JPH0330779Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention relates to an anti-freeze device for a refrigeration or cooling device used, for example, in an automobile.

(Conventional Example) Conventionally, as this type of anti-freeze device, one disclosed in, for example, Japanese Utility Model Application Laid-open No. 56-71622 has become publicly known. FIG. 6 shows a circuit diagram according to this conventional example, in which a thermistor Th ₁ for detecting the temperature of an evaporator (not shown) and a resistor 70 are connected between the power supply and ground, and the output voltage of the thermistor Th ₁ is is applied to the inverting input terminals of comparator _OP1 and comparator _OP2 . On the other hand, a resistor 7 connected in series between the power supply and ground is connected to the non-inverting input terminal of the comparator _OP1 .
The voltage determined by the division ratio of 1.72 is also
A voltage determined by the division ratio of resistors 73 and 74 connected similarly to the resistors 71 and 72 is applied as a reference voltage to the non-inverting input terminal of OP ₂ , respectively. The comparator OP ₁ and the comparator OP ₂ each have a hysteresis characteristic due to the resistors 75 and 76 connected between the non-inverting input terminal and the output terminal.

The output terminal of the comparator OP ₁ is connected to the non-inverting input terminal of the comparator OP ₃ via a parallel circuit of a resistor 77 and a diode 78, and the non-inverting input terminal is grounded via a capacitor 79.

On the other hand, a voltage determined by a division ratio with a resistor 8081 connected in series between the power source and the ground is input as a reference value to the inverting input terminal of the comparator _OP3 . The cathodes of diodes 82 and 83 are connected to the output terminal, the anode of diode 82 is connected to the non-inverting input terminal of the comparator OP ₂ , and the anode of diode 83 is connected to the connection point between resistors 84 and 85, which will be described later. Connected.

Resistors 84, 85, 86 are connected in series between the power supply and ground, and the connection point of resistors 84, 85 is
The anode of a diode 87 whose cathode is connected to the output terminal of the comparator OP ₂ is connected to the resistor 8
The base of a transistor 88 is connected to the connection point between the transistors 5 and 86.

The emitter of the transistor 88 is grounded, and the collector is connected to a power source via an excitation coil 89a of a relay 89. Further, one end of the normally open contact 89b is connected to a power source, and the other end is connected to the electromagnetic clutch 12.

(Problems to be Solved by the Invention) However, in the above conventional example, as shown in FIG. 7, the temperature of the evaporator is below the freezing temperature for a predetermined period of time. In other words, the evaporator is cooled by starting the refrigeration and air conditioning equipment, and the evaporator temperature and the interior temperature gradually decrease, but the comparator
Due to the hysteresis characteristic of OP ₂ , the comparator in T _2
OP2 does not output an "L" signal, and the evaporator temperature further decreases to around _T1 . At this temperature, the comparator _OP1 outputs an "L" signal and the time constant circuit constituted by the resistor 77 and capacitor 79 starts discharging.

However, in the early stages of starting the cooling system, the 7th
As shown in the region a in the figure, the evaporator temperature rises and falls in a relatively short cycle compared to the time constant _t1 of the time constant circuit, so the outputs of both comparators _OP2 and _OP3 are "H".
The condition remains the same.

When the evaporator passes through this initial state and is cooled down to a temperature _T1 or lower for more than _t1 hour, the discharge of the compressor 79 is completed, so that the comparator
_OP3 outputs an “L” signal and stops the compressor operation. At this time, the first comparator _OP2 also outputs an "L" signal due to the action of the diode 82. As a result, the evaporator temperature increases to T ₁
Even if the output _of comparator OP ₃ becomes "H" _at around ₂ outputs an "H" signal, the compressor starts operating again.

Therefore, in the conventional example described above, the compressor operation is stopped only after the evaporator temperature is maintained below the freezing temperature _T1 for a predetermined time period _t1 or more, so that freezing of the evaporator is promoted during this time, and after the compressor is stopped, There is a problem in that it takes time for the evaporator temperature to rise to a predetermined temperature, prolonging the stop time of the compressor, and reducing cooling efficiency.

