JPH1137571A - Air conditioner - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an effective load-reducing operation without special means for liquid compression or the like during cooling and without losing the comfort during heating. SOLUTION: A bypass valve 6 having a flow resistance and opening / closing according to the refrigerant pressure from an outdoor heat exchanger 2 and a pressure reducer 3 in a refrigeration cycle to a refrigerant inlet of the compressor 1.
And a bypass passage comprising a bypass pressure reducer and a refrigerant temperature detecting device provided in the indoor heat exchanger. During the cooling operation, when the pressure of the protruding refrigerant gas of the compressor 1 exceeds a predetermined value, the bypass is activated to reduce the load. During the heating operation, the microcomputer 10 obtains a predicted temperature T from the refrigerant temperature To detected by the temperature detecting device 8 in consideration of a change speed of the refrigerant temperature and a time lag time, and the predicted temperature T exceeds the load determination value. At this time, it is predicted that an overload state will occur, and the outdoor blower 14 and the indoor blower 1
3. Control the compressor 1 to reduce the load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner, and more particularly to an air conditioner suitable for ensuring the reliability of a compressor or the like under a high load.

[0002]

2. Description of the Related Art In an air conditioner, the compressor is overloaded due to an imbalance between the amount of heat absorbed and the amount of heat released in an outdoor heat exchanger or an indoor heat exchanger, and the temperature and pressure of the refrigerant in the compressor are increased. When the pressure is abnormally high, the cylinder and the like of the compressor are damaged due to the deterioration of the lubricating oil and the like, which affects the operation and life of the compressor and the like.

In order to solve such a problem and secure the reliability of a compressor or the like, a conventional method has been proposed in Japanese Patent Application Laid-Open No. 61-21765.
In the refrigeration cycle in which the refrigerant flows from the compressor through the condenser, the expansion valve, and the evaporator to return to the compressor, a bypass circuit for bypassing the refrigerant between the expansion valve and the evaporator is provided. Is disclosed which comprises a capillary tube and a solenoid valve.

In such a refrigerator, the temperature of the refrigerant gas discharged from the compressor is detected by a temperature sensor, and when the detected temperature exceeds a predetermined temperature, the compressor is regarded as being in an overloaded state and is normally closed. The valve is opened to allow a part of the liquid refrigerant sent from the condenser to flow to the bypass circuit.
In the bypass circuit, the pressure of the liquid refrigerant is reduced by the capillary tube, mixed with the refrigerant gas from the evaporator via the solenoid valve, and returned to the compressor. As a result, the refrigerant gas from the evaporator is cooled by the liquid refrigerant from the bypass circuit, and the temperature of the refrigerant gas discharged from the compressor decreases, and the compressor is released from the overload state. Thus, the reliability of the compressor is ensured.

On the other hand, in a conventional air conditioner, as a control for reducing the load on the compressor during a heating operation, when the refrigerant temperature exceeds a set operating value, the rotational speed of the compressor may be reduced. The load on the compressor can be reduced by changing the number of revolutions of the indoor blower or the outdoor blower to change the amount of heat radiation or heat absorption of the heat exchanger. In addition,
The operation value is a constant value set assuming a certain load state.

Japanese Patent Application Laid-Open No. Sho 62-37093 discloses that in a rotational speed control type air conditioner, the pressure of refrigerant gas discharged from the compressor is controlled to a certain value or less in order to reduce the load on the compressor. A method is disclosed. This focuses on the fact that the lower the rotation speed of the compressor, the higher the pressure of the refrigerant gas discharged from the compressor, and sets a limit value according to the rotation speed of the compressor as an operation value, and sets the input DC of the inverter. By controlling the inverter so that the current does not exceed the limit value, the pressure of the refrigerant gas discharged from the compressor is reduced to a certain value or less. When the input DC current exceeds the limit value, it is determined that the compressor is in an overload state, and the rotation speed is changed. In this case, the limit value is basically constant, and the input DC current value in the overload state is different depending on the rotation speed of the compressor. Therefore, the limit value is changed according to the rotation speed. .

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
According to the prior art described in JP 7655-B, during the cooling operation of the air conditioner, by operating the bypass circuit, the refrigerant from the evaporator is cooled by the low-temperature refrigerant from the bypass circuit. The temperature of the discharged refrigerant gas decreases, and the reliability of the compressor can be ensured.

However, such prior art does not take into account the pressure of the discharged refrigerant necessary for ensuring the reliability of the compressor. Therefore, it is conceivable to use a high-pressure sensor instead of the high-temperature sensor and open and close the solenoid valve according to the detected pressure. However, a control means for controlling the opening and closing of the solenoid valve according to the detected pressure is used. In order to reduce the pressure of the refrigerant gas discharged from the compressor, a considerable amount of liquid refrigerant must be returned from the bypass circuit to the compressor.
For this reason, the compressor requires special means for dealing with liquid compression and the like.

On the other hand, during the heating operation of the air conditioner, as described above, the operation value is constant, and when the operation value is exceeded, the overload reduction operation starts. Here, it is detected that the refrigerant temperature or the input DC current of the inverter (hereinafter referred to as a state value) exceeds an operation value, and based on this, the load reduction operation is started and the effect is obtained until the effect is obtained. There is a time lag, and therefore, in consideration of the time lag, the operation value is set to a lower value so that the load reduction operation is started earlier.

