JPS60185075A - Controller for flow rate of refrigerant - 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 refrigerant flow rate control device, and particularly to a refrigerant flow rate control device suitable for an air conditioner in which the heat load changes over a wide range.

[Background of the invention]

First, a conventional refrigerant flow rate control device using an expansion valve whose valve opening degree can be adjusted by an electric signal will be described with reference to FIG.

In Figure 1, 1 is a compressor, 2 is a condenser, 3 is an expansion valve whose valve opening is adjusted by an electric signal, and 4 is an evaporator.These are connected by refrigerant piping to form a refrigeration cycle. There is.

The refrigerant is compressed by the compression filter to become a high-temperature, high-pressure superheated gas, which is then cooled by the condenser 2.The refrigerant is then condensed to become a high-pressure liquid refrigerant and flows down, where the flow rate is controlled by the refrigerant flow control valve 3 and the adiabatic It expands and becomes a low-pressure refrigerant, which evaporates while taking heat from the outside in the evaporator 4 and is sucked into the compressor 1 again. In such a refrigeration cycle, a temperature sensor 5 and a pressure sensor 6 are generally installed at the outlet of the evaporator 4 in order to evaporate just the right amount of refrigerant depending on the external heat load in the evaporator 4.
Based on these signals, the degree of superheat calculation circuit 8 in the refrigerant flow rate control device 7 calculates the degree of superheat S H of the refrigerant at the outlet of the steamer 4.
I put it on. Then, use this value and the superheat degree setting circuit 9 in advance.
A differential amplifier 10 measures the deviation from the value SH” determined by
The opening degree of the expansion valve 3 is determined by the PID calculation circuit 11 according to this deviation.

A signal is sent from the valve drive circuit 12 to an actuator (not shown) of the expansion valve 3 to adjust the opening degree of the expansion valve 3 and control the refrigerant flow rate so that the deviation between SH and SH becomes zero.

Note that the degree of superheating of a refrigerant here refers to the difference between the temperature of a gas that has been superheated to a saturation temperature or higher corresponding to the refrigerant pressure at a certain point, and the saturation temperature. Therefore, in order to calculate the saturation temperature corresponding to the pressure at the outlet of the evaporator, the superheat degree calculation circuit 8 includes a strain gauge amplifier 8b that converts the pressure signal of the pressure sensor 6 into an electrical signal, and a strain gauge amplifier 8b that converts this electrical signal to the saturation temperature. It has a temperature calculation circuit 8C for converting the temperature signal of the temperature sensor 5 into an electric signal corresponding to the electric signal, and a DC amplifier 8a and a differential amplifier 8d for converting the temperature signal of the temperature sensor 5 into an electric signal and calculating the difference from the saturation temperature. It is normal to have one.

Generally, in order to effectively utilize the evaporator 4 and evaporate just the right amount of refrigerant depending on the external heat load, the refrigerant does not turn into superheated gas at the exit of the evaporator 4, and the degree of superheating reaches exactly zero. This is desirable. However, even if the heat load is small and the refrigerant does not completely evaporate in the evaporator 4 and liquid returns, the degree of superheat of the refrigerant at the outlet of the evaporator 4 is zero, so if you try to control the degree of superheat to zero, Liquid return cannot be prevented when the heat load is small, leading to disadvantageous problems in terms of durability of the compressor 1. In order to avoid this, the set value SH'' of the degree of superheat is usually set so that the degree of superheat of the refrigerant at the outlet of the evaporator 4 is around 5°C.

Conventionally, the set value SH of the degree of superheating has been set for a certain standard operating condition and kept at a constant value regardless of the heat load of the air conditioner. Therefore, when the heat load is small, it is necessary to reduce the refrigerant flow rate in order to bring the superheat degree SH closer to the set value SH, and the refrigerant flow control device 7 controls the expansion valve 3
Generates a signal to close. As a result, the expansion valve 3 is throttled and the evaporation pressure in the evaporator 4 is lowered, and the evaporation temperature is lowered, so that frost forms on the fin surface of the evaporator 4 and the performance of the evaporator 4 is reduced. Therefore, the refrigerant flow rate control device 7 further generates a signal to close the expansion valve 3 in order to bring the superheat degree SH closer to the set value SH'', and the evaporation pressure decreases more and more, and frost formation progresses.
Eventually it became uncontrollable. On the other hand, even when the heat load is large or when an increase in refrigerant flow rate is required, such as when starting up an air conditioner, the degree of superheating SH is controlled to a constant value SH, so sufficient cooling capacity can be obtained. Furthermore, when there is an overload, the flow rate of refrigerant is insufficient.
The cooling of the compressor 1 was insufficient and the temperature of the discharged gas rose abnormally, causing problems in terms of the durability of the compressor 1.

