KR19980049376A - Thermostats for automotive air conditioners - Google Patents

Abstract

The present invention relates to a thermostat for an automotive air conditioner, and more particularly, to an air conditioner for an automobile which circulates a refrigerant by rotating operation of a compressor and generates cool air through an evaporator, And the switching unit selectively outputs a DC voltage of a predetermined level applied from the power input unit to the compressor driving unit in accordance with the switching control signal, and outputs the switching control signal corresponding to the temperature of the evaporator The controller controls the compressor whose rotational operation is controlled in accordance with the operation of the compressor driving unit to maintain the room temperature of the automobile within a predetermined range to prevent freezing of the evaporator and to operate the off- On the other hand, in the measurement amplifier for measurement amplification of the temperature sensing unit By adjusting the hysteresis interval for the on / off operation of the compressor by varying the feedback resistance value, it is possible to adjust the hysteresis interval for on / off operation of the compressor without noise during operation, Can be varied.

Description

Thermostats for automotive air conditioners

1 is a schematic configuration diagram of a general automotive air conditioner,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an automatic air conditioner,

FIG. 3 is a diagram illustrating an operation state of a conventional automatic air conditioner according to an embodiment of the present invention,

FIG. 4 is a block diagram of a thermostat of an automotive air conditioner according to the present invention. FIG.

Fig. 5 is a circuit diagram of the present invention shown in Fig. 4,

FIG. 6 is a circuit diagram showing an embodiment of the temperature sensing unit shown in FIG. 4,

FIG. 7 is a circuit diagram showing two embodiments of the temperature sensing unit shown in FIG. 4,

FIG. 8 is a circuit diagram showing three embodiments of the temperature sensing unit shown in FIG. 4,

Fig. 9 is a circuit diagram showing an embodiment of the switching unit shown in Fig. 4,

Description of the Related Art [0002]

10: compressor 20: condenser

30: fan 40: receiver tank

50: dryer 60: expansion valve

70: evaporator 80: blower

90: sensing tube 100: capillary tube

110: thermostat 130: power input unit

140: temperature sensing unit 150: switching unit

160: compressor driving unit 170:

[Object of the invention]

[TECHNICAL FIELD OF THE INVENTION AND RELATED ART OF THE SAME]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for an automobile, and more particularly, to a thermostat for an automotive air conditioner suitable for turning on / off a compressor by an electronic switching means according to a temperature of an evaporator or a room .

As shown in Fig. 1, a general automotive air conditioner cools the interior of a vehicle by circulation of refrigerant and air.

That is, the high-temperature and high-pressure refrigerant gas discharged from the compressor 10 is forcedly cooled by the fan 30 or the like in the condenser 20 to be liquefied, and the liquefied refrigerant passes through the receiver tank 40, And is introduced into the expansion valve 60 after the foreign substance is removed.

The high pressure refrigerant liquid flowing into the expansion valve 60 is converted into a low pressure mist state refrigerant by the effect of the thermal expansion of the expansion valve 60 and flows into the evaporator 70, The refrigerant in the fog state is converted into refrigerant gas while exchanging heat with ambient air flowing by the blower 80. The heat exchanged refrigerant gas is converted into a high temperature and high pressure refrigerant gas in the compressor 10, Repeat the same cycle as.

At this time, the degree of opening / closing of the expansion valve 60 is increased or decreased by controlling the temperature of the vehicle interior or the temperature of the evaporator 20 by the sensing tube 90 and controlling the expansion valve 60 through the capillary tube 100 . The indoor air of the automobile in which the flow force is increased by the blower 80 is cooled while passing through the evaporator 70, and circulates through the inside of the automobile.

Since the refrigerant circulation amount fluctuates according to the state of the refrigerating cycle, the receiver tank 40 is disposed between the condenser 20 and the dryer 50 so that the refrigerating cycle smoothly operates in response to the fluctuation of the circulation amount. .

In addition, the liquid refrigerant passing through the condenser 20 according to the operation of the compressor 10 may have refrigerant gas in a bubble state, and the refrigerant may contain moisture and foreign matter, When the liquid refrigerant containing the foreign matter enters the expansion valve 60, the expansion effect is deteriorated, so that the cooling performance is remarkably deteriorated.

