JPS6145147B2 - - Google Patents

Description

Detailed Description of the Invention In general, the amount of frost that adheres to the cooler of a refrigeration system (the cooler of an electric refrigerator will be explained below as an example) is determined depending on the usage conditions of the equipment, such as the number of times the door is opened and closed in the electric refrigerator, It is known that when the number of times water is poured into an ice tray is constant, the humidity is approximately proportional to the absolute humidity of the outside air temperature. FIG. 1 is an psychrometric diagram that shows the dry bulb temperature (outside air temperature)-absolute humidity characteristic using relative humidity (a: 100% relative humidity, b: 60% relative humidity) as a parameter. Figure 2 is an outside air temperature vs. frost amount/unit time characteristic diagram, Figure 3 is an outside air temperature vs. compressor operation Terama characteristic diagram until a certain amount of frost is reached, and Figure 4 is a conventional defrosting method and the present invention. FIG. 2 is a characteristic diagram of the outside air temperature and the cumulative operating time of the compressor between defrosts in the defrosting method. Curve A is the compressor operating time until the amount of frost builds up that reduces cooling performance. Regardless of the defrosting method, the cumulative operating time of the compressor must be set to be smaller than curve A. Curve B is for the conventional fixed-time defrosting method, and the lower the outside temperature, the shorter the compressor operating time is because the efficiency of the refrigeration cycle increases and heat leakage decreases. Line C also shows the case of the conventional integrating type defrosting method, which is not affected by outside temperature because it is a method that integrates the time by energizing a timer when the compressor is operating. Similarly, when the outside temperature is low, the operating rate decreases for the same reason as curve B, and the interval until defrosting becomes longer.As can be seen from A, B, and C, with the conventional method, frost formation Defrosting occurs much faster than the cooling performance deteriorates.

In consideration of the above, in the present invention, the cumulative operating time of the compressor between defrosts is extended when the outside temperature is low, as shown by broken line D or curve E.

Correspondence with conventional techniques and the points to be solved by the present invention will be explained in detail below.

The defrosting cycle of conventional refrigeration equipment is either a regular method in which defrosting is generally started at 1 to 2 a.m. using a 24-hour timer, or an integrated method in which defrosting is started when the cumulative operating time of the compressor reaches, for example, 8 hours. However, these things are hot and humid (high absolute humidity)
Since the time is set so that defrosting can be completed at times, there is a drawback that when the temperature is low and humidity is low (absolute humidity is low), the defrost heater is energized even if there is not enough frost. On the other hand, there are methods that indirectly measure the amount of frost adhering to the cooler by detecting the thickness of frost adhering to the cooler using a phototube or by detecting the pressure difference between the cold air inlet and the cold air outlet to the cooler. However, the former has the disadvantage that it is not possible to accurately detect the amount of frost due to the phototube becoming dirty, and the latter has the disadvantage that the pressure difference is extremely small, making the detector less accurate. It had the disadvantage that it required

The present invention was devised to eliminate the above-mentioned drawbacks, and takes into consideration the fact that even if the relative humidity is the same, when the outside temperature decreases, the absolute humidity also decreases, and the amount of frost formed per unit time also decreases. When the outside air temperature drops, a signal is obtained from a temperature detection means such as a bimetal thermostat, pressure type thermostat, or thermistor, and the time setting is changed based on that signal to lengthen the compressor's cumulative operating time.

