Vehicle-mounted air conditioner

Abstract

To prevent a pulsation frequency of an electric compressor from approaching an air column resonance frequency of piping.SOLUTION: The vehicle-mounted air conditioner includes a refrigerant circuit and a controller. The refrigerant circuit includes an electric compressor, a condenser, an expansion valve, and an evaporator, and a refrigerant circulates through the refrigerant circuit. The refrigerant circuit includes a pipe that is connected to the electric compressor and through which the refrigerant discharged from the electric compressor flows. The controller calculates a pulsation frequency f1 of pulsation generated in the pipe based on a target rotation speed ts of the electric compressors based on an air conditioning request (S102). Further, the controller calculates the air column resonance frequency f2 of the pipe based on the sound velocity of the refrigerant and the length of the pipe (S104). When the pulsation frequency f1 falls within a predetermined frequency band including the air column resonance frequency f2 (S106: Yes), the controller updates the target number of revolutions ts of the electric compressors so as to avoid it (S110, S112).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present specification relates to an in-vehicle air conditioner, and more particularly to control of the rotation speed of an electric compressor that compresses and discharges a refrigerant. [Background technology]

[0002] A vehicle is equipped with an air conditioner. The air conditioner includes a refrigerant circuit having an electric compressor, a condenser, an expansion valve, and an evaporator through which a refrigerant circulates. The air conditioner uses a blower to blow air through the evaporator, and then sends the cooled air into the vehicle cabin.

[0003] The refrigerant circuit is connected to an electric compressor and includes piping through which the refrigerant discharged from the compressor flows. The electric compressor draws in the refrigerant using the rotation of a motor, compresses it, and discharges it into the piping. Because the piping vibrates when the electric compressor discharges the refrigerant, technologies to suppress this vibration are being studied.

[0004] Patent Document 1 discloses a technology for reducing compressor pulsation that collides with the wall surface of a bent section in the piping between a condenser and a compressor in a refrigerant circuit of a vehicle air conditioner by providing the bent section at a position that is an integer multiple of half the wavelength of the compressor pulsation away from the condenser. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-23780 Summary of the Invention [Problem to be solved by the invention]

[0006] An electric compressor is a pump, and when the electric compressor is driven, flow pulsation of the refrigerant discharged from the electric compressor occurs in the pipe through which the refrigerant flows. This causes pressure pulsation in the pipe due to the flow pulsation. If the rotation speed of the motor of the electric compressor is N [rpm], the frequency of the pressure pulsation (called the pulsation frequency) is f1 [Hz] = N / 60 (fundamental order).

[0007] On the other hand, the pipe has an air column resonance frequency f2 [Hz], which is determined based on the speed of sound of the refrigerant in the pipe and the length of the pipe.

[0008] If the pulsation frequency f1 coincides with or approaches the air column resonance frequency f2, the pressure pulsation in the piping is amplified, causing the piping to vibrate significantly. Therefore, it is desirable to prevent the pulsation frequency of the electric compressor from approaching the air column resonance frequency of the piping.

[0009] This specification discloses an in-vehicle air conditioner that prevents the pulsation frequency of the electric compressor from approaching the air column resonance frequency of the piping. [Means for solving the problem]

[0010] The vehicle air conditioning system disclosed in this specification includes a refrigerant circuit having an electric compressor, a condenser, an expansion valve, and an evaporator, through which a refrigerant circulates, and a controller. The refrigerant circuit includes a pipe connected to the electric compressor and through which the refrigerant discharged from the electric compressor flows. The controller calculates a pulsation frequency of pulsations occurring in the pipe based on a target rotation speed of the electric compressor based on an air conditioning request, calculates an air column resonance frequency of the pipe based on the sound speed of the refrigerant and a length of the pipe, and updates the target rotation speed of the electric compressor to avoid the pulsation frequency if the pulsation frequency matches the air column resonance frequency or falls within a predetermined frequency band including the air column resonance frequency.

