JP3495486B2 - 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 for controlling a constant value of superheat amount.

[0002]

2. Description of the Related Art In an air conditioner, the capacity (operating frequency) of a compressor is controlled according to a cooling load or a heating load.
At the same time, the superheat amount SH of the refrigerant is detected, and the opening degree of the electric expansion valve during the refrigeration cycle is controlled so that the superheat amount SH becomes a predetermined constant value.

In an air conditioner, the internal temperature of the compressor may rise excessively during overload operation. So-called overheating. When this overheating occurs, various problems such as the decomposition of the refrigerant, the deterioration of the lubricating oil in the compressor, the deterioration of the insulation performance of the compressor motor, and the like occur.

Therefore, conventionally, the discharge refrigerant temperature of the compressor is detected, and when the discharge refrigerant temperature exceeds a predetermined value, the operating frequency of the compressor is reduced to suppress the rise of the discharge refrigerant temperature and solve the above-mentioned problems. There is something. This is so-called discharge temperature control.

[0005]

In the discharge temperature control for reducing the operating frequency of the compressor, there is a problem that the air conditioning capacity decreases and the comfort is impaired. The present invention takes the above circumstances into consideration, and the air conditioners of the first to fourth inventions include:
An object of the present invention is to prevent overheating of the compressor and improve the life of the compressor without impairing comfort.

In the air conditioner of the fifth to seventh inventions, overheating of the compressor can be prevented and life of the compressor can be improved without impairing comfort, and the superheat amount SH regardless of cooling or heating. Is accurately detected to improve the reliability of superheat amount control.

The air conditioner of the eighth to sixteenth inventions comprises:
The object is to enable stable and smooth transition to superheat amount control while preventing overheating and liquid back at the time of starting the compressor.

[0008]

The air conditioner of the first invention comprises a refrigeration cycle in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and the refrigerant superheat amount SH is constant at a target value SHO. For controlling the opening degree of the electric expansion valve so that the discharge refrigerant temperature Td of the compressor is detected, and detection is performed as the detection temperature Td of the detecting means increases.
And a correction unit that gradually corrects the target value SHO in the decreasing direction according to the temperature Td .

The air conditioner of the second invention comprises a refrigeration cycle in which a compressor having variable capacity, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and the superheat amount SH of the refrigerant is a target value SHO.
In the one that controls the opening degree of the electric expansion valve so as to be constant, a detection unit that detects the discharge refrigerant temperature Td of the compressor,
And a correction unit that corrects the target value SHO according to the detection temperature Td of the detection unit and the operating frequency F of the compressor.

The air conditioner of the third invention comprises a refrigeration cycle in which a compressor, a condenser, an electric expansion valve and an evaporator are sequentially connected, and an electric expansion valve so that the superheat amount SH of the refrigerant becomes a target value SHO constant. In order to control the opening of the compressor, a detecting means for detecting the case temperature Tca of the compressor and a correcting means for correcting the target value SHO according to the detected temperature Tca of the detecting means are provided.

An air conditioner of a fourth invention comprises a refrigeration cycle in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and an electric expansion valve so that the superheat amount SH of the refrigerant becomes a target value SHO constant. For controlling the opening of the compressor, a detecting means for detecting the discharge refrigerant temperature Td of the compressor, a detecting means for detecting the case temperature Tca of the compressor, and a target value according to the detected temperatures Td, Tca of these detecting means. And a correction means for correcting the SHO.

The air conditioner of the fifth invention is equipped with a heat pump type refrigeration cycle in which a compressor, a four-way valve, an outdoor heat exchanger, an electric expansion valve, and an indoor heat exchanger are sequentially connected, and the superheat amount SH of the refrigerant is a target. In the one that controls the opening of the electric expansion valve to keep the value SHO constant, a bypass provided via a throttle device between the liquid side pipe of the refrigeration cycle and the suction side pipe of the compressor, and the low pressure side of this bypass Detecting means for detecting the refrigerant temperature Tu of the refrigerant, second detecting means for detecting the temperature Te of the refrigerant flowing into the outdoor heat exchanger during heating, and third detecting means for detecting the suction refrigerant temperature Ts of the compressor. , The detection temperature Tu of the first detection means and the detection temperature Te of the second detection means
The superheat amount SH based on the selection means for selecting one of the above as the pseudo saturation temperature of the refrigerant, and the pseudo saturation temperature selected by this selection means and the detection temperature Ts of the third detection means.
Detecting means for detecting the discharge refrigerant temperature Td or the case temperature Tca of the compressor, and a correcting means for correcting the target value SHO according to the detected temperature of the detecting means.
Equipped with.

In the air conditioner of the sixth invention, the selecting means of the fifth invention selects the detected temperature Tu as the pseudo saturation temperature when the condition of [(Te-Tu) ≧ predetermined value K] is satisfied. And means for selecting the detected temperature Te as the pseudo saturation temperature when the above conditions are not satisfied.

In the air conditioner of the seventh invention, the selecting means of the fifth invention selects the detection temperature Tu as the pseudo saturation temperature when the condition of [(Te-Tu) ≧ predetermined value K] is satisfied. And means for selecting the detected temperature Te as the pseudo saturation temperature when the above condition is not satisfied and the condition [Te <Tu] is satisfied, and [Te- (T
e-Tu) ² / K] is selected as the pseudo saturation temperature.

The air conditioner of the eighth invention comprises a refrigeration cycle in which a compressor, a condenser, an electric expansion valve and an evaporator are sequentially connected, and the opening degree of the electric expansion valve is set to a predetermined initial value when the compressor is started. Transition control to the opening degree, then the superheat amount of the refrigerant
It controls the opening of the electric expansion valve so that SH is constant at the target value SHO.
Control means is provided to correct the initial opening according to the time elapsed until reaching SH ₁ .

