JP3149768B2 - 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 having an inverter for driving a compressor.

[0002]

2. Description of the Related Art Conventionally, as an air conditioner, an outdoor unit,
Some include a compressor and an inverter that drives the compressor. The outdoor unit of this air conditioner is shown in FIGS. 6 (a) and 6 (b).
As shown in (1), a board 22 having the inverter circuit and the like and a radiating fin 23 to which a power transistor 24, a rectifier diode 25 and a radiating fin thermistor 26 are fixed are attached to an electrical component box 21. Then, according to the rise in the outside air temperature, the input current of the inverter is droop-controlled so that the temperature of the power transistor 24 does not exceed the temperature limit, thereby suppressing the temperature rise of the power transistor 24. Further, the air conditioner cannot protect the power transistor against a failure of the outdoor fan or the like only by the drooping control of the input current of the inverter, so that the temperature of the radiation fin 23 detected by the radiation fin thermistor 26 (power Based on the temperature of the transistor 24)
When the temperature of the power transistor 24 becomes higher than a predetermined temperature, the operation of the compressor is stopped to protect the power transistor 24.

[0003]

However, in the air conditioner described above, since the thermistor 26 for radiating fins is used to protect the power transistor 24, there is a problem that the cost of parts and the cost of mounting the parts increase.

Therefore, an object of the present invention is to protect a switching element without using a temperature sensor for detecting the temperature of a switching element of an inverter, such as a power transistor, even if an outdoor fan fails, thereby reducing costs. An object of the present invention is to provide an air conditioner.

[0005]

In order to achieve the above object, the air conditioner according to claim 1 has a higher operating frequency.
An inverter that drives a compressor with high pressure and a control signal is output to the inverter to respond to the rise in outside air temperature.
In order to prevent the temperature of the switching element of the inverter from exceeding the temperature limit when the high pressure of the compressor becomes high , the input current of the inverter is changed stepwise according to the rise of the outside air temperature to decrease the droop. Inverter control means for performing control; output overcurrent detection means for detecting the output overcurrent of the inverter; counting means for counting the number of times the output overcurrent detection means has detected the output overcurrent of the inverter; Count determining means for determining whether the count value of the means is equal to a predetermined value, the output overcurrent detecting means detecting the output overcurrent of the inverter, and the counting determining means determining the count value of the counting means. Is not equal to the predetermined value, an operation stop signal for stopping the operation of the compressor is output to the inverter control means for a predetermined period. When the power overcurrent detection means detects the output overcurrent of the inverter and the counting determination means determines that the count value of the counting means is equal to the predetermined value, an operation stop signal for stopping the operation of the compressor. And a compressor operation commanding means for outputting to the inverter control means.

According to the air conditioner of the first aspect, when the outside air temperature rises during the cooling operation, the temperature difference between the temperature of the switching element (power transistor, thyristor, etc.) of the inverter and the outside air temperature becomes small, and Since the cooling of the switching element by the ventilation of the fan is not sufficient, the inverter control means performs the operation when the high pressure of the compressor increases in accordance with the rise of the outside air temperature so that the temperature of the switching element of the inverter does not exceed the temperature limit. In addition, the so-called drooping control in which the input current of the inverter is changed stepwise and gradually reduced is performed to suppress the temperature rise of the switching element. However, if the motor of the outdoor fan breaks down or the outdoor fan is mechanically restrained and the air blow is stopped, and if the operation is continued, the heat radiation of the outdoor heat exchanger deteriorates, and the outdoor heat exchange becomes poor. The refrigerant pressure between the compressor and the compressor rises, causing an overload. At this time, when the output overcurrent of the inverter is detected by the output overcurrent detection means, and the counting determination means determines that the count value of the counting means is not equal to the predetermined value, the operation is stopped by the compressor operation command means. Outputting a signal to the inverter control means for a predetermined period,
The inverter control means stops the operation of the compressor, and the switching element is cooled by heat radiation. However, if the operation of the compressor is restarted without removing the cause of the inverter output overcurrent (such as a failure of the motor of the outdoor fan), the inverter output overcurrent is detected again, and the stop and operation of the compressor are stopped. Repeat alternately. When the predetermined period for stopping the operation of the compressor is short (for example, 3 minutes), the peak temperature of the switching element of the inverter gradually increases while the stop and operation of the compressor are alternately repeated, and the switching element is stopped. There is a risk of damage. Therefore, by setting a predetermined value of the counting determination means so that the compressor operation command means outputs an operation stop command to the inverter control means before the temperature of the switching element exceeds the temperature limit, the inverter control means The operation of the compressor is stopped to suppress a rise in the temperature of the switching element of the inverter. Therefore, even if the outdoor fan fails, the switching element can be protected and the cost can be reduced without using a temperature sensor for detecting the temperature of the switching element of the inverter.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an air conditioner according to the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 is a circuit diagram of an outdoor unit of an air conditioner according to an embodiment of the present invention, wherein 1 is a compressor, 2 is a four-way valve to which the discharge side of the compressor 1 is connected, and 3 is the above. An outdoor heat exchanger having one end connected to the four-way valve 2, 4 is an expansion valve connected to the other end of the outdoor heat exchanger 3, and 5 is an indoor heat exchanger (not shown) connected to the other end of the expansion valve 4. ) And an accumulator connected via the four-way valve 2. On the suction side near the outdoor heat exchanger 3, there is provided an outside air temperature sensor 6 for detecting the temperature of the outside air sucked by the outdoor fan 7.

