Air duct assembly, indoor unit, and heating and ventilation system

Abstract

An air duct assembly (10), an indoor unit (1), and a heating and ventilation system. A ducted air conditioner comprises a first housing (20) and a second housing (30), wherein the first housing (20) and the second housing (30) cooperate with each other to define a fan chamber (11) and a diffuser chamber (12), which are in communication with each other, a fan (91) being provided in the fan chamber (11), a volute tongue (40) being provided at the transition joint of the fan chamber (11) and the diffuser chamber (12), the fan (91) driving an external airflow to enter the fan chamber (11), and the volute tongue (40) guiding at least part of the airflow to enter the diffuser chamber (12) from the fan chamber (11); and the second housing (30) comprises a return flow channel (31), a first surface (34) which forms a chamber bottom surface of the diffuser chamber (12), and a second surface (35) which forms part of a chamber wall surface of the fan chamber (11), the first surface (34) being provided with a return flow inlet (32), the second surface (35) being provided with a return flow outlet (33), and the return channel (31) extending from the return flow inlet (32) to the return flow outlet (33).

Description

Duct components, indoor units, and HVAC systems

[0001] Related applications

[0002] This application claims priority to the Chinese patent application No. 2024100462926, filed with the China Patent Office on January 11, 2024, with the application number 2024100463191, filed with the China Patent Office on January 11, 2024, with the invention name “A duct structure, indoor unit and HVAC equipment”, and the Chinese patent application No. 2024102743498, filed with the China Patent Office on March 11, 2024, with the application number 2024200763011, filed with the China Patent Office on January 11, 2024, with the invention name “Duct assembly, indoor unit and HVAC system”. The entire text of the above documents is hereby incorporated by reference. Technical Field

[0003] The present application relates to the field of air conditioning technology, and in particular to an air duct assembly, an indoor unit, and a heating and ventilation system. Background Art

[0004] The indoor unit of the existing HVAC system includes an air duct assembly, and the air duct assembly includes a connected fan chamber and a diffuser chamber. A fan is provided in the fan chamber, and the diffuser chamber is used to receive the airflow blown from the fan chamber and diffuse it to increase the pressure and flow of the airflow, thereby improving the cooling or heating effect.

[0005] In the related technology, the air duct assembly is also provided with a volute tongue located at the junction of the fan cavity and the diffuser cavity. The volute tongue is used to divert the airflow of the fan to guide part of the airflow to the diffuser cavity and make part of the airflow flow back to the air inlet side of the fan, thereby causing a pressure difference between the side of the fan close to the volute tongue and the side of the fan away from the volute tongue, thereby generating vortexes. This vortex will affect the operating efficiency of the fan, resulting in poor overall gas flow performance in the air duct assembly. Summary of the Invention

[0006] The embodiments of the present application provide an air duct assembly, an indoor unit, and a HVAC system, which can supplement air and boost pressure on the side of the fan close to the volute tongue to weaken the vortex caused by the pressure difference and improve the aerodynamic performance in the air duct assembly.

[0007] An embodiment of the present application provides an air duct assembly, comprising:

[0008] a first housing; and

[0009] a second housing, wherein the first housing and the second housing cooperate to define a fan cavity and a diffuser cavity that are connected to each other, a fan being disposed in the fan cavity, and a volute tongue being disposed at the junction of the fan cavity and the diffuser cavity, the fan driving external airflow into the fan cavity, and the volute tongue guiding at least a portion of the airflow from the fan cavity into the diffuser cavity;

[0010] The second shell includes a return channel, a first surface constituting the bottom surface of the diffuser chamber, and a second surface constituting part of the wall surface of the fan chamber. The first surface is provided with a return inlet, and the second surface is provided with a return outlet. The return channel extends from the return inlet to the return outlet.

[0011] Based on the air duct assembly, indoor unit and HVAC system of the embodiments of the present application, a return inlet is opened on the first surface of the bottom surface of the cavity forming the diffusion cavity of the second shell, and a return outlet is opened on the second surface of the partial cavity wall surface forming the fan cavity. At the same time, a return channel is set at the second shell, and the return channel extends from the return inlet to the return outlet.

[0012] In this way, the airflow driven by the fan is diverted by the volute to flow to the diffuser chamber and the side of the volute close to the air inlet side of the fan. After the diversion, the airflow pressure flowing into the diffuser chamber becomes larger, so that the airflow pressure at the return inlet is greater than the airflow pressure at the return outlet. Then, through the pressure difference between the return inlet and the return outlet, part of the airflow entering the diffuser chamber is actively guided back to the air inlet side of the volute close to the fan through the return channel to work again. It can not only compensate for the pressure on the side close to the fan and the volute tongue, thereby reducing the vortex caused by the pressure difference, effectively improving the operating efficiency of the fan, and improving the air intake efficiency and pressure resistance of the fan's air inlet side, thereby improving the overall aerodynamic performance of the air duct assembly. At the same time, after reducing the vortex, the aerodynamic noise in the air duct assembly can also be reduced synchronously to improve the user experience. Moreover, since the air flow pressure at the diffuser cavity is greater than the air flow pressure of the volute tongue, compared with the solution of setting the return inlet at the volute tongue, the pressure difference between the return inlet and the return outlet of the present application will also be greater than the solution of setting the return inlet at the volute tongue, thereby further improving the efficiency of the air flow through the return channel to improve the effect of air replenishment and pressurization. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0014] FIG1 is a schematic structural diagram of a ducted air conditioner according to a first embodiment of the present application;

[0015] FIG2 is a schematic diagram of the exploded structure of the duct air conditioner shown in FIG1 ;

[0016] FIG3 is a structural diagram of the ducted air conditioner according to the first embodiment of the present application from another perspective;

[0017] FIG4 is a cross-sectional view of the section AA shown in FIG3 ;

[0018] FIG5 is a partial enlarged view of point A in FIG4 ;

[0019] FIG6 is a cross-sectional view of the air duct assembly of the air duct unit according to the first embodiment of the present application;

[0020] FIG7 is a schematic structural diagram of the ducted air conditioner according to the first embodiment of the present application after the first housing is disassembled;

[0021] FIG8 is a partial enlarged view of point B in FIG7;

[0022] FIG9 is a schematic structural diagram of a second housing of the air duct assembly according to the first embodiment of the present application;

[0023] FIG10 is a partial enlarged view of point N in FIG9 ;

[0024] FIG11 is a schematic structural diagram of the flow guide member of the air duct assembly according to the first embodiment of the present application;

[0025] FIG12 is a structural diagram of an indoor unit according to a second embodiment of the present application;

[0026] FIG13 is a schematic diagram of the exploded structure of the indoor unit shown in FIG12;

[0027] FIG14 is a structural diagram of the indoor unit of the second embodiment of the present application from another perspective;

[0028] FIG15 is a cross-sectional view of the section AA shown in FIG14;

[0029] FIG16 is a cross-sectional view of the section BB shown in FIG14;

[0030] FIG17 is a partial enlarged view of point A in FIG16;

[0031] FIG18 is a schematic structural diagram of the indoor unit of the second embodiment of the present application after the first housing and the fan are disassembled;

[0032] FIG19 is a partial enlarged view of point B in FIG18;

[0033] FIG20 is a schematic structural diagram of the volute, housing, and water tray of the indoor unit of the second embodiment of the present application;

[0034] FIG21 is a schematic structural diagram of a deflector and a guide plate of an indoor unit according to a second embodiment of the present application;

[0035] FIG22 is a schematic diagram of a partial structure of an indoor unit according to a third embodiment of the present application;

[0036] FIG23 is a schematic cross-sectional view of the structure along the AA plane in FIG22;

[0037] FIG24 is a schematic cross-sectional view of the structure along the BB plane in FIG22;

[0038] FIG25 is a schematic cross-sectional view of the structure along the CC plane in FIG22;

[0039] FIG26 is a schematic diagram showing the connection between the lower shell of the diffuser chamber and the volute tongue from a perspective shown in FIG23 ;

[0040] FIG27 is a partial enlarged view of point D in FIG26;

[0041] FIG28 is a schematic diagram showing the connection between the lower shell of the diffuser cavity and the volute tongue from another perspective shown in FIG23;

[0042] FIG29 is a schematic diagram showing the connection between the lower shell of the diffuser chamber and the volute tongue shown in FIG23 from another perspective;

[0043] FIG30 is a partial enlarged view of point E in FIG29;

[0044] FIG31 is a schematic structural diagram of the indoor unit shown in FIG22;

[0045] FIG32 is a schematic diagram of the three-dimensional structure of the indoor unit of the fourth embodiment of the present application;

[0046] FIG33 is a schematic diagram of the three-dimensional structure of the air duct assembly installed on the housing according to the fourth embodiment of the present application;

[0047] FIG34 is a schematic cross-sectional view of the indoor unit according to the fourth embodiment of the present application;

[0048] FIG35 is a partial enlarged view of point Q in FIG34;

[0049] FIG36 is a schematic diagram of the exploded structure of the air duct assembly according to the fourth embodiment of the present application;

[0050] FIG37 is a schematic perspective view of the fourth embodiment of the present application showing a first component mounted on a second component;

[0051] FIG38 is a schematic diagram of the three-dimensional structure of the guide portion installed on the volute tongue and the first plate according to the fourth embodiment of the present application.

[0052] Explanation of the accompanying drawings: 1. Indoor unit; 10. Air duct assembly; 11. Fan chamber; 111. Return air area; 112. First transition area; 12. Diffuser chamber; 121. Bottom surface of the diffuser chamber; 1211. First portion; 1212. Second portion; 121A. Second transition area; 13. Heat exchange chamber; 131. Air outlet area; 14. Air inlet; 15. Air outlet; 14A. Return air inlet; 15A. Air outlet; 181. Return outlet; 20. First housing; 21. Fan chamber upper housing; 21A. Upper cover; 211. Fan chamber housing; 212. Diffuser chamber top housing; 213. Heat exchange chamber top housing; 22. Diffuser chamber upper housing; 23. Heat exchange chamber upper housing; 24. Fan chamber front housing; 25. Third guide portion; 2051. Clamping opening; 251. Third connecting portion; 252. Fixing portion; 253. Guide portion; 26. Second guide rib; 2601. First surface; 2602. Second surface; 261. First protrusion; 262. Second protrusion; 263. Second clamping block; 30. Second housing; 30A. Housing body; 30B. Guide plate; 30b. Uneven portion; 31. Return channel; 311. Reinforcement rib; 3111. Hook; 32, return inlet; 33, return outlet; 34, first surface; 35, second surface; 37, support member; 371, first return air surface; 38, guide member; 381, first connecting portion; 382, ​​first guide portion; 3821, second return air surface; 3822, latching opening; 383, cavity wall; 3831, fixing slot; 39, first guide rib; 391, third surface; 392, fourth surface; 393, first clamping block; 40A, head; 40, volute tongue; 41, guide surface; 42, diffuser surface; 41A, first component; 42A, first mating portion; 43, second mating portion; 45, second component; 402, mating slot; 403, first cavity; 50. Diffuser chamber lower shell; 50A. Diffuser chamber bottom shell; 51. Shell body; 52. Guide plate; 521. Second connecting portion; 522. Second guide portion; 52a. Buckle hole; 51A. First plate body; 501. Diffuser bottom wall; 502. Guide end plate; 60. Water collection tray; 70. Side panel; 80. Insulation layer; 91. Fan; 91a. Air inlet side; 92. Heat exchanger; 93. Electric control box assembly; 98. Grille.

[0053] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of this application clearer, the following part will further describe the embodiments of this application in detail with reference to the accompanying drawings.

[0055] When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application, as detailed in the appended claims.

[0056] In the description of this application, it should be understood that the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances. In addition, in the description of this application, unless otherwise specified, "multiple" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the previous and subsequent associated objects are in an "or" relationship.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the relevant listed items.

[0058] The indoor unit of the existing HVAC system includes an air duct assembly, and the air duct assembly includes a connected fan chamber and a diffuser chamber. A fan is provided in the fan chamber, and the diffuser chamber is used to receive the airflow blown from the fan chamber and diffuse it to increase the pressure and flow of the airflow, thereby improving the cooling or heating effect.

[0059] In the related technology, the air duct assembly is also provided with a volute tongue located at the junction of the fan cavity and the diffuser cavity. The volute tongue is used to divert the airflow of the fan to guide part of the airflow to the diffuser cavity and make part of the airflow flow back to the air inlet side of the fan, thereby causing a pressure difference between the side of the fan close to the volute tongue and the side of the fan away from the volute tongue, thereby generating vortexes. This vortex will affect the operating efficiency of the fan, resulting in poor overall gas flow performance in the air duct assembly.

[0060] First embodiment:

[0061] In order to solve the above problems, the first embodiment of the present application proposes a HVAC system. In the embodiment of the present application, the HVAC system includes but is not limited to equipment such as air conditioners, multi-split units and heat pumps, and can be used in large-scale places such as shopping malls and office buildings. Among them, the HVAC system may include an indoor unit, an outdoor unit and a connecting pipe. The indoor unit 1 is connected to the outdoor unit through a connecting pipe so that the indoor unit and the outdoor unit form a refrigerant circulation. In some actual use scenarios, the indoor unit of the present application can be installed indoors, the outdoor unit is responsible for cooling or heating, and transports the refrigerant through the connecting pipe. The refrigerant exchanges heat with the indoor air and the outdoor air respectively, and the indoor unit is responsible for transporting cold air or hot air to the room to achieve the effect of cooling or heating.

[0062] Referring to Figures 1 to 3, the indoor unit 1 may include, but is not limited to, a duct unit, a wall-mounted indoor unit, and a floor-standing indoor unit. Duct units are typically installed on a ceiling using a suspended ceiling and can be hidden within the ceiling. This allows them to be more concealed and aesthetically pleasing than other indoor unit 1 structures. Furthermore, duct units utilize a decentralized air outlet, resulting in a more comfortable airflow. The indoor unit 1 may include an air duct assembly 10, a fan 91, a heat exchanger 92, and an electrical control box assembly 93.

[0063] With reference to Figures 2, 4, and 5, the air duct assembly 10 is sequentially formed with a fan chamber 11, a pressure diffuser chamber 12, and a heat exchange chamber 13, which are interconnected. The air duct assembly 10 is also formed with an air intake 14 connected to the fan chamber 11 and an air outlet 15 connected to the heat exchange chamber 13. The fan chamber 11 is configured to accommodate a fan 91. The pressure diffuser chamber 12 is used to receive the airflow blown from the fan chamber 11 and diffuse it to increase the pressure and flow of the airflow, thereby improving the cooling or heating effect. The heat exchange chamber 13 is configured to accommodate a heat exchanger 92. Thus, under the action of the fan 91, the external airflow can flow in from the air intake 14 and flow through the fan chamber 11, the pressure diffuser chamber 12, and the heat exchange chamber 13 in sequence, thereby exchanging heat through the heat exchanger 92 in the heat exchange chamber 13 to achieve heating or cooling of the external airflow before flowing out from the air outlet 15.

[0064] The air duct assembly 10 includes a first housing 20 and a second housing 30. The first and second housings 20 and 30 cooperate to define a connected diffuser chamber 12, a fan chamber 11, and a heat exchange chamber 13. The first and second housings 20 and 30 can be made of alloys or metals such as aluminum or steel to meet requirements for structural strength and long service life. Of course, the first and second housings 20 and 30 can also be made of plastic to meet requirements such as light weight, but this is not a limitation in this application. Alternatively, one of the first and second housings 20 and 30 can be made of an alloy or metal, while the other can be made of plastic. Furthermore, the air duct assembly 10 includes two side panels 70. The side panels 70 can be connected to the first and second housings 20 and 30 via snap-fit ​​or screw connections to secure the first and second housings 20 and 30. The side panels 70 are arranged opposite each other. Thus, the first and second housings 20 and 30, along with the side panels 70, form the overall outline of the air duct assembly 10. The air intake 14 may be formed by the first shell 20 , the second shell 30 and the side panel 70 , while the air outlet 15 is formed by the first shell 20 and the second shell 30 .

[0065] It should be noted that the first shell 20, the second shell 30, and the side panels 70 can serve as a shell, so there is no need to set up additional structures such as other shells, thereby reducing the number of structures of the air duct assembly 10 and reducing the volume of the air duct assembly 10, thereby miniaturizing the duct unit 1 to adapt to more use environments with relatively compact installation space. Of course, in other embodiments, the indoor unit 1 may also include a shell, which can be configured to cover the outer surfaces of the first shell 20, the second shell 30, and the side panels 70, leaving only the exhaust port 15 and the air intake port 14 exposed to communicate with the outside world, thereby protecting the first shell 20, the second shell 30, and the side panels 70.

