JP3052094B2 - Vehicle air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle air conditioner which detects the temperature of an evaporator and uses the detected value to prevent freezing of the evaporator and to control an air conditioner.

[0002]

2. Description of the Related Art It is known to provide a temperature sensor for detecting the temperature of an evaporator and to control an air conditioner using the output value of the temperature sensor. For example, Tokiko Sho 62─2
Japanese Patent No. 5522 discloses a technique for turning off the compressor when the evaporator temperature falls below the freezing critical temperature. Japanese Patent Application Laid-Open No. 2-109719 discloses a technique for controlling each air conditioner by taking the evaporator temperature into consideration. There is disclosed a technology for obtaining a total signal for controlling the temperature and controlling the temperature of a vehicle interior to a target temperature.

[0003]

By the way, in order to maintain the function of the evaporator, it is necessary to give the highest priority to the prevention of freezing. For this reason, it is necessary to provide a temperature sensor at the portion of the evaporator where the temperature becomes lowest. preferable.

However, in the temperature control of the evaporator and the blowout temperature control in accordance with the heat exchange capability of the heater unit, it is preferable to detect the average temperature of the evaporator in order to increase the control accuracy. If a temperature sensor is installed at a location where the temperature can be detected, the air conditioner will be controlled at a temperature lower than the average temperature of the actual evaporator, so the actual outlet temperature and evaporator temperature will deviate higher than the target temperature. there were.

[0005] In order to prevent this, a place where the lowest temperature of the evaporator can be detected and a place where the average temperature can be detected are as follows.
It is conceivable to provide a temperature sensor for each, but this complicates the structure and increases the cost.

In view of the above, the present invention has been made in order to solve the above-mentioned drawbacks. One of the temperature sensors attached to the evaporator is used to prevent freezing. It is an object to provide a vehicle air conditioner that can be controlled.

[0007]

The gist of the present invention is, as shown in FIG. 1, of an evaporator.
Evaporator temperature detecting means for detecting the temperature of the lowest temperature, freeze protection means for reducing the amount of refrigerant supplied to the evaporator when the output of the evaporator temperature detecting means is lower than a predetermined temperature, and evaporator temperature detecting Mean temperature calculating means for calculating the average temperature of the evaporator based on the output value of the means and the heat load factor affecting the heat exchange state of the evaporator, and each air conditioner is controlled in consideration of the output of the average temperature calculating means. Air conditioner control means for controlling the air conditioner.

[0008]

Therefore, the evaporator temperature detecting means 100
The temperature of the portion where the temperature of the evaporator becomes the lowest is detected. When the detected value falls below a predetermined temperature, the amount of refrigerant supplied to the evaporator is reduced by the freeze protection means 200, and the evaporator is prevented from freezing. The average temperature calculating means 300 corrects the output value of the evaporator temperature detecting means 100 based on the heat load factor affecting the heat exchange state of the evaporator to calculate the average temperature of the evaporator. Since the air conditioner is controlled in consideration of the average temperature, the same control as provided can be performed without separately providing a temperature sensor for obtaining the average temperature of the evaporator.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, the air conditioner for a vehicle is provided with an inside / outside air switching device 2 at the most upstream side of an air conditioning duct 1.
In the inside / outside air switching device 2, an inside / outside air switching door 5 is disposed at a portion where the inside air inlet 3 and the outside air inlet 4 are separated, and the inside / outside air switching door 5 is operated by an actuator 6 to be introduced into the air conditioning duct 1. The air to be sucked is selected between inside air and outside air, and the suction mode can be changed.

The blower 7 sucks air into the air-conditioning duct 1 and blows the air downstream. An evaporator 8 and a heater core 9 are provided behind the blower 7.

The evaporator 8 is connected to a compressor 10 having a variable capacity mechanism 24, a condenser 11, a liquid tank 12 and an expansion valve 13 by piping so as to constitute a cooling cycle. The clutch is connected via a clutch 15, and the on / off control is performed by connecting and disconnecting the electromagnetic clutch 15. The heater core 9 circulates cooling water of the engine to heat the air. An air mix door 16 is provided in front of the heater core 9, and the opening degree of the air mix door 16 is adjusted by an actuator 17, so that the amount of air passing through the heater core 9 and the amount of air bypassing the heater core 9 are adjusted. Is changed, so that the temperature of the blown air is controlled.

