JPH0345305B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a defrosting control device for a vehicle refrigerator, and particularly to a defrosting control device for automatically removing frost generated in a refrigerator selectively driven by a vehicle engine and an on-vehicle motor. Relating to a control device to be removed.

[Prior Art] In some conventional automatic defrosting control devices, defrosting is started by detecting the core differential pressure of the evaporator, but this is due to variations in the core itself or tolerances in the terminal voltage and rotation speed of the fan motor. As a result, the core differential pressure fluctuated greatly, and in some cases, defrosting was impossible.

In addition, in the defrost start method of the conventional timer-type automatic defrost control device, a defrost start signal is generated at fixed time intervals after the refrigeration switch is turned on, but every time the refrigeration switch is turned off, the defrost start signal is generated again for the above fixed period of time. When the freezer is temporarily turned off, such as during delivery, defrosting is not performed. moreover,
If defrosting is performed at regular intervals, there is a possibility that the defrosting operation will be performed even when there is no frost, which is wasteful.

[Problems to be Solved by the Invention] The present invention provides a constant control system for generating a defrosting signal even when the operation of the refrigerator is temporarily stopped due to shutoff of an engine switch or the like while the refrigerator is being driven by the vehicle engine. It is an object of the present invention to provide a defrosting control device for a vehicular refrigerator, which does not require time measurement each time and thereby ensures defrosting.

[Means for Solving the Problems] The present invention provides a refrigerator in which a condenser, an expansion valve, and an evaporator are sequentially connected to a refrigerant compressor that is selectively driven by a vehicle engine or an on-vehicle motor. a bypass circuit that allows refrigerant to flow by bypassing the expansion valve; a switching valve that switches the refrigerant supplied to the condenser and the expansion valve to the bypass circuit in response to a defrosting signal; and a control that outputs a control signal to the switching valve. means, the control means includes a first timer circuit that generates the defrosting signal when a first predetermined period of time has elapsed after the refrigerator starts operating; and a first timer circuit that generates the defrosting signal when the compressor is driven by the engine. When the first
a second timer circuit that causes the first timer circuit to continue counting time for a second predetermined time if the operation of the compressor stops within a predetermined time; If the refrigerator stops operating within the first predetermined time while being driven by the motor, the clocking of the first timer circuit is canceled and the refrigerator continues to operate for the first predetermined time. To provide a defrosting control device that starts defrosting only when the device is operated.

[Operations and Effects] According to the above means, when the first timer circuit is driven by the engine, the first timer circuit generates the defrosting signal after the first predetermined time has elapsed, but the refrigerator If the operation of the refrigerator stops, the second timer circuit instructs the first timer circuit to continue counting for a second predetermined time period, so even if the refrigerator operation stops, the refrigerator cannot be defrosted. This prevents a reduction in refrigeration capacity due to frost formation.

On the other hand, when the refrigerator is driven by a motor, if the refrigerator stops operating within the first predetermined time, the second timer circuit cancels the timing of the first timer circuit, and the refrigerator stops operating. Defrosting is started only after continuous operation for the first predetermined period of time; however, when driven by a motor, the freezer is closed and the frequency of frost formation is low, resulting in unnecessary repeated defrosting of the freezer. I don't have to worry about it.

[Example] An example in which the example is applied to a refrigerated vehicle shown in the figure will be described below.

In Fig. 1, the refrigerator includes a freezer 1 for transporting cargo at a constant temperature, a cooling unit 3 for cooling the inside of the freezer 1, a condensing unit 2 for condensing and liquefying refrigerant, and a vehicle engine (not shown). compressor 4 driven by
, an electromagnetic clutch 5 that connects and connects the compressor 4 and the engine, and a standby unit 6 that includes another compressor 6a, a standby motor 6b, and a V-belt 6c that can be driven by a commercial power source so that cooling can be performed even when the engine is stopped. Equipped with.

