JPH01269863A - Refrigeration cycle controller - Google Patents

Abstract

PURPOSE:To make it possible to control appropriately the degree of superheat of a refrigerant and to display constantly a necessary and sufficient cooling capability, by providing a controlling means for controlling the opening of an expansion valve means so as to make a determined degree of superheat agree with a determined target value. CONSTITUTION:A controlling means 9 controls the opening of an expansion valve means 5 according to both a target value of degree of superheat determined according to a detected pressure and a detected rotating speed by a target value-determining means 8 and a degree of superheat determined according to a detected temperature and the detected pressure by a superheat degree-determining means 7. The target value determined by the means 8 is higher or lower according as the detected pressure and the detected rotating speed are lower or higher. When the opening of the expansion valve means 5 is controlled based on the target value of degree of superheat thus determined, a sufficient degree of superheat of a refrigerant can be secured through a reduction in cooling capability of an evaporating means 1 based on the small opening of the valve means 5 at the time of a low load on the evaporating means 1 under a low rotating speed of a compressing means 2. At the time of a high load on the evaporating means 1, a high cooling capability of the evaporating means 1 based on the large opening of the valve means 5 can be satisfactorily secured under a reduction in the degree of superheat.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a refrigeration cycle control device that is used in air conditioners, refrigerators, freezing devices, etc., and particularly relates to a refrigeration cycle control device that is equipped with an electric expansion valve. The present invention relates to a refrigeration cycle control device.

(Prior Art) Conventionally, in this type of refrigeration cycle control device, as shown in Japanese Patent Application Laid-Open No. 60-218559, in order to cope with all load conditions, a control system is used to adjust the refrigerant pressure or refrigerant temperature. There is a system that performs switching control between the degree of superheating of the refrigerant at the outlet of the evaporator and the degree of superheating of the refrigerant at the inlet of the compressor.

[Problem to be solved by the invention]

However, in such a configuration, in the above switching control, a pressure sensor and a temperature sensor that detect the pressure and temperature of the refrigerant at the outlet of the evaporator, and a pressure sensor and a temperature sensor that detect the pressure and temperature of the refrigerant at the suction port of the compressor are used. As a result, an increase in the number of sensors leads to an increase in costs.

Therefore, in order to cope with this problem, the present invention employs a minimum number of sensors in a refrigeration cycle control device equipped with an electric expansion valve to appropriately control the degree of superheating of the refrigerant. The aim is to always be able to exhibit just the right amount of cooling capacity.

[Means to solve the problem]

In solving this problem, the structural features of the present invention are as follows:
As illustrated in FIG. 1, evaporation means 1 for cooling the incoming air stream in connection with the evaporation of the incoming refrigerant, compression means 2 for compressing the evaporative refrigerant from the evaporation means 1, and compressing means 2 for compressing the evaporative refrigerant from the evaporating means 1, An evaporation pressure control means 3 that controls the evaporation pressure so that it does not fall below a certain value on the evaporation means 1 side, a condensation means 4 that condenses the compressed refrigerant, and an evaporation pressure control means 3 that expands the condensed refrigerant according to the degree of opening. In a refrigeration cycle control device comprising an electric expansion valve means 5 which controls the superheat degree of the refrigerant to the compression means 2 to a target value and causes the refrigerant to flow into the evaporation means 1, the refrigerant is transferred from the evaporation pressure control means 3 to the compression means 2. temperature detection means 6a for detecting the temperature of the refrigerant flowing from the evaporation pressure control means 3 to the compression means 2, pressure detection means 6b for detecting the pressure of the refrigerant from the evaporation pressure control means 3 to the compression means 2, and rotation speed detection means for detecting the rotation speed of the compression means 2. 6C, and superheat degree determining means 7 for determining the degree of superheat of the refrigerant based on the detected temperature and detected pressure,
target value determining means 8 for determining the target value of the degree of superheat to decrease (or increase) in accordance with increases (or decreases) in both the detected rotational speed and the detected pressure; A control means 9 is provided for controlling the opening degree of the expansion valve means 50 so as to match the opening degree of the expansion valve means 50.