The downstream side of the air-conditioning duct 1 is divided into a defrost outlet 18, a vent outlet 19 and a heat outlet 20 and opens into the vehicle interior 21. Mode doors 22a, 22b and 22c are provided at these separated portions. By operating the mode doors 22a, 22b, 22c with the actuator 23, a desired blowing mode can be obtained.

The actuators 6, 17, 2
3, the motor of the blower 7, the variable capacity mechanism 24 of the compressor 10, and the electromagnetic clutch 15 are controlled based on output signals from the microcomputer 41 via drive circuits 40a to 40f, respectively.

The microcomputer 41 includes a central processing unit (CPU) (not shown) and a read only memory (RO).
M), a random access memory (RAM), an input / output port (I / O), etc., which are known per se. The microcomputer 41 includes a vehicle interior temperature sensor 43 for detecting the temperature in the vehicle interior 21. , An output signal Ta from the outside air temperature sensor 44 for detecting the outside air temperature, an output signal Qs from the insolation sensor 45 for detecting the amount of insolation, and the temperature of the evaporator 8 which is provided at a low temperature point. Output signal T _E from the evaporator temperature sensor 46
Is selected via a multiplexer 47, converted into a digital signal by an A / D converter 48, and input.

The evaporator temperature sensor 46 is provided at or near the lowest temperature of the evaporator 8 in order to prevent the evaporator 8 from freezing. Specifically, for example, the expansion valve 13 and the evaporator 8 It is desirable to mount it on a pipe between the refrigerant inlet and a place where the temperature of air near the refrigerant inlet downstream of the evaporator can be detected, or between fins.

An output signal from the operation panel 25 is input to the microcomputer 41. The operation panel 25 is a blow mode setting device 2 for setting a blow mode other than the defrost mode by operating the MODE switch 26a.
6. A blower capacity setting device 27 for setting the blower capacity by operating the FAN switch 27a, and the up / down switches 28a and 2
It has a temperature setter 28 for setting a set temperature T _D of the passenger compartment 8b, a display unit 30 connected to the microcomputer 41 via the display circuit 29, the blow mode, the blower capacity, and the set temperature, respectively It is displayed.

The operation panel 25 has an AUTO switch 31 for setting the air conditioner in an automatic control mode, an OFF switch 32 for stopping the operation of the air conditioner, a REC switch 33 for setting a suction mode, and a blow mode set to a defrost mode. DEF switch 34, compressor 1
An A / C switch 35 for instructing operation of 0 and an AMB switch 36 for instructing display of the outside air temperature on a display unit are provided.

FIG. 3 is a functional block diagram showing a specific control example of the air conditioner in this embodiment, which will be described prior to the description of the control operation example by the microcomputer 31 described above.

The temperature T _E which is detected by the evaporator temperature sensor 46 is a temperature of the coldest point of the evaporator 8, it falls below the limit temperature of the temperature T _E is not frozen, and freeze gradually from the coldest point Because it comes, this T
The presence or absence of freezing is determined based on _E (201). If the temperature is lower than the freezing critical temperature, the electromagnetic clutch 1 of the compressor 10 is determined.
Turn 5 OFF.

Further, the T _E, the outside air temperature Ta, and the average temperature T of the evaporator on the basis of the target air volume V 'to be described later
_{The EAV} is calculated (301). The method of calculating the average temperature _TEAV will be described later in detail, but the average temperature is used for controlling each air conditioner that determines the air conditioning state.

First, based on the outside air temperature Ta detected by the outside air temperature sensor 44, the vehicle interior temperature Tr detected by the vehicle interior temperature sensor 43, the set temperature T _D set by the temperature setting device, and the average temperature T _EAV . Then, a total signal T used for determining the target control amount of the air conditioner is calculated (401).

The operation from this complex signal T, and calculates a target temperature T _E 'of the evaporator (402), such that the difference between the T _EAV is a predetermined amount (alpha) hereinafter, the variable displacement mechanism 24 of the compressor 10 Then, the discharge capacity of the compressor is controlled (403).

Further, the air mixing door 1 is obtained from the total signal T.
6 is calculated (404), and the target opening (Θ ') and the actual opening (Θ) of the air mix door 16 are calculated.
The position of the air mix door 16 is controlled so that the difference from the air mix door 16 is equal to or less than a predetermined amount (β) (405).