Next, referring to FIG. 2, the refrigeration cycle of the refrigerator will be explained. During normal cooling operation, the compressor 4 or 6a makes the refrigerant high temperature and high pressure and compresses and discharges it.
The compressor 4 is driven during main operation, and the compressor 6a is driven during standby operation. Compressor 4
Alternatively, the gas refrigerant that exits 6a passes through check valve 7 or 8 and reaches three-way solenoid valve 9. When the three-way solenoid valve 9 is cooled, arrow A is open and the valve enters the condenser 10.
The refrigerant condensed and liquefied in the condenser 10 passes through the check valve 1
1. The condensed liquid enters the receiver 12 where it is stored, and only the complete liquid is removed by the dryer 13, and then the expansion valve 1
Send to 5. The sight glass 14 is used to visually observe the amount of refrigerant filled. The solenoid valve 16 is closed during cooling, and the refrigerant flows in the direction of arrow A. The expansion valve 15 is a temperature-type automatic expansion valve that serves as a pressure reducing means and expands the liquid refrigerant under reduced pressure to turn it into a low-temperature, low-pressure atomized refrigerant. The evaporator 17 is kept at a low temperature by the expansion valve 15.
The refrigerant, which has been reduced to a low pressure, exchanges heat with the air in the freezer 1.

The accumulator 18 stores liquid refrigerant that has not been vaporized by the evaporator 17 and returns only the gas to the compressor 4 or 6a.

During defrosting, the three-way solenoid valve 9 and the solenoid valve 16 are energized, the valves are opened, and the refrigerant flows in the direction of arrow B.
The high-temperature, high-pressure refrigerant flows directly into the evaporator 17 and melts the frost that has adhered to the evaporator 17. Temperature sensing cylinder 19a of defrosting thermostat 19
is attached to the outlet pipe of the evaporator 17 to detect the temperature of the outlet pipe of the evaporator 17. If the detected temperature is below 4°C, it is determined that frost still remains and a defrosting thermostat (not shown) is activated. The contact 19b of the defrosting thermostat (not shown) is closed, and when the temperature reaches 4° C. or higher, it is determined that defrosting has ended, and the contact 19b of a defrosting thermostat (not shown) is opened.

Next, the operation will be explained with reference to the electric circuit diagram of the apparatus of the present invention shown in FIG.

First, cooling and cold storage operation driven by an on-vehicle engine will be explained. Turn the engine key switch 21 for engine drive into ignition (IG). Since the commercial power supply 29 is not applied now, the motor switching relays 32, 33, 34, 35, and 36 are not energized and the contacts are 32a, 33a, 34a, 35a, and 3, respectively.
It is closed on the 6a side. Here, turn on the frozen switch 22.
When turned on, if the set value of the refrigerator interior thermostat 23 is lower than the current temperature inside the refrigerator, the contact 23a is closed, and the main relay 24 is energized and the contact 24a is turned on.
becomes closed. At this time, capacitor motor relay 2
7 and evaporator motor relay 28 are energized, contacts 27a and 28a are closed, and capacitor motor 10a and evaporator motor 1
7a is driven. At the same time, the electromagnetic clutch 5 is also energized, the compressor 4 is driven, and cooling is started.
Next, for cold storage, when the temperature inside the refrigerator falls below the set value of the internal thermostat 23, the contact 23a is opened, all the above-mentioned drives are stopped, and the refrigerator is kept cold.

The second cooling and cold preservation operation when driving the on-vehicle motor will be explained. When the commercial power supply 29 is applied, DC power is supplied through the transformer 30 and the rectifier 31. At this time, in-vehicle motor switching relay 3
2, 33, 34, 35, 36 are energized, and each movable contact is connected to each fixed contact 32b, 33b, 34b, 35.
b, 36b are switched. Here, frozen switch 22
When turned ON, if the set value of the refrigerator thermostat 23 is lower than the current temperature inside the refrigerator, the contact 23a is closed, and the main relay 24 is energized, and the contact 24 is closed.
a Closed. At this time, capacitor motor relay 2
7 and evaporator motor relay 28 are energized, contacts 27a and 28a are closed, and capacitor motor 10a and evaporator motor 17a are driven. At the same time, the motor drive relay 38 is energized, the contact 38a is closed, the motor 6b is driven, and the compressor 6a is driven via the power transmission V-belt 6c. Cooling is started in this way. Next, when the temperature inside the refrigerator falls below the set value of the internal thermostat 23, the contact 23a is opened, and the drive of the compressor 6a and vehicle motor 6b are all stopped, and the refrigerator is kept cold.

The defrosting control circuit in the apparatus of the present invention will be explained with reference to FIGS. 4 and 5. There are two ways to start defrosting: manual defrosting using the defrost switch 25 and timer-type automatic defrosting using the defrost control circuit 100.This automatic defrosting can be performed using vehicle engine drive or vehicle motor drive. Control is performed differently depending on the situation.

