JPH04372420A - Air conditioning device for vehicle - Google Patents

Abstract

PURPOSE:To prevent freezing, and maintain a high-precision air conditioning control by using a single temperature sensor installed at an evaporator of an air conditioning device for a vehicle. CONSTITUTION:A single temperature detecting means 100 for detecting a temperature around a cooling medium inflow part of an evaporator is provided, and a supply quantity of cooling medium to the evaporator is decreased by a freezing protective means 200 based on an output value of the temperature detecting means 100, so freezing is prevented. An average temperature at the evaporator is computed by an average temperature computing means 300 based on the output value of the temperature detecting means 100 and thermal load factors giving effects on heat exchanging conditions of the evaporator, and each air conditioning means is controlled by an air condition controlling means 400 considering the average temperature.

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 that detects the temperature of an evaporator and uses the detected value to prevent freezing of the evaporator and to control air conditioning equipment.

0002

2. Description of the Related Art It is known that a temperature sensor is provided to detect the temperature of an evaporator, and an air conditioner is controlled using the output value of the temperature sensor. For example, Tokuko Sho 62-2
Publication No. 5522 discloses a technology to turn off a compressor when the evaporator temperature falls below the freezing critical temperature, and Japanese Patent Application Laid-Open No. 2-109719 discloses a technology to control each air conditioner by taking the evaporator temperature into consideration. A technology has been disclosed that determines a comprehensive signal for controlling the vehicle interior and controls the temperature within the vehicle interior to a target temperature.

0003

[Problem to be solved by the invention] By the way, in order to maintain the function of the evaporator, it is necessary to give top priority to freezing prevention, and for this reason, it is recommended to install a temperature sensor in the part of the evaporator where the temperature is lowest. preferable.

However, in controlling the temperature of the evaporator and controlling the blowout temperature according to the heat exchange capacity of the heater unit, it is preferable to detect the average temperature of the evaporator in order to improve control accuracy. If a temperature sensor is installed at a location where it can detect the temperature, the air conditioning equipment will be controlled at a temperature lower than the actual average temperature of the evaporator, which has the disadvantage that the actual outlet temperature and evaporator temperature will deviate higher than the target temperature. there were.

[0005] In order to prevent this, it is necessary to place a
Although it is conceivable to provide a temperature sensor for each, the structure becomes complicated and costs increase.

[0006] Therefore, the present invention was made to eliminate the above-mentioned drawbacks, and uses one temperature sensor attached to the evaporator to prevent freezing, and at the same time, to control air conditioning equipment with high precision. The objective is to provide a vehicle air conditioner that can be controlled.

[0007]

[Means for Solving the Problems] As shown in FIG. 1, the gist of the present invention is to provide an evaporator temperature detection means for detecting the temperature of an evaporator, and an output of the evaporator temperature detection means to a predetermined temperature. a freeze protection means that reduces the amount of refrigerant supplied to the evaporator when The object of the present invention is to include an average temperature calculation means for calculating the average temperature calculation means, and an air conditioning control means for controlling each air conditioning device in consideration of the output of the average temperature calculation means.

[0008]

[Operation] Therefore, the evaporator temperature detection means 100
The temperature of the lowest temperature point of the evaporator is detected, and when this detected value becomes a predetermined temperature or less, the freeze protection means 200 reduces the amount of refrigerant supplied to the evaporator to prevent the evaporator from freezing. Further, the average temperature calculation means 300 corrects the output value of the evaporator temperature detection means 100 based on the heat load factor that affects the heat exchange state of the evaporator, and calculates the average temperature of the evaporator. Since the air conditioner is controlled by taking the average temperature into consideration, the same control as if a temperature sensor were provided to determine the average temperature of the evaporator is possible even without providing a separate temperature sensor.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

In FIG. 2, the vehicle air conditioner includes an inside/outside air switching device 2 provided at the most upstream side of the air conditioning duct 1.
In this internal/external air switching device 2, an internal/external air switching door 5 is arranged at a part where an internal air inlet 3 and an external air inlet 4 are separated, and the internal/external air is introduced into the air conditioning duct 1 by operating the internal/external air switching door 5 with an actuator 6. The intake mode can be changed by selecting between inside air and outside air.

