JPH0835711A - Air conditioner with inverter and controlling method therefor - Google Patents

Abstract

PURPOSE:To reduce the noise due to an induction motor with an inverter and to realize the operation of a high efficiency in an air conditioner. CONSTITUTION:The compressor of an air conditioner and the induction motor for driving a compressor are sealed in a chamber. An IGBT is used for the switching element of an inverter 8 for controlling the number of revolutions of the motor, and the inverter is so that its carrier frequency becomes low of 4kHz to 10kHZ.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner with an inverter having a function of at least one of heating and cooling, which uses a scroll type compressor for refrigerant compression, and a control method thereof, and particularly drives a scroll type compressor. The present invention relates to an air conditioner with an inverter that uses an IGBT inverter for controlling an electric motor and a control method thereof.

[0002]

2. Description of the Related Art In an air conditioner equipped with a refrigerant compressor having a variable operating frequency driven by an electric motor controlled by an inverter, the operating frequency of the inverter is changed according to the required capacity of the air conditioner. The rotational speed of the compressor changes and the capacity of the compressor is controlled. The inverter converts direct current obtained by rectifying and smoothing an alternating current power source into alternating current of operating frequency by an electric power switching element that opens and closes at a frequency corresponding to the operating frequency, and outputs it to the electric motor. In order to increase the operating frequency under the condition that the same torque is achieved and correspondingly increase the rotation speed of the electric motor, it is necessary to increase the output voltage of the inverter as the operating frequency increases. Therefore, in general, the voltage-type PWM system is configured such that the output AC voltage is chopped at a frequency higher than the operating frequency, and its on-duty ratio, that is, the temporal average output voltage is increased as the operating frequency increases. Inverters are often used.

Conventionally, in an air conditioner using such a voltage-type PWM inverter, the operating frequency of the inverter that drives the compressor is 30 Hz to 115 Hz, and the carrier frequency of the inverter is 1 kHz to 2 kHz. Alternatively, the carrier frequency is 20 kHz to remove the audible sound band.
It was above z. As a device related to this type, for example, a device described in JP-A-62-178832 can be cited.

[0004]

In the above-mentioned prior art, the carrier frequency of the inverter driving the electric motor is 1 to 2 kHz.
Since it is low, the electromagnetic noise was generated from the electric motor in the audible range due to this carrier frequency. Then, especially when the compressor of the air conditioner is operated at a low frequency, there is a problem that this electromagnetic sound is directly emitted as noise and is radiated to the surroundings, which impairs comfort. On the other hand, when the carrier frequency of the inverter is increased, noise is surely reduced, but there is a problem that the device becomes large or expensive in order to realize high-speed switching.

The present invention has been made in order to improve such conventional problems, and an object thereof is to reduce annoying noise and enable comfortable operation of an air conditioner. Another object of the present invention is to provide a high performance air conditioner with reduced loss during high frequency operation of the compressor. A further object of the present invention is to provide an air conditioner equipped with a small and inexpensive inverter. ◆ Again
An object of the present invention is to provide an air conditioner that can change the carrier frequency of an inverter according to the noise generated from the air conditioner and a control method thereof.

[0006]

In order to achieve the above object, there is provided a scroll type compressor driven by an induction motor and having a capacity controllable, and an air with an inverter for controlling the rotation speed of the induction motor by a voltage type PWM inverter. In the harmony machine, the induction motor and the scroll compressor are hermetically sealed by a hermetic chamber, and the carrier frequency of the inverter is set to 4 kHz or more and 10 kHz or less.

Preferably, an IGBT is used as the switching element of the inverter. ◆ Again
Preferably, the natural frequency (resonance frequency) of the closed chamber is set to a frequency different from the carrier frequency of the inverter and its integral multiple. Further preferably, a rectifying element for converting alternating current to direct current in the inverter, a switching element for converting direct current to alternating current, a current detecting means for detecting a current flowing through the induction motor, and a control device for driving the switching element. And the carrier frequency of the switching element is set to a low frequency so that the photocoupler provided in the control device is of a low speed type.

