JPH0325108Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is a defrost completion detection device for a refrigeration system;
More specifically, the present invention relates to a detection device for detecting the end of defrosting performed by flowing hot gas into an evaporator.

Generally, in a refrigeration system, when defrosting is performed by flowing hot gas into the evaporator, a temperature sensor is installed on the outlet side of the evaporator to detect the end of the defrost and detect the temperature of the hot gas at the outlet of the evaporator as the defrost ends. The temperature rise is detected, and the defrost operation is terminated by the operation of the temperature detector.

However, the defrost completion detection as described above is carried out using a single temperature sensor, and the temperature sensor uses a bimetal as its temperature sensing part, and as the temperature rises, this bimetal A bimetal type device is used in which the contact is opened by the operation of the bimetal, and the set temperature at which the bimetal is activated to open the contact is high, for example, 50 to 60°C, and the bimetal is welded. Since accidents are likely to occur, there is a problem in that it is not possible to accurately detect the end of defrost over a long period of time.

Therefore, conventionally, inspections and maintenance have been performed periodically, but the frequency of such inspections is high, forcing the user to spend a large amount of maintenance work.

The purpose of the present invention is that when the temperature sensor is normal, the switch is turned on during refrigeration operation, and turned off when the hot gas temperature on the evaporator outlet side rises during defrost operation, and the switch is turned off when the temperature sensor is in a normal state. Focusing on the fact that the hot gas remains on in the event of a failure, we used multiple temperature detectors with different hot gas detection temperatures when turned off, and the low-temperature side temperature detector with a lower hot gas detection temperature when turned off was developed. If it is working properly,
Using only the low-temperature detector, the high-temperature detector, which has a high hot gas detection temperature when turned off, is rendered inactive, and the high-temperature detector can operate only after the low-temperature detector has failed. In this way, even if the life of each of the temperature detectors is short, the life of the detection device as a whole for detecting the end of defrost can be extended, the maintenance cycle can be lengthened, and the user's maintenance man-hours can be reduced. , while using the temperature detectors with the same specifications, the hot gas detection temperature at the time of off operation can be made different with a simple configuration, and the management of the parts can be simplified;
This is designed to minimize cost increases.

The configuration of the present invention is to fix a first temperature detector to the low-pressure gas pipe on the outlet side of the evaporator, which has a switch that turns off at a predetermined set temperature in response to the hot gas temperature; A second temperature sensor, which has a switch that turns off at approximately the same set temperature as the first temperature sensor, is fixed to the low-pressure gas pipe near the temperature sensor via a thermal resistance plate, and these temperatures By interposing each of the switches in the detector in series with the defrost control circuit, the life of the entire device is increased by several times the life of the temperature detector, and the maintenance cycle is lengthened.

Next, embodiments of the present invention will be described based on the drawings.

What is shown in FIG. 1 is a container refrigeration system to which the detection device of the present invention is applied, specifically, a refrigeration system that enables defrosting by hot gas bypass.

Before explaining the embodiments of the present invention, the refrigeration system will be explained based on FIG. 1. In FIG. 1, 1 is a compressor, 2 is an air-cooled condenser, 3 is a water-cooled condenser, and 4 is an evaporator. Reference numeral 5 denotes a temperature-sensitive expansion valve having a temperature-sensing section 5a, and these devices are connected through refrigerant pipes 6 to form a refrigeration cycle in which the evaporator 4 cools the air inside the refrigerator.

In FIG. 1, 7 is a liquid receiver integrated with an accumulator, 7a is a liquid receiving part, 7b is an accumulator part, 8 is a dryer, 9 is a liquid indicator, and 10 is a fan attached to the evaporator 4. ,
11 is a fan attached to the air-cooled condenser 2.

In the refrigeration cycle configured as described above, the high pressure gas pipe 6a connecting the discharge side of the compressor 1 and the inlet side of the air-cooled condenser 2 is connected to the compressor 1.
The hot gas discharged from each condenser 2,
3. Connect a hot gas bypass path 20 which bypasses the liquid receiving part 7a of the liquid receiver 7 and the temperature-sensitive expansion valve 5 to the evaporator 4, and connects the outlet side thereof to the expansion valve 5 and the evaporator 4. connected to the low pressure liquid pipe 6b between the
A hot gas valve 21 is interposed at the connection portion of the hot gas bypass path 20 to the high pressure gas pipe 6a, and by operating the hot gas valve 21, hot gas can be guided to the evaporator 4 and defrosted.