However, when the operating value is set in this way,
The following problems arise.

When the heating operation is being performed in the same overload state as the overload state for which the operation value is determined, FIG.
As shown in 2), the state value changes. That is, now, the state value rises due to the high load, and when the state value exceeds the operation value, the load reduction operation starts, and its effect appears with a predetermined time lag. Since the operating value is set so as not to enter the overload region, this time lag elapses before the state value enters the overload region, and therefore, the state value does not enter the overload region, The load reduction operation is performed without any problem.

When the load is larger than the above, the rate of increase of the state value is higher than the above. For this purpose, FIG.
As shown in (b2), even if this state value exceeds the operation value and the load reduction operation is started, if a time lag has elapsed since that time, the state value enters the overload region, and from this state the load is reduced. The effect of the reduction operation appears, and the state value is reduced. As described above, the overshoot of the state value to the overload region occurs, and the overshoot increases as the load increases, so that the compressor cannot be completely protected.

Although the load is smaller than the case shown in FIG. 3 (a2), the state value may exceed the operation value in some cases. In such a case, the rate of increase of the state value is small,
As shown in FIG. 3 (c2), even if the state value exceeds the operation value, the load reduction operation is started regardless of the case where the overload region is not reached, and the effect appears after the elapse of the time lag. The state value decreases. For this reason, the compressor does not operate efficiently and the comfort during heating is lost.

A first object of the present invention is to solve the above problems, to reduce the load during cooling by avoiding a complicated structure and an increase in the scale, and to reduce the air load during cooling, and to ensure the reliability of the compressor. To provide a harmony machine.

A second object of the present invention is to provide an air conditioner capable of performing an effective load reduction operation without losing the comfort during heating and ensuring the reliability of the compressor. It is in.

[0016]

In order to achieve the above first object, the present invention provides a method for connecting an outdoor heat exchanger and an indoor heat exchanger in parallel with a decompressor and an indoor heat exchanger of a refrigeration cycle. A bypass passage having a bypass valve that opens at an opening corresponding to the refrigerant pressure when the refrigerant pressure is equal to or higher than a predetermined threshold value set according to the overload state of the compressor.

With this configuration, during the cooling operation, the load on the compressor increases and the pressure of the discharged refrigerant gas increases. As a result, when the pressure of the refrigerant output from the outdoor heat exchanger becomes equal to or higher than the predetermined threshold value. The amount of low-temperature refrigerant corresponding to the refrigerant pressure is returned to the compressor by a bypass, bypassing the decompressor and the indoor heat exchanger, and lowering the refrigerant temperature in the compressor to discharge the compressor. Reduce the pressure of the refrigerant gas. This reduces the load on the compressor. In addition, since a part of the refrigerant passes through the bypass path, the amount of the refrigerant in the indoor heat exchanger decreases, and the amount of heat absorbed decreases. As a result, the load on the compressor is reduced, and the pressure of the refrigerant gas discharged from the compressor is reduced. In this way, the bypass valve is operated so that the refrigerant gas pressure discharged from the compressor is maintained at the predetermined threshold, and the load on the compressor is reduced. Further, since the bypass valve opens and closes according to the pressure of the refrigerant, there is no need for a means for detecting the pressure of the refrigerant or a control means for the valve.

Further, in order to achieve the first object,
In the present invention, a bypass decompressor for reducing the pressure of the refrigerant that has passed through the bypass valve is provided in the bypass passage.

With this configuration, the refrigerant passing through the bypass passage is vaporized by the bypass valve and the bypass pressure reducer to become a refrigerant gas, and the refrigerant gas returns to the compressor. For this reason, in the compressor, the liquid compression by the liquid refrigerant can be prevented, and there is no need to provide any special means for dealing with the liquid compression.

In order to achieve the second object, the present invention provides a temperature detecting means for detecting a temperature of a refrigerant in an indoor heat exchanger, and an overload of a compressor based on a temperature detected by the temperature detecting means. Control means for detecting a state of the compressor, controlling at least one of the compressor, the outdoor blower, and the indoor blower to reduce the load on the compressor; and the control means detects a temperature detected by the temperature detection means. And a predicted temperature after a predetermined time determined from the temperature change rate at that time, and when the predicted temperature exceeds an overload determination value indicating an overload state of the compressor,
It is determined that the compressor is overloaded.

With this configuration, when the temperature of the refrigerant is detected during the heating operation, the change in the pressure of the refrigerant gas discharged from the compressor can be predicted from the change speed of the temperature at that time.
Thereby, it is possible to determine whether or not to enter an overload state. For this reason, when the load is large, the load reducing operation is performed regardless of the rate of increase in the temperature of the refrigerant as long as the pressure of the discharged refrigerant gas is predicted to enter the overload region. If the load does not enter the overload region and the load is small and the temperature of the refrigerant rises slowly, the load reducing operation is performed until the pressure of the discharged refrigerant gas is predicted to enter the overload region. The operation of the compressor is performed efficiently, and the comfort during heating is not impaired.