[Effect]

By configuring the present invention in this way, the control means 9 can control the target value of the degree of superheat determined by the target value determining means 8 according to the detected pressure and the detected rotational speed, and the detected temperature by the degree of superheat determining means 7. The degree of opening of the expansion valve means 5 is controlled according to the degree of superheat determined according to the detected pressure. In such a case, the target value of the degree of superheat determined by the target value determining means 8 becomes larger as the detected pressure and rotational speed are lower, and becomes smaller as the detected pressure and rotational speed are higher. Therefore, if the opening degree of the expansion valve means 5 is controlled as described above based on the target value of the degree of superheat determined in this way, when the load of the evaporation means 1 is low when the rotation speed of the compression means 2 is low, A sufficient degree of superheating of the refrigerant can be ensured while the cooling capacity of the evaporation means 1 is reduced due to the small opening degree of the expansion valve means 5, resulting in power saving. On the other hand, when the evaporation means 1 is under a high load when the compression means 2 is at a low rotational speed, the high cooling capacity of the evaporation means 1 based on the large opening degree of the expansion valve means 5 can be sufficiently ensured while reducing the degree of superheating. In such a case, when both the rotational speed of the compression means 2 and the load on the evaporation means 1 are high, the higher the rotational speed is, the lower the target value of the degree of superheat is to reduce the refrigerant discharged from the compression means 2 while ensuring a high cooling capacity. suppress unnecessary temperature rises. On the other hand, when the load on the evaporator 1 is low even if the rotational speed is high, the target value of the degree of superheat is increased to ensure power saving. Further, the above-mentioned effects can be achieved by employing only the three detection means 6a to 6c, which leads to cost reduction of this type of device.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.
The figure shows an example in which the refrigeration cycle control device according to the present invention is applied to a vehicle air conditioner. The air conditioner includes an air duct 10, and in this air duct 10, from upstream to downstream, a blower 20, an evaporator 30, an air mix damper 40, and a heater core 5 are installed.
0 are arranged sequentially. Blower 20 is air duct) 10
An air flow is introduced into the interior of the vehicle and is blown out through the evaporator 30, air mix damper 40, and heater core 50 into the passenger compartment of the vehicle. The evaporator 30 cools the airflow from the blower 20 in response to the evaporation action of its incoming refrigerant.

The refrigeration cycle control device includes a compressor 90 connected to the engine 60 of the vehicle via a belt mechanism 70 and an electromagnetic clutch 80, and the belt mechanism 70 includes a V-pulley 71 pivotally supported on the output shaft 61 of the engine 60, a V-pulley 72 pivotally supported on a rotation shaft 91 of a rotor eccentrically and rotatably supported within the housing of the compressor 90;
It is composed of a V-belt 73 wound around both pulleys 71 and 72. The electromagnetic clutch 80 is a combination lever 9
The electromagnetic clutch 80 is assembled coaxially with the rotating shaft 91 of the compressor 90 and the V-pulley 72, and this electromagnetic clutch 80 is engaged by the excitation of its electromagnetic coil so that the pulley 72 can transmit power to the rotating shaft 91 of the compressor 90. They are connected and then separated by demagnetization of the electromagnetic coil to cut off the IJ72 from the rotating shaft 91.

The compressor 90 is operated under the engagement of the electromagnetic clutch 80.
It rotates as power is transmitted from the engine 60 via the belt mechanism 70, sucks refrigerant from the evaporator 30 through the pipe P1, compresses the sucked refrigerant, and discharges it as a high-temperature, high-pressure compressed refrigerant into the pipe P2. The evaporation pressure control valve 30a is installed in the pipe Pl near the refrigerant outlet of the evaporator 30, and is designed to prevent the temperature of the evaporator 30 from falling below a predetermined value. ,
The pressure of the refrigerant in the pipe P1 near the refrigerant outlet of the evaporator 30 is maintained at a predetermined pressure or higher.

The condenser 100 condenses the compressed refrigerant in the pipe P2 under the heat dissipation effect of the cooling fan 100a, and causes the condensed refrigerant to flow into the pipe P3. The gas-liquid separator 110 receives the condensed refrigerant in the pipe P3, separates it into a gas phase component and a liquid phase component, and causes this liquid phase component to flow into the pipe P4. The electric expansion valve 120 expands the refrigerant from the pipe P4 according to its actual opening degree, and causes the refrigerant to flow into the evaporator 30 through the pipe P5 as a low-temperature, low-pressure refrigerant. However, the expansion valve 12
The actual opening degree of 0 is proportional to the amount of displacement of the valve body, which is a linear actuator built into the expansion valve 120, above the minimum opening degree.

