JP2018201311A - Inverter device for washing machine - Google Patents

Abstract

To provide an inverter device for a washing machine capable of certainly detecting excess current by fewer components.SOLUTION: An inverter device for a washing machine of an embodiment is provided with: an inverter circuit which drives a motor for generating rotation drive force for performing a washing operation; a control circuit which controls the inverter circuit; a plurality of current detection resistors which detect current flowing to the respective phase windings of the motor; a comparison circuit which is used for the control circuit to detect excess current to compare terminal voltage of the plurality of current detection resistors with threshold voltage; and a diode-OR circuit which is arranged between the plurality of current detection circuits and an input terminal of the comparison circuit.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an inverter device that drives a motor that generates a rotational driving force for performing a washing operation.

  Conventionally, in an inverter device that drives a motor of a washing machine, a terminal voltage generated in a current detection resistor for detecting each phase current flowing through the motor is compared with a threshold voltage by a comparator through a CR filter. An overcurrent condition is detected. Since a generally used motor has a three-phase configuration, comparison is made for each phase by three comparators, and an overcurrent is detected by a logical sum output via an OR gate of the comparator outputs.

  The output terminal of the comparator becomes 0 V when showing a low level, but is opened when showing a high level, and is pulled up through a resistor. The comparator output is set to a high level if the phase current is in a normal value range, and is set to a low level if the phase current shows an excessive value. Then, the output of the OR gate becomes a low level, and the driving of the motor is urgently stopped.

Japanese Patent No. 4345553

  However, the above configuration requires as many comparators as the number of phases of the motor. In addition, including a peripheral circuit such as a low-pass filter increases the circuit area and the size of the inverter device. Furthermore, the increase in the number of parts may increase the cost and reduce the reliability of the apparatus.

  Therefore, an inverter device for a washing machine that can reliably detect overcurrent with a smaller number of parts is provided.

According to the inverter device for a washing machine of the embodiment, an inverter circuit that drives a motor that generates a rotational driving force for performing a washing operation;
A control circuit for controlling the inverter circuit;
A plurality of current detection resistors for detecting a current flowing in each phase winding of the motor;
The control circuit is used for overcurrent detection, and a comparison circuit that compares terminal voltages of the plurality of current detection resistors with a threshold voltage;
A diode OR circuit disposed between the plurality of current detection resistors and an input terminal of the comparison circuit;

The circuit diagram which is 1st Embodiment and shows the electric constitution of a washing machine Partial longitudinal side view schematically showing the structure of the washing machine A diagram showing the driving process of a typical washing machine Circuit diagram showing the electrical configuration of the washing machine according to the second embodiment Circuit diagram showing the electrical configuration of the washing machine according to the third embodiment

(First embodiment)
Hereinafter, a first embodiment applied to a washing machine which is a laundry machine will be described with reference to FIGS. 1 to 3. As shown in FIG. 2, the washing machine 10 has a bottomed cylindrical water tank 12 having an open upper surface elastically supported by an elastic suspension mechanism 13 inside an outer box 11 constituting the outer shell. Inside the water tank 12, a bottomed cylindrical rotating tank 14 having an open upper surface is rotatably provided. A reinforcing member 15 for reinforcing the bottom of the rotating tub 14 is provided at the bottom of the rotating tub 14. The rotating tub 14 is configured to rotate around a vertical axis, and serves as a washing tub for washing the laundry and a washing tub in the rinsing step, and a dehydration tub in the dehydration step for dehydrating the laundry. It is also used. That is, the washing machine 10 is a so-called vertical washing machine in which the rotation center axis of the rotating tub 14 extends in the vertical direction.

  The rotating tank 14 has a large number of holes 16 in the peripheral wall portion. These holes 16 penetrate therethrough and allow water and air to pass therethrough. FIG. 1 shows only some of the numerous holes 16. A balance ring 17 made of synthetic resin in which a liquid such as salt water is sealed is attached to the upper part of the rotating tank 14. A pulsator 18 made of synthetic resin, for example, is rotatably provided as a stirring body at the bottom of the rotary tank 14.