There is a time lag from the start of the load reduction operation until the effect such as the pressure of the refrigerant actually decreases appears. Therefore, control is performed such that the load reduction operation is started earlier by the time lag time. The operation value for entering the load reduction operation earlier is obtained from the time lag time (predetermined time) specific to the air conditioner, the overload determination value, the current refrigerant temperature, and the change speed thereof.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an air conditioner according to the present invention, wherein 1 is a compressor, 2 is an outdoor heat exchanger, 3 is a decompressor, 4 is an indoor heat exchanger, and 5 is a switching valve ( For example, a four-way valve), 6 is a bypass valve, 7 is a bypass decompressor, 8 is a temperature detecting device, 9 is a control circuit, 10 is a microcomputer (hereinafter, referred to as a microcomputer), 11 is a memory, 12a to 12c are relays, 13 Is an indoor blower, 14
Is an outdoor blower.

In FIG. 1, a switching valve (four-way valve) 5 is connected by a pipe to the refrigerant gas discharge side of the compressor 1 so that the compressed refrigerant gas discharged from the compressor 1 is switched in the direction indicated by the arrow. Sent to 5. An outdoor heat exchanger 2, a decompressor 3, and an indoor heat exchanger 4 are sequentially arranged from the switching valve 5, and the switching valve 5
The piping is further connected from the switching valve 5 to the refrigerant input side of the compressor. Thus, a refrigerating cycle is formed by the compressor 1, the outdoor heat exchanger 2, the decompressor 3 and the indoor heat exchanger 4, and the switching valve 5 causes the outdoor heat exchanger 2, the decompressor 3 and the indoor heat The direction in which the refrigerant flows in the path including the exchanger 4 can be switched. However, in any flow direction, the refrigerant discharged from the compressor 1 in the direction of the arrow flows from the switching valve 5 to this path, and returns to the switching valve 5 and is input to the compressor 1 in the direction of the arrow. You.

The outdoor heat exchanger 2 is provided with an outdoor blower 14, and the indoor heat exchanger 4 is provided with an indoor blower 13, which are controlled by a control circuit 9.

A bypass valve 6 is provided between the outdoor heat exchanger 2 and the pressure reducer 3 to bypass the pressure reducer 3, the indoor heat exchanger 4, and the switching valve 5 from the refrigerant inlet of the compressor 1. A bypass including the bypass pressure reducer 7 is provided. When the pressure of the refrigerant gas between the outdoor heat exchanger 2 and the pressure reducer 3 is equal to or higher than a predetermined value, the bypass valve 6 opens at an opening corresponding to the pressure. Also, the bypass pressure reducer 7
The pressure of the refrigerant passing through the bypass valve 6 is reduced.

Further, the indoor heat exchanger 4 is provided with a temperature detecting device 8 for detecting the temperature of the refrigerant there.
The control circuit 9 controls the indoor blower 13, the outdoor blower 14, the compressor 1 and the like according to the detected temperature.

The control circuit 9 includes a microcomputer 10 having a memory 11 and relays 12a to 12c. The memory 11 stores data such as an overload determination value for determining whether or not an overload state has occurred and a time lag time from when the load reduction operation is started to when the load reduction effect actually appears. Further, the detected temperature of the temperature detecting device and the arithmetic processing data taken by the microcomputer 10 are also stored in this memory. The microcomputer 10 detects the load state of the compressor 1 by taking in the detected temperature of the temperature detecting device 8 during the heating operation and performing arithmetic processing using the data stored in the memory 11, and detects the overload state. The outdoor blower 14, the compressor 1, and the indoor blower 13 are controlled by the relays 12a to 12c so as not to be out of order.

Here, the relay 12a turns on and off, whereby the outdoor blower 14 turns on and off. The relay 12b is also turned on and off, so that the compressor 1 is turned on and off. Relay 1
2c switches the rotation speed of the indoor blower 13 to, for example, three stages.

The control for adjusting the room temperature according to this embodiment can be the same as that of the conventional air conditioner, and the description thereof is omitted.

Next, the operation of this embodiment will be described.
First, the operation during the cooling operation will be described.

During the cooling operation, the switching valve 5 forms a cooling cycle. That is, the refrigerant gas discharged from the compressor 1 is sent from the switching valve 5 to the outdoor heat exchanger 2 to radiate heat,
It condenses to liquid refrigerant. This liquid refrigerant is decompressed and decompressed by the decompressor 3, sent to the indoor heat exchanger 4 as a refrigerant gas to absorb indoor heat, and sent to the compressor 1 through the switching valve 5. In this case, to increase the cooling efficiency, the indoor blower 13 and the indoor blower 14 are appropriately operated.

Here, when the pressure of the condensed liquid refrigerant between the outdoor heat exchanger 2 and the pressure reducer 3 becomes equal to or higher than a predetermined pressure value indicating that the compressor 1 enters an overload state, The bypass valve 6 opens at an opening corresponding to the pressure of the liquid refrigerant, whereby the refrigerant passes through the bypass passage, and a part of the liquid refrigerant sent from the outdoor heat exchanger 2 is partially decompressed by the decompressor 3 or the indoor heat exchanger 4. The switching valve 5 will be bypassed.

