JPH11281222A - Controller of quantity of refrigerant circulating in open show case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of times of start and stoppage of a compressor, by controlling the aperture of an electric expansion valve and controlling the quantity of a refrigerant circulating in a refrigerant circuit, and keeping the quantity of a refrigerant constant at a set temperature within a refrigerator, and adjusting the temperature of the refrigerant at the outlet of an evaporator at a proper temperature. SOLUTION: A refrigerant pressurized and liquefied with a compressor 1 and a condenser 3 is depressurized with an electric control valve whose aperture is controllable with a pulse motor, and is evaporated and gasified with an evaporator 4, and again it is sucked with a compressor 1. The control of the aperture of this expansion valve 5 is performed by relating the two factors of the in-refrigerator temperature of an open case arid the overheat degree of the refrigerant at the outlet of the evaporator to each other. The 0 origin production of the pulse motor, that is, the origin production where the valve part comes to full close position is made at the time of turning on the power of the refrigerant circuit and the time of reopening of the cooling after finish of defrost. A controller outputs the planned number of pulses as initial aperture to the expansion valve 5, and operates and stores the differences between the set in-refrigerator temperature and the degree-of-overheat lower limit value and the actual in-refrigerator temperature and the temperatures detected by the evaporator inlet and outlet refrigerant detection means 6 and 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling the amount of circulating refrigerant in a refrigerant circuit of an open showcase using an electric expansion valve whose opening can be adjusted.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional open-showcase refrigerant circulation amount control device.
Is a low pressure switch, 3 is a condenser, 4 is an evaporator, 11 is a temperature type expansion valve connected to the inlet side of the evaporator 4, 12 is a liquid pipe solenoid valve provided on the inlet side of the temperature type expansion valve 11. , 13
Is an evaporator outlet gas temperature detector for detecting the outlet gas temperature of the evaporator 4. Reference numeral 8 denotes a temperature sensor in the refrigerator, and 14 denotes a control device for controlling the liquid pipe solenoid valve 12 based on a signal from the temperature sensor 8 in the refrigerator.

Next, the operation will be described. FIG. 6 shows FIG.
3 is an operation flow of the conventional open showcase refrigerant circulation amount control device shown in FIG. Hereinafter, the operation flow shown in FIG. 6 will be described. The temperature-type expansion valve 11 opens the valve when the outlet gas temperature of the evaporator 4 is higher than a set value based on a signal from the outlet gas temperature detector 13 for detecting the outlet gas temperature of the evaporator 4 to circulate the refrigerant. When the outlet gas temperature of the evaporator 4 is smaller than the set value, the valve is closed, and the operation is performed so as to reduce the amount of circulating refrigerant, so that the outlet gas temperature of the evaporator 4 is stabilized at the set value. Adjust the valve opening to perform

The control device 14 determines whether the store where the open showcase is installed is open or closed, for example, based on the ON / OFF state of a lighting switch. The signal from the sensor 8 is compared with a preset temperature inside the store during opening,
When the temperature detected by the inside temperature sensor 8 becomes equal to or lower than the set inside temperature during opening of the store, a signal is output to close the liquid pipe solenoid valve 12 and the refrigerant circulation is shut off.

Further, when the detected temperature of the internal temperature sensor 8 rises by a predetermined differential value from the set internal temperature during opening of the store, the control device 14 controls the liquid pipe solenoid valve 1.
A signal is output to open the second solenoid valve 2, and the liquid pipe solenoid valve 12 is controlled to circulate the refrigerant.

When the store is currently closed, the control device 14
The temperature detected by the inside temperature sensor 8 is compared with a preset inside temperature when the store is closed, and the same control as during the opening of the store is performed. The reason that the inside temperature is set to a different value between when the store is opened and when the store is closed is that, when the store is closed, there is a reduction in load such as radiant heat of lighting caused by turning off the lighting. This is to prevent the temperature of the product placed in the refrigerator from becoming too low as compared to when the store is open.

The operating pressure of the compressor 1 fluctuates due to the valve opening of the temperature type expansion valve 11 controlled as described above and the opening and closing of the liquid pipe solenoid valve 12, the liquid pipe solenoid valve 12 is closed, and the refrigerant circulates. May be stopped by the operation of the low pressure switch 2 when the power supply is shut off.

FIG. 7 shows changes in the temperature of the open showcase compartment, the degree of superheat at the evaporator outlet, and the compressor suction pressure by the conventional open showcase refrigerant circulation amount control device shown in FIGS. It is shown.

[0009]

Since the conventional open-showcase refrigerant circulation amount control device is constructed as described above, the amount of refrigerant circulation in the refrigerant circuit keeps the degree of superheat of the refrigerant at the evaporator outlet constant. It is controlled by adjusting the opening degree of the temperature type expansion valve and opening and closing the liquid pipe solenoid valve based on the temperature inside the refrigerator. Since the opening and closing of the valves are performed independently without being related to each other, the relationship between the adjustment of the internal temperature and the control of the refrigerant circulation amount is only the opening and closing operation of the liquid pipe solenoid valve.
There is a problem that the fluctuation range of the internal temperature must be equal to or larger than the differential value for opening and closing the liquid pipe solenoid valve.

[0010] Further, since the low pressure switch is actuated by the fluctuation of the operating pressure of the compressor due to the opening and closing of the liquid pipe solenoid valve, and the compressor is started and stopped, the operation of the compressor is unstable and inefficient. There was a problem of becoming.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is intended to stably maintain the internal temperature at a set temperature, minimize the fluctuation range of the internal temperature, and reduce the compressor temperature. It is an object of the present invention to obtain an open-showcase refrigerant circulation amount control device capable of reducing the number of times of start / stop of the compressor, stabilizing the operation state of the compressor, and improving the operation efficiency.

[0012]

In order to achieve the above object, the present invention firstly comprises a compressor, a condenser, a decompression expansion mechanism and an evaporator which are sequentially connected. In an open showcase refrigerant circuit provided with a degree-adjustable electric expansion valve, provided is a temperature detecting means for detecting the internal temperature of the open showcase, the evaporator inlet refrigerant temperature, and the evaporator outlet refrigerant temperature, further comprising: A control device for detecting and calculating the current inside temperature and the degree of superheat (current refrigerant temperature difference between the inlet and outlet of the evaporator) based on an input signal from the temperature detecting means is provided, and the control device is opening a store where an open showcase is installed. Means for judging whether the store is closed or not, selecting a set inside temperature and a superheat degree lower limit of different values which are preset depending on whether the store is currently open or closed. Deviation inside temperature and the set temperature and calculates the deviation between the current superheating degree and superheat lower limit,
A control method is selected from among a plurality of opening control methods of the electric expansion valve that are predetermined according to the deviation of the internal temperature and the deviation of the superheat degree, and the opening degree of the electric expansion valve is selected. By controlling the amount of circulating refrigerant in the refrigerant circuit by controlling, the amount of circulating refrigerant in the refrigerant circuit keeps the temperature in the refrigerator constant at the set temperature, and the degree of superheat of the refrigerant at the evaporator outlet is an appropriate value. It is adjusted to become.

Secondly, an evaporator outlet refrigerant pressure detecting means is provided in place of the evaporator inlet refrigerant temperature detecting means, and the control device converts the pressure signal input from the pressure detecting means into a saturation temperature corresponding to the pressure. Then, by calculating the superheat degree and the temperature signal input from the evaporator outlet refrigerant temperature detection means, the refrigerant superheat degree control of the evaporator outlet, the evaporator outlet refrigerant pressure is detected by the pressure detection means Can be controlled by the value converted to the saturation temperature.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows an apparatus for controlling the amount of refrigerant circulating in an open showcase according to the present invention.
Is a condenser, 4 is an evaporator, 5 is an electric expansion valve connected to the inlet side of the evaporator 4, and in this embodiment, it is a pulse motor driven electric expansion valve.

6 is a means for detecting the refrigerant temperature at the inlet of the evaporator 4, 7
Is a means for detecting the refrigerant temperature at the outlet of the evaporator 4, 8 is a means for detecting the temperature in the refrigerator, 9 is a means for determining whether the store in which the open showcase is installed is open or closed, This is a control device that receives signals from the refrigerant temperature detecting means 6 and 7 and the internal temperature detecting means 8 as inputs, calculates an opening adjustment amount of the electric expansion valve 5, and outputs an opening control signal.

Next, the operation will be described. First, FIG.
The refrigerant flow in the refrigerant circuit shown in FIG. 1 is described. The refrigerant pressurized and liquefied in the compressor 1 and the condenser 3 is decompressed by an electric expansion valve 5 whose opening can be adjusted by a pulse motor, and It is evaporated and vaporized and sucked into the compressor 1 again. As described above, the circulation amount of the refrigerant circulating in the refrigerant circuit is controlled by the opening degree of the electric expansion valve 5, and the present invention controls the opening degree of the electric expansion valve by controlling the temperature in the open showcase chamber and the temperature. The two factors of the superheat degree of the refrigerant at the evaporator outlet are performed in association with each other.

The opening degree of the electric expansion valve 5 is controlled by a control device 9.
Hereinafter, a specific control method of the control device 9 will be described with reference to FIG.

First, at the start of the cooling of the open showcase, the zero point of the pulse motor for adjusting the opening of the electric expansion valve is set, that is, the base point at which the valve section is in the fully closed position is set. Note that the start of cooling refers to the time when the power of the refrigerant circuit is turned on and the time when cooling is restarted after the defrost of the open showcase, which is performed at a constant cycle.

After completion of the zero base point output, a predetermined number of pulses as an initial opening is output to the motor-operated expansion valve 5, which is also maintained at the initial opening for a preset time, and then the evaporator inlet / outlet refrigerant is maintained. The signals of the temperature detecting means 6, 7 and the internal temperature detecting means 8 are input, and the temperature of the internal temperature detecting means 8 is calculated by calculating the difference between the current internal temperature Ta and the evaporator inlet / outlet refrigerant temperature detecting means 6, 7. Is stored as the current degree of superheat SH.

Here, the control device 9 determines whether the store in which the open showcase is installed is open or closed. For example, the control device 9 inputs the opening time and closing time using a timed timer or There are various methods such as automatic or manual changeover switch operation, and discrimination by lighting ON / OFF.

If the store is currently open, the control device 9 compares the set internal temperature a and the superheat degree lower limit value b during the store opening with the current internal temperature Ta and the current superheat degree SH, and calculates a deviation ΔTa ,
Calculate ΔSH. Further, if the store is currently closed, the set inside temperature c and the superheat degree lower limit d, which are different from those during the opening of the store, are compared with the current store temperature Ta and the current superheat degree SH, and each deviation Δ
Ta and ΔSH are calculated. In the following, the opening change pulse number ΔPuls of the electric expansion valve 5 is based on the difference ΔTa of the internal temperature and the difference ΔSH of the degree of superheat both during opening and closing.
e is calculated by a different calculation method according to the current state as follows.

First, when the deviation ΔTa of the internal temperature is equal to or larger than the first deviation A set in advance, rapid cooling is required, for example, at the time of pull-down, so that the current superheat is lower than the superheat degree lower limit b or d. ΔPulse is determined so that ΔSH = 0 so as to ensure the maximum refrigerant circulation amount within a range where the degree SH does not decrease.

Next, the deviation ΔTa of the internal temperature becomes smaller than the first set deviation A, and the second predetermined deviation A is determined.
If the deviation ΔSH of the degree of superheat is not less than 0 and the deviation ΔSH of the degree of superheat is not less than 0, the current internal temperature is within a predetermined range from the set internal temperature, and the current superheat degree is equal to or higher than the superheat degree lower limit value. Since it is in a stable state, ΔPulse = 0 is determined so that the current opening degree of the electric expansion valve 5 is maintained.

Furthermore, if the deviation ΔTa of the internal temperature is A> ΔTa ≧ B as in the above condition, but the deviation ΔSH of the superheat degree is less than 0, the load and the refrigerant circulation amount are not well balanced, so that ΔSH = 0. ΔPulse is determined as follows. In addition,
In this case, the opening of the electric expansion valve 5 is controlled in the closing direction.

Further, when the deviation ΔTa of the internal temperature becomes smaller than the second set deviation B, ΔPulse is determined so that the current internal temperature Ta = the set internal temperature a or c. In this case as well, the degree of opening of the electric expansion valve (5) is controlled in the closing direction.

As described above, the control device 9 calculates the deviation ΔTa of the internal temperature and the deviation ΔSH of the degree of superheat based on
The pulse change amount ΔPulse of the electric expansion valve 5 is determined by a control method suitable for the current state. The set deviations A and B are determined as, for example, A = 0.5, B = −0.5. For example, the control device 9 operates to maintain the internal temperature Ta in the range of the set internal temperature a or c ± 0.5 deg. Further, it is desirable that the set internal temperature c at the time of closing the store is set to about the set internal temperature a during opening of the store a + 2 deg so that the product temperature is the same between when the store is open and when the store is closed. Further, when the superheat degree lower limit b during opening of the store is about 5 deg and the superheat degree lower limit d during closing of the store is about 15 deg, a good balance between the load and the refrigerant circulation amount can be obtained.

Pulse change amount ΔPuls of electric expansion valve 5
e, the control device 9 determines the current pulse number Pulse
Is added to ΔPulse, and the changed pulse number Pulsen
ew is calculated, and the value of the Pulsenew is set to a preset pulse number lower limit value Pul of the electric expansion valve 5 in advance.
Compare with semin.

The Pulsemin is provided when the control device 9 keeps changing the opening of the electric expansion valve 5 in the closing direction, especially in the case of a light load, and the lower limit of the valve opening control of the pulse motor. Is exceeded, it is determined that the refrigerant circulation amount cannot be controlled, the electric expansion valve 5 is fully closed, and the refrigerant circulation is shut off.

If the changed pulse number Pulsenew is equal to or greater than the pulse number lower limit Pulsemin, the controller 9
Outputs a signal so that the number of pulses of the electric expansion valve 5 becomes Pulsenew, and adjusts the valve opening. The control device 9 that drives the pulse motor and adjusts the valve opening degree performs the above-described operation at predetermined intervals. However, when the pulse motor drive period is set to about 15 seconds, good control can be obtained.

Now, the pulse number Pulsenew after the change
Is smaller than the pulse number lower limit value Pulsemin, the control device 9 outputs a signal to the pulse motor so that the electric expansion valve 5 is fully closed. Thereafter, the current internal temperature Ta is detected at a predetermined cycle, and when Ta becomes higher than the set internal temperature a or c by a predetermined set differential value diff, an initial time at the time of returning from the forced full closing is set. After fixing for a predetermined time with the number of pulses set in advance as the opening degree, the operation returns to the normal control.

In the control for shutting off the refrigerant circulation by fully closing the electric expansion valve 5 as described above, the suction pressure of the compressor 1 decreases and the low-pressure switch 2 operates and the compressor 1 stops, but as described above, the control device 9 controls the opening of the electric expansion valve 5 using two factors of the internal temperature and the degree of superheat at the evaporator outlet. Since the amount of circulating refrigerant is adjusted, the frequency of the fully closed control is reduced as compared with the related art.

FIG. 3 shows the temperature in the open showcase compartment, the superheat degree at the cooler outlet, the compressor suction pressure, and the electric expansion valve by the refrigerant circulation amount control device of the first embodiment shown in FIGS. 3 shows the change in the number of pulses.

Embodiment 2 FIG. FIG. 4 shows another embodiment, wherein the means for detecting the degree of superheat of the refrigerant at the evaporator outlet is the same as that of the first embodiment.
And different. Reference numeral 10 denotes evaporator outlet pressure detecting means. The control device 9 has a function of receiving a pressure signal from the evaporator outlet pressure detecting means 10 and converting the pressure signal into a saturation temperature corresponding to the pressure.
The controller 9 determines the degree of superheat of the refrigerant at the evaporator outlet using the temperature signal input from the evaporator outlet refrigerant temperature detecting means 7 and a value obtained by converting the pressure signal input from the evaporator outlet pressure detecting means 10 into a saturation temperature. calculate. The control method is the same as that of the first embodiment, however, since an accurate evaporation temperature can be obtained by the pressure, the control accuracy is improved.

In the first and second embodiments, a pulse motor driven electric expansion valve is used. However, even if the electric expansion valve is of another driving type, the same degree of opening is used. The refrigerant circulation amount can be controlled by the adjustment method.

[0035]

As described above, the apparatus for controlling the amount of refrigerant circulated in the open showcase according to the present invention is constructed by connecting the compressor, the condenser, the decompression and expansion mechanism, and the evaporator in order.
In the open-showcase refrigerant circuit provided with a motorized expansion valve whose degree of opening can be adjusted as the pressure-reducing expansion mechanism, the temperature at which the temperature inside the open showcase, the temperature at the evaporator inlet, and the temperature at the evaporator outlet are detected. Detecting means, further provided by an input signal from the temperature detecting means,
A control device is provided for detecting and calculating the current inside temperature and the current evaporator entrance / exit refrigerant temperature difference (hereinafter referred to as the degree of superheat), and the control device determines whether the store where the open showcase is installed is open or closed. Having a preset inside temperature and a superheat degree lower limit value which are respectively set in advance depending on whether the store is currently opened or closed, and a deviation between the detected present inside temperature and the set inside temperature and Calculating the deviation between the current superheat degree and the lower limit of the superheat degree, and controlling the degree of opening of the plurality of electric expansion valves predetermined according to the deviation of the internal temperature and the deviation of the superheat degree. Select the control method from
The refrigeration cycle is controlled by controlling the opening degree of the electric expansion valve to regulate the amount of refrigerant circulating in the refrigerant circuit, thereby stabilizing the temperature in the refrigerator at a set temperature, and reducing the number of times the compressor is started and stopped. Can be stabilized.

Secondly, an evaporator outlet refrigerant pressure detecting means is provided in place of the evaporator inlet refrigerant temperature detecting means, and the control device converts the pressure signal input from the pressure detecting means into a saturation temperature corresponding to the pressure. Then, by calculating the superheat degree and the temperature signal input from the evaporator outlet refrigerant temperature detection means, the refrigerant superheat degree control of the evaporator outlet, the evaporator outlet refrigerant pressure is detected by the pressure detection means The temperature can be controlled by a value converted to a saturation temperature, and the accuracy of the internal temperature control and the superheat degree control can be improved.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram showing Embodiment 1 of a refrigerant circulation amount control device for an open showcase according to the present invention.

FIG. 2 is a control flow according to the first embodiment.

FIG. 3 is a graph showing changes in a temperature inside an open showcase compartment, a superheat degree of a refrigerant at an outlet of a cooler, a compressor suction pressure, and an opening degree of an electric expansion valve in the first embodiment.

FIG. 4 is a refrigerant circuit diagram showing Embodiment 2 of an open showcase refrigerant circulation amount control device according to the present invention.

FIG. 5 is a refrigerant circuit diagram of a conventional open showcase.

FIG. 6 shows a control flow in a conventional refrigerant circulation amount control device, in which (a) is a control flow using a temperature type expansion valve and an outlet gas temperature detector, and (b) is a control flow using a liquid pipe solenoid valve and a temperature sensor in a refrigerator. It is a flow.

FIG. 7 is a graph showing changes in the open showcase internal temperature, the cooler outlet refrigerant superheat degree, and the compressor suction pressure in the conventional refrigerant circulation amount control device.

[Explanation of symbols]

1: compressor, 2: low pressure switch, 3: condenser, 4:
Evaporator, 5: Electric expansion valve, 6: Evaporator inlet refrigerant temperature detecting means, 7: Evaporator outlet refrigerant temperature detecting means, 8: Internal temperature detecting means, 9: Control device according to the present invention, 10: Evaporator Outlet pressure detection means, 11: temperature expansion valve, 12: liquid pipe solenoid valve, 13: outlet gas temperature detector, 14: conventional control device

Claims (2)

[Claims] 1. A compressor, a condenser, a decompression and expansion mechanism and an evaporator are connected in order, and the decompression and expansion mechanism is
In a refrigerant circuit of an open showcase provided with a motorized expansion valve capable of adjusting the opening degree, a temperature detecting means for detecting a temperature inside the open showcase, an evaporator inlet refrigerant temperature, and an evaporator outlet refrigerant temperature is further provided. A control device is provided for detecting and calculating the current inside temperature and the degree of superheat (current refrigerant temperature difference between the inlet and outlet of the evaporator) based on an input signal from the temperature detecting means, and the control device opens a store where an open showcase is installed. It has a means for determining whether the store is inside or closed, and selects a set inside temperature and a superheat degree lower limit value which are respectively set in advance depending on whether the store is currently opened or closed, and detects the detected present inside temperature. And the difference between the set internal temperature and the current superheat degree and the superheat degree lower limit value are calculated, and a plurality of predetermined values are determined in advance according to the internal temperature difference and the superheat degree deviation value. An open showcase wherein a control method is selected from among the electric expansion valve opening control methods, and the amount of refrigerant circulating in the refrigerant circuit is controlled by controlling the opening of the electric expansion valve. Refrigerant circulation amount control device. 2. The refrigerant circulation amount control device for an open showcase according to claim 1, further comprising an evaporator outlet refrigerant pressure detecting means in place of the evaporator inlet refrigerant temperature detecting means, wherein the control device comprises: Wherein the pressure signal input from the evaporator is converted into a saturation temperature corresponding to the pressure, and the degree of superheat is calculated based on the temperature signal input from the evaporator outlet refrigerant temperature detecting means. Quantity control device.