Therefore, the present invention achieves noise reduction by using a DC brushless motor, and also does not destroy the switching element when stopping in the brake mode and restarting from the brake mode even when using the DC brushless motor. It is another object of the present invention to provide a washing machine capable of inverting a pulsator forward and backward in a short cycle and increasing a washing rate.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the problems described above, the present invention provides a DC brushless motor having a three-phase armature winding and driving a pulsator, and a three-phase brushless motor corresponding to three phases. The six-phase switching device connected to each arm of the DC brushless motor converts an input DC voltage into a three-phase AC synchronized with a rotor position of the DC brushless motor and supplies the three-phase AC to an armature winding of the DC brushless motor. When the DC brushless motor and the DC brushless motor are stopped once and then inverted and started again, the six switching elements are temporarily turned off during the temporary stop and the inverted start, and the six switching elements are interposed therebetween. A brake mode to turn on three switching elements connected to one of the arms in each phase simultaneously. And summarized in that and a motor driving means for.

(Operation) When the DC brushless motor is temporarily stopped and subsequently inverted and started, the stop mode in which the six switching elements in the three-phase full-wave bridge inverter are once turned off is set for the temporarily stopped and inverted start. And during this stop mode,
A brake mode for simultaneously turning on three switching elements connected to one of the arms in each phase among the switching elements is set. As a result, an input DC voltage short-circuit state in which the two switching elements connected to the in-phase arm are simultaneously turned on is eliminated, and an excessive short-circuit current is prevented from flowing through the switching elements. Is prevented. The off-time width of the stop mode in which the six switching elements are once turned off may be a short time on the order of ms as long as it exceeds the accumulation time of a transistor or the like which is a switching element. The DC brushless motor can be stopped in a short time, and the pulsator can be rotated forward and backward in a short cycle, so that the cleaning rate can be increased.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

First, a schematic configuration of the washing machine will be described with reference to FIG. In the figure, 1 is a washing machine main body, 2 is a water tub (outer tub) elastically suspended by a suspension 4, and 3 is a dehydration tub that also serves as a washing tub for washing and dewatering laundry, and a number of dehydration tubs are provided on the side surface of the peripheral wall. Holes 6 for draining water. At the bottom of the dewatering tub 3, a pulsator 5 for stirring the laundry and water in the washing and rinsing steps is provided. The mechanism for driving the pulsator 5 includes a mechanical case 7 having a built-in brake and clutch mechanism, and a DC brushless motor 8. The DC brushless motor 8 and the mechanical case 7 side are connected by a V-belt 9 stretched between a motor pulley and a driven pulley on the mechanical case side. The DC brushless motor 8 is connected to the three-phase full-wave bridge type inverter 1 as its power source. Further, when the DC brushless motor 8 is controlled in rotation speed, forward and reverse, and when the DC brushless motor 8 is stopped in the brake mode and restarted from the brake mode, all the transistors in the three-phase full-wave bridge type inverter 10 are temporarily controlled. For example, to turn off and set the stop mode, the three-phase full-wave bridge type inverter 10 is connected to a motor drive circuit 20 as a motor drive means.
A microcomputer 30 for executing a stop mode command, a brake mode command, and the like is connected. The three-phase full-wave bridge inverter 10, the motor drive circuit 20, the microcomputer 30, etc.
It is built in an electronic circuit unit and the like installed below a control panel (not shown) arranged at the upper part of the washing machine main body 1.

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 13 is
It is closed during the water supply, washing, and rinsing steps.

In the washing machine of this embodiment, since the DC brushless motor 8 having a variable rotation speed is used as the drive motor of the pulsator 5, the rotation of the pulsator 5 during the washing, rinsing, and dewatering steps is performed according to the amount of the laundry. The speed can be freely changed, and the cleaning rate and the dewatering rate can be improved.

Next, the internal configuration of the three-phase full-wave bridge inverter 10, the motor drive circuit 20, and the like will be described with reference to FIG.

Reference numeral 16 in the three-phase full-wave bridge inverter 10 denotes a commercial AC power supply. The commercial AC power supply 16 is connected to a rectifier bridge 18 via a reactor 17. An AC voltage from a commercial AC power supply 16 is rectified by a rectifying bridge 18 and then smoothed by a smoothing capacitor 19 to be obtained from an input DC voltage. Then, the input DC voltage is converted into a three-phase AC at a three-phase full-wave bridge portion. That is, in the three-phase full-wave bridge portion, six transistors u ₁ , u ₂ , v ₁ , v ₂ , w ₁ , w ₂ as switching elements are provided on three pairs of arms corresponding to the three phases. It is connected. Hereinafter, for convenience of explanation, three arms on the side to which transistors u ₁ , v ₁ , and w ₁ are connected are upper arms, and three arms on the other side to which other transistors u ₂ , v ₂ , and w ₂ are connected. Is called a lower arm. A free wheel diode 21 is connected in parallel to each of the six transistors u _{1 to} w ₂ , and three connection points of the upper arm and the lower arm are connected to the DC brushless motor 8.
Are connected to the three-phase armature windings u, v, w.