[0066] The electrical control box assembly 93 can be mounted on the surface of the air duct assembly 10 to achieve fixed installation. The electrical control box assembly 93 can be electrically connected to the fan 91 and the heat exchanger 92 respectively to control or adjust the fan 91 and the heat exchanger 92. For example, when the temperature in the environment where the air duct unit 1 is used reaches a set value, the electrical control box assembly 93 can send a command to shut down the fan 91 and the heat exchanger 92, thereby reducing energy consumption and preventing the indoor temperature from being too low or too high.

[0067] Furthermore, the electrical control box assembly 93 can be installed on the surface of the lower shell 50 of the diffusion chamber away from the diffusion chamber 12, and be arranged adjacent to the air suction port 14 and facing the air suction port 14. In this way, maintenance personnel can directly disassemble and assemble the electrical control box assembly 93 at a position adjacent to the air suction port 14. Since there is no other structure blocking the area adjacent to the air suction port 14, it is more convenient for maintenance personnel to operate when disassembling and assembling the electrical control box assembly 93.

[0068] The fan 91 can be configured in a cylindrical, long strip. The fan 91 can be a crossflow impeller, a centrifugal fan, or an axial flow fan, among others. When the fan 91 is configured as a crossflow impeller, it has advantages such as a small radial dimension, low rotational speed, low noise, and uniform air output. Its axial length can be arbitrarily lengthened without affecting the gas flow state, among other advantages. Furthermore, compared to centrifugal or axial flow fans, crossflow impellers are less expensive. Furthermore, the fan 91 can be positioned directly opposite the air intake 14, so that the external airflow can flow to the fan 91 via the air intake 14 in a shorter path, reducing losses during the flow process.

[0069] The heat exchanger 92 is housed in the heat exchange chamber 13 and is connected to the air conditioner outdoor unit through a connecting pipe so that the refrigerant can circulate between the air conditioner outdoor unit and the air conditioner indoor unit 1. When hot air flows into the heat exchange chamber 13 and passes through the heat exchanger 92, the hot air will exchange heat with the refrigerant in the heat exchanger 92, so that the refrigerant can absorb heat, and the heat can be transferred to the refrigerant to achieve a cooling effect. The heat exchanger 92 can be roughly V-shaped, so that the heat exchange area can be increased and the heat exchange efficiency can be improved. The heat exchanger 92 and the exhaust port 15 can be arranged to face each other. In this way, the airflow can flow to the exhaust port 15 along a shorter path after flowing through the heat exchanger 92, so as to reduce the loss of the airflow during the flow process.

[0070] In addition, in some structural forms, the inner surface of the first shell 20 facing the diffusion chamber 12 and the inner surface of the second shell 30 facing the diffusion chamber 12 are provided with an insulation layer 80. The insulation layer 80 can be an insulation sponge or insulation glue. In this way, by providing the insulation layer 80, the temperature inside the air duct assembly 10 can be maintained to a certain extent, and the probability of energy dissipating outward through the first shell 20 and the second shell 30 can be reduced.

[0071] 4 and 5 , in order to improve the gas flow performance during use of the indoor unit 1, a return inlet 32 ​​is provided on the first surface 34 of the bottom surface of the second shell 30 constituting the pressure diffuser chamber 12, and a return outlet 33 is provided on the second surface 35 of a portion of the cavity wall surface constituting the fan cavity 11. At the same time, a return channel 31 is provided at the second shell 30, and the return channel 31 extends from the return inlet 32 ​​to the return outlet 33.

[0072] In this way, the airflow driven by the fan 91 is diverted by the volute 40 to flow to the diffuser chamber 12 and the side of the volute 40 close to the air inlet side of the fan 91. After the diversion, the airflow pressure flowing into the diffuser chamber 12 becomes greater, so that the airflow pressure at the return inlet 32 ​​is greater than the airflow pressure at the return outlet 33. Then, through the pressure difference between the return inlet 32 ​​and the return outlet 33, part of the airflow entering the diffuser chamber 12 is actively guided back to the air inlet side of the volute 40 close to the fan 91 through the return channel 31 to work again. It can not only compensate for the pressure on the side close to the fan 91 and the volute tongue 40, thereby reducing the vortex caused by the pressure difference, and effectively improve the operating efficiency of the fan 91, so as to improve the air intake efficiency and pressure resistance of the air inlet side of the fan 91, thereby improving the overall aerodynamic performance of the air duct assembly 10, and at the same time, after reducing the vortex, it can also simultaneously reduce the aerodynamic noise in the air duct assembly 10 to improve the user experience, and because the air flow pressure at the diffusion chamber 12 is greater than the air flow pressure of the volute tongue 40, compared with the solution of setting the return inlet 32 ​​at the volute tongue 40, the pressure difference between the return inlet 32 ​​and the return outlet 33 of the present application will also be greater than the solution of setting the return inlet 32 ​​at the volute tongue 40, thereby further improving the efficiency of the air flow through the return channel 31 to improve the effect of air replenishment and pressurization.

[0073] In some structural forms, the return channel 31 is arranged in a curved shape. Specifically, the return channel 31 can be arranged in a curved shape, such as an arc or a wavy line, which can slow down the impact speed of the airflow within the return channel 31, further reducing airflow noise and stabilizing airflow. It should be noted that in other embodiments, the return channel 31 can also be arranged in a straight line, thereby increasing air volume at the same fan 91 speed. Alternatively, the return channel 31 can be a combination of a straight line and a curve, and the specific selection can be made by those skilled in the art according to their needs.

[0074] Optionally, the width of the return channel 31 remains constant from the return inlet 32 ​​to the return outlet 33, thereby maintaining a stable flow of air through the return channel and thereby maintaining a stable flow rate through the return channel 31, thereby improving the effect of replenishing air and boosting pressure on the side of the fan near the volute tongue. Alternatively, in another embodiment, the width of the return channel 31 is configured to gradually expand from the return inlet 32 ​​to the return outlet 33. That is, the change in the width of the return channel 31 gradually increases from the return inlet 32 ​​to the return outlet 33. With this configuration, the change in the width of the return channel 31 is initially small at the return inlet 32, allowing for uniform mixing of the airflow as it enters the return channel 31. Thereafter, the change in the width of the return channel 31 continues to increase. While ensuring that flow separation does not occur within the return channel 31, the change in width is maximized for the same channel length, thereby ensuring that the airflow rate is maintained while reducing the airflow velocity, thereby achieving the purpose of reducing noise.

[0075] Referring to Figure 6, in some embodiments, the return flow channel 31 passes through the rotor of fan 91 at an extension line L0 of the return flow outlet and forms an angle θ with the outer peripheral tangent line L1 of the rotor of fan 91, where θ is less than or equal to 15 degrees and greater than or equal to 0 degrees. This ensures that the airflow stabilizes the eccentric vortex of the rotor of fan 91 while preventing excessive impact of the airflow on the rotor of fan 91, which could cause noise. When θ is greater than 15 degrees, the airflow may impact the rotor of fan 91 too strongly, causing vibration and noise. When θ is less than 0 degrees, the airflow's supplementary effect on the rotor of fan 91, i.e., the airflow's effectiveness in stabilizing the eccentric vortex of the rotor of fan 91, is less effective. For example, θ can be 0 degrees, 2 degrees, 5 degrees, 7 degrees, 10 degrees, 12 degrees, or 15 degrees, etc., and this is not limited in the present embodiment.

[0076] Furthermore, θ is equal to 0 degrees. Thus, the extended line L0 of the return channel 31 at the return outlet 33 coincides with the outer peripheral tangent line L1 of the fan 91 , thereby stabilizing the eccentric vortex of the fan 91 through the return outlet 33 while preventing the airflow from impacting the fan 91 and generating noise.

[0077] In some embodiments, with reference to FIG6 , the return channel 31 extends from the return outlet 33 toward the outer side of the rotor of the fan 91, and forms an angle β with the outer peripheral tangent line L1 of the rotor of the fan 91, with β being less than or equal to 45 degrees and greater than or equal to 0 degrees. This ensures that the airflow stabilizes the eccentric vortex of the rotor of the fan 91 while preventing excessive impact of the airflow on the rotor of the fan 91, which could cause noise. When β is less than 0 degrees, the airflow may impact the rotor of the fan 91 too strongly, causing vibration and noise. When θ is greater than 0 degrees, the airflow's supplementary effect on the rotor of the fan 91 is reduced, meaning that the airflow's effectiveness in stabilizing the eccentric vortex of the rotor of the fan 91 is less effective. For example, β can be 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 45 degrees, and so on, though this is not a limitation in the present embodiment.

[0078] Furthermore, β is equal to 0 degrees. Thus, the extended line L0 of the return channel 31 at the return outlet 33 coincides with the outer peripheral tangent line L1 of the fan rotor of the fan 91. This allows the airflow flowing out through the return outlet 33 to stabilize the eccentric vortex of the fan rotor of the fan 91 while preventing the airflow from impacting the fan 91 and generating noise.

[0079] In some structural forms, the second shell 30 further includes a connecting surface (not shown) connected between the first surface 34 and the second surface 35. The connecting surface is concave to form an airflow groove. One end of the airflow groove passes through the first surface 34 to connect to the reflux inlet 32, and the other end of the airflow groove passes through the second surface 35 to connect to the reflux outlet 33. The volute tongue 40 covers the connecting surface so that the airflow groove forms the reflux channel 31. In this way, by providing the airflow groove on the connecting surface to form the reflux channel 31, the process difficulty is low and the processing is convenient. At the same time, when maintenance personnel need to clean and maintain the reflux channel 31 later, after removing the volute tongue 40 to expose the connecting surface, the airflow groove forming the reflux channel 31 can be directly cleaned and maintained, thereby facilitating regular cleaning of the reflux channel 31 and ensuring the smooth flow of the reflux channel 31.

[0080] Referring to Figures 5 and 6 , in some structural forms, the first housing 20 may include a fan chamber front housing 24, a fan chamber upper housing 21, a diffuser chamber upper housing 22, and a heat exchange chamber upper housing 23, which are connected in sequence. The second housing 30 includes a diffuser chamber lower housing 50, a support member 37, and a flow guide 38. The diffuser chamber lower housing 50 has a first surface 34, which forms the bottom surface of the diffuser chamber 12 and is used to guide airflow to the heat exchange chamber 13. The diffuser chamber lower housing 50 is connected to the volute 40. The support member 37 is connected to the side of the diffuser chamber lower housing 50 facing away from the first surface 34 and is also connected to the volute 40. In this way, the volute 40 is connected simultaneously by the diffuser chamber lower housing 50 and the support member 37, thereby improving the positional stability of the volute 40 after connection. The flow guide 38 is connected to the side of the diffuser chamber lower housing 50 facing away from the first surface 34, and the flow guide 38 and the support member 37 cooperate to form the return flow outlet 33.

[0081] The fan chamber front housing 24, the fan chamber upper housing 21, the volute tongue 40, and the end of the flow guide 38 away from the diffuser chamber lower housing 50 cooperate to define the fan chamber 11. Furthermore, the fan chamber front housing 24, the fan chamber upper housing 21, the diffuser chamber upper housing 22, and the heat exchange chamber upper housing 23 can be an integrated structure to improve the connection strength of the three and reduce the number of assembly steps. The diffuser chamber upper housing 22 cooperates with the volute tongue 40 and the diffuser chamber lower housing 50 to define the diffuser chamber 12.

[0082] In addition, the second shell 30 also includes a water receiving pan 60. The water receiving pan 60 is located below the heat exchanger 92 and is used to receive the condensed water flowing out of the heat exchanger 92. It cooperates with the heat exchange chamber upper shell 23 of the first shell 20 to define the heat exchange chamber 13. Furthermore, the diffuser chamber lower shell 50 and the water receiving pan 60 can be an integrally molded component, making the connection between the two more secure and reducing the assembly steps to improve assembly efficiency. Of course, in other structural forms, the diffuser chamber lower shell 50 and the water receiving pan 60 can be a split structure, and the two can be fixed by a snap connection or a threaded connection, which is not limited in this application.

[0083] The side of the support member 37 facing away from the volute tongue 40 is configured as a first return air surface 371 and is spaced apart from the support member 37. The side of the air guide member 38 facing the support member 37 is configured as a second return air surface 3821. The second return air surface 3821 and the first return air surface 371 cooperate to form the return flow channel 31. Thus, the support member 37 and the air guide member 38 cooperate to form the return flow channel 31, that is, a split structural design is adopted to form the return flow channel 31 and the return flow outlet 33. This facilitates disassembly and control to change the shape of the return flow channel 31, and makes it easier to control the direction of the return flow outlet 33.

[0084] 7 to 9 , further, to reduce deformation of the guide member 38 and the support member 37 when air flows through the return channel 31, at least one first guide rib 39 is provided on one of the first return air surface 371 and the second return air surface 3821, and the other of the first return air surface 371 and the second return air surface 3821 abuts against the at least one first guide rib 39. Thus, the first guide rib 39 can provide support for the guide member 38 and the support member 37, further reducing deformation of the guide member 38 and the support member 37.

[0085] Furthermore, the first guide rib 39 is protruding from the first return air surface 371 and is integrally formed with the first return air surface 371, and the second return air surface 3821 abuts the first guide rib 39. Alternatively, in another embodiment, the first guide rib 39 is protruding from the second return air surface 3821 and is integrally formed with the second return air surface 3821, and the first return air surface 371 abuts the first guide rib 39. In this manner, by integrally providing the first guide rib 39 with one of the first return air surface 371 and the second return air surface 3821 and abutting the other, the attachment area of ​​the first guide rib 39 is larger, the structural stability is enhanced, the interaction force between the first guide rib 39, the guide member 38, and the support member 37 is stronger, and deformation is less likely to occur.

[0086] Optionally, with reference to Figures 7 to 9 , one of the first return air surface 371 and the second return air surface 3821 is provided with a plurality of first guide ribs 39 . The plurality of first guide ribs 39 are arranged side by side and spaced apart in the transverse direction of the return flow channel 31 . The plurality of first guide ribs 39 divide the return flow inlet 32 ​​into a plurality of sub-inlets. The transverse direction of the return flow channel 31 is perpendicular to the direction of airflow within the return flow channel 31 and perpendicular to the direction from the first return air surface 371 toward the second return air surface 3821 . Referring to Figure 10 , the direction indicated by arrow T is the transverse direction of the return flow channel 31 . In this way, multiple first guide ribs 39 are provided to further improve the structural stability of the guide member 38 and the support member 37. At the same time, the return inlet 32 ​​is divided into multiple sub-inlets by multiple first guide ribs 39, and the return channel 31 is divided into multiple sub-ducts. The airflow separated from the diffuser chamber 12 is divided into multiple airflows to lead out of the diffuser chamber 12, and the pressure of the airflow entering the return channel 31 is divided. The airflow pressure of the airflow entering a single sub-duct is relatively small, and the force of the airflow in each sub-duct on the guide member 38 and the support member 37 is also relatively small, thereby reducing the impact on the guide member 38 and the support member 37, thereby further reducing the deformation of the guide member 38 and the support member 37 caused by the airflow entering the return duct.

[0087] 5 , 10 , and 11 , the air duct assembly 10 further includes a plurality of first clamping blocks 393 . Each first clamping block 393 is protruding from the first guide rib 39 located on the first return air surface 371 and is integrally formed with the first guide rib 39 . The second return air surface 3821 is provided with a plurality of latching openings 3822 , and each first clamping block 393 is inserted into one of the latching openings 3822 . During assembly, by inserting the first clamping block 393 into the corresponding latching opening 3822 , the air guide 38 and the support member 37 can be quickly aligned. This facilitates assembly, effectively improves the alignment stability of the air guide 38 and the support member 37 , and effectively prevents deformation of the air guide 38 and the support member 37 when the wind pressure is excessive.

[0088] Optionally, the first guide rib 39 extends along the longitudinal direction of the return channel 31 and from the return inlet 32 ​​toward the side where the return outlet 33 is located. The longitudinal direction of the return channel 31 is the direction of airflow within the return channel 31. A plurality of first guide ribs 39 are provided on one of the first return air surface 371 and the second return air surface 3821. The plurality of first guide ribs 39 are arranged side by side and spaced apart along the transverse direction of the return channel 31. The transverse direction of the return channel 31 is perpendicular to the direction of airflow within the return channel 31 and perpendicular to the direction from the first return air surface 371 toward the second return air surface 3821. Thus, the first guide ribs 39 extend through the return channel 31 along the longitudinal direction of the return channel 31, thereby stabilizing the airflow out of the return channel 31 and reducing the wind resistance on the air inlet side of the fan 91.

