JP2001116372A - Refrigerating cycle controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an abnormal rise of an evaporator temperature by preventing hunting of an expansion unit at a low load time and continuing a closed state of the unit. SOLUTION: The refrigerating cycle controller comprises a valve operation delay means for delaying a valve operation of an expansion unit 5 to be controlled by a valve opening control means as compared with a larger cooling load than a predetermined value when a cooling load is the value or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a refrigeration cycle in which, for example, carbon dioxide is used as a refrigerant and the refrigerant is compressed to a supercritical region at a high load.

[0002]

2. Description of the Related Art A refrigeration cycle disclosed in Japanese Patent Publication No. Hei 7-18602 discloses a compressor connected in series so as to form an integrated closed circuit operated at supercritical pressure on the high pressure side of a vapor compression cycle. A supercritical vapor compression cycle comprising a cooling device, a throttle device, an evaporator and an accumulator is disclosed.

[0003] In this refrigeration cycle, the gas-phase refrigerant sucked into the compressor is compressed to a supercritical region, discharged and cooled by the cooling device. Instead, it is sent to the throttle means in a gaseous state. Then, the pressure is reduced to the gas-liquid mixing region by the throttle means to generate a liquid phase component, and the refrigerant in the gas-liquid two-phase state absorbs the heat of the air passing through the evaporator and evaporates, and further accumulates. The liquid phase component is completely removed and is sucked into the compressor.

In the above-mentioned refrigeration cycle, as a method of adjusting the opening degree of the throttle means, there is a method depending on the high pressure and temperature of the refrigeration cycle. Japanese Patent Application Laid-Open No. Hei 9 (1998) -129, discloses a method in which a high-pressure pressure at which a high coefficient of performance can be obtained is used as a reference, and the throttle means is controlled so that the high-pressure pressure matches the high pressure.
It is known from -264622.

[0005] As the compressor, those capable of changing the compression and discharge capacity of the refrigerant are widely used, such as those disclosed in Japanese Patent Application Laid-Open No. 05-202849. Such a change in the capacity of the compressor often depends on the suction pressure of the compressor, that is, the low pressure of the refrigeration cycle, and when the refrigerant pressure on the low pressure side decreases at a low load, the capacity of the compressor decreases. Then, the operation is performed so that the refrigerant discharge amount is reduced.

[0006]

However, in the conventional refrigeration cycle using carbon dioxide as described above, when the outside air temperature is low and the load is reduced, the high pressure of the refrigeration cycle becomes lower than the critical pressure. A phenomenon occurs in which the refrigerant condenses in the vessel (gas cooler). For this reason,
When the high pressure decreases, the expansion device (throttle means) that senses this closes and stops the flow of the refrigerant to the low pressure side, so that the pressure on the low pressure side decreases. As a result, the compressor senses the decrease in the low-pressure pressure and reduces the refrigerant discharge amount, so that the high-pressure pressure does not rise sufficiently and the expansion device does not easily open. And
Even if the high pressure finally rises to a predetermined value and the expansion device is opened, the refrigerant rapidly flows from the high pressure line to the low pressure line, causing a hunting phenomenon in which the high pressure decreases and the expansion device closes immediately. . For this reason, since the amount of refrigerant flowing into the evaporator is drastically reduced, the temperature of the evaporator rises abnormally, and the temperature of the blowout of the evaporator rises. There is.

Accordingly, the present invention provides a refrigeration cycle control device that can prevent hunting of an expansion device at a low load and prevent an abnormal increase in evaporator temperature due to the expansion device continuing to be closed. The purpose is to do.

