JPS6324842B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle air conditioner, and in particular, to a control circuit that detects the temperature of a cooler, controls a cooling cycle, and prevents the cooler from freezing. This is related to a device that is set to .

A conventional air conditioner is constructed as shown in Fig. 1, in which air is absorbed by a blower 2 installed in an air duct 1, cooled by a cooler 3 consisting of an evaporator, and sent out in the direction of the arrow. However, the warm air is heated by the heater 4, mixed at a mixing ratio according to the opening degree of the air mix door 5, and is blown into the vehicle interior at a predetermined temperature.

The cooler 3 also has a temperature detector 6 near it.
is arranged to detect the temperature of the cooler 3 and stop the compressor of the cooling cycle when the temperature of the cooler 3 falls below a predetermined value.
This prevents the cooler 3 from freezing.

However, in conventional vehicle air conditioners, the cooling cycle is operated until the cooler 3 reaches a temperature just before freezing, and even when the outside air temperature is low and air conditioning is not required, cold air flows into the heater 4. Since the cold air is sent to the side and heated by the heater 4 to obtain blown air at a predetermined temperature, the energy efficiency of the equipment as a whole deteriorates.

The purpose of the present invention is to fundamentally eliminate the conventional drawbacks, and when the ambient temperature of outside air etc. drops, the temperature level for stopping the compressor is raised, and when the ambient temperature rises, the compressor is stopped. The present invention provides an extremely rational air conditioner that controls the operating temperature level of the compressor and improves the energy efficiency of the entire system by lowering the temperature level for stopping the compressor.

The details of the present invention will be explained below with reference to FIG. 2 and subsequent figures showing embodiments.

FIG. 2 is a circuit diagram of the control circuit, in which the variable resistance element RX and the second
A thermistor Th ₂ is _provided as a _temperature detector, and a variable resistance element RX and a thermistor Th The voltage at terminal ₂ changes, thereby producing detection outputs for the air mix door detection angle and cooler temperature.

Since the angle θ of the air mix door is adjusted according to the room temperature, the variable resistance element RX such as a potentiometer or a variable resistor is linked to this, and the air mix door opening/closing angle θ is detected as an electrical signal. In this case, the angle θ is set to become smaller as the indoor temperature becomes lower, and to become larger as the output of the variable resistance element RX increases.

Furthermore, the detection output of the variable resistance element RX is applied to the inverting input of the operational amplifier CP ₁ via the diode D ₂ and the resistor R ₆ , but the voltage divided by the resistors R ₃ and R ₄ is also applied to the diode D _{1 .} When the detection angle θ of the variable resistance element _RX is small and the voltage of the detection output is higher than the anode side voltage of the diode _D1 , the output voltage of the diode _D1 is is off, diode _D2 is on, and variable resistance element RX
The output of the variable resistance element changes the inverting input of the operational amplifier CP ₁ , and the detection angle θ exceeds a predetermined value, and the voltage on the anode side of the diode D ₁
When the output voltage of RX decreases, diode _D1 turns on, diode _D2 turns off, and resistors _R3 ,
A voltage determined by the voltage division ratio of _R4 is applied to the inverting input of operational amplifier _CP1 , and variable resistance element RX
The input voltage of comparator _CP1 remains constant regardless of changes in the output of.

That is, resistors R ₃ , R ₄ and diode D ₁ ,
D ₂ acts as a limiting circuit and apparently keeps the detection output of the variable resistance element RX in a constant state.

On the other hand, the voltage divided by the resistor R ₅ and the variable resistor RV for level adjustment is applied as a reference voltage to the non-inverting input of the operational amplifier CP ₁ via the resistor R ₇ . , the operational amplifier _CP1 is configured to generate an output according to the voltage difference between both inputs.

However, the output of operational amplifier CP ₁ is a diode
Diode _D3 is connected to the connection point of resistors _R9 and _R10 through D3, and only when the output voltage of operational amplifier _CP1 is lower than the voltage at the connection point, diode _D3 is turned on, and the operational amplifier CP The voltage at the connection point is controlled in accordance with the output of CP ₁ and is applied to the non-inverting input of operational amplifier CP ₂ via resistor R ₁₂ and the reference voltage.

The operational amplifier CP ₂ is given the detection output of the thermistor Th ₂ , and the difference between both inputs is the output of the operational amplifier CP 2.
It is obtained as the output of CP ₂ , and if the reference voltage of operational amplifier CP ₂ is now constant, when the detection output voltage of the thermistor Th ₂ decreases due to an increase in the detection temperature of the thermistor Th 2, the output voltage of the operational amplifier CP ₂ increases, Resistor
Through _R14 and diode _D5 , transistor Q is turned on to make the terminal voltage of resistor _R15 positive, operating relay RY, turning on its contact ry, and engaging compressor magnetic clutch MC. The compressor is in an operating state.