Further, the air conditioner receives a signal indicating the outside air temperature detected by the outside air temperature sensor 7,
The control device includes a control device 11 for controlling the compressor 1 and the like, and an inverter 12 for outputting a drive signal to the compressor 1. The compressor 1 has a built-in motor (not shown) that is driven to rotate by the inverter 12. The control device 1
1 is composed of a microcomputer and an input / output circuit, etc.
An output overcurrent of the inverter 12 is detected based on an output of an inverter control unit 11a as an inverter control means for outputting a control signal to the inverter 12 and a current sensor (not shown) for detecting an output current of the inverter 12. An output overcurrent detection unit 11b as output overcurrent detection means,
A counting unit 11c as counting means for counting the number of times the output overcurrent detection unit 11b has detected the output overcurrent of the inverter 12, and a counting determination for determining whether the count value of the counting unit 11c is equal to a predetermined value. Count determination unit 11d as means
And a compressor operation command section 11e as compressor operation command means for commanding the inverter control section 11a to start / stop the compressor 1. In addition, the inverter 12
Is the power transistor attached to the radiation fin
(Not shown), and by cooling the radiating fins by blowing air from the outdoor fan 7, the power transistor is cooled so as not to exceed the temperature limit.

In the air conditioner having the above configuration, for example, when performing a cooling operation, the inverter control unit 1 of the control device 11
1a receives a signal indicating the outside air temperature from the outside air temperature sensor 6, and outputs a control signal to the inverter 12 so as to droop the input current of the inverter 12 according to the rise in the outside air temperature. FIG. 2 shows the input current of the inverter 12 with respect to the outside air temperature during the cooling operation. When the outside air temperature is lower than 40 ° C., the input current of the inverter 12 is set to 17 A (standard value). Each time the temperature rises by ° C., the drooping control for reducing the input current of the inverter 12 by ΔI (= 0.25 A) is performed. The inverter 12 shown in FIG.
The same applies to the droop control of the input current in the heating operation.

FIG. 3 shows the relationship between the operating frequency of the compressor 1 and the high pressure (refrigerant pressure between the compressor 1 and the outdoor heat exchanger 3) as input currents 17A, 16.5A, 1 of the inverter 12.
6A and 15.5A, and the shaded area at the upper right in the figure indicates the area exceeding the temperature limit of the power transistor. When the input current of the inverter 12 is constant, the load on the compressor 1 increases as the high pressure increases, and the compressor 1
Operating frequency decreases. As shown by the dotted line in FIG. 3, when the operating frequency of the compressor 1 is gradually increased at the time of the standard load where the outside air temperature is 35 ° C., the input current and the high voltage of the inverter 12 gradually increase. There is a margin before the temperature limit of the power transistor is reached. On the other hand, at the time of overload where the outside air temperature is 43 ° C., the high voltage is higher than at the time of the standard load, and when the input current is 17 A, the temperature approaches the temperature limit of the power transistor.

In FIG. 3, when the drooping control of the input current of the inverter 12 shown in FIG. 2 is performed during the cooling operation, the outside air temperature rises as indicated by the broken line at the input current 17A, and the outdoor heat exchanger 3 When the heat radiation is deteriorated and the high pressure rises, the operating frequency of the compressor 1 gradually decreases. And
When the outside air temperature exceeds 40 ° C. (point B in FIG. 2), 40 ° C.
Each time the temperature rises by 1 ° C., the input current of the inverter 12 is reduced by 0.25 A so that the temperature of the power transistor does not exceed the temperature limit. In addition, 17A of FIG.
In fact, the straight line portion above the polygonal line changes stepwise according to the current droop value in FIG.