[0008]

In order to solve the above-mentioned problems, the present invention provides a compressor for compressing and discharging a refrigerant, a radiator for cooling the refrigerant compressed by the compressor, and a control signal. An expansion device having an adjustable valve opening degree, and a refrigerating cycle constituted by at least an evaporator for evaporating the refrigerant expanded by the expansion device, wherein an environmental factor detecting means for detecting an environmental factor of the refrigerating cycle; A cooling load calculating unit that calculates a cooling load from the environmental factor detected by the environmental factor detecting unit; a refrigerant pressure detecting unit that detects a pressure of the refrigerant flowing into the expansion device; and a temperature of the refrigerant flowing into the expansion device. A refrigerant temperature detecting means for detecting, and a target pressure for calculating a target pressure of the refrigerant flowing into the expansion device from the refrigerant temperature detected by the refrigerant temperature detecting means. The control means outputs a control signal so that the actual refrigerant pressure detected by the refrigerant pressure detecting means matches the target pressure calculated by the target pressure calculating means, and controls the valve opening of the expansion device. The valve opening control device is controlled by the valve opening control means when the cooling load calculated by the cooling load calculation means is equal to or less than a predetermined value, compared to when the cooling load is larger than a predetermined value. A valve operation delay means for delaying the valve operation of the expansion device is provided (claim 1).

According to this, when the cooling load is reduced due to a decrease in the outside air temperature or the like and the pressure in the high pressure line from the compressor to the expansion device is reduced, the valve opening control means expands the pressure to increase the high pressure. Attempts to reduce the valve opening of the device, but at this time the valve closing speed is slower than when the cooling load is high, so it takes time until the valve of the expansion device closes and secures the refrigerant flowing to the evaporator. As a result, a decrease in the low pressure can be suppressed, so that hunting of the expansion device can be prevented and an abnormal rise in the evaporator temperature can be prevented.

[0010] The environmental factor detecting means for determining the cooling load by the cooling load calculating means includes, for example, an outside air temperature sensor for detecting the outside air temperature, an inside air temperature sensor for detecting the temperature of indoor (in-vehicle) air, and an evaporator. An evaporator inlet temperature sensor that detects the temperature of the air at the inlet, an evaporator refrigerant temperature sensor that detects the temperature of the refrigerant flowing inside the evaporator, and a fan speed that detects the rotational speed of the fan that sends cool air generated by the evaporator into the room Sensors and the like can be used.

Further, it is preferable that the valve operation delay means makes the valve operation in the opening direction faster than the valve operation in the closing direction.

[0012] According to this, since the recovery of the flow of the refrigerant at the time of a low load can be accelerated, a decrease in the low pressure can be prevented, and an abnormal rise in the evaporator temperature can be more effectively prevented. .

The valve operation delay means changes a constant of a formula for calculating a control signal output by the valve opening control means when the cooling load calculated by the cooling load calculation means is equal to or less than a predetermined value. Thereby, the valve operation may be delayed (claim 3).

In the control of the electric expansion device, it is possible to calculate the stroke (movement) amount of the valve by using various arithmetic expressions. A formula for calculating the stroke amount by multiplying the obtained constant is used. Therefore, as in the above-described configuration, the valve operation delay unit changes the constant in the equation for calculating the stroke amount so that the valve operation is delayed at a low load, that is, the stroke amount is reduced so as to reduce the stroke amount. It is possible to prevent hunting of the expansion device under load and abnormal rise of the evaporator temperature.

In controlling the electric expansion device, a feedback control for referring to a deviation between a target output value and an actual output value is often used to calculate an output value.
PID control combining control, integral (I) control, and differential (D) control is effective. In the PID control, for example, as shown in FIG. 9, a proportional component, an integral component, and a differential component are calculated using a deviation ΔP between the target pressure Pa and the actual pressure P,
This is performed by calculating the stroke amount of the valve section from these components. The proportional component operation element 30, the integral component operation element 31, and the differential component operation element 32 in FIG. 9 include a proportional constant Kp, an integral constant Ki, and a differential constant Kd, respectively. For example, these Kp, By changing Ki and Kd according to the cooling load, the valve operation of the expansion device can be slowed down at a low load.