[0011] The vehicle air conditioning system of the present disclosure may further include a temperature sensor that detects a refrigerant temperature of the refrigerant in the piping, and the controller may calculate the speed of sound of the refrigerant based on the refrigerant temperature detected by the temperature sensor.

[0012] In the vehicle air conditioning system of the present disclosure, the electric compressor may be a scroll pump.

[0013] The present specification also discloses an automotive air conditioning system including a refrigerant circuit having an electric compressor, a condenser, an expansion valve, and an evaporator, through which a refrigerant circulates, and a controller. The refrigerant circuit includes a pipe connected to the electric compressor and through which the refrigerant discharged from the electric compressor flows. The controller calculates a pulsation frequency of pulsations occurring in the pipe based on an actual rotation speed of the electric compressor, calculates an air column resonance frequency of the pipe based on the sound speed of the refrigerant and a length of the pipe, and, if the pulsation frequency coincides with the air column resonance frequency or falls within a predetermined frequency band including the air column resonance frequency, updates a target rotation speed of the electric compressor based on an air conditioning request to avoid the pulsation frequency. [Effects of the Invention]

[0014] According to the technology disclosed in this specification, it is possible to prevent the pulsation frequency of the electric compressor from approaching the air column resonance frequency of the piping. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an air conditioning device. [Figure 2] FIG. 10 is a schematic diagram for explaining vibration of a pipe. [Figure 3] 1 is a flowchart illustrating a processing flow according to an embodiment. [Figure 4] FIG. 10 is a timing diagram showing an example of changes in pulsation frequency and air column resonance frequency. [Figure 5] 10 is a flowchart illustrating a process flow according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments will be described with reference to the drawings. In all drawings, equivalent elements are designated by the same reference numerals, and redundant explanations will be omitted.

[0017] Fig. 1 is a schematic diagram showing the configuration of an air conditioner 12 according to an embodiment. The air conditioner 12 is mounted on a vehicle such as an automobile. The air conditioner 12 conditions the air inside the vehicle. As shown in Fig. 1, the air conditioner 12 includes a refrigerant circuit R that serves as a heat source.

[0018] The refrigerant circuit R is a closed circuit that includes, in order along the refrigerant flow direction, an electric compressor 20, a condenser 24, an expansion valve 26, and an evaporator 28, which are connected in sequence by piping. The refrigerant circulates through the refrigerant circuit R. A receiver may be provided between the condenser 24 and the expansion valve 26. An accumulator may be provided between the evaporator 28 and the electric compressor 20.

[0019] The electric compressor 20 is a scroll pump. The electric compressor 20 is equipped with a motor 21, and by rotation of the motor 21, it draws in a refrigerant, compresses it, and discharges it into a pipe P. Note that in FIG. 1, the pipe P between the electric compressor 20 and the condenser 24 is exaggeratedly drawn with double lines, but this pipe P is equivalent to the pipe between other devices. The condenser 24 is a heat exchanger that exchanges heat between the refrigerant and the vehicle running air Wtr. The evaporator 28 is disposed in an air passage 75 of the air conditioning unit 70 and is a heat exchanger that exchanges heat between the refrigerant and the conditioned air Wac. The evaporator 28 cools the conditioned air Wac.

[0020] In the refrigerant circuit R, the refrigerant circulates as follows. The electric compressor 20 discharges high-pressure gas refrigerant, which dissipates heat by exchanging heat with the vehicle running air Wtr in the condenser 24, where it is liquefied and condensed into high-pressure liquid refrigerant. The high-pressure liquid refrigerant flowing out of the condenser 24 is decompressed and expanded by the expansion valve 26, becoming low-pressure refrigerant, and flows into the evaporator 28. The low-pressure refrigerant flowing into the evaporator 28 evaporates by exchanging heat with the air-conditioning air Wac in the evaporator 28, becomes gas refrigerant, flows out of the evaporator 28, and returns to the electric compressor 20.