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

The evaporator 8 is connected to the piping together with a compressor 10 having a variable capacity mechanism 24, a condenser 11, a liquid tank 12, and an expansion valve 13 to form a cooling cycle. They are connected via a clutch 15, and are controlled to be turned on and off by turning on and off the electromagnetic clutch 15. Further, the heater core 9 is configured to circulate engine cooling water and heat the air. An air mix door 16 is provided in front of the heater core 9, and by adjusting the opening degree of the air mix door 16 with an actuator 17, the amount of air passing through the heater core 9 and air bypassing the heater core 9 can be adjusted. is changed, and as a result, 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, which open into the vehicle interior 21, and mode doors 22a, 22b, and 22c are provided in these divided parts. By operating these mode doors 22a, 22b, and 22c with an actuator 23, a desired blowing mode can be obtained.

[0014] 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 (ROM).
), random access memory (RAM), input/output ports (I/O), etc., and the microcomputer 41 is equipped with a temperature sensor 43 that detects the temperature inside the vehicle interior 21. An output signal Tr, an output signal Ta from an outside air temperature sensor 44 that detects the outside air temperature, an output signal Qs from a solar radiation sensor 45 that detects the amount of solar radiation, and are provided at a low temperature location of the evaporator 8 to detect the temperature of the location. Output signal T from evaporator temperature sensor 46
E is selected via multiplexer 47 and A/D
The signal is converted into a digital signal by a converter 48 and input.

The evaporator temperature sensor 46 is provided at or near the lowest temperature part of the evaporator 8 in order to prevent the evaporator 8 from freezing. It is desirable to install it on the piping between the refrigerant inlet, at a location where the temperature of the air near the refrigerant inlet on the downstream side of the evaporator can be detected, or between the fins.

Further, an output signal from the operation panel 25 is input to the microcomputer 41 . This operation panel 25 includes a blowout mode setting device 2 that sets a blowout mode other than the defrost mode by operating a MODE switch 26a.
6. Air blowing capacity setting device 27 that sets the air blowing capacity by operating the FAN switch 27a, up/down switches 28a, 2
The display section 30, which is connected to the microcomputer 41 via the display circuit 29, displays the blowout mode,
The air blowing capacity and set temperature are displayed.

The operation panel 25 also includes an AUTO switch 31 that sets the air conditioner to automatic control mode, an OFF switch 32 that stops the operation of the air conditioner, a REC switch 33 that sets the suction mode, and a blowout mode that sets the defrost mode. DEF switch 34, compressor 1
0 operation, and an AMB switch 36 that commands the outside temperature to be displayed on the display section.

FIG. 3 shows a functional block diagram showing a specific example of control of the air conditioner in this embodiment, and this will be explained prior to explaining an example of the control operation by the microcomputer 31 mentioned above.

The temperature TE detected by the evaporator temperature sensor 46 is the temperature of the lowest temperature point of the evaporator 8, and if this temperature TE falls below the limit temperature at which freezing will not occur, the temperature will gradually freeze starting from the lowest temperature point. Based on this TE, the presence or absence of freezing is determined (201), and if the temperature is lower than the freezing critical temperature, the electromagnetic clutch 15 of the compressor 10 is turned off.

Furthermore, the average temperature TEAV of the evaporator is calculated based on the TE, the outside air temperature Ta, and the target air volume V' to be described later (301). This average temperature TE
Although the method for calculating AV will be described in detail later, this average temperature is used to control each air conditioning device that determines the air conditioning state.

First, the outside 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 TD set by the temperature setting device,
and the average temperature TEAV, calculate the overall signal T used to determine the target control amount of the air conditioning equipment (4
01).

From this total signal T, a target temperature TE' of the evaporator is calculated (402), and the compressor 10 is adjusted so that the difference from the TEAV is less than or equal to a predetermined amount (α).
The variable capacity mechanism 24 is operated to control the discharge capacity of the compressor (403).