FIG. 4 is a flowchart showing the operation of the control device 11.

Hereinafter, a process of controlling the operation of the compressor 1 by the control device 11 will be described with reference to the flowchart of FIG. In FIG. 4, before starting the above processing, the counting unit 1
The counter M of 1c is initialized to zero, and when the output overcurrent of the inverter 12 is not detected for a certain period (for example, 6 to 7 minutes), the counter M is set to zero.

First, when operation is started, step S
In step 1, the air-conditioning operation is performed.

Next, after an abnormal stop during operation in step S2, the process proceeds to step S3, where it is determined whether or not the cause of the abnormal stop is an output overcurrent of the inverter 12. And
If it is determined in step S3 that the output is an overcurrent of the inverter 12, the process proceeds to step S4, and the counter M of the counting unit 11c is incremented by one.

Next, in step S5, it is determined by the counting determining section 11d whether or not the counter M is equal to N. When it is determined that the counter M is equal to N, that is, the abnormal stop due to the output overcurrent of the inverter 12 occurs. When N times occur, the process proceeds to step S6, where the compressor operation command unit 11e outputs an operation stop signal to the inverter 12, and stops the operation of the compressor 1.

On the other hand, if it is determined in step S5 that the counter M is not equal to N, the process proceeds to step S7, where the compressor operation command section 11e outputs an operation stop signal to the inverter 12 for 3 minutes, and the operation of the compressor 1 is started. After stopping for 3 minutes, the process returns to step S1 to resume the operation.

If it is determined in step S3 that the cause of the abnormal stop is not the output overcurrent of the inverter 12, the processing based on the cause of the abnormal stop is performed. That is, the processing is performed according to the cause of the abnormal stop other than the output overcurrent of the inverter 12.

When the output overcurrent of the inverter 12 is not detected for a certain period (for example, 6 to 7 minutes), the counting unit 1
By setting the counter M of 1c to zero, the operation of the air conditioner, which is relatively likely to be stopped for a long period of time due to the output overcurrent of the inverter 12, is prevented from being stopped when the normal operation can be continued. ing.

As described above, in the above-described air conditioner, the inverter control unit 11a of the control device 11 controls the input current of the inverter 12 to droop according to the rise of the outside air temperature, thereby suppressing the rise in the temperature of the power transistor of the inverter 12.

In the case where the motor of the outdoor fan 7 breaks down or the outdoor fan 7 is mechanically restrained and the air blow is stopped, the power transistor of the inverter 12 is not cooled and the operation is continued. Then, the heat radiation of the outdoor heat exchanger 3 deteriorates, and the refrigerant pressure between the compressor 1 and the outdoor heat exchanger 3 increases, resulting in an overload. For this reason, when the output current of the inverter 12 increases and the output overcurrent detection unit 11b detects the output overcurrent of the inverter 12, the operation of the compressor 1 is stopped for 3 minutes by the compressor operation command unit 11e. When the operation of the compressor 1 is stopped, the input current of the inverter 12 becomes zero, and the temperature of the power transistor gradually decreases due to natural heat radiation. However, when the operation of the compressor 1 is automatically restarted without removing the cause of the output overcurrent of the inverter 12 (such as a failure of the motor of the outdoor fan 7), as shown in FIG. And the operation is alternately repeated. During this time, when the peak temperature of the power transistor of the inverter 12 gradually rises and the fifth output overcurrent of the inverter 12 is detected, the temperature of the power transistor of the inverter 12 reaches the temperature limit. Reach. Therefore, when the predetermined value N of the counting determination unit 11d is set to 4 and the fourth output overcurrent of the inverter 12 is detected, the inverter 1
The operation of the compressor 1 is stopped before the temperature of the power transistor 2 exceeds the temperature limit and is damaged.

Therefore, even if the outdoor fan 7 fails, the radiation fin thermistor for monitoring the temperature of the power transistor of the inverter 12 can be used without using the thermistor.
Since the power transistor can be protected, the cost of the air conditioner can be reduced.

In the above embodiment, the compressor operation command section 11e as the compressor operation command means outputs an operation stop signal to the inverter 12 for 3 minutes to stop the operation of the compressor 1 for 3 minutes. The predetermined period during which the machine operation command means outputs the operation stop signal to the inverter may be set to an appropriate value according to the operation capability of the air conditioner and the like.

In the above-described embodiment, the predetermined value N of the counting section 11c as the counting section is set to 4. However, the predetermined value of the counting section is appropriately determined according to the operating capacity of the air conditioner. May be set to an appropriate value.

