Vehicle air conditioning system

Abstract

To provide a vehicle air conditioner which can inhibit erroneous judgment of frost formation to achieve high performance.SOLUTION: A vehicle air conditioner includes: an outdoor heat exchanger 11 which exchanges heat with outside air; a compressor 13 which compresses a refrigerant; an outside air temperature sensor 21 configured to detect an outside air temperature Ta; a refrigerant temperature sensor 22 configured to detect a refrigerant outlet temperature Tr which is an outlet temperature of the refrigerant in the outdoor heat exchanger 11; and a determination part 23 which determines whether or not frost is formed on the outdoor heat exchanger 11 based on a temperature difference ΔT between the detected outside air temperature Ta and the refrigerant outlet temperature Tr. The determination part 23 adds a correction value C set according to a rotation number R of the compressor 13 to the temperature difference ΔT to determine whether or not frost is formed.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD

[0001] The present invention relates to a vehicle air conditioner.

BACKGROUND ART

[0002] Patent Document 1 discloses an in-vehicle air conditioner that determines that frost formation has occurred on an outdoor heat exchanger based on the elapsed time of a state where the temperature difference between the refrigerant in the refrigerant flow path on the outlet side of the outdoor heat exchanger and the outside air is equal to or greater than a frost formation temperature difference at which frost formation can occur on the outdoor heat exchanger.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] However, since the refrigerant temperature on the outlet side of the outdoor heat exchanger also depends on the rotational speed of the compressor, the in-vehicle air conditioner described in Patent Document 1 may erroneously determine that frost has formed when the rotational speed of the compressor instantaneously increases, leading to a risk of reduced heating capacity.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vehicle air conditioner that can suppress erroneous determination of frost formation and exhibit high performance.

MEANS FOR SOLVING THE PROBLEMS

[0006] To achieve the above object, the vehicle air conditioner of the present invention includes: an outdoor heat exchanger that performs heat exchange with outside air; a compressor that compresses refrigerant; an outside air temperature sensor that detects the outside air temperature; a refrigerant temperature sensor that detects a refrigerant outlet temperature, which is the outlet temperature of the refrigerant in the outdoor heat exchanger; A determination unit that determines whether or not frost has formed on the outdoor heat exchanger based on the temperature difference between the detected outside temperature and the refrigerant outlet temperature, Equipped with, The determination unit adds a correction value corresponding to the rotation speed of the compressor to the temperature difference to determine whether or not frost has formed.

[0007] With this configuration of vehicle air conditioning system, by adding a correction value corresponding to the compressor rotation speed to the temperature difference between the outside temperature and the refrigerant outlet temperature used to determine the presence or absence of frost, it is possible to suppress misjudgment of frost formation due to instantaneous increases in the compressor rotation speed and to suppress a decrease in heating capacity. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a vehicle air conditioning system that can suppress misjudgment of frost formation and exhibit high performance. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of the vehicle air conditioning system according to this embodiment. [Figure 2] Figure 2 is a graph illustrating general frost detection criteria. [Figure 3] Figure 3 is a graph illustrating the frost determination method according to the present invention. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 is a schematic diagram of the vehicle air conditioning system 10 according to this embodiment.

[0011] As shown in Figure 1, the vehicle air conditioning system 10 according to this embodiment includes, as an example, an outdoor heat exchanger 11, an evaporator 12, a compressor 13, and an expansion valve 14. The outdoor heat exchanger 11 and the evaporator 12 are connected by piping 15, and refrigerant is circulated through piping 15. The compressor 13 is provided in one of the pipes 15, and the expansion valve 14 is provided in the other pipe 15.

[0012] The outdoor heat exchanger 11 is a condenser located outside the vehicle, and the refrigerant exchanges heat with the outside air through this outdoor heat exchanger 11. The outdoor heat exchanger 11 is equipped with a fan 11a, and the efficiency of heat exchange in the outdoor heat exchanger 11 is increased by the blowing of outside air by this fan 11a. The evaporator 12 is located inside the vehicle, and the refrigerant exchanges heat with the indoor air through this evaporator 12. The evaporator 12 is equipped with a blower 12a, and the air that has undergone heat exchange in the evaporator 12 is sent into the interior by the blower 12a.

[0013] During cooling operation, in the vehicle air conditioning system 10, the refrigerant, which has been compressed and liquefied by the compressor 13, is cooled by heat exchange with the outside air in the outdoor heat exchanger 11. The refrigerant cooled in the outdoor heat exchanger 11 is then expanded and vaporized in the expansion valve 14 and sent to the evaporator 12. As a result, the room air is cooled in the evaporator 12 by the latent heat of vaporization of the refrigerant, and the cool air is sent into the room by the blower 12a.

[0014] During heating operation, in the vehicle air conditioning system 10, the refrigerant, which has been expanded by the expansion valve 14 and cooled to a low temperature, is heated by heat exchange in the outdoor heat exchanger 11. The refrigerant that has passed through the outdoor heat exchanger 11 is then compressed and liquefied by the compressor 13, becoming hot, and sent to the evaporator 12. As a result, the air in the evaporator 12 is heated, and this heated air is then sent into the room as warm air by the blower 12a.

[0015] The vehicle air conditioning device 10 having the above configuration includes an outside air temperature sensor 21, a refrigerant temperature sensor 22, and a determination unit 23.

[0016] The outside air temperature sensor 21 detects an outside air temperature Ta, and is arranged outside the vehicle compartment. The refrigerant temperature sensor 22 detects a refrigerant outlet temperature Tr, which is the outlet temperature of the refrigerant in the outdoor heat exchanger 11.

[0017] The determination unit 23 determines the presence or absence of frost formation on the outdoor heat exchanger 11 of the vehicle air conditioning device 10. The outside air temperature sensor 21 is connected to this determination unit 23, and a detection signal of the outside air temperature Ta is transmitted from the outside air temperature sensor 21. Further, the refrigerant temperature sensor 22 is connected to the determination unit 23, and a detection signal of the refrigerant outlet temperature Tr is transmitted from the refrigerant temperature sensor 22. Furthermore, the compressor 13 is connected to the determination unit 23, and data on the rotation speed R of this compressor 13 is transmitted thereto.

[0018] The determination unit 23 determines the presence or absence of frost formation during heating operation, based on the detection signal of the outside air temperature Ta, the detection signal of the refrigerant outlet temperature Tr, and the data of the rotation speed R of the compressor 13, which are transmitted from the outside air temperature sensor 21, the refrigerant temperature sensor 22, and the compressor 13.

[0019] Incidentally, frost formation during heating operation occurs as the temperature difference ΔT (ΔT=Ta-Tr) between the outside air temperature Ta and the refrigerant outlet temperature Tr increases. That is, it is considered that frost formation progresses as this temperature difference ΔT increases. Therefore, by monitoring the temperature difference ΔT between the outside air temperature Ta and the refrigerant outlet temperature Tr, the presence or absence of frost formation can be determined.

[0020] Figure 2 is a graph for describing a general frost formation determination that is made based on the temperature difference ΔT between the outside air temperature Ta and the refrigerant outlet temperature Tr.

[0021] In a general determination of whether or not frost has formed based on the ambient temperature Ta and the refrigerant outlet temperature Tr, frost is determined to have formed when the temperature difference ΔT between the ambient temperature Ta obtained from the ambient temperature sensor 22 and the refrigerant outlet temperature Tr obtained from the refrigerant temperature sensor 22 exceeds a preset threshold Th (see the graph of ΔT in Figure 2).

[0022] Incidentally, the temperature difference ΔT between the ambient temperature Ta and the refrigerant outlet temperature Tr fluctuates depending on the operating state of the compressor 13 (see the graph of compressor rotation speed R in Figure 2). Specifically, the refrigerant outlet temperature Tr fluctuates along with the fluctuations in the rotation speed R of the compressor 13, and the temperature difference ΔT between the ambient temperature Ta and the refrigerant outlet temperature Tr fluctuates similarly. Therefore, when the rotation speed R of the compressor 13 increases and the refrigerant outlet temperature Tr decreases, the temperature difference ΔT between the ambient temperature Ta and the refrigerant outlet temperature Tr temporarily increases and exceeds the threshold Th (at timing t in Figure 2), it may be mistakenly determined that frost has formed on the outdoor heat exchanger 11, even though there is actually no frost.