[Object of the Invention] The present invention has been made to solve the above-mentioned problems, and is capable of controlling the flow rate of refrigerant in a refrigeration cycle, without causing a shortage of cooling capacity over a wide heat load range, and without causing instability in the control system. The purpose of this project is to provide a refrigerant meteor control device that can avoid inconsistency and loss of control.

[Summary of the invention]

1'+ The refrigerant flow rate control device according to the present invention is provided with a means for detecting a heat load and a means for changing the set value of the degree of superheating of the refrigerant at the outlet of the evaporator according to the heat load. to change the set value of superheat degree.

The control circuit issues an electric signal to the expansion valve to control the refrigerant flow rate so that the degree of superheat at the evaporator outlet reaches this set value.

[Embodiments of the invention]

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

FIG. 2 shows a refrigerant flow rate control device according to an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 are the same parts as in the prior art, so the explanation thereof will be simplified.

In Fig. 2, 5 is a temperature sensor that detects the temperature of the refrigerant at the outlet of the evaporator 4, 6 is a pressure sensor that detects the pressure at the outlet of the evaporator 4, and 8 is a sensor that measures the degree of superheating of the refrigerant based on the signals of these sensors. 9 is a superheat degree setting circuit that commands the superheat degree set value, 1Φ is a differential amplifier that calculates the deviation between the measured superheat degree and its set value, and 11 is an expansion circuit based on this deviation. Control that determines the opening degree of valve 3 < P that emits g
The ID calculation circuit 12 is a valve drive circuit that issues a drive signal 41 to the actuator of the expansion valve 3 in accordance with this control signal.

In FIG. 2, there is further provided a temperature sensor for detecting negative heat 3if, and a set value calculation circuit 13 that determines the set value of the degree of superheating based on the signal of this sensor, and the output signal of this set value calculation circuit 13 is Accordingly, the superheat degree setting circuit 9 sets the superheat degree.

Next, the operation of the refrigerant flow rate control device 7 configured as described above will be explained with reference to FIGS. 3 and 4. Figure 3 shows an example in which the superheat setpoint S H'' is varied as a function of room temperature.
H' decreases in proportion to the decrease in Tr, and when Tr reaches the set value T
When r + is larger than Tr, and when it is smaller, SH" is a constant value Sl+.

When Tr is larger than Tr, SH decreases in proportion to the increase in Tr. In order to generate such a change pattern of Sll'', an arithmetic circuit may be configured according to the arithmetic flow shown in FIG.

That is, the signal Tr of the room temperature sensor 14 and the set value Tr are compared with a comparator (not shown), and if Tr < Tr, then SH" = SH", - is calculated as 1 (Trt - Tr). Turn on SH with the circuit. Go r.

When < T r < T r2, SH"=SH",
When constant, Tr, and when <Tr, SH=SH.

-, add S H" with (Tr-Tr,). Here,
, KI2 is a proportionality constant, SH,.

Like Tr, , Tr, it can be freely set using a potentiometer or the like. These values can be set depending on the air conditioning system.

By configuring the set value calculation circuit 13 in this way and configuring the superheat degree setting circuit 9 to set the degree of superheat according to the calculation result of this circuit, the overload can be reduced and the room temperature Tr can be lowered. When the temperature drops below Tr, the set value SH of the degree of superheating decreases to prevent the expansion valve 3 from throttling too much, so stable control is possible even at low heat loads, but on the other hand, when the heat load increases, .

When Tr becomes larger than Tr, SH" decreases and the opening degree of the expansion valve 3 increases, so the refrigerant flow also increases, resulting in insufficient cooling capacity, abnormal rise in the discharge gas temperature of the compressor 1, etc. Note that when the room temperature is larger than T r and smaller than G r2, there is no problem even if the control is performed using the conventional set value.