In the case shown in FIG. 1, an electromagnetic on-off valve 30 is provided on the downstream side of the liquid indicator 9, which closes in response to a defrost operation start command, to enable pump-down operation, and the condensers 2, 3 and A defrost circuit, that is, a compressor 1, is configured to confine refrigerant in a liquid reservoir including a liquid receiver 7a of the liquid receiver 7, and performs a defrost operation on a certain amount of the refrigerant confined in the liquid reservoir. , hot gas valve 21, hot gas bypass path 20, evaporator 4,
A quantitative outflow mechanism 40 is provided which flows out into a defrost circuit consisting of an accumulator section 7b of the liquid receiver 7.

This quantitative outflow mechanism 40 includes, for example, the on-off valve 3
Of the liquid reservoir part that performs pump-down operation and confines refrigerant by closing 0, an electromagnetic on-off valve 41 is installed at a position where a predetermined outflow amount can be obtained, with respect to the interposed position where the on-off valve 30 is installed. As shown in FIG. A certain amount of refrigerant is interposed in the high-pressure liquid pipe 6c near the side and confined in the high-pressure liquid pipe 6c between these intervening positions, so that it can flow out by closing the on-off valve 41 and opening the on-off valve 30. It is something.

Further, the amount of refrigerant set by the fixed amount outflow mechanism 40 is set to an optimum amount so that the steady operation performed after the defrost operation is always kept within the operable range regardless of the operating state, and the defrost time is not prolonged. It is.

The hot gas valve 21 is mainly an electric three-way valve that can control the valve opening degree to the hot gas bypass path 20 from 0% to 100% in proportion to the voltage, and controls the hot gas valve opening to the evaporator 4 from 0% to 100%. Using a proportional control valve that controls the amount of gas bypass to adjust the capacity and at the same time allows the entire amount of refrigerant circulating during frosting to flow through the hot gas bypass path 20, a controller 22 and a defrost start relay 2DX, which will be described later, are used. ₂ , it seems to be controlled by

In addition, in FIG. 1, 23 is the suction gas pipe 6e.
An energized/closed solenoid valve installed in the intake gas pipe 6e is connected in parallel to the capillary reach tube 24.
It is intervening.

This solenoid valve 23 supplies the suction gas refrigerant to the capillary reach tube 2 by closing the solenoid valve 23.
The refrigerant is returned to the compressor 1 through the refrigerant 4, and the amount of refrigerant circulated is reduced.The amount of refrigerant is reduced in this way when the outside temperature is high, when steady operation starts after defrosting, or when pulling down. This is to prevent the high and low pressures of the refrigerant from increasing and overloading, and due to the reduction in the amount of circulation, the amount of work of the compressor 1 is reduced, and the high pressure and the current value of the compressor motor are reduced. This allows the operating range to be expanded.

Further, the solenoid valve 23 detects the suction temperature of the evaporator 4, closes when the suction temperature exceeds a certain value to reduce the circulation amount, and opens when the suction temperature exceeds a certain value. , other high pressure or low pressure may be detected to control the opening/closing,
The suction temperature of the air-cooled condenser 2, that is, the outside air temperature may be detected, and the system may be closed when the outside air temperature is above a certain value, and opened when the outside air temperature is below a certain value.

In addition, in Fig. 1, 63L is a low pressure switch,
63H is a high pressure switch, 63CL is a high pressure control switch, 63QL is a hydraulic protection switch, and 63W is a water pressure switch.

Therefore, in the above configuration, the hot gas valve 21 is controlled by the output signal from the controller 22 and the command to start the defrost operation, and the opening/closing valve 30 is closed by the command to start the defrost operation to perform the pump down operation. Furthermore, the end of the pump down operation and the start of the defrost operation are mainly controlled using the low pressure switch 63L.

In addition, the defrost operation start command is mainly sent to the air pressure switch APS and, for example, 12
Defrost timer 2D with time as set time
and is used. In this case, the air pressure switch APS gives priority to the defrost timer 2D, and the air pressure switch APS
The operation of the APS is like resetting the defrost timer 2D.

The present invention is configured as described above and is for detecting the end of a defrost operation performed by a command to start a defrost operation. Next, an embodiment of the detection device of the present invention will be described with reference to FIG.

What is shown in FIG. 2 is a bimetal type first temperature detector 50 and a second temperature detector 5 which have switches 23D ₁ and 23D ₂ with the same set temperature for turning off.
1, and the first switch 23D with these switches 23D ₁
A temperature detector 50 and a second temperature detector 51 having a switch 23D ₂ are connected to the low pressure gas pipe 6d on the outlet side of the evaporator 4, and one first temperature detector 50 is connected to the low pressure gas pipe 6d on the outlet side of the evaporator 4.
is directly attached to the mounting plate 52, and the other second temperature sensor 51 is attached to the mounting plate 52 via a heat resistance plate 53 made of nylon resin or the like. By preventing heating to the second temperature detector 51, the actual hot gas detection temperature at the time of off operation is made different, and
The switches 23D ₁ and 23D 2 of the detectors 50 and 51 configured as described above are the switches 23D 1 and 23D ₂ that are turned on by the defrost command as described later.
The contact point of the defrost timer 2D and the defrost starting relay _2DX2 are connected in series.