The valve operation delay means may include a sampling interval of the refrigerant pressure and the refrigerant temperature by the refrigerant pressure detecting means and the refrigerant temperature detecting means when the cooling load calculated by the cooling load calculating means is equal to or less than a predetermined value. May be lengthened (claim 4).

With this configuration, the calculation of the target pressure is delayed at a low load compared to the normal operation, so that the valve operation of the expansion device can be delayed.

When the cooling load calculated by the cooling load calculating means is equal to or less than a predetermined value, a lower limit opening setting means for changing the lower limit of the valve opening so that the valve opening does not become zero is provided. It is desirable to have it (claim 5).

According to this, when the cooling load is low,
Since the valve opening is not fully closed, the refrigerant can always be supplied to the low-pressure side, so that hunting of the expansion device can be prevented and an abnormal rise in the evaporator temperature can be prevented. Further, by increasing the minimum valve opening as the cooling load decreases, the valve opening of the expansion device can be adjusted at a level corresponding to the cooling load.

Further, when the cooling load calculated by the cooling load calculating means is equal to or less than a predetermined value, an upper limit opening setting means for setting the upper limit of the valve opening smaller than when the cooling load is larger than the predetermined value. It is desirable to have it (claim 6).

If the valve opening range of the expansion device is large at a low load, the flow rate of the refrigerant suddenly increases at the maximum opening, and the refrigerant flows rapidly from the high pressure line to the low pressure line. Hunting of the expansion device is more likely to occur. Therefore, as described above, the reduction of the high-pressure pressure can be suppressed by making the maximum valve opening at the time of low load smaller than at the time of high load, so that the hunting of the expansion device can be more reliably prevented.

The refrigerant used in the refrigeration cycle is carbon dioxide (claim 7), and the predetermined value is desirably a value at which the refrigerant is below the critical point (claim 8).

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

A refrigeration cycle 1 shown in FIG. 1 uses carbon dioxide as a refrigerant, and a compressor 2, a radiator (gas cooler) 3, an internal heat exchanger 4, an expansion device 5, an evaporator 6, and an accumulator 7 are connected by piping. A high-pressure line 11 from a discharge port 2a of the compressor 2 to an inlet 5a of the expansion device 5, and a low-pressure line from an outlet 5b of the expansion device 5 to a suction port 2b of the compressor 2. And 12.

With the above configuration, the gas-phase refrigerant sucked by the compressor 2 is compressed in the supercritical region during normal operation,
The compressed gas-phase refrigerant is cooled by heat exchange with the air passing through the radiator 3. The gas-phase refrigerant cooled by the radiator 3 flows into the high-pressure side flow path 4a of the internal heat exchanger 4, exchanges heat with the low-temperature low-pressure refrigerant flowing through the low-pressure side flow path 4b, and is further cooled. The pressure is reduced to the gas-liquid mixing area through the expansion device 5. The gas-liquid mixed refrigerant decompressed by the expansion means 5 evaporates by removing the heat of the air passing therethrough in the evaporator 6 and is gas-liquid separated in the accumulator 7. The refrigerant flows into the side flow path 4b, exchanges heat with the high-temperature and high-pressure refrigerant flowing through the high-pressure side flow path 4a, and is sucked by the compressor 2.

The compressor 2 has a known capacity changing mechanism for changing the compression and discharge capacity of the refrigerant in accordance with the pressure of the low pressure line 12, and the structure thereof will not be described in detail. This capacity variable mechanism reduces the amount of compression and discharge when the low-pressure pressure becomes low, for example, at low load.

The expansion device 5 is constituted by an electromagnetic coil to which a control signal is supplied and a valve portion which opens and closes by an electromagnetic force generated in the electromagnetic coil. Driven up to. The throttle amount of the passing refrigerant is determined by the opening degree of the valve section, and the amount and pressure of the refrigerant supplied to the evaporator 8 are determined.