Therefore, the receiver tank 40 and the expansion valve 60 are provided to separate bubbles contained in the liquid refrigerant that has passed through the receiver tank 40 from the liquid refrigerant, and to remove moisture and foreign substances contained in the liquid refrigerant. And the driver 50 is disposed between them.

The expansion valve (60) is a mechanical expansion valve having a diaphragm and a spring.

On the other hand, by turning on / off the compressor 10 by the automatic thermostat, the indoor temperature of the automobile is kept constant and freezing of the evaporator is prevented.

FIG. 2 is a perspective view illustrating a connection structure of a conventional automatic thermostat for an automotive air conditioner. Referring to FIG. 2, the thermostat 110 detects the temperature of the evaporator 70, And a signal generator 113 for generating a signal according to the temperature sensed by the sensor unit 111. The signal generator 113 generates a signal corresponding to the sensed temperature of the sensor unit 111, .

The electric signal 117 is connected to the signal generator 113 of the thermostat 110 so as to turn on and off the magnetic switch by activating the relay by the signal of the signal generator 113.

Here, the magnetic switch is connected to a crankshaft of the engine by a belt so that the compressor 10 can be rotated.

3, the sensor unit 111 includes a capillary tube 114 in which a refrigerant gas is sealed, a bellows 116 disposed in the body 115 of the signal generation unit 113, As shown in Fig.

The signal generating unit 113 is hermetically disposed on the upper side of the bellows 116 so that the movable contact c is brought into contact with the fixed contacts a and b connected to the electric wire 117, (c) has a structure in which a spring member 119 connected to the adjusting screw 118 is arranged to adjust the expansion force of the alcohol enclosed in the bellows 116. As shown in Fig.

Meanwhile, when the temperature of the evaporator 70 drops below a certain temperature during the heat exchange in the evaporator 70, the evaporator 70 is cooled by the condensed water that is frozen on the surface of the evaporator 70, . Accordingly, the above-mentioned property blocks the passage of the air, thereby lowering the freezing performance. Therefore, the operation of the air conditioner is stopped or the defrosting operation is performed.

3, when the surface temperature of the evaporator 70 falls below a predetermined value, the capillary 114 of the sensor portion 111 is shrunk due to shrinkage of the alcohol contained therein, 116 is lowered, and the movable contact c is separated from the fixed contacts a, b.

Therefore, the relay RL is disconnected by the cutoff of the power supplied to the relay RL, thereby shutting off the power supplied to the magnetic clutch MG, thereby turning off the magnetic clutch MG.

When the magnetic clutch MG is turned off, the magnetic clutch MG is disconnected from the internal pulley (not shown) to disconnect the electromagnet, Negative) is separated from the shaft (not shown) of the compressor 10.

Therefore, the compressor 10 is stopped and the operation of the automotive air conditioner is stopped.

On the other hand, when the surface temperature of the evaporator 70 rises to a predetermined value or more, the internal pressure of the bellows 116 rises due to the expansion of the alcohol sealed in the capillary tube 114 of the sensor unit 111, The movable contact c is brought into contact with the fixed contacts a and b.

Accordingly, power is supplied to the relay RL, and the relay RL is energized by the power supply to supply power to the magnetic clutch MG, thereby turning on the magnetic clutch MG.

When the magnetic clutch MG is turned on, the magnetic clutch MG is energized by a current passing through an internal pulley (not shown) to excite the electromagnet, Is brought into contact with the shaft (not shown) of the compressor 10.

Therefore, the compressor 10 is driven to operate the automotive air conditioner.

As described above, the defrosting operation of the automotive air conditioner is performed due to the repetition of the on / off of the compressor 10 by the automatic thermostat 110, so that the surface of the evaporator 70 is stuck On the other hand, it is possible to keep the air in the automobile room within a certain temperature range.

However, since the thermostat 110 has a mechanical structure as described above, when the movable contact c comes in contact with or falls off the fixed contacts a and b, And noise caused by the operation noise disperses the driver's nerves, which is disadvantageous in terms of a pleasant driving environment.

On the other hand, in order to readjust the preset off-point of the compressor 10, it is necessary to turn the adjustment screw 118 again to set the off-point of the compressor 10, which is precise There is a problem that it is very difficult for the driver or the maintenance person of the front line to rotate the adjustment screw 118 to readjust the off-point of the compressor 10 and to deteriorate precision.

