JPH04237625A - Air conditioner for vehicle - Google Patents

Abstract

PURPOSE:To improve the stability of blow-off air temperature without reheating. CONSTITUTION:A hydraulic motor 5 serving as the drive source of a refrigerant compressor 4, and a variable displacement hydraulic pump 6 variable in displacement through a control part 7 are provided as the driving means of a refrigerating cycle 2 so as to make the rotating speed of the refrigerant compressor 4 variable. The control part 7 controls the displacement of the hydraulic pump 6 with the required rotating speed Nc of the refrigerant compressor 4 computed by a microcomputer 8 as the command value. The required rotating speed Nc of the refrigerant compressor 4 is determined by a primary polynominal formed of the required blow-off temperature computed on the basis of the set interior temperature, the interior temperature, the outside air temperature, the quantity of solar radiation, and the like, and the sucked air temperature and sucked air humidity of a refrigerant evaporator 13.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for a vehicle that can continuously change its cooling capacity. [0002] Conventionally, vehicle air conditioners have generally adopted an air mix system in which cold air and warm air are mixed and blown out by controlling the opening and closing of an air mix damper. However, with this method, the air that has been cooled is heated again (
reheating), which requires more power from the refrigerant compressor than necessary. [0003] Therefore, a hydraulically driven air conditioner has been proposed that uses a hydraulic motor as the drive source of the refrigerant compressor and makes the rotational speed of the refrigerant compressor variable, thereby controlling the temperature of the blown air without reheating. has been done. [0004] Problems to be Solved by the Invention [0004] In this system, a method can be considered in which the temperature of the blown air is controlled to a target blown air temperature that is determined according to the set temperature, heat load, etc. However, the response delay of the refrigeration cycle Therefore, when the temperature of the blown air is detected and the rotational speed of the refrigerant compressor is feedback-controlled so as to reach the target blown air temperature, the response of the blown air temperature becomes more unstable than in the air mix method. The present invention has been made based on the above circumstances, and its object is to provide an air conditioner for a vehicle that improves the stability of the temperature of the blown air without requiring reheating. . Means for Solving the Problems In order to achieve the above object, the present invention provides a vehicle air conditioner in which the cooling capacity can be continuously changed by varying the rotational speed or capacity of the refrigerant compressor. In the apparatus, the refrigerant compressor has a rotation speed or a capacity that is determined based on the required blowout temperature calculated based on the set temperature, the vehicle interior temperature, the outside air temperature, and the amount of solar radiation, and the suction air temperature and suction air of the refrigerant evaporator. The technical means is to be determined by a first-order polynomial consisting of humidity. [Embodiment] Next, an air conditioner for a vehicle according to the present invention will be explained based on an embodiment shown in the drawings. FIG. 1 is an overall configuration diagram of a vehicle air conditioner. The air conditioner 1 of this embodiment includes a hydraulic circuit 3 as driving means for the refrigeration cycle 2. Hydraulic circuit 3
consists of a hydraulic motor 5 that drives a refrigerant compressor 4 of a refrigeration cycle 2, and a hydraulic pump 6 that is driven by an on-vehicle engine (not shown). The hydraulic pump 6 is a variable displacement pump whose displacement is variable via the control section 7. The control unit 7 controls the capacity of the hydraulic pump 6 based on the command value output from the microcomputer 8. [0009] In addition to the refrigerant compressor 4, the refrigeration cycle 2 includes:
It has a well-known structure including a refrigerant condenser 9, a receiver 10, an expansion valve 11, and a refrigerant evaporator 13 housed in a blower duct 12, and these functional parts are connected in a ring shape by a refrigerant pipe 14. [0010] Upstream of the blower duct 12, an outside air inlet 16 and an inside air inlet 17 are provided, which are selected by an inside/outside air switching damper 15, and downstream of the blower duct 12, an outside air inlet 16 and an inside air inlet 17 are provided for blowing the air into the vehicle interior. Each air outlet (not shown)