[0089] Furthermore, in the transverse direction of the return channel 31 , the intervals between two adjacent first guide ribs 39 are equal, so as to facilitate processing and ensure that the overall force balance is achieved when the support member 37 and the guide member 38 are installed.

[0090] Of course, the spacing between two adjacent first guide ribs 39 can also be unequal. It is understandable that, in the transverse direction of the return channel 31, the airflow pressure in different areas of the return channel 31 may vary. In areas with stronger airflow pressure, the airflow exerts a stronger force on the support member 37 and the guide member 38, making the support member 37 and the guide member 38 more likely to deform. Therefore, in the transverse direction of the return channel 31, the return channel 31 includes multiple return air zones arranged side by side, with the airflow pressure in adjacent return air zones differing. The spacing between two adjacent first guide ribs 39 in a return air zone with higher airflow pressure is a1, while the spacing between two adjacent first guide ribs 39 in a return air zone with lower airflow pressure is a2, where a2 > a1. Thus, in the transverse direction of the return channel 31, when the airflow pressure in the middle area is higher and the airflow pressure in the edge area is lower, the spacing between two adjacent first guide ribs 39 gradually decreases from the edge area toward the middle area, resulting in a distribution of multiple first guide ribs 39 that is denser in the middle and more sparse at the edges.

[0091] Referring to Figure 10 , optionally, at least one first guide rib 39 provided on one of the first return air surface 371 and the second return air surface 3821 includes two third surfaces 391 disposed opposite each other. The two third surfaces 391 are disposed perpendicularly or at an obtuse angle toward a portion of the first return air surface 371 or the second return air surface 3821 on the same side. This allows for a larger connection area between the first guide rib 39 and the corresponding guide member 38 and support member 37, thereby improving the installation stability of the first guide rib 39.

[0092] Furthermore, the first guide rib 39 has a fourth surface 392 connected between the two third surfaces 391. The fourth surface 392 abuts the other of the first return air surface 371 and the second return air surface 3821. This improves the support stability of the first guide rib 39 on the support member 37 and the guide member 38. For example, when both third surfaces 391 of the first guide rib 39 are in contact with the first return air surface 371, the fourth surface 392 abuts the second return air surface 3821; when both third surfaces 391 of the first guide rib 39 are in contact with the second return air surface 3821, the fourth surface 392 abuts the first return air surface 371.

[0093] Optionally, the vertical spacing between the two third surfaces 391 gradually decreases or remains unchanged in the direction from the return inlet 32 ​​of the return channel 31 toward the return outlet 33. Considering that the pressure of the airflow at the return inlet 32 ​​is greater and the pressure of the airflow at the return outlet 33 is less, preferably, the vertical spacing between the two third surfaces 391 in the transverse direction of the return channel 31 gradually decreases in the direction from the return inlet 32 ​​of the return channel 31 toward the return outlet 33, thereby gradually increasing the flow area of ​​the sub-air duct.

[0094] In some configurations, the diffuser lower shell 50 and the support member 37 are integrally formed. This not only reduces installation steps but also improves the structural strength of the diffuser lower shell 50 and the support member 37, thereby reducing deformation of the support member 37 caused by the impact of airflow within the return channel 31. Similarly, the diffuser lower shell 50 and the flow guide 38 can also be integrally formed. This also improves the structural strength of the flow guide 38.

[0095] 5 and 11 , in some structural forms, the air guide 38 includes a first connecting portion 381, a first air guide portion 382, ​​and a cavity wall portion 383. The first connecting portion 381 is stacked on the side of the diffuser cavity lower shell 50 facing away from the first surface 34 and is detachably mounted on the diffuser cavity lower shell 50. The first connecting portion 381 can be configured as a flat plate and stacked and fitted with the diffuser cavity lower shell 50 to increase the contact area between the two and thereby improve the stability of the connection. The first air guide portion 382 is connected to the first connecting portion 381 at an angle and has a second return air surface 3821. The first air guide portion 382 is used to cooperate with the support member 37 to form the return flow channel 31 and the return flow outlet 33. The first air guide portion 382 can be configured as an arc-shaped plate to facilitate guiding the direction of the airflow. The cavity wall portion 383 is connected at an angle to the end of the first air guide portion 382 that faces away from the first connecting portion 381 and extends away from the diffuser chamber lower shell 50. Thus, the cavity wall portion 383 cooperates to form a portion of the cavity wall of the fan cavity 11, thereby also guiding airflow toward the fan 91. The first connecting portion 381, the first air guide portion 382, ​​and the cavity wall portion 383 can be integrally formed to enhance the overall structural stability of the air guide 38. Of course, the above three components can also be provided separately to facilitate the subsequent maintenance and replacement of individual components.

[0096] Furthermore, the first connecting portion 381 has a first connecting hole, and the diffuser chamber lower shell 50 has a second connecting hole corresponding to the first connecting hole. The air duct assembly 10 also includes a fastener that passes through the second connecting hole and the first connecting hole in sequence to secure the first connecting portion 381 to the diffuser chamber lower shell 50. The first and second connecting holes can be threaded holes, and the fastener can be a screw. The screws are used to secure the first connecting portion 381 to the diffuser chamber lower shell 50. This securing method is relatively simple to install and operate, and is easy to disassemble, facilitating subsequent maintenance.

[0097] To prevent foreign matter from entering the fan chamber 11, the diffuser chamber 12, and the heat exchange chamber 13, the air duct assembly 10 further includes a grille 98, which is detachably connected to the chamber wall portion 383 and covers the air inlet side of the fan chamber 11. By providing the grille 98 to cover the air inlet side of the fan 91, the fan 91 and the heat exchanger 92 are protected, thereby extending the service life of the air duct assembly 10. The grille 98 can be detachably connected to the chamber wall portion 383, thereby improving the stability of the grille 98 installation and eliminating the need for additional structures to connect the grille 98. This reduces the number of structures in the air duct assembly 10, reduces the volume of the air duct assembly 10, and achieves miniaturization of the indoor unit 1. Of course, to further improve the stability of the grille 98 connection, the grille 98 can also be additionally connected to the first housing 20, thereby further improving the stability of the grille 98 connection.

[0098] Furthermore, one of a fixing buckle and a fixing slot 3831 is provided on the end of the cavity wall portion 383 facing away from the first air guide portion 382, ​​and the other of the fixing buckle and the fixing slot 3831 is provided on the grille 98. The fixing buckle and the fixing slot 3831 engage with each other. This combination of fixing buckle and fixing slot 3831 not only ensures the stability of the relative fixation between the cavity wall portion 383 and the grille 98, but also eliminates the need for additional tools for disassembly, reducing the difficulty of subsequent disassembly.

[0099] Second embodiment:

[0100] The second embodiment of the present application proposes a HVAC system. In the second embodiment of the present application, the HVAC system includes but is not limited to equipment such as air conditioners, multi-split units, and heat pumps, and can be used in large-scale places such as shopping malls and office buildings. The HVAC system may include an indoor unit 1, an outdoor unit, and a connecting pipe. The indoor unit 1 is connected to the outdoor unit through a connecting pipe so that a refrigerant circulation is formed between the indoor unit 1 and the outdoor unit. In some actual usage scenarios, the indoor unit 1 of the present application can be installed indoors, the outdoor unit is responsible for cooling or heating, and transports the refrigerant through the connecting pipe. The refrigerant exchanges heat with the indoor air and the outdoor air respectively, and the indoor unit 1 is responsible for transporting cold air or hot air into the room to achieve the effect of cooling or heating.

[0101] 12 to 14 , the indoor unit 1 may include, but is not limited to, a duct unit, a wall-mounted indoor unit, and a floor-standing indoor unit. Duct units are typically installed on a ceiling using a suspended ceiling and can be hidden within the ceiling. This allows them to be more concealed and aesthetically pleasing than other indoor unit 1 structures. Furthermore, duct units utilize a decentralized air outlet, resulting in a more comfortable airflow. The indoor unit includes an air duct assembly 10, a fan 91, a heat exchanger 92, and an electrical control box assembly 93.

[0102] The air duct assembly 10 is used to construct an air duct for the indoor unit 1 for air flow. Referring to Figures 13 and 15 , specifically, the air duct assembly 10 includes a first shell 20 and a second shell 30. The first shell 20 and the second shell 30 cooperate to define a diffuser chamber 12, a fan chamber 11, and a heat exchange chamber 13 that are connected to each other. The first shell 20 and the second shell 30 also form an air intake 14 connected to the fan chamber 11 and an air outlet 15 connected to the heat exchange chamber 13. The fan chamber 11 is configured to accommodate a fan 91. The diffuser chamber 12 is used to receive the airflow blown from the fan chamber 11 and diffuse it to increase the pressure and flow of the airflow, thereby improving the cooling or heating effect. The heat exchange chamber 13 is configured to accommodate a heat exchanger 92. In this way, the external air flow can flow in from the air intake port 14 under the action of the fan 91, and flow through the fan chamber 11, the diffuser chamber 12 and the heat exchange chamber 13 in sequence, and then pass through the heat exchanger 92 in the heat exchange chamber 13 to heat or cool the external air flow before flowing out from the exhaust port 15.

[0103] The first and second housings 20 and 30 can be made of alloys or metals such as aluminum or steel, or hard plastic materials to meet requirements such as structural strength and long service life. Of course, the first and second housings 20 and 30 can also be made of plastic to meet requirements such as light weight, and this is not a limitation in this application. Alternatively, one of the first and second housings 20 and 30 can be made of an alloy or metal, while the other can be made of plastic. Furthermore, the air duct assembly 10 includes two side panels 70, which can be connected to the first and second housings 20 and 30 via snaps or screws to secure them together. The side panels 70 are positioned opposite each other. The first and second housings 20, 30, and side panels 70 together define the overall contour of the air duct assembly 10. The air intake 14 can be formed by the first and second housings 20, 30, and side panels 70, while the air outlet 15 can be formed on the first housing 20.

[0104] It should be noted that the first shell 20, the second shell 30, and the side panels 70 can serve as a housing, so there is no need to set up additional structures such as other shells, thereby reducing the number of structures in the air duct assembly 10 and reducing the volume of the air duct assembly 10, thereby miniaturizing the indoor unit 1 to adapt to more environments with relatively compact installation spaces. Of course, in other embodiments, the indoor unit may also include a housing, which can be configured to cover the outer surfaces of the first shell 20, the second shell 30, and the side panels 70, leaving only the exhaust port 15 and the air intake port 14 exposed for communication with the outside world, thereby protecting the first shell 20, the second shell 30, and the side panels 70.

[0105] The fan 91 can be arranged in a cylindrical strip shape. The fan 91 can be a crossflow fan, a centrifugal fan 91, or an axial flow fan 91, etc. When the fan 91 is configured as a crossflow fan, the crossflow fan has the advantages of small radial size, low speed, low noise, uniform air output, etc. Its axial length can be arbitrarily extended without affecting the gas flow state, etc., and compared with centrifugal fans 91 or axial flow fans 91, the cost of the crossflow fan is lower. The fan 91 can also be arranged directly opposite the air intake 14, so that the external airflow can flow to the fan 91 through the air intake 14 in a shorter path, reducing losses during the flow process.

[0106] The heat exchanger 92 is housed in the heat exchange chamber 13 and is connected to the air conditioner outdoor unit via a connecting pipe, so that the refrigerant can circulate between the air conditioner outdoor unit and the air conditioner indoor unit. When hot air flows into the heat exchange chamber 13 and passes through the heat exchanger 92, the hot air will exchange heat with the refrigerant in the heat exchanger 92, so that the refrigerant can absorb heat, and the heat can be transferred to the refrigerant to achieve a cooling effect. The heat exchanger 92 can be roughly V-shaped, so that the heat exchange area can be increased and the heat exchange efficiency can be improved. The heat exchanger 92 and the exhaust port 15 can be arranged to face each other. In this way, the airflow can flow to the exhaust port 15 via a shorter path after flowing through the heat exchanger 92, so as to reduce the loss of the airflow during the flow process.

[0107] The electrical control box assembly 93 can be mounted on the surface of the air duct assembly 10 to achieve fixed installation. The electrical control box assembly 93 can be electrically connected to the fan 91 and the heat exchanger 92 respectively to control or adjust the fan 91 and the heat exchanger 92. For example, when the temperature in the environment where the indoor unit 1 is operating reaches a set value, the electrical control box assembly 93 can send a command to shut down the fan 91 and the heat exchanger 92, thereby reducing energy consumption and preventing the indoor temperature from being too low or too high.

[0108] Furthermore, referring to FIG4 , the electric control box assembly 93 can be installed on the surface of the lower shell 50 of the pressure diffuser chamber facing away from the pressure diffuser chamber 12, and can be arranged adjacent to and facing the air inlet 14. In this way, maintenance personnel can directly disassemble and assemble the electric control box assembly 93 at a location adjacent to the air inlet 14. Since there is no other structure blocking the area adjacent to the air inlet 14, maintenance personnel can more conveniently disassemble and assemble the electric control box assembly 93. In some structural forms, the inner surface of the first shell 20 facing the pressure diffuser chamber 12 and the inner surface of the second shell 30 facing the pressure diffuser chamber 12 are provided with an insulation layer 80. The insulation layer 80 can be an insulation sponge or insulation glue. In this way, by providing the insulation layer 80, the temperature in the air duct assembly 10 can be maintained to a certain extent, reducing the probability of energy in the indoor unit 1 being dissipated outward through the first shell 20 and the second shell 30.

[0109] Referring to Figures 15 to 17, in an embodiment of the present application, the second shell 30 includes a shell body 30A and a guide plate 30B connected to each other. The shell body 30A is provided with a return channel 31. The return channel 31 includes a return inlet 32 ​​and a return outlet 33. The return inlet 32 ​​is connected to the diffuser chamber 12, and the return outlet 33 is connected to the fan chamber 11.

[0110] It can be understood that in the direction from the pressure diffuser chamber 12 to the heat exchange chamber 13, the pressure diffuser chamber 12 is gradually expanded, and the lateral flow area of ​​the gas in the pressure diffuser chamber 12 gradually increases. As the lateral flow area of ​​the gas gradually increases, the flow rate of the gas gradually decreases, the dynamic pressure decreases, and the static pressure increases. The larger static pressure can help the airflow flowing out of the exhaust port 15 to overcome the air resistance more effectively, so that it can reach a farther distance relative to the exhaust port 15. The return channel 31 is configured to connect the pressure diffuser chamber 12 and the fan chamber 11, the return inlet 32 ​​connects to the pressure diffuser chamber 12, and the return outlet 33 connects to the fan chamber 11. The airflow pressure (static pressure) in the pressure diffuser chamber 12 gradually increases, so that the airflow pressure at the return inlet 32 ​​is greater than the airflow pressure at the return outlet 33, so that part of the airflow entering the pressure diffuser chamber 12 is actively guided back to the air inlet side 91a of the fan 91 through the return channel 31. In this way, the vortex effect can be weakened, the operating efficiency of the fan 91 can be effectively improved, and the overall aerodynamic performance of the air duct assembly 10 can be enhanced. At the same time, after the vortex is weakened, the aerodynamic noise in the air duct assembly 10 can be reduced synchronously to enhance the user experience.

[0111] In some structural forms, the return channel 31 is arranged in a curved shape. Specifically, the return channel 31 can be arranged in a curved shape, such as an arc or a wavy line, which can slow down the impact speed of the airflow within the return channel 31, further reducing airflow noise and stabilizing airflow. It should be noted that in other embodiments, the return channel 31 can also be arranged in a straight line, thereby increasing air volume at the same fan 91 speed. Alternatively, the return channel 31 can be a combination of a straight line and a curve, and the specific selection can be made by those skilled in the art according to their needs.

[0112] Optionally, the width of the return channel 31 remains constant from the return inlet 32 ​​to the return outlet 33, thereby maintaining a stable flow of air through the return channel and thereby maintaining a stable flow rate through the return channel 31, thereby improving the effect of replenishing air and boosting pressure on the side of the fan near the volute tongue. Alternatively, in another embodiment, the width of the return channel 31 is configured to gradually expand from the return inlet 32 ​​to the return outlet 33. That is, the change in the width of the return channel 31 gradually increases from the return inlet 32 ​​to the return outlet 33. With this configuration, the change in the width of the return channel 31 is initially small at the return inlet 32, allowing for uniform mixing of the airflow as it enters the return channel 31. Thereafter, the change in the width of the return channel 31 continues to increase. While ensuring that flow separation does not occur within the return channel 31, the change in width is maximized for the same channel length, thereby ensuring that the airflow rate is maintained while reducing the airflow velocity, thereby achieving the purpose of reducing noise.

