JPH01212867A - Refrigerating device - Google Patents

Abstract

PURPOSE:To improve the response property of the opening and closing of an electric expansion valve, by a method wherein a pulse width modulating signal with a proper frequency, avoiding the resonance frequency of a spring, is produced based on the signals of a temperature sensor and a temperature setting unit while a valve opening degree regulating unit, which controls the opening degree of the valve by the pulse width modulating signal, is provided in the title device. CONSTITUTION:A valve opening degree regulating unit 15 receives signals from room temperature sensors 10, 11 and a temperature setting unit 20, setting the room temperatures at desired temperatures, and produces a pulse width modulating signal, in which an ON/OFF duty ratio is changed based on a relation between these signals, to control a refrigerant flow rate control valve 14. The refrigerant flow rate control valve 14 is provided with a characteristic, in which the hysteresis width of a magnetic core, magnetized by a solenoid constituting a part of the valve 14, is increased with respect to the smooth change of an impressing voltage, and the hysteresis width of the same becomes wider with respect to a periodic change as the period of the same becomes shorter, while this characteristics is one of reasons to delay the response property of valve opening degree changing with respect to a signal. Therefore, the frequency of the valve opening degree regulating unit 15 is set based on the consideration of the resonance frequency of a spring when the impressing voltage is changed periodically, in order to make the hysteresis width small.

Description

[Detailed Description of the Invention] [Object of the Invention] Industrial Field of Application The present invention relates to a refrigeration system that controls the temperature of a low-temperature refrigerator. This invention relates to a refrigeration system with an improved control device for cooling.

2. Description of the Related Art There are several types of valves for controlling the flow rate of refrigerant, and among them, an electric expansion valve is well known for its excellent responsiveness. As this electric expansion valve,
There are those that use a motor to adjust the valve opening, and those that adjust the valve opening by changing the force applied to a spring connected to the valve.

In the present invention, the latter valve is adopted, and examples of the latter valve include Japanese Patent Publication No. 60-56983 and Japanese Patent Publication No. 60-56983.
There is a publication No. 0-34037. Special Public Service No. 60-56983
In the publication, a change in temperature on the evaporator outlet side is converted into an electrical signal, and the opening degree of the valve is adjusted using this electrical signal. On the other hand, in Japanese Patent Publication No. 6G-34037, when the compressor is started, the electric expansion valve is operated until the electricity and signal from the third temperature sensor provided at the condenser inlet or intermediate portion reach a predetermined value. The control circuit outputs a signal to fully open the valve.

Problems to be Solved by the Invention The aforementioned Japanese Patent Publication No. 60-56983 does not describe in detail what type of electrical signal is used to change the opening degree of the expansion valve, and the controller thereof cannot be specified. On the other hand, in Japanese Patent Publication No. 60-34037, when the compressor is started after being stopped for a long time,
The control circuit outputs a signal to fully open the expansion valve until the electric signal from the temperature sensor installed in the condenser reaches a predetermined value, making it possible to start the engine in an extremely stable manner. However, the control circuit is not configured to improve the responsiveness of the expansion valve to the applied voltage.Therefore, in both publications, improvements are made to improve the responsiveness of the electric expansion valve to signals. However, although the control signal is quickly changed in response to temperature changes, there is a problem in that it is not reflected in the speed at which the valve opening is changed.

Therefore, the present invention is an electric expansion valve in which a solenoid generates a force to be applied to a spring connected to the valve, and the cause of the poor response of opening and closing the valve is the hysteresis of the magnetic core that is completely magnetized by the solenoid. Focusing on this, our technical challenge is to reduce this hysteresis width.
The object of the present invention is to provide a refrigeration system that includes a control device (valve opening adjustment section) that sends out a signal that reduces the hysteresis width.

[Structure of the invention]

Means for Solving the Problems The present invention provides a refrigeration system in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected by pipes in an annular manner. a refrigerant flow control valve whose opening degree changes and controls the refrigerant flow rate;
a temperature sensor that detects the temperature in the room cooled by the refrigeration device; a temperature setting section that sets a desired indoor temperature; and an appropriate temperature sensor that avoids the resonance frequency of the spring based on signals from the temperature sensor and the temperature setting section. The valve opening adjustment section generates a frequency-based pulse width modulation signal and controls the valve opening using the pulse width modulation signal.

The hysteresis of the magnetic core, whose magnetization is determined by the magnetic field generated by changing the direction of the current flowing through the working solenoid, is proportional to the speed at which the direction of the current is changed, that is, the frequency, and this frequency is defined as the resonant frequency of the spring. The width of the hysteresis is made small by avoiding it and reducing it as close to the resonant frequency as possible.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 4.