In the case of manual defrosting, the conditions for defrosting are that the defrosting thermostat contact 19b is closed and that cooling is in progress. Defrost switch 25
When turned ON, the defrosting relay 26 is energized and the movable contact is switched to the contact 26b side. The defrost switch 25 is a snap switch that is turned off when the user releases his or her hand. At this time, since the terminal of the defrosting control circuit 100 is connected via the diode 106,
The defrosting relay 26 is energized and a self-holding circuit is formed. As a result, the three-way solenoid valve 9 and the solenoid valve 16
is energized, the defrosting cycle is formed, and defrosting is started.

To complete defrosting, when the temperature of the outlet pipe of the evaporator 17 reaches 4° C. or higher, the contact 19b of the defrosting thermostat 19 is opened and the defrosting relay 26 is no longer energized. As a result, the contacts of the defrosting relay 26 are set to 26.
Switches to mode a and returns to cooling operation. A case will be explained in which automatic defrosting is performed by driving the vehicle engine. The defrost control circuit 100 terminal is a power source for the second timer circuit 102 and the first timer circuit 105. The terminal is grounded. Here, regarding the potential within the defrosting control circuit 100, when the potential is high, it is set to the "1" level, and when the potential is low, it is set to the "0" level.

During cooling operation, a "1" level potential is input from the refrigeration switch 22 to the AND gate circuit 101 via the terminal of the defrosting control circuit 100. Furthermore, a “0” level potential is applied to the terminal of the defrosting control circuit 100 and input to the inverter 107 . Inverter 107 inverts the input "0" level and outputs it. The “0” level potential input to the inverter 107 is inverted to a “1” level potential and input to the AND gate circuit 101. When a "1" level signal is applied to both inputs, the AND gate circuit 101 generates a "1" level signal, so in this case, it generates a "1" level output, and the timer circuit 101
Enter into 2.

The timer circuit 102 outputs the "1" level when the "1" level is input, but when the "0" level is input, the timer circuit 102 outputs the "1" level for a fixed time (t _A ), and outputs the "1" level for a fixed time (t A ). When it exceeds t _A ), it switches to the "0" level. Timer circuit 1 during cooling operation
02 outputs the "1" level. The terminal of the defrosting control circuit 100 is the terminal 24 of the main relay 24.
a, and serves as an input signal to the OR gate circuit 103 and an output power source to the terminal of the defrosting control circuit 100. When the timer 105 times out, it goes to the "1" level, and the output power at that time is taken from the terminal. The OR gate circuit 103 outputs a "1" level if either or both inputs are at a "1" level.
During cooling operation, the output is at “1” level.
Input to AND gate circuit 104. AND gate circuit 104 has the same function as AND gate circuit 101. The terminal of the defrosting control circuit 100 is connected to the terminal 26b of the defrosting relay 26, and is input to the inverter 108 at the "0" level during cooling operation.
Inverter 108 has the same function as inverter 107. The potential input to the inverter 108 at the “0” level is inverted to the “1” level and input to the AND gate circuit 104. AND gate circuit 1
04 inputs a “1” level signal to the timer circuit 105. When the “1” level is input, the timer circuit 105 measures a certain time (t _B ) and outputs the “1” level that exceeds the certain time (t _B ) to the defrosting control circuit 1.
Occurs on the 00 terminal. As a result, the defrosting relay 26 is energized and the contact 26b side is closed. At this time, since the terminal of the defrosting control circuit 100 is electrically connected through the diode 106, the defrosting relay 26 is energized, a self-holding circuit is formed, and defrosting operation begins. At the same time, the “1” level is input to the inverter 108, so the “0” level is input to the AND gate circuit 104.
The level is entered. At this time, the output of the AND gate circuit 104 becomes "0" level and the timer circuit 1
05 is a "0" level output. At the time when defrosting is completed, a "1" level is input to the timer circuit 105 to start counting a predetermined time (t _B ). With the above configuration, when the refrigerator is stopped by the key switch 21 or the freezing switch 22,
The terminal is at the "0" level, the terminal is at the "0" level, therefore the AND gate circuit 101 is at the "0" level, and the signal is input to the timer circuit 102 at the "0" level. The timer circuit 102 outputs the "1" level for the time _tA , and the OR gate circuit 103 outputs "1".
Since the terminal of the AND gate circuit 104 is "0", the inverter 108 outputs the "1" level, and the timer circuit 104 outputs the "1" level.
This is to continue the time measurement of 5. Timer circuit 1
After timer 02 has counted the time _tA , it becomes a "0" level output and the timer circuit 105 is released from counting time. Also,
When the refrigerator is re-driven within time _tA , the timer circuit 102 cancels timing and continues outputting the "1" level. Timer circuit 10 when the refrigerator is temporarily stopped
2, the timer circuit 105 for a certain period of time ( _tA )
This allows the operation of the system to continue.