The refrigeration cycle 1 includes an expansion device 5
And a refrigerant temperature sensor 16 for detecting a refrigerant temperature Texpin on the inflow side of the expansion device 5 and an outdoor temperature Tout.
And an indoor temperature sensor 18 for detecting the indoor temperature Tin.

Further, the refrigeration cycle 1 includes the refrigerant pressure sensor 15, the refrigerant temperature sensor 16, and the outdoor temperature sensor 1.
7. A control unit (C / U) 8 including a CPU, a ROM, a RAM, etc., which receives detection signals from the indoor temperature sensor 18 and outputs control signals to the expansion device 5 based on these detection signals. Is provided. This C / U
8, as shown in FIG. 2, cooling load calculating means 20, target pressure calculating means 21, valve opening control means 22, valve operation delaying means 23, lower limit opening setting means 24, upper limit opening setting means 25
Is provided.

The cooling load calculating means 20 calculates the cooling load CL based on the outdoor temperature Tout and the indoor temperature Tin detected by the outdoor temperature sensor 17 and the indoor temperature sensor 18, for example, CL = K · F (Tout, Tin) + C
(K and C are constants) and are determined by numerical expression.
The target pressure calculating means 21 is provided with the refrigerant temperature sensor 16.
Temperature Texpin at the inlet of expansion device 5 detected by
, The refrigerant temperature Texpi as shown in FIG.
The target pressure Pa is obtained from a graph map showing the relationship between n and the target pressure Pa at which the optimum coefficient of performance is obtained at this temperature.
Ask for.

The valve opening control means 22 calculates the target pressure Pa obtained by the target pressure calculating means and the actual refrigerant pressure (actual pressure) Pexpin at the inlet of the expansion device 5 detected by the refrigerant pressure sensor 15. Compare the actual pressure Pex
A control signal for moving the valve portion of the expansion device 5 so that the pin approaches the target pressure Pa is output to the electromagnetic coil of the expansion device 5. In order to calculate the stroke (movement) amount S of the valve portion, for example, PI
D control is performed. In Equation 1, ΔP is the target pressure Pa
And the actual pressure Pexpin (ΔP = Pa−Pexpin), where Kp is a proportional constant, Ki is an integral constant, and Kd is a differential constant.

[0032]

(Equation 1)

In the first embodiment, the valve operation delay means 23 is provided in accordance with the cooling load CL obtained by the cooling load calculation means 20 and the valve opening control means 2.
The proportional constant Kp, the integral constant Ki, and the differential constant Kd are changed depending on whether the control signal outputted from the control signal 2 is a signal for closing the valve or a signal for opening the valve. For example, these constants Kp, Ki, Kd are calculated as follows: Kp = K1 · L, Ki = K2 ·
L, Kd = K3 · L (K1, K2, K3 are constants, L is a variable), and the cooling load CL is less than a predetermined value CL0;
When the valve of the expansion device 5 operates in the closing direction, the stroke amount S can be set small by setting the variable L in the range of 0 <L <1.

When the cooling load CL is larger than a predetermined value CL0 or when the valve of the expansion device 5 operates in the opening direction, the normal speed is set by setting the variable L in the range of L ≧ 1. Now, or faster than usual, the valve can be operated. Also, if the predetermined value CL0 is set to a cooling load such that the carbon dioxide of the refrigerant is below the critical point, the refrigerant condenses in the radiator 3 and the high pressure line 1
When the pressure of No. 1 stops increasing, the delay of the valve operation as described above can be started.

The lower limit opening setting means 24 opens the valve of the expansion device 5 in accordance with the cooling load CL obtained by the cooling load calculating means 20, for example, based on the line segment L1 of the graph map shown in FIG. The lower limit value θlow is set, and a control signal for preventing the valve portion of the expansion device 5 from falling below the lower limit value θlow is output. The upper limit opening setting means 2
5 is an upper limit value θup of the valve opening of the expansion device 5 according to the cooling load CL obtained by the cooling load calculating means 20, for example, based on the line segment L2 of the graph map shown in FIG.
In addition to setting per, a control signal for preventing the valve portion of the expansion device 5 from exceeding the upper limit value θupper is output.