FIG. 5 shows another embodiment of the present invention, which is different from the embodiment shown in FIG. This is different from the embodiment shown in Fig. 2 in that the microcomputer has a CPU 5 and a memory unit 16.
, and an AD converter 17. Temperature sensor 14
The room temperature signal detected at are respectively 19a with superheat level A.
and 1.9b, is converted into a digital signal by the AD converter 17, and then processed by the CPU. The CPU calculates the degree of superheating based on these iFf numbers, calculates the deviation from the set value, performs PII:) calculation, determines the valve opening degree, and outputs a signal to the valve drive circuit 12. The output signal of the valve drive circuit 12 is sent from the output boat 20 to the actuator of the expansion valve 3 to control the flow rate. With this configuration, the calculations shown in FIG. 4 can be processed on a program without configuring an arithmetic circuit, so that the calculation formula can be easily changed. In addition, patterns that are difficult to construct using conventional arithmetic circuits, such as the one shown in Figure 5, can be created using the SH at the point marked 0 in the figure.
” corresponds to the value of Tr, a memory map is created on the memory unit 16, and for any value of Tr, SH
Since the value of `` can be interpolated and used on the CPU, more accurate meteor control is possible. Fig. 6 shows another example of Fig. 4, and the air conditioner design point room temperature is 1. When the room temperature is lower, the design value of the degree of superheating Sl This embodiment differs from the embodiment shown in FIG. 4 in that the flow rate can be controlled immediately in response to heat loads other than the heat load.

FIG. 7 is a diagram of a cold<Is flow control device according to another embodiment of the present invention. The temperature sensor 4 is installed at the gas discharge part of the compressor 1, and the temperature sensor 4 is taken in from the heat load 1a, as shown in FIGS. 2 and 4. This is different from the embodiment shown in FIG. Detect the discharge gas temperature of compressor 1; f! As a method of changing the setting value of 1 degree per heat, the calculation shown in FIG. 8 may be performed by the CPU.

That is, when the constant value SH of the degree of superheating is initially set to SH, and the discharge gas temperature signal Tel taken in from the thermal load signal input port 18 is smaller than a predetermined value T, the coefficient C is set to 1. ,] When d is thicker than Td, C
=1-, 5 ('rcl-Td) and 5r9<. The value obtained by multiplying this coefficient C by S H, b H'' S H As shown in FIG. 9, since SH decreases in proportion to the increase in Td, the amount of refrigerant circulation increases and an abnormal increase in the gas discharged from the compressor 1 can be prevented. Here, the change pattern of S H” in Fig. 9 is as follows:
Similarly to FIG. 5, it may be stored in the memory unit 16 as a memory map.

FIG. 10 shows a temperature sensor 14a according to another embodiment of the present invention.
5 and 7, the temperature sensor 14b detects the indoor temperature, the temperature sensor 14b detects the discharge gas temperature of the compressor 1, and these signals are input from the thermal load signal input ports 18a and 18b, respectively. Different from the example. FIG. 11 shows an example of a method for setting the degree of superheat in the refrigerant flow rate control device of this example. In this embodiment, when the room temperature Tr is smaller than the set value Tr, the set value SH of the superheat degree is set to Tr.
decreases in proportion to the decrease in Tr, and T
When Tr is smaller than r2, it is maintained at a constant value SH"=SH, and when Tr is larger than Tr, SH decreases in proportion to the increase in Tr, which is similar to the embodiment shown in FIG. It is.

The embodiment shown in FIG. 11 further differs from the embodiment shown in FIG. 4 in that SH, which is determined by the room temperature Tr, is multiplied by a coefficient C, which is determined by the discharge gas temperature Td of the compressor 1. With this configuration, as shown in FIG. 12, the compression i
When the discharge gas temperature of the compressor] is larger than the set value d9, the coefficient C is multiplied by pattern (B), which is a number smaller than l, which decreases in proportion to the increase in Td. When the discharge gas temperature is lower than God*, the indoor temperature is 1゛r.
Accordingly, the set value SI of the superheat degree is determined, and Td becomes
When it is larger, this signal is prioritized and C3I-1* is determined, and the degree of superheating can be set according to the room temperature Tr without causing an abnormal rise in the compressor discharge gas temperature.

FIG. 13 shows an embodiment of the inventionless pond, in which a temperature sensor 14 is installed at the air outlet of the evaporator 4, measures the temperature of the air cooled by the evaporator 4, and sends this signal to the heat load input point. -1-
This is different from the other embodiments in that the data is imported from ``8''. With this configuration, especially when using an automobile compressed air conditioner to increase the indoor temperature by +11!1 m by using a heater (not shown) during intermediate seasons such as spring and autumn, or when the rotation speed of compression [1] When the temperature increases, a decrease in the evaporation temperature of the evaporator 4 can be detected, which has the effect of preventing frost formation and freezing of the fins 21.