  A drainage path 19 is provided in the lower part of the water tank 12. The drainage passage 19 is provided with a drainage valve 20, and when the drainage valve 20 is opened, the water in the water tank 12 is discharged outside the apparatus. An air trap 21 for detecting the water level is provided at the bottom of the water tank 12.

  A driving mechanism 23 is provided at the center of the lower part of the water tank 12. The drive mechanism unit 23 includes a motor 24 and a clutch mechanism unit (not shown). The drive mechanism 23 transmits the rotational force to the pulsator 18 by the clutch mechanism during the washing stroke or the rinsing stroke. For this reason, during the washing process or the rinsing process, the rotary tank 14 is not driven to rotate, and only the pulsator 18 is driven to rotate. Further, the drive mechanism unit 23 transmits the rotational force of the motor 24 to the pulsator 18 and the rotary tank 14 by the clutch mechanism unit during the dehydration process. For this reason, the pulsator 18 is rotationally driven integrally with the rotary tank 14 during the dehydration process.

  A top cover 26 is provided on the top of the outer box 11. The top cover 26 is provided with, for example, a foldable lid 27 that can open and close the laundry doorway. A tank cover (not shown) is attached to the upper part of the water tank 12 so as to be openable and closable. An operation panel 28 is provided at the front portion of the top cover 26. A control unit 29 that controls the overall operation of the washing machine 10 is disposed on the back side of the operation panel 28. The control unit 29 is provided on the front surface side of the outer box 11 in the top cover 26.

  A water supply mechanism 30 that supplies water from the water source into the water tank 12 is provided at the rear portion of the top cover 26. The water supply mechanism 30 includes a water supply valve (not shown), a water supply path (not shown) that communicates with the water tank 12, and the water supply into the water tank 12 is controlled by the control unit 29 controlling the opening and closing of the water supply valve. The

  Next, an electrical configuration relating to the control system of the washing machine 10 will be described. As shown in FIG. 1, the inverter circuit 40 is configured by connecting six IGBTs 41 in a three-phase bridge, and a flywheel diode 42 is connected between the collector and emitter of each IGBT 41. The IGBT 41 corresponds to a switching element. The inverter circuit 40 is supplied with a DC voltage of about 280V generated by double voltage full-wave rectification of a 100V AC power supply. Each phase output terminal of the inverter circuit 40 is connected to each U, V, W phase winding of the motor 24. In the present embodiment, for example, an outer rotor type three-phase brushless DC motor is employed as the motor 24.

  Shunt resistors 43U, 43V, and 43W, which are current detection resistors, are connected between the emitter of the lower arm IGBT 41 and the ground, respectively. The resistance value of the shunt resistor 43 is, for example, 0.22Ω. In the following, the configurations that are symmetric with respect to each phase will be described without adding the symbols “U, V, W” shown in FIG.

  A common connection point between the emitter of the IGBT 41 on the lower arm side and the shunt resistor 43 is connected to the A / D input terminal of the control circuit 45 via the resistor 44. The control circuit 45 is composed of, for example, a single-chip microcomputer and incorporates an A / D converter (not shown). A capacitor 46 is connected between the A / D input terminal and the ground, and the capacitor 46 and the resistor 44 constitute a CR filter.

  The A / D input terminal is pulled up to a 3.3V power supply via a resistor 47. That is, the voltage applied to the A / D input terminal is voltage-divided by the resistor 47, the shunt resistor 43, and the resistor 44 and is level-shifted. These resistors constitute a resistance voltage dividing circuit 48. The same motor phase current as that of the motor winding flows through the shunt resistor 43 at the timing when the lower arm side IGBT 41 is ON. Therefore, the terminal voltage indicates a level corresponding to the motor phase current.