Next, to explain the electric circuit configuration of the refrigeration cycle control device, the temperature sensor 130a is connected to the evaporation pressure control valve 30.
The actual temperature of the refrigerant in the pipe Pl is detected downstream of a and generated as a refrigerant temperature detection signal. The pressure sensor 130b is
The zero rotation speed sensor 140 detects the actual pressure of the refrigerant in the pipe Pl downstream of the evaporation pressure control valve 30a and generates a pressure detection signal, and outputs the actual rotation speed of the output shaft 61 of the engine 60. Generates a series of pulse signals at a frequency proportional to the detection result. The operation switch SW is operated to generate an operation signal when operating the air mixing device. The AD converter 150 digitally converts the refrigerant temperature detection signal from the temperature sensor 130a and the pressure detection signal from the pressure sensor 130b into a refrigerant temperature digital signal and a pressure digital signal, respectively. The waveform shaper 160 shapes the waveform of each pulse signal from the rotational speed sensor 140 and sequentially generates a shaped signal.

The microcomputer 170 has operation switches SW and A.
- In cooperation with the D converter 150 and the waveform shaper 160, the combiator program is executed according to the flowchart shown in FIG. 3, and during this execution, the electromagnetic clutch 8
The calculation processing necessary for controlling each of the drive circuits 180 and 190 connected to the electromagnetic coil 0 and the linear actuator of the expansion valve 120 is performed. However, the above-mentioned computer program is stored in the ROM of the micro combinator 170 in advance. Note that the microcomputer 170 operates by being supplied with power from the battery B via the ignition switch IC of the vehicle.

In this embodiment configured as described above, when the ignition switch IG is closed, the engine 60 is operated to start the vehicle, and the microcomputer 1
70, the microcomputer 170 will
At step 200, execution of the computer program is started according to the flowchart of FIG. 3, and at step 210
At step 210, it is determined that it is "N0" based on the generation of the operation signal from the operation switch SW, and the coil excitation signal for exciting the electromagnetic coil of the electromagnetic clutch 80 remains extinguished using the steering knob 210a. Return to

When an operation signal is generated from the operation switch SW at such a stage, the microcomputer 170 determines rYESJ in step 210, and in step 210b, the pressure digital signal and refrigerant temperature from the A-D converter 150 are output. Each value of the digital signal is converted into refrigerant pressure Ps and refrigerant temperature Tr.
In step 210C, the rotational speed Ne of the engine 60 is calculated based on each shaping signal from the waveform shaper 160. Therefore, if the refrigerant pressure ps is higher than the predetermined pressure Pso (previously stored in the ROM of the microcomputer 170), the microcomputer 17
0 is determined as "rYES" in step 230, and a coil excitation signal is generated in step 230a. Then, the drive circuit 170 excites the electromagnetic coil of the electromagnetic clutch 80 in response to the coil excitation signal from the microcomputer 170, and the electromagnetic clutch 80 engages to transmit the power of the engine 60 to the compressor 90 via the mechanism 70. and activate it. At this time, the blower 20, heater core 5
0 and the cooling fan 110a are both operating.

Thus, the compressor 90
The refrigerant is sucked in from the evaporator 30 through the pipe P1, compressed, and discharged as a high-temperature, high-pressure compressed refrigerant into the pipe P2, and the condenser 100 condenses the compressed refrigerant from the pipe P2 under the heat dissipation action of the cooling fan 100a. The gas-liquid separator 110 flows into the pipe P3 as a condensed refrigerant.
The liquid phase component in the condensed refrigerant from the pipe is caused to flow into the pipe P4 as a refrigerant, and the expansion valve 120 expands the refrigerant from the pipe P4 based on its actual opening degree and flows into the evaporator 30 through the pipe P5. let Therefore, the air flow introduced into the air duct 10 by the blower 20 is
0, the refrigerant is cooled according to the inflowing refrigerant, heated by the heater core 50 according to the actual opening degree of the air mix damper 40, and blown out into the passenger compartment of the vehicle. Note that the refrigerant that has flowed into the evaporator 30 passes through the pipe P1 and is sucked into the compressor 90 via the evaporation pressure control valve 3Qa.

When the computer program proceeds to step 240, the microcomputer 170 generates a plurality of characteristic curves L1.・
. . L E + . . . Based on predetermined data representing Ln (see FIG. 4), a superheat degree target value SHo is determined according to the refrigerant pressure ps and the rotational speed Ne. In this case, the superheat degree target value S Ho is the target value of the superheat degree of the refrigerant in the pipe Pl downstream of the evaporation pressure control valve 30a. Moreover, each of the characteristic curves L1 to Ln has a rotational speed p as shown in FIG.
Superheat degree target value SHo and refrigerant pressure P with Je as a parameter
s, and are stored in advance in the ROM of the microcomputer 170 as the predetermined data.