In the bypass passage, the liquid refrigerant passing therethrough is decompressed by a bypass valve 6 or a bypass decompressor 7 having a flow resistance, is vaporized as a refrigerant gas, is mixed with the refrigerant gas from the indoor heat exchanger 4, and is compressed. Sent to 1. At this time, since the temperature of the liquid refrigerant sent from the outdoor heat exchanger 2 is low, the temperature of the refrigerant gas mixed with the refrigerant gas from the indoor heat exchanger 4 through the bypass passage is also low. Further, since the amount of the refrigerant gas sent to the indoor heat exchanger 4 passing through the bypass passage is small, the amount of heat absorbed from the room is small. Therefore, when low-temperature refrigerant gas from the bypass path is mixed with the refrigerant gas from the indoor heat exchanger 4, the refrigerant gas input to the compressor 1 is effectively cooled and becomes low. In addition, the pressure of the refrigerant gas discharged from the compressor 1 can be reduced. That is, the load on the compressor 1 is reduced.

In this way, the load reduction operation of the compressor can be effectively performed at a high load without providing the refrigerant pressure detecting means or the valve control means in the bypass passage as in the conventional air conditioner. The reliability of the compressor 1 can be ensured.

In the bypass line, the refrigerant passing therethrough is vaporized by the bypass valve 6 and the bypass decompressor 7 and returned to the compressor 1, so that the liquid compression by the liquid refrigerant in the compressor 1 is prevented. It can also be prevented and no special measures are needed to deal with this liquid compression.

Next, the heating and rolling of this embodiment will be described.

In the heating operation, the relays 12a, 12b, 1
2c is on, whereby the outdoor blower 14, the compressor 1 and the indoor blower 13 are operating. Further, the switching valve 5 is switched to form a heating cycle in which the refrigerant flows in a direction opposite to that in the cooling operation. That is, the high-temperature, high-pressure refrigerant gas discharged from the compressor 1 is sent from the switching valve 5 to the indoor / outdoor heat exchanger 4 to radiate heat to the room. This refrigerant gas is further decompressed by the decompressor 3, absorbs heat from the outside air in the outdoor heat exchanger 2, and passes through the switching valve 5,
It is sent to the compressor 1. At this time, in the outdoor heat exchanger 2, the outdoor air is blown in by the outdoor blower 14, so that the refrigerant efficiently absorbs the outdoor heat, and
In the indoor heat exchanger 4, since the indoor air is sucked in and blown out by the indoor blower 13, warm air due to the heat radiation of the refrigerant is blown into the room.

In this heating operation, the pressure of the refrigerant between the pressure reducer 3 and the outdoor heat exchanger 2 is reduced by the pressure reducer 3, and the bypass valve 6 does not open.
The operation of reducing the load by the bypass is not performed. Therefore, during the heating operation, a load reducing operation described below is performed.

When the outside air temperature is high or the amount of air blown indoors is small, the amount of heat absorbed in the entire heating cycle is larger than the amount of heat released, so that the compressor 1 increases the pressure and temperature of the refrigerant gas discharged from the compressor. As a result, an overload condition may occur.

Therefore, in the control circuit 9, the microcomputer 10
Calculates the detected temperature To of the temperature detector 8 in the indoor heat exchanger 4 and the data in the memory 11 to predict the temperature of the refrigerant after a lapse of the time lag from the current refrigerant temperature To (this predicted temperature). Is referred to as a predicted temperature T), and it is determined whether or not an overload state occurs by detecting whether or not the predicted temperature T is equal to or higher than a set overload determination value.

Here, the predicted temperature T can be obtained by the following equation (1) according to, for example, the proportional method. T = To + K · R · ΔT (1) where: T: predicted temperature (° C.) To: current refrigerant temperature (° C.) K: proportionality constant R: time lag time (second) ΔT: temperature change rate (° C / sec).

The temperature change rate ΔT is determined by the microcomputer 1
The period of taking in the detected temperature from the temperature detector 8 of 0 is Δ
Assuming that t is (where Δt> R) and the detected temperature taken immediately before is To ′, it is expressed by the following equation (2). ΔT = (To−To ′) / Δt (2) In order to calculate this equation (2), the detected temperature from the temperature detecting device 8 is stored in the memory 11 at least until the next detected temperature is fetched. deep. Further, the fetch period Δt is also stored in the memory 11.

The time lag time R differs depending on the structure of the air conditioner. For example, even if the outdoor air blower 14 is turned off by turning off the outdoor air blower relay 12a, it continues to rotate for a while due to the inertia of the propeller. Therefore, heat is continuously absorbed by the outdoor heat exchanger 2 for several seconds to several tens of seconds during that time. This time lag time R is also stored in the memory 11.

Further, since the refrigerant temperature that changes during the lapse of the time lag time R gradually becomes saturated, the actual refrigerant temperature after the lapse of the time lag time R is smaller than the predicted temperature obtained with the current temperature change rate ΔT. Lower. For this reason,
It is necessary to set the predicted temperature T in consideration of this, and therefore, the proportionality constant K is set in the range of 0 ≦ K ≦ 1. As in the case of the time lag time R and the like, it differs depending on the structure of the air conditioner, but is about 0.8. This proportional constant K is also stored in the memory 11.

