JPH02220918A - Automotive air conditioner - Google Patents

Abstract

PURPOSE:To prevent the variation of evaporation pressure in an evaporator by controlling an expansion valve so that, when the temperature pressure is regulated, the amount of liquid refrigerant may become the value corresponding to the evaporation pressure, in the above device with a variable displacement compressor. CONSTITUTION:The temperature of the air at the inlet and outlet of an evaporator 3 is detected by thermisters 16 and 17, respectively, an applied voltage to be applied to the solenoid valve of a control valve 10 is calculated by a micro-computer 14 according to a specified procedure, the maximum and minimum voltages to be applied are limited to a controllable range, and the calculated voltage value is set to the applied voltage for the solenoid valve of the control valve 10. The capacity of a compressor 6 is varied according to whether the acceleration of it is required or not and whether the heat load of it is large or small. On the other hand, an expansion valve 9 is opened or closed according to whether the applied voltage to the solenoid valve of the control valve 10 is large or small, i.e., whether the refrigerant pressure Pe in the evaporator 3 is high or low. With this constitution, the variation of evaporation pressure in the evaporator can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an air conditioning system for automobiles, and more particularly to an automatic military air conditioning system that controls the discharge capacity variable means of a compressor to adjust the evaporation pressure of refrigerant in an evaporator. Regarding.

[Conventional technology]

Japanese Patent Application Laid-Open No. 58-43340 is a known air conditioner for automobiles that controls the discharge capacity variable means of a compressor to adjust the evaporation pressure of refrigerant in an evaporator. This is the air temperature immediately after the evaporator exit (
(cold air temperature) and vehicle interior temperature, for example, when the interior temperature is higher than a set value. The discharge capacity variable means is controlled to set the discharge state of the compressor to a large capacity, thereby increasing the evaporation pressure of the refrigerant in the evaporator, and the compressor is switched between high capacity operation and operation stop according to the cold air temperature. Furthermore, the expansion valve that adjusts the amount of liquid refrigerant supplied to the evaporator is configured to close when the compressor stops operating, thereby stopping the supply of liquid refrigerant.

[Problem that the invention seeks to solve]

However, in the conventional device described above, when the capacity of the compressor is changed and the evaporation pressure of the refrigerant in the evaporator is changed,
No consideration was given to the fact that the optimum amount of liquid refrigerant to be supplied to the evaporator changes, and the amount of liquid refrigerant (refrigerant pressure) in the evaporator is adjusted by the expansion valve and the evaporation pressure is adjusted by the capacity control of the compressor. There was a problem in that the cooler cycle caused hunting due to mismatch with the evaporator, the evaporation pressure of the refrigerant in the evaporator fluctuated, and the temperature of the blown air fluctuated accordingly.

An object of the present invention is to provide an air conditioner for an automobile that adjusts the amount of liquid refrigerant supplied to an evaporator in accordance with capacity control of a compressor and prevents fluctuations in evaporation pressure within the evaporator.

[Means for solving problems]

The above object is a compressor having a discharge capacity variable means;
An evaporator that cools air with refrigerant circulated by the compressor, an expansion valve that adjusts the amount of liquid refrigerant supplied to the evaporator, and a control device that controls the discharge capacity variable device to adjust the evaporation pressure of the refrigerant in the evaporator. In the air conditioner for an automobile, the control means adjusts the evaporation pressure by controlling the expansion valve so that an amount of liquid refrigerant commensurate with the evaporation pressure is obtained.

[Effect]

In the present invention configured in this manner, the expansion valve supplies an amount of liquid refrigerant according to the evaporation pressure of the evaporator, so that the amount of liquid refrigerant (refrigerant pressure) in the evaporator and the evaporation pressure adjusted by the capacity control of the compressor are different. Hunting of the cooler cycle due to mismatching does not occur, and fluctuations in the evaporation pressure within the evaporator are prevented, and accompanying fluctuations in the temperature of the blown air can be prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, an air conditioner for an automobile, which is an embodiment of the present invention and has a variable capacity compressor, includes an intake door 1 that selects air inside the car or air outside the car, and a blower that sends the air selected by the intake door 1 to the inside of the car. 2. It has an evaporator 3 that cools the air, an air mix door 4 that controls the proportion of the cooled air to be reheated, and a shutter 5 that heats the air.

