JP3296335B2 - Air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner using a scroll compressor for refrigerant compression and having at least one of cooling and heating functions, and more particularly to an IGBT inverter for controlling an electric motor for driving a scroll compressor. To an air conditioner using the same.

[0002]

2. Description of the Related Art In an air conditioner provided 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 in accordance with the required capacity of the air conditioner. Of the compressor changes, and the capacity of the compressor is controlled. The inverter converts a DC obtained by rectifying and smoothing the AC power supply into an AC having an operation frequency by a power switching element that opens and closes at a frequency corresponding to the operation frequency, and outputs the AC to an electric motor. In order to increase the operating frequency under the condition that the same torque is achieved, and to increase the rotation speed of the motor correspondingly, it is necessary to increase the output voltage of the inverter according to the increase in the operating frequency. Therefore, in general, the output AC voltage is chopped at a frequency higher than the operation frequency, and the on-duty ratio, that is, the temporal average output voltage is increased as the operation frequency increases. An inverter is 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, set the carrier frequency to 20 kHz to remove the audible sound band.
z or more. It should be noted that a related device of this type is, for example, a device described in JP-A-62-178832.

[0004]

In the above prior art, the carrier frequency of an inverter for driving an electric motor is 1 to 2 kHz.
Therefore, electromagnetic noise in the audible range caused by the carrier frequency was generated from the electric motor. In particular, when the compressor of the air conditioner is operated at a low frequency, there is a problem that the electromagnetic noise is directly radiated as noise to the surroundings, thereby impairing comfort. On the other hand, when the carrier frequency of the inverter is increased, noise is certainly reduced, but high-speed switching is realized.

[0005] The present invention has been made in order to improve the conventional disadvantages, and has as its object to reduce harsh noise and enable comfortable operation of an air conditioner. Another object of the present invention is to provide a high-performance air conditioner in which loss during high-frequency operation of a compressor is reduced. Still another object of the present invention is to provide an air conditioner equipped with a small and inexpensive inverter.

[0006]

In order to achieve the above-mentioned object, the present invention relates to a refrigeration cycle in which a compressor driven by an electric motor is connected to an outdoor heat exchanger and an indoor heat exchanger by piping, and a refrigerant circulates. In an air conditioner having a control operation device that commands the operating frequency of the compressor using the operating state of the indoor side and the outdoor side, an orbiting scroll driven through a fixed scroll and a crankshaft connected to the electric motor, Wherein the compressed refrigerant is discharged from the compressor through a discharge port formed at the center of the fixed scroll to the outside of the compressor via the electric motor, and the compression of which is volume-controlled at the operating frequency. A sealed container made of steel or cast iron formed so as to cover the body of the electric motor and the compressor with a body side plate, a top cover with a head cover, and a bottom cover with a lower cover, and 4 kHz. Determine the following constant carrier frequency above 10 kHz, the at higher the operating frequency of the compressor exceeds the reference value reduces the determined the carrier frequency stages, compressor or noise detection hand near the
Provide a step, and when the noise level exceeds the allowable value,
Increase the number and reduce the capacity of the inverter that drives the motor
Is what you do.

[0007] Thus, the operating frequency of the compressor is commanded using the indoor and outdoor operating states of the air conditioner, and the compressor is driven via the fixed scroll and the crankshaft connected to the electric motor. Since the scroll-type compressor has the orbiting scroll and can suppress the torque fluctuation to a small value, the noise caused by the torque fluctuation of the refrigeration cycle can be reduced. In addition, 4 kHz or more and 10 kHz or less
Determine a constant carrier frequency and determine the operating frequency of the compressor.
The carrier frequency determined at high places beyond the reference value
As the number decreases gradually, the compressor's high operating frequency range
Does not result in a high carrier frequency, preventing an increase in loss,
The motor is cooled by the refrigerant to reduce the capacity of the inverter.
Can be In addition, the motor and compressor
Cover the upper part with the head cover and the lower part with the lower cover.
Stored in a sealed container made of steel or cast iron
In conjunction with this, the noise is further reduced and the size of the device is reduced.
realizable.

As described above, both the reduction of noise and the reduction of inverter loss are satisfied, the power loss and noise of the air conditioner are reduced, and a wide range of capacity control can be achieved while reducing the size of the device.

[0009]

[0010]

[0011]

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

Further, a noise detecting means 21 for detecting noise is provided at or near the induction motor and the scroll compressor. As this noise detection means,
An ordinary sound level meter may be used, but for simplicity, any type of signal such as various acceleration sensors and AE sensors 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. As the detection means, there are an optical sensor, a capacitance type, an electromagnetic gap sensor, and the like.

The scroll compressor 5 has, for example, a structure shown in a sectional view of FIG. Induction motor 6 on rotating shaft
The orbiting scroll 14 is attached to the opposite end of the 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 the gas is then sucked into the fixed scroll 14 having a spiral wrap and the orbiting scroll. 15, the orbiting scroll 15 is driven through a crankshaft connected to the induction motor 6 to move toward the center of the spiral wrap of the scroll and is gradually compressed. The compression space is minimum at the center, the gas is compressed at the maximum at the center, and the discharge port 1 formed at the center of the fixed scroll 14 is formed.
It is discharged from 4 'to the upper discharge chamber, and then discharged from the discharge pipe 17 to the outside through the motor chamber. In this way, the suction, compression, and discharge of the refrigerant gas are continuously repeated, and the discharged refrigerant circulates in the refrigeration cycle to perform cooling or heating.