The predicted temperature T obtained in this way is compared with the overload determination value stored in the memory 11, and when it exceeds this, it is determined that an overload state is entered, and the microcomputer 10 performs the load reduction operation. To start. This load reduction operation is performed by turning on or off the compressor 1 by controlling any or all of the relays 12a to 12c,
Is turned on and off, and the rotation speed of the indoor blower 13 is switched.

In the following, a description will be given of the load reduction operation accompanying this overload determination with reference to FIG. 2. FIG. 2 shows the load reduction operation, the load reduction release and the determination values in steps as an example as follows. Is defined.

Overload determination value 1 = 56 ° C. Load reduction release determination value 1 = 50 ° C. Overload determination value 2 = 58 ° C. Load reduction release determination value 2 = 51 ° C. Overload determination value 3 = 64 ° C. Load reduction release determination value 3 = 52 ° C Load reduction 1 operation = relay 12a is turned off and outdoor blower 1
4 Stop the load reduction 2 operation = switch the relay 12c to increase the rotation speed of the indoor blower 13 Load reduction 3 operation = turn off the relay 12b and stop the compressor 1 Also, release the load reduction 1 and release the load reduction 2 and load The relief 3 release is a control opposite to the above-described load reduction 1 operation, load reduction 2 operation, and load reduction 3 operation, respectively.

In FIG. 2, when the heating operation is started, the microcomputer 10 turns on the relays 12a to 12c to operate the compressor 1, the outdoor blower 14, and the indoor blower 13. Thereby, a heating cycle is formed, and the room is heated.

At the start of the heating operation, the temperature detecting device 8 attached to the indoor heat exchanger 4 detects the refrigerant temperature (step 101), and the microcomputer 10 takes in the detected temperature To, so that the compressor 1 The pressure of the discharged refrigerant gas is artificially detected (step 102). Here, as described above, the acquisition of the detected temperature To of the temperature detection device 8 is performed in the above-described cycle Δt. Here, it is assumed that the second and subsequent acquisitions have been performed. Therefore, the detected temperature To ′ previously taken is stored in the memory 11.

When the microcomputer 10 receives the detected temperature To, the microcomputer 10 reads the previously detected detected temperature To ′ from the memory 11.
Is read (step 103), and these detected temperatures To,
The temperature change rate ΔT is obtained from To ′ by the above equation (2) (step 104). And further, the memory 11
Then, the proportional constant K and the time lag time R are read out from the above, and the calculation of the above equation (1) is performed to obtain the predicted temperature T after the lapse of the time lag time R (step 105).

Next, the overload judgment value is read from the memory 11 and compared with the predicted temperature T obtained. First, the predicted temperature T is compared with the lowest overload judgment value 1 (= 56 ° C.). (Step 106). Here, if the predicted temperature T ≦ the overload determination value 1, it is determined that the overload state will not occur even after the elapse of the time lag time R, and then the lowest load reduction release determination value 1 (= 50 ° C.) (Step 1
08). Here, if the predicted temperature T ≦ the load reduction release determination value 1, it is determined that the heating efficiency is not sufficient, the load reduction 1 release operation is performed, and the outdoor blower 14 is brought into the operating state (on state) (step 109). Then, the load reduction 2 release operation is performed to reduce the rotation speed of the indoor blower 14 (step 113), and the compressor 1 is brought into the operating state (step 11).
7). Then, the process returns to step 101 in which the temperature detection device 8 performs the next temperature detection.

When the load on the compressor 1 increases in the continuous heating operation and the calculated predicted temperature T exceeds the overload determination value 1 (= 56 ° C.) (step 106), the compression is performed before the time lag time R elapses. It is determined that the machine 1 is in an overload state, and the load reduction 1 operation is started immediately (step 10).
7). That is, the microcomputer 10 turns off the relay 12a,
The outdoor blower 14 is stopped. Next, the predicted temperature T is compared with the overload determination value 2 (= 58 ° C.).
Assuming that ℃ <predicted temperature T ≦ 58 ° C., the predicted temperature T ≦
Since it is the overload determination value 2 (step 110), the predicted temperature T is compared with the load reduction release determination value 2 (= 51 ° C.) (step 112). At this time, since the predicted temperature T ≦ the load reduction release determination value 2, the load reduction 2 release operation is performed to reduce the rotation speed of the indoor blower 14 (step 113), and the load reduction 3 release operation is performed to execute the compressor 1 release. Is set to the operating state (step 117). Then, the process returns to step 101 in which the temperature detection device 8 performs the next temperature detection.

If it is assumed that the load on the compressor 1 is further increased and the speed of temperature change is so large that 58 ° C. <predicted temperature T ≦ 64 ° C., the predicted temperature T> overload judgment value 1 (step 107), Predicted temperature T> overload determination value 2 (step 11
0), the outdoor fan 14 is stopped by performing the load reduction 1 operation (step 107), and the rotation speed of the indoor blower 13 is switched to a higher speed by performing the load reduction 2 operation (step 111). And then,
The predicted temperature T is compared with the overload determination value 3 (= 64 ° C.). At this time, since the predicted temperature T ≦ the overload determination value 3 (step 114), the predicted temperature T is reduced to the load reduction release determination value 3 ( = 52 ° C) (step 116). At this time, since the predicted temperature T ≦ the load reduction release determination value 3, the load reduction 3 release operation is performed to put the compressor 1 into the operating state (step 117). Then, the process returns to step 101 in which the temperature detection device 8 performs the next temperature detection.