The outline of the present invention will be explained below based on FIG. 5.
1 is an AC power supply, 2 is a defrost heater for melting frost attached to the cooler, 3 is a compressor for cooling the refrigerator or freezer compartment, and 4 is a fan motor for forced circulation of cold air. 5,
Reference numeral 6 denotes a control element consisting of, for example, a semiconductor switch, which controls the defrosting heater 2 and the compressor 3,
It controls the on/off state of the fan motor 4, and signal lines 8 and 9 from a control circuit 7 containing an electronic timer circuit are connected to each gate terminal. 10 is a power supply circuit for the control circuit 7; 11 is a pulse generation circuit that supplies clock pulses to the counter of the electronic timer circuit in the control circuit 7;
It has a frequency variable means for varying the frequency of the clock pulse in response to the temperature detecting means 12 for detecting the outside air temperature. Then, the pulse generation circuit 11
The number of clock pulses from the defrosting heater 2 is counted by a counter in the electronic timer circuit, and when a predetermined number is counted, a signal is sent from the signal line 8 to the gate terminal of the control element 5 to energize the defrosting heater 2. Reference numeral 13 denotes an internal temperature detection means for detecting the internal temperature of the refrigerator, and when the internal temperature of the refrigerator reaches a predetermined temperature or higher, a pulse signal is sent to the control circuit 7 and sent to the control element 6 via the signal line 9.
A pulse voltage is applied to the gate of compressor 3.
And the fan motor 4 is energized. 14 is a means for detecting the end of defrosting, which sends a signal to the control circuit 7 and turns off the control element 5 when the end of defrosting is detected.
The defrosting heater 2 is then cut off from being energized.

A series of operations related to FIG. 5 will be explained below.

1. First, when the temperature inside the refrigerator is higher than a certain set temperature, the control element 6 is turned ON by a signal from the inside temperature detection means 13, and the compressor 3 and fan motor 4 are operated. When the inside of the refrigerator is cooled to the set temperature by the operation of the compressor 3 and fan motor 4, the control element 6 is activated by a signal from the inside temperature detection means 13.
Turn OFF and stop compressor 3 and fan motor 4.

2. As described in the above section 1, the compressor 3 and the fan motor 4 perform intermittent operation in response to the signal from the internal temperature detection means 13 to maintain the internal temperature at a predetermined temperature. Pulse generation circuit 11 in the electronic timer circuit inside
When the cumulative operating time reaches a predetermined time by supplying a clock pulse from the control circuit 7, a pulse voltage is applied from the control circuit 7 to the gate terminal of the control element 5 via the signal line 8, and the defrosting heater 2 is energized.

3. When defrosting is completed, the control element 5 is turned off by a signal from the defrosting completion detection means 14, and the power supply to the defrosting heater 2 is cut off. On the other hand, since the temperature inside the refrigerator is rising due to the defrosting operation, the temperature inside the refrigerator 13 is activated to return to the cooling operation described in item 1 above.

In this way, the device of the present invention repeatedly performs the cooling operation and the defrosting operation, but the cumulative operating time mentioned in Section 2 above is determined by the number of clock pulses counted by the electronic timer circuit in the control circuit 7 and the period of the number of clock pulses. It is determined by the product. Therefore, in response to the temperature detection means 12, the frequency variable means in the pulse generation circuit 11 changes the period of the clock pulse continuously or stepwise, thereby changing the cumulative operating time of the compressor 3 in accordance with the outside temperature. be able to.

The specific structure of the pulse generating circuit 11 equipped with the temperature detecting means 12 and frequency variable means used in the present invention will be described below.