Further, based on the total signal T, a target air volume is calculated as a target applied voltage (V ') to the blower motor (406), and this target applied voltage (V') and the actual voltage (B ') of the blower motor are calculated. The control amount of the power transistor (408) is adjusted to control the air flow so that the difference from V) is within a predetermined amount (γ) (407).

Next, an operation example of the microcomputer 41 will be described with reference to a flowchart shown in FIG. 4. When the air conditioner starts operating, the microcomputer 41 starts executing the program from a start step 50. , An output signal from each sensor is input, and in step 52, a switch signal from the operation panel 25 is input.

In step 53, the above-mentioned total signal T is calculated based on the equation (1).

[0028]

T = Tr + A · Ta + B · T _EAV −C · T _D + D

Here, A, B, and C are constants calculated experimentally, and D is a correction term.

After the total signal T is calculated, step 5
At 4, the control of the air mix door 16 described above is performed. Here, the target opening (Θ ′) of the air mix door 16 is calculated so that, for example, a characteristic substantially proportional to the magnitude of the total signal T is obtained as shown in FIG.

In the next step 55, a blower control as shown in FIG. 6 is performed. More specifically, in step 58, it is determined whether or not there is a request to stop (OFF) the fan (FAN). In step 59, the fan (27) is pressed to release the fan (FA).
It is determined whether or not there is a request for the manual mode of N).
Going to 0, the blower is stopped, and if there is a request for the manual mode of the blower 7, the process goes to step 61, where the blower 7 is manually controlled. If there is no request, the process proceeds to step 62, and the blower control accompanying the above-described calculation of the target air volume is performed. Here, the target applied voltage (V ') corresponding to the target air volume is calculated so that a low air volume is obtained in the intermediate region of the total signal T, for example, as shown in step 62.

Thereafter, in step 56 of the main routine, control of the compressor 10 as shown in FIG. 7 is performed.

In this control, in step 63, it is determined whether or not there is a request to stop (OFF) the blower (FAN). In step 64, it is determined whether or not the A / C switch 35 is turned on. If there is a request to stop or the A / C switch 35 is not turned on, the process proceeds to step 65, where the compressor 10 is stopped (OFF). On the other hand, there is no request to stop the blower 7 and A /
If the C switch 35 is turned on, step 6
Advances to 6, the temperature T _E which is detected by the evaporator temperature sensor 46, predetermined freezing critical temperature (e.g. 0.5
It is determined whether the temperature is below 3 ° C.). If the temperature is lower than the freezing critical temperature, the process proceeds to step 65 to prevent the evaporator 8 from freezing, and the compressor 10 is stopped (OFF). If the freezing critical temperature has not been reached, the routine proceeds to step 67, where the compressor 10 is operated (O
N), and in steps 68 to 70, the above-described compressor control is performed.

[0034] That is, in step 68, so that the characteristic shown in the step is obtained, 'is calculated, in step 70, the target temperature T _E' from a comprehensive signal T of the evaporator target temperature T _E at Step 69 and The difference between the calculated average temperature T _EAV of the evaporator 8 is, for example, 1 ° C.
The capacity of the compressor 10 is controlled so as to be within the range.

FIG. 8 shows a specific example of the calculation of the average temperature T _EAV of the evaporator 10 in step 69. In step 71, the temperature T _E detected by the evaporator temperature sensor 46, the outside air temperature Ta,
And the target air volume V ′ is input. In step 72, it is determined whether the outside air temperature belongs to the low outside air area (A), the middle outside air area (B), or the high outside air area (C).

Then, in steps 73 and 74,
The region determined in the previous step 72 is determined, and if it is determined that the region belongs to the low outside air region (A), the process proceeds to step 7.
Proceed to 5, determines the target air volume V 'is whether greater than a predetermined airflow K _1.

When the outside air temperature is low and the air volume is small, the heat load on the evaporator 8 is small, and the amount of refrigerant flowing in the evaporator is small. Therefore, the liquid refrigerant flows only near the refrigerant inlet and does not flow near the refrigerant inlet. T _E detected by the evaporator temperature sensor 46 and the evaporator 8
Is larger than the average temperature. On the other hand, when the outside air temperature is low but the air volume is large, the heat load of the evaporator 8 increases, and the amount of the refrigerant flowing in the evaporator increases. Therefore, the temperature is detected by the evaporator temperature sensor 46 near the refrigerant inlet. the difference between the temperature T the average temperature of the _E and the evaporator is reduced that. Therefore, in order to calculate T _EAV based on T _E , it is necessary to consider the magnitude of the difference between T _E and T _EAV, and the target air volume V ′ is equal to the predetermined air volume K _1.
If less than, and the correction amount corresponding to the difference between T _E and T _EAV the (alpha) and a large value alpha ₁ (step 76), when V 'is greater than K ₁ is smaller correction amount (alpha) Value α ₂
(Α ₁ > α ₂ > 0) (step 77).