Therefore, this invention solves the drawbacks of the conventional example, which are caused by controlling the compressor on and off below the freezing temperature of the evaporator. The task is to provide equipment.

(Means for solving the problem) The main points of this invention are: an evaporator sensor that detects the temperature of the evaporator; an air temperature sensor that detects the temperature of the air that has passed through the evaporator; a second comparing means for comparing the output of the sensor with a predetermined value;
As a result of the comparison means, if the output of the air temperature sensor is greater than or equal to a predetermined value, the first set value is output, and if the output of the air temperature sensor is less than or equal to the predetermined value, the first set value is output. Thermo reference voltage setting means for outputting a high second set value; and a timer for continuing output of the second set value for a predetermined time when the second set value is set by the thermo reference voltage setting means. and a first comparing means for comparing the output of the evaporator sensor with the first or second setting value set by the thermo reference voltage setting means, and the output from the first comparing means. and drive control means for controlling the compressor on and off.

(Function) Therefore, the temperature of the air passing through the evaporator is detected, and when the temperature of the air passing through the evaporator is above a predetermined temperature, the compressor is turned on and off near the freezing temperature, and when the temperature falls below the predetermined temperature, the compressor is turned on and off. , the on-off temperature of the compressor was raised for a predetermined period of time to prevent the evaporator from being kept below freezing for a long period of time.
The above-mentioned problems can be achieved.

(Example) Hereinafter, an example of this invention will be described with reference to the drawings.

In Figure 2, the automotive refrigeration and cooling equipment is
An inside air inlet 2 and an outside air inlet 3 are formed in two parts on the most upstream side of the ventilation duct 1, and an inside/outside air switching door 4 is provided at the divided part. The air to be introduced into the ventilation duct 1 can be selected between inside air and outside air.

The blower 5 is for sucking air into the ventilation duct 1 from the inside air inlet 2 and the outside air inlet 3 and sending it to the downstream side, and an evaporator 6 and a heater core 7 are sequentially arranged on the downstream side of the blower 5. ing.

The evaporator 6 is connected with piping together with a compressor 8, a condenser 9, a liquid tank 10, and an expansion valve 11 to form a refrigeration/cooling cycle, and the air passing through the evaporator 6 is cooled. Further, the compressor 8 is connected to an electromagnetic clutch 12.
The electromagnetic clutch 12 is connected to an engine (not shown) as a drive source, and the drive is stopped by turning on and off the electromagnetic clutch 12.

The heater core 7 is inserted into a hot water cycle in which engine cooling water (not shown) circulates, and the heater core 7 also heats the air passing through it, and is disposed in a heating passage 13 formed on the side of the ventilation duct 1. There is. A bypass passage 14 that bypasses the heater core 7 is formed on the opposite side of the heating passage 13, and the air that has passed through the bypass passage 14 or the heating passage 13 merges on the downstream side of each, as shown in the figure. Air is blown into the vehicle interior from the air outlet that does not. Furthermore, an air mix door 15 is provided in front of the heater core 77, and the heating passage 13
The ratio of the air passing through the bypass passage 14 to the air passing through the bypass passage 14 can be adjusted depending on the position thereof.

The control circuit 16 is attached to the main body of the evaporator 6 and detects the temperature of the evaporator sensor 17, which detects the temperature of the evaporator 6, and the temperature of the air passing through the evaporator 6, which is disposed behind the evaporator 6. Air temperature sensor 1 to detect
8, the vehicle interior temperature Tr from the vehicle interior temperature sensor 19 that detects the vehicle interior temperature, and the solar radiation sensor that is installed at a position that receives solar radiation at the top of the dash board and detects the amount of solar radiation that enters the vehicle interior, for example. sensor 2
The amount of solar radiation Ts from 0, the outside air temperature Ta from the outside air temperature sensor 21 that detects the outside air temperature, and the set temperature from the temperature setting device 22 that sets the temperature inside the vehicle.
and Td respectively, and the electromagnetic clutch 12
control the intermittency of

FIG. 1 shows an embodiment of this control circuit 16, in which 23 is a first comparison circuit constituting a first comparison means, 24 is a second comparison circuit constituting a second comparison means, 25 is a timer, 26 is a drive control circuit which constitutes a drive control means together with the electromagnetic clutch 12, 27 is a variable thermo circuit, and 28 is a general signal calculation circuit.

