JPS5824285B2 - Car cooler control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a car cooler control device that controls the temperature inside a car by controlling on/off of a refrigerant compressor.

In a general car cooler control device, a temperature detection element such as a thermistor is installed on the cold air outlet side of the refrigerant evaporator, and when the air temperature on the outlet side of the evaporator drops to a predetermined value, the refrigerant compressor is stopped. When the air temperature on the outlet side rises and reaches a predetermined value that is sufficiently higher than the predetermined value, the refrigerant compressor is driven again to control the temperature inside the car, and a temperature detection element is also installed inside the car to control the temperature inside the car. There are some that allow similar control.

However, in the above-mentioned device, when the temperature outside the vehicle is high in midsummer, the temperature inside the vehicle is difficult to drop, so control is essentially performed based on the air temperature on the outlet side of the evaporator.

If you set the air temperature on the outlet side to turn off the refrigerant compressor to a low value, the operating rate of the refrigerant compressor will also increase, and if this continues for a long time, the surface temperature of the evaporator will be below 0°C, so the air temperature will reach the surface of the evaporator. Frost begins to form.

This frost formation not only obstructs heat exchange in the evaporator and prevents the temperature of the air on the outlet side from decreasing, but also destabilizes the amount of air blown out and disrupts the output of the temperature detection element installed on the outlet side of the evaporator. In order to stabilize the temperature inside the car, the temperature control becomes unstable.

Therefore, in order to ensure reliable on/off control of the refrigerant compressor, it is necessary to set the outlet air temperature slightly higher when the refrigerant compressor is turned off. The disadvantage was that the cooling effect could not be fully utilized and the cooling effect would be poor.

The present invention aims to eliminate such drawbacks, and aims to provide a car cooler control device that has a function of preventing frost formation on the evaporator and can fully demonstrate its cooling capacity. .

The present invention is a car cooler control device that is equipped with a circuit that stops a refrigerant compressor when the air temperature of the evaporator or its outlet side remains below a predetermined temperature for a predetermined period of time. It can also be combined with a circuit for off control.

The present invention will be described below with reference to drawings showing embodiments.

FIG. 1 shows a first embodiment of the present invention up to the part of the electromagnetic clutch that drives the refrigerant compressor.

Th1 is a thermistor as a temperature detection element installed on the outlet side of the evaporator (not shown) (may be between the fins of the evaporator), and OPl is the detection output of thermistor Th1, and the outlet side air temperature is set to T1 (e.g. OF2 is a comparator amplifier that outputs a low level when O20 becomes a low level output, and has a relatively larger hysteresis than resistor R8. , a comparator amplifier that outputs a high level when Th1 reaches a relatively high set value T2 (for example, 10°C); OF2 is connected to the comparator amplifier OP1 via a delay circuit consisting of a resistor R7 and a capacitor C; The comparator amplifier whose output becomes low level after a predetermined time 11 (for example, 10 minutes) determined by the discharge time constant of the delay circuit after the output of OP1 becomes low level, A is an AND gate and comparator amplifier OP2. OP3
Only when both outputs are at a high level, the transistor Q is made conductive to operate the relay RL, thereby energizing the electromagnetic clutch MC for driving the refrigerant compressor 1.

R6 is a resistor for providing hysteretic characteristics to the comparator amplifier OP1, and provides a slight temperature difference between starting and canceling the timer operation.

Note that the output of the comparator amplifier OP2 becomes a low level after the comparator amplifier OP3 completes the timer operation for the predetermined time t1. Therefore, the output of the comparator amplifier OP2 is reversed when the temperature rises to the predetermined value T2 after the refrigerant compressor is stopped. However, this temperature T2 is set so that if there is frost on the evaporator, enough time can be obtained to remove it by continuing air blowing without refrigerant supply. is resistance R8
The value can be adjusted arbitrarily.

Dl is a diode for resetting the operation of the delay circuit formed by the resistor R7 and the capacitor C, and when the air temperature on the outlet side becomes below T□, the output of the comparator amplifier OP1 becomes a low level, so that the capacitor C is discharged. If the outlet air temperature becomes slightly higher than T1 within the predetermined time 11 after starting, the capacitor C is instantly charged through the diode D1 to stop the delay operation.

Further, D2 is a diode that uses the low level output of the comparator amplifier OP3 to make the output of the comparator amplifier OP2 a low level, and when a predetermined time t1 has elapsed after the air temperature on the outlet side becomes below T0, the comparison is made via the diode D2. Amplifier OP2
The output of the refrigerant compressor is set to a low level, and the temperature of the air on the outlet side is set to T2 when the refrigerant compressor is re-driven, so that sufficient time necessary for defrosting can be obtained.

Next, the circuit operation will be explained with reference to FIG. 2, which shows the hourly characteristics of the air temperature on the outlet side of the evaporator.

In the region a in FIG. 2, the air temperature on the outlet side has not decreased to the set temperature T□, and in this state, the comparator amplifier OP1. Both outputs of OP2 are at a high level, and energization of electromagnetic clutch MC is maintained.

Such periodic temperature changes occur when the cooling time is short and not much frost has formed on the evaporator, and in such a state, the time during which the air temperature on the outlet side becomes equal to or lower than T1 is the predetermined time t1. The time is sufficiently shorter than the predetermined time t1.