In the air conditioner of the ninth invention, the control means of the eighth invention corrects the initial opening degree in the opening direction by an amount according to the elapsed time. An air conditioner of a tenth invention comprises a refrigeration cycle in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and the opening of the electric expansion valve is set to a predetermined initial opening when the compressor is started. It controls the opening of the electric expansion valve so that the superheat amount SH of the refrigerant becomes constant at the target value SHO, and the transition of the electric expansion valve to the initial opening accompanying startup is performed. the opening, first sets the basic opening corresponding to the operating frequency of the compressor until the superheat amount SH set value SH ₁ beyond setpoint SH ₂ (> SH _1), superheat amount SH set value When SH ₂ is exceeded, the starting opening α that is larger than the basic opening is increased and the state is maintained,
When the superheat amount SH drops to the set value SH _1, the first control means for narrowing the starting opening α to the above initial opening, and the above according to the elapsed time from the start until the superheat amount SH reaches the set value SH ₁ Second control means for correcting the initial opening,
Equipped with.

In the air conditioner of the eleventh invention, the first control means of the tenth invention gradually narrows the opening of the electric expansion valve from the starting opening α to the initial opening by a predetermined value. In the air conditioner of the twelfth aspect of the invention that performs control to proceed to, the first control means of the eleventh aspect of the invention sets the opening degree of the electric expansion valve to the starting opening degree α.
When the superheat amount SH falls to the set value SH ₃ (> SH ₂ ) in the process of gradually reducing from the initial opening to the initial opening, the opening is stopped at that point and the opening is controlled to keep the target value SHO constant. Control to move to.

An air conditioner according to a thirteenth aspect of the present invention is the air conditioner according to any one of the eighth to twelfth aspects of the present invention, wherein a detecting means for detecting the refrigerant discharge temperature Td of the compressor and a temperature Td detected by the detecting means are equal to or more than a predetermined value. Control means for terminating the shift control to the initial opening degree upon startup and shifting to the discharge temperature control for suppressing the rise in the detected temperature Td.

The air conditioner of the fourteenth invention comprises a refrigeration cycle in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and the opening degree of the electric expansion valve is set to a predetermined initial value when the compressor is started. It controls the opening degree of the electric expansion valve so that the superheat amount SH of the refrigerant becomes the target value SHO at a constant value. The opening of the expansion valve is increased to a predetermined starting opening α and is maintained, and when the superheat amount SH drops to a set value SH _1, control means for reducing the starting opening α to the above-mentioned initial opening, and electric expansion After the valve opening is increased to the starting opening α and maintained, if the predetermined amount of time elapses without the superheat amount SH decreasing to the set value SH ₁ , the starting opening α is released and the target value SHO becomes constant. Control means for shifting to the opening degree control for.

An air conditioner of a fifteenth invention is the air conditioner of any one of the tenth, eleventh, twelfth and fourteenth inventions,
When the operation of the compressor is interrupted during the transition control to the initial opening degree upon start-up, the control means for restarting the transition control along with the restart of the operation of the compressor, and the restarting degree α of the startup opening α when the transition control is restarted And a control unit that corrects the value to a value smaller than that in the previous transition control.

The air conditioner of the sixteenth invention is the air conditioner of any one of the tenth, eleventh and twelfth inventions, wherein when the operation of the compressor is interrupted during the control of shifting to the initial opening degree upon start-up, the compression thereof is performed. Control means for restarting the above-mentioned transfer control with restarting of the machine, and control means for correcting the set value SH ₂ to a value larger than that at the previous transfer control when restarting this transfer control,
Equipped with.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, an outdoor heat exchanger 3 is connected to a discharge port of a variable capacity compressor 1 via a four-way valve 2.
Is connected to a pipe, and the indoor heat exchanger 5 is connected to the outdoor heat exchanger 3 via an electric expansion valve (pulse motor valve; PMV) 4. Further, the suction port of the compressor 1 is connected to the indoor heat exchanger 5 via the four-way valve 2 by piping.

That is, during cooling, the flow path of the four-way valve 2 is set to the cooling mode so that the refrigerant flows in the direction of the solid line arrow to form the cooling cycle, and the outdoor heat exchanger 3 is connected to the condenser,
The indoor heat exchanger 5 functions as an evaporator.

During heating, the flow path of the four-way valve 2 is switched to the heating mode to flow the refrigerant in the direction of the dashed arrow to form a heating cycle, and the indoor heat exchanger 5 is changed to the condenser and the outdoor heat exchanger 3 Function as an evaporator.

The bypass 6 is pipe-connected from the liquid side pipe between the outdoor heat exchanger 3 and the electric expansion valve 4 to the suction side pipe of the compressor 1. A capillary tube 7 is provided in the bypass 6 as a diaphragm device.

In the discharge side pipe of the compressor 1, the discharge refrigerant temperature T
A temperature sensor 11 for detecting d is attached. The temperature sensor 12 is attached to the liquid side pipe near the outdoor heat exchanger 3. The temperature sensor 12 detects the temperature Te of the refrigerant flowing into the outdoor heat exchanger 3 during heating, and the outdoor heat exchanger 3
It is used for frost detection. An indoor temperature sensor 13 for detecting the intake air temperature (hereinafter, referred to as indoor temperature) Ta is provided near the indoor heat exchanger 5. A temperature sensor 14 for detecting the suction refrigerant temperature Ts is attached to the suction side pipe of the compressor 1. In the bypass 6, a temperature sensor 15 is attached to the low pressure side pipe downstream of the capillary tube 7. The temperature sensor 15 detects the refrigerant temperature Tu on the low pressure side of the bypass 6. The temperature sensor 16 is attached to the case of the compressor 1. The temperature sensor 16 detects the case temperature Tca of the compressor 1.