is provided. A blower 18 is disposed inside the blower duct 12 to generate an air flow toward the vehicle interior. When the blower 18 operates, the air introduced from the outside air inlet 16 or the inside air inlet 17 is transferred to the refrigerant evaporator. After the heat is exchanged in step 13, the air is blown out into the vehicle interior from the selected air outlet. The microcomputer 8 includes an outside air sensor 19, a room temperature sensor 20, a solar radiation sensor 21, a temperature setting device 22 for setting a target temperature inside the vehicle, and an inside/outside air switching damper 1.
A command value to be output to the control unit 7 is calculated based on output signals from a damper position sensor 23 that detects the position of 5 and a humidity sensor 24 that detects the humidity of the air sucked into the refrigerant evaporator 13. The operation of the microcomputer 8 will now be explained based on the flowchart shown in FIG. First, in step S1, output signals from each sensor (outside air sensor 1
outside air temperature Tam from 9, solar radiation ST from solar radiation sensor 21, room temperature Tr from room temperature sensor 20, temperature setting device 2
Target set temperature Tset from 2, damper position sensor 23
The damper position IO from the humidity sensor 24 and the suction air humidity Hin from the humidity sensor 24 are input. [0013] Next, in step S2, based on the data indicating the environmental conditions in the vehicle interior, the air flow from the ventilation duct 12 necessary to bring the temperature in the vehicle interior closer to and maintain the set target temperature is determined. The required blowout temperature Tao is calculated using the following formula. Tao = Kset・Tset−Kr・Tr−Ks・S
T+C (Kset, Kr, Ks, C are constants determined in advance experimentally based on the heat load balance) [0014] After that, the process proceeds to step S3, and the suction air temperature Tin of the refrigerant evaporator 13 is calculated using the following equation. Tin = IO・Tam +Tr(1-IO) 001
5] Tin in the above equation is given as a function of the damper position IO, and in the internal air mode, when IO=0, Ti
n = Tr, when in outside air mode, IO = 1 and Tin = T
It becomes am. Note that a temperature sensor for detecting the suction air temperature of the refrigerant evaporator 13 may be added, and the suction air temperature Tin, which is the output signal of the temperature sensor, may be directly taken in in step S1. In that case, damper position sensor 2
3 becomes unnecessary. Next, in step S4, the necessary blowing temperature Ta
The required rotational speed Nc of the refrigerant compressor 4 to realize o is calculated using the following formula. Nc=C1+C2・Tao +C3・Tin +C4・
Hin Note that C1, C2, C3, and C4 are constants, which are determined using Chebyshev's orthogonal polynomial. C
1 is a constant, and C2, C3, and C4 are constants representing the change in rotation speed, that is, the slope, with respect to the factor change in each factor. [0018] Then, the process advances to step S5, and step S
The Nc calculated in step 4 is output to the control unit 7 as a command value. The control unit 7 controls the capacity of the hydraulic pump 6 based on this command value. Here, the procedure for calculating the required rotational speed Nc will be explained based on FIG. 3. First, extract the factors that affect the rotation speed, and within the range that the factors can take,
We investigated the required rotation speed determined by the combination of each factor. As a result of analyzing them using the experimental design method, as shown in Fig. 3, the first-order terms of the three factors, suction air temperature Tin, suction air humidity Hin, and required blowout temperature Tao, govern the change in rotation speed. It became clear that it would be best to incorporate them into the rotation speed control formula. Note that the suction air temperature and the suction air humidity give the suction air enthalpy, that is, the heat load, and the required blowing temperature gives the blowing air enthalpy. In addition, it was found that the number of revolutions required to give the same temperature of the blown air changes greatly depending on the humidity of the suction air. Therefore, in this system, which controls the temperature of the blown air without reheating, the number of revolutions is determined by detecting the humidity. It is included in the control formula. Next, the operation of this embodiment will be explained. After starting up the refrigeration cycle 2, the required rotation speed Nc is calculated by the microcomputer 8 based on output signals from various sensors. This required rotation speed Nc is used as a command value by the control unit 7.