[0021] The air conditioner 12 includes an air conditioning unit 70 that supplies air cooled by an evaporator 28 into the vehicle interior. The air conditioning unit 70 includes a blower 80 and an air passage 75 formed by a case (not shown). Inside the air passage 75, the blower 80, the evaporator 28, and a heater core 74 are arranged in this order from the air flow direction. The heater core 74 is a heat exchanger that receives, for example, engine coolant or coolant heated by a water heating PTC heater. The heater core 74 may also be configured to receive coolant heated by a condenser 24.

[0022] The blower 80 introduces air into the air passage 75 from an intake port (not shown) and blows the air through the evaporator 28 and the heater core 74, thereby blowing temperature-controlled air into the vehicle cabin. An air mix door 82 is provided inside the air passage 75, and the air mix door 82 adjusts the ratio of air that has passed through the evaporator 28 to air that flows into the heater core 74. Note that the air conditioning unit 70 may employ conventional HVAC (Heating, Ventilation, and Air Conditioning) technology.

[0023] The air conditioner 12 includes a controller 40. The controller 40 has a processor 41 and a storage device 42. The processor 41 performs various calculations and controls by performing processing in accordance with programs stored in the storage device 42. The controller 40 may be, for example, an ECU (Electronic Control Unit) having a microcomputer.

[0024] The controller 40 sets an air conditioning request based on information detected by a plurality of sensors (not shown) that detect the outside air temperature, the inside air temperature, the amount of solar radiation, pressure, etc., and setting information on an operation panel (not shown) operated by a user. The air conditioning request is the output level of the air conditioner 12, and includes, for example, a cooling level that indicates the strength of cooling. The controller 40 controls each device included in the air conditioner 12 based on the air conditioning request. Conventional air conditioner control technology may be adopted for the controller 40.

[0025] 1, the refrigerant circuit R includes a pipe P that is connected to the electric compressor 20 and through which the refrigerant discharged therefrom flows. The pipe P is a pipe between the electric compressor 20 and the condenser 24. The air conditioner 12 includes a temperature sensor 50 that detects the temperature of the refrigerant in the pipe P. As will be described later, the controller 40 calculates the sound speed of the refrigerant based on the refrigerant temperature detected by the temperature sensor 50 in order to obtain the air column resonance frequency of the pipe P.

[0026] 2 is a schematic diagram for explaining vibration of pipe P. As shown in FIG. 2(A), when electric compressor 20 is driven, pressure pulsation 90 of the refrigerant is generated in pipe P. As described above, electric compressor 20 is a scroll pump, and refrigerant is discharged once when motor 21 (see FIG. 1) rotates once. If the rotation speed of motor 21 of electric compressor 20 is N [rpm], the pulsation frequency of the pressure pulsation is f1 [Hz] = N / 60 (fundamental order).

[0027] Furthermore, the pipe P has an air column resonance frequency f2 [Hz]. FIG. 2(B) shows a 1 / 2 wavelength standing wave 92 as an example of a standing wave 92 that represents the natural vibration of an air column. The shape pattern of the standing wave 92 changes depending on the shapes (boundary conditions) of both ends of the pipe P. When both ends of the pipe L are open ends, as shown in FIG. 2(B), both ends of the pipe P become antinodes in the standing wave 92, and a standing wave with a fundamental vibration of 1 / 2 wavelength appears in the pipe P.

[0028] The air column resonance frequency f2 is expressed by the following equation (1) in the case of a standing wave with a fundamental vibration of 1 / 2 wavelength.

[0029] f2=(c / 2L)×m...Equation (1)

[0030] In the above formula (1), c is the sound velocity of the refrigerant, L is the length of the pipe P, and m is the order (an integer equal to or greater than 1 that indicates how many times the vibration is greater than the fundamental vibration). Note that the sound velocity c of the refrigerant varies depending on the type and temperature of the refrigerant.