  The emitter of each phase IGBT 41 on the lower arm side is connected to the anodes of three diodes 49U, 49V, and 49W having cathodes connected in common. The diodes 49U, 49V, and 49W constitute a diode OR circuit 50. The cathode of the diode 49 is connected to the ground via the resistor 51 and is connected to the inverting input terminal of the comparator 53 via the resistor 52. The inverting input terminal is connected to the ground via a capacitor 54. The capacitor 54 and the resistor 52 constitute a CR filter. The comparator 53 corresponds to a comparison circuit.

  A series circuit of resistors 55 and 56 is connected between the 5V power source and the ground, and the common connection point thereof is connected to the non-inverting input terminal of the comparator 53. The potential at the common connection point applies a threshold voltage to the comparator 53, and is set to 3.3 V, for example. The non-inverting input terminal is connected to the ground through a capacitor 57. The output terminal of the comparator 53 is connected to the 5V power source via the resistor 58 and to the ground via the capacitor 59, and also connected to the emergency stop signal input terminal of the control circuit 45.

  The control circuit 45 generates a PWM command for driving the motor 24. Further, the control circuit 45 selects, for each carrier wave period of the PWM signal, a phase corresponding to at least two phases, for example, a long lower arm ON time, near the middle of the timing when the lower arm IGBT 41 is turned ON, and the terminal voltage thereof A / D conversion is performed to obtain the motor phase current. The control circuit 45 obtains the position of the rotor based on the output of a rotational position sensor (not shown) accompanying the rotation of the motor 24, and generates the three-phase complementary PWM signal. The control circuit 45 performs a vector control calculation so that the d-axis current and the q-axis current of the motor 24 have appropriate values, and drives and controls the motor 24.

  FIG. 3 shows the operation of each component such as the water supply valve, the motor 24, the drain valve, and the clutch mechanism in the entire process of the washing machine 10. In this figure, a thick line indicates a state in which each component operates. Further, the motor 24 is shown separately for normal rotation and reverse rotation. When the clutch mechanism operates as indicated by a thick line, the rotation of the motor 24 is transmitted to the rotating tank 14 via the clutch mechanism, and the rotating tank 14 also rotates.

  Next, the operation of this embodiment will be described. In the range where the phase current of the motor 24 shows a normal value, the voltage applied to the inverting input terminal of the comparator 53 via the diode OR circuit 50 does not exceed the threshold voltage. Therefore, the level of the emergency stop signal input terminal of the control circuit 45 is maintained high. For example, in the inverter circuit 40, when an overcurrent flows due to a short circuit between the upper and lower arms of any phase, the level of the emergency stop signal input terminal changes to low because the potential of the inverting input terminal exceeds the threshold voltage. . When the control circuit 45 recognizes the level change, it immediately stops outputting the PWM signal. Thereby, destruction of the circuit element or the like is prevented.

  As described above, according to the present embodiment, the inverter circuit 40 drives the motor 24 that generates the rotational driving force for performing the washing operation, and the control circuit 45 controls the inverter circuit 40. The shunt resistors 43U, 43V, and 43W detect currents that flow through the phase windings of the motor 24. The comparator 53 is used by the control circuit 45 to detect overcurrent, and the terminal voltage of the shunt resistor 43 is set to the threshold voltage. Compare with A diode OR circuit 50 is disposed between the shunt resistors 43U, 43V, 43W and the inverting input terminal of the comparator 43.

  With this configuration, since the overcurrent can be detected using the diode OR circuit 50 and the single comparator 53, the inverter device can be made compact without increasing the circuit area. Then, the number of parts can be reduced to reduce the cost, and the reliability of the apparatus can be increased.