In FIG. 6, the temperature detection means 12 for detecting the outside temperature is composed of a resistor _R1 and an outside temperature sensing thermistor _RT , and the resistor _R1 and the outside temperature sensing thermistor _RT are connected in series to a DC power source E. It is connected to the.
The voltage V _T at the midpoint between the resistor R ₁ and the outside temperature sensing thermistor R _T is E·R _T /(R ₁ +R _T ).
Therefore, when the outside temperature is low, the resistance value of the outside temperature sensing thermistor R _T becomes large and the voltage V _T becomes high, and when the outside temperature is high, the resistance value of the thermistor _RT becomes small and the voltage V _T becomes low. In this way, changes in outside air temperature can be extracted as voltage changes (as shown in Figure 7). On the other hand, the pulse generation circuit 11 includes a frequency variable means 11a, a capacitor c,
It consists of a voltage comparison circuit 11b with hysteresis and a capacitor discharge circuit 11c. This frequency variable means 11a is a general-purpose OP/AMP (e.g.
TA7504) Connect the ○+ terminal of IC ₁ to the midpoint between the resistor R ₁ and the outside temperature sensing thermistor R _T , and connect the ○- terminal to the resistor R ₃ .
It is connected to the midpoint between the emitter terminal of the PNP transistor Q ₁ and the base terminal of the transistor Q ₁ via the output terminal and the resistor R ₂ . The capacitor C is connected to the collector terminal of the transistor _Q1 , and the midpoint between the capacitor C and the collector terminal is connected to the voltage comparison circuit 11b. The voltage comparator circuit 11b with this hysteresis is a general-purpose OP/AMP (e.g.
TA7504) Consists of IC ₂ , resistors R ₆ , R ₇ , R ₈ and constant voltage diode D, which are connected as shown in the figure. The resistor R ₆ and the constant voltage diode D provide a reference voltage V _ref to the IC ₂ , and the resistors R ₇ and R ₈ provide positive feedback from the output terminal of the IC ₂ to the non-inverting input terminal to provide hysteresis. Further, the capacitor discharge circuit 11c consists of resistors R ₄ and R ₅ and a PNP transistor Q ₂ ,
One end of the resistor _R4 connected to the collector terminal of the transistor _Q2 is connected to the midpoint between the collector terminal of the PNP transistor _Q1 and the capacitor C,
Resistor connected to the base terminal of transistor Q ₂
The terminal of _R5 is connected to the output terminal of _IC2 .

Now, if the outside temperature is low and the voltage V _T at the midpoint between the resistor R ₁ and the outside temperature sensing thermistor R _T is high, the voltage applied to the base terminal of the transistor Q ₁ is large, and the emitter terminal voltage and base terminal voltage are high. Since the voltage difference is small, a small current flows on the collector terminal side, and the charging time to the capacitor C becomes long. On the other hand, when the outside temperature is high and the voltage V _T is low, the voltage applied to the base terminal of transistor Q ₁ is small, the voltage difference between the emitter side and the base side becomes large, and a large current flows through the collector terminal side of capacitor C. The charging time will be shorter. The period of the clock pulse is determined by the length of time for charging the capacitor C. The connection between the midpoint between resistor R ₃ and the emitter terminal of transistor Q ₁ and the ○- terminal (inverting input terminal) of IC ₁ is used to perform a constant current effect on the emitter current according to the outside temperature. It's for a reason.

On the other hand, the "H" level inverted input voltage of IC ₂ is E _i
When _H , “L” level inverted input voltage is E _iL , “H” output voltage circle V _OH , “L” output voltage is V _OL and hysteresis width is △V, E _iH = Vref + △V/2,
E _iL = Vref - △V/2, and when the capacitor C is charged and the inverting input terminal voltage Ei (=V _C ) rises to E _iH , the output voltage V _p becomes V _OL and the inverting input terminal voltage Ei ( = V _C ) decreases to E _iL , V _O becomes V _OH . Also, when the output V _O of IC ₂ is "L", the transistor Q ₂ turns on and discharges the charge of the capacitor C through the resistor R ₄ , and when the output V _O of IC 2 is "H", the transistor Q ₂ turns off and stops discharging. do. In this way, the change in outside temperature is converted into the charging time of capacitor C for pulse generation, and the frequency is changed to make the counter of the electronic timer circuit count, so even if the number of counters is the same, the total cumulative time changes in response to outside temperature.