[0113] By setting a guide plate 30B connected to the shell body 30A and located on one side of the air intake 14, the airflow flowing through the return channel 31 is guided, so that the airflow is more uniform and smooth and is directed to the fan 91 in the fan chamber 11, thereby reducing the impact of the airflow in the return channel 31 on the fan 91 in the fan chamber 11, thereby improving the working efficiency of the fan 91.

[0114] In some structural forms, the deflector plate 30B is arranged at an angle, and the distance between the deflector plate 30B and the air inlet 14 gradually increases in the direction away from the return outlet 33. The deflector plate 30B can be directly bent and connected to the housing body 30A, or the deflector plate 30B itself can be bent, so that the distance between the deflector plate 30B and the air inlet 14 gradually increases in the direction away from the return outlet 33. In other words, the deflector plate 30B is actually arranged away from the fan 91, thereby reducing the resonance between the fan 91 and the deflector plate 30B during transportation of the fan 91, thereby further reducing the noise during operation of the indoor unit 1 and improving the user experience.

[0115] In related technologies, a return channel is usually set up in the indoor unit in the air duct to reintroduce the airflow at the outlet side of the fan into the inlet side of the fan for pressurization. However, in this process, due to the gradient of upstream and downstream pressures in the return channel, a strong flow vortex appears at the tail of the return channel, resulting in a large noise generated by the ducted air conditioner, affecting the user experience.

[0116] In order to reduce the tail vortex noise of the return channel 31 during the use of the indoor unit 1 and improve the operating sound quality of the indoor unit 1 when in use, in conjunction with Figure 17, the guide plate 30B of the present application is provided with an uneven portion 30b at the end away from the return outlet 33, so that the uneven portion 30b can break up the flow vortex at the return outlet 33 of the return channel 31, reducing the number of flow vortices contained in the airflow, thereby weakening the intensity of the flow vortex, which is more conducive to the operation of the fan 91 in the fan chamber 11, and sending a more uniform and smooth airflow into the fan chamber 11, thereby improving the working efficiency of the indoor unit 1 and reducing the aerodynamic noise during the operation of the indoor unit 1, so as to enhance the user experience.

[0117] In some structural forms, the uneven portion 30b includes a tooth-like structure, which can effectively increase the contact area with the flow vortex, thereby improving the effect of breaking up the flow vortex. In another embodiment, the uneven portion 30b includes a wave-like structure, which can effectively increase the contact area with the flow vortex, thereby improving the effect of breaking up the flow vortex. It should be noted that the uneven portion 30b can be configured as a tooth-like structure, the uneven portion 30b can be configured as a wave-like structure, or the uneven portion 30b can be configured as a tooth-like structure or a wave-like structure.

[0118] Furthermore, when the uneven portion 30b includes a tooth-like structure, the tooth-like structure includes a plurality of sawteeth arranged in sequence along the axial direction of the fan chamber 11, with the roots of the plurality of sawteeth connected. Increasing the number of sawteeth in this manner further increases the area of ​​the tooth-like structure, further reducing the number of vortices contained in the airflow, thereby reducing aerodynamic noise during operation of the indoor unit 1 and improving the user experience.

[0119] In another embodiment, the tooth structure includes a plurality of saw teeth arranged in sequence along the axial direction of the fan chamber 11, with the tooth roots of the plurality of saw teeth spaced apart. Thus, the spacing of the tooth roots of the plurality of saw teeth can reduce the number of vortices contained in the airflow while reducing the overall weight of the tooth structure, thereby reducing the overall weight of the indoor unit 1.

[0120] Furthermore, in the axial direction of the fan chamber 11, the spacing between adjacent saw teeth in the middle is smaller than the spacing between adjacent saw teeth on the sides. It is understood that the air volume in the middle of the fan 91 located in the fan chamber 11 is generally greater than the air volume on the sides. Thus, the air volume in the middle of the fan 91 entering the return air duct is also greater than the air volume on the sides. As a result, the spacing between adjacent saw teeth in the middle is smaller than the spacing between adjacent saw teeth on the sides, that is, the multiple saw teeth in the middle are denser than the multiple saw teeth on the sides, thereby improving the effect of breaking up the flow vortices in the airflow.

[0121] In some structural forms, the end surface of the saw teeth away from the return outlet 33 is flat. That is, the surface away from the tooth tip and away from the tooth root is flat. This prevents the sharp end of the saw teeth from easily scratching the installer during installation, thereby improving installation safety, facilitating saw tooth processing, and improving processing efficiency.

[0122] Optionally, the shapes of the multiple serrations are the same, and the width of the serrations gradually decreases in the direction in which the guide plate 30B is away from the return outlet 33. Thus, the serrations are formed into a triangular shape, and the outer contour of the serrations can be formed into a triangle. The triangular serrations can be easily processed, and at the same time, the width of the end of the serration away from the return air outlet is smaller so that the flow vortex of the airflow will be broken up smaller, thereby achieving a better noise reduction effect. Of course, this embodiment is not limited to this, and the outer contour of the serrations can also be formed into a trapezoid, a semicircle, an ellipse, etc. The specific shape can be set by those skilled in the art according to needs.

[0123] Referring to Figures 18 and 19 , in some configurations, the second housing 30 further includes a grille 98, which is removably connected to the guide plate 30B and covers the air intake 14. The grille 98 is formed with multiple through-holes, through which air passing through the air intake 14 can enter the fan chamber 11. The grille 98 effectively prevents large foreign matter from entering the fan chamber 11 and potentially affecting the operation of the fan 91. The grille 98 is arranged in a grid pattern to maximize the size of the through-holes and minimize the impact on airflow. The grille 98 can be secured to the guide plate 30B via snaps or screws, facilitating both initial installation and subsequent removal for maintenance. This improves the stability of the grille 98 installation and eliminates the need for separate structures to connect the grille 98. This reduces the number of components in the air duct assembly 10 and reduces its size, leading to a more compact indoor unit 1. To further enhance the stability of the grille 98 connection, the grille 98 can also be connected to the first housing 20, further enhancing the stability of the grille 98 connection.

[0124] Optionally, the entire grille 98 can be arranged in an arc shape. Alternatively, the grille 98 can include a first grille and a second grille arranged at an angle, with the first grille connected to the first housing 20 and the second grille connected to the guide plate 30B. The first and second grilles can be integral structures, providing good integrity and ease of processing, or they can be separate structures connected by bolts or welding. The first and second grilles arranged at an angle are farther away from the fan 91, leaving ample space between the air inlet side 91a of the fan 91 and the grille 98, making it easier for the fan 91 to draw air.

[0125] With reference to Figures 15, 18, and 20, in some structural forms, the shell body 30A includes a volute 40, a diffuser lower shell 50, and a water receiving tray 60. The volute 40 and the diffuser lower shell 50 define the bottom surface of the diffuser chamber 12. The side of the volute 40 facing away from the fan chamber 11 cooperates with the diffuser lower shell 50 to form a return channel 31 and a return outlet 33. The guide plate 30B is connected to the diffuser lower shell 50. The return inlet 32 ​​of the return channel 31 is opened on the bottom surface of the diffuser chamber 12 and is located between the volute 40 and the diffuser lower shell 50 or within the diffuser lower shell 50.

[0126] It should be noted that the first housing 20 may include a fan chamber upper shell 21, a diffuser chamber upper shell 22, and a heat exchange chamber upper shell 23, which are connected in sequence. Thus, the fan chamber upper shell 21 cooperates with the volute 40 to define the fan chamber 11, and the diffuser chamber upper shell 22 cooperates with the volute 40 and the diffuser chamber lower shell 50 to define the diffuser chamber 12. The volute 40 and the diffuser chamber lower shell 50 define the bottom surface of the diffuser chamber 12, and the bottom surface of the diffuser chamber 12 is used to guide airflow to the heat exchange chamber 13. Furthermore, the fan chamber upper shell 21, the diffuser chamber upper shell 22, and the heat exchange chamber upper shell 23 may be an integrated structure to improve the connection strength of the three and reduce the number of assembly steps.

[0127] By arranging the return inlet 32 ​​between the volute 40 and the diffuser chamber lower shell 50 or on the diffuser chamber lower shell 50, when the airflow from the fan 91 is diverted by the volute 40 to flow to the diffuser chamber 12 and the side of the volute 40 close to the air inlet side 91a, the pressure of the airflow flowing into the diffuser chamber 12 after diversion increases, so that the airflow pressure at the return inlet 32 ​​is greater than the airflow pressure at the return outlet 33. Furthermore, due to the pressure difference between the return inlet 32 ​​and the return outlet 33, part of the airflow entering the diffuser chamber 12 is actively guided back through the return channel 31 to the air inlet side 91a of the volute 40 close to the fan 91 for further processing, making it easier for the airflow to enter the return inlet 32. The water receiving tray 60 is located below the heat exchanger 92, for receiving condensed water from the heat exchanger 92, and cooperates with the heat exchange chamber upper shell 23 of the first shell 20 to define the heat exchange chamber 13. Furthermore, the diffuser chamber lower shell 50 and the water receiving tray 60 can be integrally formed, making the connection between the two more secure and reducing the number of assembly steps, thereby improving assembly efficiency. Of course, in other structural forms, the diffuser chamber lower shell 50 and the water receiving tray 60 can be separate structures, and the two can be fixed together by a snap connection or a threaded connection, which is not limited in this application.

[0128] Further, with reference to Figures 17, 20, and 21, the diffuser chamber lower shell 50 includes a shell body 51 and a guide plate 52. The shell body 51 is connected to the volute tongue 40 and cooperates to define the bottom surface of the diffuser chamber 12. The guide plate 52 is detachably connected to the shell body 51 and is located on the side of the shell body 51 facing away from the diffuser chamber 12. The side of the volute tongue 40 facing away from the fan chamber 11 cooperates with the guide plate 52 to form the return flow channel 31 and the return flow outlet 33. The guide plate 30B is connected to the end of the guide plate 52 facing away from the shell body 51.

[0129] Among them, the shell body 51 is the main structure of the diffuser chamber lower shell 50, and the opposite sides of the shell body 51 are connected to the volute 40 and the water receiving tray 60. It should be noted that the volute 40 and the shell body 51 can be an integrated structure to improve the overall structural strength. Of course, the two can also be connected in a detachable manner such as screws or snaps. In this way, the appropriate volute 40 can be selected according to the specific air outlet conditions of the fan 91, or when the volute 40 needs to be maintained, the maintenance personnel can also disassemble and assemble it. The reflow channel 31 is formed by the volute 40 and the guide plate 52 of the diffuser chamber lower shell 50, that is, the reflow channel 31 is formed by the split structural design, so that the shape of the reflow channel 31 can be easily changed by disassembly and assembly, so that the structural dimensions of the reflow channel 31 can be accurately controlled, and the channel structure can be simplified and easy to open the mold. To improve the stability of the return channel 31, in the present application, when a reinforcing rib 311 is provided on the surface of the volute tongue 40 facing the guide plate 52, a hook 3111 can be provided at the end of the reinforcing rib 311. A button hole 52a is provided on the surface of the guide plate 52 facing the volute tongue 40. The hook 3111 engages with the button hole 52a to secure the position of the volute tongue 40 and the guide plate 52. Of course, the volute tongue 40 and the guide plate 52 can also be secured by other means such as screws, and the specific method can be selected by those skilled in the art. It is worth noting that the structural shape of the guide plate 52 is not limited. For example, it can be a curved guide plate 52 or a flat guide plate 52. When the guide plate 52 is a curved guide plate 52, the diversion effect can be improved. When the guide plate 52 is a flat guide plate 52, the processing difficulty can be reduced.

[0130] Furthermore, the guide plate 30B and the guide plate 52 are integrally formed, for example, by integral injection molding, which can improve the firmness of the connection between the two and reduce the number of assembly steps.

[0131] In addition, it should be noted that the guide plate 52 can be fixed or movable.

[0132] For example, when the deflector 52 is fixed, the installation angle can be pre-designed (e.g., it can be tilted at a certain angle) to more effectively control the direction of the airflow outflowing from the return outlet 33 and ensure air volume. The deflector 52 and the housing body 51 are thus integrally structured. For example, by integral injection molding, this can improve the connection between the two and reduce the number of assembly steps.

[0133] When the guide plate 52 is movable, the guide plate 52 can be elastically swingable, that is, the guide plate 52 can be elastically swingable through the elastic part, so that the elasticity can be used to adapt to different speeds to increase the pressure on the side of the volute 40 close to the air inlet side 91a of the fan 91, thereby reducing costs and achieving good adjustable effects.

[0134] Furthermore, the deflector 52 includes a second connecting portion 521 and a second guide portion 522, which are connected to each other. The second connecting portion 521 is detachably connected to the shell body 51. The second guide portion 522 cooperates with the side of the volute tongue 40 facing away from the fan 91 to form the return channel 31 and the return outlet 33. The second connecting portion 521 and the shell body 51 can be connected by screws or snaps. The second connecting portion 521 can be configured as a flat plate and fit against the bottom surface of the shell body 51, thereby increasing the contact area between the two and improving the stability of the connection. The second guide portion 522 is used to cooperate with the volute tongue 40 to form the return channel 31 and the return outlet 33. The second guide portion 522 can be configured as an arc-shaped plate to facilitate guiding the direction of the airflow.

[0135] 17 , in some configurations, the outer wall of the volute tongue 40 includes a guide surface 41 and a diffuser surface 42. The guide surface 41 is configured to guide the airflow within the fan chamber 11 into the diffuser chamber 12. The guide surface 41 extends from the side of the volute tongue 40 facing the fan chamber 11 to the diffuser chamber 12. The diffuser surface 42 is connected between the guide surface 41 and the top surface of the diffuser chamber lower shell 50. The diffuser surface 42 and the top surface of the diffuser chamber lower shell 50 together form the bottom surface of the diffuser chamber 12. The top surface of the diffuser chamber lower shell 50 defines a return inlet 32.

[0136] Among them, the guide surface 41 can be set in an arc surface to change the direction of the airflow to reduce airflow loss. The diffuser surface 42 can be set coplanar with the top surface of the diffuser chamber lower shell 50 so that the airflow can flow smoothly and reduce losses. By limiting the return inlet 32 ​​to be directly opened on the top surface of the diffuser chamber lower shell 50, the processing and manufacturing of the return inlet 32 ​​is more convenient, and the shape is easy to control, thereby ensuring the air intake of the return inlet 32 ​​and facilitating the subsequent maintenance and replacement of the return inlet 32. In addition, the diffuser chamber lower shell 50 forms a guide slope at the return inlet 32 ​​to further improve the airflow from the return inlet 32 ​​into the return channel 31.

[0137] Third embodiment:

[0138] The third embodiment of the present application proposes a HVAC system. In the third embodiment of the present application, the HVAC system includes but is not limited to equipment such as air conditioners, multi-split units, and heat pumps, and can be used in large-scale places such as shopping malls and office buildings. The HVAC system may include an indoor unit 1, an outdoor unit, and a connecting pipe. The indoor unit 1 is connected to the outdoor unit through a connecting pipe so that a refrigerant circulation is formed between the indoor unit 1 and the outdoor unit. In some actual usage scenarios, the indoor unit 1 of the present application can be installed indoors, the outdoor unit is responsible for cooling or heating, and transports the refrigerant through the connecting pipe. The refrigerant exchanges heat with the indoor air and the outdoor air respectively, and the indoor unit 1 is responsible for transporting cold air or hot air into the room to achieve the effect of cooling or heating.

[0139] Please refer to Figures 18 and 19. Specifically, the indoor unit 1 can include, but is not limited to, a duct unit, a wall-mounted air conditioner indoor unit, and a floor-standing air conditioner indoor unit. Duct units are typically installed on the ceiling using a suspended ceiling and can be hidden within the ceiling. This makes them more concealed and aesthetically pleasing compared to other indoor unit 1 structures. Furthermore, duct units use a decentralized air outlet, providing a more comfortable airflow. The indoor unit 1 may include an air duct assembly 10, a fan 91, a heat exchanger 92, and an electrical control box assembly.

[0140] The air duct assembly 10 is used to construct an air duct for the indoor unit 1 to facilitate air flow. The outer contour of the air duct assembly 10 can be longitudinally shaped. The air duct assembly 10 sequentially defines a fan chamber 11, a diffuser chamber 12, and a heat exchange chamber 13, which are interconnected. The air duct assembly 10 also defines a return air port 14A connected to the fan chamber 11 and an air outlet 15A connected to the heat exchange chamber 13.