On the other hand, according to the automatic thermostat 110, only the off-point of the compressor 10 can be adjusted, and the interval of the hysteresis for the on / off operation of the compressor 10 can not be adjusted.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a compressor which is free from noise during operation, The present invention has been made in view of the above problems, and it is an object of the present invention to provide an automatic thermostat for an automotive air conditioner.

According to an aspect of the present invention for achieving the above object, there is provided an automotive air conditioner for circulating a refrigerant by a rotation operation of a compressor and generating cool air through an evaporator, the automotive air conditioner comprising: a power input unit for outputting a predetermined driving power; A compressor driving unit selectively driving the compressor by selectively transmitting a driving force generated from an engine of the vehicle to the compressor according to an input of a driving power source; a temperature sensor for sensing the temperature of the evaporator and outputting a corresponding switching control signal And a switching unit for selectively applying the driving power to the compressor driving unit on the basis of a switching control signal input from the temperature sensing unit. Is provided.

[Structure and operation of the invention]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of a thermostat for an automotive air conditioner according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 4 is a block diagram of a thermostat of an automotive air conditioner according to the present invention. Referring to FIG. 4, a DC voltage of a predetermined refresh applied from the power input unit 130 is input to the temperature sensing unit 140 and the switching unit 150, The temperature sensing unit 140 senses the temperature of the evaporator 70 and inputs a corresponding switching control signal to the switching unit 150. The switching unit 150 switches the temperature sensing unit 140, And supplies a DC voltage of a predetermined level, which is applied from the power input unit 130, to the compressor driver 160 by performing a switching operation based on the switching control signal input from the power supply unit 140.

When a DC voltage of a predetermined level applied from the power input unit 130 is supplied to the compressor driving unit 160, the compressor driving unit 160 transmits the driving force of the engine (not shown) to the compressor , Thereby driving the compressor (see 10 in Fig. 1).

The temperature sensing unit 140 senses a DC voltage of a predetermined level applied from the power input unit 130 to the compressor driving unit 160 when the temperature of the evaporator (see 70 in FIG. 1) The off-point adjusting unit 170 adjusts the reference temperature so as to adjust the temperature of the compressor 10 according to the temperature of the evaporator (refer to 70 in FIG. 1) (See FIG.

5 is a circuit diagram of the present invention shown in FIG. 4, in which a DC voltage of a predetermined level provided by a battery BT of a power input unit 130 is bypassed through a bypass diode D, The voltage is smoothed by the capacitor C1 which is grounded on one side and then applied to the temperature sensing unit 140. [

The Zener diode ZD is turned on when the DC voltage of the predetermined level output from the battery BT is higher than a certain level and passes the DC voltage to the ground, Thereby preventing an overvoltage accident applied to the unit 140.

The voltage V1 applied from the power input unit 130 to the temperature sensing unit 140 is divided by the resistor R2 and the resistor R3 and connected to an operational amplifier OP1 Inverting terminal (+) of the operational amplifying circuit OP1 while being divided by the resistor R4 and the thermistor RTh and applied to the inverting terminal (-) of the operational amplifier OP1 for measurement amplification.

Here, the non-inverting terminal (+) of the operational amplifier OP1 for measurement and amplification and the output terminal of the operational amplification operational amplifier OP1 are connected by a feedback resistor R5.

The inverting terminal (-) of the comparison operational amplifier OP2 in the temperature sensing unit 140 is connected to the inverting terminal (-) of the operational amplifier OP1 for measurement amplification, (V3) which is the same as the inverting terminal (-) of the operational amplifier OP1.

The high-level or low-level signal output from the output terminal of the comparison operational amplifier OP2 drops in voltage at the resistor R6 and is supplied to the base end of the control transistor Q1 provided in the switching unit 150 .

Therefore, when a high-level signal of the comparative operational amplifier OP2 whose voltage is lowered in the resistor R6 is provided at the base end of the control transistor Q1, the control transistor Q1 is turned on to turn on the switching transistor The switching transistor Q2 is turned on and the DC voltage of the predetermined level applied from the power input unit 130 to the emitter terminal of the switching transistor Q2 is reduced to a low level, And supplies it to the compressor driving unit 160.