FIG. 11 shows an example of a control circuit 7 incorporating an electronic timer circuit, which is used to drive a control element 5 that controls the defrosting heater 2 and a control element 6 that controls the compressor 3 and fan motor 4. Drivers 21 and 22 are provided. Further, the pulse signal from the pulse generation circuit 11 is inverted by an inverter (not shown) and applied as a pulse signal 110 to one input terminal of a NAND circuit 23, and the output signal 24 of this NAND circuit 23 is A counter 25 counts, and an output signal 26 of the counter 25 is applied to a driver 21 and a NOT circuit 27. Further, the output signal 28 of the NOT circuit 27 is applied to one input terminal of the NAND circuit 23 and one input terminal of an AND circuit 29. Internal temperature detection means 1
The output signal 130 from the NAND circuit 23 and the AND circuit 29 is set to "H" when the temperature inside the refrigerator is higher than a certain set value, and "L" when the temperature is lower than the set value. applied to two input terminals. Furthermore, the output signal 140 from the defrosting end detection means 14 is applied to the counter 25,
When this addition is made, the contents of the counter 25 are cleared. The counter 25 is, for example, a multi-stage flip-flop circuit (usually 14 to 20 stages).
In order to make the sequence of FIG. 13 easier to understand, the five stages shown in FIG. 12 will be explained.

Assuming that the contents of the counter 25 are initially cleared, the output lines A, B of the counter 25,
C, D, and E are all "L", so the driver 21 is OFF, no signal is output to the signal line 8, and the control element 5 is also OFF, so the defrosting heater 2 is not energized. This state is cooling operation,
Since the output signal 26 is added to the input of the knot circuit 27, the output signal 28 is "H" during cooling operation.
It is becoming.

The input of the AND circuit 29 is the internal temperature detection means 1.
Since the output signal 130 of No. 3 and the output signal 28 of the knot circuit 27 are added, according to that logic, the output signal 30 becomes "H" only when the temperature inside the refrigerator is higher than a certain set value even during cooling operation. . This output signal 30 turns on the driver 22 and turns on the control element 6 through the signal line 9. As a result, the compressor 3 and fan motor 4 are energized.
In addition, the pulse signal 110 is input to the NAND circuit 23.
Since the output signal 130 and the output signal 28 of the chamber temperature detection means 13 are added, the output signal 24 is output only when the chamber temperature is high during cooling operation, as shown at 28 in FIG. 13, according to the logic. Appears as a pulse signal. This pulse signal 24 is counted by a counter 25, and in the case of the counter shown in FIG. 12, when 16 pulse signals are input, the output signal 2
6 switches from "L" to "H". For this reason,
The output signal 28 of the Nantes circuit 27 switches from "H" to "L", no pulse signal appears in the output signal of the Nantes circuit 23, and the counter 2
The contents of 5 are retained. As a result, the output signal 26
is "H", the driver 21 is turned on, the defrosting heater 2 is energized, and the output signal 30 is "L".
Then, driver 22 is turned off and compressor 3
And the power supply to the fan motor 4 is cut off. This state is the defrosting operation. When defrosting is completed, an output signal 140 is output from the defrosting end detection means 14, and this signal is input to the reset terminal of the counter 25, so that the contents of the counter 25 are cleared. Therefore, the defrosting operation returns to normal cooling operation.

FIG. 14 shows another embodiment of the apparatus of the present invention, in which the timing at which electricity starts to be applied to the defrosting heater is changed by varying the number of clock pulses counted by a counter in accordance with the outside temperature. 14th
Portions other than those shown are the same as those in FIG. 11.

Output lines C, D, and E are drawn out from each stage F ₂ , F ₃ , and F ₄ of the flip-flop circuit in the counter 25 and are input to the frequency division ratio circuit 31 . Output line E is connected to one input of AND circuit 32, output lines C and D are connected to two inputs of AND circuit 33, and the outputs of each AND circuit 32 and 33 are connected to two inputs of OR circuit 34. The output line 26 of the OR circuit 34 is connected to the output line 26 of the OR circuit 34. Further, the output line 120 of the outside air temperature detection means 12 is configured to output an output of "H" when the outside air temperature is higher than a certain set value, and output of "L" when it is lower than a certain set value. This output line is connected to one input of the AND circuit 33 and to the input of the NOT circuit 35, and the output of the NOT circuit 35 is connected to one input of the AND circuit 32.