In this embodiment, the characteristic curves L1 to Ln are determined as shown in FIG. 4 for the following reasons.

(1) Rotational speed N e, I of the engine 60! l] Chico 77"l/When the rotational speed of the shaft 90 is low. If the suction pressure of the compressor 90, that is, the refrigerant pressure P3 is high, this corresponds to the establishment of a high load condition, so the superheat degree target value S
By reducing Ho, a high cooling capacity of the evaporator 30 is ensured. On the other hand, when the refrigerant pressure Ps is low, this corresponds to the establishment of a low load condition, so power saving is ensured by increasing the superheat degree target value SHo.

(2) When the rotation speed of the compressor 90 is high, the refrigerant pressure P
If s is high, this corresponds to the establishment of a high load condition, and the discharge temperature of the refrigerant from the compressor 90 becomes high. Therefore, by reducing the superheat degree target value S Ho, the increase in the discharge temperature is suppressed and the evaporator 30 is Ensure high cooling capacity. On the other hand, when the refrigerant pressure Ps is low, which corresponds to the establishment of a low load condition, the superheat degree target value S Ho is increased to such an extent that power saving is ensured while suppressing the rise in the discharge temperature. In FIG. 4, the symbol S Ho a represents the minimum value of 8 ports 0 in the region where liquid return (liquid back) of the refrigerant to the compressor 90 does not occur.

After the arithmetic processing in step 240, the microcomputer 170 converts the superheating degree deviation En-1 into the superheating degree deviation En-u in each of the following steps 250 to 270, and converts the superheating degree deviation En into the superheating degree deviation En-1. and set
And the duty ratio DTn is set to the duty ratio DTn-+. Here, the superheat degree deviation En is calculated using the following formula (
11.

En-Tr-Ts-5Ho...11) Also, this formula (
In 1), the symbol TS represents the evaporation temperature of the refrigerant corresponding to the pressure of the refrigerant in the pipe Pl, and this evaporation temperature Ts is expressed by the following equation (2).

'l'5=f(PS)...(2) Also, the duty ratio DTn is calculated using the following formula (3) (PID control θ represents the proportional gain, integration time 1 minute time, and sampling time, respectively. , each superheat degree deviation E n-I and En-U represent each superheat degree deviation preceding each superheat degree deviation En and E n-1, respectively. In addition, each of equations (i) to (3)
is stored in the ROM of the micro combinator 170 in advance.

In addition, in the arithmetic processing in each step 250 to 270 as described above, since En-1, En and DTn are not calculated, the R of the microcomputer 170 is
Each initial deviation E-1, EO and initial duty ratio DTo stored in advance in OM are En-co, En-1 and DT.
n-1, respectively. Thereafter, in step 280, the microcomputer 170 calculates the formula (
2), the evaporation temperature TS is determined according to the refrigerant pressure Ps in step 210b, and the superheat degree deviation En is determined according to the evaporation temperature Ts, the superheat degree target value SHo and the refrigerant temperature Tr in step 240, based on equation (1). determine, and the expression (
Based on 3), the superheat degree deviation En and each step 25
Each superheat degree deviation En-yu at 0.260 and 270.

The duty ratio DTn is determined according to En-1 and the duty ratio DTn-1. As a result, the superheat degree deviation En
In other words, the duty ratio DTn is determined so that the degree of superheat of the refrigerant becomes the target value SHo of the degree of superheat.

When the duty ratio DTn is determined in this way, the microcomputer 170 generates the same duty ratio DTn as a duty output signal in step 290, and in response, the drive circuit 190 operates the linear actuator of the expansion valve 120. It is displaced by an amount corresponding to the determined duty ratio DTn.

At the current stage, the load on the evaporative lake 30 is low (
That is, if the refrigerant pressure Ps is low) and the rotational speed Ne is low, the superheat degree deviation En, that is, the duty ratio DTn is small, so the amount of increase in the opening degree of the expansion valve 120 is small. Therefore, the refrigerant in the pipe P4 is greatly throttled by the expansion valve 120 based on its small opening and flows into the evaporator 30. Thereby, the evaporator 30 cools the air flow from the blower 20 in response to the inflowing refrigerant. Further, the degree of superheat of the refrigerant flowing from the evaporator 30 through the evaporation pressure control valve 30a into the portion of the pipe Pl located downstream thereof is controlled to be the half-heat degree target value SHO in step 240. In this case, since the load is low and the rotational speed Ne is low as described above, the degree of superheating is controlled so as to approach the maximum value specified by the characteristic curve L1. Therefore, since the duty ratio DTn, that is, the opening degree of the expansion valve 120 is small, in exerting the cooling capacity of the evaporator 30,
The refrigerant is used to completely vaporize, which helps save power.