The mounting plate 52 is fixed to a mounting band 54, and the mounting band 54 is fixed to the low pressure gas pipe 6d by bolt/nut fixing means or welding, and the first and second temperature detectors 50,
51 is provided with mounting flanges 50a and 51 facing the mounting plate 52, and is mainly provided with mounting screws 55.
When the heat resistance plate 53 is used, the flange 5 is fixed to the mounting plate 52.
It is inserted between 1a and the mounting plate 52, and is fixed by tightening them together with the mounting screws 55. The mounting positions of the first and second temperature detectors 50 and 51 are as follows:
Low pressure gas pipe 6d on the outlet side of the evaporator 4, suction gas pipe 6
It may be located anywhere in e, but a location where service can be provided from outside is preferable.

Further, the difference in temperature of the hot gas in the low pressure gas pipe 6d when the switches 23D ₁ and 23D ₂ in the first and second temperature detectors 50 and 51 are respectively turned off is due to The temperature is set in anticipation of the rise range in which the temperature of the hot gas flowing through the low pressure gas pipe 6d rises between the time when the defrost operation is completed and the time when the defrost operation is returned to normal operation. That's what I do.

If the thermal resistance plate 53 is used as shown in the drawing, the set temperatures at which the switches 23D ₁ and 23D ₂ of the first and second temperature detectors 50 and 51 turn off can be made the same. Since it can be constructed using specified parts, parts management can be simplified accordingly, and cost increase can be minimized by using two temperature detectors 50 and 51 that differ in hot gas detection temperature.

Next, the electric circuits of the controller 22 for regulating the temperature of the blown air by controlling the hot gas valve 21 and the respective control devices for controlling the defrost operation will be explained with reference to FIG.

What is shown in FIG. 3 is the electrical circuit of the refrigeration system shown in FIG. MF _1-1 , MF _1-2 ,
MF _1-3 and three outdoor fan motors corresponding to the three fans 11 attached to the air-cooled condenser 2.
Equipped with electrical equipment MF _2-1 , MF _2-2 , MF _2-3 , the power supply circuit of these electrical equipment is connected to a 200V or 220V low voltage power plug _P1 and a 380 to 415V or 440V high voltage power supply. Select one of the plugs P ₂ and connect it to the power supply, and connect the transformer Tr to the power supply circuit.
The controller 22 and the control circuits of each of the control devices are connected through the controller.

In FIG. 3, CB is a circuit breaker, OC is an overcurrent relay, 2X ₁ to 2X ₃ are auxiliary relays and their contacts, and 3-88 is an on/off switch. Further, in the power supply circuit, contacts without numbers are switching contacts that are switched by selecting the plugs P ₁ and P ₂ .

Although not shown, the controller 22 includes an input transformer, a power input device, a sensor input device, an operation input/output device, a central processing unit, and a relay output device. As shown, the return sensor RS is placed on the suction side of the evaporator 4 and detects the temperature of the return air from inside the refrigerator, that is, the suction air, and the supply sensor SS is connected to the outlet side of the evaporator 4 to detect the temperature of the blowing air.
A set point selector PS and an output display DP are connected to the operation input/output device, and the electric part 20M of the hot gas valve 21 and the electromagnetic part in the embodiment shown in FIG. 1 are connected to the relay output device. In addition to the solenoid relay 20SS of the valve 23, the auxiliary relays 2X ₄ and 2X ₅ , and the lamps AL and BL, the following relay circuits are included: 1 Parallel circuit of the normally open contacts of the auxiliary relay 2X ₄ and the defrost start relay 2DX ₂ and a series circuit with the solenoid relay _20LS1 of the on-off valve 30 for pump down operation. (Pump down control circuit) 2 Compressor protection thermostat 49, overcurrent relay 0
C, high pressure switch 63H, low pressure switch 63
L, hydraulic protection switch 63QL and compressor motor
Series circuit with MC's electromagnetic switch 88C.

3 The indoor fan motor attached to the evaporator 4 connects to the normally closed contact of the defrost start relay 2DX ₂ .
A circuit of the delay timer 2F of the MF _1-1 ..., a circuit in which a parallel circuit of the electromagnetic switch 88F of the indoor fan motor MF _1-1 ... and the defrost timer 2D is connected in series to the contact point of the delay timer 2F, and the circuit of the delay timer 2F of the indoor fan motor MF 1-1... Solenoid relay 20 for valve 41
A circuit in which a three-way parallel circuit with the LS ₂ circuit is connected in series.

and the following defrost control circuit in which the switches 23D ₁ and 23D ₂ of the first temperature detector 50 and the second temperature detector 51 constituting the detection device of the present invention are connected in series; A parallel circuit of the contacts of the air pressure switch APS, which issues a command to start operation, the defrost timer 2D, and the manual defrost switch 3D, and the normally open contact of the defrost relay 2DX ₁ , and the first and second temperature detectors that detect the end of defrosting. vessel 50,
51 switches 23D ₁ and 23D ₂ series circuit and the defrost relay 2DX ₁ , and a parallel circuit of the normally closed contact and the self-holding contact of the electromagnetic switch 88C for the compressor motor MC for the defrost relay 2DX ₁ . The defrost control circuit is connected in series with each circuit in the parallel circuit with the defrost starting relay 2DX ₂ connected in parallel through the defrost control circuit.

In Figure 3, CPD is a contact protection diode, GL and RL are lamps,
3-30L is a lamp switch, Y ₂ , U ₁ , G ₂ , G ₁
is a switch for switching between freezing operation and refrigeration operation.
In addition, the electric part 20M of the hot gas valve 21 is formed with a direct connection circuit, separate from the control circuit of the controller 22, through which the normally open contacts of the auxiliary relay _2X6 are interposed, so that the opening can be switched to 100%. It's summery.

In the above configuration, the air temperature is adjusted by the set temperature set by the set point selector CPS of the controller 22, and when the set temperature is lower than -5°C, for example, the air temperature is adjusted by the return sensor RS on the suction side. Compressor 1 based on
In addition, in the case of refrigeration operation at 5°C or higher, the hot gas valve 21 is controlled to an opening degree of 0 to 100% based on the sublicensor SS on the outlet side, and the opening degree is This is done by bypassing the hot gas at an appropriate flow rate.

During such freezing or refrigeration operation, the evaporator 4 may become frosted and the air pressure switch APS may be activated.
Alternatively, when the defrost timer 2D operates and a command to start the defrost operation is issued, the defrost operation is performed as follows.

First, when a defrost operation start command is issued as described above, the defrost relay 2DX ₁ is energized, the auxiliary relay 2X ₄ is demagnetized, the pump down control circuit is opened, and the solenoid relay 20LS ₁ of the on-off valve 30 is demagnetized. Then, the on-off valve 30 closes and pump down operation begins.

In this pump-down operation, the liquid refrigerant is trapped in the condensers 2 and 3, the liquid receiving part 7a of the liquid receiver 7, and the liquid pipe portion 6c leading to the on-off valve 30, and the low pressure of the refrigerant is reduced. When the low pressure becomes lower than the set value of the low pressure switch 63L, the low pressure switch 63L is turned off, and the compressor motor MC start/stop control circuit is activated.
The electromagnetic switch 88C of the motor (MC) is demagnetized, the compressor 1 is stopped, and the pump-down operation is completed.

Then, as the electromagnetic switch 88C is demagnetized, its normally closed contact closes, so the defrost start relay 2DX ₂ in the defrost control circuit is energized, the electric part 20M of the hot gas valve 21 is operated, and the opening degree is 100%. and the indoor fan motors MF1-1... are stopped, and at the same time, the relay ₂ connected in series with the solenoid relay 20LS2 of the on-off valve 41 constituting the quantitative outflow mechanism 40 is switched.
The normally closed contact of DX ₂ opens to open the quantitative outflow control circuit, the solenoid relay 20LS ₂ is demagnetized, the on-off valve 41 closes, and the normally open contact of the defrost start relay 2DX ₂ closes to The pump town control circuit is closed, and the on-off valve 30 is closed.
The solenoid relay _20LS1 is energized to open the on-off valve 30, and at the same time, the hot gas valve 2
1 is fully opened to the hot gas bypass path 20 side regardless of control by the controller 22, and the indoor fan motors MF _1-1 . . . are stopped.

As described above, by closing the on-off valve 41 and opening the on-off valve 30, each of the on-off valves 41, 3
A certain amount of liquid refrigerant trapped in the high pressure liquid pipe 6c between 0 and 0 will flow out, and this flow will cause the low pressure to rise and become higher than the set value of the low pressure switch 63L.
is turned on, the compressor 1 is started, a certain amount of the refrigerant is circulated through the defrost circuit, and the hot gas flowing into the evaporator 4 from the hot gas bypass path 20 performs defrosting.

Then, when the defrost is finished as described above,
the low pressure gas pipe 6 on the outlet side of the evaporator 4;
the first and second temperature detectors 50 and 51 provided in d;
Among them, the first temperature detector 50 is activated, the defrost control circuit is opened, the defrost relay 2DX ₁ is demagnetized, and the self-holding circuit of the defrost start relay 2DX ₂ is also released, and the solenoid relays 20LS ₁ , _20LS2 are both excited, the opening/closing valves 30 and 41 open, and the operation returns to freezing operation, or during refrigeration operation, the hot gas valve 21 shifts to opening control by the controller 22 and returns to normal operation.

Therefore, when the first temperature detector 50 operates normally, the hot gas temperature is determined by the switch 23.
The second temperature detector 51, which operates when the temperature is higher than the set temperature at which D ₁ and 23D ₂ turn off, does not operate at all because its contact 23D ₂ remains closed. The second temperature sensor 51 operates only after the bimetal of the first temperature sensor 50 malfunctions due to welding, etc., and can complete its lifespan, thereby extending the lifespan of the entire detection device. , each of the detectors 50,
This makes it possible to achieve a total lifespan of 51.

Although the embodiment described above uses two temperature detectors 50 and 51, three or more temperature detectors may be used, and the life of the entire detection device can be extended accordingly.

Further, the defrost control circuit is not limited to the example described above. For example, when controlling defrost only with a timer, a series circuit of a timer and two temperature detectors, and a series circuit of a contact point of the timer and a defrost start relay are used. circuit in parallel between the power supplies,
After the timer has counted a predetermined period of time, the contact closes to energize the defrost start relay and defrost starts, and when one of the temperature detectors opens, the defrost ends and the timer automatically returns. However, the contact may be open.

As described above, the present invention fixes the first temperature detector 50 to the low pressure gas pipe 6d on the outlet side of the evaporator 4, and has the switch _23D1 which is turned off at a predetermined set temperature in response to the hot gas temperature. , a switch 23D ₂ is installed in the low pressure gas pipe 6d near the first temperature detector 50, and is turned off at a set temperature that is approximately the same as the set temperature of the first temperature detector 50.
A second temperature detector 51 with a heat resistance plate 53 is fixed therebetween, and the switches 23D ₁ and 23D ₂ of these temperature detectors 50 and 51 are connected in series to the defrost control circuit. Even if the lifespan of each temperature detector 50, 51 is short, the lifespan of the entire device can be extended by using it under harsh conditions where it operates in response to the hot gas temperature, and maintenance by the user is reduced accordingly. This makes it possible to reduce the frequency of maintenance operations and reduce user maintenance man-hours. Furthermore, each temperature sensor 50,
Since the temperature sensor 51 is provided close to the low pressure gas pipe 6d, the completion of defrosting can be detected by either temperature sensor 50 or 51. Since the switch 23D ₂ is turned off at almost the same set temperature as the temperature detector 50, the first and second temperature detectors 50 and 51 have the same specifications. Just by adding the heat resistance plate 53,
Parts management can be simplified, and the temperature at the time of OFF operation can be made different with a simple configuration, so the cost increase can be minimized while using two types of temperature detectors 50 and 51 with different hot gas detection temperatures. It can be done.

[Brief explanation of the drawing]

Fig. 1 is a refrigerant piping system diagram showing an embodiment of the refrigeration system to which the detection device of the present invention is applied, Fig. 2 is a side view showing an embodiment of the detection device of the present invention, and Fig. 3 is the same as shown in Fig. 1. It is an electric circuit diagram of a refrigeration device. 4... Evaporator, 50... First temperature detector, 51
...Second temperature detector, 53...Heat resistance plate, 23
D ₁ , 23D ₂ ... switch, 6d ... low pressure gas pipe.

Claims (1)

[Scope of utility model registration request] This is a detection device for detecting the end of defrosting performed by flowing hot gas into the evaporator 4, and a switch is provided in the low pressure gas pipe 6d on the outlet side of the evaporator 4 and turns off at a predetermined set temperature in response to the hot gas temperature. 23D ₁ is fixed, and the low pressure gas pipe 6d near the first temperature detector 50 is turned off at a set temperature that is approximately the same as the set temperature of the first temperature detector 50. A second temperature detector 5 with an operating switch 23D ₂
1 is fixed via a heat resistance plate 53, and each of the switches 23D ₁ ,
1. A defrost end detection device for a refrigeration system, characterized in that a defrost controller _23D2 is connected in series to a defrost control circuit.