JPH07107467B2 - Refrigeration equipment - Google Patents

Description

The present invention relates to a refrigerating apparatus for controlling the temperature of a low-temperature storage, and more specifically to changing the opening degree of a refrigerant flow control valve for controlling the refrigerant flow rate. The present invention relates to a refrigeration system having an improved control device.

2. Description of the Related Art There are several types of valves for controlling the flow rate of a refrigerant, and among them, an electric expansion valve that is excellent in its responsiveness is well known. For this electric expansion valve,
There are ones that adjust the valve opening degree by a motor, and one that adjusts the valve resolution by changing the force applied to the spring that is connected to the valve. In the present invention, the latter valve is adopted, and as the latter valve, there are JP-B-60-56983 and JP-B-60-34037. In Japanese Patent Publication No. 60-56983, the change in temperature at the outlet side of the evaporator is converted into an electric signal, and the opening degree of the valve is adjusted by this electric signal. On the other hand, according to Japanese Patent Publication No. 60-34037, at the time of starting the compressor, the electric expansion valve is fully opened until the electric signal from the third temperature sensor provided at the condenser inlet or intermediate portion reaches a predetermined value. The control circuit outputs a signal for setting the state.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In Japanese Patent Publication No. 60-56983, what kind of signal is used as an electric signal for changing the opening of the expansion valve is not described in detail, and its controller is not specified. On the other hand, in JP-B-60-34037, when the compressor is started after being stopped for a long time, the expansion valve is fully opened until the electric signal of the temperature sensor provided in the condenser reaches a predetermined value. The control circuit outputs a signal indicating that the start is extremely stable. However, the control circuit is not configured to improve the response of the expansion valve to the applied voltage. Therefore, in both publications, no improvement is made to speed up the response of the electric expansion valve to the signal, and although the control signal is quickly changed with respect to the temperature change, it is the valve opening change speed. There was a problem that was not prosperous.

Therefore, in the present invention, in the electric expansion valve, the force applied to the spring connected to the valve is generated by the solenoid, and the cause of the poor response of opening and closing of the valve is the hysteresis of the magnetic core magnetized by the solenoid. Paying attention to the fact that it is a technical issue to reduce this hysteresis width,
It is intended to provide a refrigerating apparatus having a control device (valve opening adjustment unit) that sends out a signal with which the hysteresis width becomes small.

[Structure of Invention]

Means for Solving the Problem The present invention provides a refrigeration apparatus in which a compressor, a condenser, a decompression device, and an evaporator are connected by pipes in an annular shape, and a force applied to a spring connected to a valve by an electric signal is applied. A refrigerant flow rate control valve that controls the refrigerant flow rate by changing its opening degree,
A temperature sensor that detects the temperature of the room cooled by the refrigeration system, a temperature setting unit that sets a desired room temperature, and avoids the resonance frequency of the spring based on signals from the temperature sensor and the temperature setting unit. There is provided a valve opening adjustment unit that generates a pulse width modulation signal with a frequency near the resonance frequency and controls the opening of the valve with the pulse width modulation signal.

The hysteresis of the magnetic core magnetized by the magnetic field generated by changing the direction of the current flowing through the solenoid is proportional to the speed at which the direction of the current changes, that is, the frequency, and the resonance frequency of the spring is used as this frequency. Avoid,
Moreover, the width of the hysteresis is made small by selecting the frequency as close as possible to this resonance frequency (frequency near the resonance frequency).

Embodiment An embodiment of the present invention will be described below 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 (5) as a decompressor and an expansion valve (6), indoor side 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), and the like are connected in an annular pipe, and a four-way valve (3) is used in a cooling operation. It is controlled to take the refrigerant path in the direction of the solid arrow and take the refrigerant path in the direction of the broken arrow during the defrosting operation. (9) is an indoor blower that sends air to the evaporator during cooling operation to circulate / refrigerate the air in the storage room, and (10) and (11) are evaporators (7) during cooling operation to detect the temperature in the storage room. ) Is an indoor temperature sensor (the former is the intake temperature sensor and the latter is the outlet temperature sensor) provided on the air intake side and the air outlet side, respectively. The signal based on each is transmitted. The capillary tube (5) and the expansion valve (6) have check valves (1
2) Connect (13) in parallel.

Reference numeral (14) is a refrigerant flow rate control valve whose opening is controlled by a valve opening adjusting section (15), and is on the low pressure side of the refrigeration system (1) (more specifically, the main refrigerant flow path (A)) (this example). Then, it is connected to the outlet side of the evaporator (7) during the cooling operation. (B) is a motor-operated valve whose opening and closing is controlled by an electric signal (in the present example, a solenoid valve is used, henceforth referred to as a solenoid valve) (16), an expansion valve (17) and an auxiliary evaporator (hereinafter referred to as an auxiliary evaporator). )
(18) is a main refrigerant flow path (A) that is connected in series, that is, an auxiliary flow path that bypasses the expansion valve (6), the evaporator (7) and the refrigerant flow control valve (14), and is used for condensation during cooling operation. Is connected between the outlet side of the vessel (4) (here the outlet side of the capillary tube) and the outlet side of the evaporator (7) (here the inlet side of the accumulator), and the auxiliary evaporator (18) is connected to the condenser. It is arranged so as to be located on the leeward side of (4). The opening / closing of the solenoid valve (16) is controlled by a low pressure switch (19) arranged on the suction side of the compressor (2) (here, on the outlet side of the accumulator (8). In this example, the compressor When the suction side pressure of (2) becomes less than the predetermined pressure P ₁ ,
When the low-pressure switch (19) is closed, the electromagnetic coil (not shown) is energized, the solenoid valve (16) is opened, and the suction side pressure exceeds a certain pressure P ₂ (P ₂ > P ₁ ) The switch (19) opens and the solenoid coil is de-energized and the solenoid valve (1
Keep 6) closed. The refrigerant flow control valve (14) controls the opening of the valve by changing the force applied to the spring connected to the valve by an electric signal, and is controlled by a DC signal. 12V), it is fully closed when a voltage of 0V is applied, and it is fully opened when a voltage of zero is applied. When a voltage between a voltage and a predetermined voltage is applied, the opening becomes larger as the applied voltage becomes smaller.

The refrigerant flow control valve (14) is called an electromagnetic control valve and has a structure as shown in FIG. 4, and an example thereof will be described below (however, the flow of the refrigerant during the cooling operation is also described. And explained). The valve body (30) has a refrigerant inflow part (31) connected to the evaporator outlet side and a refrigerant outflow part (32) connected to the inlet side of the four-way valve (3), and the valve body is divided into two chambers. The partition wall (33) to be partitioned divides the communication port (3) that connects both parts (31) (32).
4) (35) is drilled, and valve seats (36) (37) that open and close the communication ports (34) (35) are provided on the valve shaft (38), and one valve seat (36) flows in. And the other valve seat (37) is located on the outflow side. Then, the compressed coil springs (39) (40) that urge the valve seats (36) (37) in the opening direction.
Are provided in the outlet side valve body, respectively, while the actuating body (41) provided on the head of the valve shaft (38) receives the magnetic force of the coil (42) excited by an electric signal. Drive vertically. Further, the valve seats (36) (37) are fully opened when the coil (42) is not energized, fully closed when a predetermined voltage is applied, and operate in the opening direction when the applied voltage becomes small. Therefore, the refrigerant flow control valve (14 has a structure capable of performing an operation from fully closed to fully open or vice versa.

The valve opening adjustment section (15) receives signals from the indoor temperature sensors (10) and (11) and a temperature setting section (20) that sets the indoor temperature to a desired temperature, and based on the relationship between these signals, the on / off duty is set. An electric signal (that is, a pulse width modulation signal) with a changed ratio is created to control the refrigerant flow control valve (14), and an example thereof is shown in FIG. The refrigerant flow rate control valve (14) has a magnetic core magnetized by a solenoid which forms a part thereof, and has a large hysteresis width with respect to a smooth change in the applied voltage, and has a large hysteresis width with respect to a surrounding change. As the cycle becomes shorter, the hysteresis width becomes larger, which is one of the causes of delaying the response of the valve opening change to the signal.Therefore, in order to reduce this hysteresis width, the valve opening adjustment The part (15) sets the frequency by taking into consideration the resonance frequency of the spring when the applied voltage is changed periodically.

Reference numeral (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). The average temperature detected by the indoor temperature sensors (10) and (11) Is determined as the room temperature) and the set temperature, a calculation is performed by the PID control method, the calculated value is converted into, for example, an 8-bit binary signal, and the output terminal group D (D _{0 to} D ₇ ). Output more. The output signal is referred to as D data. Arithmetic unit (2
In 1), the pulse of the reference clock (here, the frequency is 2 MHz) is sent from the output terminal φ. (22) is a counter, which receives a reference clock pulse and divides it by an appropriate number to generate a slock pulse (in this example, it is divided by 64 to generate a pulse of 31,25 KHz)
Frequency divider (23) and a counter (24) that receives this clock pulse and counts it in 8-bit binary numbers, that is, 256 steps
The counter (24) outputs an 8-bit binary signal from the output terminal group Q (Q _{0 to} Q ₇ ). This output signal is P
Although referred to as data, one cycle of P data is about 1/120.
Then, (25) inputs the output of the calculation unit (21), that is, D data, and the output of the counting unit (22), that is, P data,
The two data are compared and a Hi level signal (predetermined voltage V _cc , hereinafter referred to as "H" signal) or L based on the comparison result.
This is a comparison unit that outputs a level signal (zero voltage, which will be referred to as “L” signal hereafter). The arithmetic unit (21) and the counting unit (22)
Further, the valve opening adjustment section (15) is configured by the comparison section (25).

The output of the valve opening adjustment unit (15) is a switching element, for example, a switching transistor (hereinafter referred to as a transistor).
It is input to the base of (26), the emitter of this transistor (26) is grounded, and the collector is connected to a predetermined voltage source V via a refrigerant flow control valve (more specifically, electromagnetic coil) (14).
It is connected to _cc (= 12 volts). When the "H" signal in the pulse width modulation signal output from the valve opening adjustment section (15), the transistor (26) is turned on and the electromagnetic coil is energized, and the valve operates in the closing direction. When a signal is given, the transistor (26) is turned off and the valve operates in the opening direction. For this reason, the valve is instructed to perform both full open and full close operations within one cycle, but it cannot follow mechanically,
The valve opening at the position corresponding to the average voltage determined by the on / off duty ratio stabilizes.

Although the operation during the cooling operation of the refrigerating device having the above-described configuration will be described {the refrigerant flow path by the four-way valve (3) is in the direction of the solid line arrow}, the stored matter is appropriately accommodated in the storage chamber,
It is assumed that the room temperature exceeds the set temperature.

A valve opening adjustment section (15) determines the opening of the valve based on the signals from the indoor temperature sensors (10) and (11) and sends a signal to change the opening of the refrigerant flow control valve (14). At this time, the high-pressure gas refrigerant discharged from the compressor (2) is condensed in the condenser (4), liquefied, decompressed and expanded in the expansion valve (6), and passed through the evaporator (7). Exchanges heat with indoor air,
The flow rate is controlled by the refrigerant flow rate control valve (14), passes through the accumulator (8), becomes a low-pressure gas refrigerant, and returns to the compressor (2). The refrigerant circulates in the main refrigerant channel (A) to cool the room air and reduce the temperature to the set temperature.

Here, the refrigerant flow control valve (14) and the valve opening adjustment section (15)
The operation of (1) receives the signals from the indoor temperature sensors (10) (11), the arithmetic unit (21) takes the average of both detection signals as the indoor temperature, and calculates the PID from the relationship with the set temperature. D data is output from the output terminal group D. This D
The data has a low value when the deviation between the indoor temperature and the set temperature is large, and a high value when the deviation is small. On the other hand, the counter (22) creates a clock pulse from the reference clock,
This clock pulse is counted in 256 steps in one cycle T (one cycle T is about 1/120 in this example), and P data is output from the output terminal group Q. Then, the comparing section (25) compares the D data with the P data, and when the D data is larger than the P data (P <D), outputs an “L” signal, and the D data is equal to or less than the P data (P ≧ D). At this time, the "H" signal is output. Therefore, when the deviation is large, the period t during which the "H" signal is output in one cycle T is long, and the "H" becomes longer as the deviation becomes smaller.
The period t during which the signal is output becomes shorter. That is, one cycle T
The output voltage V _{t at} is [V _t = V _cc × t / T], and the length of t changes proportionally according to the deviation. Therefore, V _t also has a large value when the deviation is large, and the deviation is small. Sometimes it takes a small value.

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) is energized only 1 / T times for each period t per second. It This is substantially the same as when a voltage of [V _t = V _cc × t / T] is applied to the refrigerant flow control valve (14) and the valve stops at the opening based on this voltage V _t. .

However, the frequency f of the signal output from the comparison unit (25)
When (= 1 / T) becomes equal to the resonance frequency f _L of the spring connected to the valve of the refrigerant flow control valve (14), the control valve resonates and the original function as a valve cannot be achieved. ,
Within a range in which spring resonance does not occur, f is set to a value that is as close to f _L as possible, even if it is larger than f _L (120 Hz in the embodiment). By setting in this way, the responsiveness of changing the valve opening degree with respect to the voltage applied to the valve is improved.

On the other hand, when the room temperature decreases as the cooling operation continues and the opening of the refrigerant flow control valve (14) also gradually decreases, the suction side pressure of the compressor (2) gradually decreases. When the suction side pressure becomes equal to or lower than the predetermined pressure P ₁ , the low pressure switch (19) 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 passage (A) and the auxiliary passage (B). At this time, since the auxiliary evaporator (18) in the auxiliary flow path (B) is located on the leeward side of the condenser (4), it is warmed by the warm air heat-exchanged in the condenser (4) and has the same flow rate. Even when the refrigerant flows in, the evaporation temperature of the auxiliary evaporator (18) becomes higher than the evaporation temperature of the evaporator (7). Then, as the refrigerant flows into the auxiliary flow path (B), the refrigerant flow rate to the accumulator (8) increases, and the suction side pressure of the compressor (2) gradually increases. In addition, by splitting the refrigerant in the auxiliary flow path (B), the main refrigerant flow path (A)
The amount of refrigerant flowing into the evaporator (7) is reduced, and the cooling capacity of the evaporator (7) is substantially reduced, the degree of decrease in the indoor temperature is reduced, and as a result, the opening of the refrigerant flow control valve (14) is reduced. It is suppressed from becoming small. When this state continues and the suction side pressure gradually rises to a certain pressure P ₂ or more, the low pressure switch (19) opens and the solenoid valve (16) closes, and the diversion to the auxiliary flow path (B) is cut off. Then, the same operation is repeated again by switching to the cooling operation using only the main refrigerant flow path (A). Therefore, the suction side pressure of the compressor (2) is the predetermined pressure.
Significantly lower than P ₁ is suppressed, so that the compressor (2) can be continuously operated without stopping. That is, the low pressure compensation of the compressor (2) can be performed, and since the compressor (2) does not stop, the most overloaded start can be reduced and the life of the compressor (2) can be extended as a result. Become.

〔The invention's effect〕

As described above, according to the present invention, since the signal sent to the refrigerant flow control valve is the pulse width modulation signal, the current flowing through the solenoid forming a part of the valve changes periodically, The direction of the magnetic field accompanying it also changes periodically. At this time, the magnetic core that receives this magnetic field and presses the spring operates with hysteresis, which hysteresis is inversely proportional to the current cycle. For this reason, the frequency of the pulse width modulated signal is set so as to avoid the resonance frequency of the spring and to be as close as possible to this resonance frequency (frequency near the resonance frequency), thereby reducing hysteresis and making the valve Improves responsiveness of opening change.

[Brief description of drawings]

Each drawing shows one embodiment of the present invention, FIG. 1 is a block circuit diagram of a valve opening adjusting section, FIG. 2 is a refrigerant circuit diagram in which a refrigerant flow control valve is arranged, and FIG. FIG. 4 is a signal waveform diagram showing an example of the pulse width modulation signal output from the section, and FIG. 4 is a schematic sectional view of the refrigerant flow control valve. (1) …… Refrigerator, (7) …… Evaporator, (10), (1
1) ... Temperature sensor, (14) ... Refrigerant flow control valve, (1
5) …… Valve opening adjustment section, (20) …… Temperature setting section.

Claims (1)

[Claims] In a refrigeration system in which a compressor, a condenser, a decompression device, and an evaporator are connected in an annular pipe, the force applied to a spring connecting the valves is changed by an electric signal to control the opening thereof to control the refrigerant flow rate. A refrigerant flow rate control valve for controlling, a temperature sensor for detecting the temperature of the room cooled by the refrigerating apparatus, a temperature setting unit for setting a desired room temperature, and a signal of the temperature sensor and the temperature setting unit. And a valve opening adjusting section for generating a pulse width modulation signal at a frequency near the resonance frequency of the spring while avoiding the resonance frequency of the spring and outputting this signal to the control valve. apparatus.