JPH0156923B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air conditioner for a vehicle, and more particularly to an air conditioner for a vehicle that suppresses fluctuations in cabin temperature in response to changes in heat load.

An air conditioner installed in a vehicle (hereinafter referred to as an air conditioner) compresses refrigerant using a compressor connected to the engine via an electromagnetic clutch, sends it to a condenser, liquefies it, and stores it in a liquid receiver. The high-pressure refrigerant in the container is lowered to low pressure by an expansion valve and blown into the evaporator.
The air is evaporated in the evaporator to remove ambient heat, and air from inside or outside the vehicle is passed between each pipe of the evaporator using a blower to turn it into cold air, thereby cooling the interior of the vehicle.

In general, air conditioners perform appropriate capacity control by switching the capacity of the compressor or controlling the on/off of an electromagnetic clutch depending on the heat load. Such a control device senses the temperature of the air immediately after the evaporator or the temperature or pressure of the refrigerant in the evaporator, and adjusts the compressor to operate the compressor at a discharge capacity corresponding to the set value of the temperature or pressure in response to this sensing signal. "Automotive refrigeration cycle control device" that controls the functional power so that the refrigeration cycle operates at a capacity according to the load at the time.
(Japanese Unexamined Patent Publication No. 13962/1983) has been proposed.

According to this control device, as shown in FIG. 1, when the evaporator temperature T is equal to or higher than the compressor large capacity switching set temperature _T1 , the compressor is controlled for large capacity operation to maximize the cooling capacity, and the evaporator temperature is When the evaporator temperature decreases and reaches the compressor small capacity switching set temperature _T3 , the compressor is switched to a small capacity to reduce the cooling capacity, and when the evaporator temperature further decreases and reaches the compressor stop temperature _T4 , the electromagnetic clutch is switched on. is deenergized (off) to stop the compressor. When the compressor is stopped and the evaporator temperature gradually rises and reaches the compressor starting temperature _T2 , the electromagnetic clutch is energized (on) to drive the compressor at the small capacity and restart the cooling cycle. This operation is repeated to maintain the evaporator temperature at a substantially average temperature of T ₂ and T ₄ (T ₂ +T ₄ )/2.

However, when the air conditioner is operating stably under a certain heat load condition as described above, if the heat load changes due to some reason, such as a drop in engine speed or a sudden change in outside temperature, the cooling cycle may become unstable. As a result, the air temperature at the outlet of the evaporator changes, which ultimately causes a change in the cabin temperature, and the temperature control has to be set again, which is a disadvantage.

For example, if the cooling cycle is stabilized by the compressor's small capacity on-off operation as shown by the curve in Figure 1 under certain heat load conditions, the evaporator temperature will vary between temperatures T ₂ and T ₄ . Changes as shown,
On average, air cooled by the evaporator at a temperature of (T ₂ +T ₄ )/2 is blown into the passenger compartment.
However, as the engine speed decreases, heat load fluctuations occur and the stable state of the cooling cycle changes, causing the evaporator fin temperature to rise and drop between temperatures T ₁ and T ₃ , as shown by the curve in Figure 1. If the temperature of the air cooled by the evaporator changes as shown in the figure, the average temperature of the air cooled by the evaporator will be (T ₁ + T ₃ )/2, and the average temperature difference ΔT will increase, resulting in This causes an increase in the temperature, that is, the temperature in the passenger compartment, resulting in a worsening of the feeling.

The present invention has been made in view of the above points, and an object of the present invention is to suppress fluctuations in cabin temperature even when the heat load fluctuates. sensing the temperature or pressure related to the temperature to obtain a corresponding signal, comparing the signal with a set value corresponding to the set temperature, and operating the compressor to control the discharge capacity according to the comparison result; In a vehicle air conditioner that performs optimal capacity control according to heat load, an average value of temperature or pressure related to the degree of cooling of the evaporator is detected, and when the value is large, the set value is decreased. The present invention provides an air conditioner for a vehicle, which is equipped with a correction means for increasing the set value when the set value is small, and suppresses fluctuations in the vehicle interior temperature.