The displacement of the hydraulic pump 6 is controlled by the control unit 7. As a result, the amount of oil supplied from the hydraulic pump 6 to the hydraulic motor 5 changes, and the rotation speed of the hydraulic motor 5 changes, so that the rotation speed of the refrigerant compressor 4 changes to the required rotation speed calculated by the microcomputer 8. It is controlled so that the number Nc. [0021] Here, the room temperature controllability during sudden changes in solar radiation is shown in Figure 4.
Shown below. In addition, in FIG. 4, the measurement results of this example are shown by a solid line a, and the measurement results by the current air mix damper are shown by a broken line b, and the measurement results are shown by a feedback control method in which the blowout temperature is feedback-controlled to the target required blowout temperature. is shown by a dashed line c. From this measurement result, in the air conditioner 1 of this example, there was no significant initial rise in room temperature;
There is no deviation in the steady room temperature (approximately 23 degrees here) after correcting for changes in thermal sensation due to solar radiation. There is a slight delay in the room temperature drop during the transition, but it is at a level that poses no problem. On the other hand, in the feedback control method, in order to control the steady room temperature without deviation, the initial room temperature fluctuates significantly, causing a problem in terms of feeling. As described above, the air conditioner 1 of this embodiment controls the capacity of the hydraulic pump 6 and makes the rotational speed of the refrigerant compressor 4 variable, thereby controlling the temperature of the blown air without reheating. It is possible. The rotational speed of the refrigerant compressor 4 is determined based on the required blowout temperature calculated based on the set temperature, vehicle interior temperature, outside air temperature, amount of solar radiation, etc., and the suction air temperature and suction air humidity of the refrigerant evaporator 13. By being given by a first-order polynomial, the stability of the blowing temperature can be improved. Note that the rotation speed control formula for calculating the required rotation speed Nc is based on the required blowout temperature Tao and the refrigerant evaporator 13.
It is given by the linear terms of the suction air temperature Tin and the suction air humidity Hin, but it may also be determined by the following equation including the outside air temperature Tam. Nc=C1+C2・Tao +C3・Tin +C
4・Hin +C5・Tam (C1 to C5: constant) [
Next, a second embodiment of the present invention will be explained. Figure 5
1 is an overall configuration diagram of a vehicle air conditioner 1. FIG. The air conditioner 1 of this embodiment uses a variable capacity refrigerant compressor 4. In the first embodiment, the refrigerant compressor 4 with a fixed capacity was used to calculate the required number of revolutions of the refrigerant compressor 4, but in the refrigerant compressor 4 of this embodiment, both the number of revolutions and the capacity change. Therefore, for example, a rotation speed sensor 25 is added to adjust the rotation of the refrigerant compressor 4 so that the value of (rotation speed x fixed capacity) in the first embodiment becomes equal to the value of (rotation speed x variable capacity). All you have to do is detect the number and change the capacity. [0026] As explained above, according to the present invention,
The temperature of the blown air can be controlled without reheating, and the stability of the blown air temperature can be improved, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a vehicle air conditioner according to a first embodiment.

FIG. 2 is a flowchart showing the operation of the microcomputer.

FIG. 3 is a diagram showing analysis results of various factors that affect the rotation speed.

FIG. 4 is a measurement result of room temperature controllability during sudden changes in solar radiation.

FIG. 5 is an overall configuration diagram of a vehicle air conditioner in a second embodiment.

[Explanation of symbols]

1 Vehicle air conditioner 4 Refrigerant compressor 13 Refrigerant evaporator

Claims (1)

[Claims] Claims: 1. A vehicle air conditioner in which the cooling capacity can be continuously changed by varying the rotation speed or capacity of a refrigerant compressor, wherein the rotation speed or capacity of the refrigerant compressor varies depending on the set temperature; A vehicle air conditioner characterized in that the air conditioner is determined by a first-order polynomial consisting of a required blowout temperature calculated based on a vehicle interior temperature, an outside air temperature, and an amount of solar radiation, and a refrigerant evaporator suction air temperature and suction air humidity. Device.