The commercial AC power source 20 is provided with an inverter circuit 21.
And the control unit 30 via the step-down transformer 22. The inverter circuit 21 rectifies the power supply voltage, converts the power supply voltage into alternating current having a frequency (and voltage) according to a command from the control unit 30, and outputs the alternating current. This output is supplied to the compressor 1 as drive power. The output frequency of the inverter circuit 21 is
It is referred to as the operating frequency F of the compressor 1.

The control unit 30 includes a four-way valve 2, an electric expansion valve 4,
The temperature sensors 11, 12, 13, 14, 15, the inverter circuit 21, and the light receiving section 31 are connected. Light receiving part 31
Receives infrared light emitted from the remote control type operation device 32. The operation device 32 transmits operating conditions input by a user's key operation to the air conditioner body by infrared light. The operation device 32 will be abbreviated as a remote controller hereinafter.

The control unit 30 has the following (1) to (4) as main functional means. (1) The detection temperature Tu of the temperature sensor 15 is selected as the pseudo saturation temperature of the refrigerant, and the pseudo saturation temperature and the temperature sensor 14 are selected.
A detection means for detecting the superheat amount SH of the refrigerant in the evaporator from the detected temperature Ts.

(2) The detected superheat amount SH is the target value
SHO Superheat amount control means for controlling the opening degree of the electric expansion valve 4 by a predetermined value so as to be constant. (3) Temperature detected by the temperature sensor 11 (discharged refrigerant temperature) Td
Is less than the predetermined value d _3, a correction means for correcting the target value SHO of the superheat amount control according to the detected temperature Td. Specifically, the target value SHO is corrected downward as the detected temperature Td increases. When the superheat amount control follows this correction, the opening degree of the electric expansion valve 4 is increased, and the refrigerant is returned to the compressor 1 in a liquid-backed manner to suppress the overheated state of the refrigeration cycle.

(4) Despite the correction of the target value SHO,
When the detection temperature Td of the temperature sensor 11 rises above a predetermined value d _3, with priority type to superheat amount control, discharge temperature control means to further increase the degree of opening of the electric expansion valve 4 by a predetermined control amount. This control is for surely suppressing overheating.

Next, the operation will be described. During cooling operation,
Refrigerant is caused to flow in the direction of the solid line arrow in FIG. 1 so that the outdoor heat exchanger 3 functions as a condenser and the indoor heat exchanger 5 functions as an evaporator. This cools the room.

During the heating operation, the flow path of the four-way valve 2 is switched to allow the refrigerant to flow in the direction of the broken arrow in FIG. 1 so that the indoor heat exchanger 7 functions as a condenser and the outdoor heat exchanger 5 functions as an evaporator. This heats the room.

During the cooling and heating operation, the remote controller 32
The set indoor temperature by T and the detected temperature T of the indoor temperature sensor 13
The difference from a is obtained as an air conditioning load, and the operating frequency F of the compressor 1 is controlled according to the air conditioning load. By this control,
Allow the room temperature to converge to the set room temperature.

During the cooling and heating operations, part of the refrigerant passing through the liquid side pipe of the refrigeration cycle flows into the bypass 6. The inflowing refrigerant passes through the capillary tube 7 and is guided to the compressor 1 through the suction port. At this time, the temperature Tu of the refrigerant flowing on the low pressure side (downstream side) of the bypass 6 is determined by the temperature sensor 15.
The temperature Ts of the refrigerant sucked into the compressor 1 is detected by the temperature sensor 14. The detection temperature Tu of the temperature sensor 15 corresponds to the pseudo saturation temperature.

The control unit 30 executes the following control at a predetermined control interval (for example, 1 minute). Temperature sensor 1
The difference (= Ts-Tu) between the detected temperature Ts of No. 4 and the detected temperature Tu of the temperature sensor 15 is obtained as the superheat amount SH of the refrigerant. Difference between this superheat amount SH and target value SHO (= SH
-SHO), the opening degree operation amount (driving pulse number) with respect to the current opening degree of the electric expansion valve 4 is obtained. Then, the opening degree of the electric expansion valve 4 is actually operated by the calculated opening operation amount.

By this opening operation, the superheat amount SH is kept constant at the target value SHO regardless of the change in the capacity of the compressor 1, and the refrigeration cycle is stabilized. As for the target value SHO, a normal value "5deg" is set in advance, and the normal value is appropriately corrected according to the detected temperature Td of the temperature sensor 11.
For example, as shown in FIG. 2, set values d ₁ , d ₂ , d ₃
(D ₁ <d ₂ <d ₃ ) is prepared, and when Td <d ₁ , the normal target value SHO (= “5deg”), and in the region of d ₁ <Td ≦ d ₂ , the value is “2deg” lower than the normal target value SHO. , D ₂ <Td ≦ d
_In the area of ₃ , usually use a value that is “4deg” lower than the target value SHO.

The refrigeration cycle becomes overheated and the compressor 1
When the discharge refrigerant temperature Td of No. 1 increases, the target value SHO is first lowered to "3deg" which is "2deg" lower than usual. When the target value SHO decreases, the superheat amount control follows it and the opening degree of the electric expansion valve 4 changes in the increasing direction.
With this increase in the opening degree, the refrigerant is returned to the compressor 1 in a liquid backed manner, and overheating of the refrigeration cycle is suppressed.