In this embodiment, the cooling load calculating means 20 determines the cooling load by integrating the signals from the outside air temperature sensor 17 and the indoor temperature sensor 18. However, the present invention is not limited to this. For example, the fan 1 that sends out the temperature of the intake air of the evaporator 6 or the cool air into the room
An air volume of 0 or the like can also be used as a material for determining the cooling load.

Hereinafter, control of the expansion device in the first embodiment will be described with reference to the flowchart shown in FIG. The expansion device control is periodically executed from a main control routine for performing normal air conditioning control when, for example, a cooling operation switch (A / C switch) provided on an operation panel of the air conditioner is turned on. It is.

First, at step 100, the refrigerant pressure Pexpin and the refrigerant temperature Texpin are detected based on the detection signals from the refrigerant pressure sensor 15 and the refrigerant temperature sensor 16, and at step 110, the detected refrigerant pressure Pexpin and the refrigerant temperature Texpin are used as target values. The pressure Pa is calculated. At step 120, the outside air temperature Tout and the inside air temperature Tin are detected by the outside air temperature sensor 17 and the inside air temperature sensor 18, and at step 130, the cooling load CL is calculated from the outside air temperature Tout and the inside air temperature Tin.

Next, at step 140, it is determined whether or not the detected cooling load CL is equal to or less than a predetermined value CL0. If it is determined that the cooling load CL is not equal to or less than the predetermined value CL0, step 170 In the variable L
Is set in the range of L ≧ 1, and in step 180, the proportional constant Kp and the integration constant K are calculated using the set variable L.
i and the differential constant Kd are calculated. In addition, K in step 180
1, K2 and K3 are preset constants.

In step 140, the cooling load C
If it is determined that L is equal to or less than the predetermined value CL0, it is determined in step 150 whether the valve operation of the expansion device 5 is in the closing direction, and if it is determined that the valve operation is not in the closing direction, Sets the variable L in the range of L ≧ 1 in the step 170. On the other hand, step 1
In 50, if it is determined that the valve operation is in the closing direction, after setting the variable L in the range of 0 <L <1,
In step 180, the proportional constant Kp, the integral constant Ki, and the differential constant Kd are calculated.

Next, at step 190, the proportional constant Kp, the integral constant Ki, the differential constant Kd, and the deviation ΔP between the target pressure Pa and the actual pressure Pexpin (= Pa−P
expin), the stroke amount S of the valve portion is calculated, and in step 200, the lower limit value θlow and the upper limit value θupper of the valve opening are set based on the obtained cooling load CL. A control signal based on the calculated stroke amount S is output to the electromagnetic coil of the expansion device 5.

Then, in step 220, it is determined whether or not the valve opening is smaller than the lower limit θlow. If it is determined that the valve opening is not smaller than the lower limit θlow, the process proceeds to step 220. At 240, it is determined whether or not the valve opening is greater than the upper limit value θupper. If it is determined that the valve opening is not greater than the upper limit value θupper, the process returns to the main control routine. .

If it is determined in step 220 that the valve opening is smaller than the lower limit value θlow, in step 230, the valve opening degree is increased to the lower limit value θlow, and the process proceeds to step 240. 24
If it is determined at 0 that the valve opening is larger than the upper limit value θupper, at step 250,
After reducing the valve opening to the upper limit value θupper, the process returns to the main control routine.

According to the refrigeration cycle control device according to the first embodiment, the cooling load CL obtained by the cooling load calculating means 7 becomes equal to or less than the predetermined value CL0, and the valve portion of the expansion device 5 is closed. When the valve is operated, the valve operation delay means 23 calculates P to calculate the stroke amount S of the valve section.
By changing the proportional constant Kp, the integral constant Ki, and the differential constant Kd in the ID control arithmetic expression (Equation 1 above) so that the stroke amount S becomes smaller than that under a normal cooling load, the valve of the expansion device 5 is changed. Operation is slowed down.