  Further, the terminal voltage of the shunt resistors 43U, 43V, 43W is divided by the resistance voltage dividing circuit 48 and applied to the A / D input terminal of the control circuit 45. Thereby, the potential applied to the input terminal can be adjusted to be within the input voltage range of the A / D converter built in the control circuit 45. Then, when performing overcurrent detection using the diode OR circuit 50, it is possible to absorb an error caused by a voltage drop corresponding to the forward voltage of the diode 49.

(Second Embodiment)
Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, description thereof will be omitted, and different parts will be described. As shown in FIG. 4, the inverter device of the second embodiment is obtained by replacing the control circuit 45 with a control circuit 61. The control circuit 61 has a built-in comparator 62, which is used for overcurrent detection instead of the comparator 53. According to the second embodiment configured as described above, the number of parts to be used can be further reduced.

(Third embodiment)
As shown in FIG. 5, the inverter device of the third embodiment uses a control circuit 45 as in the first embodiment. A power element module 71 including the inverter circuit 40 is used. The power element module 71 includes the inverter circuit 40 and a built-in driver unit 72 that outputs a gate signal to each IGBT 41. The built-in driver unit 72 includes a gate driver 73 that drives the gate of the IGBT 41 in accordance with a complementary PWM signal input from the control circuit 45, and a comparator 74 that is used to stop the gate signal output from the gate driver 73. Have.

  In the third embodiment, the output terminal of the diode OR circuit 50 is connected to the inverting input terminal of the comparator 74 in order to use the comparator 74 for overcurrent detection. The output terminal of the comparator 74 is connected to the emergency stop signal input terminal of the gate driver 73 in order to stop the gate signal output as described above. Therefore, the control circuit 45 does not need to perform the emergency stop process of the inverter circuit 40 as in the first embodiment. However, the output terminal of the comparator 74 is also connected to the overcurrent detection terminal of the control circuit 45 in order to execute other processes such as abnormality notification associated with the overcurrent detection.

  As described above, according to the third embodiment, the power element module 71 formed by integrating the inverter circuit 40, the driver 73 that drives the gate of the IGBT 41 that constitutes the inverter circuit 40, and the comparator 73 that performs overcurrent detection. Is provided. Thereby, the number of parts used can be reduced similarly to 2nd Embodiment.

(Other embodiments)
The inverter circuit is not limited to a three-phase configuration, and may be applied to a single-phase H-bridge configuration.
What is necessary is just to change about each power supply voltage, resistance value, etc. according to individual design. The same applies to specific numerical values of frequencies.
The switching element is not limited to the IGBT 51, and may be a MOSFET, a power transistor, or the like.
You may apply to laundry machines, such as a drum type washing machine, a washing dryer, and a dryer.

  Although several embodiments of the present invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  In the drawing, 10 is a washing machine, 40 is an inverter circuit, 41 is an IGBT, 48 is a resistance voltage dividing circuit, 49 is a diode, 50 is a diode OR circuit, 53 is a comparator, 61 is a control circuit, 62 is a comparator, and 71 is power. An element module 74 represents a comparator.

Claims (4)

An inverter circuit for driving a motor that generates a rotational driving force for performing a washing operation;
A control circuit for controlling the inverter circuit;
A plurality of current detection resistors for detecting a current flowing in each phase winding of the motor;
The control circuit is used for overcurrent detection, and a comparison circuit that compares terminal voltages of the plurality of current detection resistors with a threshold voltage;
An inverter device for a washing machine comprising the plurality of current detection resistors and a diode OR circuit disposed between the input terminals of the comparison circuit. The control circuit includes an A / D converter,
The inverter device for a washing machine according to claim 1, further comprising a resistance voltage dividing circuit that divides the terminal voltages of the plurality of current detection resistors and inputs the divided voltage to the A / D converter.   The inverter device for a washing machine according to claim 1 or 2, wherein the comparison circuit is built in the control circuit.   The inverter device for a washing machine according to claim 1 or 2, further comprising a power element module formed by integrating the inverter circuit, a driver for driving a plurality of switching elements constituting the inverter circuit, and the comparison circuit.

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