On the other hand, the resistor R8 of the predetermined value of the off-point adjusting unit 170 is connected in parallel to the resistor R3 of the temperature sensing unit 140. When the switch S is turned on, the resistor R3 and the resistor R8 ) ≪ / RTI > .

Therefore, when the switch S of the off-point adjusting unit 170 is turned on, the non-inverting terminal (+) of the operational amplifier OP1 for measurement amplification of the temperature sensing unit 140 receives the temperature sensing The voltage V1 applied to the unit 140 is lower than the voltage applied to the resistor R2, A low pressure which is divided by the pressure is provided.

Hereinafter, an operation example of the present invention having the above-described configuration will be described in detail with reference to FIGS. 4 and 5. FIG.

The direct current voltage of the predetermined level outputted from the battery BT of the power input unit 130 in the state that the main switch MS of the air conditioner is turned on is detected by the resistor R1 through the bypass diode D, And is smoothed by the capacitor C1 whose one side is grounded, and is applied to the temperature sensing unit 140. [

The voltage V1 applied to the temperature sensing unit 140 in the power input unit 130 is divided by the resistor R2 and the resistor R3 and input to the non-inverting terminal (+) of the operational amplifier OP1 for measurement amplification While being divided by the resistor R4 and the thermistor RTh and input to the inverting terminal (-) of the operational amplifier OP1 for measurement and the inverting terminal (-) of the operational amplifier OP2 for comparison.

At this time, on the output terminal of the operational amplifier OP1 for measurement amplification, a voltage V2 input to the non-inverting terminal (+) of the operational amplifier OP1 for measurement and amplification, An output voltage V0 of an exact multiple of the level difference of the voltage V3 input to the inverting terminal (-) is generated, and the output voltage V0 thereof can be calculated by the following equation (1).

[Equation 1]

The output voltage V0 of the operational amplifier OP1 for measurement amplification is applied to the non-inverting terminal (+) of the operational amplifier OP2 for comparison.

Therefore, the comparison operational amplifier OP2 compares the level of the output voltage V0 of the operational amplifier OP1 for measurement and the voltage V3 of the inverted terminal (-) of the comparison operational amplifier OP2 And when the level of the output voltage V0 of the operational amplifier OP1 for measurement amplification is larger than the level of the voltage V3 provided to the inverting terminal (-) of the comparative operational amplifier OP2 , And outputs a signal of a high level, and outputs a signal of a low level when the signal is low.

The voltage V3 provided to the inverting terminal OP2 of the comparative operational amplifier OP2 is supplied from the power input unit 130 to the voltage V1 applied to the temperature sensing unit 140 through the resistor R4 and the thermistor The voltage V3 provided to the inverting terminal (-) of the comparative operational amplifier OP2 is lower than the voltage V3 of the thermistor RTh which varies according to the temperature of the evaporator (see 70 in FIG. 1) The voltage level is varied by the resistance value, and the relationship is expressed by the following equation (2).

[Equation 2]

For example, when the temperature of the evaporator (see 70 in FIG. 1) detected by the thermistor RHh is equal to or higher than a predetermined reference temperature, the resistance value of the thermistor RTh becomes relatively small, When the level of the voltage V3 input to the inverting terminal (-) of the thermistor RT2 becomes lower and the temperature of the evaporator (see 70 in FIG. 1) is lower than the predetermined reference temperature, the resistance of the thermistor RTh The level of the voltage V3 input to the inverting terminal (-) of the comparative operational amplifier OP2 becomes higher (see Equation 2).

On the other hand, the output voltage V0 of the operational amplifier OP1 for measurement amplification is proportional to the resistance value of the thermistor RTh, as can be seen from Equation (1).

Accordingly, when the temperature of the evaporator (see 70 in FIG. 1) sensed by the thermistor RTh is equal to or higher than a predetermined reference temperature, a comparatively low level voltage V3 corresponding thereto is inputted to the comparative operational amplifier OP2. The level of the output voltage V0 of the operational amplifier OP1 for measurement amplification is also lowered.

At this time, the voltage V3 input to the inverting terminal (-) of the comparative operational amplifier OP2 is input to the non-inverting terminal (+) of the comparative operational amplifier OP2, ), The comparison operational amplifier OP2 outputs a signal of a high level.