[0031] When the pulsation frequency f1 of the pressure pulsation (Figure 2(A)) coincides with or approaches the air column resonance frequency f2 (Figure 2(B)), the vibration of the piping P is amplified, causing the piping P to vibrate violently, as shown in Figure 2(C).

[0032] Therefore, when the pulsation frequency f1 coincides with the air column resonance frequency f2 or falls within a predetermined frequency band including the air column resonance frequency f2, the controller 40 updates the target rotation speed of the electric compressor 20 so as to avoid this. This specific processing is shown in FIG. 3.

[0033] 3 is a flowchart showing a process flow according to the embodiment. The controller 40 executes the process flow of FIG. 3 at predetermined intervals.

[0034] In step S100, the controller 40 sets a target rotation speed ts [rpm] for the electric compressor 20 based on an air conditioning request. Note that, hereinafter, the target rotation speed set based on an air conditioning request may be referred to as pts.

[0035] In step S102, the controller 40 calculates the pulsation frequency f1 [Hz]. f1 is calculated by ts / 60.

[0036] In step S104, the controller 40 calculates the air column resonance frequency f2 using the above formula (1). The piping length L and the order m in formula (1) can be stored in advance in the storage device 42 of the controller 40. The sound speed c of the refrigerant is calculated using a calculation formula f(T) that corresponds to the refrigerant used in the refrigerant circuit R and that uses temperature T as a variable. The calculation formula f(T) is stored in advance in the storage device 42 of the controller 40. The controller 40 obtains the refrigerant temperature T from the temperature sensor 50 and substitutes it into the calculation formula f(T) to calculate the sound speed c.

[0037] The sound speed c of the refrigerant may be obtained using a table that associates the temperature T with the sound speed c corresponding to the refrigerant used in the refrigerant circuit R. In this case, the table is stored in advance in the storage device 42 of the controller 40. The controller 40 obtains the refrigerant temperature T from the temperature sensor 50, and obtains the sound speed c corresponding to the refrigerant temperature T from the table.

[0038] In step S106, the controller 40 checks whether the pulsation frequency f1 is within a predetermined frequency band (f2-Δd) to (f2+Δd) that includes the air column resonance frequency f2. In other words, it checks whether the air column resonance frequency f2 is within a predetermined frequency band (f1-Δd) to (f1+Δd) that includes the pulsation frequency f1. Δd is a predetermined frequency width that is stored in advance in the storage device 42 of the controller 40.

[0039] Specifically, in step S106, the controller 40 checks whether |f1-f2| (the absolute value of f1-f2) is less than or equal to Δd. If Δd≧|f1-f2| is not true (S106: No), that is, if Δd<|f1-f2|, the controller 40 determines that the pulsation frequency f1 is not within a predetermined frequency band that includes the air column resonance frequency f2, and ends the processing flow in FIG. 3. In this case, the controller 40 controls the motor 21 of the electric compressor 20 so that the actual rotation speed of the motor 21 becomes the target rotation speed pts [rpm] (the target rotation speed set in step S100).

[0040] On the other hand, when Δd≧|f1 - f2| (S106: Yes), the controller 40 determines that the pulsation frequency f1 falls within a predetermined frequency band including the air column resonance frequency f2, and proceeds to step S108.

[0041] In step S108, the controller 40 checks whether the pulsation frequency f1 is greater than or equal to the air column resonance frequency f2 (f1≧f2). When f1 is greater than or equal to f2 (S108: Yes), in step S110, the controller 40 updates the target rotational speed ts by adding a predetermined rotational speed α (positive value) to the target rotational speed ts. The predetermined rotational speed α is stored in advance in the storage device 42 of the controller 40. When the rotational speed per second of the predetermined rotational speed α [rpm] is represented as α_f (=α / 60), the value of α may be set so as to satisfy the condition α_f>Δd.