If it is assumed that the load on the compressor 1 is higher and the temperature change rate is higher and 64 ° C. <the predicted temperature T, the predicted temperature T> the overload judgment value 1 (step 10
7), predicted temperature T> overload determination value 2 (step 11)
0), predicted temperature T> overload determination value 3 (step 114)
Therefore, the load reduction 1 operation is performed and the outdoor blower 14
Is stopped (step 107), the load reduction 2 operation is performed, the rotational speed of the indoor blower 13 is switched to a higher speed (step 111), and the load reduction 3 operation is performed to stop the compressor 1. Then, the process returns to step 101 in which the temperature detection device 8 performs the next temperature detection.

In this way, when the load of the compressor 1 is high and the load rising speed is not so fast based on the predicted temperature T, it is predicted that the compressor 1 will be overloaded after the time lag time R. In order to reduce the load on the compressor 1 by stopping the outdoor blower 14 to reduce the amount of heat absorbed in the outdoor heat exchanger 2, the load on the compressor 1 is further higher, and the rate of increase of the load is higher. When it is predicted that the compressor 1 will be overloaded after the time lag time R, the outdoor blower 14 is stopped to reduce the amount of heat absorbed in the outdoor heat exchanger 2 and to rotate the indoor blower 13. The speed is further increased to increase the amount of heat radiation in the indoor heat exchanger 4 to reduce the load on the compressor 1. If the load on the compressor 1 is higher than this, and the load rising speed is very fast, and it is predicted that the compressor 1 will be overloaded more rapidly within the time lag time R, the outdoor blower 14
Is stopped, the amount of heat absorbed in the outdoor heat exchanger 2 is suppressed, the rotation speed of the indoor blower 13 is further increased to increase the amount of heat released in the indoor heat exchanger 4, and the compressor 1 is stopped.
The load on the compressor 1 is reduced. As described above, the load reduction operation is switched stepwise according to the magnitude of the load on the compressor 1, whereby an efficient load reduction operation can be performed.

The load on the compressor 1 is reduced by the above-described load reducing operation. However, if the load reducing operation is continued as it is, the load is abnormally reduced, and the compressor 1 can sufficiently exhibit its performance. The heating efficiency is reduced, and the comfort is impaired. For this reason, it is necessary to cancel the load reduction operation. The load reduction cancellation determiners 1, 2, and 3 are set, and the load reduction operation is canceled based on these.

Here, in this embodiment, as described above, the magnitude of the load on the compressor 1 (overload determination values 1, 2,
3) Since the operations of the load reduction operations 1, 2, and 3 are performed every time, the release of the load reduction operation is made different depending on the type of the load reduction operation being performed.
This prevents the load from becoming abnormally large immediately after the load reduction operation. For example, when the load reduction 1, 2, 3 operation is performed because the load becomes abnormally large, the load reduction 1, 2, 3
If the operations are canceled at the same time, there may be a case where the overload state is immediately attempted due to the large load originally. Therefore, immediately after the cancellation of the load reduction operations, the load reduction operations are re-entered. As a result, activation and release of these load reduction operations are repeated simultaneously and in a short cycle, so that a load is imposed on the compressor 1 and the blowers 13 and 14, and power consumption increases.

In this embodiment, such a problem can be solved. In FIG. 2, the load reduction 1, 2, 3 operation is performed and the outdoor blower 14 is stopped.
The indoor blower 13 is rotating at a high rotation speed, and the compressor 1 is in a load reducing operation state in which the compressor 1 is stopped.
Predicted temperature T obtained by a series of operations from 01 to 105
Is lower than 64 ° C., and 58 ° C. <predicted temperature T ≦ 6
If the temperature reaches 4 ° C., the load reduction 1 operation and the load reduction 2 operation are not canceled (steps 106, 107, and 11).
0,111), predicted temperature T ≦ overload judgment value 3 (= 64
° C), the predicted temperature T is compared with the load reduction release determination value 3 (= 52 ° C) (step 116). At this time, since the predicted temperature T> the load reduction release determination value 3,
Return to Step 101 without canceling the load reduction 3
This operation is repeated.

Thereafter, the load is reduced to 56 ° C.
<When predicted temperature T ≦ 58 ° C., step 10
A series of operations 1 to 107, 110, 112, 114, and 116 are repeated, and the load is further reduced to 52
C. (= load reduction release determination value 3) <predicted temperature T ≦ 56 ° C., steps 101 to 106, 108, 1
A series of operations of 10, 112, 114, and 116 are repeated. During these operations, the load reductions 1, 2, and 3 are not released.

Thereafter, the load on the compressor was further reduced to 5
1 ° C. (= load reduction release determination value 2) <predicted temperature T ≦ 52 ° C.
When (= load reduction release determination value 3), step 101 is reached.
After the processing of 106, 108, 110, 112, and 114 is performed, the predicted temperature T at this time is compared with the load reduction release determination value 3 (step 116). At this time, the predicted temperature T <load Since the lightening cancellation determination value is 3, the lightening cancellation 3 is canceled (step 117). As a result, the compressor 1 starts and returns to step 101.