Preferably, the air conditioner is provided with noise detecting means for detecting noise of the air conditioner, and when the noise value detected by the noise detecting means exceeds a reference value, the carrier frequency of the inverter is increased. The inverter is provided with control means for controlling so as to raise.
Further, preferably, the inverter is provided with means for lowering the carrier frequency of the inverter when the operating frequency of the scroll compressor exceeds a reference value.

Further, the present invention is an air conditioner with an inverter in which a refrigeration cycle is formed by sequentially connecting a scroll compressor, a four-way valve, an outdoor heat exchanger, an expansion means, and an indoor heat exchanger by piping. The inverter that controls the rotation speed of the induction motor that drives the scroll compressor includes a rectifying unit that converts AC into DC, a switching element that converts DC into AC, and a carrier frequency of the switching element is 4 kHz. The frequency is set to 10 kHz or less.

Furthermore, the present invention is a control method for an air conditioner with an inverter, in which a scroll compressor, a four-way valve, an outdoor heat exchanger, an expansion means, and an indoor heat exchanger are sequentially connected by piping. The carrier frequency of the switching element provided in the inverter that controls the rotation speed of the induction motor that drives the scroll compressor is set to 4 kHz or more and 10 kHz or less. And, preferably, when the operating frequency of the scroll compressor is higher than a reference value, the carrier frequency of the switching element is lowered.

Preferably, the carrier frequency is
When the operating frequency of the scroll compressor exceeds a reference value, it is gradually reduced. Still further, the present invention is a control method for an air conditioner with an inverter, in which a scroll compressor, a four-way valve, an outdoor heat exchanger, an expansion means, and an indoor heat exchanger are sequentially connected by piping. The carrier frequency of the switching element installed in the inverter that controls the rotation speed of the induction motor that drives the scroll compressor is 4 kHz.
The frequency is set to z or more and 10 kHz or less, and the carrier frequency of the inverter is lowered when the output of the noise detecting means provided in the air conditioner exceeds a reference value.

[0012]

A scroll type compressor is used as the compressor for compressing the refrigerant of the air conditioner. As a result, the torque fluctuation can be suppressed to a small level, and the noise caused by the torque fluctuation can be reduced. Next, a voltage-type PWM inverter with a variable operating frequency is used to control the induction motor that drives this scroll compressor, and an IGBT (Insulated Gamut) is used as its switching element.
te Bipolar Transistor). Further, the carrier frequency of this inverter is controlled to 4 kHz to 10 kHz.
As a result, it is possible to reduce an offensive electromagnetic noise generated from the electric motor and reduce the loss of the IGBT. The carrier frequency is more preferably 5 kHz.
It is good to set it to ~ 7kHz. If the carrier frequency is selected within this range, an inverter-controlled compressor that is less expensive and less affected by low frequencies can be obtained. ◆ Also, if the carrier frequency is changed according to the amount of noise generated by the air conditioner, the noise caused by driving the compressor can be reduced and a comfortable air conditioning environment can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In Fig. 1, the refrigeration cycle includes an indoor unit heat exchanger 1, an outdoor unit heat exchanger 2, and an expansion means 20 provided between the indoor unit heat exchanger 1 and the outdoor unit heat exchanger 2. ,
A four-way valve 4 that changes the flow direction of the refrigerant in the refrigeration cycle by cooling and heating, an induction motor 6 inside, and a scroll compressor 5 that has a mechanism for sucking, compressing, and discharging the refrigerant by rotation of the induction motor 6, And a refrigeration cycle pipe 3 for sequentially connecting these. The induction motor 6 in the scroll compressor 5 has the induction motor 6
An inverter 8 for controlling the number of revolutions is further connected to a supply power source 8 respectively.