Note that the combination of the first timer circuit 105 and the second timer circuit 102 defrosts the refrigerator at first predetermined time intervals when the vehicle engine is driving the refrigerator. Conventionally, when the key switch is turned off, the timing is canceled and defrosting cannot be performed, resulting in a decrease in performance.
When this occurs, defrosting is started at a second predetermined time to ensure that defrosting is performed.

A case will be described in which automatic defrosting control is performed by driving an on-vehicle motor.

Defrost control circuit 1 when driven by on-vehicle motor
The terminal 00 becomes the “1” level and is input to the inverter 107. At this time, since the "0" level is input to the AND gate circuit 101, the output also becomes the "0" level, and the timer circuit 102 does not operate. The operation of the timer circuit 105 will depend on an input signal applied to a terminal of the defrost control circuit 100. Since the terminal of the defrosting control circuit 100 is connected to the terminal 24a of the main relay 24, the timer circuit 105 measures a certain period of time (t _B ) only during the cooling operation, and the timing is canceled when the cooling operation is started.

In other words, when the refrigerator is driven by the on-vehicle motor, there is generally little frost formation, so there is no need to defrost continuously and repeatedly.Therefore, when the refrigerator is stopped, for example, the internal thermostat is used to keep the refrigerator cool. When the device starts operating, the conventional timing is canceled to prevent unnecessary defrosting.

Therefore, when the motor is driven, defrosting is started only when the cooling operation continues for a continuous period of time (t _B ). Also, the operation of each part to start defrosting and the end of defrosting are the same as when the engine is running.

In this embodiment, the timing for starting automatic defrosting is determined by a timer circuit, but other methods may be used to detect the end of defrosting.

Further, in this embodiment, defrosting control is performed using a defrosting control circuit, but a combination of a commercially available timer alone and a relay may also be used.

[Brief explanation of drawings]

FIG. 1 is a layout diagram of a refrigerator installed in a refrigerator truck. FIG. 2 is a diagram showing a refrigeration cycle of the refrigerator shown in FIG. 1. FIG. 3 is a configuration diagram of a defrosting control device according to the present invention. FIG. 4 is an electrical circuit diagram of the defrosting control circuit in FIG. 3. FIG. 5 is an operational diagram of the defrosting control circuit in FIG. 4. Explanation of symbols: 1... Refrigerator truck, 2... Capacitor unit, 3... Cooling unit, 4... Compressor, 5... Electromagnetic clutch, 6... Standby unit, 6a... Compressor, 6b... Vehicle mounted motor,
9...Three-way solenoid valve, 10...Capacitor, 10b
...Capacitor motor, 16...Solenoid valve, 17...
... Evaporator, 17a... Evaporator motor, 19... Defrosting thermostat, 100... Defrosting control circuit, 102... Timer circuit, 105...
timer circuit.

Claims (1)

[Claims] 1. A condenser, an expansion valve,
A refrigerator in which evaporators are connected in sequence includes a bypass circuit that allows refrigerant to flow bypassing the condenser and the expansion valve, and a refrigerant that is supplied to the condenser and the expansion valve to be sent to the bypass circuit in response to a defrosting signal. A switching valve for switching, and a control means for outputting a control signal to the switching valve, and the control means generates the defrosting signal when a first predetermined time elapses after the refrigerator starts operating. a first timer circuit, and if the operation of the refrigerator stops within the first predetermined time while the compressor is being driven by the engine, the timing of the first timer circuit is set to a second predetermined time; a second timer circuit that causes the compressor to continue for a certain period of time; A defrosting control device for a vehicular refrigerator, characterized in that the defrosting control device starts defrosting only when the first timer circuit cancels timing and the refrigerator continues to operate for the first predetermined period of time.