The first comparison circuit 23 has resistors 29 and 30 connected in series between the power supply side and the ground.
A voltage determined by the division ratio is applied as a reference voltage to the non-inverting input terminal of the comparator 32 via the resistor 31, while the voltage of the evaporator sensor 17 consisting of the temperature detection element 17a and the resistor 17b is applied to the inverting input terminal. An output signal is applied via resistor 33.
Further, a resistor 34 is connected between the non-inverting input terminal and the output terminal, and the cathode of a diode 35 is connected to the output terminal, and the anode of the diode 35 is connected to a drive control circuit 26 to be described later. ing.

The first comparison circuit 23 outputs an "L" signal when the temperature of the evaporator 6 becomes lower than the temperature corresponding to the reference voltage _E3 .

In the second comparison circuit 24, a resistor 36 provided on the input side is connected to a non-inverting input terminal of a comparator 37,
The temperature detection element 18a and the resistance 1 are connected through the resistance 36.
The output signal of the air temperature sensor 18 composed of the air temperature sensor 8b and the air temperature sensor 8b is inputted.

Further, resistors 38 and 39 are connected in series between the power supply and the ground, and the connection point between the resistors 38 and 39 is connected to the inverting input terminal of the preamplifier comparator 37 via a resistor 40. The output terminal of the comparator 37 is connected to the cathode of a diode 41, the anode of the diode 41 is connected to the non-inverting input terminal via a resistor 42, and the output terminal is further connected to a timer 25 which will be described later. ing.

The second comparison circuit 24 determines that the temperature of the air passing through the evaporator 6 is below a predetermined temperature, that is, the input voltage of the non-inverting input terminal is the reference value of the inverting input terminal.
Outputs an “L” signal when it falls below _E4 .

Timer 25 has resistors 43 and 44 between the power supply and ground.
are connected in series, and a connection point between the resistors 43 and 44 is connected to a non-inverting input terminal of a comparator 45. Further, a resistor 46 and a capacitor 47 are connected in series, and the other end of the resistor 46 is connected to the power supply, and the capacitor 4
The other end of 7 is connected to the output terminal of the comparator 37 of the second comparison circuit 24, and the resistor 4
One end of a resistor 48 and the cathode of a diode 49 are connected to the connection point between the capacitor 6 and the capacitor 47, respectively. Further, the other end of the resistor 48 is connected to the inverting input terminal of the comparator 45, and the anode of the diode 49 is connected to the other end of the capacitor 47. Further, the output terminal of the comparator 45 is connected to the cathode of a diode 50, and the anode of the diode 50 is connected via a resistor 51 to a variable thermo circuit 27, which will be described later.

When the output signal of the second comparison circuit 24 is "H", the timer 25 outputs "L" because this "H" signal is inputted to the inverting input terminal of the comparator 45 via the diode 49. A signal is output to connect the resistor 51 and the resistor 62 of the variable thermocircuit 27 in parallel. Then, the second comparison circuit 24
When the comparator 4 outputs an "L" signal, at the same time the comparator 4 outputs an "L" signal.
5 outputs an "H" signal only while the capacitor 47 is being charged via the resistor 46. Therefore, the resistor 51 is released from the parallel connection state with the resistor 62 of the variable thermocircuit 27 only during the charging period of the capacitor 47.

In the drive control circuit 26, the base of a transistor 52 is grounded via a resistor 53, and an output signal of the first comparison circuit 23 and an output signal of a variable thermocircuit 27, which will be described later, are applied to the base. Ru. Further, the emitter of the transistor 52 is grounded, the collector is connected to a power source via an excitation coil 54a of a relay 54, and a Zener diode 55 for protecting the transistor 52 is connected between the collector and the ground. One end of the normally open contact 54b of the relay 54 is connected to the power supply, and the other end is connected to the terminal to which the electromagnetic clutch 12 is connected.
connected to T ₁ respectively.