[0024] Also, from the general signal T, the air mix door 1
The target opening degree (Θ') of the air mix door 16 is calculated (404), and the target opening degree (Θ') and the actual opening degree (Θ) of the air mix door 16 are calculated (404).
The position of the air mix door 16 is controlled such that the difference from

Furthermore, based on the overall signal T, the target air volume is calculated as the target applied voltage (V') to the blower motor (
406), the control amount of the power transistor (408) is adjusted to control the air volume so that the difference between this target applied voltage (V') and the actual voltage across the blower motor (V) is within a predetermined amount (γ). (407).

Next, an example of the operation of the microcomputer 41 will be explained based on the flowchart shown in FIG. , output signals from each sensor are input, and in step 52, a switch signal from the operation panel 25 is input.

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

[0028]

[Math. 1] T=Tr +A・Ta +B・TEAV −C・TD
+D

[0029] Here, A, B, and C are constants calculated experimentally, and D is a correction term.

After the total signal T is calculated, step 5
4, the air mix door 16 described above is controlled. Here, the target opening degree (Θ') of the air mix door 16 is calculated so as to obtain a characteristic that is approximately proportional to the magnitude of the total signal T, as shown in FIG. 5, for example.

In the next step 55, blower control as shown in FIG. 6 is performed. To explain this specifically, in step 58, it is determined whether or not there is a request to stop (OFF) the fan (FAN), and in step 59, when the FAN switch 27a is pressed, the fan (FAN) is turned off.
N) respectively determine whether there is a request for manual mode, and if there is a request to stop the blower 7, step 6
0, the blower is stopped, and if there is a request for the manual mode of the blower 7, the process proceeds to step 61, where the blower 7 is manually controlled. If there is no request, the process proceeds to step 62, where blower control is performed in conjunction with the calculation of the target air volume described above. 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, the compressor 10 is controlled as shown in FIG.

In this control, it is determined in step 63 whether or not there is a request to stop (OFF) the fan (FAN), and in step 64 it is determined whether or not the A/C switch 35 is turned on. If there is a request to stop the compressor 10 or if the A/C switch 35 is not turned on, the process advances to step 65 and the compressor 10 is stopped (turned OFF). In contrast, there was no request to stop the blower 7, and A/
If the C switch 35 is turned on, step 6
6, the temperature TE detected by the evaporator temperature sensor 46 is set to a predetermined freezing critical temperature (for example, 0.
If the temperature is below the freezing critical temperature, the process proceeds to step 65 and the compressor 10 is stopped (OFF) in order to prevent the evaporator 8 from freezing. If the freezing critical temperature has not been reached, the process proceeds to step 67 and the compressor 10 is activated (
ON), and in steps 68 to 70, the compressor control described above is performed.

That is, in step 68, a target temperature TE' of the evaporator is calculated from the overall signal T so that the characteristics shown in the same step are obtained, and in step 70, this target temperature TE' is calculated in step 69. The capacity of the compressor 10 is controlled such that the difference from the average temperature TEAV of the evaporator 8 is, for example, within 1°C.

FIG. 8 specifically shows an example of calculating the average temperature TEAV of the evaporator 10 in step 69. In step 71, the temperature TE detected by the evaporator temperature sensor 46, the outside air temperature Ta, and the above-mentioned The target air volume V' is input, and in step 72 it is determined whether the outside air temperature belongs to a low outside air area (A), an intermediate outside air area (B), or a high outside air area (C).

[0036] Then, in steps 73 and 74,
The area determined in the previous step 72 is determined, and if it is determined that it belongs to the low outside air area (A), step 7
5, it is determined whether the target air volume V' is larger than the predetermined air volume K1.

