JPS61262570A - Controller for refrigeration cycle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a control device for a refrigeration cycle, and the present invention relates to a control device for a refrigeration cycle. The present invention relates to a refrigeration cycle control device using a type expansion valve.

[Background of the invention]

A conventional device, as described in Japanese Patent Publication No. 56-16353VC, detects temperature signals at the inlet and outlet of the evaporator, and uses the detected signals to control an electric expansion valve to control the refrigerant flow rate in the refrigeration cycle. be. In this method, if the refrigerant at the inlet of the expansion valve is in a supercooled state, the degree of superheating of the refrigerant at the outlet of the evaporator can be well controlled. However, for example, if the amount of air blown to the condenser increases rapidly, the high pressure side pressure suddenly decreases VC, and the refrigerant at the expansion valve inlet turns into bubbles, the state change of this high pressure side cycle will occur as described above. No consideration was given to the fact that the refrigerant supply to the evaporator is insufficient and the cooling capacity is reduced due to a delay in response until the temperature signal VC appears at the inlet and outlet of the evaporator and a decrease in the gain of the expansion valve.

[Purpose of the invention]

An object of the present invention is to provide a refrigeration cycle control device that does not reduce cooling capacity even if the pressure of refrigerant at the inlet of an expansion valve suddenly decreases.

[Summary of the invention]

If the change in the physical quantity correlated with the pressure state of the refrigerant at the inlet of the expansion valve is less than or equal to a predetermined value in a predetermined time, the first control changes the valve opening degree of the electric expansion valve according to the degree of superheating of the refrigerant at the outlet of the evaporator. a second means for controlling the valve opening of the electric expansion valve based on the physical quantity reflecting the pressure state of the refrigerant at the inlet of the expansion valve when the change in the physical quantity becomes equal to or greater than a predetermined value in a predetermined time;
It is characterized by having a groan suppressing means.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

First, the refrigeration cycle consists of a pressure #i machine 1, a condenser 2, a liquid reservoir 3, an evaporator 5, which are driven and controlled by an electromagnetic clutch 1a#/c, and an electric motor which controls the opening degree of a valve by inputting an electric signal. The electric expansion valve 4 adiabatically expands high-temperature, high-pressure liquid refrigerant, converts it into low-temperature, low-pressure refrigerant, and exchanges heat with external air in the evaporator 5 for cooling. .

Next, in the refrigeration cycle of this embodiment, a temperature sensor 6.7 for detecting refrigerant temperature and pressure sensors 8, 9 for detecting refrigerant pressure are attached at predetermined positions.

1o is a control circuit which inputs signals from these temperature and pressure sensors to drive and control the electric expansion valve 4.

Here, the refrigerant pressure PeO at the outlet of the evaporator 5 detected by the pressure sensor 8 is the pressure-temperature conversion circuit (
1) At 10 a, the pressure Peo vc is converted into the corresponding saturation temperature t-SC of the refrigerant, and the refrigerant temperature at the outlet of the evaporator 5 detected by the temperature sensor 6 is t0. becomes an output signal of the refrigerant superheat degree SHe <= tea-tea) at the outlet of the evaporator 5 in the differential amplification circuit (1) 10b. Note that the saturation temperature tas is detected by detecting the refrigerant temperature t1 at the inlet of the evaporator 5 as in Japanese Patent Publication No. 56-16353, without using the pressure sensor 8 as in this embodiment.
It may also be a.

On the other hand, the refrigerant pressure Pex of the expansion valve 4 detected by the pressure sensor 9 is determined by the pressure-temperature conversion circuit (2) in the control circuit 10.
The saturation temperature t of the refrigerant corresponding to its pressure PeX at IOC,
, , and the temperature t,! , refrigerant temperature t of the expansion valve 4 detected by the temperature sensor 6, ! is the output signal of the refrigerant subcooling degree 5Cex (j ezs j ex) of the differential amplifier circuit (2) 10 d and the expansion valve 4.

Next, the control method of the present invention will be explained with reference to the flowchart shown in FIG.

First, when the mode determination circuit 10 determines that the rate of change Δ5Hex of the degree of subcooling 5Cex of the refrigerant at the inlet of the expansion valve 4 is less than or equal to the predetermined value Δ5Cex for a predetermined time, it is the same as in the prior art Japanese Patent Publication No. 56-16353. The first control means 10f drives the pneumatic expansion valve 4 and controls the flow rate of refrigerant in the cycle.

Next, when the rate of change Δ5Cex of the inlet refrigerant supercooling degree 5Cex of the expansion valve 4 is equal to or greater than a predetermined value ΔS Cexo for a predetermined time, the electric expansion valve 4 is controlled by the second control means selected by the mode determination circuit 10e. drive and control the refrigerant flow rate within the cycle.

During control by this second control means, the degree of subcooling of the refrigerant is 5Ce.
Amount of change in x over time (dsc ex/d t)
Accordingly, the opening degree of the expansion valve 4 is increased to control the refrigerant flow rate so as to promote refrigerant supply to the evaporator.