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

The inverter 8 for controlling the induction motor 6 includes:
As shown in FIG. 3, a rectifying element 9 for converting an alternating current from the power supply 7 to a direct current, a smoothing capacitor 10, a switching element 11 for converting a direct current to an alternating current of a desired frequency, and a current flowing to the induction motor 6 are detected. A current sensor 12 and a control device 13 for taking in 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 indoor operation state of the air conditioner of FIG.
For example, using the outdoor heat exchanger temperature or the like, the operation state of the compressor is calculated in the control operation device of the air conditioner provided on the outdoor side, and the value is transmitted to the control device 13 as an operation frequency command. Upon receiving this operation command, the control device 13 switches the switching element 11. As a result, an AC having a desired operation frequency according to the operation command is generated and supplied to the induction motor 6 to rotate the induction motor 6. In this embodiment, an IGBT is used for the switching element 11. 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 is, the higher the number of revolutions is, and the capacity of the scroll compressor 5 can be controlled.

FIG. 4 shows an outline of pulse width modulation. When the capacity of the scroll compressor 5 is indicated, the inverter determines the carrier frequency. Here, the carrier frequency is constant, for example, 5 kHz irrespective of the operating frequency of the compressor (FIG. 7A). When 50 Hz is specified as the capacity of the compressor, that is, 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 equal division timing (0.2 msec) is calculated, and the application time to the switching element in each section is calculated from the calculation result. A determined application signal is applied (FIG. 2B). As a result, a 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 a pulse width modulation, the carrier frequency has been controlled so as to be 10 kHz or more so that an electromagnetic sound of an audible frequency is not generated from the motor 6.
In this embodiment, an IGBT is used as a switching element, and the carrier frequency is set to a relatively low frequency of 10 kHz or less. FIG. 5 shows the results of noise measurement when the carrier frequency was set in the audible range and the motor was 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 this 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 is equal to the carrier frequency and its integral multiple. Set not to
Electromagnetic noise having 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
The noise is significantly reduced as compared with the case of. This reduction in noise is remarkable especially in a low speed range. Therefore, it is preferable to increase the carrier frequency where the operating frequency of the compressor is low. Further, according to experiments by the present inventors, when the carrier frequency is decreased steadily, harsh sounds gradually increase. This is particularly remarkable below 4 kHz, and becomes almost unnoticeable above 5 kHz.

Next, FIG. 7 shows the result of experimentally determining the loss of the inverter when the carrier frequency is changed in the present embodiment having the above configuration. The loss of the IGBT which is a switching element of the inverter unit is normalized by a value of a carrier frequency of 10 kHz. As can be seen from FIG. 7, the loss of the IGBT decreases as the carrier frequency decreases. When comparing the case where the carrier frequency is 10 kHz and the case where the carrier frequency is 5 kHz, the loss of the IGBT is reduced by 18% in this example when the carrier frequency is 5 kHz. Thus, if the operation is performed with a lower carrier frequency, there are many advantages in terms of efficiency. On the other hand, since the noise increases as the carrier frequency is lower, it is desirable to operate in combination with the actual operation. That is, the operation is performed with the carrier frequency lowered as much as possible, and when the noise level exceeds the allowable value, the carrier frequency is increased. Thus, 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 for detecting the noise level.

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

As described above, since the scroll type compressor and the electric motor whose capacity can be controlled are housed in a closed container and the carrier frequency of the inverter is set to 4 kHz to 10 kHz, noise reduction and inverter loss reduction are achieved. And an air conditioner that satisfies both. Further, since the carrier frequency can be reduced and the size of the device can be reduced, the heat generated from the IGBT can be reduced and the cooling system can be simplified. In addition, it is possible to increase inverter and motor efficiency,
The operating range of the compressor can be expanded, and a wide range of capacity control can be realized.

[0022]

According to the present invention, both the reduction of noise and the reduction of inverter loss are satisfied, the power loss and noise of the air conditioner are reduced, and the size of the apparatus can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional view of one 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 a motor single-unit noise level when a carrier frequency of an inverter is changed.

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

FIG. 7 is a diagram showing a change in loss in an IGBT depending on 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 ... Heat exchanger for indoor units, 2 ... Heat exchanger for outdoor units, 3 ... Refrigerant piping, 4 ... Four-way valve, 5 ... Scroll compressor, 6 ... Induction motor, 7 ... Power supply, 8 ... Inverter, 9 ... Rectifier element, 10 ... Smoothing capacitor, 11 ... Switching element,
12: current sensor, 13: control device for driving the switching element, 14: fixed scroll, 14 ': discharge port at the center of the fixed scroll, 15: orbiting scroll, 16: suction port, 17: discharge port, 21: noise detection means , 22... Rotation speed detecting means.

Claims (1)

(57) [Claims] 1. An air conditioner having a refrigeration cycle in which a compressor driven by an electric motor is connected to an outdoor heat exchanger and an indoor heat exchanger by pipes to circulate a refrigerant. A scroll type compressor having a control operation device for instructing the operating frequency of the compressor by using a fixed scroll and an orbiting scroll driven via a crankshaft connected to the electric motor, wherein the compressed refrigerant is The compressor, which is discharged from the compressor through the motor through a discharge port formed at the center of the fixed scroll and whose volume is controlled by the operating frequency, the body of the motor and the compressor being a body A steel or cast iron sealed container formed to cover the side plate, top cover with the top cover and bottom cover with the lower cover, and a fixed carrier frequency of 4 kHz or more and 10 kHz or less are determined. When the operating frequency of the compressor exceeds a reference value, the determined carrier frequency is reduced stepwise, and noise detecting means is provided at or near the compressor.
If the noise level exceeds the allowable value, the carrier frequency
And reduce the capacity of the inverter that drives the motor.
Air conditioner, characterized in that Kusuru.