JPH05196286A - Electromagnetic noise suppression device for air conditioner - Google Patents

Abstract

PURPOSE:To restrict noise generated in a communication line between an indoor device and an outdoor device by a method wherein a capacitor is connected between a circuit ground of an electronic control device for the indoor device and a chassis earth of a main body of the indoor device. CONSTITUTION:A capacitor 27 is connected between a circuit ground of an electronic control circuit 7 of an indoor device 4 and a chassis earth line 28 of a main body of the indoor device. Noise of high frequency component generated at a switching power supply 9 is shielded by a noise filter 10 against a power supply cord 1. However, noise coming into a communication line 3 due to dropping onto the circuit ground with the capacitor of the noise filter 10 drops onto the chassis earth line 28 through the capacitor 27 added to it, resulting in that noise in a short wave band of about 5MHz is restricted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter type air conditioner equipped with an electronic control device indoors and outdoors.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIGS. In FIG. 6, power is supplied from the power cord 1 to the indoor unit 4, and the outdoor unit 5 is connected to the power line 2 and the communication line 3 from the indoor unit 4. Further, the chassis ground wire 6 is connected from the main body of the outdoor unit 5 in terms of the electrical appliance control law and safety.

In FIG. 5, the power supplied from the power cord 1 is supplied to the electronic control unit 7 of the indoor unit 4, and a switching power supply 9 for driving a fan motor 12 is provided in the electronic control unit 7 of the indoor unit 4. A noise filter 10 for cutting noise of the switching power supply 9 and a microcomputer 11 are provided. Switching power supply 9 for indoor unit 4
Oscillates at 50 to 70 KHz, and noise of its harmonic component is suppressed by the noise filter 10. Indoor unit 4
The microcomputer 11 of the electronic control unit 7 and the microcomputer 18 of the electronic control unit 8 of the outdoor unit 5 are
The communication line 3 is connected via the transmission transistors 13 and 19.

The power supplied to the outdoor unit 5 through the power supply line 2 is double-voltage rectified by the diode bridge 23, the capacitors 16 and 17 through the noise filter 14 and the reactor 15, and converted into a DC voltage. 8 and the power transistor 21. A PWM signal having a carrier frequency of 3 KHz is supplied from the microcomputer 18 to the power transistor 21, and the compressor 22
Works. The outdoor fan motor 20 also operates according to the operation. The noise filter 14 has a carrier frequency of 3 KH
The PWM signal of z turns on / off the power transistor 21.
It suppresses the harmonic noise that occurs when F is reached.

FIG. 11 is a characteristic diagram of the noise level measured by using a high impedance probe between the communication line 3 and the chassis ground line 6. In FIG. 11, 0.5KH
Noise peaks are seen in the AM band of the low frequency radio of z and the short wave band of the radio near 5 MHz. This is the noise filter 10, the circuit ground lines 24, 25, 26 of the microcomputers 11, 18, and the transmission transistor 13,
This is because one end of 19 is connected to the circuit ground.

[0006]

In the current inverter type air conditioner, the noise of the switching power supply 1 mounted on the indoor unit 4 travels on the communication line 3 of the indoor unit 4 and the outdoor unit 5 and is input to the radio as noise. However, the regulations have been tightened under the Electrical Appliance and Material Control Law.

The present invention solves the above problems, and an object of the present invention is to provide an electromagnetic noise suppression device for an air conditioner, which suppresses noise generated from a communication line between an indoor unit and an outdoor unit to reduce radio noise. Is to

[0008]

In order to solve the above problems, the electromagnetic noise suppressing device of the present invention comprises a capacitor connected between the circuit ground of the electronic control unit of the indoor unit and the chassis ground of the indoor unit body. is there. Further, the electromagnetic noise suppressing device of the present invention is one in which a noise filter section is provided on the indoor unit side between the communication lines of the indoor unit and the outdoor unit, and further, the circuit ground of the electronic control device of the outdoor unit and the outdoor unit. A capacitor is connected between the chassis ground of the main body.

[0009]

With the above structure, the switching power supply noise of the indoor unit flows from the capacitor of the noise filter and the circuit ground to the capacitor added to the indoor unit side and to the chassis ground, so that the noise on the communication line is reduced.