Further, a cooler cycle for cooling the evaporator 3 includes a compressor 6, a condenser 7, and an expansion valve 9, and the compressor 6 compresses the refrigerant evaporated in the evaporator 3. The condenser 7 releases the heat of the compressed high-temperature, high-pressure refrigerant into the air sent by the fan 8, turning it into liquid refrigerant. expansion valve 9
controls the amount of liquid refrigerant supplied to the evaporator 3.

Here, the outlet air temperature Te of the evaporator 3 is somewhat higher than the evaporation temperature of the refrigerant in the evaporator 3.

Also, the refrigerant pressure (evaporation pressure) P in the evaporator 3
There is a refrigerant pressure difference between e and the refrigerant pressure PS at the inlet of the compressor 6 corresponding to the piping pressure loss, and when the piping pressure loss is subtracted from the evaporation pressure pe in the evaporator 3, the refrigerant pressure ps at the compressor inlet is Become.

A control valve 10 constituting a discharge capacity variable means is installed at the inlet of the compressor 6. This control valve 10 has a built-in solenoid valve (not shown), and when the voltage Vs applied to the solenoid valve increases, the refrigerant passage is throttled and the capacity is controlled so that the inlet refrigerant pressure Ps of the compressor 6 becomes higher.As a result, the above-mentioned inlet refrigerant pressure Based on the relationship between ps and the evaporation pressure pe in the evaporator, the evaporation pressure Pe is controlled to be high.

A shutter 11 is provided between the capacitor 7 and the fan 8. The shutter 11 is driven by an actuator 12, and when a pulse is applied, the actuator 12 rotates in proportion to the number of pulses Nl, changing the amount by which the capacitor 7 is blocked. If the amount of condenser 7 that is blocked increases, heat radiation will deteriorate, and refrigerant pressure Pd at the outlet of compressor 6 will increase.

The expansion valve 9 is controlled so that an amount of liquid refrigerant corresponding to the amount of refrigerant evaporated in the evaporator 3 is supplied. That is, the expansion valve 9 has a built-in solenoid valve (not shown), and when the voltage Ve applied to the solenoid valve increases, the refrigerant passage is throttled and the amount of liquid refrigerant supplied to the evaporator 3 is reduced.

The control circuit 13 includes a microcomputer 14 and an amplification port #t15 such as a transistor. The amplifier circuit 15 receives commands from the microcomputer 14 and drives devices such as the control valve 10.

The microcomputer 14 has an A/D conversion function that converts an analog voltage into a digital binary number, and a timer function that starts a program at fixed time intervals.

Hereinafter, the second
Using the flow shown in the figure, the microcomputer 14
Explain the operation.

The flow in FIG. 2 is executed at predetermined time intervals (100 nsec in this embodiment) by the timer function of the microcomputer 14.
Run it every time.

In step 100, the evaporator inlet air temperature Ti is detected by the thermistor 16 provided on the inlet side of the evaporator 3, and is taken in using the A/D conversion function.

In step 101, the target air temperature TeO at the outlet of the evaporator is calculated from the Ti according to the characteristics stored in the microcomputer 14.The characteristics shown in the figure are just an example, and the numerical values will vary depending on the vehicle to which it is applied. The characteristics of the region 7130<2° C. are determined so that it takes a predetermined time (2 hours in this example) for the evaporator 3 to completely freeze.

In addition, the characteristics in the region of 'reo > 2℃ are set at Ti = 20℃, and Ti < 20℃ allows dehumidification to the extent that the windows do not fog up, and Ti > 20℃ provides a comfortable blowing temperature. Determine the characteristics of each so that it can be used.

In step 102, the evaporator outlet air temperature Te is detected by the thermistor 17 provided on the outlet side of the evaporator 3, and is taken in using the A/D conversion function.

In step 103, the temperature difference Tea-Te between the target air temperature Tea and the detected temperature TO is multiplied by a coefficient A to calculate how much the voltage VS to be applied to the solenoid valve of the control valve 10 should be increased or decreased. Then, a new applied voltage vS' is calculated based on the currently applied voltage Vs.

In step 104, the maximum voltage and minimum voltage are limited so that the new applied voltage Vs' falls within the controllable range, and that value is set as the voltage Vs to be applied to the solenoid valve of the control valve 10.