[0141] It is understandable that the fan chamber 11 is configured to accommodate the fan 91. The diffuser chamber 12 is used to receive the airflow blown from the fan chamber 11 and diffuse it to increase the pressure and flow of the airflow, so as to improve the cooling or heating effect. The heat exchange chamber 13 is configured to accommodate the heat exchanger 92. In this way, the external airflow can flow in from the return air port 14A under the action of the fan 91, and flow through the fan chamber 11, the diffuser chamber 12 and the heat exchange chamber 13 in turn, so as to heat the heat exchanger 92 in the heat exchange chamber 13, and then flow out from the air outlet 15A to achieve heating or cooling of the external airflow.

[0142] The air duct assembly 10 includes a first shell 20 and a second shell 30. The first shell 20 and the second shell 30 cooperate to define a connected diffuser chamber 12, a fan chamber 11, and a heat exchange chamber 13. The first shell 20 and the second shell 30 can be made of alloys or metals such as aluminum or steel to meet requirements such as structural strength and long service life. Of course, the first shell 20 and the second shell 30 can also be made of plastic to meet requirements such as light weight, and this application does not impose any restrictions on this. Of course, it is also possible to use a combination of one of the first shell 20 and the second shell 30 using an alloy or metal material and the other using a plastic material.

[0143] It should be noted that the first shell 20 and the second shell 30 can serve as a shell, so there is no need to set up additional structures such as other shells, thereby reducing the number of structures in the air duct assembly 10 and reducing the volume of the air duct assembly 10, thereby miniaturizing the air duct unit to adapt to more use environments with relatively compact installation space. Of course, in other embodiments, the indoor unit 1 may also include a shell, which can be configured to cover the outer surfaces of the first shell 20 and the second shell 30, leaving only the air outlet 15A and the return air outlet 14A exposed for communication with the outside world, thereby protecting the first shell 20 and the second shell 30.

[0144] The first shell 20 may include an upper cover 21A and two side panels 70, the two side panels 70 are connected to opposite sides of the upper cover 21A along its width direction, the upper cover 21A includes a fan chamber shell 211, a diffuser chamber top shell 212 and a heat exchange chamber top shell 213 connected in sequence, and the second shell 30 includes a connected volute tongue 40, a diffuser chamber bottom shell 50A and a water receiving tray 60, and the opposite sides of the diffuser chamber bottom shell 50A are respectively connected to the volute tongue 40 and the water receiving tray 60.

[0145] The fan chamber shell 211 of the first housing 20 defines the fan chamber 11, and the diffuser chamber top shell 212, the volute tongue, and the diffuser chamber bottom shell 50A of the first housing 20 cooperate to define the diffuser chamber 12. Furthermore, the fan chamber shell 211, the diffuser chamber top shell 212, and the upper shell of the heat exchange chamber 13 can be an integrated structure to improve the connection strength of the three and reduce the number of assembly steps.

[0146] The water tray 60 is located below the heat exchanger 92 and is used to receive condensed water flowing out of the heat exchanger 92. It cooperates with the heat exchange chamber top shell 212 of the first housing 20 to define the heat exchange chamber 13. Furthermore, the diffuser chamber bottom shell 50A and the water tray 60 can be a one-piece structure, making the connection between the two more secure and reducing assembly steps to improve assembly efficiency. Of course, in other structural forms, the diffuser chamber bottom shell 50A and the water tray 60 can be separate structures, and the two can be secured via a snap-fit ​​connection or a threaded connection, which is not limited in this application.

[0147] The fan 91 is housed in the fan cavity 11 and includes a wind wheel and a motor. The wind wheel is housed in the fan cavity 11, the motor is installed in the air duct assembly 10, and the output shaft of the motor is connected to the wind wheel to drive the wind wheel to rotate. The wind wheel can be arranged in a cylindrical strip shape. The fan 91 can be a cross-flow fan, a centrifugal fan or an axial flow fan, etc. When the fan 91 is configured as a cross-flow fan, the cross-flow fan has the advantages of small radial size, low speed, low noise, uniform air output, etc. Its axial length can be arbitrarily lengthened without affecting the gas flow state, etc., and compared with centrifugal fans or axial flow fans, the cost of cross-flow fans is lower. The fan 91 can be arranged opposite the return air port 14A so that the external air flow can flow to the fan 91 through the return air port 14A in a shorter path, reducing losses during the flow process.

[0148] The heat exchanger 92 can have a variety of shapes, such as straight, V-shaped, curved, or wavy. The heat exchanger 92 is used to exchange heat with the gas flowing through the heat exchange chamber 13 and passing through the heat exchanger 92, thereby cooling or heating the gas. For example, a plurality of refrigerant pipes are provided within the heat exchanger 92. When the gas passes through the heat exchanger 92, it exchanges heat with the refrigerant within the pipes, thereby changing the gas temperature. Specifically, during cooling, the gas exchanges heat with the refrigerant in the heat exchanger 92 to form low-temperature air; while during heating, the gas exchanges heat with the refrigerant in the heat exchanger 92 to form heated air.

[0149] The electrical control box assembly can be mounted on the surface of the air duct assembly 10 to achieve fixed installation. The electrical control box assembly can be electrically connected to the motor of the fan 91 and the heat exchanger 92, respectively, to control or regulate the fan 91 and the heat exchanger 92. For example, when the temperature in the environment where the duct unit is operating reaches a set value, the electrical control box assembly can send a command to shut down the motor and the heat exchanger 92, thereby reducing energy consumption and preventing the indoor temperature from being too low or too high.

[0150] Furthermore, the electrical control box assembly can be installed on the surface of the diffusion chamber bottom shell 50A of the second shell 30 facing away from the diffusion chamber 12, and be arranged adjacent to the return air outlet 14A and facing the return air outlet 14A. In this way, maintenance personnel can directly disassemble and assemble the electrical control box assembly at a position adjacent to the return air outlet 14A. Since there is no other structure blocking the area adjacent to the return air outlet 14A, it is more convenient for maintenance personnel to operate when disassembling and assembling the electrical control box assembly.

[0151] In some configurations, the indoor unit 1 further includes a grille 98, which may be installed at the return air inlet 14A. The grille 98 prevents users or maintenance personnel from touching the impeller of the fan 91, reducing the risk of injury from accidentally touching the impeller blades. The grille 98 also blocks external debris, preventing it from entering the fan chamber 11 and heat exchange chamber 13 and potentially affecting the impeller of the fan 91 and the heat exchanger 92. This can extend the service life of the indoor unit 1.

[0152] Please refer to Figures 19 to 21. In order to improve the gas flow performance during use of the indoor unit 1 of the HVAC system, the second shell 30 of the present application is provided with a return channel 31. The bottom surface of the pressure diffuser chamber 12 includes a first portion 1211 and a second portion 1212. The first portion 1211 and the second portion 1212 are arranged side by side along the width direction of the air duct assembly 10. Taking the fan 91 as a cross-flow fan as an example, when the indoor unit 1 faces a high back pressure working condition, the eccentric vortex intensity of the cross-flow fan's impeller along its axial direction will be inconsistent, so that when the airflow delivered by the impeller of the cross-flow fan flows through the first portion 1211 and the second portion 1212, the flow rate of the airflow flowing through the second portion 1212 is lower than the flow rate of the airflow in the first portion 1211. In addition, in the embodiment of the present application, the return inlet 32 ​​of the return channel 31 is opened in the first portion 1211, and the return outlet 33 is connected to the fan chamber 11. Based on this, the present application has the following technical effects:

[0153] The airflow delivered by the impeller of the fan 91 will be diverted by the second shell 30, wherein part of the airflow flows to the gap between the second shell 30 and the impeller of the fan 91, and then flows back to the impeller of the fan 91 in the fan cavity 11; while the other part of the airflow flows to the diffuser cavity 12, and the pressure of the airflow flowing into the diffuser cavity 12 becomes larger, so that the airflow pressure at the return inlet 32 ​​is greater than the airflow pressure at the return outlet 33, and then through the pressure difference between the return inlet 32 ​​and the return outlet 33, part of the airflow entering the diffuser cavity 12 is actively guided back to the fan cavity 11 through the return channel 31, so that the airflow can flow back to the impeller of the fan 91 through two paths, so as to stabilize the eccentric vortex of the impeller of the fan 91, thereby improving the air supply effect of the fan 91 and making the fan 91 rotate more smoothly, thereby reducing the noise and vibration of the fan 91. Moreover, on the basis of keeping the total reflux volume unchanged, by adding the reflux channel 31, the flow rate of the airflow reflux through the gap between the second shell 30 and the wind wheel of the fan 91 can be relatively reduced, thereby avoiding that this part of the airflow is too close to the wind wheel of the fan 91, resulting in excessive pressure pulsation in the second shell 30, thereby reducing the impact of the airflow on the second shell 30, reducing the noise generated between the wind wheel of the fan 91 and the second shell 30, and reducing the vibration of the wind wheel of the fan 91.

[0154] Next, because the airflow through the second portion 1212 has a relatively slow velocity, airflow blockage may occur in the area near the second portion 1212. If the return inlet 32 ​​is located in the second portion 1212, the airflow through the second portion 1212 cannot flow smoothly into the return inlet 32, and thus cannot effectively return through the return channel 31. Therefore, in the embodiment of the present application, the return inlet 32 ​​is only located in the first portion 1211, so that the airflow flowing to the diffuser chamber 12 can flow into the return channel 31 through the inlet of the return channel 31 and then flow out through the outlet of the return channel 31, thereby stabilizing the eccentric vortex of the wind wheel of the fan 91.

[0155] Please refer to FIG. 20 to FIG. 22 . In some embodiments, the fan 91 is a cross-flow fan. The second portion 1212 includes two second portions 1212 located on opposite sides of the first portion 1211 in the width direction of the air duct assembly 10 . It can be understood that when the indoor unit 1 is a duct unit, a cross-flow fan can be selected as the fan 91 of the fan 91; in some duct unit usage scenarios, for example, when the return air outlet on the ceiling and the return air outlet 14A of the duct assembly 10 are installed misaligned, or when the grille 98 covering the return air outlet on the ceiling is blocked by foreign objects, the duct unit will be in a high back pressure condition. Under the high back pressure condition, the eccentric vortices at both ends of the cross-flow fan's impeller along its axial direction will be less stable than the eccentric vortex in the middle of the cross-flow fan's impeller along its axial direction. Therefore, the bottom surface of the diffusion chamber 12 will accordingly include two second parts 1212 and a first part 1211, and the second part 1212 is located on opposite sides of the first part 1211.

[0156] Referring to Figures 22 and 23 , the distance L between the return inlet 32 ​​and the outer edge of the second portion 1212 is greater than 35 mm. This allows the return inlet 32 ​​to maintain a certain distance from the second portion 1212 as much as possible, preventing the return inlet 32 ​​in the return channel 31 from being too close to the second portion 1212 and thus affecting the return flow effect of the return channel 31. For example, the distance L between the return inlet 32 ​​and the outer edge of the second portion 1212 can be 35 mm, 37 mm, 40 mm, 42 mm, or 55 mm, etc., and is not limited to this embodiment of the present application.

[0157] Please refer to Figures 20 to 22. In some structural forms, the number of the return inlets 32 is at least two, and the at least two return inlets 32 are arranged at intervals in the direction of the airflow flow. It is understandable that the airflow delivered by the impeller of the cross-flow fan will have an airflow direction on the basis of flowing through the first part 1211. The embodiment of the present application is provided with at least two return inlets 32, which can increase the number of return inlets 32 to better improve the airflow rate returning to the fan chamber 11 through the return air duct, and at least two return inlets 32 are arranged at intervals in the direction of the airflow flow, so that the at least two return inlets 32 can be arranged in multiple areas of the first part 1211 to further improve the return airflow rate. For example, the number of return inlets 32 can be two, three or four, etc., and the embodiment of the present application is not limited to this. In other structural forms, the area of ​​the return inlet 32 ​​can be increased based on the area of ​​the original return inlet 32, and the volume of the return channel 31 can be increased accordingly. This can also increase the return airflow flow rate and thus improve the return effect.

[0158] Please refer to Figures 20 to 22 . Furthermore, the length of the return inlet 32 ​​located downstream in the direction of airflow is shorter than the length of the return inlet 32 ​​located upstream in the direction of airflow. This allows the shorter return inlet 32 ​​located downstream to serve as an auxiliary inlet, precisely aligning with the area with a higher flow rate of air flowing through the first portion 1211. This prevents the return inlet 32 ​​located downstream from being too long, which could cause the airflow with a lower flow rate to flow back through the first portion 1211. This ensures a more uniform air supply from the air outlet 15A of the indoor unit 1, improving the air output efficiency of the indoor unit 1.

[0159] Please refer to Figures 21 to 23. In order to improve the return flow effect of the return channel 31, the end of the return inlet 32 ​​located downstream in the airflow direction should extend beyond the end of the return inlet 32 ​​located upstream in the airflow direction in the width direction of the air duct assembly 10. In this way, the return inlet 32 ​​located upstream and the return inlet 32 ​​located downstream can cooperate to occupy more area of ​​the first portion 1211, fully and evenly utilizing the airflow flowing through the first portion 1211 in the width direction of the air duct assembly 10 for return flow, avoiding concentrated utilization of the airflow flowing through the same area of ​​the first portion 1211 for return flow, thereby ensuring uniform air supply to the subsequent indoor unit 1.

[0160] The width of the return inlet 32 ​​located downstream in the direction of airflow is greater than or equal to the width of the return inlet 32 ​​located upstream in the direction of airflow. Similarly, the return inlet 32 ​​located downstream can be used as an auxiliary inlet to accurately correspond to the area with a large airflow flow through the first portion 1211. If the airflow flow through the first portion 1211 is relatively large, the width of the return inlet 32 ​​located downstream should be greater than the width of the return inlet 32 ​​located upstream; if the airflow flow through the first portion 1211 is relatively small, the width of the return inlet 32 ​​located downstream can be equal to the width of the return inlet 32 ​​located upstream. Therefore, by adjusting the width of the return inlet 32 ​​located downstream to adapt to the actual flow field conditions, the air supply effect of the air outlet 15A of the indoor unit 1 is made more uniform, thereby improving the air outlet effect of the indoor unit 1.

[0161] Please refer to Figures 21 and 22 in conjunction. In some embodiments, at least two return inlets 32 are arranged at intervals along the width direction of the air duct assembly 10. In this way, by increasing the number of return inlets 32, the airflow rate returning to the fan chamber 11 through the return air duct can be effectively improved. In addition, the at least two return inlets 32 are arranged at intervals along the width direction of the air duct assembly 10, so that the at least two return inlets 32 can be arranged in multiple areas of the first portion 1211 along the width direction of the air duct assembly 10, thereby further improving the return airflow rate. For example, the number of return inlets 32 can be two, three, or four, etc., and this embodiment of the present application is not limited to this.

[0162] Please refer to Figures 19 and 20. In some structural forms, the return inlet 32 ​​is set to be gradually contracted from the outside to the inside. In this way, when the airflow flowing through the first part 1211 flows into the return inlet 32 ​​from the return inlet 32, the flow rate of the airflow will gradually increase, and the dynamic pressure will also gradually increase, so that the airflow can enter the return channel 31 more smoothly, reduce the generation of turbulence, and then make the airflow have a more stable flow state, reducing the noise and vibration caused by the unstable flow state of the gas. Of course, in other structural forms, the size of the return inlet 32 ​​can be equal from the outside to the inside, or the return inlet 32 ​​can be set to be gradually expanded from the outside to the inside, and the embodiments of the present application are not limited to this.

[0163] Furthermore, the connection between the wall of the return inlet 32 ​​and the first portion 1211 forms a smooth transition. Thus, as the airflow flows from the first portion 1211 into the return channel 31, the smooth transition creates less resistance to the airflow as it passes through the connection between the wall of the return inlet 32 ​​and the first portion 1211. This allows the airflow to flow more smoothly, reducing noise caused by friction between the wall of the return inlet 32 ​​and the first portion 1211. Of course, in other structural forms, the connection between the wall of the return inlet 32 ​​and the first portion 1211 may form a sharp transition, and this embodiment of the present application is not limited thereto.

[0164] Please refer to Figures 18 to 21. In some structural forms, the first shell 20 may include a fan chamber shell 211, a diffuser chamber top shell 212 and a heat exchange chamber top shell 213 connected in sequence, and the second shell 30 includes a connected volute tongue 40, a diffuser chamber bottom shell 50A and a water receiving tray 60.