(1) is a compressor (2), a four-way valve (3), an outdoor heat exchanger (hereinafter referred to as a condenser) (4), a capillary tube as a pressure reducing device (5) and an expansion valve (6), an indoor side This is a refrigeration system having a main refrigerant flow path (A) in which a heat exchanger (hereinafter referred to as an evaporator) (7), an accumulator (8), etc. are connected in an annular manner, and the four-way valve (3) is closed during cooling operation. The refrigerant path is taken in the direction of the solid line arrow, and the refrigerant path is controlled to be taken in the direction of the dotted line arrow during defrosting □ operation. (9
) is an indoor fan that circulates and cools the air inside the storage room by sending air to the evaporator during cooling operation, and (10) and (11) are the evaporator (
7) are installed on the air suction side and the Suita side (the former is the suction temperature sensor and the latter is the Suita temperature sensor), and the detected temperature is sent to the valve opening adjustment section (15), which will be described later. A signal based on each signal is sent out. Note that a check valve (12> (13)) is connected in parallel to the capillary tube (5) and the expansion valve (6), respectively.

(14) is a refrigerant flow rate control valve whose opening degree is controlled by a valve opening degree adjusting part (15), and is a refrigerant flow control valve on the low pressure side (in this example , it is connected to the outlet side of the evaporator (7) during cooling operation. (B) is an electric valve whose opening and closing can be controlled by electrical signals (hereinafter referred to as a solenoid valve as a solenoid valve is used in this example) (16)
, an expansion valve (17), and an auxiliary evaporator (hereinafter referred to as auxiliary evaporator) <18) are connected in series to form a main refrigerant flow path (A), that is, an expansion valve (6), an evaporator (7), and a refrigerant flow control valve (
14), the outlet side of the condenser (4) (here, the outlet side of the capillary tube) and the outlet side of the evaporator (7) (here, the inlet side of the accumulator) during cooling operation. and the auxiliary evaporator (18) is located on the leeward side of the condenser (4). In addition, the solenoid valve (16) is connected to the suction side (
Here, the opening and closing of the accumulator (8) is controlled by a low pressure switch (19) disposed on the outlet side of the accumulator (8).

In this example, when the suction side pressure of the compressor (2) falls below a predetermined pressure P, the low pressure switch (19) closes, the electromagnetic coil (not shown) is energized, and the electromagnetic valve (16) is opened. Therefore, the suction side pressure is a constant pressure P! (Pa > pt
), the low pressure switch (19) opens to stop energizing the electromagnetic coil, so that the electromagnetic valve (16) becomes closed. In addition, the refrigerant flow control valve (14)
The opening degree of the valve is controlled by changing the force applied to the spring connected to the valve using an electric signal.It is controlled by a DC signal, but when a predetermined voltage (12V in this example) is applied, the valve opens completely. When zero voltage is applied, the opening is fully open, and when a voltage between zero voltage and a predetermined voltage is applied, the smaller the applied voltage, the greater the degree of opening.

This refrigerant flow control valve (14) can be called an electromagnetic control valve, and has a structure as shown in Fig. 4, and an example will be explained below (based on the flow of refrigerant during cooling operation). ). The valve body (30) has a refrigerant inlet (31) connected to the evaporator outlet side and a refrigerant outlet (32>) connected to the inlet side of the four-way valve (3). The partitioning wall (33) is provided with communication ports (34) and (35) that communicate the two parts (31 and 32).
4) The valve seats (36) and (37) that open and close (35) are connected to the valve stem (
38), one valve seat (36) is located on the inlet side and the other valve seat (37) is located on the outflow side.

Compressed fill springs (39) and (40) that bias the valve seats (36) and (37) in the direction of opening are respectively interposed in the outlet side valve body. An actuating body (41) provided on the head receives the magnetic force of a filter (42) excited by an electric signal, and drives the shaft in the vertical direction. Also, the valve seats (36) and (37) are filled with fill (
42) is fully open when not energized, fully closed when a predetermined voltage is applied, and operates in the open direction when the applied voltage becomes smaller. Therefore, this refrigerant flow rate control valve (14) has a structure that allows it to operate from fully closed to fully open or vice versa.

The valve opening adjustment section (15) is connected to the indoor temperature sensor (10) (1
1) and a temperature setting section (
The refrigerant flow control valve (14) receives signals from the refrigerant flow control valve (14), generates an electric signal (i.e., pulse width modulation signal) with a varying on-off duty ratio based on the relationship between these signals, and
), an example of which is shown in FIG. Note that the refrigerant flow control valve (14) has a magnetic core that is magnetized by a solenoid, which is a part of the valve, and the hysteresis width becomes large when the applied voltage changes smoothly, and when the voltage changes periodically. The hysteresis width has a characteristic that the shorter the cycle, the larger the hysteresis width, and this is one of the reasons why the response of changing the valve opening to the signal is delayed. Therefore, in order to reduce the hysteresis width, the valve opening adjustment is carried out. In section (15), the frequency is set in consideration of the resonance frequency of the spring when the applied voltage is changed periodically.

(21) is a calculation unit that receives both the signal from the temperature setting unit (20) and the signals from the indoor temperature sensors (10) and (11). is determined to be the room temperature) and the set temperature using the PID control method, and the calculated value is converted to, for example, an 8-bit binary signal and sent to the output terminal group D (
Output from D8-01). The output signal is called D data. The arithmetic unit (21) also sends out a pulse of a reference clock (frequency: 2 MHz here) from the output terminal. (22) is a counting unit which receives the reference clock pulse, divides the frequency by an appropriate number, and divides the clock pulse (64 in this example).
Frequency divider (31.25K) Iz pulse)
23) and a counter (24) that receives this clock pulse and counts in 8-bit binary numbers, that is, 256 steps. Outputs a bit binary signal. This output signal is P
Although called data, one period of P data is approximately 17120. (25) inputs the output of the calculation section (21), that is, the D data, and the output of the counting section (22), that is, the P data, compares both data, and based on the comparison result, a Hi level signal (predetermined Voltage VCC (hereinafter referred to as "H" signal) or Lo level signal (zero voltage, hereinafter referred to as "H" signal)
This is a comparison section that outputs a signal (referred to as "L" signal).The calculation section (21), the counting section (22), and the comparison section (25) constitute a valve opening adjustment section (15).

The output of the valve opening adjustment section (15) is connected to a switching element such as a switching transistor (hereinafter referred to as a transistor).
(26), the emitter of this transistor (26) is grounded, and the flap is connected to a predetermined voltage source Vcc (= 12 volts) via a refrigerant flow control valve (more specifically, an electromagnetic coil) (14). It is connected. Then, when the pulse width modulation signal output from the valve opening adjustment section (15) is a 'H' signal, the transistor (26) is turned on, energizing the electromagnetic coil, operating the valve in the closing direction, and turning the signal 'L'. When the signal is received, the transistor (26) is turned off and the valve operates in the direction of opening.Therefore, the valve is instructed to operate both fully open and fully closed within one cycle.
It cannot be followed mechanically, and the valve opening becomes stable at a position corresponding to the average voltage determined by the on-off duty ratio.

The operation of the refrigeration system with the above configuration during cooling operation will be explained (the refrigerant flow path by the four-way valve (3) is in the direction of the solid arrow).
It is assumed that the indoor temperature is higher than the set temperature.

A valve opening degree adjusting section (15) determines the opening degree of the valve based on the signals from the indoor temperature sensors (10) and (11), and sends out a signal to change the opening degree of the refrigerant flow rate control valve (14). At this time,
The high pressure gas refrigerant discharged from the compressor (2) is passed through the condenser (
The refrigerant is condensed and liquefied in step 4), depressurized and expanded in an expansion valve (6), exchanges heat with indoor air as it passes through an evaporator (7), and its flow rate is controlled by a refrigerant flow control valve (14). After passing through the accumulator (8), it becomes a low-pressure gas refrigerant and is compressed by the compressor (2).
) Return to By circulating the refrigerant through this main refrigerant flow path (A), the indoor air is cooled down to the set temperature.

Here, the refrigerant flow control valve (14) and the valve opening adjustment part (1
To explain the operation of 5), indoor temperature sensor (10) (1
1), the calculation unit (21) takes the average of both detection signals, determines the indoor temperature, and calculates the PID based on the relationship with the set temperature.
, and outputs D data from the output terminal group. This D data has a high value when the deviation between the indoor temperature and the set temperature is large, and a low value when it is small. On the other hand, the counting section (22) generates clock pulses from the reference clock, and counts these clock pulses in 256 steps in one period T. In this example, one period T is approximately 1/
120), and outputs P data from the output terminal group Q. Then, the comparison unit (25) compares the D data and the P data, and when the D data is larger than the P data (P<D), “H
When the D data is less than or equal to the P data (P≧D), a 'L' signal is output. Therefore, when the deviation is large, the period t in which the "H" signal is output during one period T is long, and as the deviation becomes small, the period t during which the 1H" signal is output is shortened. That is, the output voltage V in one period T
.

is (Vl - VCCx t / T), and since the length of t changes proportionally according to the deviation, v8 also takes a large value when the deviation is large, and takes a small value when the deviation is small. Become.

Then, the transistor (26) is turned on only during the period t during which the "H" signal is output, and the refrigerant flow control valve (14)
The current is applied only 1/T times for each period t in one second. This is essentially the same as applying a heavy pressure of [Vl-VccX t/T) to the refrigerant flow control valve (14) and stopping the valve at the opening degree based on this voltage V.

However, the frequency f of the signal output from the comparator (25)
When '(-1/T) becomes equal to the resonant frequency f of the spring connected to the refrigerant flow control valve (14), the control valve itself will resonate and will no longer be able to perform its original function as a valve. Within the range where resonance of the spring does not occur, f is set to a value that is larger than fL and as close to f as possible (120 Hz in the example). By setting in this way, the responsiveness of changing the valve opening degree to the voltage applied to the valve is improved.

On the other hand, as the cooling operation continues, the indoor temperature decreases and the opening degree of the refrigerant flow rate control valve (14) gradually decreases, so that the suction side pressure of the compressor (2) gradually decreases. When this suction side pressure falls below a predetermined pressure P, the low pressure switch (1
9) is closed and the solenoid valve (16) is opened. Therefore, the refrigerant that has passed through the condenser (4) is divided into the main refrigerant flow path (A) and the auxiliary flow path (B).

At this time, since the auxiliary evaporator (18) in the auxiliary channel (B) is located on the leeward side of the condenser (4),
The evaporation temperature of the auxiliary evaporator (18) is higher than the evaporation temperature of the evaporator (7) even when the same flow rate of refrigerant flows into the auxiliary evaporator (18). and,
As the refrigerant flows into the auxiliary flow path (B), the flow rate of refrigerant to the accumulator (8) increases, and the pressure on the suction side of the compressor (2) gradually increases. Furthermore, by diverting the refrigerant to the auxiliary flow path (B), the amount of refrigerant flowing to the main refrigerant flow path (A) is reduced, and the cooling capacity of the evaporator (7) is substantially reduced, causing the indoor temperature to rise. The degree of decrease in is reduced, and as a result, the opening degree of the refrigerant flow rate control valve (14) is suppressed from becoming small. If this state continues and the suction side pressure gradually increases to a constant pressure P3 or higher, the low pressure switch (19)
is opened, the solenoid valve (16) is closed, the branch flow to the auxiliary flow path (B) is cut off, and the cooling operation is again switched to using only the main refrigerant flow path (A). The same operation is repeated below. Therefore, the suction side pressure of the compressor (2) is prevented from dropping significantly below the predetermined pressure P1, and therefore the compressor (2) can be operated continuously without stopping. In addition to providing low pressure compensation, the compressor (2)
Since the compressor (2) does not stop, the number of starts that cause the most overload is reduced, and as a result, the life of the compressor (2) is extended.

〔Effect of the invention〕

As detailed above, according to the present invention, since the signal sent to the refrigerant flow control valve is a pulse width modulation signal, the current flowing through the solenoid that constitutes a part of the valve changes periodically. , the direction of the accompanying magnetic field also changes periodically. At this time, the magnetic core that receives this magnetic field and presses the spring operates with hysteresis, and the hysteresis is inversely proportional to the current cycle. Therefore, by selecting the frequency of the pulse width modulation signal to avoid the spring's resonant frequency and to be as close to this resonant frequency as possible, the hysteresis can be reduced and the response of changing the valve opening to the signal can be improved. are doing.

[Brief explanation of the drawing]

Each figure shows an embodiment of the present invention. Figure 1 is a block circuit diagram of the valve opening adjustment section, Figure 2 is a refrigerant circuit diagram with a refrigerant flow control valve, and Figure 3 is a valve opening adjustment section. FIG. 4 is a signal waveform diagram showing an example of a pulse width modulated signal that can be output from the refrigerant flow rate control valve. (1)... Refrigeration device, (7)... Evaporator, <1
o), m)...Temperature sensor, (14)...Refrigerant flow rate control valve, (15)...Valve opening adjustment section, (2
0)...Temperature setting section.

Claims (1)

[Claims] 1. In a refrigeration system in which a compressor, a condenser, a pressure reducer, and an evaporator are connected by pipes in a ring, a refrigerant whose opening degree is controlled by changing the force applied to a spring connected to a valve by an electric signal and controlling the refrigerant flow rate. a flow rate control valve; a temperature sensor that detects the temperature in the room cooled by the refrigeration device; a temperature setting section that sets a desired indoor temperature; 1. A refrigeration system comprising: a valve opening adjustment section that generates a pulse width modulation signal with an appropriate frequency that avoids the resonance frequency of the control valve, and outputs this signal to the control valve.