However, if the evaporator continues to operate for a long time with a large heat load, the situation will be in the region shown in the figure.

Comparison amplifier OP1 compares the voltage divided by resistor R3 and resistor R4 with the voltage divided by resistor R5 and thermistor Th1, and determines whether the outlet air temperature is T.
, the voltage at the inverting terminal becomes equal to the voltage at the non-inverting terminal, and the output becomes low level.

On the other hand, comparator amplifier OP3 compares the voltage divided by resistor R9 and resistor R1° with the terminal voltage of capacitor C, and at the same time as the output of comparator amplifier OP1 becomes low level, capacitor C starts discharging. When the inverting terminal voltage drops exponentially and becomes equal to the inverting terminal voltage, that is, after a predetermined time t, the output becomes a low level.

As a result, the power to the electromagnetic clutch MC is cut off and the refrigerant compressor is stopped. However, as mentioned above, at this time, the output of the comparator amplifier OP2 is also reduced to a low level due to the diode D2, so the refrigerant compressor changes the temperature of the air on the outlet side. The stoppage continues until the temperature rises to T2, and during this time the frost on the evaporator surface is removed.

Note that a predetermined period of time 11 has passed since the air temperature on the outlet side decreased to T1.
If the temperature becomes slightly higher than T1 again within the same period, the output of the comparator amplifier OP becomes high level, and as mentioned above, the capacitor C is charged by the diode D1, returning to the state before the start of discharging, and the air temperature on the blowing side becomes T1 again. It starts operating when the temperature drops to .

As described above, the present invention not only controls the interior temperature of the vehicle by detecting the evaporator or outlet side air temperature and controlling the refrigerant compressor on and off, but also detects when frost is starting to accumulate on the evaporator. Frost formation can be kept to a minimum by detecting the phenomenon of stagnation in the air temperature on the outlet side and stopping the refrigerant compressor for a sufficient period of time required for defrosting.

This makes it possible to control the interior temperature of the vehicle at a lower temperature than before without setting a lower limit for the air temperature on the outlet side, and to make full use of the refrigerant compressor's capacity, ensuring sufficient cooling return even in the middle of summer. The effect can be obtained and the interior of the car can be cooled comfortably at all times.

FIG. 3 is a circuit diagram showing another embodiment of the present invention. In this embodiment, in addition to the thermistor Th1 disposed on the outlet side of the evaporator, a thermistor Th2 as a temperature detection element is disposed inside the vehicle. The output can be used to control the temperature inside the vehicle.

O20 is the temperature T3 where the temperature inside the car is set by the driver.
This is a comparator amplifier whose output becomes a low level when the temperature drops to
8°C).

That is, the comparison amplifier OP4 compares the voltage divided by the resistor R15 and the resistor R16 that constitute the bridge circuit with the voltage divided by the resistor R14, the variable resistor VR, and thermistor Th2, and determines the temperature inside the vehicle. T
When the voltage decreases to 5 and the inverting terminal voltage and non-inverting terminal voltage become equal, the output becomes a low level and energization to the electromagnetic clutch MC is cut off.

Such control based on the vehicle interior temperature is performed when the heat load on the evaporator O is relatively small, and since the operating rate of the refrigerant compressor does not increase, there is almost no frost on the evaporator.

Control based on the air temperature on the outlet side is the same as in the embodiment described above, and temperature control is performed so that frost does not accumulate on the evaporator.

As is clear from this, in this embodiment, frost formation prevention control is performed based on the air temperature on the outlet side of the evaporator and the inside of the vehicle is controlled.

Since the interior temperature of the vehicle is controlled by temperature, it is possible to prevent the accumulation of frost on the evaporator as well as to provide comfortable cooling of the interior of the vehicle at an arbitrary set temperature, as in the previous embodiment.

Figure 4 is a circuit diagram of an embodiment that enables frost prevention control and vehicle interior temperature control only by detecting the temperature of the air on the evaporator or outlet side. The temperature inside the car can be changed using a variable resistor VR, and one AND gate shown in the embodiment shown in Fig. 1 is added to control frost formation and the temperature inside the car. By varying the set value of the evaporator or its outlet air temperature within a certain range, the refrigerant compressor can be turned on and off to control the interior temperature around the temperature set by the variable resistor VR. can.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram showing a first embodiment of the present invention, and FIG.
The figure is a characteristic diagram showing temporal changes in the air temperature on the outlet side of the evaporator and the temperature inside the vehicle due to this control circuit, and FIGS. 3 and 4 are control circuit diagrams showing the second and third embodiments of the present invention, respectively. It is. Th1. Th2...Thermistor, OPl, OF2. O
20゜O20... Comparison amplifier, RL... Relay, M
C...Electromagnetic clutch, A...And gate.

Claims (1)

[Claims] 1. In a car cooler control device that controls the temperature inside a car by on/off control of a refrigerant compressor, the air temperature of the evaporator or its outlet side is detected, and when the detected temperature is below a set value and a predetermined period of time has elapsed, the refrigerant compression is started. A car cooler control device characterized by being equipped with a circuit for stopping the machine.