Further, noise detecting means 21 for detecting noise is provided at or near the induction motor and the scroll compressor. As this noise detection means,
A normal sound level meter may be used, but for the sake of simplicity, various acceleration sensors, AE sensors and the like that can obtain signals related to noise and vibration may be used. Further, the induction motor 6 or the scroll compressor 5 is provided with a rotation speed detecting means 22. Examples of this detecting means include an optical sensor, a capacitance type sensor, an electromagnetic gap sensor, and the like.

The scroll compressor 5 has, for example, a structure shown in the sectional view of FIG. Induction motor 6 on the rotating shaft
Of the electric motor rotor, and the orbiting scroll 14 is attached to the opposite end of the electric motor rotor. When the induction motor 6 rotates, low-pressure gas is sucked from the suction port 16 formed on the outer diameter side of the fixed scroll 14 in the scroll compressor 5, and this gas is then fed to the fixed scroll 14 having a spiral wrap and the orbiting scroll. 15 is enclosed in a compression space formed by 15 and is driven toward the center of the spiral wrap of the scroll by the orbiting motion of the orbiting scroll 15 driven via a crankshaft connected to the induction motor 6, and is gradually compressed. The compression space is the smallest in the central part, the gas is compressed maximally in the central part, and the discharge port 1 formed in the central part of the fixed scroll 14
4'is discharged to the upper discharge chamber and then discharged from the discharge pipe 17 to the outside of the machine through the electric motor chamber. In this way, the refrigerant gas is continuously sucked, compressed, and discharged repeatedly, and the discharged refrigerant circulates in the refrigeration cycle to perform cooling or heating.

In the induction motor 6 and the scroll compressor 5, the body part is a body part side plate 24, the upper part is a head cover 25,
The bottom part is covered with each of the lower covers 25 to form a sealed container. Here, each of the covers is made of a material such as steel or cast iron that blocks noise.

The inverter 8 for controlling the induction motor 6 is
As shown in FIG. 3, a rectifying element 9 for converting an alternating current from the power supply 7 into a direct current, a smoothing capacitor 10, a switching element 11 for newly converting a direct current into an alternating current of a desired frequency, and a current flowing to the induction motor 6 are detected. The current sensor 12 and the control device 13 for fetching the current value detected by the current sensor 12 and driving the switching element 11 are provided. On the other hand, although not shown here, the operating condition on the indoor side of the air conditioner of FIG. 3, such as room temperature and the operating condition on the outdoor side,
For example, the temperature of the outdoor heat exchanger is used to calculate the operation state of the compressor in the control arithmetic unit of the air conditioner provided outside the room, and the value is transmitted to the control device 13 as an operation frequency command. In response to this operation command, the control device 13 switches the switching element 11. As a result, an alternating current having a desired operating frequency according to the operating command is generated, and this is supplied to the induction motor 6 to rotate the induction motor 6. An IGBT is used as the switching element 11 in this embodiment. Further, in the inverter control device 13, pulse width modulation is performed such that the higher the operating frequency is, the higher the output voltage to the induction motor 6 is. Therefore, the higher the operating frequency of the electric motor 6, the higher the rotation speed of the electric motor 6, and the capacity control of the scroll compressor 5 becomes possible.

An outline of pulse width modulation is shown in FIG. When the capacity of the scroll compressor 5 is designated, the inverter determines the carrier frequency. Here, the carrier frequency is constant regardless of the operating frequency of the compressor, for example, 5 kHz ((a) in the same figure). If the capacity of the compressor, that is, 50 Hz is specified as the operating frequency, 100 carrier signals are output during one cycle of the voltage. That is, one wavelength (20 msec) is equally divided into 100, the value of the sine wave at the timing (0.2 msec) of the equal division is calculated, and the application time to the switching element in each section is calculated from this calculation result. An applied signal for determination is given ((b) in the same figure). As a result, the voltage waveform as shown in FIG. In this example, the carrier signal is fixed, but the carrier signal may be changed together with the operating frequency as described later.