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 shows a control circuit of a compressor to which the present invention is applied, and a temperature sensor 1 detects the air temperature immediately after the evaporator (at the outlet) and is composed of a negative resistance element such as a thermistor. The evaporator is located at a specified location in the evaporator. One connection terminal of this temperature sensor 1 is connected to a power supply connection line 10 via a variable resistor VR for temperature adjustment, and the other connection terminal is connected to a ground line 11. The temperature sensor 2 senses the average temperature of the air immediately after the evaporator, and like the temperature sensor 1, it is disposed at a predetermined location of the evaporator. Like the temperature sensor 1, this temperature sensor 2 is also composed of a negative resistance element such as a thermistor, and one connection terminal is connected to the wire 10, and the other connection terminal is connected to the wire 10 through resistors _R1 , _R2 , and _R3. A capacitor C is connected to the temperature sensor 2 in parallel. A series circuit of these temperature sensors 2 and resistors R ₁ , R ₂ and R ₃ constitutes a temperature setting circuit.

The capacitor C is used to detect the evaporator temperature on average by preventing a sudden change in the resistance value of the temperature sensor 2, and is not particularly necessary if the temperature sensor 2 with a large heat capacity is used.

The connection point a between the variable resistor VR and the temperature sensor 1 is connected via resistors R ₄ and R ₅ to a comparator 3 for electromagnetic clutch on-off control and a comparator 4 for compressor capacity switching control.
are connected to each inverting input terminal of the The connection point b between the resistor R ₁ and the resistor R ₂ is connected to the output terminal of the comparator 3 via the non-inverting input terminal of the comparator 3, the resistor R _{6 ,} and the diode D ₁ .
The connection point c with _R3 is connected to the comparator 4 through the non-inverting input terminal of the comparator 4, the resistor _R8 , and the diode _D2 .
is connected to the output terminal of Capacitors C ₁ and C ₂ are connected between each inverting input terminal and non-inverting input terminal of comparators 3 and 4, and these comparators 3 and 4
The output terminals of are connected to the bases of transistors Tr ₁ and Tr ₃ via resistors R ₇ and R ₉ , respectively.

The potential Va at the connection point a changes as shown in the curve in FIG. In response to changes in , the curve changes as shown in the figure. These potentials
Vb and Vc correspond to the average temperature of the evaporator, and the potentials Vb and Vc at the connection points b and c form the reference voltages of the comparators 3 and 4, respectively, and serve as the lower limit of the threshold value. Then, the intersection point P between the curve and V,
Q is set to be the compressor stop temperature T ₄ and the compressor small capacity switching temperature T ₃ respectively. Also,
The threshold values of these comparators 3 and 4 are set to be the compressor starting temperature _T2 and the compressor large capacity switching temperature _T1 , respectively.

The collector of the transistor Tr ₁ is connected to the line 10, the emitter to the line 11 via the resistor R ₁₀ , the base of the transistor Tr ₂ to the emitter of the transistor Tr ₁ , the collector to the line 10 via the coil 5a of the relay 5. , the emitter is connected to line 11. The collector of transistor Tr ₂ is connected to line 10 via a protection diode D ₃ . One connection terminal of the electromagnetic clutch 6 is the contact 5b of the relay 5.
The other connecting terminal is connected to the line 11 via the line 10 . When the electromagnetic clutch 6 is energized, the compressor (variable displacement compressor) is connected to an engine (not shown).
The compressor is connected to the engine, and when it is deenergized, the compressor is disconnected from the engine.

The collector of the transistor Tr ₃ is connected to the line 10 through the resistor R ₁₁ , the emitter is connected to the line 11, the base of the transistor Tr ₄ is connected to the collector of the transistor Tr ₃ , the collector is connected to the line 10 through the coil 7a of the relay 7. , the emitter is connected to line 11, and the collector of transistor Tr ₄ is connected to line 10 via a protection diode D ₄ . One connection terminal of the solenoid valve 8 is connected to a line 10 via a contact 7a of the relay 7, and the other connection terminal line 11. The electromagnetic valve 8 controls the capacity of the compressor, and when energized, the compressor is switched to a small capacity, and when deenergized, the compressor is switched to a large capacity.