If it is determined that the outside air temperature Ta belongs to the high outside air area (C), the routine proceeds to step 78,
Target airflow V 'is equal to or greater than a predetermined air volume K _2.

When the outside air temperature is high and the air volume is large, the heat load on the evaporator 8 is large, and the amount of refrigerant flowing in the evaporator is large. the difference between the average temperature T _EAV temperature T _E and the evaporator detected by the evaporator temperature sensor 46 in the vicinity is increased. On the other hand, when the outside air temperature is high but the air volume is small, the heat load of the evaporator 8 is reduced to reduce the degree of superheat, and the temperature T _E detected by the evaporator temperature sensor 46 near the refrigerant inlet and the evaporator 8 Is smaller than the average temperature _TEAV . Therefore, to calculate T _EAV based on T _E , if the target air volume V ′ is larger than the predetermined air volume K ₂ ,
_The correction amount (α) corresponding to the difference between _E and T _EAV is set to a large value α.
₃ (step 79), V 'is a case K ₂ is smaller than the correction amount (alpha) to a small value of _{α 4 (α 3> α 4} > 0) ( step 80).

On the other hand, when it is determined that the outside air temperature Ta belongs to the intermediate outside air area (B), the heat load of the evaporator 8 is not so high, and the refrigerant circulates throughout the evaporator. , The temperature T _E detected by the evaporator temperature sensor 46 near the refrigerant inlet
And the average temperature T _EAV of the evaporator 8 is hardly different. Therefore, the correction amount (α) corresponding to the difference between T _E and T _EAV is set to zero (step 81).

The above correction amount (α) is experimentally determined in advance. After the correction amount (α) is determined,
Proceeding to step 82, the average evaporator temperature T _EAV is calculated as the sum of T _E and α, as shown by equation (2).

[0042]

## EQU2 ## T _EAV = T _E + α

In this embodiment, among the air conditioners, only the control operation examples of the air mix door, the blower, and the compressor are shown. However, other air conditioners, such as an intake device and a mode, are included in the main routine. A step 57 for controlling a door or the like may be added, and these air conditioners may be driven and controlled based on the total signal T in consideration of _TEAV .

[0044]

As described above, according to the present invention,
The temperature of the coldest part of the evaporator is actually detected, and the average temperature of the evaporator is calculated by correcting the temperature of the lowest temperature part of the evaporator based on the heat load factor that affects the heat exchange state of the evaporator. By doing so, each can be obtained, so that freezing can be prevented by one temperature sensor without providing two temperature sensors in the evaporator, and the air conditioner can be controlled with high accuracy.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a vehicle air conditioning control device according to the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of a vehicle air conditioner according to the present invention.

3 is a functional block diagram illustrating a control operation example of the vehicle air conditioner in FIG. 2;

FIG. 4 is a flowchart showing a main control example of a microcomputer used in the vehicle air conditioner of FIG. 2;

FIG. 5 is a characteristic diagram showing a relationship between a total signal (T) and a target opening (Θ ′) of an air mix door.

FIG. 6 is a flowchart illustrating an example of a subroutine of blower control in main control in FIG. 4;

FIG. 7 is a flowchart showing a subroutine example of compressor control in main control in FIG. 4;

FIG. 8 is a flowchart showing an example of average temperature calculation in a subroutine in FIG. 7;

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 evaporator temperature detecting means 200 freezing protection means 300 average temperature calculating means 400 air conditioning control means

Claims (1)

(57) [Claims] An evaporator temperature detecting means for detecting a temperature of a portion of the evaporator where the temperature is the lowest, and a refrigerant supply amount to the evaporator when an output of the evaporator temperature detecting means is lower than a predetermined temperature. Freeze protection means for lowering the temperature; average temperature calculation means for calculating an average temperature of the evaporator based on an output value of the evaporator temperature detection means and a heat load factor affecting a heat exchange state of the evaporator; An air conditioner for a vehicle, comprising: an air conditioning control unit that controls each air conditioning device in consideration of an output of a calculation unit.