The control operation shown in FIG. 14 will be explained below. Since the output line 120 is "H" when the outside temperature is high, the output of the AND circuit 33 becomes "H" only when the output lines C and D are respectively "H". Also, one input of the AND circuit 32 is "L" because the state of the output line 120 is inverted via the NOT circuit 35, and therefore, regardless of the state of the output line E, the output of the AND circuit 32 is becomes "L". Since the respective outputs of the AND circuits 32 and 33 are input to the OR circuit 34, the output of the AND circuit 33 appears on the output line 26 of the OR circuit 34. As a result, when output lines C and D each become "H", output line 2
6 becomes "H". Further, when the outside temperature is low, the same operation as above is performed, and when the output line E becomes "H", the output line 26 becomes "H".

Here, when the counter 25 is as shown in FIG. 12, referring to the sequence in FIG. 13, the output lines C and D become "H" because the counter 25
This is when 12 pulses are input to the output line E.
becomes "H" when 16 pulses are input.

As explained above, even when the frequency of the clock pulse is fixed, by using the variable division ratio circuit 31, the defrosting cycle can be lengthened or shortened depending on the outside temperature, just like changing the frequency of the clock pulse according to the outside temperature. It is something that can be done.

As described above, the present invention is capable of automatically changing the cumulative operation time of the compressor from one defrosting to the next defrosting according to the outside temperature, so that the amount of frost adhering is small and the defrosting effect is lower than in the past. The defrost heater is not energized when it is not needed, an appropriate defrost cycle can be obtained, and wasted power consumption can be completely eliminated. If the frequency of the clock pulse is varied in an analog manner, detailed time control that follows changes in the outside temperature can be performed, and if the number of clock pulses counted by the counter is varied according to the outside temperature, the above-mentioned method can be performed. This has the remarkable effect of being able to achieve the objective with a circuit that is extremely simple compared to conventional circuits.

[Brief explanation of the drawing]

Figure 1 is an psychrometric diagram showing the dry bulb temperature (outside air temperature)-absolute humidity characteristic relative humidity (a: relative humidity 100%,
b: Relative humidity 60%) as a parameter, Figure 2 is an outside air temperature vs. frost amount/unit time characteristic diagram, and Figure 3 is an outside air temperature vs. compressor operating time characteristic until a certain amount of frost is reached. Figure 4 shows the outside air temperature vs. cumulative operating time characteristic of the compressor between defrosts in the conventional defrosting system and the defrosting system of the present invention, and Figure 5 shows an outline of the defrosting system of the present invention. 6 is an electric circuit diagram of the outside temperature sensing means and pulse generation circuit used in the device of the present invention, and FIG. 7 is a diagram showing the relationship between V _T input to the non-inverting input terminal of IC ₁ and outside temperature. Characteristic diagrams, Figure 8 is a clock pulse waveform diagram when the outside temperature is low, Figure 9 is a clock pulse waveform diagram when the outside temperature is high, Figure 10 is a characteristic diagram of the outside air temperature and clock pulse frequency, and Figure 11. 12 is an explanatory diagram of a counter circuit used in the device of the present invention, FIG. 13 is a time chart of the device of the present invention, and FIG. 14 is an electric circuit diagram of the control circuit used in the device of the present invention. 1 shows a main part electric circuit diagram of an embodiment. 2...Defrost heater, 4...Compressor,
11...Pulse generation circuit, 12...Outside temperature detection means.

Claims (1)

[Claims] 1. In a defrosting control device that integrates the operating time of the compressor during the refrigeration cycle using a timer device and starts defrosting operation by energizing the defrosting heater when the timer reaches a predetermined time, clock pulses are counted by a counter. It has an electronic timer circuit that controls the time by converting changes in outside temperature into the charging time of a capacitor for pulse generation, and changes the frequency of the clock pulse in response to a signal from the outside temperature detection means using a frequency variable means that changes the frequency. This defrosting control device is characterized in that the timing at which electricity starts to be applied to a defrosting heater is changed by varying the number of clock pulses by a counter in an analog manner or by varying the number of clock pulses counted by a counter according to the outside temperature.