Thereafter, each step 210 of the computer program
b, 210 c, and 230. In the process of repeating the calculations from 240 to 290, when the refrigerant pressure P3 and the refrigerant temperature Tr in step 210b increase under the low rotational speed Ne in step 210C, a high load on the evaporator 30 is established. , the superheat target value S Ho in step 240 is one characteristic curve L(N
(determined by e), the superheat degree deviation En increases in step 280, and the duty ratio DTn increases. In this way, the duty ratio DT
As n increases, the degree of opening of the expansion valve 120 increases, and the degree of restriction of the expansion valve 120 to the refrigerant flowing into the evaporator 30 decreases, which reduces the target value SHo of the degree of superheating of the refrigerant flowing into the pipe P1. Therefore, the cooling capacity of the evaporator 30 can be increased.

Further, as described above, the refrigerant pressure P in step 210b
s and the refrigerant temperature Tr increase, the superheat degree target in step 240 is set based on the premise that if the rotation speed Ne in step 210C also increases, the temperature of the refrigerant discharged from the compressor 90 may become unnecessarily high. Value SHo
decreases depending on the refrigerant pressure Ps and the rotational speed Ne in relation to the predetermined data shown in FIG. In such a case, the higher Ne is, the SHo is determined by the characteristic curve located lower in FIG. 4 among the characteristic curves of the predetermined data. Therefore, although the superheat degree deviation En and the duty ratio DTn in step 280 further increase, and the opening degree of the expansion valve 120 further increases, the superheat degree target value SHo of the refrigerant flowing into the pipe Pl The compressor 90 is designed to further reduce the
It is possible to suppress the temperature rise of the discharged refrigerant.

Further, as described above, when the rotation speed Ne increases in step 210c, unlike the above, if the refrigerant pressure Ps in step 210b remains low, the load on the evaporator 30 is determined to be low, and the superheat degree in step 240 is determined. Target value SH.

is largely determined depending on the refrigerant pressure Ps in relation to the predetermined data shown in FIG. Therefore, similarly to the above, the expansion valve 120
Since the degree of opening is small, vaporization of the refrigerant is promoted when the evaporative lake 30 exerts its cooling ability, thereby ensuring power saving.

In addition, in the above explanation of the operation, since the evaporation pressure control valve 30a controls the pressure of the refrigerant flowing out from the evaporator 30 to be maintained constant, the evaporation pressure control valve 30a
never freezes. Note that when the determination in step 230 is "NO", the microcomputer 170 executes the computer program in step 21.
Proceed after 0a.

In addition, in carrying out the present invention, the present invention may be applied not only to a vehicle air opening device but also to various air conditioning devices, refrigeration devices, refrigeration devices, and the like.

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to the configuration of the invention described in the claims, FIG. 2 is a block diagram showing an embodiment of the invention, FIG. 3 is a flowchart showing the operation of the microcomputer in FIG. Figure 4 is a graph showing the relationship between refrigerant pressure and superheat degree target value using engine rotational speed as a parameter. Explanation of symbols 30... Evaporator, 90... Compressor, 1
00... Capacitor, 120... Expansion valve, 130a
...Temperature sensor, 130b...Pressure sensor, 170
...Microcomputer.

Claims (1)

[Claims] evaporation means for cooling the incoming air flow in connection with the evaporation of the inflowing refrigerant; compression means for compressing the evaporative refrigerant from the evaporation means; an evaporation pressure control means for controlling, a condensation means for condensing the compressed refrigerant, and an expansion means for the condensed refrigerant according to the degree of opening, so that the degree of superheating of the refrigerant from the evaporation pressure control means to the compression means is set to a target value. In the refrigeration cycle control device, the refrigeration cycle control device includes an electric expansion valve means for causing the refrigerant to flow into the evaporation means while controlling the refrigerant to flow into the evaporation means. pressure detection means for detecting the pressure of the refrigerant from the pressure control means to the compression means; rotation speed detection means for detecting the rotation speed of the compression means; and determining the degree of superheating of the refrigerant based on the detected temperature and the detected pressure. a target value determining means for determining the target value of the degree of superheat to decrease (or increase) in accordance with an increase (or decrease) in both the detected rotational speed and the detected pressure;
A refrigeration cycle control device comprising: control means for controlling the opening degree of the expansion valve means so that the determined degree of superheat matches the determined target value.