As a result, as shown in FIG. 6, when the load is low (curve A), the opening degree of the valve is changed slowly, and the opening degree of the target valve is smaller than that at high load (curve B). , It takes a long time to reach the temperature and the valve opening degree does not change too rapidly for the refrigerant whose discharge capacity is reduced by the discharge capacity variable mechanism of the compressor 2, thereby preventing hunting of the expansion device. be able to. Further, since the time during which the refrigerant flows to the evaporator 4 while the expansion device 5 is closed is ensured longer than before, it is possible to prevent an abnormal rise in temperature due to the supply of the refrigerant to the evaporator 4 being stopped.

Further, the lower limit value θlow and the upper limit value θupper of the valve opening are changed according to the cooling load CL. When the load is low, the lower limit value θlow is set to a high value so as not to be fully closed, and the upper limit value θupper is set to a low value, so that the valve opening range of the expansion device 5 becomes narrower than that at the time of a high load. .

As a result, the circulation of the refrigerant is ensured even at a low load, so that an abnormal rise in the temperature of the evaporator 4 can be prevented. When the valve opening range of the expansion device 5 is large at a low load, the refrigerant rapidly flows from the high-pressure line 11 to the low-pressure line 12 when the valve portion reaches the maximum opening, and the pressure of the high-pressure line 11 suddenly increases. However, the hunting phenomenon in which the opened valve portion closes soon again is likely to occur, but as described above, the hunting is effectively prevented by narrowing the valve opening range at a low load. be able to.

Hereinafter, a second embodiment of the present invention will be described with reference to the accompanying drawings. The same reference numerals as those in the first embodiment or those having similar functions and effects will be used. The description is omitted.

As shown in FIG. 7, the C / U 8 of the refrigeration cycle control device according to the second embodiment of the present invention comprises a cooling load calculating means 20, a target pressure calculating means 21, a valve opening degree controlling means 22, Valve operation delay means 23, lower limit opening setting means 2
4. An upper limit opening setting means 25 is provided. The valve operation delay means 23 according to the second embodiment
When the cooling load CL obtained by the cooling load calculating means 20 is equal to or less than a predetermined value CL0, the sampling interval of the refrigerant pressure Pexpin and the refrigerant temperature Texpin by the refrigerant pressure sensor 15 and the refrigerant temperature sensor 16 is set to a high value. It should be longer than under load. In particular,
A sampling interval ti longer than the sampling interval at the time of the cooling load larger than the predetermined value CL0 is set, and when the count by the timer 26 reaches the sampling interval ti, the refrigerant pressure sensor 15 and the refrigerant temperature sensor 16 The detection is performed.

The cooling load calculating means 20, target pressure calculating means 21, valve opening control means 22, lower limit opening setting means 2
4. The upper limit opening setting means 25 may have the same function as that of the first embodiment.

Hereinafter, the expansion device control of the refrigeration cycle control device according to the second embodiment will be described with reference to the flowchart shown in FIG. This expansion device control is performed by, for example, a cooling operation switch (A) provided on an operation panel of an air conditioner.
When the (/ C switch) is ON, this routine is periodically executed from a main control routine for performing normal air conditioning control.

First, in step 300, the outdoor temperature Tout and the indoor temperature Tin are detected based on the detection signals from the outdoor temperature sensor 17 and the indoor temperature sensor 18. In step 310, the detected outdoor temperature Tout and indoor temperature Tin are detected. The cooling load CL is calculated from
At 20, the obtained cooling load CL is equal to a predetermined value C.
It is determined whether it is equal to or less than L0.