In such a configuration, the temperature of the evaporator is equal to the temperature T ₃
In the above case, as shown in FIG. 3, the potential Va at the connection point a is lower than the potentials Vb and Vc at the connection points b and c,
The outputs of comparators 3 and 4 both become high level. When the output of comparator 3 becomes high level, the transistor
Tr ₁ and Tr ₂ conduct (hereinafter referred to as on) and relay 5
The coil 5a is energized and the contact 5b is closed,
The electromagnetic clutch 6 is energized to drive the compressor,
A cooling cycle is performed. Furthermore, when the output of the comparator 4 is at a high level, the transistor Tr ₃ is turned on, the transistor Tr ₄ is turned off (hereinafter referred to as off), the coil 7a of the relay 7 is deenergized, and the contact 7b is turned on.
is opened, the solenoid valve 8 is deenergized, and the compressor is switched to large capacity. Thus, the compressor is controlled to operate at a large capacity, and cooling is performed.

When the cooling is performed and the temperature of the evaporator decreases and reaches the compressor small capacity switching temperature _T3 , Va=Vc,
The output of comparator 4 becomes low level, and the transistor
Tr ₃ is turned off, transistor Tr ₄ is turned on, coil 7a of relay 7 is energized, contact 7b is closed, solenoid valve 8 is energized, and the compressor is switched to a small capacity. The compressor is then operated at a small capacity to continue the cooling cycle. When the temperature of the evaporator further decreases and reaches the compressor stop temperature _T4 , Va=Vb, the output of the comparator 3 becomes a low level, transistors _Tr1 and _Tr2 are turned off, and the coil 5 of the relay 5 is turned off.
a is deenergized, contact 5b is opened, electromagnetic clutch 6 is deenergized, and the compressor is stopped. Thereafter, as mentioned above, the compressor is controlled to operate at a small capacity on and off in accordance with the temperature change of the evaporator, and as shown in the curve in Fig. 4, the evaporator temperature is between T ₄ and T ₂ . The room temperature is approximately the average temperature (T ₄ + T ₂ )/
2. Such control is similar to that shown in FIG. 1 above.

Now, when the evaporator is operating at the average temperature (T ₄ + T ₂ )/2, for example, if the vehicle speed decreases and the compressor rotational speed decreases, and the compression function becomes insufficient, the compressor becomes Instead of switching control between capacity and small capacity, the temperature of the evaporator would normally be the same as the first one mentioned above.
As shown by the curve in the figure, it is controlled between the large capacity switching temperature T ₁ and the small capacity switching temperature T ₃ .
The average temperature of the evaporator will be controlled to (T ₁ +T ₃ )/2.

However, in such a state, the air temperature in the evaporator becomes higher than that during the previous small capacity on-off control of the compressor, so the resistance value of the temperature sensor 2 becomes smaller, and as a result, the potential at the connection points b and c decreases. , the reference potentials Vb and Vc of comparators 3 and 4 rise as shown in FIG. On the other hand, the resistance value of the sensor 1 decreases, and the potential Va at the connection point a decreases. As a result, the threshold values of the comparators 3 and 4 become higher in accordance with the increase in the reference potentials Vb and Vc and the decrease in the potential Va, respectively. In other words, the compressor on-off switching set temperature
T ₂ , T ₄ and compressor large/small capacity switching setting temperature
This means that T ₁ and T ₃ have become lower.