If the discharge refrigerant temperature Td continues to rise, the target value SHO is further lowered by "2deg" to "1deg". As a result, the opening degree of the electric expansion valve 4 further changes in the increasing direction, and the effect of suppressing overheating is further enhanced.

As described above, the target value SHO is corrected toward the lower side as the discharge refrigerant temperature Td becomes higher,
Can sufficiently suppress the overheated state of the refrigeration cycle,
The life of the compressor 1 can be improved. Operating frequency F of compressor 1
With respect to the above, the control according to the air conditioning load is continued, so that the original cooling or heating does not continue and the comfort is not impaired.

By the way, although the target value SHO is corrected, overheating may not be suppressed and the discharge refrigerant temperature Td may continue to rise. When the discharge refrigerant temperature Td exceeds the set value d ₃ , the discharge temperature control is executed in the form of giving priority to the superheat amount control. That is, in the discharge temperature control, the opening degree of the electric expansion valve 4 is further increased to return the refrigerant to the compressor 1 in a liquid backed manner, and further increase in the detected temperature Td is reliably suppressed to eliminate overheating.

In shifting to the discharge temperature control,
As a former stage, the gradual opening increase by superheat amount control will continue, so a smooth transition is possible,
Problems such as a large overshoot of the discharged refrigerant temperature Td during the transition can be prevented. This greatly contributes to the stability of the refrigeration cycle.

[First Modification] In the above embodiment, the target value SHO for superheat amount control is corrected according to the discharge refrigerant temperature Td, but it is corrected according to the discharge refrigerant temperature Td and the operating frequency F of the compressor 1. May be.

In this case, the normal target value SHO is assigned as shown in FIG. 3 corresponding to the frequency command value for setting the operating frequency F. For example, the minimum allowable operating frequency F
Normal target value SHO = 10d for the frequency command value "S3" of min
eg. Normal target value S for medium frequency command value "S8"
HO = 5deg. The normal target value SHO = 3deg is assigned to the frequency command value "SF" of the maximum allowable operating frequency Fmax.

Considering that the refrigeration cycle is likely to overheat at a high operating frequency F, the operating frequency F
When the temperature is high, the target value SHO is usually lowered so that it is difficult to overheat in advance. As a result, the rise in the detected temperature Td is reduced and the detected temperature Td
The chance of target value correction (that is, increase in the opening degree of the electric expansion valve 4) according to is reduced, the control fluctuation is eliminated, and the refrigeration cycle is stabilized.

When the refrigerant circulation amount is small in the cooling operation and the suction refrigerant temperature Ts of the compressor 1 is greatly increased due to the influence of the outside air temperature, the detected superheat amount SH changes to a larger value than the actual value and the electric expansion is performed. The opening of the valve 4 may be unnecessarily controlled in the increasing direction. If this state continues, there is a concern that the refrigeration cycle will be stable with a liquid back. However, when the circulation amount is low, that is, when the operating frequency F is low, the opening degree of the electric expansion valve 4 is reduced in advance by setting the normal target value SHO high as described above. Even if the superheat amount SH changes to a value larger than the actual value and the opening degree of the electric expansion valve 4 is controlled in the increasing direction, the opening degree of the electric expansion valve 4 does not increase so much, and thus the stability of the liquid back tendency is avoided. it can.

[Second Modification] The target value SHO for superheat amount control may be corrected according to the case temperature Tca of the compressor 1 detected by the temperature sensor 16 instead of the discharge refrigerant temperature Td.

In this case, as shown in FIG. 4, set values of 40 ° C., 50 ° C. and 60 ° C. are prepared for the case temperature Tca, and Tca <
At 40 ℃, the normal target value SHO = 5deg, and in the range of 40 ℃ <Tca ≤ 50 ℃, "2deg" lower than the normal target value SHO, 50 ℃ <T
In the region of ca ≤ 60 ° C, use a value that is "4deg" lower than the target value SHO.

As described above, by using the case temperature Tca instead of the discharge refrigerant temperature Td, the compressor protection priority control by directly catching the overheat of the compressor 1 is performed. [Third Modification] The target value SHO for superheat amount control may be corrected according to both the discharge refrigerant temperature Td and the case temperature Tca.

In this case, if the discharge refrigerant temperature Td rises, control is started according to the discharge refrigerant temperature Td. If the compressor 1 overheats and the case temperature Tca rises, the case temperature Td increases.
Enter control according to ca.

[Fourth Modification] In the above embodiment, the refrigerant temperature on the outlet side of the bypass 6 (the temperature detected by the temperature sensor 15) Tu.
Was selected as the pseudo saturation temperature of the refrigerant, and the superheat amount SH was detected from it and the suction refrigerant temperature (detection temperature of the temperature sensor 14) Ts, but the temperature sensor 12 for detecting frost near the outdoor heat exchanger 3 was detected. Either one of the detected temperature Te and the outlet side refrigerant temperature Tu is selected as the pseudo saturation temperature of the refrigerant, and by using it and the suction refrigerant temperature Ts, the superheat amount
SH may be detected.

During cooling, the pressure loss becomes large at both ends of the capillary tube 7 in the bypass 6 and the bypass 6
Refrigerant flows into. As a result, the outlet side refrigerant temperature Tu can be effectively used as the pseudo saturation temperature.

However, at the time of heating, the pressure difference between both ends of the capillary tube 7 in the bypass 6 is small, so that it becomes difficult for the refrigerant to flow through the bypass 6 and the outlet side refrigerant temperature T
It is unreasonable to use u as the pseudo saturation temperature.
The appropriate superheat amount SH cannot be detected.