In step 320, the cooling load CL
If it is determined that is less than or equal to the predetermined value CL0, a sampling interval ti longer than the normal time is set in step 330, and in step 340, the timer 26 is counted at intervals of, for example, one second to measure the elapsed time t. .

Next, at step 350, it is determined whether or not the elapsed time t is longer than the sampling interval ti. If it is determined that the elapsed time t is not longer than the sampling interval ti, the process proceeds to step 340.
And the timer 26 continues counting, while the elapsed time t
, The refrigerant pressure sensor 15 and the refrigerant temperature sensor 16 detect the refrigerant pressure Pexpin and the refrigerant temperature Texpin in step 360. If it is determined in step 320 that the cooling load CL is not less than the predetermined value CL0, the flow proceeds to step 360 where the refrigerant pressure Pexpin and the refrigerant temperature Texpin are detected.

In step 370, a target pressure Pa is calculated from the detected refrigerant pressure. In step 380, the target pressure Pa is calculated based on the determined target pressure Pa and the actual pressure Pexpin detected by the refrigerant pressure sensor 15. After outputting a control signal to the electromagnetic coil of the expansion device 5, the process returns to the main control routine.

According to the refrigeration cycle control device according to the second embodiment, when the cooling load CL detected by the cooling load calculating means 7 becomes equal to or less than the predetermined value CL0, the valve operation delay means 23 causes the refrigerant pressure sensor 15 to operate. And the refrigerant pressure Pexpin and the refrigerant temperature Texpin by the refrigerant temperature sensor 16.
Is delayed, the output of the control signal to the electromagnetic coil is delayed, and the valve operation of the expansion device 5 is delayed.

As a result, as shown in FIG. 6, the valve opening changes slowly when the load is low (curve A), and the target valve opening is smaller than when the load is high (curve B). , It takes a long time to reach the temperature and the valve opening degree does not change too rapidly for the refrigerant whose discharge capacity is reduced by the discharge capacity variable mechanism of the compressor 2, thereby preventing hunting of the expansion device. be able to. Further, since the time during which the refrigerant flows to the evaporator 4 while the expansion device 5 is closed is ensured longer than before, it is possible to prevent an abnormal rise in temperature due to the supply of the refrigerant to the evaporator 4 being stopped.

[0058]

As described above, according to the present invention, hunting of the valve portion can be prevented by reducing the reactivity of the valve opening of the expansion device at a low load.
It is possible to prevent an abnormal rise in temperature due to the supply of the refrigerant to the evaporator being stopped.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a refrigeration cycle according to the present invention.

FIG. 2 is a block diagram showing a configuration of a control unit according to the first embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a refrigerant temperature and a target pressure.

FIG. 4 is a graph showing a relationship between a cooling load and an upper limit value and a lower limit value of a valve opening.

FIG. 5 is a flowchart showing valve opening degree adjustment control of the refrigeration cycle control device according to the first embodiment of the present invention.

FIG. 6 is a graph showing the relationship between the time and the amount of change in the valve opening in the refrigeration cycle control device according to the present invention.

FIG. 7 is a block diagram showing a configuration of a control unit according to a second embodiment of the present invention.

FIG. 8 is a flowchart illustrating valve opening adjustment control of a refrigeration cycle control device according to a second embodiment of the present invention.

FIG. 9 is an explanatory diagram of PID control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refrigeration cycle 2 Compressor 3 Condenser 4 Internal heat exchanger 5 Expansion device 6 Radiator 7 Accumulator 8 Control unit (C / U) 11 High pressure line 12 Low pressure line 15 Refrigerant pressure sensor 16 Refrigerant temperature sensor 17 Outside air temperature sensor 18 Inside air temperature sensor Reference Signs List 20 cooling load calculating means 21 target pressure calculating means 22 valve opening control means 23 valve operation delay means 24 lower limit opening setting means 25 upper limit opening setting means 26 timer