Further, in this case, although leakage current flowing to the chassis ground through the capacitor of the noise filter and the capacitor added from the circuit ground increases and a safety problem remains, the indoor unit side is located between the communication line of the indoor unit and the outdoor unit. The noise filter section provided in the unit cuts off the noise of the switching power supply of the indoor unit, reduces the noise riding on the communication line, and does not increase the leakage current.

Further, since the inverter noise of the outdoor unit flows to the capacitor added to the outdoor unit side to the chassis ground, the noise riding on the communication line is further reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is an electric circuit diagram of an electromagnetic noise suppression device for an air conditioner according to a first embodiment of the present invention. In FIG. 1, those having the same functions as those of FIG. 5 of the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, reference numeral 27 is a capacitor connected between the circuit ground of the electronic control unit 7 of the outdoor unit 4 and the chassis ground wire 28 of the indoor unit body. Now, the noise of the harmonic component generated in the switching power supply 9 is cut off from the power cord 1 by the noise filter 10, but the noise of the capacitor of the noise filter 10 causes it to fall on the circuit ground, so that it is carried on the communication line 3. The incoming noise will be dropped to the chassis ground wire 28 through this added capacitor 27, and as shown in FIG.
Radio short-wave noise near MHz is suppressed. Here, 74 dB is a standard under the Electrical Appliance and Material Control Law, and is a regulation value when the distance between the communication line 3 and the chassis ground 6 is measured by a high impedance probe.

FIG. 2 is an electric circuit diagram of an electromagnetic noise suppressor for an air conditioner according to a second embodiment of the present invention. In FIG. 2, those having the same functions as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 2, reference numeral 29 designates a two-wire communication line 3 for communication between the microcomputer 11 of the electronic control unit 7 of the indoor unit 4 and the microcomputer 18 of the electronic control unit 8 of the outdoor unit 5 in the room. It is a noise filter section connected between the machine side and the chassis ground wire 28 of the indoor unit body. Now, the noise of the harmonic component generated in the switching power supply unit 9 flows to the circuit ground through the capacitor of the noise filter 10, and the transistor 13 that sends a signal from the microcomputer 11 of the indoor unit 4 to the microcomputer 12 of the outdoor unit 8 and the like. Although it tries to get on the communication line 3 via the, it does not get on the communication line 3 because it falls on the chassis ground line 28 due to the noise filter portion 29. Therefore, when measuring the noise between the communication line 3 and the chassis ground line 6 with a high impedance probe,
As shown in FIG. 8, the noise level in the radio short-wave band around 5 MHz decreases.

Moreover, in the first embodiment, the leakage current is generated from the capacitor of the noise filter 10 and the circuit ground through the capacitor 27 to the chassis ground line 28, but in the present embodiment, such leakage current increases. Nor.

FIG. 3 is an electric circuit diagram of an electromagnetic noise suppressing device for an air conditioner according to a third embodiment of the present invention. In FIG. 3, components having the same functions as those in FIGS. 1 and 2 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 3, reference numeral 27 denotes a condenser added to the indoor unit side similar to FIG. Reference numeral 30 is a capacitor connected between the circuit ground of the electronic control unit 18 of the outdoor unit 5 and the chassis ground wire 6 of the outdoor unit main body. From the microcomputer 11 of the electronic control unit 7 of the indoor unit 4 to the microcomputer 18 of the electronic control unit 8 of the outdoor unit 5
The communication line 3 is tangentially connected to each other, and a signal from the indoor unit 4 communicates with the transistor 13 and a signal from the outdoor unit 5 communicates with the transistor 19. Outdoor unit 5
Is supplied to the electronic control unit 8 and the power transistor 21, and further to the microcomputer 18
A PWM signal having a carrier frequency of 3 KHz is supplied to the power transistor 21. The noise filter 14 suppresses harmonic noise generated when the PWM signal having the carrier frequency of 3 KHz turns the power transistor 21 ON / OFF.