The DC brushless motor 8 includes, in addition to the armature windings u, v, and w, a rotor (not shown) formed of a permanent magnet, and three Hall elements 22 for detecting the rotational position of the rotor.
a, 22b and 22c are provided. Hall elements 22a, 22b, 2
The rotor position detection output 2c is given to the motor control circuit 23 in the motor drive circuit 20. Motor control circuit 23
The outputs of are photocouplers 27a to 27f and drive circuits 28a to 28f
Are applied as drive signals to the bases u ₁ B to w ₂ B of the respective transistors u _{1 to} w ₂ via the gate. Hall elements 22a, 22b, 22c
Rotor position detection output is logically converted by the motor control circuit 23, in response to the rotor position, for example, a transistor in the transistor u ₁ and the lower arm in the upper arm
v ₂ , a drive signal for sequentially turning on the transistors of the respective combinations of the transistors v ₁ and w ₂ and the transistors w ₁ and u ₂ is output. The input DC voltage is converted to three-phase AC by switching on the transistor, and the DC brushless motor 8
Current flows sequentially through the armature windings uv, vw, and wu, so that the DC brushless motor 8 rotates in one direction.

The normal rotation and reversal of the DC brushless motor 8 are performed by reversing the order of the currents flowing through the armature windings u, v, and w. Done. Further, in order to vary the rotation speed of the DC brushless motor 8, a PWM duty variable circuit 25 and a PWM oscillation circuit 26 are provided, and a signal whose pulse width is modulated is output from the PWM oscillation circuit 26 by the output of the PWM duty variable circuit 25. Then, the on-periods of the three transistors u ₁ , v ₁ and w ₁ of the upper arm are made variable by this PWM signal. That is, the shorter the on-period duty of the transistors u ₁ , v ₁ , w ₁ , the lower the rotational speed of the DC brushless motor 8.

31 is a brake circuit for setting the DC brushless motor 8 to the brake mode, 32 is a stop circuit for setting the stop mode, and three transistors u ₂ , v ₂ , w ₂ is set to ON at the same time. Also, stop circuit
By the output of 32, all the transistors u _{1 to} w _{2 that} are in the on state are set to be on.

Next, the operation of the washing machine configured as described above will be described with reference to FIG.

As shown in FIG. 3 (A), located in the pulsator 5 is forward state based on the output of the motor control circuit 23, 1 in the upper arm and lower arm pairs of transistors u ₁ and v _2, v ₁ and
It is assumed that w ₂ , w ₁ and u ₂ are sequentially turned on (FIG. 7A). Stop circuit when reversing pulsator 5
A stop signal is applied to all the transistors that are in the on state by the output of 32, and the transistors are turned off once and set to the stop mode (FIG. 10C). Next, based on the output of the brake circuit 31, the brake signal
The transistors brushes u ₂ , v ₂ , and w ₂ are turned on at the same time, and the DC brushless motor 8 is set to the brake mode and rapidly stops (FIG. 9B). Output period of the stop signal, the photocoupler to storage time of the transistor u ₁ to w ₂
It is determined in consideration of delays of the drive circuits 28a to 28f and the drive circuits 28a to 28f, and is set to, for example, about 10 ms. As a result, the DC brushless motor 8 can be stopped in a short time of about 0.2 seconds. And, by setting the stop mode, the state of the input DC voltage short circuit in which the transistors in the same phase in the upper arm and the lower arm, for example, u ₁ and u ₂ are simultaneously turned on, is eliminated, thereby preventing an excessive short circuit current from flowing. , breakdown of the transistor u ₁ to w ₂ is prevented. After DC brushless motor 8 is stopped by the brake mode, to reverse the rotation of the pulsator 5, from the DC brushless motor 8 when to restart in the reverse direction, is set once to the stop mode, transistor u ₁ to w ₂ is supplied with a drive signal for reverse rotation. This prevents the transistors u _{1 to} w ₂ from being destroyed in the same manner as described above.

FIG. 3B is a modified example of the control mode, in which the DC brushless motor 8 is reliably stopped using two brake signals (FIG. 3B). Even if such a control mode is used, the output period of the stop signal can be defined as short as described above, so that the DC brushless motor 8 can be stopped in the same short time as described above. .

FIG. 3 (C) shows a comparative example, in which DC
The control mode which stops a brushless motor only in a brake mode is shown.

[Effects of the Invention] As described above, according to the present invention, when the DC brushless motor is temporarily stopped and subsequently started to be inverted, the six stops in the three-phase full-wave bridge inverter are used for the temporary stop and the inverted start. A stop mode in which the switching elements are temporarily turned off is set, and during this stop mode, three switching elements connected to any one arm in each phase among the six switching elements are simultaneously turned on. The switching mode is set so that the two switching elements connected to the in-phase arm are turned on at the same time. Can be reliably prevented. Further, the off-time width for temporarily turning off the six switching elements only needs to exceed the accumulation time of a transistor or the like which is a switching element, and can be a short time of ms order. The DC brushless motor can be stopped in a short period of time, and the pulsator can be rotated forward and backward in a short cycle, thereby increasing the cleaning rate. Further, by using the DC brushless motor, the noise reduction of the washing machine can be appropriately achieved.

[Brief description of the drawings]

1 to 3 show an embodiment of a washing machine according to the present invention. FIG. 1 is a configuration diagram showing the entire configuration in cross section and the like, and FIG. 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, and the like, 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: Hall element for detecting rotor position, 31: Brake circuit, 32: Stop circuit, u, v, w: three-phase armature winding, u _{1 to} w ₂ : 6 transistors (switch

Claims (1)

(57) [Claims] 1. A brushless DC motor having three-phase armature windings for driving a pulsator, and six switching elements respectively connected to three pairs of arms corresponding to three phases. A three-phase full-wave bridge inverter that converts the three-phase AC into a three-phase AC synchronized with the rotor position of the brushless motor and supplies the AC to the armature winding of the DC brushless motor; During the temporary stop and the reversal start, the six switching elements are temporarily turned off, and at the same time, the three switching elements connected to one of the arms in each phase among the six switching elements are simultaneously operated. A motor driving means for setting a brake mode to be turned on.