In the above embodiment, a power transistor is used as a switching element of the inverter 12, but a thyristor or the like may be used as a switching element of the inverter.

[0027]

As is apparent from the above, in the air conditioner of the first aspect of the present invention, the inverter control means increases the high pressure as the operating frequency increases as the outside air temperature increases.
That outputs a control signal to the compressor inverter that drives,
When the high pressure of the compressor increases in accordance with the rise in outside air temperature
In order to prevent the temperature of the switching element of the inverter from exceeding the temperature limit, the droop control is performed to reduce the input current of the inverter in a stepwise manner and the output overcurrent of the inverter is detected by the output overcurrent detecting means. The number of times the output overcurrent detection means detects the output overcurrent of the inverter is counted by the counting means, and the compressor operation command means detects the output overcurrent of the inverter by the output overcurrent detection means, and When the counting determining means determines that the count value of the counting means is not equal to the predetermined value, the counting output means outputs a stop signal for stopping the operation of the compressor to the inverter control means for a predetermined period, and the output overcurrent detecting means outputs Is detected, and when the counting determination means determines that the count value of the counting means is equal to the predetermined value,
The operation stop signal for stopping the operation of the compressor is output to the inverter control means.

Therefore, according to the air conditioner of the first aspect of the present invention, for example, during a cooling operation, an overload occurs due to a failure of the outdoor fan and the inverter becomes an output overcurrent, and the factor of the inverter output overcurrent is eliminated. When the stop and operation of the compressor are alternately repeated without being performed, the predetermined value of the counting determination means is set so that the operation of the compressor is stopped before the temperature of the switching element exceeds the temperature limit. Temperature rise of the switching element can be suppressed. Therefore, even if the outdoor fan fails, the switching element can be protected without using a temperature sensor for detecting the temperature of the switching element of the inverter, and the cost of the air conditioner can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an outdoor unit of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a diagram showing a current droop value with respect to an outside air temperature of a compressor of the air conditioner.

FIG. 3 is a diagram showing a relationship between an operating frequency of a compressor of the air conditioner and a high pressure.

FIG. 4 is a flowchart showing an operation of the control device of the air conditioner.

FIG. 5 is a diagram showing a temperature change of a power transistor when output overcurrent of an inverter of the air conditioner is repeatedly detected.

FIG. 6 (a) is a top view of the inside of an electrical component box of a conventional air conditioner, and FIG. 6 (b) is a side view of the electrical component box.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Four-way valve, 3 ... Outdoor heat exchanger, 4 ... Expansion valve, 5 ... Accumulator, 6 ... Outdoor air temperature sensor, 7 ... Outdoor fan, 11 ... Control device, 11a ... Inverter control part, 11b ... Output overcurrent detection section, 11c ... Counting section, 11d ... Counting determination section, 11e ... Compressor operation command section, 12 ... Inverter.

Continuation of the front page (56) References JP-A-5-99519 (JP, A) JP-A-2-214499 (JP, A) JP-A-1-136842 (JP, U) (58) Fields surveyed (Int .Cl. ⁷ , DB name) F24F 11/02

Claims (1)

(57) [Claims] 1. The higher the operating frequency, the higher the high pressure
That an inverter for driving the compressor (1) (12), and outputs a control signal to the inverter (12), the outside air temperature
When the high pressure of the compressor (1) increases in accordance with the rise in the temperature of the compressor, the temperature of the switching element of the inverter (12) does not exceed the temperature limit. Inverter control means (11a) for performing droop control to reduce the input current of step (12) by changing it stepwise
An output overcurrent detecting means (11b) for detecting an output overcurrent of the inverter (12); and the output overcurrent detecting means (11b)
Counting means (1) for counting the number of times the output overcurrent is detected in 2);
1c), counting determining means (11d) for determining whether or not the count value of the counting means (11c) is equal to a predetermined value, and output overcurrent detecting means (11b).
2) The output overcurrent is detected, and the counting determination means (1)
If 1d) determines that the count value of the counting means (11c) is not equal to the predetermined value, it outputs an operation stop signal for stopping the operation of the compressor (1) to the inverter control means (11a) for a predetermined period. Together with the output overcurrent detection means (1)
1b) detects the output overcurrent of the inverter (12), and when the counting determining means (11d) determines that the counting value of the counting means (11c) is equal to the predetermined value, the compressor
Compressor operation command means (11e) for outputting an operation stop signal for stopping the operation of (1) to the inverter control means (11a).
An air conditioner comprising: