JPH076719B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention uses, as an expansion mechanism, an electric expansion valve that controls a superheat degree by adjusting a valve opening degree based on a difference in inlet and outlet temperatures of an evaporator
In addition, the present invention relates to a refrigerating apparatus that defrosts by introducing hot gas discharged from a compressor to an evaporator during frosting.

(Prior Art) Conventionally, an electric expansion valve is used as an expansion mechanism, a temperature sensor detects the inlet / outlet temperature of the evaporator, and the opening degree of the expansion valve is adjusted based on the detected inlet / outlet temperature difference to prevent a predetermined overheat. A device capable of obtaining a degree is known, for example, from JP-A-61-36671.

Further, a hot gas bypass passage is provided from the discharge side of the compressor to the inlet side of the evaporator, and the heat quantity of the hot gas introduced through the bypass passage is used to defrost the evaporator. Are known, for example, from Japanese Patent Application Laid-Open No. 59-122863.

Then, in the one in which the electric expansion valve is used for the expansion mechanism and the defrosting is performed by the hot gas bypass system, after the defrosting is completed, the inlet temperature of the evaporator on the hot gas injection side is usually In the case of the cooling operation of the above, since it will reverse from the state lower than the outlet temperature to the state higher than the outlet temperature, superheat control based on the inlet / outlet temperature difference can no longer be performed, and therefore, in general, the expansion valve The valve opening of the
For a second), it is forcibly fixed to a fixed opening of, for example, about 75%, so that a transient response can be made when the operation is restarted.

(Problems to be Solved by the Invention) However, even when the valve opening degree of the electric expansion valve is fixed to a constant opening degree for a certain period of time when the operation is restarted after the completion of defrosting, depending on the outside air condition, The problem of.

That is, when the outside air is low, the condensing action in the condenser is promoted and the predetermined refrigerating capacity can be satisfactorily drawn out, so that the inlet / outlet temperature of the evaporator is relatively quickly brought to a low temperature state corresponding to the warehouse set temperature. Although it decreases, the fixed valve opening (75%) is nevertheless too wide for the relatively small heat load at low outside air, or the valve opening fixed time (30 seconds) However, if it is too long compared to the temperature decrease time of the evaporator, the evaporation of the refrigerant in the evaporator will not be sufficient due to the temperature decrease of the evaporator, and the liquid refrigerant will be returned to the compressor. Liquid back occurred.

On the other hand, when the outside air is high, the fixed valve opening fixed for a fixed time is not wide enough or the valve opening fixed time is short, even though the temperature of the evaporator slows down due to the reduction of the refrigerating capacity. If the evaporator is not sufficiently cooled, it will be shifted to normal superheat control, the valve opening will be throttled immediately, the amount of refrigerant supplied to the evaporator will decrease, and the inside of the refrigerator will be set. The pull-down time for lowering the temperature to temperature was prolonged.

The above-mentioned problem becomes more remarkable in the case of refrigeration loading mounted on a sea container or the like, and since the outside air temperature fluctuates greatly depending on day and night or the area, a uniform valve opening degree. In addition, it was difficult to properly restart the operation that matched the outside air conditions with the fixed valve opening fixed time.

The object of the present invention is to adjust the valve opening degree of the expansion valve at the time of restarting the driver's operation after defrosting, and to devise conditions for shifting to normal superheat control, so that the liquid Another object of the present invention is to provide a refrigeration system capable of avoiding backing and shortening the pull-down time.

(Means for Solving Problems) Therefore, according to the present invention, a compressor (1), a condenser (2), an evaporator (5), and a valve opening adjustment based on a difference in inlet and outlet temperatures of the evaporator (5) are provided. An electric expansion valve (4) for controlling the degree of superheat, and a hot gas bypass passage for guiding hot gas discharged from the compressor (1) to the evaporator (5) by-passing the condenser (2). (8) and a hot gas valve (7) for bypassing the hot gas in the bypass passage (8), and a hot gas introduced through the bypass passage (8) during frosting of the evaporator (5). A refrigerating apparatus for defrosting the evaporator (5) by gas, comprising a storage means for storing the outlet temperature of the evaporator (5) immediately before the start of defrosting, and a restarting operation after the completion of defrosting. The valve opening of the expansion valve (4) is set to the evaporator ( The expansion outlet valve is controlled after the detected outlet temperature of 5) is sequentially controlled so as to approach the stored outlet temperature stored in the storage means, and the detected outlet temperature or the detected inlet temperature approaches the stored outlet temperature. A valve opening control means for shifting the valve opening adjustment of (4) to superheat control based on the inlet / outlet temperature difference of the evaporator (5) is provided.

(Operation) The valve opening degree of the expansion valve (4) is determined based on the stored outlet temperature just before the start of defrost, which is the stored outlet temperature of the evaporator (5) stored in advance, that is, in the normal cooling operation. Is gradually adjusted so that the temperature of the evaporator (5) in the high temperature state immediately after the completion of defrosting decreases, the amount of refrigerant is adjusted according to the temperature decrease of the evaporator (5). , Liquid back can be avoided, and
The transition to the superheat control is performed irrespective of the outside air temperature, after the detection outlet temperature or the detection inlet temperature of the evaporator (5) has dropped to near the memory outlet temperature, and at this time, the evaporator In (5), since the temperature is already close to the low temperature state before defrosting, the pull-down time delay can be eliminated.

(Embodiment) FIG. 1 shows a refrigerating apparatus mounted on, for example, a marine container, and a condenser (a fan (F2) is attached from the discharge gas pipe (11) side of the compressor (1) ( 2), a liquid receiver (3), an electric expansion valve (4), an evaporator (5) with a fan (F) attached, and an accumulator (6) are sequentially connected through a refrigerant pipe (10), and Discharge gas pipe (11)
The hot gas discharged from the compressor (1) via the hot gas valve (7) between the condenser and the flow divider (45) installed at the inlet of the evaporator (5) and the condenser (2) and expansion. Hot gas bypass passage (8) which leads the evaporator (5) by bypassing the valve (4)
Is provided.

The electric expansion valve (4) includes a valve drive section (40M) for driving and adjusting a valve opening degree, and the inlet pipe (51) of the evaporator (5).
The inlet and outlet temperatures of the evaporator (5) are detected by an inlet temperature sensor (41) and an outlet temperature sensor (42) attached to the outlet pipe (52) and the valve opening degree based on the detected inlet and outlet temperature difference. Is adjusted to obtain an appropriate degree of superheat.

The hot gas valve (7) is connected to the bypass passage (8).
Using an electric three-way proportional valve that can control the valve opening to 0% to 100% by driving its electric part (20M),
The hot gas bypass amount to the evaporator (5) is adjusted, and when the evaporator (5) is frosted, the hot gas valve (7) is opened 100% to the bypass passage (8) to circulate. The entire amount of the hot gas used is introduced into the evaporator (5), and the hot gas is used for defrosting.

With the above configuration, when the operation is restarted after the completion of defrost,
A storage means for storing the outlet temperature of the evaporator (5) immediately before the start of defrosting and a valve opening of the expansion valve (4) at the time of restarting operation after completion of defrosting so that the operation can be properly restarted regardless of the outside air temperature. Degree of the evaporator (5)
The detection outlet temperature of the is sequentially controlled so as to approach the storage outlet temperature stored in the storage means, and after the detection outlet temperature or the detection inlet temperature reaches near the storage outlet temperature,
A controller (100) shown in FIG. 2 is formed by forming valve opening control means for shifting the valve opening adjustment of the expansion valve (4) to superheat degree control based on the inlet / outlet temperature difference of the evaporator (5).
It is provided inside.

The controller (100) is configured by using a microcomputer or the like, and its input side is based on the inlet / outlet pressure difference of the air passing through the evaporator (5) in order to receive a defrost start command. In order to connect the operating air pressure switch (APS), the defrost timer switch (2D) with a set time of 12 hours, and the manual defrost switch (3D) that performs defrost by manual operation, and to detect the completion of defrost , A thermistor (Th) for detecting the temperature of the outlet pipe (52) is connected. Further, a return and supply sensor (RS) (SS) for detecting the temperature of intake and blown air of the evaporator (5), and a temperature setter (55) for setting the temperature inside the refrigerator.
The temperature sensors (41) (42) for detecting the inlet and outlet temperatures of the evaporator (5) and the outside air temperature detector (60) for detecting the outside air temperature are connected.

On the other hand, on the outlet side, an electromagnetic relay (88C) that starts and stops the motor (MC) of the compressor (1), an electromagnetic relay (88F) that starts and stops the motor (MF) of the evaporator side fan (F), and the Electromagnetic relay (88FH) that changes the rotation speed of the motor (MF) by changing the number of poles, etc., to switch the air passing through the evaporator (5) between high air volume and low air volume, motor (MF2) of the condenser side fan (F2) )
Relay (88F2) for starting and stopping, electric part (20M) of hot gas valve (7), valve drive part (40M) of electric expansion valve (4)
Connect. In addition, in the exciting circuit of the relays (88C) (88F), a high pressure pressure detector (HP
S), the contact (51C) and the thermoswitch (49C) of the overcurrent relay of the compressor motor (MC) are installed in series, and the fan relay (88F) is connected to the fan motor ( MF) thermoswitch (49CF) is connected in series.

Then, based on the internal temperature setting (SP) set by the temperature setting device (55), a predetermined cooling operation is performed from a frozen region of approximately -5 ° C to -6 ° C or less to a chilled region higher than that. During this cooling operation, the evaporator (5) is frosted and the air pressure switch (APS) is automatically operated by the pressure change of the passing air, or the defrost timer switch (2D) is operated. )
When a defrost command is issued at every specified time or the defrost switch (3D) is manually operated, the operation shifts to the defrost operation.

Thus, when the defrost start command is input, the process is performed according to the flowchart shown in FIG. 3. First, the outlet temperature of the evaporator (5) immediately before the defrost start detected by the outlet temperature sensor (42) is performed. (TR
O) is stored in the memory in the controller (100) that constitutes the storage means. The outlet temperature (TRO) stored in this storage means is a value during normal cooling operation before the start of defrosting, that is, a low temperature value based on the set temperature (SP) in the refrigerator, and is generally about the above-mentioned set temperature in the refrigerator. The temperature is about 5 ° C lower than the temperature (SP).

Then, after storing the outlet temperature (TRO), the electric part (20M) of the hot gas valve (7) is driven to open the high pressure gas pipe (11) 100% with respect to the bypass passage (8) for circulation. The defrosting is performed by bypassing the entire amount of hot gas to be supplied to the evaporator (5).

In this way, the evaporator (5) is defrosted by the amount of heat of the hot gas, and it is detected that the defrosting progresses, the outlet pipe (52) is heated, and the thermistor (Th) reaches a predetermined temperature. Then, the defrost operation is completed.

Then, when the operation is restarted after the defrosting is completed, the outlet temperature sensor (42) detects the outlet temperature of the evaporator (5) and stores the detected outlet temperature (tRO) in the storage means. The difference (TRO-tRO) from the memory outlet temperature (TRO) immediately before the start of Oita defrost is the predetermined temperature range (ΔT),
For example, the valve opening degree (V) of the expansion valve (4) is determined so that the detected outlet temperature (tRO) approaches the memory outlet temperature (TRO) until the temperature range of 1 ° C to 2 ° C is entered. .

The valve opening degree (V) is set to be wider as the difference between the detected outlet temperature (tRO) and the memory outlet temperature (TRO) is larger, and is set to be gradually narrower as the difference becomes smaller. As shown in FIG. 4 and the following equation, the temperature difference (TRO-tRO) and the valve opening degree (V) are associated with each other by a logarithmic function, and the coefficients (α) and (β) are experimentally obtained to obtain the above. It is stored in the controller (100) and calculated every time the outlet temperature (tRO) is detected.

V = α {ln (TRO-tRO)} ² + β ... In is the natural logarithm based on e = 2.718.

Then, based on the valve opening degree (V) set by the above equation, the valve drive unit (40M) is operated to control the expansion valve (4). Hereinafter, the detected outlet temperature (tRO) is the memory outlet temperature (TRO). Until the temperature reaches close, that is, the temperature difference (TRO-tRO = ΔT)
The valve opening degree (V) is sequentially updated every time the temperature is detected by the outlet temperature sensor (42) until the temperature becomes 1 ° C to 2 ° C.

As a result, as shown in FIG. 5, the outlet temperature of the evaporator (5) is gradually decreased from the high temperature state immediately after the completion of defrosting. In this case, immediately after the completion of defrosting, the detection outlet temperature is decreased. Temperature (tRO) and memory outlet temperature (TR
Since the temperature difference with O) is large, the valve opening (V) is controlled to a wide opening, and a large amount of refrigerant is supplied to the evaporator (5) in the high temperature state, and the temperature decrease can be promoted. Further, when the detected outlet temperature (tRO) decreases toward the memory outlet temperature (TRO) side and the temperature difference becomes smaller, the valve opening (V) is controlled narrower and the refrigerant supplied to the evaporator (5) is reduced. The amount is reduced and liquid back can be avoided.

Then, when the detection outlet temperature (tRO) decreases to near the memory outlet temperature (TRO) and the temperature difference ΔT becomes 1 ° C to 2 ° C,
The normal superheat control is performed, and the transition to the superheat control is performed regardless of the outside air temperature, the detection outlet temperature (tRO) of the evaporator (5) and the set temperature (SP) in the refrigerator.
Memory temperature just before defrost start (TR
O) based on the comparison with
At this time, since the outlet temperature of the evaporator (5) is already in a low temperature state close to the memory outlet temperature (TRO), that is, the value at the time of normal cooling operation, the problem of delay of pull-down time can be eliminated. .

Therefore, it is possible to eliminate the problems such as liquid backing and delay of pull-down time as in the case where the valve opening degree and the valve fixing time are uniform, and it is possible to appropriately restart the operation regardless of the outside air temperature.

After shifting to the normal superheat control, the cooling operation in the chilled or frozen region is performed based on the internal set temperature (SP). (20M) is so-called PID control based on the comparison between the set temperature (SP) and the return sensor (RS), bypasses a certain amount of hot gas that matches the heat load, and the electromagnetic relay (88FH) When turned on, the amount of air passing through the evaporator (5) is set to a high amount to improve the circulation of air in the refrigerator. Also, in the operation in the frozen region, bypass of hot gas is not performed, and start / stop control of the compressor (1) is performed based on the comparison between the set temperature (SP) and the return or supply sensor (RS or SS). Together with the electromagnetic relay (88
FH) is turned off, and the amount of air passing through the evaporator (5) is made low.

In the embodiment described above, the valve opening (V) is set to the temperature difference (TR
Although the logarithmic function of (O-tRO) is used for the correspondence, the present invention is not limited to this, and proportional control may be performed based on the temperature difference (TRO-tRO), or the temperature difference (TRO-tRO) and the valve opening. Degree (V)
It may be associated with any curve that is experimentally obtained. In this case, the curve data is stored in the memory in the controller (100) and a data search is performed every time the outlet temperature (tRO) is detected. The valve opening (V) may be sequentially updated by performing the above.

Further, in the above embodiment, the transition condition to the normal superheat degree control is that the difference between the detected outlet temperature (tRO) and the memory outlet temperature (TRO) is within the predetermined temperature range (ΔT), and the outlet temperature is The detection outlet temperature (tRO) by the sensor (42) is set to the contrast temperature, but the detection inlet temperature (tRI) detected by the inlet temperature sensor (41) is set as the contrast temperature.
Needless to say, it may be set when the difference between the temperature and the memory outlet temperature (TRO) enters the predetermined temperature range (ΔT).

(Effect of the invention) As described above, in the present invention, the outlet temperature of the evaporator (5) immediately before the start of defrosting is stored, and when the operation is restarted after the completion of defrosting, the valve opening degree of the electric expansion valve (4) is set as follows. After the detected outlet temperature of the evaporator (5) is sequentially adjusted so as to approach the stored stored outlet temperature, and the detected outlet temperature or the detected inlet temperature reaches near the stored outlet temperature, the expansion valve ( Since the valve opening adjustment of 4) is shifted to the normal superheat control, problems such as liquid back and delay of pull-down time can be avoided, and appropriate operation restart can be performed regardless of outside air temperature.

[Brief description of drawings]

FIG. 1 is a refrigerant piping system diagram of a refrigerating apparatus according to the present invention, and FIG.
The figure is the same control circuit diagram, FIG. 3 is a flow chart showing the control procedure from the defrost operation to the restart of the operation after its completion, FIG. 4 is a view showing a setting example of the valve opening degree, and FIG. It is a figure which shows the change of an inlet and an outlet temperature. (1) ...... Compressor (2) ...... Condenser (4) ...... Motorized expansion valve (5) ...... Evaporator (7) ...... Hot gas valve (8) ...... Hot gas bypass passage

Claims (1)

[Claims] 1. A motor-operated expansion valve (4) for controlling a superheat by controlling a valve opening of a compressor (1), a condenser (2), an evaporator (5) and a temperature difference between an inlet and an outlet of the evaporator (5). ) And a hot gas bypass passage (8) for guiding hot gas discharged from the compressor (1) to the evaporator (5) by-passing the condenser (2), and the bypass passage (8). ) Is provided with a hot gas valve (7) for bypassing hot gas, and when the evaporator (5) is frosted, hot gas introduced through the bypass passage (8) is used to defrost the evaporator (5). In the refrigerating apparatus, the storage means for storing the outlet temperature of the evaporator (5) immediately before the start of defrost, and the valve opening degree of the expansion valve (4) at the time of restarting the operation after the completion of defrost. The detected outlet temperature of the evaporator (5) is stored in the storage means. After sequentially controlling the stored outlet temperature to approach the stored outlet temperature, and after the detected outlet temperature or the detected inlet temperature reaches near the stored outlet temperature, the valve opening degree of the expansion valve (4) is adjusted by the evaporator ( 5) A refrigeration system comprising valve opening control means for shifting to superheat control based on the inlet / outlet temperature difference of 5).