FIG. 14 is another embodiment of the present invention, which differs from the embodiment shown in FIG. 13 in that a temperature sensor 14 is installed on the surface of the fin 21. With this configuration, the temperature of the fins 21 is directly detected, which is more effective in preventing the fins 21 from freezing.

FIG. 15 shows another embodiment of the present invention, in which the inlet refrigerant temperature of the evaporator 4, that is, the evaporation temperature, is detected by a temperature sensor 5b and taken in from a heat load signal input boat.
This is different from the embodiment shown in the figure. With this configuration, the state of the heat load is directly detected as the evaporation temperature, so the heat load actually acting on the evaporator can be detected, allowing highly accurate flow rate control.

FIG. 16 shows another embodiment of the present invention, which differs from the embodiment shown in FIG. 15 in that the signal from the pressure sensor 6 installed at the outlet of the evaporator 4 is used instead of the evaporation temperature signal. Even with this configuration, the same control as the embodiment shown in FIG. 15 is possible, and there is an advantage that the number of sensors can be further reduced.

FIG. 17 shows another embodiment of the present invention, in which a temperature sensor 5a provided at the evaporator 4 outlet and a temperature sensor 5b provided at the evaporator 4 outlet are used to superheat the refrigerant at the evaporator 4 outlet. This embodiment differs from the embodiments shown in FIGS. 15 and 16 in that the temperature is determined and the evaporation temperature signal detected by the temperature sensor 5b is input from the total heat load signal input port 18.

With this configuration, the number of sensors can be reduced compared to the embodiment shown in FIG. 15, and compared to the embodiment shown in FIG. Flow rate control becomes possible without using a circuit.

According to the present invention, even if the heat load changes, the set value of the degree of superheat can be changed accordingly, so that control cannot be achieved when the heat load is small and when the heat load is large. This has the effect of making it possible to control the refrigerant flow rate over a wide heat load range without causing insufficient cooling capacity.

The above example is effective in a steady state where the operating condition of the nitrogen air conditioner (nitrogen air conditioning) fD device does not change suddenly, but it is effective in the initial stage of cool-down (immediately after the air conditioner is started) in an automobile sudden air conditioner. When the temperature in a single chamber is extremely high and it is necessary to lower the temperature in the single chamber quickly, it is more effective to reduce the evaporation temperature in the evaporator by slightly restricting the expansion valve. . This is because in a transient state such as the initial stage of cooldown, the amount of heat absorbed by the refrigerant flowing inside the evaporator from the evaporator is different from the amount of heat absorbed by the evaporator from the air inside the vehicle, and the evaporator is first cooled by the refrigerant. This is because the air is then cooled by the cooled evaporator. In other words, at the beginning of cool-down, the temperature of the evaporator is also a factor, so in order to cool the air, it is first necessary to quickly cool the evaporator.To do this, it is necessary to lower the evaporation temperature of the refrigerant and reduce the temperature difference with the evaporator. This is because there is a need to increase the degree of superheat.In the refrigerant flow rate control device described in the embodiment of the present invention, in order to reach the limit of full expansion, it is sufficient to increase the set value of the degree of superheat. As shown in Fig. 18, the average temperature inside the vehicle decreases faster in the early stage of cool-down in case a, which has a higher superheating degree set value, but the evaporator also cools down sufficiently after the nitrous air control Oroiso is activated. If you lower the superheat setting and increase the refrigerant flow rate by opening the #b, the interior of the vehicle will cool down well.

Therefore, more effective refrigerant current control can be achieved by increasing the set value of the degree of superheat at the initial stage of cool-down, and switching to the control method described above when the temperature inside the single chamber becomes low. FIG. 19 shows an example of control in which the set value of the degree of superheat is increased in the early stage of cool-down, and the control shown in FIG. 4 is combined. Here, Trx < Tr2 (Tr31 SHo'
<sH1', and when the average vehicle interior temperature Tr is higher than Tr3 at the beginning of cool-down, the superheat degree setting value SHK is set to SHK.
HI', and when Tr becomes smaller than Tr3, the control is switched to the one shown in FIG. As a signal for switching between control to increase the superheat degree set value at the initial stage of cool-down and the control method described above, in addition to the vehicle interior temperature, the difference between the vehicle interior temperature and the set value (Tr - Tr2 or Tr
-Tra), evaporation temperature, evaporator temperature or evaporation pressure can be used to similar effect. FIG. 20 shows an example in which the evaporation temperature is fully switched No. 1g. other than this,
As shown in FIG. 21, the set value of the degree of superheat may be increased within a certain period of time after the air conditioner is started.