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Yuji Kawamura 39, Higashihara, Chiyo-ji, Odai-gun, Osato-gun, Saitama Prefecture Inside of Xexel Konan Plant (72) Inventor Shunji Muta 39, Higashihara, Chiyo-ji, Konan-cho, Osato-gun, Saitama Prefecture Address: Inside the Xexel Gangnam Plant (72) Inventor Kenji Iijima 39, Higashihara, Chiyo-ji, Odai-gun, Osato-gun, Saitama Prefecture Inside of the Zexxel Gangnam Plant (72) Inventor: Sakae Hayashi 39, Chiyo-ji, Higashihara, Konan-cho, Osato-gun, Saitama Prefecture Address: Inside the Xexel Gangnam Plant (72) Inventor Hiroshi Kanai 39, Higashihara, Chiyo-ji, Odai-gun, Osato-gun, Saitama 39 Inventor: Akihiko Takano 39, Higashihara, Chiyo-ji, Konan-cho, Osato-gun, Saitama Address Zexel Gangnam Plant

Claims (8)

[Claims] 1. A compressor that compresses and discharges a refrigerant, a radiator that cools the refrigerant compressed by the compressor, an expansion device whose valve opening can be adjusted by a control signal, and expansion by the expansion device. A refrigerating cycle constituted by at least an evaporator for evaporating the refrigerant, wherein an environmental factor detecting means for detecting an environmental factor of the refrigerating cycle, and a cooling load is calculated from the environmental factor detected by the environmental factor detecting means. Cooling load calculating means, refrigerant pressure detecting means for detecting the pressure of the refrigerant flowing into the expansion device, refrigerant temperature detecting means for detecting the temperature of the refrigerant flowing into the expansion device, detected by the refrigerant temperature detecting means Target pressure calculating means for calculating a target pressure of the refrigerant flowing into the expansion device from the detected refrigerant temperature, and the target pressure detected by the refrigerant pressure detecting means. A valve opening control device that outputs a control signal to control the valve opening of the expansion device so that the actual refrigerant pressure matches the target pressure calculated by the target pressure calculating means; and the cooling load calculation. A valve operation delay that delays the valve operation of the expansion device controlled by the valve opening control means when the cooling load calculated by the means is equal to or less than a predetermined value, compared to when the cooling load is larger than the predetermined value. Means for controlling a refrigeration cycle. 2. The refrigeration cycle control device according to claim 1, wherein the valve operation delay means makes the valve operation in the opening direction faster than the valve operation in the closing direction. 3. The valve operation delay means changes a constant of a formula for calculating a control signal output by the valve opening control means when the cooling load calculated by the cooling load calculation means is equal to or less than a predetermined value. The refrigeration cycle control device according to claim 1, wherein the valve operation is delayed. 4. The sampling interval of the refrigerant pressure and the refrigerant temperature by the refrigerant pressure detecting means and the refrigerant temperature detecting means when the cooling load calculated by the cooling load calculating means is equal to or less than a predetermined value. 3. The refrigeration cycle control device according to claim 1, wherein the length of the refrigeration cycle is increased. 5. When the cooling load calculated by the cooling load calculating means is equal to or less than a predetermined value, a lower limit opening setting means for changing the lower limit of the valve opening so that the valve opening does not become zero is provided. The refrigeration cycle control device according to any one of claims 1 to 4, further comprising: 6. When the cooling load calculated by the cooling load calculating means is equal to or less than a predetermined value, the upper limit opening setting means for setting the upper limit of the valve opening smaller than when the cooling load is larger than the predetermined value. 6. The method according to claim 1, further comprising:
The refrigeration cycle control device according to any one of the above. 7. The refrigerant used in the refrigeration cycle,
The refrigeration cycle control device according to claim 1, wherein the refrigeration cycle control device is carbon dioxide. 8. The refrigeration cycle control device according to claim 1, wherein the predetermined value is a value at which the refrigerant is below a critical point.