Here, the added capacitor 30 induces into the circuit of the electronic control unit 18 of the outdoor unit 8 due to the harmonic noise and the inverter noise generated from the power transistor 22, and the chassis ground through the added capacitor 30. Since it goes out to the line 6, it cannot come on the communication line 3. Therefore, as shown in FIG. 9, when noise between the communication line 3 and the chassis ground line 6 is measured using a high impedance probe, the low frequency range is 0.5.
The noise in the AM radio band around 5 MHz is also reduced, and the generated noise is reduced by the synergistic action with the capacitor 27 added on the indoor unit side.

FIG. 4 is an electric circuit diagram of an electromagnetic noise suppressing device for an air conditioner according to a fourth embodiment of the present invention. 4, those having the same functions as those in FIGS. 1, 2 and 3 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 4, noise generated by the switching power supply 9 of the indoor unit 4 is dropped to the chassis ground line 28 by the noise filter section 29, and the outdoor unit 5
The noise generated from the power transistor 21 of FIG.
The noise generated inside and outside over 0.5 to 30 MHz is cut from the communication line 3, and the noise level is reduced as shown in FIG. Further, as shown in FIG. 3, the leakage current does not increase by not dropping the indoor unit side to the chassis ground line 28 with the capacitor 27.

[0021]

As described above, according to the present invention, the switching power supply noise of the indoor unit flows from the capacitor of the noise filter and the circuit ground to the capacitor added to the indoor unit side to the chassis ground. There is less noise riding on. In addition, the noise of the switching power supply of the indoor unit is blocked by the noise filter section added to the communication line, the noise riding on the communication line is reduced, and it does not leak from the circuit ground to the additional capacitor as described above. The current does not increase.
Further, since the inverter noise of the outdoor unit flows to the capacitor added to the outdoor unit side to the chassis ground, the noise riding on the communication line is further reduced.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an electromagnetic noise suppression device for an air conditioner according to a first embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing an electromagnetic noise suppression device for an air conditioner according to a second embodiment of the present invention.

FIG. 3 is an electric circuit diagram showing an electromagnetic noise suppression device for an air conditioner according to a third embodiment of the present invention.

FIG. 4 is an electric circuit diagram showing an electromagnetic noise suppression device for an air conditioner according to a fourth embodiment of the present invention.

FIG. 5 is an electric circuit diagram showing a conventional electromagnetic noise suppression device for an air conditioner.

FIG. 6 is a configuration diagram of an air conditioner body.

FIG. 7 is a characteristic diagram of a noise level in the first embodiment of the present invention.

FIG. 8 is a characteristic diagram of a noise level in the second embodiment of the present invention.

FIG. 9 is a noise level characteristic diagram in the third embodiment of the present invention.

FIG. 10 is a noise level characteristic diagram in the fourth embodiment of the present invention.

FIG. 11 is a characteristic diagram of noise level in a conventional example.

[Explanation of symbols]

 2 power line 3 communication line 4 indoor unit 5 outdoor unit 6 chassis ground wire of outdoor unit 7 electronic control unit for indoor unit 8 electronic control unit for outdoor unit 9 switching power supply 10 noise filter for indoor unit 11 micro for indoor unit Computer 14 Noise filter on the outdoor unit side 18 Microcomputer on the outdoor unit side 27 Condenser added on the indoor unit side 28 Chassis ground wire of the indoor unit body 29 Noise filter section added to the communication line 30 Added on the outdoor unit side Capacitor

Claims (3)

[Claims] 1. In an inverter type air conditioner in which an electronic control device is mounted in each of an indoor unit and an outdoor unit, a capacitor is provided between a circuit ground of the electronic control device of the indoor unit and a chassis ground of the indoor unit main body. The electromagnetic noise suppression device for the air conditioner connected via. 2. In an inverter type air conditioner in which an electronic control device is installed in each of an indoor unit and an outdoor unit, communication between the microcomputer of the electronic control device of the indoor unit and the microcomputer of the electronic control device of the outdoor unit. Do 2
An electromagnetic noise suppression device for an air conditioner, in which a noise filter section is provided on the indoor unit side between the lines. 3. The electromagnetic noise suppressor for an air conditioner according to claim 1, wherein the circuit ground of the electronic control unit of the outdoor unit and the chassis ground of the main unit of the outdoor unit are connected via a capacitor.