The high-level signal output from the comparative operational amplifier OP2 is reduced in voltage by the resistor R6 and input to the base end of the control transistor Q1.

The control transistor Q1 receiving the high level signal at the base end is turned on and the control transistor Q1 is turned on so that the potential at the base end of the switching transistor Q2 is switched to the switching transistor Q2, The potential of the collector of the transistor Q2 becomes lower than the potential of the collector of the transistor Q2, and the switching transistor Q2 is turned on.

The switching transistor Q2 is turned on so that a DC voltage of a predetermined level applied from the power input unit 130 to the switching unit 150 is supplied to the relay RL through the main switch MS of the compressor driving unit 160 . Here, the main switch MS is in an ON state as described above.

When the DC voltage applied from the power input unit 130 through the switching unit 150 is input to the relay RL, a current flows through the internal electromagnet and the relay RL performs a switching 'on' operation And applies the DC voltage applied from the power input unit 130 through the switching unit 150 to the magnetic clutch MG.

The DC voltage applied through the switching unit 150 is input from the power input unit 130, thereby turning on the magnetic clutch MG.

When the magnetic clutch MG is turned on, the magnetic clutch MG is energized by a current flowing through an internal pulley (not shown) to excite the electromagnet, Is contacted with an axis (not shown) of the compressor (see 10 in Fig. 1).

As a result, the compressor (see 10 in Fig. 1) starts driving, and the refrigerant circulates, and the interior of the automobile is cooled by the cooling of the evaporator (see 70 in Fig. 1).

Thereafter, when the temperature of the evaporator (see 70 in FIG. 1) sensed by the thermistor RTh is lower than the predetermined reference temperature '', a comparatively high level voltage V3 corresponding to the temperature of the evaporator Is input to the inverting terminal (-), and the level of the output voltage V0 of the operational amplifier OP1 for measurement amplification also increases.

At this time, the voltage V3 input to the inverting terminal (-) of the comparative operational amplifier OP2 is input to the non-inverting terminal (+) of the comparative operational amplifier OP2, , The comparison operational amplifier OP2 outputs a signal of a low level.

The low-level signal output from the comparative operational amplifier OP2 is lowered in voltage by the resistor R6 and provided to the base end of the control transistor Q1.

The control transistor Q1 receiving the low level signal at the base end is turned off and the control transistor Q1 is turned off so that the potential at the base end of the switching transistor Q2 is applied to the switching transistor Q2, The potential of the collector of the transistor Q2 becomes higher than the potential of the collector of the transistor Q2 and the switching transistor Q2 is turned off.

The switching transistor Q2 is turned off so that the DC voltage of the predetermined level input from the power input unit 130 to the relay RL of the compressor driving unit 160 through the switching unit 150 is cut off.

The relay RL performs a switching 'off' operation by switching off the DC voltage input to the relay RL to cut off the current to the electromagnet inside the relay RL. The relay RL switches the power from the power input unit 130 to the switching unit 150, The DC voltage inputted to the magnetic clutch MG is cut off.

The direct current voltage input through the switching unit 150 from the power input unit 130 is cut off, thereby turning off the magnetic clutch MG.

When the magnetic clutch MG is turned off, the magnetic clutch MG is disconnected from the internal pulley (not shown) to disconnect the electromagnets. Accordingly, the rotor pulley Not shown) is separated from the shaft of the compressor (see 10 in Fig. 1).

Thereby, the compressor (see 10 in Fig. 1) stops driving, the refrigerant stops circulating motion, and the operation of the automotive air conditioner is stopped by stopping the cooling operation of the amplifier (see 70 in Fig. 1) do.

As can be seen from the above-mentioned equation (1), the feedback resistance R5 (R5) connecting the output terminal of the operational amplifier OP1 for measurement amplification and the non-inverting terminal (+ The output voltage V0 of the operational amplifier OP1 for measurement amplification can be adjusted.

When the output voltage V0 of the operational amplifier OP1 for measurement amplification is adjusted, the level of the voltage V3 input to the inverting terminal (-) of the comparative operational amplifier OP2 is the same, The level of the voltage V0 input to the non-inverting terminal (+) of the amplifier OP2 is varied to adjust the hysteresis interval for the on / off operation of the compressor (see 10 in FIG. 1) It will be easy to see that it can.