When the "L" signal is applied to the base of the transistor 52, the drive control circuit 26 opens the normally open contact 54b of the relay 54, puts the electromagnetic clutch 12 in a de-energized state, and operates the compressor 8. Stop.

In the variable thermo circuit 27, a resistor 56 provided on the input side receives an output signal from a general signal calculation circuit 28, which will be described later, via a comparator 57. The comparator 5
The cathode of a diode 58 is connected to the output terminal of 7, and the anode of the diode 58 is connected to an inverting input terminal, and is also connected to an inverting input terminal of a comparator 60 via a resistor 59. Also,
One ends of resistors 61 and 62 are connected to the anode, and the other ends of resistors 61 and 62 are connected to a power source or ground, respectively.

A resistor 63 is connected to the non-inverting input terminal of the comparator 60.
is connected, and the output signal of the air temperature sensor 18 is inputted via the resistor 63. A resistor 64 is connected between the output terminal and the non-inverting input terminal of the comparator 60, and a resistor 65 is connected to the output terminal, and the other end of this resistor 65 is connected to the drive control circuit 26. Connected to the base of transistor 52.

The resistor 62 is normally connected in parallel with the resistor 51 of the timer 25 due to the action of the timer 25, so the reference voltage _E3 is applied to the resistor 62.
When the input voltage of the comparator 57 is lower than Es ₁ by the action of the comparator 57, the voltage Es ₁ determined by the division ratio of the parallel resistor 51 and the resistor 61 is lowered. , its voltage change characteristics are as shown in FIG.

Then, when the temperature of the air passing through the evaporator 6 is below the temperature corresponding to the reference voltage Es, that is, when the input voltage of the non-inverting input terminal of the comparator 60 is below the reference voltage Es, the variable thermocircuit 27 An "L" signal is output to the output terminal of 60.

Further, the output signal of the variable thermo circuit 27 is transmitted to the electromagnetic clutch 12 via the drive control circuit 26.
Since the operation of the compressor 8 is turned on and off by turning on and off the compressor 8, the on-off characteristic of the compressor 8 becomes as shown by the characteristic line A in FIG. 4 based on the above-mentioned FIG. The difference in reference temperature Ts at which the compressor 8 is turned on and off is due to the hysteresis characteristic of the comparator 60.

The general signal calculation circuit 28 is connected to the vehicle interior temperature sensor 1.
9. Input the signals Tr, Ts, Ta, and Td from the solar radiation sensor 20, the outside air temperature sensor 21, and the temperature setting device 22, and calculate the total signal T using, for example, the following equation.

T = (Tr-25) + K ₁ (Ts-25) K ₂ (Ta-25) - K ₄ (Td-25) ...(1) However, K ₁ to _{K 4} are the gains of each sensor or setting device. be.

Then, a voltage signal corresponding to this total signal T is output. In this embodiment, the total signal T calculated by the above equation (1) and the output voltage of the total signal calculation circuit 25 are set to be inversely proportional.

The operation of the above configuration will be explained with reference to FIGS. 4 and 5. When the device is started, the temperature of the evaporator 6 is high, and therefore the temperature of the air passing through it is also high. 1 comparison circuit 23
In the second comparison circuit 24, when E ₂ < E ₃ , the output is "H", and in the second comparison circuit 24, when E ₁ > E ₄ , the output is "H", so the output of the timer 25 is "L", and the variable thermo circuit 27 When E ₁ >Es, the output becomes "H", and the drive control circuit 26 excites the electromagnetic clutch 12, so that the compressor 8 is activated.

As the compressor 8 operates, the temperature of the evaporator 6 gradually decreases, and the temperature of the air passing through the evaporator 6 also gradually decreases (region in FIG. 5).