[0042] On the other hand, in S108, when f1≧f2 is not satisfied (S108: No), that is, when f1 < f2, in step S112, the controller 40 updates the target rotational speed ts by subtracting a predetermined rotational speed β (positive value) from the target rotational speed ts. The predetermined rotational speed β is stored in advance in the storage device 42 of the controller 40. When the rotational speed per second of the predetermined rotational speed β [rpm] is represented as β_f (=β / 60), the value of β may be set so as to satisfy the condition β_f≧Δd.

[0043] When the controller 40 updates the target rotational speed ts in step S110 or step S112, the controller 40 controls the motor 21 so that the actual rotational speed of the motor 21 of the electric compressor 20 becomes the updated target rotational speed ts [rpm].

[0044] Fig. 4 is a timing diagram showing an example of changes in pulsation frequency f1 and air column resonance frequency f2 when the processing flow of Fig. 3 is executed. In the diagram, pts_f [Hz] is 1 / 60 of the target rotation speed pts [rpm] (S100 in Fig. 3) set based on the air conditioning request. Also, pulsation frequency f1 [Hz] is 1 / 60 of the target rotation speed ts [rpm].

[0045] FIG. 4 shows an example in which the air column resonance frequency f2 changes due to a change in the refrigerant temperature when the target rotation speed pts (pts_f) of the electric compressor 20 based on the air conditioning request is constant.

[0046] In FIG. 4, until time t1, the air column resonance frequency f2 and the target rotation speed pts_f are far apart, so the target rotation speed ts (pulsation frequency f1) is not updated (S106 in FIG. 3: No).

[0047] At time t1, the air column resonance frequency f2 approaches the target rotation speed pts_f (S106: Yes), so the target rotation speed ts (pulsation frequency f1) is increased (S108: Yes, S110 in Figure 3) to prevent the pulsation frequency f1 from approaching the air column resonance frequency f2.

[0048] At time t2, the air column resonance frequency f2 becomes greater than the target rotation speed pts_f (S108: No), so the target rotation speed ts (pulsation frequency f1) is reduced (S112 in FIG. 3) to prevent the pulsation frequency f1 from approaching the air column resonance frequency f2.

[0049] At time t3, the air column resonance frequency f2 has deviated significantly from the target rotation speed pts_f (S106: No in FIG. 3), so the target rotation speed ts (pulsation frequency f1) is returned to the target rotation speed pts (pts_f) based on the air conditioning request.

[0050] Furthermore, at time t4, the air column resonance frequency f2 approaches the target rotation speed pts_f again (S106: Yes), so the target rotation speed ts (pulsation frequency f1) is reduced (S108: No, S112 in FIG. 3) to prevent the pulsation frequency f1 from approaching the air column resonance frequency f2. Note that, although detailed explanation will be omitted to avoid repetition, the same avoidance processing and processing for restoring the target rotation speed as described above are also performed at times t5 and t6.

[0051] According to the embodiment described above, it is possible to prevent the pulsation frequency f1 of the electric compressor 20 from approaching the air column resonance frequency f2 of the piping P. Therefore, it is possible to prevent the vibration amplification of the piping P and to prevent the vibration noise of the piping P from being transmitted to the interior of the vehicle.

[0052] In the embodiment described above, the target rotation speed ts (pulsation frequency f1) is increased or decreased as shown in steps S110 and S112 of FIG. 3 to deviate the target rotation speed ts from the air column resonance frequency f2. However, the target rotation speed ts may not be decreased, that is, the target rotation speed ts may be constantly increased to deviate from the air column resonance frequency f2. In this case, the process of step S112 of FIG. 3 becomes ts = ts + γ instead of ts = ts - β. That is, in step S112, the controller 40 updates the target rotation speed ts by adding a predetermined rotation speed γ (positive value) to the target rotation speed ts. The predetermined rotation speed γ is pre-stored in the storage device 42 of the controller 40. When the number of rotations per second of a predetermined rotation speed γ [rpm] is expressed as γ_f (=γ / 60), the value of γ is preferably set to satisfy the condition γ_f>(Δd+(f2-f1)).