In such pulse width modulation, the carrier frequency has been set to 10 kHz or higher so far so that the electromagnetic noise of the audible frequency is not generated from the electric motor 6.
In this embodiment, an IGBT is used as the switching element and the carrier frequency is set to a relatively low frequency of 10 kHz or less. FIG. 5 shows the noise measurement result when the carrier frequency is set in the audible range and the electric motor is operated alone. As shown in this figure, when the carrier frequency is 10 kHz or less, the noise value increases as the operating frequency decreases. However, in the case of the present embodiment, the motor driven by the inverter is housed in an iron container as shown in FIG. 2, and the natural frequency of the scroll compressor matches the carrier frequency and an integral multiple thereof. Set it not to
The electromagnetic noise of the same frequency component as the carrier frequency generated from the motor is suppressed from leaking to the outside of the scroll compressor.

FIG. 6 shows the measurement results of noise when the scroll compressor is operated. Carrier frequency is 5-6kHz
Even when controlled at a relatively low frequency value,
The noise level is the same as when the carrier frequency is 10 kHz or higher. And the carrier frequency is 1-2kHz
Compared to the case, the noise is significantly reduced. This noise reduction is remarkable especially in the low speed range. Therefore, it is preferable to increase the carrier frequency at a place where the operating frequency of the compressor is low. Further, according to experiments by the present inventors, when the carrier frequency is lowered more and more, annoying sound gradually increases. This is particularly noticeable below 4 kHz, and becomes almost unnoticeable above 5 kHz.

Next, FIG. 7 shows a result of experimentally finding the loss of the inverter when the carrier frequency is changed in this embodiment having the above-mentioned structure. The loss of the IGBT, which is the switching element of the inverter unit, is shown normalized by the value of the carrier frequency of 10 kHz. As can be seen from FIG. 7, the loss of the IGBT decreases as the carrier frequency decreases. Then, comparing the case where the carrier frequency is 10 kHz and the case where the carrier frequency is 5 kHz, when the carrier frequency is 5 kHz, the loss of the IGBT is reduced by 18% in this example. As a result, operating at a lower carrier frequency has many advantages in terms of efficiency, but on the other hand, since noise increases as the carrier frequency becomes lower, it is desirable to combine these in actual operation. That is, the carrier frequency is lowered as much as possible for operation, and when the noise level exceeds the allowable value, the carrier frequency is increased. As a result, the capacity of the inverter can be reduced, and the size and cost can be reduced. Here, the output of the above-described sensor is used to detect the noise level.

FIG. 8 shows a modification of the above embodiment.
In this embodiment, the carrier frequency is reduced continuously or stepwise when the operating frequency is high.
By selecting the carrier frequency in this way, the IGBT
There is an effect that it is possible to prevent a high carrier frequency in a high operating frequency range in which the loss of is increased.

[0023]

As described above, the IGBT is used as the switching element of the inverter of the air conditioner, the scroll type compressor capable of controlling the capacity and the induction motor are housed in the closed container, and the carrier frequency of the inverter is 4 kHz. Above 1
Since the frequency is set to 0 kHz or less, it is possible to realize an air conditioner that satisfies both the noise reduction and the inverter loss reduction. Further, since the carrier frequency is lowered, the device can be downsized and the cost can be reduced. Further, since the loss of the IGBT can be reduced, the heat generation from the IGBT can be reduced and the cooling system can be simplified. Further, the efficiency of the inverter and the motor can be increased, the operating range of the compressor can be widened, and a wide range of capacity control can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a refrigeration cycle of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of an embodiment of a scroll compressor used in the present invention.

FIG. 3 is a configuration block diagram of an inverter used in the air conditioner.

FIG. 4 is a diagram illustrating pulse width modulation.

FIG. 5 is a diagram showing a change in noise level of a motor when the carrier frequency of the inverter is changed.

FIG. 6 is a diagram showing a change in noise level at each operating frequency of the compressor of the air conditioner depending on the carrier frequency.

FIG. 7 is a diagram showing a change in loss of an IGBT according to a carrier frequency.