In this state, when the load on the compressor 1 increases and the predicted temperature T increases, the above-described steps 101 to 101 are performed.
A series of operations of 106, 108, 110, 112, 114 and 116 is repeated, and when the predicted temperature T exceeds 64 ° C., the load reduction 3 operation is performed again and the compressor 1 is stopped. Conversely, the load reduction 3 is canceled (step 117), and even if the compressor 1 is started, the predicted temperature T decreases to 50 ° C. (= load reduction release determination value 1) <predicted temperature T When ≦ 51 ° C. (= load reduction release determination value 2), steps 101 to 106, 108, and 11
After the processing of 0 is performed, the predicted temperature T at this time is compared with the load reduction release determination value 2 (step 11).
2) At this time, since the predicted temperature T ≦ the load reduction release determination value 2, the load reduction 2 is released (step 11).
3). As a result, the rotation speed of the indoor blower 113 decreases, and the process returns to step 101 via step 113.

The operation of the compressor 1 and the indoor blower 113
If the predicted temperature T rises due to the decrease in the rotational speed, the load reduction 2 operation is finally performed to increase the rotational speed of the indoor blower 113 (step 111). Ascending, as above,
The load reducing 3 operation is performed to start the compressor 1 (step 115), but as described above, the compressor 1 is started.
Is stopped and the rotational speed of the indoor blower 113 is further reduced, the predicted temperature T decreases, and the predicted temperature T ≦ 50 ° C. (=
When the load reduction release determination value 1) is reached, steps 101 to 1
After the processing of step 06 is performed, the predicted temperature T at this time is compared with the load reduction release determination value 1 (step 1).
08) At this time, predicted temperature T ≦ load reduction release determination value 1
Therefore, the load reduction 1 is canceled (step 1).
09). Accordingly, the outdoor blower 114 starts operating, and returns to step 101 via steps 113 and 117.

In this way, the load is reduced step by step.
2 and 1 are canceled, and a sudden load change in the compressor 1 due to simultaneous cancellation is prevented.

For example, when it is desired to control the pressure of the refrigerant gas discharged from the compressor 1 to 2.55 MPa, the temperature detected by the temperature detecting device 8 in the above example depends on the configuration of the heating cycle. When the temperature is 56 ° C. or higher, an overload state is set.

FIGS. 3 (a1) to 3 (c1) are characteristic diagrams of the change in the detected temperature due to the load reduction operation of this embodiment under typical load conditions.

FIG. 3 (a1) shows a change characteristic of the detected temperature when the compressor 1 is in a high load state. The microcomputer 10 predicts the change after the lapse of the time lag time R from the detected temperature To of the temperature detecting device 8. The temperature T is obtained, and when the predicted temperature T exceeds the overload determination value, the load reduction operation is started. The overload determination value is the overload determination value 1, 2, or 3 in FIG. 2, and the load reduction operation is performed by the load reduction 1 operation or the load reduction in FIG. 1, 2 operation or load reduction 1, 2, 3 operation.

Therefore, when the load on the compressor 1 is high,
Although the refrigerant temperature detected by the temperature detecting device 8 rises, when the predicted temperature T obtained from the detected temperature To of the temperature detecting device 8 exceeds the overload judgment value, the load reducing operation is started. As a result, the refrigerant temperature further rises,
By this load reducing operation, the rise is suppressed, and even after the time lag time R has passed, the load does not exceed the overload determination value and decreases. Therefore, the compressor 1 does not become overloaded.

In the above-mentioned conventional air conditioner, under the same load condition (that is, for example, the change speed of the refrigerant temperature is equal), the operating value is appropriately set, thereby obtaining
As described in (a2), the compressor can be prevented from being overloaded.

FIG. 3 (b1) shows a case where the load is higher than in the case of FIG. 3 (a1). In this case, the rising speed of the detected temperature is faster than in the case of FIG.

In this case, the refrigerant temperature detected by the temperature detecting device 8 rises more rapidly, but the predicted temperature T obtained from the detected temperature To of the temperature detecting device 8 is still higher.
When the load exceeds the overload determination value, a load reduction operation starts. As a result, the refrigerant temperature further rises, but this load reduction operation suppresses the rise, and does not exceed the overload determination value even after the time lag time R,
It is going down. Therefore, the compressor 1 does not become overloaded.

In this case, however, since the rate of rise of the refrigerant temperature is high, the rise temperature (K · R · ΔT in the above equation (1)) determined by the microcomputer 10 has been described with reference to FIG. 3 (a1). Since it is larger than the case, it can be predicted that the compressor 1 will be overloaded when the detected temperature To in this case is lower than the detected temperature To in FIG. 3 (a1). Even if the rate of rise of the detected temperature increases, it is possible to avoid an overload state.

On the other hand, in the above conventional air conditioner,
When the rate of rise of the refrigerant temperature is the same as in the case of FIG. 3 (b1), since the operating value is constant as described in FIG. 3 (b2), when this refrigerant temperature exceeds the operating value, When the load reduction operation is started, a decrease in the refrigerant temperature due to the load reduction operation appears after the elapse of the time lag time, so that the load overshoots within the overload state and enters the overload state. The overshoot amount increases as the rate of rise of the refrigerant temperature increases.