Therefore, when the cooling fan 13 that sends cooling air to the condenser 2 is controlled intermittently, such as in an automobile air conditioner, depending on the operating conditions, the cooling air increases rapidly and the high-pressure side pressure of the refrigeration cycle suddenly decreases. Even if the refrigerant supercooling degree SHe at the outlet of the evaporator 5 changes, this pressure change changes to the refrigerant superheating degree SHe at the outlet of the evaporator 5. Without waiting for an upward change, the expansion valve 4 is set to the first position according to dscex/dt.
The control means opens the control 11-g, thereby promoting the supply of refrigerant to the evaporator 5 and preventing the cooling capacity from being significantly reduced as in the prior art.

A concrete example of this is shown in FIG. This figure shows the results of a cool-down experiment in an automotive air conditioner. First, immediately after the start of operation, the amount of heat dissipated from the engine cooling water cooling radiator 12 installed downstream of the condenser 2 is small, so cooling 7A/13fl is turned off and the condenser 2 is operated only by the wind from the vehicle. cooled down. When the cooling water temperature rises to a predetermined value as the vehicle is operated, and the cooling fan 13 turns on at time t, the heat dissipation capacity of the condenser 2 rapidly increases, so the pressure on the high pressure side rapidly decreases, and the water is cooled. Since the liquefied refrigerant temporarily accumulates inside the condenser 2 whose temperature has become low, the degree of subcooling of the refrigerant in the expansion valve 4 decreases rapidly. Here, in the present invention, this change (-dsc ex
/dt) at time t.

to tb, in order to control the opening of the expansion valve 4 in the direction of opening, the refrigerant superheat degree signal 8He Vc at the evaporator outlet is always maintained.
Therefore, more refrigerant is supplied to the evaporator 5 more quickly than in the conventional control technology. Therefore, an abnormal increase in the degree of superheating SHe of the refrigerant at the evaporator outlet, which occurs after a sudden pressure decrease, can be suppressed, so that an abnormal decrease in cooling capacity can be prevented compared to the prior art.

In the above embodiment, the degree of supercooling 5Cex calculated from both the temperature Tex of the inlet refrigerant of the expansion valve 4 and the pressure Pex was used as the input signal for the detection signal of the second cape control means. As shown in FIG. 2, control may be performed only by either the temperature Tex of the expansion valve 4, which varies depending on the cooling fan/operation, or the pressure Pex.

Furthermore, when the degree of subcooling S/Cex of the refrigerant at the inlet of the expansion valve 40 reaches a saturated state, saturated gas is mixed into the liquid refrigerant, so the degree of dryness X of the refrigerant at the inlet of the expansion valve 4 is as shown in FIG. In order to make sure that the change occurs as shown in Fig. 1, this change is detected by the change in capacitance of the refrigerant between the electrodes of which opposing electrodes are arranged at the inlet of the expansion valve, for example, as described in JP-A No. 56-119474.
Control means may also be provided.

[Effects of the Invention] According to the present invention, when the refrigerant pressure suddenly decreases, the valve opening degree of the electric expansion valve is controlled based on the physical quantity that changes in response to the pressure change. Responsiveness is improved, and it is possible to prevent the air temperature at the evaporator outlet from rising during the transient state of the refrigeration cycle as described above.

[Brief explanation of the drawing]

Figure 1 is a system configuration diagram that is an embodiment of the present invention;
The figure is a flowchart for explaining the controllability of the refrigeration cycle in FIG. 1, and FIG. 3 is a graph showing an example of experimental results showing changes in the state of the refrigeration cycle. 1...Compressor, 1a...IIl, a gratch, 2.
... Condenser, 3... Liquid reservoir, 4... Electric expansion valve,
5... Evaporator, 6° 7... Temperature sensor, 8,9...
・Pressure sensor, 10°°° control circuit, 12... radiator, 13... cooling fan. 1 prisoner, 20 prisoners, 3 prisoners

Claims (6)

[Claims] 1. In a refrigeration cycle control device that has an electric expansion valve that controls the refrigerant flow rate by changing the valve opening degree using an electric signal, the valve opening degree of the electric expansion valve is changed according to the degree of superheating of the refrigerant at the outlet of the evaporator. a first control means for controlling the flow rate;
The invention is characterized by having a second control means that operates when the pressure of the refrigerant at the inlet of the expansion valve suddenly decreases and controls the opening degree of the expansion valve in accordance with a change in a physical quantity caused by the sudden decrease in the pressure of the refrigerant. Refrigeration cycle control device. 2. A control device for a refrigeration cycle, wherein the physical quantity according to claim 1 is a degree of supercooling of a refrigerant at an inlet of an expansion valve. 3. A control device for a refrigeration cycle, wherein the physical quantity according to claim 1 is the pressure of refrigerant at an inlet of an expansion valve. 4. A control device for a refrigeration cycle, wherein the physical quantity according to claim 1 is the temperature of the refrigerant at the inlet of the expansion valve. 5. A control device for a refrigeration cycle, wherein the physical quantity according to claim 1 is the degree of dryness of the refrigerant at the inlet of the expansion valve. 6. A refrigeration cycle control device according to claim 5, wherein the degree of dryness is detected by a change in capacitance of the refrigerant.