[0053] In the embodiment described above, the temperature sensor 50 is used to detect the refrigerant temperature T, and the sonic speed c of the refrigerant is calculated from the refrigerant temperature T. However, for example, if the value or range of the refrigerant temperature T during operation of the electric compressor 20 can be known in advance, the temperature sensor 50 may be omitted.

[0054] Fig. 5 is a flowchart showing a processing flow according to another embodiment. Steps S200, and S204 to S212 in Fig. 5 are the same as steps S100, and S104 to S112 in Fig. 3. In the processing flow in Fig. 5, step S201 is added, and the processing in step S202 is changed from step S102 in Fig. 3.

[0055] Specifically, in step S201, the controller 40 acquires the actual rotation speed rs [rpm] of the motor 21 of the electric compressor 20. In this embodiment, the air conditioner 12 is provided with a rotation speed sensor that detects the actual rotation speed rs of the motor 21. The controller 40 acquires the actual rotation speed rs [rpm] of the motor 21 from the rotation speed sensor.

[0056] Then, in step S202, the controller 40 calculates the pulsation frequency f1 [Hz] from the actual rotation speed rs of the motor 21. f1 is calculated by rs / 60.

[0057] According to this embodiment, the pulsation frequency f1 can be accurately obtained even when the actual rotation speed of the motor 21 deviates relatively significantly from the target rotation speed. This makes it possible to reliably prevent the pulsation frequency f1 of the electric compressor 20 from approaching the air column resonance frequency f2 of the pipe P. [Explanation of symbols]

[0058] 12 air conditioning unit, 20 electric compressor, 21 motor, 24 condenser, 26 expansion valve, 28 evaporator, 40 controller, 41 processor, 42 storage device, 50 temperature sensor, 70 air conditioning unit, 74 heater core, 75 air passage, 80 blower, 82 air mix door, 90 pressure pulsation, 92 standing wave, P piping, R refrigerant circuit, Wtr driving wind, Wac air conditioning wind.

Claims

1. An in-vehicle air conditioning device, a refrigerant circuit having an electric compressor, a condenser, an expansion valve, and an evaporator, through which a refrigerant circulates; a controller; the refrigerant circuit includes a pipe connected to the electric compressor through which the refrigerant discharged from the electric compressor flows, The controller calculating a pulsation frequency of the pulsation occurring in the piping based on a target rotation speed of the electric compressor based on an air conditioning request; Calculating an air column resonance frequency of the piping based on the sound velocity of the refrigerant and the length of the piping; If the pulsation frequency coincides with the air column resonance frequency or falls within a predetermined frequency band including the air column resonance frequency, the target rotation speed of the electric compressor is updated so as to avoid the pulsation frequency. In-vehicle air conditioner.

2. The vehicle air conditioning system according to claim 1, a temperature sensor for detecting a refrigerant temperature of the refrigerant in the pipe, The controller calculating a sound speed of the refrigerant based on the refrigerant temperature detected by the temperature sensor; In-vehicle air conditioner.

3. 3. The vehicle air conditioning system according to claim 1, The electric compressor is a scroll pump. In-vehicle air conditioner.

4. An in-vehicle air conditioning device, a refrigerant circuit having an electric compressor, a condenser, an expansion valve, and an evaporator, through which a refrigerant circulates; a controller; the refrigerant circuit includes a pipe connected to the electric compressor through which the refrigerant discharged from the electric compressor flows, The controller calculating a pulsation frequency of the pulsation occurring in the piping based on an actual rotation speed of the electric compressor; Calculating an air column resonance frequency of the piping based on the sound velocity of the refrigerant and the length of the piping; If the pulsation frequency coincides with the air column resonance frequency or falls within a predetermined frequency band including the air column resonance frequency, the target rotation speed of the electric compressor is updated based on an air conditioning request so as to avoid the pulsation frequency. In-vehicle air conditioner.

Images