Therefore, it is considered that the detected temperature Tu is used as the pseudo saturation temperature during cooling, and the temperature detected by the temperature sensor 12 (the temperature of the refrigerant flowing into the outdoor heat exchanger 3) Te is used as the pseudo saturation temperature during heating. To be

However, since the detected temperature Te during heating shows a value higher than the actual saturation temperature, the detected temperature Te
Is used as the pseudo saturation temperature, the superheat amount SH
There is a concern that an error may occur in the detection of the above condition, and the opening degree of the electric expansion valve 4 may be excessively narrowed, resulting in a cycle of overheating.

As a countermeasure, as shown in FIG. 5, the compressor 1
Temperature T is lower than 50Hz, detection temperature T
Select e as the pseudo saturation temperature. When the operating frequency F of the compressor 1 is 50 Hz or higher, the detected temperature Tu is selected as the pseudo saturation temperature.

FIG. 6 shows the pressure loss characteristics of the outdoor heat exchanger 3 during heating. Tj is the evaporation temperature of the outdoor heat exchanger 3 and corresponds to the actual saturation temperature, and the temperature difference "Te-
Tj ″ corresponds to the pressure loss in the outdoor heat exchanger 3.
The temperature difference "Te-Tj" increases as the operating frequency F increases, that is, the refrigerant circulation flow rate increases.

As is clear from the characteristics of FIG. 6, even during heating, when the operating frequency F is low, the difference between the detected temperature Te and the actual saturation temperature (= evaporation temperature Tj) is small, so the detected temperature Te is simulated. Superheat amount even when used as saturation temperature
It is possible to detect SH appropriately. In other words, there is no risk of overheating.

Further, it can be seen from the characteristics of FIG. 6 that the pressure loss becomes sufficiently large at a high operating frequency F,
Therefore, the refrigerant sufficiently flows into the bypass 6 even during heating. That is, even during heating, if the operating frequency F is on the high side, the superheat amount SH can be appropriately detected by using the detected temperature Tu as the pseudo saturation temperature.

Thus, the detected temperature Tu,
By selecting one of Te and using it as the pseudo saturation temperature to detect the superheat amount SH, an appropriate superheat amount SH can always be captured, and reliable superheat amount control becomes possible.

[Fifth Modification] In the fourth modification, one of the detected temperatures Te and Tu is selected according to the operating frequency F. However, the temperature difference "Te-Tj" of the characteristic shown in FIG. 6 is the temperature difference. Paying attention to the similar relationship with (= Te-Tu), the detected temperature T depends on the magnitude of the temperature difference (= Te-Tu).
Either e or Tu may be selected.

That is, [(Te-Tu) ≧ predetermined value K]
When the condition of is satisfied (when the operating frequency F is high and the refrigerant circulation amount is large), the detected temperature Te is too high than the actual saturation temperature, and it is judged that the use of the detected temperature Te is not preferable. One of the detected temperatures Tu is selected as the pseudo saturation temperature, and the superheat amount SH is detected. of course,
Even during heating, the refrigerant is sufficiently flowing into the bypass 6, and the detected temperature Tu as the pseudo saturation temperature can be used sufficiently.

The predetermined value K is, for example, "1 deg". When the above conditions are not satisfied, that is, [(Te-Tu) <
When the detected temperature Te is close to the actual saturation temperature and the detected temperature Te can be used when the predetermined value K], the detected temperature Te is selected as the pseudo saturation temperature and the superheat amount is selected. Detect SH.

[Sixth Modification] In the fifth modification, the detected temperature Te is selected as the pseudo saturation temperature when the condition is not satisfied, that is, [(Te-Tu) <predetermined value K]. If the detected temperature Tu is closer, an error will occur in the detection of the superheat amount SH by the temperature difference (= Te-Tu). This error appears as a step in superheat amount control.

As a countermeasure, when the condition is not satisfied, [Te-
(Te−Tu) ² / K] is calculated, and the calculated value is used as the pseudo saturation temperature to detect the superheat amount SH. Thereby, there is no step between the superheat amount control based on the selection of the detected temperature Tu when the condition is satisfied and the superheat amount control based on the selection of the detected temperature Te when the condition is not satisfied, and smooth superheat amount control is possible. The stability of the refrigeration cycle is improved.

Even when the condition is not satisfied, [Te <
In the case of [Tu], the detected temperature Te is sufficiently close to the actual saturation temperature, and if it is determined that there is no concern about detection error, the detected temperature Te is pseudo saturated as it is instead of the calculated value. Select as temperature. The processing time becomes faster because there is no calculation.

[Startup Control in One Embodiment] (1) By the way, in the above embodiment, when the compressor 1 is started, the electric expansion valve 4 is operated before the superheat amount control corresponding to the superheat amount SH and the target value SHO. The startup control is performed to shift the opening of to a predetermined initial opening PLS. This start-up control deals with the phenomenon that the superheat amount SH temporarily increases greatly when the compressor 1 is started, and is aimed at a smooth transition to the superheat amount control.

That is, the change in the superheat amount SH is shown in FIG. 7 as an SH curve, and in order to cope with the change,
First, the opening degree of the electric expansion valve 4 is set to the starting opening α, and the state is maintained (at least m minutes, for example, 2 minutes). When the superheat amount SH drops to the set value SH ₁ , the starting opening α is initially set. Open to PLS. Electric expansion valve 4
When the opening of reaches the initial opening PLS, it shifts to superheat amount control.