[0165] The fan chamber housing 211 defines the fan chamber 11, and the diffuser chamber top housing 212 cooperates with the volute tongue 40 and the diffuser chamber bottom housing 50A to define the diffuser chamber 12. The volute tongue 40 and the diffuser chamber bottom housing 50A define the bottom surface of the diffuser chamber 12, and the bottom surface of the diffuser chamber 12 is used to guide airflow to the heat exchange chamber 13. Furthermore, the fan chamber housing 211, the diffuser chamber top housing 212, and the upper housing of the heat exchange chamber 13 can be an integrated structure to improve the connection strength of the three and reduce the number of assembly steps.

[0166] The water tray 60 is located below the heat exchanger 92, receiving condensed water from the heat exchanger 92 and cooperating with the upper shell of the heat exchange chamber 13 of the first housing 20 to define the heat exchange chamber 13. Furthermore, the diffuser chamber bottom shell 50A and the water tray 60 can be integrally formed, making the connection more secure and reducing assembly steps to improve assembly efficiency. Of course, in other structural forms, the diffuser chamber bottom shell 50A and the water tray 60 can be separate structures, and the two can be secured via a snap-fit ​​or threaded connection, which is not limited in this application.

[0167] Referring to Figures 19 to 21 , in some embodiments, the outer wall of the volute tongue 40 includes a guide surface 41 and a diffuser surface 42. The guide surface 41 is configured to guide airflow within the fan chamber 11 into the diffuser chamber 12. The guide surface 41 extends from the side of the volute tongue 40 facing the wind wheel of the fan 91 to the diffuser chamber 12. The diffuser surface 42 connects between the guide surface 41 and the top surface of the diffuser chamber bottom shell 50A. The diffuser surface 42 and the top surface of the diffuser chamber bottom shell 50A together form the bottom surface of the diffuser chamber 12. The guide surface 41 can be curved to significantly change the direction of the airflow and reduce airflow losses. The diffuser surface 42 can be coplanar with the top surface of the diffuser chamber bottom shell 50A to ensure smooth airflow and reduce losses.

[0168] Based on this, the location of the reflux inlet 32 ​​may include but is not limited to the following:

[0169] In the first embodiment, a return inlet 32 ​​is provided on the top surface of the diffuser chamber bottom shell 50A (as shown in Figures 19 and 20). By defining the return inlet 32 ​​as being directly provided on the top surface of the diffuser chamber bottom shell 50A, the return inlet 32 ​​is easier to manufacture and the shape is easier to control, thereby ensuring the air intake of the return inlet 32 ​​and facilitating subsequent maintenance and replacement of the return inlet 32.

[0170] Furthermore, the return inlet 32 ​​is located on the top surface of the diffuser chamber bottom shell 50A, closer to the diffuser surface 42 than to the guide surface 41. For example, the distance between the return inlet 32 ​​and the intersection of the guide surface 41 and the diffuser surface 42 is less than one-quarter of the length of the top surface of the diffuser chamber bottom shell 50A. Since the airflow velocity on the diffuser surface 42 is relatively low and the pressure is relatively high, the return inlet 32 ​​is positioned near the diffuser surface 42. This allows the airflow to be better drawn into the return inlet 32 ​​under the action of pressure, reducing air volume loss and allowing the airflow to flow more quickly and stably toward the return outlet 33. This improves the air intake efficiency of the return channel 31, enhances the gas flow performance within the return channel 31, enhances the pressure resistance of the return channel 31, and thereby increases the airflow rate through the return channel 31.

[0171] In the second embodiment, the return inlet 32 ​​is formed by the connection between the diffuser surface 42 and the top surface of the diffuser chamber bottom shell 50A. It will be appreciated that in this embodiment, the return inlet 32 ​​is formed by the connection between the diffuser surface 42 and the top surface of the diffuser chamber bottom shell 50A. This effectively prevents the return inlet 32 ​​from being independently provided on the diffuser chamber bottom shell 50A or the volute tongue 40, which would result in a lower structural strength, thereby ensuring the structural stability of the diffuser chamber bottom shell 50A or the volute tongue 40.

[0172] In the third form, the diffuser surface 42 is provided with a return inlet 32. This makes the return inlet 32 ​​easier to manufacture and easier to shape, thereby ensuring the air intake of the return inlet 32 ​​and facilitating later maintenance and replacement of the return inlet 32.

[0173] It should be noted that, based on the fact that the number of the reflux inlets 32 is at least two and the setting form of the reflux inlets 32 can be the above three setting forms, each reflux inlet 32 ​​of the present application can uniformly adopt any one of the above three setting forms, or one reflux inlet 32 ​​can adopt one setting form, and the embodiments of the present application do not limit this.

[0174] The above content introduces the advantage of the return channel 31 of the air duct assembly 10 of the present application having a better return effect from the specific setting form of the return inlet 32. On this basis, please refer to Figures 19 to 21. In order to further improve the flow efficiency of the airflow when it flows through the return channel 31, the return outlet 33 of the embodiment of the present application can be gradually expanded from the inside to the outside. In this way, through the gradual expansion of the return outlet 33, when the airflow in the return channel 31 flows through the return outlet 33, the size of the return outlet 33 gradually increases, so that the flow area of ​​the return outlet 33 for the airflow increases, thereby allowing more airflow to leave the return channel 31 and enter the fan chamber 11, effectively improving the flow efficiency of the airflow and optimizing the flow state of the airflow.

[0175] Please continue to refer to Figures 19 to 21. Further, the connection between the mouth wall of the return outlet 33 and the wall surface of the second shell 30 is in a smooth transition. In this way, when the airflow flows from the return channel 31 into the fan chamber 11, when the airflow flows through the connection between the mouth wall of the return outlet 33 and the wall surface of the second shell 30, the smooth transition connection has less resistance to the airflow, allowing the airflow to flow more smoothly, reducing the noise caused by the friction between the airflow and the connection between the mouth wall of the return outlet 33 and the wall surface of the second shell 30. Of course, in other structural forms, the connection between the mouth wall of the return outlet 33 and the wall surface of the second shell 30 can be a sharp transition, and the embodiments of the present application are not limited to this.

[0176] Referring to Figure 19 , in some embodiments, the return flow channel 31 passes through the rotor of the fan 91 at an extension line L0 of the return flow outlet 33 and forms an angle θ with the outer tangent line L1 of the rotor of the fan 91, where θ is less than or equal to 15 degrees and greater than or equal to 0 degrees. This ensures that the airflow stabilizes the eccentric vortices of the rotor of the fan 91 while preventing excessive impact of the airflow on the rotor of the fan 91 and noise. When θ is greater than 15 degrees, the airflow can impact the rotor of the fan 91 too strongly, causing the fan 91 to vibrate and generate noise. When θ is less than 0 degrees, the airflow's supplementary effect on the rotor of the fan 91—that is, the airflow's effectiveness in stabilizing the eccentric vortices of the rotor of the fan 91—is less effective. For example, θ can be 0 degrees, 2 degrees, 5 degrees, 7 degrees, 10 degrees, 12 degrees, or 15 degrees, among others, and is not limited in this embodiment of the present application.

[0177] Continuing with FIG19 , further, θ is equal to 0 degrees. Thus, the extended line L0 of the return channel 31 at the return outlet 33 coincides with the outer peripheral tangent line L1 of the fan 91 , thereby stabilizing the eccentric vortex of the fan 91 through the return outlet 33 while preventing the airflow from impacting the fan 91 and generating noise.

[0178] Referring to Figure 19 , in some embodiments, the return channel 31 extends from the return outlet 33 toward the outer side of the rotor of the fan 91, and forms an angle β with the outer peripheral tangent line L1 of the rotor of the fan 91, with β being less than or equal to 45 degrees and greater than or equal to 0 degrees. This ensures that the airflow stabilizes the eccentric vortices of the rotor of the fan 91 while preventing excessive impact of the airflow on the rotor of the fan 91, which could cause noise. When β is less than 0 degrees, the airflow can impact the rotor of the fan 91 too strongly, causing vibration and noise. When θ is greater than 0 degrees, the airflow's supplementary effect on the rotor of the fan 91 is reduced, meaning that the airflow's effectiveness in stabilizing the eccentric vortices of the rotor of the fan 91 is less effective. For example, β can be 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 45 degrees, and so on, though this is not a limitation in the present embodiment.

[0179] Continuing to refer to FIG. 19 , further, β is equal to 0 degrees. Thus, the extended line L0 of the return channel 31 at the return outlet 33 coincides with the outer peripheral tangent line L1 of the fan rotor of the fan 91. This allows the airflow flowing out of the return outlet 33 to stabilize the eccentric vortex of the fan rotor of the fan 91 while preventing the airflow from impacting the fan 91 and generating noise.

[0180] In some structural forms, the return channel 31 is arranged in a curved shape. Specifically, the return channel 31 can be arranged in a curved shape, such as an arc or a wavy line, which can slow down the impact speed of the airflow within the return channel 31, further reducing airflow noise and stabilizing airflow. It should be noted that in other embodiments, the return channel 31 can also be arranged in a straight line, thereby increasing air volume at the same fan 91 speed. Alternatively, the return channel 31 can be a combination of a straight line and a curve, and the specific selection can be made by those skilled in the art according to their needs.

[0181] Referring to Figures 24 to 26 , in some embodiments, the return outlet 33 includes a plurality of return sub-outlets 181 spaced apart along the width of the second housing 30. Thus, the airflow flowing out of the return sub-outlets 181 of the return channel 31 can evenly stabilize the eccentric vortex of the impeller of the fan 91 across the width of the second housing 30, ultimately improving the uniformity of air delivery from the impeller of the fan 91 in its axial direction.

[0182] Please refer to Figure 27. Optionally, the return outlet 33 can be extended along the width direction of the second shell 30. In this way, the eccentric vortex of the wind wheel of the fan 91 can be stabilized evenly in the width direction of the second shell 30, thereby ultimately improving the uniformity of the air supply of the wind wheel of the fan 91 in its axial direction.

[0183] Fourth embodiment:

[0184] The fourth embodiment of the present application provides a HVAC device, which includes an indoor unit and an outdoor unit. The indoor unit and the outdoor unit are connected by cables, pipes, etc., so as to jointly operate to regulate the indoor environment.

[0185] As can be understood, the indoor unit is installed indoors and is typically mounted on a ceiling to supply air to the room. Figures 32 to 34 illustrate the structure of an indoor unit 1 according to an embodiment of the present application. The indoor unit 1 includes an air duct assembly 10, a fan 91, a heat exchanger 92, and an electrical control box assembly 93.

[0186] The air duct assembly 10 is used to construct an air duct suitable for the indoor unit 1 for air flow. Specifically, the air duct assembly 10 includes a housing, the outer contour of which can be roughly rectangular. As shown in Figure 3, an air flow channel is formed in the housing. The air flow channel includes a fan chamber 11 and a pressure diffuser chamber 12. The fan chamber 11 has a return air area 111 and a first transition area 112. The pressure diffuser chamber 12 is arranged corresponding to the first transition area 112. The area of ​​the pressure diffuser chamber 12 away from the fan chamber 11 forms a second transition area 121A. The air flow channel also includes a heat exchange chamber 13. The heat exchange chamber 13 is arranged corresponding to the second transition area 121A. The area of ​​the heat exchange chamber 13 away from the pressure diffuser chamber 12 forms an air outlet area 131.

[0187] The fan 91 is arranged in the fan chamber 11. The fan 91 drives the external air flow from the return air area 111 into the fan chamber 11, and works on it so that it flows at a faster flow rate through the first transition area 112 to the diffuser chamber 12, providing power for the gas circulation of the above-mentioned air duct, so that the air flow can flow through the second transition area 121A of the diffuser chamber 12 to the heat exchange chamber 13, and flow out of the air flow channel through the air outlet area 131 of the heat exchange chamber 13. As shown in Figure 3, the direction indicated by the dotted arrow is the direction of the air flow in the air flow channel.

[0188] Heat exchanger 92 is housed within heat exchange chamber 13 and is used to exchange heat with the gas flowing through heat exchange chamber 13 and passing through heat exchanger 92, thereby cooling or heating the gas. For example, heat exchanger 92 is provided with multiple refrigerant pipes. As the gas passes through heat exchanger 92, it exchanges heat with the refrigerant within the pipes, thereby reducing its temperature and forming low-temperature air. To increase the heat exchange area of ​​heat exchanger 92, heat exchanger 92 can be configured in a V-shape, an arc shape, or a wavy shape, and can be composed of a single heat exchange fin or a combination of multiple heat exchange fins.

[0189] The electrical control box assembly 93 houses an electrical control board assembly, which integrates various electronic components. These components are used to electrically connect to the fan 91 and other devices, and to provide overall control over the operation of the indoor unit 1. Inevitably, these electronic components generate considerable heat during operation. In this embodiment, the electrical control box assembly 93 can be mounted within the housing of the air duct assembly 10 or positioned proximate to the airflow path to dissipate heat from the electrical control box assembly 93 to a certain extent.

[0190] The shell of the air duct assembly 10 includes a first shell 20 and a second shell 30. The first shell 20 is connected to the second shell 30 to form an air flow channel having an upper fan chamber 11, a pressure diffuser chamber 12 and a heat exchange chamber 13. The first shell 20 and the second shell 30 can be respectively made of metal materials such as aluminum alloy or stainless steel to meet the requirements of high strength and corrosion resistance. Alternatively, the first shell 20 and the second shell 30 can also be made of plastic materials to achieve lightweight shells. This application does not impose any restrictions on this. For example, the shell can be a combination of a first shell 20 made of metal and a second shell 30 made of plastic. In addition, the embodiment of the present application does not limit the connection method of the first shell 20 and the second shell 30. They can be connected individually or in combination by means of snap-on, riveting, welding and bolting.

[0191] The shell has a volute tongue 40 located at the junction of the fan chamber 11 and the diffuser chamber 12, and a return channel 31 located on the side of the volute tongue 40 away from the air flow channel. The fan chamber 11 is provided with a fan 91, and the fan 91 drives the external air flow into the fan chamber 11. The volute tongue 40 guides at least part of the air flow from the fan chamber 11 into the diffuser chamber 12. The return channel 31 connects the diffuser chamber 12 and the fan chamber 11, guiding at least part of the air flow from the diffuser chamber 12 back to the fan chamber 11. As shown in Figures 35 and 36 , the housing of the air duct assembly of the embodiment of the present application includes at least a head 40A and a first plate 51A. The portion of the head 40A facing the airflow channel is at least configured as a volute 40. The first plate 51A extends downstream of the airflow and is part of the first housing 20. A portion of the second housing 30 of the indoor unit 1 and the head 40A define a fan chamber 11. Another portion of the second housing 30 of the indoor unit 1, the head 40A, and the first plate 51A define a diffuser chamber 12. The first housing 20 of the indoor unit 1 also includes a water receiving tray 60. The water receiving tray 60 is connected to an end of the first plate 51A away from the head 40A. The remaining portion of the second housing 30 of the indoor unit 1 and the water receiving tray 60 define a heat exchange chamber 13. The water receiving tray 60 is used to collect water droplets condensed from the heat exchanger 92.

[0192] The housing of the air duct assembly of the embodiment of the present application also includes a third air guide portion 25. The portion of the head portion 40A facing away from the air flow channel is at least configured as a first return air surface 371. The first return air surface 371 extends from the pressure diffuser chamber 12 to the fan chamber 11. The third air guide portion 25 has a second return air surface 3821 spaced apart from the first return air surface 371. Specifically, the third air guide portion 25 includes a guide portion 252. The guide portion 252 is provided on a side of the first return air surface 371 facing away from the air flow channel, and the guide portion 252 has a second return air surface 3821. A return inlet 32 ​​and a return outlet 33 are formed between the first return air surface 371 and the second return air surface 3821. The return inlet 32 ​​faces the pressure diffuser chamber 12, and the return outlet 33 faces the fan chamber 11. The return channel 31 extends from the return inlet 32 ​​to the return outlet 33.

[0193] The head portion 40A and the first plate 51A define a diffuser bottom wall 501 of the diffuser chamber 12 for gas circulation, and a portion of the head portion 40A forms a volute tongue 40. The airflow from the fan 91 is diverted by the volute tongue 40 to flow to the diffuser chamber 12 and the area between the volute tongue 40 and the fan 91, respectively, and then flows back to the fan chamber 11. It is understandable that when the airflow from the fan 91 is diverted by the volute tongue 40 to flow to the diffuser chamber 12 and the fan chamber 11, respectively, the pressure (static pressure) of the airflow flowing into the diffuser chamber 12 after diversion increases, thereby making the airflow pressure at the return inlet 32 ​​greater than the airflow pressure at the return outlet 33. Furthermore, due to the pressure difference between the return inlet 32 ​​and the return outlet 33, part of the airflow entering the diffuser chamber 12 is actively guided back to the fan chamber 11 through the return channel 31 to work again. In this way, not only can the pressure of the fan chamber 11 between the volute tongue 40 and the fan 91 be compensated, thereby reducing the vortex effect and effectively improving the operating efficiency of the fan 91, but also the air intake efficiency and pressure resistance of the airflow returning to the fan chamber 11 can be increased, thereby improving the overall aerodynamic performance of the air duct assembly 10. At the same time, the reduction of vortexes can also simultaneously reduce the aerodynamic noise within the air duct assembly 10. In the embodiment of the present application, the third guide portion 25 is provided separately from the volute tongue 40. This facilitates mold opening when preparing the third guide portion 25, the volute tongue 40, and the first plate 51A, and the process difficulty is low.