In addition, due to a decrease in the detection temperature of thermistor Th ₂ ,
If its detection output voltage increases, the operational amplifier CP ₂
The output voltage of the compressor decreases and transistor Q is turned off, so relay RY is restored and magnetic clutch MC is opened, stopping the compressor.

However, the resistors R ₉ , R ₁₀ and the diode D ₃ provided on the non-inverting input side of the operational amplifier CP ₂ act as a limiting circuit, and the output voltage of _the operational amplifier CP _{1 is} When the voltage becomes higher than the connection point voltage, the diode _D3 is turned off, so that the reference voltage of the operational amplifier _CP2 becomes a constant state determined by the voltage division ratio of the resistors _R9 and _R10 .

On the other hand, until the reference voltage of operational amplifier CP ₂ becomes constant, the reference voltage is
A thermistor that is controlled according to the detection angle θ of RX, and the relay RY restores operation accordingly.
The detected temperature of Th ₂ also changes.

In addition, operational amplifier CP ₁ is provided with negative feedback via diode D ₃ , resistor R ₈ and capacitor C, and exhibits an integral action only when diode D ₃ is turned on. , operational amplifier CP ₂ has diode D ₄ and resistor
Positive feedback is provided by _R13 , and when the output voltage drops below the reference voltage, diode _D4 turns on,
Since they exhibit a positive feedback effect, they stabilize the control operation and provide hysteresis characteristics.

Therefore, as shown in Figure 3, the relationship between the detected angle θ of the variable resistance element RX, the detected temperature _tb of the thermistor _Th2 , and the ON state when the compressor is in operation and the OFF state when the compressor is in a stopped state is shown. is low and the introduced air temperature is low, so the detection angle θ of variable resistance element RX is relatively small angle θ1
When detected, the temperature detected by the thermistor Th ₂ drops to a relatively high temperature level T _b11 and the compressor is turned off, and when the detected temperature rises to T _b12 , the compressor is turned on.

Also, for example, if the outside air temperature becomes high, the introduced air temperature becomes high, and the detection angle θ of the variable resistance element RX becomes θ2 or more, the detection temperature of the thermistor Th ₂ , which turns the compressor ON and OFF, becomes constant.
Relatively low temperature level (temperature just before the cooler freezes)
It turns OFF when it drops to t _b21 , and turns ON when it rises to T _b22 . Therefore, if the temperature in the surrounding area other than cooler 3 is low, the opening degree θ will be small and the reference voltage will increase, so when the temperature of the cooler detected by thermistor Th ₂ is at a relatively high level, the cooling When the cycle is stopped and the ambient temperature becomes high, the opening degree θ becomes large and the reference voltage decreases, so the operation of the cooling cycle is continued until the temperature of the cooler reaches a low temperature level (temperature just before freezing). This results in a reasonable compressor operating temperature level setting.

In the present invention, since the variable resistance element RX is used as the first temperature detector, the comparator is controlled in accordance with the opening degree of the air mix door, which directly controls the temperature of the blown air, so the temperature of the blown air can be determined more accurately. can be controlled.

In addition, depending on the conditions, the detection output of the variable resistance element RX may be appropriately amplified and then directly connected to the operational amplifier _CP2.
Resistors R ₃ , R ₄ , which may be given as reference voltages for
Limiting circuit with diodes D ₁ , D ₂ and resistors
Even if the limiting circuit including R ₉ , R ₁₀ and the diode D ₃ is omitted, the structure is essentially the same, and various modifications are possible.

As is clear from the above explanation, according to the present invention, the cooling cycle is rationally operated and stopped according to the ambient temperature, and the energy efficiency of the entire device is significantly improved by improving the heating efficiency of the heater. As a result, significant effects can be obtained in terms of energy saving and reducing unnecessary wear and tear on the compressor.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an air conditioner, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing the relationship between the compressor operating status and detected temperature using the circuit shown in FIG. 2. . 3... Cooler, 4... Heater, 5... Air mix door, RX... Variable resistance element (first temperature detector), Th ₂ ... Thermistor (second temperature detector),
CP ₂ ...Operation amplifier, Q...Transistor, RY
...Relay, MC...Magnetic clutch.

Claims (1)

[Scope of Claims] 1. An air conditioner including a cooler, a heater, and an air mix door that changes the mixing ratio of cold air from the cooler and warm air from the heater, wherein the angle of the air mix door is adjusted. a first temperature detector that includes a detection element and outputs an angle signal as a reference voltage; a second temperature detector that detects the temperature of the cooler; and a reference voltage from the first temperature detector and the second temperature detector. and a comparator inputting the output from the temperature detector, and the comparator stops the cooling cycle of the cooler when the temperature of the cooler falls below a predetermined temperature determined by the reference voltage. An air conditioner characterized by: 2. Claim 1, characterized in that a limiting circuit is provided to keep the reference voltage of the first temperature detector constant when the detected angle of the air mix door by the first temperature detector exceeds a predetermined angle. air conditioner.