In step 105, acceleration is determined based on the presence or absence of a signal generated by the engine control port i18 during acceleration.

In the case of acceleration, in step 106, the voltage VS is set to the maximum voltage Vsl, that is, a small capacity.

At the step 107, the solenoid applied voltage ■S.

is smaller than a predetermined value Vso, and it is determined whether the heat load is large.

When the heat load is small, the capacity of the compressor 6 is small,
The power consumption of the compressor 6 is low. In this case, in this embodiment, in order to further reduce power consumption and improve acceleration, the magnetic clutch 19 of the compressor 6 is turned off in step 108.

On the other hand, when the heat load is large, the capacity of the compressor 6 is large and the power consumption of the compressor 6 is large.

In this case, the compressor 6 is
Reduces power consumption and improves acceleration. Therefore, in step 109, the McNet clutch 19 is turned on.

When the voltage Vs applied to the solenoid valve of the M control valve 10 is increased and the refrigerant pressure Pe of the evaporator 3 is high, the refrigerant passage of the expansion valve 9 is throttled so that the amount of liquid refrigerant supplied to the evaporator 3 is reduced accordingly.

That is, in step 110, the voltage Ve to be applied to the solenoid valve of the expansion valve 9 is determined from the voltage Vs to be applied to the solenoid valve of the control valve 10 in accordance with a certain memorized characteristic. This characteristic is
It is determined that the voltage Ve increases in proportion to the increase in the voltage Vs.

In step 111, the voltage Vs is applied to the solenoid valve of the control valve 10 to control the capacity of the compressor 6, and in step 112, the voltage ve is applied to the solenoid valve of the expansion valve 9 to adjust the amount of liquid refrigerant supplied to the evaporator 3. do.

When the outside air temperature is low, heat radiation in the condenser 7 is good, and the outlet refrigerant pressure Pd of the compressor 6 is reduced. The discharge capacity variable means of the compressor 6 is configured to use this outlet refrigerant pressure Pd as a power source for changing the capacity of the compressor 6. Therefore, the degree to which the shutter 11 closes the condenser 7 is controlled so that the outlet refrigerant pressure Pd is such that the outlet target air temperature TeO of the evaporator 3 is obtained.

That is, in step 113, the temperature difference Tea- between the target air temperature Tea and the detected temperature Tf3 is determined according to the stored characteristics.
The number Nll of pulses to be applied to the actuator 12 of the shutter 11 is determined from 're, and the number Nll of pulses is output to the actuator 12.

After the above processing is completed, the program waits until the program shown in FIG. 2 is re-executed by the timer function.

According to this embodiment, in steps 110 and 112, the throttle amount of the expansion valve 9 is controlled in accordance with the capacity control of the compressor 6 by the control valve 10, and the refrigerant of the evaporator 3 is adjusted according to the inlet refrigerant pressure ps of the compressor. pressure pe
Since the amount of liquid refrigerant commensurate with the amount is supplied to the evaporator, fluctuations in the evaporation pressure of the refrigerant in the evaporator 3 can be prevented, fluctuations in the blowing air temperature are reduced, and a comfortable blowing temperature can be obtained.

〔Effect of the invention〕

According to the present invention, since fluctuations in refrigerant pressure can be prevented by controlling each component of the cooler cycle in a correlated manner, fluctuations in the blowout air temperature are small and a comfortable blowout temperature can be obtained. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the system configuration of an automobile air conditioner according to an embodiment of the present invention, and FIG. 2 is a flowchart showing a program stored in the microcomputer of FIG. Explanation of symbols 3...Evaporator 6...Compressor 9...Expansion valve 10...Control valve (discharge volume variable means) 13...Control circuit (control means) Applicant Hitachi, Ltd. Agent Patent attorney Yuzuru Kasuga

Claims (1)

[Claims] (1) A compressor having a variable discharge capacity means, an evaporator that cools air with a refrigerant circulated by the compressor, an expansion valve that adjusts the amount of liquid refrigerant supplied to the evaporator, and a variable discharge capacity that controls the In an air conditioner for an automobile including a control means for adjusting the evaporation pressure of refrigerant in the evaporator, the control means controls the expansion valve so that when adjusting the evaporation pressure, an amount of liquid refrigerant commensurate with the evaporation pressure is obtained. An air conditioner for an automobile characterized by controlling.