When the temperature of the evaporator (see 70 in FIG. 1) detected through the temperature sensing unit 140 is 0 ° C, the switching unit 150 switches the power from the power input unit 130 through the switching unit 150, The rotation of the compressor (see 10 in Fig. 1) is stopped by turning off the magnetic clutch MG by interrupting the DC voltage of the predetermined level input to the relay RL of the driving unit 160, 1) is rotated by increasing the resistance value of the feedback resistor R5, the temperature of the evaporator (see 70 in FIG. 1) is increased by increasing the resistance of the feedback resistor R5, It is possible to stop the rotation of the compressor (see 10 in Fig. 1) when the temperature is 1 캜 and rotate the compressor (see 10 in Fig. 1) when the temperature of the evaporator (see 70 in Fig. 1) will be.

That is, the hysteresis temperature interval of the evaporator (refer to 70 in Fig. 1) in which the compressor (see 10 in Fig. 1) is turned on and off is set to be 2 deg. C interval (1 deg. C to 3 deg. .

On the other hand, when the switch S of the off-point adjusting unit 160 is turned on, the non-inverting terminal (+) of the operational amplifier OP1 for measurement amplification of the temperature sensing unit 140 is connected to the non- The output voltage V0 of the operational amplifier OP1 for measurement amplification is varied to the voltage level according to the following expression (3) at the voltage level according to Equation (1).

[Equation 3]

Since the off-point of the compressor (see 10 in Fig. 1) with respect to the temperature of the evaporator (see 70 in Fig. 1) is a temperature point which varies in accordance with the output voltage V0 of the operational amplifier OP1 for measurement amplification, The off-point of the compressor (see 10 in Fig. 1) varies depending on the on / off operation of the switch S.

For example, if the temperature of the evaporator (see 70 in FIG. 1) sensed through the temperature sensing unit 140 is 0 ° C in the state where the switch S is off, the switching unit 150 receives the power from the power input unit 130, Off of the DC voltage of the predetermined level inputted to the relay RL of the compressor driving unit 160 by turning off the magnetic clutch MG to stop the rotation of the compressor (see 10 in Fig. 1) (See 10 in Fig. 1) based on the above-described procedure when the temperature of the switch S is on, and when the temperature of the output terminal of the operational amplifier OP1 When the temperature of the evaporator (see FIG. 1) is 12 ° C due to the fluctuation of the voltage V 0, the rotation of the compressor (see 10 in FIG. 1) is stopped and the temperature of the evaporator Lt; 0 > C, the compressor (see 10 in Fig. 1) can be rotated.

That is, the off-point of the compressor (see 10 in Fig. 1) relative to the temperature of the evaporator (see 70 in Fig. 1) can be varied from 0 캜 to 12 캜.

The capacitor C2 of the temperature sensing unit 140 is connected to the voltage V1 provided by the power supply input unit 130 and is connected to the output terminal of the operational amplification amplifier for measurement amplification The same voltage is supplied to the non-inverting terminal (+) and the inverting terminal (-) of the operational amplifier OP1 so that the output voltage V0 of the operational amplifier OP1 for measurement amplification is not generated, And has a function of preventing malfunction.

4 is a circuit diagram showing one embodiment of the temperature sensing unit. The voltage V1 of a predetermined level applied from the power supply input unit 130 is connected to a resistor R2 and an evaporator 70 And is inputted to the inverting terminal (-) of the operational amplifier OP1 for measurement and amplification and the inverting terminal (-) of the operational amplifier OP2 for comparison, while being divided by the resistor (RTh) Divided by the variable resistor R2 and the variable resistor VR1 and input to the non-inverting terminal (+) of the operational amplifier OP1 for measurement amplification.

On the other hand, the output terminal of the non-inverting terminal (+) of the operational amplifier OP1 for measurement amplification and the operational amplifier OP1 for measurement amplification is connected by the feedback resistor R5 and the variable resistor VR2.

In this case, the output voltage V0 of the operational amplification amplifier OP1 is calculated by the following equation (4). As can be seen from the operation example of the present invention described above, the resistance value of the variable resistor VR1 The output voltage V0 of the operational amplifier OP1 for measurement amplification is adjusted so that the off-point of the compressor (see 10 in Fig. 1) is adjusted by adjusting the variable resistor VR1.

For reference, the off-point of the compressor (see 10 in Fig. 1) corresponds to the output voltage V0 of the operational amplifier OP1 for measurement amplification (see the above-described operation example of the present invention).

[Equation 4]

On the other hand, when the resistance value of the variable resistor VR2 is varied, the hysteresis interval for the on / off operation of the compressor (see 10 in FIG. 1) is adjusted as will be seen from the operation example of the present invention described above.

7 is a circuit diagram showing the second embodiment of the temperature sensing unit shown in FIG. 4. The voltage V1 of a predetermined level applied by the power input unit 130 is connected to the resistor R2 and the evaporator 70) and is inputted to the inverting terminal (-) of the operational amplifier OP1 for measurement and the inverting terminal (-) of the operational amplifier OP2 for comparison, while being divided by the thermistor RTh, Is divided by the resistor R2 and the thermistor RTh which detects the room temperature of the automobile and is provided to the non-inverting terminal (+) of the operational amplifier OP1 for measurement and amplification.

Here, since the output voltage V0 of the operational amplifier OP1 for measurement amplification is calculated by the following equation (5), as can be seen from the operation example of the present invention described above, 1) is controlled by the temperature of the evaporator (see 70 in Fig. 1), and the temperature of the compressor (see 10 in Fig. 1) is changed by the change of the room temperature of the automobile detected by the thermistor RTh2. ) Is adjusted.

[Equation 5]

On the other hand, FIG. 8 is a circuit diagram showing the third embodiment of the temperature sensing unit shown in FIG. 4. The voltage V1 of a predetermined level applied from the power input unit 130 is connected to the resistor R2 and the evaporator 70) and is inputted to the inverting terminal (-) of the operational amplifier OP1 for measurement and the inverting terminal (-) of the operational amplifier OP2 for comparison, while being divided by the thermistor RTh, Divided by the resistance R2 and the self resistance of the timer T and input to the non-inverting terminal (+) of the operational amplifier OP1 for measurement amplification

Here, since the voltage input to the non-inverting terminal (+) of the operational amplifier OP1 for measurement amplification is turned on / off according to the switching operation according to the counting of the timer T, As can be seen, by using the timer T, it is possible to control the operation of delaying the on / off operation of the compressor (see 10 in Fig. 1) for a predetermined set time.

FIG. 9 is a circuit diagram showing one embodiment of the switching unit shown in FIG. 4, in which the switching control signal provided by the temperature sensing unit 140 is lowered in voltage by the resistor R6 so that the base end of the control transistor Q1, And is provided at the base end of the low level signal outputting transistor Q3.

Therefore, when a high level signal is provided at the base end of the control transistor Q1 and at the base end of the low level signal output transistor Q3 in the temperature sensing unit 140, the switching transistor Q2 is connected to the power input unit Level signal output transistor Q3 is applied to the engine control unit (not shown) by a compressor (see FIG. 1 (a)) to the compressor driving unit 160 while a DC voltage of a predetermined level input from the switching unit 130 to the switching unit 150 is applied to the compressor driving unit 160 (See reference numeral 10 in FIG.

Thus, the present invention can be applied to an automobile in which the on / off operation of the compressor driving unit 160 is controlled by the engine control unit.

As described above, in the automatic thermostat for an automotive air conditioner according to the present invention, the temperature sensing unit 140 senses the temperature of the evaporator (see 70 in FIG. 1) To the switching unit 150. The switching unit 150 outputs a DC voltage of a predetermined level applied from the power input unit 130 to the compressor driving unit 160 according to the switching control signal, (See 10 in Fig. 1) in which the rotational operation is controlled in accordance with the operation of the compressor driving unit 160 to keep the room temperature of the automobile within a predetermined range, and the evaporator (see 70 in Fig. 1) On the other hand, the off-point of the compressor (see 10 in Fig. 1) is adjusted by operating the off-point adjusting unit 170 while preventing the freezing of the operational amplifier OP1 for measuring amplification The value of the feedback resistor R5 provided is varied to thereby control the compressor (See 10 of FIG. 3).