As described above, in the present embodiment, the load reduction operation is started earlier in anticipation of the rising speed ΔT of the refrigerant temperature and the time lag time R. It is possible to prevent the shift to.

FIG. 3 (c1) shows a case where the load is lighter than the case of FIG. 3 (a1). In this case, the rising speed of the refrigerant temperature is lower than in the case of FIG.

In this case as well, if the refrigerant temperature continues to rise, the compressor 1 will eventually be overloaded. In this embodiment, when the load on the compressor 1 is light and the rise in the refrigerant temperature is slow, the rise temperature (K · R · ΔT in the above equation (1)) determined by the microcomputer 10 is calculated as shown in FIG. When the detected temperature To in this case is higher than the detected temperature To in FIG.
Can be predicted to be in an overload condition, and thus, even if the rate of increase in the detected temperature is reduced,
As shown in FIG. 3 (c1), an overload state can be avoided.

On the other hand, in the above conventional air conditioner,
When the rising speed of the refrigerant temperature is the same as that in the case of FIG. 3 (c1), since the operating value is constant as described in FIG. 3 (c2), the operating value in which the refrigerant temperature is fixed is If the load reduction operation is started when the temperature exceeds the threshold, the refrigerant temperature is reduced by the load reduction operation in a state where the refrigerant temperature is lower than the lower limit of the refrigerant temperature in the overload state of the compressor.
For this reason, although there is still room, the load reducing operation is performed, the heating capacity is reduced, and the heating comfort is impaired.

As described above, in this embodiment, the start of the load reduction operation can be delayed until the last minute in consideration of the rising speed ΔT of the refrigerant temperature and the time lag time R, so that the heating capacity can be sufficiently exhibited. The heating comfort is not lost.

Although specific numerical values have been given in the above description, these are merely numerical values, and the present invention is not limited by these numerical values.

[0080]

As described above, according to the present invention,
During the cooling operation, when the pressure after condensation of the discharged refrigerant gas exceeds a predetermined value, the bypass valve opens according to the pressure, so the pressure can be reduced, and the effect on the compressor at high load etc. Can be reduced.

Further, since the liquid refrigerant is vaporized by the bypass valve and the bypass decompressor and then comes to the inlet side of the compressor, liquid compression by the liquid refrigerant can be prevented. Therefore, special means corresponding to the liquid compression is required. You don't have to.

Since the bypass valve opens according to the pressure, detection means such as a pressure sensor is not required.

In the heating operation, the pressure of the bypass valve does not increase, and the bypass valve does not open. Therefore, this bypass valve is a unique load reducing device during the cooling operation.

During the heating operation, the timing for starting the load reduction operation can be optimized according to the degree of the load. When the load is high, the reliability of the compressor is ensured by starting the load reduction operation earlier. When the load is light, unnecessary heating operation is not performed, and a comfortable heating operation can be performed.

Further, almost no additional mechanism or device is required for the conventional air conditioner, and a highly reliable air conditioner can be realized at low cost.

Further, the load reducing devices for the cooling operation and the heating operation are independent of each other, and do not interfere with each other.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a load reduction control operation during a heating operation in the embodiment shown in FIG. 1;

FIG. 3 is a diagram illustrating an effect of a load reduction operation during a heating operation between the embodiment illustrated in FIG. 1 and a conventional air conditioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Outdoor heat exchanger 3 Pressure reducer 4 Indoor heat exchanger 5 Switching valve (four-way valve) 6 Bypass valve 7 Bypass pressure reducer 8 Temperature detection device 9 Control circuit 10 Microcomputer 11 Memory 12a-12c Relay device 13 Indoor blower 14 outdoor blower

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazuhiko Moezuka 709 Tomita, Ohira-cho, Ohira-cho, Shimotsuga-gun, Tochigi 2 Within Hitachi Tochigi Electronics Co., Ltd.

Claims (3)

[Claims] 1. A refrigeration cycle in which an outdoor heat exchanger, a decompressor, and an indoor heat exchanger are arranged in order from at least a compressor via a four-way valve is formed. An air conditioner configured to switch the flow direction of the refrigerant in the air conditioner, wherein a bypass path for the refrigerant is provided in parallel with the decompressor and the indoor heat exchanger, and the bypass path includes the outdoor heat exchanger and the decompressor. By opening at an opening degree according to the refrigerant pressure when the refrigerant pressure between the pressure is equal to or more than a predetermined threshold set according to the overload state of the compressor, the amount of refrigerant according to the opening degree An air conditioner comprising a bypass valve that bypasses the pressure reducer and the indoor heat exchanger. 2. The air conditioner according to claim 1, wherein a bypass decompressor for reducing the pressure of the refrigerant passing through the bypass valve is provided in the bypass passage. 3. The temperature sensor according to claim 1, wherein a temperature of the refrigerant in the indoor heat exchanger is detected, and an overload state of the compressor is detected based on a temperature detected by the temperature detector. And control means for controlling at least one of the compressor, the outdoor blower and the indoor blower to reduce the load on the compressor, the control means comprising: a temperature detected by the temperature detection means; A predicted temperature after a predetermined period of time determined from the temperature change rate is obtained.When the predicted temperature exceeds an overload determination value indicating an overloaded state of the compressor, the compressor is in an overloaded state. An air conditioner characterized by determining that: