Vehicle air conditioning system

Abstract

To realize a vehicle air conditioner which prevents the generation of coolant flow noise.SOLUTION: A vehicle air conditioner comprises: a control section 12 which controls air-conditioning in a vehicle; an evaporator 14; a compressor 16; a condenser 18; coolant piping 20 which serves as a flow passage for circulating coolant and connects the evaporator 14, the compressor 16, and the condenser 18; and an expansion valve 22 which is installed on a passage constituting the coolant piping 20 and connecting the condenser 18 and the evaporator 14. The control section 12 operates so as to concentrate air conditioning on a specific vehicle seat and to increase the number of air outlets that discharge conditioned air into the vehicle interior when an air-conditioning load is equal to or below a predetermined value.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Vehicles are equipped with air conditioners that control the environment inside the vehicle, such as the temperature. Conventionally, technologies related to air conditioners suitable for each purpose, such as improving fuel efficiency and improving the comfort inside the vehicle, have been proposed.

[0003] For example, the vehicle air conditioner disclosed in Patent Document 1 can reduce the load on the air conditioner by performing air conditioning control according to the presence or absence of passengers other than the driver's seat, or can provide effective air conditioning for both when the temperature sensations of the passengers in the driver's seat and other seats are different.

[0004] Also, Patent Document 2 discloses a vehicle air conditioner aimed at suppressing the generation of noise. This vehicle air conditioner can suppress the generation of refrigerant passing sound and compressor suction pulsation sound in the refrigeration cycle device by acquiring the load amount of the refrigeration cycle device and switching the control method of the compressor based on this load amount.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, when the load on the air conditioning system decreases, the refrigerant noise—the sound of refrigerant circulating within the system—becomes louder, which can impair comfort inside the vehicle. This is thought to be because the reduced load on the air conditioning system leads to insufficient evaporation of the refrigerant in the evaporator.

[0007] Therefore, this specification aims to realize a vehicle air conditioning system that suppresses the generation of refrigerant passage noise. [Means for solving the problem]

[0008] The vehicle air conditioning system disclosed herein comprises a control unit for controlling the vehicle's air conditioning, an evaporator, a compressor, a condenser, a refrigerant piping which is a flow path for circulating refrigerant and which connects the evaporator, the compressor, and the condenser, and an expansion valve provided on the path connecting the condenser and the evaporator in the refrigerant piping, wherein the control unit operates to concentrate the air conditioning on one seat in the passenger compartment, and controls the number of outlets for air conditioning air blown into the passenger compartment when the load of the air conditioning is below a predetermined value. [Effects of the Invention]

[0009] According to the vehicle air conditioning system disclosed herein, the load on the air conditioning system is increased by increasing the number of air outlets that blow conditioned air into the passenger compartment under certain conditions. As a result, the generation of refrigerant flow noise, which is likely to occur when the load on the air conditioning system is low, can be suppressed. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of the vehicle's air conditioning system. [Figure 2] This graph shows the state of the refrigerant in a vehicle's air conditioning system when it is under low load. [Figure 3] This flowchart shows an example of processing in a vehicle's air conditioning system. [Modes for carrying out the invention]

[0011] The vehicle's air conditioning system will be described below with reference to the diagrams.

[0012] Figure 1 is a schematic diagram of the vehicle's air conditioning system. More specifically, Figure 1 is a schematic front-view perspective of the vehicle showing an example of the configuration of the vehicle's air conditioning system 10 disclosed herein. As shown in Figure 1, the vehicle's air conditioning system 10 comprises a control unit 12, an evaporator 14, a compressor 16, a condenser 18, refrigerant piping 20, and an expansion valve 22. In this example, the vehicle's air conditioning system 10 uses sensors to detect the presence or absence of occupants in each seat, such as the driver's seat and passenger seat, and the front and rear seats, and controls the air conditioning in the vehicle cabin. This airflow control technology is called S-Flow (Save energy + airflow control).

[0013] The control unit 12 is an electronic control unit that includes at least a CPU for performing various calculations and a memory for storing control programs and data. For example, the control unit 12 controls the air conditioning system 10, controlling the temperature of the conditioned air blown into the vehicle cabin from the air conditioning system 10, and controlling the position of the air conditioning outlet. The control unit 12 also controls the operation of each part of the air conditioning system 10. In Figure 1, each part controlled by the control unit 12 is shown enclosed by a dashed line.

[0014] The evaporator 14 is a device that changes the state of the refrigerant circulating within the air conditioning unit 10 from a liquid state (hereinafter referred to as "liquid-phase refrigerant") to a gaseous state (hereinafter referred to as "gas-phase refrigerant"). In other words, the evaporator 14 is a heat exchanger that evaporates the refrigerant circulating within the air conditioning unit 10 and removes heat from its surroundings.

[0015] The compressor 16 is a device connected to the evaporator 14 via refrigerant piping 20. The compressor 16 draws in the low-pressure, low-temperature gas after evaporation in the evaporator 14, compresses it, and discharges it at high pressure and high temperature. This discharged gaseous refrigerant is then sent to the condenser 18.

[0016] The condenser 18 is a device connected to the compressor 16 via refrigerant piping 20. The condenser 18 is installed at the front of the vehicle and is a heat exchanger that exchanges heat with the outside air. The gaseous refrigerant discharged by the compressor 16 is condensed and liquefied as it passes through the condenser 18. More specifically, when the air conditioning system 10 is in cooling operation, the condenser 18 releases heat to the outside, reducing the energy of the refrigerant and condensing the gaseous refrigerant into liquid refrigerant.

[0017] As shown in Figure 1, the refrigerant piping 20 connects the evaporator 14, the compressor 16, the condenser 18, and the expansion valve 22, and is the piping through which the refrigerant circulates.

[0018] The expansion valve 22 is located in the passage of the refrigerant piping 20, at the point where the condenser 18 and the evaporator 14 are connected. More specifically, the expansion valve 22 is a pressure reducing device that reduces the pressure of the refrigerant when the high-pressure refrigerant liquefied in the condenser 18 is passed through it. This pressure reduction in the expansion valve 22 is achieved by rapidly expanding the liquid phase refrigerant and spraying it from high pressure to low pressure in a mist. At this time, thermal energy is removed by rapidly expanding the refrigerant from high pressure to low pressure, so the boiling point of the refrigerant decreases. In other words, the temperature of the refrigerant after passing through the expansion valve 22 drops sharply.

[0019] Furthermore, the refrigerant after passing through the expansion valve 22 is a low-pressure, low-temperature atomized (in other words, a gas-liquid two-phase) refrigerant. This gas-liquid two-phase refrigerant flows to the evaporator 14 and exchanges heat with the air in the vehicle cabin, causing the refrigerant circulating within the air conditioning system 10 to evaporate and the air in the vehicle cabin to cool.

[0020] Next, referring to FIG. 2, the state of the refrigerant circulating inside the air conditioner 10 adopting the S-Flow technology and the influence of that state on the quietness of the vehicle will be described. FIG. 2 is a graph showing the state of the refrigerant when the vehicle air conditioner is at a low load. Here, the "state where the air conditioner 10 is at a low load" means that as a result of the air conditioning being controlled according to the number and position of the vehicle occupants by S-Flow, there is no excessive operation of the air conditioner, the load applied to the air conditioner 10 becomes low, and the flow rate of the circulating refrigerant also decreases.

[0021] In the graph of FIG. 2, in addition to the changes in the pressure and temperature of the refrigerant, based on a known Mollier diagram showing the refrigeration cycle of the air conditioner where gas and liquid go back and forth, the refrigeration cycle of the air conditioner 10 in a low-load state is shown. In the mountain-shaped curve displayed in the center of the graph of FIG. 2, the left line shown by the solid line is the saturated liquid line, and the right line shown by the broken line is the saturated vapor line. As also shown in FIG. 2, in the region to the left of the saturated liquid line, the refrigerant exists as a liquid, and in the region to the right of the saturated vapor line, the refrigerant exists as a gas. Also, in the central region surrounded by the saturated liquid line and the saturated vapor line, the refrigerant exists in a gas-liquid two-phase state.

[0022] As shown in Fig. 2, when the air conditioner 10 is in a low-load state, most of the line connecting the condenser 18 and the expansion valve 22 is included in the central region surrounded by the saturated liquid line and the saturated vapor line. This indicates that the refrigerant discharged from the condenser 18 exists in a gas-liquid two-phase state. Here, the graph enclosed by the two-dot chain line below Fig. 2 is a graph for comparison and is a Mollier diagram showing the refrigeration cycle of the air conditioner 10 when the air conditioner 10 is in a normal state (i.e., a state that is not a low load). In the graph of the normal state enclosed by the two-dot chain line shown below, the line connecting the condenser 18 and the expansion valve 22 is arranged in the region to the left of the saturated liquid line. This indicates that the refrigerant discharged from the condenser 18 exists in a liquid state. That is, as is clear from the two graphs shown in Fig. 2, the state of the refrigerant after passing through the condenser 18 differs depending on whether the air conditioner 10 is in a low-load state or a normal state. The difference in the state of the refrigerant is also represented by the lengths of the arrows of the double arrow SC in Fig. 2. This double arrow SC represents the subcooling, which is the difference between the saturated temperature of the refrigerant in the condenser 18 and the actual temperature of the refrigerant from the condenser 18. That is, subcooling indicates how many degrees the refrigerant has dropped from the saturated temperature. As shown in Fig. 2, when the air conditioner 10 is in a low-load state, no subcooling indicating how much the amount further cooled from the saturated liquid line is taken (in Fig. 2, it is expressed by the short length of the arrow of the subcooling indicated by the double arrow SC). In such a case, it means that the refrigerant was not sufficiently cooled by the condenser 18. As a result, although it is originally desirable for the refrigerant after passing through the condenser 18 to be condensed into a liquid-phase refrigerant, when the air conditioner 10 is in a low-load state, gaseous refrigerant remains and is in a gas-liquid two-phase state. On the other hand, in the graph for comparison enclosed by the two-dot chain line below Fig. 2, subcooling is taken (in Fig. 2, it is expressed by the long length of the arrow of the subcooling indicated by the double arrow SC). That is, when the air conditioner 10 is in a normal state (i.e., a state that is not a low load), the refrigerant after passing through the condenser 18 is condensed into a liquid-phase refrigerant as a result of being sufficiently cooled by the condenser 18.

[0023] The above will be further explained, including the function of each component that makes up the vehicle's air conditioning system 10. First, because S-Flow control is in operation in the air conditioning system 10, the load on the air conditioning system 10 is reduced, and the amount of refrigerant circulating within the air conditioning system 10 tends to decrease. When the amount of circulating refrigerant decreases, the evaporator 14, which functions as a heat exchanger, receives less heat from the inside of the vehicle than usual. In other words, the refrigerant cannot completely evaporate as it passes through the evaporator 14, and the refrigerant flowing from the evaporator 14 to the compressor 16 becomes a two-phase gas-liquid refrigerant. Normally, the compressor 16 draws in the low-pressure, low-temperature gas after evaporation in the evaporator 14. However, as described above, the influx of two-phase gas-liquid refrigerant instead of gas causes a liquid accumulation at the intake of the compressor 16. This liquid accumulation reduces the capacity of the compressor 16. As a result, the amount of refrigerant discharged by the compressor 16 becomes less than usual.

[0024] As described above, when the amount of refrigerant discharged by the compressor 16 is less than the amount of refrigerant passing through the expansion valve 22, some of the gaseous refrigerant is more easily passed through the condenser 18, and the refrigerant flows into the expansion valve 22 without being sufficiently cooled in the condenser 18 (i.e., in a gaseous-liquid two-phase state). At this time, bubbles are more likely to form between the condenser 18 and the expansion valve 22, and as a result, two-phase refrigerant bubbles flow into the expansion valve 22. When two-phase refrigerant bubbles pass through the expansion valve 22, vibrations are generated. These vibrations are then transmitted through the refrigerant piping 20 to the evaporator 14 inside the vehicle, and the sound is transmitted to the air conditioning outlet that blows air into the vehicle. As described above, in an air conditioning system 10 employing S-Flow technology, the load on the air conditioning system 10 is reduced, which changes the state of the refrigerant circulating inside the air conditioning system 10 from the normal state, and as a result the refrigerant passage noise becomes louder, which can adversely affect the quietness of the vehicle.

[0025] Therefore, in the vehicle air conditioning system disclosed herein, taking the above characteristics into account, in order to suppress the generation of refrigerant passage noise, even in the air conditioning system 10 employing S-Flow technology, the system is controlled to increase the air conditioning load by increasing the number of air outlets blowing conditioned air into the passenger compartment under certain conditions. This control will be explained in detail with reference to Figure 3.

[0026] Figure 3 is a flowchart illustrating an example of processing in a vehicle's air conditioning system. The control unit 12 determines, using S-Flow, whether the air conditioning is automatically concentrated on one seat (S10). If the air conditioning is automatically concentrated on one seat (Yes in S10), the process proceeds to step S12. On the other hand, if the air conditioning is not automatically concentrated on one seat (No in S10), the process proceeds to step S20. Here, if there are no occupants in seats other than the driver's seat, and the air conditioning operates only in the driver's seat (for example, the conditioned air blown into the passenger compartment is blown only from the vent on the driver's side), the load on the air conditioning system 10 will be low.

[0027] Next, the control unit 12 determines whether the outside temperature is 8°C or higher (S12). If the outside temperature is 8°C or higher (Yes in S12), the process proceeds to step S14. On the other hand, if the outside temperature is less than 8°C (No in S12), the process proceeds to step S30. Generally, when the outside temperature is high, the load on the cooling function of the air conditioning system increases. On the other hand, when the outside temperature is below 8°C, the load on the air conditioning system 10 increases in order to maintain the dehumidification function. That is, when the outside temperature is between 8°C and 30°C, the load on the air conditioning system 10 decreases. Therefore, in S12 of this example, 8°C is used as the criterion to exclude cases where the load on the dehumidification function increases.

[0028] Next, the control unit 12 determines whether the vehicle is stationary or not (S14). If the vehicle is stationary (Yes in S14), the process proceeds to step S16; otherwise, if the vehicle is not stationary (No in S14), the process proceeds to step S30. Here, when the vehicle is stationary, the ambient noise is quieter, so the sound of the refrigerant passing through may become more distinct.

[0029] Next, the control unit 12 determines whether the target temperature after passing through the evaporator 14 is 5°C or higher (S16). If the target temperature after passing through the evaporator 14 is 5°C or higher (Yes in S16), the process moves to step S18; if it is less than 5°C (No in S16), the process moves to step S30. The expansion valve 22 has the function of controlling the flow rate of the refrigerant in addition to its function as a pressure reducing device, but generally it controls the flow rate of the refrigerant so that the target temperature after passing through the evaporator 14 is maintained at 5°C to 10°C. That is, if the target temperature after passing through the evaporator 14 is less than 5°C, the load on the cooling function is high, but if it is 5°C or higher, the load on the air conditioning system 10 is low. For this reason, in this example, 5°C is used as the criterion for determination.

[0030] As described above, if the answer to Yes is given in each branch from S10 to S14, the load on the air conditioning unit 10 is low and the refrigerant passage noise is louder, or the refrigerant passage noise is simply more noticeable because other noises are quieter. Therefore, if the control unit 12 wants to prioritize reducing the refrigerant passage noise, it controls the S-Flow control to change the target of the air conditioning from only the driver's seat to the front seats (S18). More specifically, the control unit 12 controls the air conditioning air blown into the vehicle interior to be blown out from both the driver's seat and passenger's seat vents, which are the front seats.

[0031] Next, the control unit 12 determines whether the air conditioning is automatically concentrated on the front seats (S20). If the air conditioning is automatically concentrated on the front seats (Yes in S20), the process proceeds to step S22. On the other hand, if the air conditioning is not automatically concentrated on the front seats (No in S20), the process proceeds to step S30. Next, the control unit 12 determines whether the outside temperature is 8°C or higher (S22). If the outside temperature is 8°C or higher (Yes in S22), the process proceeds to step S24. On the other hand, if the outside temperature is less than 8°C (No in S22), the process proceeds to step S30. Next, the control unit 12 determines whether the vehicle is stationary (S24). If the vehicle is stationary (Yes in S24), the process proceeds to step S26; otherwise, if the vehicle is not stationary (No in S24), the process proceeds to step S30. Next, the control unit 12 determines whether the target temperature after passing through the evaporator 14 is 8°C or higher (S26). If the target temperature after passing through the evaporator 14 is 8°C or higher (Yes in S26), the process proceeds to step S28; if it is less than 8°C (No in S16), the process proceeds to step S30. Here, in this example, 8°C is used as the criterion, but it is not particularly limited. Note that each determination in S20 to S24 corresponds to each determination in S10 to S14.

[0032] As described above, if the answer to Yes is given in each branch from S20 to S24, the load on the air conditioning unit 10 is low and the refrigerant passage noise becomes louder, or the refrigerant passage noise becomes more noticeable simply because other noises are quieter. In this case, if the control unit 12 wants to prioritize reducing the refrigerant passage noise, it controls the S-Flow control to change the target of the air conditioning from the front seats to all seats (S28). More specifically, the control unit 12 controls the air conditioning air blown into the cabin to be blown out from all seats. On the other hand, if the answer to No is given in each branch of the above steps, the conditions for loud refrigerant passage noise are not met, so the control unit 12 continues with normal S-Flow control (S30).

[0033] It should be noted that the above explanation is merely an example, and in the vehicle air conditioning system disclosed herein, it is sufficient to increase the load on the air conditioning system 10 and suppress the generation of refrigerant flow noise by increasing the number of air outlets that blow conditioned air into the passenger compartment under certain conditions. For this reason, the numerical values ​​of the judgment criteria in the flowchart of Figure 3, in particular, may be changed as appropriate. [Explanation of symbols]

[0034] 10 Vehicle air conditioning system, 12 Control unit, 14 Evaporator, 16 Compressor, 18 Condenser, 20 Refrigerant piping, 22 Expansion valve.

Claims

[Claim 1] A control unit that controls the vehicle's air conditioning, Evaporator and, Compressor and Capacitors and, A refrigerant piping that is a flow path through which the refrigerant circulates, and which connects the evaporator, the compressor, and the condenser, An expansion valve is provided in the refrigerant piping that connects the condenser and the evaporator, Equipped with, The control unit operates to concentrate the air conditioning on one seat in the vehicle cabin, and controls the number of air outlets blowing conditioned air into the vehicle cabin when the load of the air conditioning is below a predetermined value. A vehicle air conditioning system characterized by the following features.

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