The starting opening α is larger than the basic opening corresponding to the operating frequency F of the compressor 1, and for example, the driving pulse number 3
The opening is equivalent to 80 shots. The initial opening PLS is a value determined for the time being and corresponds to, for example, 180 drive pulses. The basic opening corresponds to, for example, 150 driving pulses. The setting value SH ₁ is “3deg”.

After the start-up, the elapsed time n until the superheat amount SH reaches the set value SH ₁ is counted, and the initial opening PLS is corrected in the opening direction by an amount corresponding to the elapsed time n.
In the case of SH curve A, the superheat amount SH from the start is the set value SH
The elapsed time n to reach ₁ is 2 minutes, and the initial opening PLS
Set the initial opening PLS as is as the correction value PLS _n . In the case of the SH curve B, the elapsed time n from the start-up until the superheat amount SH reaches the set value SH ₁ is about 4 minutes and a half, and PLS _b is set as the correction value PLS _n for the initial opening PLS.

In the case of SH curve C, the amount of superheat from the start
SH is the elapsed time n is about 7 minutes and a half up to the set value SH _1, sets the PLS _b greater PLS _c as the correction value PLS _n of initial opening PLS. In the case of SH curve D, the elapsed time n from startup to when the superheat amount SH reaches the set value SH ₁ is about 1
0 minutes, it sets the PLS _c greater PLS _d as a correction value PLS _n of initial opening PLS. In the example of the SH curve E, the superheat amount SH does not reach the set value SH ₁ and the upper limit value of 12 minutes has elapsed from the startup, and the startup opening α is set as the correction value PLS _n of the initial opening PLS.

The corrected initial opening PLS _n is calculated by the following equation. PLS _n = PLS + (α-PLS) / (12 min-m) ・ (n-
m) The long elapsed time from when the superheat amount SH increases to when it completely falls means that the refrigeration cycle is in a state of overheating, so it seems that overheating will be eliminated immediately after entering the superheat amount control. , The initial opening PLS is set large in advance. When actually entering the superheat amount control, the operation amount of the opening degree to the electric expansion valve 4 can be small and the refrigeration cycle can be stabilized early.

The electric expansion valve 4 is a factor that determines the elapsed time from when the superheat amount SH increases to when it completely falls.
In addition to the opening degree, there are a pipe length, a refrigerant filling amount, an operation stop time (corresponding to the refrigerant stagnation amount), and the like, and it is possible to always maintain a stable operating state while absorbing these factors.

In the example of the SH curve E in which the upper limit value of 12 minutes elapses without the superheat amount SH decreasing to the set value SH ₁ , the holding of the starting opening α is released and the control immediately shifts to the superheat amount control.

(2) In the process of narrowing the opening of the electric expansion valve 4 from the starting opening α to the initial opening correction value PLS _n , the opening is gradually advanced by a predetermined value (for example, 15 pulses / second). As a result, the superheat amount SH can reach the initial opening correction value PLS _n without overshooting, and a smooth transition to the superheat amount control is possible.

[Modification of Startup Control] (1) When the compressor 1 is started, as shown in FIG. 8, the opening degree of the electric expansion valve 4 is first set so that the superheat amount SH exceeds the set value SH _1. Set the basic opening corresponding to the operating frequency of the compressor 1 up to the value SH ₂ (> SH ₁ ) and set the superheat amount SH
Is greater than the set value SH ₂ , the starting opening α that is larger than the basic opening α
To the initial value when the superheat amount SH drops to the set value SH ₁
Focus on PLS. The setting value SH ₂ is “4deg”.

After the start, the elapsed time until the superheat amount SH reaches the set value SH ₁ is counted, and the initial opening PLS is corrected in the opening direction by an amount according to the elapsed time. Whether or not the superheat amount SH exceeds the set value SH ₂ is a criterion for determining whether or not the subsequent superheat amount SH continues to rise. That is, when the superheat amount SH exceeds the set value SH ₂ , the opening degree is increased to the starting opening α for the first time under the prediction that the superheat amount SH continues to further increase.

In the control shown in FIG. 7, the opening degree of the electric expansion valve 4 is set to the starting opening degree α at the same time as the start-up. However, depending on the situation, there is a concern that the cycle becomes liquid back-like and that it continues. is there.

Therefore, only when it is predicted that the superheat amount SH continues to increase, the opening degree of the electric expansion valve 4 is set to the starting opening degree α.
I am trying to increase. Thereby, liquid back can be avoided and the life of the compressor 1 can be improved.

FIG. 9 shows a process in which the opening degree of the electric expansion valve 4 is gradually reduced from the starting opening degree α to the initial opening degree correction value PLS _n . (2) In the process of gradually narrowing the opening of the electric expansion valve 4 from the starting opening α to the initial opening correction value PLS _n , as shown in FIG. 9, the superheat amount SH is set to a set value SH ₃ (> SH ₂ ). When the temperature is lowered to, the throttle of the opening is finished at that point, and the superheat amount control is started. The set value SH ₂ is “5deg”.

The superheat amount SH is the set value SH ₃ (> SH ₂ )
Whether or not it has fallen to is a criterion for determining whether or not the degree of opening at the time of shifting to the superheat amount control becomes too narrow. That is, the superheat amount SH is the set value SH ₃
If it is lowered to (> SH ₂ ), the throttle will be stopped and the superheat amount will be terminated with the prediction that the opening will be too narrow when the control shifts to superheat amount control, resulting in insufficient refrigerant flow. To move to.

(3) When the temperature detected by the temperature sensor 11 (the temperature of the refrigerant discharged from the compressor 1) Td rises above a predetermined value during the startup control, the transition control to the initial opening correction value PLS _n associated with the startup is performed. After that, the discharge temperature control for suppressing the increase of the detection temperature Td is started.