When the outside temperature is low and the air volume is small, the heat load on the evaporator 8 is small and the amount of refrigerant flowing inside the evaporator is small, so the liquid refrigerant only flows properly near the refrigerant inlet. The difference between the temperature TE detected by the evaporator temperature sensor 46 and the average temperature of the evaporator 8 increases. On the other hand, when the outside temperature is low but the air volume is large, the heat load on the evaporator 8 becomes large and the amount of refrigerant flowing inside the evaporator increases, so that the temperature is detected by the evaporator temperature sensor 46 near the refrigerant inlet. The difference between the temperature TE and the average temperature of the evaporator becomes smaller. Therefore, in order to calculate TEAV based on TE, TE and TEA
It is necessary to consider the size of the difference between the target air volume V
' is smaller than the predetermined air volume K1, TE and TEA
The correction amount (α) corresponding to the difference from V is set to a large value α1 (step 76), and if V' is larger than K1,
Set the correction amount (α) to a small value α2 (α1 > α2 > 0)
(Step 77).

If it is determined that the outside air temperature Ta belongs to the high outside air region (C), the process proceeds to step 78, where it is determined whether the target air volume V' is larger than the predetermined air volume K2.

When the outside temperature is high and the air volume is large, the heat load on the evaporator 8 is large, and the amount of refrigerant flowing through the evaporator increases, but the large amount of heat exchange increases the degree of superheating, and the refrigerant inlet The difference between the temperature TE detected by the nearby evaporator temperature sensor 46 and the average temperature TEAV of the evaporator increases. On the contrary,
When the outside temperature is high but the air volume is small, the heat load on the evaporator 8 becomes small and the degree of superheating becomes small, causing a difference between the temperature TE detected by the evaporator temperature sensor 46 near the refrigerant inlet and the evaporator average temperature TEAV. The difference becomes smaller. Therefore, based on TE, TEA
To calculate V, if the target air volume V' is larger than the predetermined air volume K2, the correction amount (α) corresponding to the difference between TE and TEAV is set to a large value α3 (step 79), and V
' is smaller than K2, the correction amount (α) is set to a smaller value α
4 (α3 > α4 > 0) (step 80).

On the other hand, if it is determined that the outside air temperature Ta belongs to the intermediate outside air region (B), the heat load on the evaporator 8 is not so high and the refrigerant is circulating throughout the evaporator. , the temperature T detected by the evaporator temperature sensor 46 near the refrigerant inlet
There is almost no difference between E and the average temperature TEAV of the evaporator 8. Therefore, the correction amount (α) corresponding to the difference between TE and TEAV is set to zero (step 81).

The above correction amount (α) is determined in advance experimentally, and after the correction amount (α) is determined,
Proceeding to step 82, the average temperature TEAV of the evaporator is calculated as the sum of TE and α, as shown in equation (2).

[0042]

[Math 2] TEAV = TE + α

In this embodiment, only examples of control operations for the air mix door, blower, and compressor among the air conditioning equipment are shown, but the main routine also includes control operations for other air conditioning equipment, such as the intake device and mode. A step 57 for controlling doors and the like may be added, and the driving of these air conditioners may also be controlled based on the comprehensive signal T that takes TEAV into consideration.

[0044]

[Effects of the Invention] As described above, according to the present invention,
The temperature of the lowest temperature 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 heat load factors that affect the heat exchange state of the evaporator. By doing so, each temperature sensor can be obtained, so that freezing can be prevented using one temperature sensor without providing two temperature sensors in the evaporator, and the air conditioning equipment can be controlled with high precision.

[Brief explanation of the drawing]

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.

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

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

FIG. 5 is a characteristic diagram showing the relationship between the total signal (T) and the target opening degree (Θ') of the air mix door.

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

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

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

[Explanation of symbols]

100 Evaporator temperature detection means 200 Freeze protection measures 300 Average temperature calculation means 400 Air conditioning control means

Claims (1)

[Claims] 1. Evaporator temperature detection means for detecting the temperature of the evaporator; freeze protection means for reducing the amount of refrigerant supplied to the evaporator when the output of the evaporator temperature detection means is below a predetermined temperature; average temperature calculation means for calculating the average temperature of the evaporator based on the output value of the detection means and heat load factors that affect the heat exchange state of the evaporator; An air conditioning system for a vehicle, comprising an air conditioning control means for controlling the air conditioning system.