[0023] After misjudging the occurrence of frost, the rotation speed R of the compressor 13 is reduced to suppress the progression of frost (see the graph of compressor rotation speed R in Figure 2). As a result, reducing the rotation speed R of the compressor 13 reduces the heating capacity after the timing t in which frost was detected (see the graph of heating capacity in Figure 2). Furthermore, as the rotation speed R of the compressor 13 decreases, the frost rate after the timing t in which frost was detected is suppressed more than necessary (see the graph of frost rate in Figure 2).

[0024] To avoid such misjudgments of frost formation, the determination unit 23 in this invention makes the determination as follows. Figure 3 is a graph illustrating the frost determination method according to the present invention.

[0025] First, the temperature difference ΔT between the ambient temperature Ta obtained from the ambient temperature sensor 22 and the refrigerant outlet temperature Tr obtained from the refrigerant temperature sensor 22 is calculated.

[0026] Furthermore, a correction value C is determined to compensate for this temperature difference ΔT. This correction value C is derived from the rotational speed R of the compressor 13 and is calculated by the following equation (1) where A is a constant.

[0027] C = A × R …(1)

[0028] Then, the added value obtained by adding this correction value C to the temperature difference ΔT is defined as the determination value ΔT+C, and this determination value ΔT+C is compared with a preset threshold Th (see the graph of ΔT+C in Figure 3). When this added value ΔT+C exceeds the preset threshold Th, it is determined that frost has formed on the outdoor heat exchanger 11.

[0029] Thus, by determining frost formation while considering the correction value C derived from the rotational speed R of the compressor 13, fluctuations in the determination value ΔT+C for determining frost formation can be suppressed even if the rotational speed R of the compressor 13 fluctuates (see the graph of compressor rotational speed R in Figure 3) (see the graph of ΔT+C in Figure 3).

[0030] Therefore, misjudgments of frost formation due to instantaneous increases in the rotational speed R of the compressor 13 are suppressed, and a decrease in heating capacity can be prevented (see the graph of heating capacity in Figure 3). In this case, since the heating capacity is maintained, the frost rate gradually increases until the judgment value ΔT+C exceeds the threshold Th (see the graph of frost rate in Figure 3).

[0031] As described above, according to the vehicle air conditioning system 10 of this embodiment, by adding a correction value C corresponding to the rotation speed R of the compressor 13 to the temperature difference ΔT between the outside temperature Ta and the refrigerant outlet temperature Tr used to determine the presence or absence of frost, it is possible to suppress misjudgment of frost formation due to a momentary increase in the rotation speed R of the compressor 13 and suppress a decrease in heating capacity. [Explanation of Symbols]

[0032] 10. Vehicle air conditioning system 11 Outdoor heat exchanger 13 Compressor 21 Outdoor temperature sensor 22 Refrigerant temperature sensor 23 Judgment section C Correction Value R rotation speed Ta outside temperature Tr Refrigerant outlet temperature ΔT temperature difference

Claims

[Claim 1] An outdoor heat exchanger that exchanges heat with the outside air, A compressor that compresses the refrigerant, An ambient temperature sensor that detects the ambient temperature Ta, A refrigerant temperature sensor detects the refrigerant outlet temperature Tr, which is the outlet temperature of the refrigerant in the outdoor heat exchanger. A determination unit that determines whether or not frost has formed on the outdoor heat exchanger based on the temperature difference ΔT between the detected outside temperature Ta and the refrigerant outlet temperature Tr, Equipped with, The determination unit determines the presence or absence of frost formation using a determination value ΔT+C, which is obtained by adding a correction value C corresponding to the rotation speed R of the compressor to the temperature difference ΔT. The correction value C is calculated using the negative constant A as A × R. Vehicle air conditioning system.

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