That is, the abnormal rise in the refrigerant discharge temperature Td is preferentially suppressed to prevent overheating. (4) When the upper limit value of 12 minutes elapses without the superheat amount SH decreasing to the set value SH ₁ , the holding of the starting opening α is released and the process immediately shifts to the superheat amount control. This example is shown in FIG.

(5) When the operation of the compressor 1 is interrupted during the start control (that is, within 12 minutes) based on the indoor temperature control, that is, when the thermostat is turned off, the start control (initial opening degree) is performed when the operation of the compressor 1 is restarted, that is, the thermostat is turned on. Restart control of shift to correction value PLS _n ). At the time of this restart, the starting opening α is corrected to a value smaller than that at the previous starting control.

The correction of the starting opening α aims to reduce the liquid back amount due to the intermittent operation in a short time,
It is for protecting the compressor 1. (6) During start-up control (that is, within 12 minutes), when the compressor 1 stops operation based on indoor temperature control, so-called thermo-off,
The operation control of the compressor 1 is restarted, so that the start-up control (control to shift to the initial opening correction value PLS _n ) is restarted with the so-called thermo-on. At this restart, the set value SH ₂ is corrected to a value larger than that at the previous startup control.

The correction of the set value SH ₂ is for prolonging the time during which the opening degree at the time of restart is kept smaller than the starting opening degree α. Has the effect of protecting the compressor 1 by reducing The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

[0087]

As described above, according to the present invention, the air conditioner of the first to fourth inventions corrects the target value SHO of the superheat amount control according to the refrigerant temperature discharged from the compressor. Therefore, overheating of the compressor can be prevented and the life of the compressor can be improved without impairing comfort.

In the air conditioner of the fifth to seventh inventions, since the pseudo saturation temperature is properly captured, overheating of the compressor can be prevented and the life of the compressor can be improved without impairing comfort. At the same time, the superheat amount SH can be accurately detected regardless of whether it is cooling or heating, and the reliability of the superheat amount control can be improved.

The air conditioners of the eighth to sixteenth inventions are:
Since the initial opening of the electric expansion valve is corrected according to the state of the refrigeration cycle, stable and smooth transition to superheat amount control is possible while preventing overheating and liquid back at the time of starting the compressor.

[Brief description of drawings]

FIG. 1 is a diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a target value SH according to a discharge refrigerant temperature Td of the embodiment.
The figure which shows the correction conditions of O.

FIG. 3 is a diagram showing a correspondence between a frequency command value and a normal target value SHO in a first modified example of the same embodiment.

FIG. 4 is a case temperature Tca in a second modification of the embodiment.
The figure which shows the correction conditions of the target value SHO according to.

FIG. 5 is a diagram for explaining superheat amount detection according to an operating frequency F in a fourth modified example of the same embodiment.

FIG. 6 is a diagram showing a pressure loss characteristic of the outdoor heat exchanger during heating in the fourth modification of the embodiment.

FIG. 7 is a diagram showing a change in superheat amount during start-up control in the same embodiment.

FIG. 8 is a diagram showing changes in the superheat amount SH in a modification of the startup control of the same embodiment.

FIG. 9 is a diagram showing another example of changes in the superheat amount SH in a modification of the startup control of the same embodiment.

FIG. 10 is a diagram showing yet another example of changes in the superheat amount SH in a modification of the startup control of the same embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Four-way valve, 3 ... Outdoor heat exchanger, 4 ... Electric expansion valve, 5 ... Indoor heat exchanger, 6 ... Bypass, 7 ... Capillary tube (throttle device), 11, 12, 14, 15 …
Temperature sensor, 13 ... Indoor temperature sensor, 21 ... Inverter circuit, 30 ... Control section.

Claims (16)