Therefore, the set temperature for switching between large and small capacity of the compressor in such a state is T ₁ '(<
T ₁ ), T ₃ ′ (<T ₃ ), the evaporator temperature will vary between these temperatures T 1 ′ and T ₃ ′, as shown by the curve in the same figure.
T ₃ ′, and its average temperature is (T ₁ ′+
T ₃ ′)/2, which is lower than the average temperature of the set temperatures T ₁ and T ₃ (T ₁ +T ₃ )/2. As a result, the average temperature of the evaporator during compressor small capacity on-off control (T ₄ +T ₂ )/2 and the average temperature of the evaporator during compressor large and small capacity switching control (T ₁ '+
The temperature difference ΔT' from T ₃ ')/2 is smaller than the temperature difference ΔT during the control shown in FIG.

Therefore, even if the stable state of the cooling cycle changes due to fluctuations in the heat load, the average temperature of the evaporator, that is, the change in the air temperature at the outlet of the evaporator, can be suppressed to a small extent, and the temperature in the passenger compartment changes accordingly. This makes it possible to suppress fluctuations to a small extent.

In addition, contrary to the above, when the air temperature of the evaporator decreases, the resistance value of the temperature sensor 2 increases, and accordingly, the potentials of the connection points b and c, that is, the reference potentials Vb and Vc of the comparators 3 and 4 decrease. On the other hand, temperature sensor 1
The resistance value of becomes large, and the potential Va at the connection point a rises. As a result, the threshold values of the comparators 3 and 4 are lowered in accordance with the decrease in the reference potentials Vb and Vc and the increase in the potential Va. That is, the compressor on-off switching set temperatures T ₂ and T ₄ and the compressor large and small capacity switching set temperatures T ₁ and T ₃ become higher. As a result, as in the case described above, fluctuations in the cabin temperature can be suppressed to a small extent.

In this embodiment, a case has been described in which the temperature setting value is corrected by detecting the average temperature of the evaporator. However, the present invention is not limited to this, and the correction may be performed based on other factors such as refrigerant pressure. You may also do so.

Further, in this embodiment, a case has been described in which a temperature sensor for temperature control and a temperature sensor for correction are used, but the present invention is not limited to this. You may also do so.

As explained above, according to the present invention, the temperature or pressure related to the degree of cooling of the evaporator is sensed to obtain a corresponding signal, the signal is compared with a set value corresponding to the set temperature, and the comparison result is In a vehicle air conditioning system, the compressor is operated according to the heat load to control the discharge capacity, and the capacity is optimally controlled according to the heat load.
comprising a correction means for detecting an average value of temperature or pressure related to the degree of cooling of the evaporator, lowering the set value when the value is large, and increasing the set value when the value is small; Since the change in the temperature of the passenger compartment is made small, even if the stable state of the cooling cycle changes due to a change in the heat load, the change in the cabin temperature can be suppressed to a small extent, and comfortable cooling can be performed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing temperature changes in the evaporator due to heat load fluctuations, FIG. 2 is a circuit diagram showing an embodiment of the control circuit for a vehicle air conditioner according to the present invention, and FIG. FIG. 4 is a diagram showing changes in potential at connection points a to c with respect to temperature, and FIG. 4 is a diagram showing temperature correction of the cooling cycle by the control circuit of FIG. 2. 1, 2... Temperature sensor, 3, 4... Comparator,
5, 7... Relay, 6... Electromagnetic clutch, 8...
Solenoid valve, VR... variable resistor, Tr ₁ to _{Tr 4} ... transistor, R ₁ to _{R 11} ... resistor, D ₁ to _{D 4} ... diode.

Claims (1)

[Claims] 1 Sense the temperature or pressure related to the degree of cooling of the evaporator to obtain a corresponding signal, compare the signal with a set value corresponding to the set temperature, and operate the compressor to discharge according to the comparison result. In a vehicle air conditioner that controls capacity and performs optimal capacity control according to heat load, the average value of temperature or pressure related to the degree of cooling of the evaporator is detected, and when the average value is large, the An air conditioner for a vehicle, comprising a correction means for lowering a set value and increasing the set value when the set value is small, thereby suppressing fluctuations in vehicle interior temperature.