When freezing or cooling is started, the entire evaporator 6 is not sufficiently cooled, so the compressor 8 continues to operate without being turned off by the action of the variable thermocircuit 27, and as a result, the temperature of the evaporator 6 decreases. It reaches near the freezing temperature (around 0°C) (D in Figure 5). In the figure, the difference in on-off temperature is due to the hysteresis characteristic of the comparator 32. In the vicinity of this freezing temperature, the first comparator circuit 23 outputs an "L" signal, so the compressor 8 is turned off, the temperature of the evaporator 6 rises, and when the temperature rises to a predetermined value, the compressor 8 is turned on again. Then, the entire evaporator 6 comes to be cooled while the compressor 8 is repeatedly turned on and off near the freezing temperature, and the temperature of the air passing through the evaporator 6 gradually decreases. When the temperature M ₁ corresponding to the reference voltage E ₄ of the second comparison circuit 24 becomes lower than that, that is, when E ₁ <E ₄ , the second comparison circuit 24 outputs an “L” signal. This "L" signal causes the timer 25 to release the parallel connection between the resistors 51 and 62 for a predetermined time _t1 , so the reference voltage Es of the variable thermocircuit 27 rises during this period, and the on/off control of the compressor 8 is controlled. This occurs along characteristic line B in FIG. As a result, the temperature of the evaporator 6 rises, and as the compressor 8 turns on and off, it begins to rise and fall near the temperature _M2 . Then, when the predetermined time _t1 has elapsed, the reference voltage Es returns to its normal value again, and the compressor 8 is activated, so the temperature of the evaporator 6 decreases, and when it reaches near the freezing temperature, the above-mentioned action resumes. As a result of this repetition, freezing of the evaporator 6 is prevented.

In this embodiment, the output of the timer 25 is connected to the variable thermo circuit 27 to change the reference voltage Es of the variable thermo circuit 27, but it may also be connected to the evaporator sensor 17. It is also possible to change the inputs of the timer 45 and connect the output of the timer 25 to the connection point between the resistors 29 and 30 of the first comparison circuit 23 to increase the on/off temperature.

(Effects of the invention) As described above, according to this invention, the temperature of the air passing through the evaporator is detected, and when the temperature of the air passing through the evaporator is higher than a predetermined temperature, the compressor is controlled to turn on and off near the freezing temperature. However, if the temperature of the air passing through the evaporator falls below a predetermined value, the on/off control temperature of the compressor is raised for a predetermined period of time, so the evaporator will not be kept near the freezing temperature for a long time, and as a result, the evaporator will not freeze. In addition, even if the evaporator freezes, the compressor will not be stopped for a relatively long period of time, resulting in no loss of freezing or cooling efficiency.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the control circuit used in the antifreeze device according to the present invention, Fig. 2 is a schematic diagram showing the antifreeze device described above, and Fig. 3 is a reference voltage Es in the control circuit described above. FIG. 4 is a characteristic diagram showing the on/off characteristics of the compressor in the same control circuit as above;
Fig. 5 is a characteristic diagram showing the temperature change of the evaporator and the temperature change of the air passing through the evaporator in the same anti-freezing device as above, Fig. 6 is a circuit diagram showing a conventional example, and Fig. 7 is an evaporator in the conventional example same as above. FIG. 2 is a characteristic diagram showing temperature changes in the vehicle and temperature changes in the vehicle interior. 17... Evaporator sensor, 18... Air temperature sensor, 23... First comparison circuit, 24... Second
Comparison circuit, 25...Timer, 26...Drive control circuit, 27...Variable thermo circuit, 28...Comprehensive signal calculation circuit.

Claims (1)

[Claims for Utility Model Registration] An evaporator sensor that detects the temperature of the evaporator, an air temperature sensor that detects the temperature of the air that has passed through the evaporator, and a second comparing means that compares the output of the air temperature sensor with a predetermined value. As a result of the second comparison means, if the output of the air temperature sensor is equal to or higher than a predetermined value, a first set value near the freezing temperature is output, and if the output of the air temperature sensor is equal to or lower than the predetermined value, a thermo reference voltage setting means for outputting a second set value higher than the first set value, and a second set value when the second set value is set by the thermo reference voltage setting means. a timer that continues to output the value for a predetermined period of time; a first comparison unit that compares the output of the evaporator sensor with a first or second set value set by the thermo reference voltage setting unit; 1. A freeze prevention device comprising: drive control means for controlling on/off of a compressor based on the output from the comparison means.