FIG. 8 is a diagram showing control of a carrier frequency according to a modification of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Indoor unit heat exchanger, 2 ... Outdoor unit heat exchanger, 3 ... Refrigerant piping, 4 ... Four-way valve, 5 ... Scroll type compressor, 6 ... Induction motor, 7 ... Supply power supply, 8 ... Inverter, 9 ... rectifying element, 10 ... smoothing capacitor, 11 ... switching element,
12 ... Current sensor, 13 ... Switching element drive control device, 14 ... Fixed scroll, 14 '... Discharge port at the center of the fixed scroll, 15 ... Orbiting scroll, 16 ... Suction port, 17 ... Discharge port. 21 ... Noise detecting means, 22 ... Rotation speed detecting means.

Claims (11)

[Claims] 1. A scroll type compressor having a capacity controllable drive by an induction motor, wherein the induction motor is a voltage source PW.
An air conditioner with an inverter that controls the rotation speed by an M inverter, wherein the induction motor and the scroll compressor are hermetically sealed by a hermetic chamber, and the carrier frequency of the inverter is 4 kHz or more and 10 kHz or less. Air conditioner. 2. An IG is used as a switching element of the inverter.
The air conditioner with an inverter according to claim 1, wherein BT is used. 3. The air conditioner with an inverter according to claim 1, wherein the natural frequency of the closed chamber is a frequency different from an integral multiple of the carrier frequency of the inverter. 4. The inverter comprises a rectifying element for converting alternating current to direct current, and a switching element for converting direct current to alternating current.
3. The inverter according to claim 1, further comprising a current detection unit that detects a current flowing through the induction motor and a control device that drives a switching element, and the control device includes a low-speed photocoupler. With air conditioner. 5. The air conditioner is provided with noise detecting means for detecting noise of the air conditioner, and when the noise value detected by the noise detecting means is larger than a reference value, control for increasing the carrier frequency of the inverter is performed. The air conditioner with an inverter according to claim 1 or 2, wherein means is provided in the inverter. 6. The inverter according to claim 1, wherein the inverter is provided with means for lowering the carrier frequency of the inverter when the operating frequency of the scroll compressor exceeds a reference value. With air conditioner. 7. An air conditioner with an inverter, wherein a scroll type compressor, a four-way valve, an outdoor heat exchanger, an expansion means, and an indoor heat exchanger are sequentially connected by piping to form a refrigeration cycle. An inverter that controls the rotation speed of an induction motor that drives the scroll compressor includes a rectifying unit that converts AC into DC, a switching element that converts DC into AC, and a carrier frequency of the switching element is 4 kHz or more and 10 kHz or less. An air conditioner with an inverter that is characterized by 8. A control method for an air conditioner with an inverter, in which a scroll compressor, a four-way valve, an outdoor heat exchanger, an expansion means, and an indoor heat exchanger are sequentially connected by piping. A method for controlling an air conditioner with an inverter, characterized in that a carrier frequency of a switching element provided in an inverter that controls a rotation speed of an induction motor that drives a compressor is set to 4 kHz or more and 10 kHz or less. 9. The method of controlling an air conditioner with an inverter according to claim 8, wherein the carrier frequency of the switching element is lowered when the operating frequency of the scroll compressor is higher than a reference value. 10. The method of controlling an air conditioner with an inverter according to claim 9, wherein the carrier frequency is gradually reduced when the operating frequency of the scroll compressor exceeds a reference value. 11. A control method for an air conditioner with an inverter, in which a scroll compressor, a four-way valve, an outdoor heat exchanger, an expansion means, and an indoor heat exchanger are sequentially connected by piping.
The carrier frequency of the switching element provided in the inverter that controls the rotation speed of the induction motor that drives the scroll compressor is set to 4 kHz or more and 10 kHz or less, and the output of the noise detection means provided in the air conditioner exceeds the reference value. A method for controlling an air conditioner with an inverter, characterized in that the carrier frequency of the cod is reduced.