[0194] Optionally, the first housing 20 includes at least a third air guide portion 25 and a first plate 51A, the first plate 51A integrally extending from the third air guide portion 25 toward the downstream airflow. For example, the third air guide portion 25 further includes a mounting portion 251, the mounting portion 251 being connected at an angle to the side of the guide portion 252 facing away from the second return air surface 3821. The first plate 51A integrally extends from the guide portion 252 or the mounting portion 251 toward the downstream airflow. The first plate 51A and the head portion 40A are configured as portions of the bottom wall of the diffuser chamber 12. The head portion 40A is independently provided from the first housing 20, i.e., the head portion 40A is detachably mounted to the first housing 20. The second return air surface 3821 of the third air guide portion 25 is spaced apart from the side of the first return air surface 371 facing away from the airflow channel. The return inlet 32, the return flow channel 31, and the return outlet 33 are surrounded by the first return air surface 371 and the second return air surface 3821. Furthermore, the first shell 20 may also include two guide end plates 502. In the direction perpendicular to the first return air surface 371 toward the second return air surface 3821 (that is, the horizontal direction of the return channel 31 described later), the two guide end plates 502 are respectively connected to the first plate body 51A and the guide portion 252 on opposite sides, and the head 40A is detachably installed on at least one of the first plate body 51A, the guide portion 252 and the guide end plate 502. At this time, the guide end plate 502 can extend to connect to the head 40A, and the return channel 31 is jointly defined by the walls of the first return air surface 371, the second return air surface 3821 and the two guide end plates 502.

[0195] Optionally, as shown in FIG35 , the first housing 20 includes at least a head 40A and a first plate 51A. The first plate 51A integrally extends from the head 40A toward the downstream direction of the airflow. The first plate 51A and the head 40A are configured as portions of the bottom wall of the pressure diffuser 12. The return inlet 32 ​​is formed by extending through the bottom wall of the pressure diffuser 12. For example, the return inlet 32 ​​extends through the first plate 51A, or the return inlet 32 ​​is defined by the first return air surface 371 of the head 40A and the surface of the first plate 51A facing the head 40A. The third air guide 25 is provided independently of the first housing 20, that is, the third air guide 25 is removably mounted to the first housing 20. For example, the third air guide 25 is removably mounted to the first plate 51A or the head 40A. Specifically, the third air guide portion 25 includes a mounting portion 251 and a guide portion 252. The mounting portion 251 is connected to the side of the guide portion 252 away from the second return air surface 3821 at an angle, and the mounting portion 251 is fixedly mounted on the first shell 20 at the edge of the return inlet 32. The mounting portion 251 is mounted on at least one of the head 40A and the first plate 51A, and the mounting portion 251 is spaced apart on the side of the first return air surface 371 away from the air flow channel. The return outlet 33 and the return channel 31 are surrounded by the first return air surface 371 via the guide portion 253. Furthermore, as shown in Figure 36, the first shell 20 may also include two guide end plates 502. In the direction perpendicular to the first return air surface 371 toward the second return air surface 3821 (that is, the horizontal direction of the return flow channel 31 described later), the two guide end plates 502 are respectively connected to the first plate body 51A and the head 40A on opposite sides, and the third guide part 25 is detachably installed on at least one of the first plate body 51A, the head 40A and the guide end plate 502. At this time, the return flow channel 31 is jointly defined by the walls of the first return air surface 371, the second return air surface 3821 and the two guide end plates 502.

[0196] It can be understood that the air flow pressure diverted into the return channel 31 is relatively high, and the third guide part 25 and the volute tongue 40 are separately arranged. When the air flow enters the return channel 31, due to the high air flow pressure, the air flow will act on the wall surface of the third guide part 25 and the volute tongue 40, which may easily cause the third guide part 25 and the volute tongue 40 to be unstable in installation, or even cause the third guide part 25 and the volute tongue 40 to be deformed. As shown in FIG37 , in an embodiment of the present application, the air duct assembly 10 further includes at least one second guide rib 26 . The second guide rib 26 is disposed within the return channel 31 and divides the return channel 31 into multiple sub-channels. This divides the airflow from the pressure diffuser 12 into multiple airflow paths leading out of the pressure diffuser 12, thereby dividing the pressure of the airflow entering the return channel 31. This results in a lower pressure for the airflow entering a single sub-channel, and a lower force exerted by the airflow within each sub-channel on the header 40A and the third guide portion 25. This effectively reduces deformation of the header 40A and the third guide portion 25 caused by airflow entering the return channel. Furthermore, the second guide rib 26 is located between the first return air surface 371 and the second return air surface 3821, providing support for the header 40A and the return air duct plate, further reducing deformation of the header 40A and the third guide portion 25.

[0197] The second guide ribs 26 are integrally formed with at least one of the first plate 51A, the third guide portion 25, and the head portion 40A. The second guide ribs 26 are disposed without gaps between the first return air surface 371 and the second return air surface 3821. "Without gaps" refers to at least one of an integral arrangement and a close fit. The provision of the ribs provides more stable support for the head portion 40A and the third guide portion 25, making them less susceptible to deformation.

[0198] When the second guide rib 26 is integrally formed with the first plate 51A, the head portion 40A and the third guide portion 25 can both be disposed in contact with the second guide rib 26. It is understood that because the head portion 40A and the third guide portion 25 are separate components, only one of the head portion 40A and the third guide portion 25 can be integrally formed with the second guide rib 26, while the other of the head portion 40A and the third guide portion 25 must be disposed in contact with the second guide rib 26.

[0199] Optionally, one of the first return air surface 371 and the second return air surface 3821 is provided with a second guide rib 26, and the second guide rib 26 contacts the other of the first return air surface 371 and the second return air surface 3821. For example, the second guide rib 26 is formed on the first return air surface 371 of the head portion 40A, and the portion of the second guide rib 26 away from the first return air surface 371 contacts the second return air surface 3821 of the third guide portion 25; or the second guide rib 26 is formed on the second return air surface 3821 of the third guide portion 25, and the portion of the second guide rib 26 away from the second return air surface 3821 contacts the first return air surface 371 of the head portion 40A. In this way, by integrally setting the second guide rib 26 with one of the head 40A and the third guide portion 25, the attachment area of ​​the second guide rib 26 is larger, the structural stability is stronger, the interaction force among the second guide rib 26, the head 40A and the third guide portion 25 is stronger, and deformation is less likely to occur.

[0200] When the second guide rib 26 is formed on the first return air surface 371 of the head 40A and is integrally arranged with the head 40A, the second guide rib 26 is in contact with the second return air surface 3821, and the second guide rib 26 extends to the return inlet 32 ​​of the return channel 31. The second guide rib 26 is integrally arranged with the first plate 51A at the return inlet 32 ​​of the return channel 31. Multiple second guide ribs 26 divide the return inlet 32 ​​of the return channel 31 into multiple sub-inlets. The head 40A can be connected to the first plate 51A through multiple second guide ribs 26 to realize the integrated arrangement of the head 40A, the first plate 51A and the second guide rib 26, which is convenient for assembly.

[0201] The second guide rib 26 extends along the longitudinal direction of the return channel 31 and from the return inlet 32 ​​of the return channel 31 to the side where the return outlet 33 is located. The longitudinal direction of the return channel 31 is the direction of airflow within the return channel 31, specifically the direction of airflow from the return inlet 32 ​​toward the return outlet 33. The direction indicated by the arrow S in Figure 35 is the direction of airflow within the return channel 31. This ensures smooth airflow into each sub-duct and minimizes flow resistance to airflow entering the return channel 31. Furthermore, the second guide rib 26 extends through the return channel 31 in the longitudinal direction of the return channel 31, stabilizing the state of airflow exiting the return channel 31 and reducing wind resistance to airflow entering the fan chamber 11.

[0202] Multiple second guide ribs 26 are arranged side by side and at intervals along the transverse direction of the return channel 31. The transverse direction of the return channel 31 is perpendicular to the direction of airflow in the return channel 31 and perpendicular to the direction from the first return air surface 371 to the second return air surface 3821. As shown in Figure 37, the direction indicated by the arrow T is the transverse direction of the return channel 31.

[0203] In the transverse direction of the return channel 31, the spacing between two adjacent second guide ribs 26 is equal, or the spacing between two adjacent second guide ribs 26 may be unequal. It is understood that in the transverse direction of the return channel 31, the airflow pressure in different areas of the return channel 31 may vary. In areas with high airflow pressure, the airflow exerts a stronger force on the head 40A and the third guide portion 25, making the head 40A and the third guide portion 25 more susceptible to deformation. Based on this, more second guide ribs 26 can be provided in areas with high airflow pressure, dividing these areas into multiple sub-channels with smaller flow areas. Specifically, in the transverse direction of the return channel 31, the return channel 31 includes multiple return air zones arranged side by side, with adjacent return air zones having different airflow pressures. The spacing between two adjacent second guide ribs 26 in the return air zone with higher airflow pressure is a1, while the spacing between two adjacent second guide ribs 26 in the return air zone with lower airflow pressure is a2, where a2 > a1. For example, in the transverse direction of the return channel 31, when the airflow pressure in the middle area is larger and the airflow pressure in the edge area is smaller, the distance between two adjacent second guide ribs 26 gradually decreases in the direction from the edge area to the middle area, that is, the multiple second guide ribs 26 are distributed more densely in the middle and more loosely at the edges.

[0204] The second guide ribs 26 are disposed without gaps with the first return air surface 371 and the second return air surface 3821, respectively. The width of the second guide ribs 26 in the direction from the first return air surface 371 to the second return air surface 3821 is the width of the corresponding area of ​​the return air duct. In the transverse direction of the return air duct, the widths of the second guide ribs 26 in the direction from the first return air surface 371 to the second return air surface 3821 are equal or different. Optionally, in the return air area with higher airflow pressure, the width of the second guide ribs 26 in the direction from the first return air surface 371 to the second return air surface 3821 is smaller, and in the return air area with lower airflow pressure, the width of the second guide ribs 26 in the direction from the first return air surface 371 to the second return air surface 3821 is larger.

[0205] The second guide rib 26 has two first surfaces 2601 arranged opposite to each other in the transverse direction of the return channel 31. The two first surfaces 2601 are respectively arranged to be perpendicular or at an obtuse angle to one of the first return air surface 371 and the second return air surface 3821. In this way, the second guide rib 26 has a larger connection area with the corresponding head 40A or the third guide part 25, thereby improving the installation stability of the second guide rib 26.

[0206] As the return inlet 32 ​​of the return channel 31 moves toward the return outlet 33, the vertical spacing between the two first surfaces 2601 in the transverse direction of the return channel 31 gradually decreases or remains unchanged. Considering that the pressure of the airflow at the return inlet 32 ​​is greater and the pressure of the airflow at the return outlet 33 is less, preferably, the vertical spacing between the two first surfaces 2601 in the transverse direction of the return channel 31 gradually decreases as the return inlet 32 ​​of the return channel 31 moves toward the return outlet 33, thereby gradually increasing the flow area of ​​the sub-air duct.

[0207] Optionally, the two first surfaces 2601 of the second guide rib 26 may extend to intersect at a guide line. For example, when the two first surfaces 2601 of the second guide rib 26 are both connected to the first return air surface 371, the two first surfaces 2601 intersect at a guide line in a direction away from the first return air surface 371, and the guide line is in contact with the second return air surface 3821; or, when the two first surfaces 2601 of the second guide rib 26 are both connected to the second return air surface 3821, the two first surfaces 2601 intersect at a guide line in a direction away from the second return air surface 3821, and the guide line is in contact with the second return air surface 3821.

[0208] Optionally, the second guide rib 26 includes a second surface 2602 connected between the two first surfaces 2601. The second surface 2602 is in contact with the other of the first return air surface 371 and the second return air surface 3821, thereby improving the support stability of the second guide rib 26 on the head 40A and the third guide portion 25. For example, when both first surfaces 2601 of the second guide rib 26 are in contact with the first return air surface 371, the second surface 2602 is in contact with the second return air surface 3821; when both first surfaces 2601 of the second guide rib 26 are in contact with the second return air surface 3821, the second surface 2602 is in contact with the first return air surface 371.

[0209] In the embodiment of the present application, the shape and size of the second guide rib 26 can be designed to adjust the distance between the first return air surface 371 and the second return air surface 3821. That is, in the direction from the first return air surface 371 to the second return air surface 3821, the width of the second guide rib 26 is equal to the width of the return flow channel 31. The above is only an exemplary introduction to the structure of the guide rib 2. In the embodiment of the present application, the shape and size of the second guide rib 26 are not limited, and can be selected according to actual needs to change the shape of each sub-duct.

[0210] The return inlet 32 ​​of the return channel 31 is set toward the diffuser chamber 12, and the return outlet 33 of the return channel 31 is set toward the fan chamber 11. The return channel 31 is set in an arc shape so as to smoothly guide part of the airflow in the diffuser chamber 12 to the fan chamber 11, thereby reducing the wind resistance of the airflow in the return channel 31 entering the fan chamber 11.

[0211] It is understood that the head 40A is used to divert the airflow from the fan 91 to flow toward the diffuser chamber 12 and the side of the head 40A near the fan chamber 11. Furthermore, a return channel 31 is provided at the first return air surface 371 of the head 40A. Consequently, three airflow spaces exist near the head 40A, and the airflow directions of the three airflow spaces are angled relative to each other. Accordingly, the cross-sectional profile of the head 40A in the transverse direction of the return channel 31 is approximately triangular, with the first vertex of the triangular cross-section of the head 40A being located near the junction between the first transition zone 111 of the fan chamber 11 and the diffuser chamber 12, the second vertex being located near the junction between the diffuser chamber 12 and the return inlet 32 ​​of the return channel 31, and the third vertex being located near the junction between the return outlet 33 of the return channel 31 and the fan chamber 11. Based on this, a first cavity 403 may optionally be provided within the head 40A to reduce the material usage and mass of the head 40A, thereby reducing the weight of the entire indoor unit 1.

[0212] As shown in Figure 35, optionally, the head 40A includes a first component 41A and a second component 45 that are independent of each other, the first component 41A forms a volute tongue 40, the second component 45 forms a first return air surface 371, the first component 41A is detachably mounted on the second component 45, and the first component 41A and the second component 45 define a first cavity 403 of the head 40A, wherein the first cavity 403 inside the head 40A is a closed cavity, preventing the airflow outside the head 40A and the gas in the first cavity 403 of the head 40A from intermingling, causing airflow turbulence in the space outside the head 40A.

[0213] The first component 41A and the second component 45 are snap-fitted to achieve a detachable connection between the first component 41A and the second component 45. Optionally, one side of the portion of the second component 45 adjacent to the return inlet 32 ​​is snap-fitted to the first component 41A, and the other side is connected to the first plate 51A. For example, when the return inlet 32 ​​of the return channel 31 is provided on the surface of the first plate 51A, the second component 45 is directly connected to the first plate 51A. When the return inlet 32 ​​of the return channel 31 is provided between the first plate 51A and the first return air surface 371, that is, the return inlet 32 ​​is jointly defined by the first plate 51A and the second component 45, the second component 45 can be connected to the first plate 51A via a plurality of second guide ribs 26.

[0214] A first matching portion 42A extends from both ends of the first component 41A toward the side away from the air flow channel, and a second matching portion 43 extends from both ends of the second component 45 toward the side of the air flow channel. The first matching portion 42A of each section corresponds to the outer side of each second matching portion 43, and the first matching portion 42A at one end faces the pressure diffuser 12, forming a part of the pressure diffuser bottom wall 501 of the pressure diffuser 12. Furthermore, the first matching portion 42A and the corresponding second matching portion 43 and the first plate body 51A jointly form the pressure diffuser bottom wall 501 of the pressure diffuser 12, and the first matching portion 42A at the other end faces the return flow channel 31, forming a part of the first return air surface 371.