[Effects of the Invention]

As described above, according to the automatic thermostat of the air conditioner for an automobile of the present invention, since the temperature of the evaporator is sensed and the rotation operation of the compressor is controlled through the switching operation of the corresponding electronic device, The adjustment of the off-point of the compressor is easy, and the hysteresis interval for the operation control of the compressor can be varied.

Claims (12)

An air conditioner for an automobile in which a refrigerant is circulated by a rotating operation of a compressor and cool air is generated through an evaporator, A power input unit for outputting a predetermined driving power, A compressor driving unit selectively driving the compressor by selectively transmitting a driving force generated from an engine of the vehicle to the compressor according to input of the driving power, A temperature sensing unit sensing the temperature of the evaporator and outputting a corresponding switching control signal, And a switching unit for selectively applying the driving power to the compressor driving unit based on a switching control signal input from the temperature sensing unit. The method according to claim 1, The power input unit includes a battery for outputting a DC voltage of a predetermined level, A diode for bypassing a DC voltage output from the battery, A capacitor grounded at one side thereof for smoothing a DC voltage output to the battery and providing a constant voltage, And a Zener diode that is turned on when the DC voltage output from the battery is higher than a predetermined level and is grounded by passing the DC voltage through the ground to shut off the Zener diode. Device. The method according to claim 1, Wherein the compressor driving unit includes a magnetic clutch selectively contacting the driving part of the engine with the rotating part of the compressor according to the magnetization state of the internal electromagnet, And a relay for selectively applying a driving power for magnetizing the electromagnet to the magnetic clutch from the power input unit. The method according to claim 1, The temperature sensing unit may include a temperature sensor for sensing the temperature of the evaporator and converting the temperature of the evaporator into a sensing signal having a corresponding voltage level, Inverting terminal and the inverting terminal and receives a reference voltage of a predetermined level from one of the non-inverting terminal and the inverting terminal, while the non- And a measurement amplifier for generating an output voltage of a multiple of a difference between a voltage level of the sensing signal and a voltage level of the reference voltage by connecting a terminal to which the reference voltage is input and an output terminal thereof with a feedback resistance of a predetermined value, An operational amplifier, Amplifies the voltage level of the sensing signal provided by the temperature sensor and applies a switching control signal of a high level or a low level based on the comparison result to the switching unit And a comparative operational amplifier for controlling the temperature of the air conditioner. 5. The method of claim 4, The comparison operational amplifier compares the output voltage generated by the operational amplifier for measurement and the voltage level of the reference voltage with each other to apply a switching control signal of a high level or a low level based on the comparison result to the switching unit And a comparative operational amplifier that compares the temperature of the air with the temperature of the air. The method according to claim 4 or 5, Characterized in that the voltage level of the reference voltage is varied by a pair of resistors connected in parallel and constituting a composite resistor selectively in accordance with the switching operation of the switch in order to adjust the off point of the compressor Automatic thermostat of air conditioner. The method according to claim 4 or 5, Wherein the voltage level of the reference voltage is varied by a variable resistor to adjust an off-point of the compressor. The method according to claim 4 or 5, Wherein the reference voltage is a sensing signal of a voltage level corresponding to an indoor temperature of the automobile, which is output from a temperature sensor that senses a room temperature of the automobile. The method according to claim 4 or 5, Wherein the reference voltage is delayed for a predetermined time by a predetermined counting means performing different switching operations according to a predetermined set time and input to the comparison means. Device. The method according to claim 4 or 5, Wherein the measurement amplification operational amplifier adjusts the hysteresis interval for the on / off operation of the compressor by varying the variable resistor by further connecting a variable resistor to the feedback resistance in series. Automatic thermostat of the machine. The method according to claim 1, The switching unit may include a switching transistor that performs a switching operation of turning on or off and selectively applies driving power output from the power input unit to the compressor driving unit, A control transistor for controlling a switching operation of the switching transistor by performing a switching operation of turning on or off based on a switching control signal input from the temperature sensing unit and varying a base end potential of the switching transistor Wherein the air conditioner comprises a plurality of air conditioners. 12. The method of claim 11, And a switching transistor for performing a switching operation based on a switching control signal input from the temperature sensing unit and providing a high level or low level signal to a predetermined electronic control means for controlling the engine The automatic thermostat of an air conditioner for an automobile.