(57) [Claims] 1. An air conditioner that comprises a refrigeration cycle in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and controls the opening of the electric expansion valve so that the superheat amount SH of the refrigerant becomes a target value SHO constant. A detector for detecting a refrigerant discharge temperature Td of the compressor,
The higher the detection temperature Td of the detection means, the higher the detection temperature T
An air conditioner comprising: a correction unit that gradually corrects the target value SHO in a decreasing direction according to d . 2. A refrigeration cycle in which a variable capacity compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and the opening of the electric expansion valve is controlled so that the superheat amount SH of the refrigerant becomes a target value SHO. In the air conditioner, detecting means for detecting the refrigerant discharge temperature Td of the compressor,
Correction means for correcting the target value SHO according to the detected temperature Td of the detection means and the operating frequency F of the compressor;
An air conditioner characterized by having. 3. An air conditioner that comprises a refrigeration cycle in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and controls the opening of the electric expansion valve so that the superheat amount SH of the refrigerant becomes a target value SHO. An air conditioner, comprising: a detector that detects a case temperature Tca of the compressor; and a corrector that corrects the target value SHO according to the detected temperature Tca of the detector. 4. An air conditioner comprising a refrigeration cycle in which a compressor, a condenser, an electric expansion valve and an evaporator are sequentially connected, and which controls the opening of the electric expansion valve so that the superheat amount SH of the refrigerant becomes a target value SHO. A detector for detecting a refrigerant discharge temperature Td of the compressor,
Detecting means for detecting the case temperature Tca of the compressor, and the target value according to the detected temperatures Td, Tca of these detecting means.
An air conditioner characterized by comprising a correction means for correcting SHO. 5. A heat pump type refrigeration cycle in which a compressor, a four-way valve, an outdoor heat exchanger, an electric expansion valve, and an indoor heat exchanger are sequentially connected, and the superheat amount SH of the refrigerant is a target value SHO.
In an air conditioner that controls the opening of an electric expansion valve so as to be constant, a bypass provided via a throttle device between the liquid side pipe of the refrigeration cycle and the suction side pipe of the compressor, and a low pressure of this bypass. Side detecting means for detecting the side refrigerant temperature Tu, second detecting means for detecting the temperature Te of the refrigerant flowing into the outdoor heat exchanger during heating, and the suction refrigerant temperature Ts of the compressor.
And a selection means for selecting one of the detection temperature Tu of the first detection means and the detection temperature Te of the second detection means as the pseudo saturation temperature of the refrigerant, and the selection means. Detecting means for detecting the superheat amount SH from the pseudo saturation temperature and the detected temperature Ts of the third detecting means, detecting means for detecting the discharge refrigerant temperature Td of the compressor or the case temperature Tca, and the detecting means of this detecting means. Correction means for correcting the target value SHO according to the detected temperature,
An air conditioner characterized by having. 6. The air conditioner according to claim 5, wherein the selecting means selects the detected temperature Tu as a pseudo saturation temperature when the condition of [(Te−Tu) ≧ predetermined value K] is satisfied, Means for selecting the detected temperature Te as the pseudo saturation temperature when the above conditions are not satisfied, the air conditioner. 7. The air conditioner according to claim 5, wherein the selecting means selects the detected temperature Tu as the pseudo saturation temperature when the condition of [(Te-Tu) ≧ predetermined value K] is satisfied, Means for selecting the detected temperature Te as the pseudo saturation temperature when the above condition is not satisfied and the condition [Te <Tu] is satisfied, and [Te- (T
e-Tu) ² / K] is selected as a pseudo saturation temperature, and an air conditioner. 8. A refrigeration cycle in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and the opening of the electric expansion valve is controlled to shift to a predetermined initial opening when the compressor is started, After that, in the air conditioner that controls the opening of the electric expansion valve so that the refrigerant superheat amount SH becomes the target value SHO, in the air conditioner, depending on the elapsed time from startup until the superheat amount SH reaches the set value SH _1. Control means for correcting the initial opening,
An air conditioner characterized by having. 9. The air conditioner according to claim 8, wherein the control means includes means for correcting the initial opening degree in the opening direction by an amount according to the elapsed time. 10. A refrigeration cycle in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and the opening of the electric expansion valve is controlled to shift to a predetermined initial opening when the compressor is started,
After that, in the air conditioner that controls the opening degree of the electric expansion valve so that the superheat amount SH of the refrigerant becomes the target value SHO, in the transition to the initial opening degree due to start-up, the opening degree of the electric expansion valve is changed to First, the superheat amount SH is the set value SH ₁
The basic opening corresponding to the operating frequency of the compressor is set until the set value SH ₂ (> SH ₁ ) is exceeded, and when the superheat amount SH exceeds the set value SH ₂ , the start opening larger than the basic opening is set. The first control means for reducing the starting opening α to the initial opening when the superheat amount SH decreases to the set value SH ₁ and the superheat amount SH from the start are increased. Second control means for correcting the initial opening according to the elapsed time until reaching the set value SH ₁ .
An air conditioner characterized by having. 11. The air conditioner according to claim 10, wherein the first control means gradually advances the throttle by a predetermined value in the process of reducing the opening of the electric expansion valve from the starting opening α to the initial opening. An air conditioner characterized by that. 12. The air conditioner according to claim 11, wherein the first control means gradually reduces the opening degree of the electric expansion valve from the starting opening degree α to the initial opening degree, and the superheat amount SH is set to a set value.
An air conditioner characterized in that when it has descended to SH ₃ (> SH ₂ ), the throttle of the opening is terminated at that point, and the operation proceeds to opening control for maintaining the target value SHO constant. 13. The air conditioner according to claim 8, further comprising a detection unit that detects a discharge refrigerant temperature Td of the compressor.
When the detection temperature Td of the detection means rises to a predetermined value or more, the control means for ending the transition control to the initial opening degree upon start-up and shifting to the discharge temperature control for suppressing the rise of the detection temperature Td. An air conditioner characterized by being equipped. 14. A refrigeration cycle in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, and the opening of the electric expansion valve is controlled to shift to a predetermined initial opening when the compressor is started,
After that, in the air conditioner that controls the opening degree of the electric expansion valve so that the superheat amount SH of the refrigerant becomes the target value SHO, in the transition to the initial opening degree due to start-up, the opening degree of the electric expansion valve is changed to A control means for increasing and maintaining a predetermined starting opening α, and narrowing down from the starting opening α to the initial opening when the superheat amount SH decreases to a set value SH ₁ .
After increasing the opening degree of the electric expansion valve to the starting opening degree α and holding it, when the predetermined time elapses without decreasing the superheat amount SH to the set value SH ₁ , the holding of the starting opening degree α is released. And a control unit that shifts to an opening degree control for maintaining the target value SHO constant, the air conditioner. 15. The method according to claim 10, claim 11, and claim 12.
15. The air conditioner according to claim 14, wherein when the operation of the compressor is interrupted during the transition control to the initial opening degree upon start-up, the transition control is restarted with the restart of the operation of the compressor. Control means to perform and when restarting this transition control,
An air conditioner comprising: a control unit that corrects the starting opening α to a value smaller than that at the time of the previous transition control. 16. The air conditioner according to any one of claims 10, 11, and 12, when the operation of the compressor is interrupted during transition control to the initial opening upon start-up, Control means for restarting the transfer control with restart of the compressor, and when restarting the transfer control,
An air conditioner comprising: a control unit that corrects the set value SH ₂ to a value larger than that at the time of the previous transition control.