〔Effect of the invention〕

According to the invention, even if the heat load changes, the set value of the degree of superheat can be changed accordingly, so there is no control when the heat load is small, and when the heat load is large. ! ? Control of refrigerant flow rate over a wide heat load range without causing insufficient room capacity
It has the effect of making money possible.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional refrigerant flow rate control device, FIG. 2 is a configuration diagram of a refrigerant flow rate control device according to an embodiment of the present invention, and FIG.
The figures are diagrams showing control patterns according to the embodiment of Fig. 2, and Fig. 4.
The figure shows the flow of the calculation, FIG. 5 shows the configuration according to another embodiment of the present invention, FIG. 6 shows another control pattern, FIG. 7 shows the configuration of another embodiment, and FIG. Figures 8 and 9 show the calculation flow and control pattern of the embodiment shown in Figure 7.
FIG. 11 is a block diagram of another embodiment of the present invention. 12 is a diagram showing calculation float control patterns according to the embodiment of FIG. 10, FIG. 13, and FIG. 14. FIG. 15, FIG. 16, and FIG. 17 are all configuration diagrams of a refrigerant flow rate control device according to still another embodiment of the present invention. Fig. 18 is a diagram illustrating the influence of the superheat degree setting value on the change in cabin temperature at the beginning of cool-down, Fig. 19 is an example of control for increasing the superheat degree setting value at the early stage of cool-down, and Fig. 20 , FIG. 21 is a diagram illustrating another embodiment of the present invention. 1... Pressure m machine, 3... Expansion box, 4... Evaporator, 5
°°゛Temperature sensor, 6... Pressure sensor, 7... Refrigerant flow rate control device, 8... Superheat degree calculation circuit, 9... Superheat degree setting circuit, 13゛°° Set value calculation circuit, 14 ...Temperature sensor, 15...CPU, 16...Memory unit, 17...AD converter, 18...Heat load signal manual boat, 19...Superheat degree signal input boat, 20...・
Output boat, 21...fin. T 1 Figure 1ρ 2nd Figure L--1----------/4 Figure 3 of Showa 4 Figure Z5 Figure L-1------------Go 4 ¥16 Fig. 7 Fig. 6 ■ 9 Fig.￥l lo Fig. ■ 11 Fig. 1z Ward Tn Trz Tr and Ta whisper 13 Fig. Tomi /4 Fig. 115 Fig. 17 1 (1 circle)

Claims (1)

[Claims] 1. An evaporator in an air conditioner comprising a compressor, a condenser that condenses refrigerant, an expansion valve whose valve opening degree can be adjusted by an electric signal, and an evaporator that evaporates refrigerant. It consists of a means for detecting the degree of superheat of the refrigerant at the outlet, and a control circuit that issues the expansion valve and an electric signal to maintain the degree of superheat at a set value, and the set value of the degree of superheat is controlled by the operating state of the air conditioner. A refrigerant flow rate control device that changes the flow of refrigerant according to the flow of refrigerant.゛2.When the heat load is larger than the set value, the set value of the degree of superheat is decreased as the heat load increases, and when the heat load is smaller than the set value, the degree of superheat is decreased as the heat load decreases. The refrigerant flow rate control device according to claim 1, characterized in that the set value is decreased. 3. Claim 2, characterized in that the indoor air temperature is detected as means for detecting the heat load of the air conditioner.
The refrigerant flow rate control device described in Section 1. 4. When the indoor air temperature is within a certain range, the set value of the degree of superheat is kept constant, and when the indoor air temperature is higher than this range, the set value of the degree of superheat is decreased as the indoor temperature increases. and when the indoor air temperature is lower than the range, the set value of the degree of superheating is lowered as the indoor air temperature decreases. . 5. When the compressor discharge gas temperature is below a certain value, the set value of the degree of superheating of the evaporator outlet refrigerant is kept constant, and when the compressor discharge gas temperature is higher than the constant value, this compressor discharge gas The refrigerant flow rate control device according to claim 1, wherein the set value of the degree of superheat is decreased as the temperature increases.