[0215] Optionally, as shown in FIG37 , a portion of the second component 45 adjacent to the return outlet 33 is provided with a plurality of mating grooves 402, and the plurality of first mating portions 42A are snap-fitted into the mating grooves 402 in a one-to-one correspondence. This facilitates quick alignment of the second component 45 with the first component 41A, improving the installation stability of the second component 45 and the first component 41A adjacent to the return outlet 33. In this case, the first mating portions 42A and the second component 45, facing the surface of the third air guide 25, form a first return air surface 371. In which, a single second guide rib 26 can be formed entirely on the surface of the second component 45 facing the third guide portion 25; or, a portion of the single second guide rib 26 is formed on the first matching portion 42A, and the other portion is formed on the second component 45. Specifically, at least one first protrusion 261 is formed on the surface of the first matching portion 42A facing the third guide portion 25, and a plurality of second protrusions 262 are formed on the surface of the second component 45 facing the third guide portion 25, and each first protrusion 261 is connected to one of the second protrusions 262 to form a second guide rib 26.

[0216] Furthermore, each second guide rib 26 is formed by docking the first convex portion 261 with the second convex portion 262; or, a portion of the second guide ribs 26 are only formed on the surface of the second component 45, and the other portion of the second guide ribs 26 are formed by docking the first convex portion 261 with the second convex portion 262.

[0217] As shown in Figure 37, the air duct assembly 10 further includes a plurality of second clamping blocks 263, each of which is protruding from one of the second guide ribs 26 and integrally formed with the second guide rib 26. In conjunction with Figures 36 and 38, the second return air surface 3821 defines a plurality of latching openings 2051, each of which is inserted into one of the latching openings 2051. During assembly, the second clamping blocks 263 are inserted into corresponding latching openings 2051, and the second guide ribs 26 are positioned without gaps with the first return air surface 371 and the second return air surface 3821, respectively. This allows for rapid alignment of the third air guide portion 25 with the head portion 40A, facilitates assembly, effectively improves the alignment stability of the third air guide portion 25 with the head portion 40A, and effectively prevents deformation of the third air guide portion 25 and the second component 45 when wind pressure is excessive.

[0218] Optionally, each second block 263 is integrally formed on one of the second protrusions 262, and the second block 263 extends to fit the surface of the first protrusion 261 that is docked with the second protrusion 262. This further facilitates the rapid alignment of the first component 41A and the second component 45, and improves the connection stability between the first component 41A and the second component 45.

[0219] In the embodiment of the present application, the width of the return channel 31 in its transverse direction is greater than the flow rate of the airflow in the longitudinal direction of the return channel 31. Based on this, the part of the third guide part 25 adjacent to the return inlet 32 ​​and the part of the third guide part 25 adjacent to the return outlet 33 need to be fixed to improve the installation stability of the third guide part 25 and prevent the third guide part 25 from deformation.

[0220] Please refer to Figure 36 again. The third air guide portion 25 includes an integrally arranged third connecting portion 251, a guide portion 253 and a fixed portion 252; the third connecting portion 251 is stacked on the first plate body 51A and can be detachably installed on the first plate body 51A; the guide portion 253 is connected to the third connecting portion 251 at an angle and has a second return air surface 3821; the fixed portion 252 is connected to the end of the guide plate away from the third connecting portion 251 at an angle, and the fixed portion 252 is used to guide the airflow in the return channel 31 to flow toward the fan cavity 11, and the fixed portion 252 is used to connect to the grille 98 of the return air area 111 covered in the fan cavity 11. In this way, the third connecting portion 251 and the fixing portion 252 increase the contact area between the third air guide portion 25 and other structures, effectively improving the installation stability of the third air guide portion 25. Moreover, the third connecting portion 251 and the fixing portion 252 each extend away from the guide portion 253. The third connecting portion 251, the guide portion 253, and the fixing portion 252 can interact with each other, further reducing the probability of deformation of the third air guide portion 25. The fixing portion 252 can also guide the airflow in the return channel 31 smoothly into the return air area 111 of the fan chamber 11, reducing wind resistance and noise.

[0221] The functional components mounted on the first plate 51A may include the electronic control box assembly 93, sensors, and other components. The third connecting portion 251 is spaced apart from the functional components to facilitate assembly and disassembly of the third air guide 25 and the functional components. The functional components are mounted on the first plate 51A, and the gas flowing within the diffuser chamber 12 also removes heat generated by the functional components, facilitating heat dissipation. Of course, the functional components, the third connecting portion 251, and the first plate 51A can also be stacked to conserve installation space.

[0222] Optionally, the third connecting portion 251 and the fixing portion 252 are connected to the guide portion 253 on the side of the guide portion 253 facing away from the second return air surface 3821, and only the guide portion 253 is involved in defining the return channel 31, which facilitates assembly and facilitates the airflow in the return channel 31 to flow smoothly to the return air area 111 of the fan cavity 11.

[0223] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of this application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. This is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0224] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An air duct assembly, wherein, Comprising: A first housing; And A second housing, wherein the first housing and the second housing cooperate to define a connected blower chamber and a diffuser chamber. A blower is disposed in the blower chamber, and a volute tongue is provided at the transition between the blower chamber and the diffuser chamber. The blower drives external air flow into the blower chamber, and the volute tongue guides at least part of the air flow from the blower chamber into the diffuser chamber; The second housing includes a return passage, a first surface constituting the bottom surface of the diffuser chamber, and a second surface constituting part of the chamber wall surface of the blower chamber. The first surface is provided with a return inlet, and the second surface is provided with a return outlet. The return passage extends from the return inlet to the return outlet.

2. The air duct assembly according to claim 1, wherein, The return passage is curved.

3. The air duct assembly according to claim 1 or 2, wherein, The width of the return passage remains unchanged or is gradually enlarged in the direction from the return inlet to the return outlet.

4. The air duct assembly according to any one of claims 1 to 3, wherein, The extension line of the orientation of the return passage at the return outlet passes through the blower, and the included angle with the outer peripheral tangent of the blower is θ, and the θ is less than or equal to 15 degrees and greater than or equal to 0 degrees; Alternatively, the extension line of the orientation of the return passage at the return outlet passes through the outside of the blower, and the included angle with the outer peripheral tangent of the blower is β, and the β is less than or equal to 45 degrees and greater than or equal to 0 degrees.

5. The air duct assembly according to claim 4, wherein The θ is equal to 0 degrees or the β is equal to 0 degrees, so that the extension line of the orientation of the return passage at the return outlet coincides with the outer peripheral tangent of the blower.

6. The air duct assembly according to any one of claims 1 to 5, wherein, The second housing further includes an interface surface connected between the first surface and the second surface. The interface surface is recessed to form an air flow groove. One end of the air flow groove penetrates through the first surface to communicate with the return inlet, and the other end of the air flow groove penetrates through the second surface to communicate with the return outlet. The volute tongue covers the interface surface, so that the air flow groove forms the return passage.

7. The air duct assembly according to any one of claims 1 to 5, wherein, The second housing includes: A diffuser chamber lower housing, the diffuser chamber lower housing is provided with the first surface, and the diffuser chamber lower housing is connected to the volute tongue; A support member, the support member is connected to the side of the diffuser chamber lower housing facing away from the first surface and is connected to the volute tongue. The side of the support member facing away from the volute tongue is configured as a first air return surface; and A guide member, the guide member is connected to the side of the diffuser chamber lower housing facing away from the first surface and is spaced from the support member. The side of the guide member facing the support member is configured as a second air return surface. The second air return surface and the first air return surface cooperate to form the return passage, and the guide member and the support member cooperate to form the return outlet.

8. The air duct assembly according to claim 7, wherein, At least one first guide rib is provided on one of the first air return surface and the second air return surface, and the other of the first air return surface and the second air return surface abuts against the at least one first guide rib.

9. The air duct assembly according to claim 8, wherein, The first guide rib protrudes from the first air return surface and is integrally formed with the first air return surface, and the second air return surface abuts against the first guide rib; and / or, The first guide rib protrudes from the second air return surface and is integrally formed with the second air return surface, and the first air return surface abuts against the first guide rib.

10. The air duct assembly according to claim 8, wherein, One of the first return air surface and the second return air surface is provided with a plurality of the first guide ribs, and the plurality of the first guide ribs are arranged side by side and at intervals along the transverse direction of the return air channel, and the plurality of the first guide ribs divide the return inlet into a plurality of sub-inlets, and the transverse direction of the return air channel is perpendicular to the direction of airflow in the return air channel and perpendicular to the direction from the first return air surface toward the second return air surface.

11. The air duct assembly according to claim 10, wherein, The air duct assembly also includes a plurality of first clamping blocks, each of which is protruding from a first guide rib located on the first return air surface and is integrally formed with the first guide rib; the second return air surface is provided with a plurality of clamping openings, each of which is plugged into one of the clamping openings.

12. The air duct assembly according to claim 8, wherein, The first flow-guiding rib extends along the longitudinal direction of the return channel and from the return inlet to the side where the return outlet is located, and the longitudinal direction of the return channel is the direction of airflow flow in the return channel; One of the first return air surface and the second return air surface is provided with a plurality of the first guide ribs, and the plurality of the first guide ribs are arranged side by side and at intervals along the transverse direction of the return air channel, and the transverse direction of the return air channel is perpendicular to the direction of airflow flowing in the return air channel and perpendicular to the direction from the first return air surface to the second return air surface.

13. The air duct assembly according to claim 12, wherein, In the transverse direction of the return channel, the intervals between two adjacent first flow guiding ribs are equal.

14. The air duct assembly according to claim 12, wherein, In the transverse direction of the return channel, the return channel includes a plurality of return air zones arranged side by side, and the air flow pressures of two adjacent return air zones are different. The distance between two adjacent first guide ribs in the return air zone with larger air flow pressure is a1, and the distance between two adjacent first guide ribs in the return air zone with smaller air flow pressure is a2, and a2>a1.

15. The air duct assembly according to claim 12, wherein, At least one of the first guide ribs provided on one of the first return air surface and the second return air surface has two third surfaces arranged opposite to each other, and the two third surfaces are vertically or obtusely convex toward the part of the first return air surface and the second return air surface on the same side.

16. The air duct assembly according to claim 15, wherein, The first guide rib has a fourth surface connected between the two third surfaces, and the fourth surface abuts against the other of the first return air surface and the second return air surface.

17. The air duct assembly according to claim 15, wherein, In the direction from the reflux inlet of the reflux channel toward the reflux outlet, the vertical distance between the two third surfaces gradually decreases or remains unchanged.

18. The air duct assembly according to claim 7, wherein, The lower shell of the pressure diffuser cavity and the support member are an integral structure.

19. The air duct assembly according to claim 7, wherein, The lower shell of the pressure diffuser cavity and the flow guide member are an integral structure.

20. The air duct assembly according to claim 7, wherein, The guide member includes a first connecting portion, a first guide portion and a cavity wall portion. The first connecting portion is stacked on a side of the lower shell of the diffuser chamber facing away from the first surface and can be detachably installed on the lower shell of the diffuser chamber. The first guide portion is connected to the first connecting portion at an angle, and the first guide portion cooperates with the support member to form the reflux channel and the reflux outlet. The cavity wall portion is connected to an end of the first guide portion facing away from the first connecting portion at an angle, and extends in a direction away from the lower shell of the diffuser chamber.

21. The air duct assembly according to claim 20, wherein, The first connecting portion has a first connecting hole, and the diffuser chamber lower housing has a second connecting hole corresponding to the first connecting hole. The air duct assembly further includes: A fastener that sequentially passes through the second connecting hole and the first connecting hole to fix the first connecting portion to the diffuser chamber lower housing.

22. The air duct assembly according to claim 20, wherein, The air duct assembly further includes a grille that is detachably connected to the chamber wall portion and covers the air inlet side of the blower chamber.

23. The air duct assembly according to claim 22, wherein, One of a fixing buckle and a fixing slot is provided at one end of the chamber wall portion facing away from the first guiding portion, and the other of the fixing buckle and the fixing slot is provided on the grille. The fixing buckle and the fixing slot are in snap-fit connection.

24. The air duct assembly according to claim 1, wherein, The first housing and the second housing cooperate to define an air suction port communicating with the blower chamber. The second housing includes a housing main body and a diversion plate. The housing main body includes the return channel, the return inlet, and the return outlet; The diversion plate is connected to the housing main body and is located on one side of the air suction port. An uneven portion is provided at an end of the diversion plate away from the return outlet.

25. The air duct assembly according to claim 24, wherein, The uneven portion includes a tooth-shaped structure and / or a wavy structure.

26. The air duct assembly according to claim 24 or 25, wherein, When the uneven portion includes a tooth-shaped structure, the tooth-shaped structure includes a plurality of saw teeth arranged in sequence along the axial direction of the blower chamber, and the tooth roots of the plurality of saw teeth are connected.

27. The air duct assembly according to claim 26, wherein, When the uneven portion includes a tooth-shaped structure, the tooth-shaped structure includes a plurality of saw teeth arranged in sequence along the axial direction of the blower chamber, and the tooth roots of the plurality of saw teeth are spaced apart.

28. The air duct assembly according to claim 27, wherein, In the axial direction of the blower chamber, the spacing distance between adjacent saw teeth in the middle is smaller than the spacing distance between adjacent saw teeth on both sides.

29. The air duct assembly according to claim 26 or 27, wherein, The end face of the saw tooth away from the return outlet is flat; and / or, the shapes of the plurality of saw teeth are the same, and in the direction away from the return outlet of the diversion plate, the width dimension of the saw teeth gradually decreases.

30. The air duct assembly according to any one of claims 24 to 29, wherein, The diversion plate is inclined, and the distance between the diversion plate and the air suction port gradually increases in the direction away from the return outlet; and / or, the second housing further includes a grille that is detachably connected to the diversion plate and covers the air suction port.

31. The air duct assembly according to any one of claims 24 to 29, wherein, The housing main body includes a volute tongue and a diffuser chamber lower housing that are connected to each other, and the volute tongue and the diffuser chamber lower housing define the bottom surface of the diffuser chamber. The side of the volute tongue facing away from the blower chamber and the diffuser chamber lower housing cooperate to form the return channel and the return outlet, and the diversion plate is connected to the diffuser chamber lower housing; The return inlet of the return channel is opened on the bottom surface of the diffuser chamber and is located between the volute tongue and the diffuser chamber lower housing or on the diffuser chamber lower housing.

32. The air duct assembly according to claim 31, wherein, The diffuser chamber lower housing includes a housing body and a diversion plate. The housing body is connected to the volute tongue and cooperates to define the bottom surface of the diffuser chamber; The diversion plate is detachably connected to the housing body and is located on the side of the housing body facing away from the diffuser chamber. The side of the volute tongue facing away from the blower chamber and the diversion plate cooperate to form the return channel and the return outlet, and the diversion plate is connected to an end of the diversion plate facing away from the housing body.

33. The air duct assembly according to claim 32, wherein, The diversion plate and the diversion plate are of an integral structure.

34. The air duct assembly according to claim 1, wherein, The cavity bottom surface of the diffuser cavity includes a first part and a second part arranged side by side in the width direction of the air duct assembly, and the flow velocity of the air flow passing through the second part is lower than that of the air flow passing through the first part; Wherein, the return inlet of the return channel is opened on the first part, and the return outlet of the return channel communicates with the fan cavity.

35. The air duct assembly according to claim 34, wherein, The fan is a cross-flow fan, and the second part includes two parts respectively located on opposite sides of the first part in the width direction of the air duct assembly; Wherein, the distance from the return inlet to the outer edge of the second part is greater than 35 millimeters.

36. The air duct assembly according to claim 34 or 35, wherein The number of the return inlets is at least two, and at least two of the return inlets are arranged at intervals in the air flow direction.

37. The air duct assembly according to claim 36, wherein, The length of the return inlet located downstream in the air flow direction is shorter than the length of the return inlet located upstream in the air flow direction.

38. The air duct assembly according to claim 37, wherein, At the end of the return inlet located downstream in the air flow direction, it exceeds the end of the return inlet located upstream in the width direction of the air duct assembly.

39. The air duct assembly according to claim 37, wherein, The width of the return inlet located downstream in the air flow direction is greater than or equal to the width of the return inlet located upstream in the air flow direction.

40. The air duct assembly according to claim 34 or 35, wherein At least two of the return inlets are arranged at intervals in the width direction of the air duct assembly.

41. The air duct assembly according to claim 34 or 35, wherein, The return inlet is tapered from the outside to the inside.

42. The air duct assembly according to claim 41, wherein, The connection between the orifice wall of the return inlet and the first part is smoothly transitioned.

43. The air duct assembly according to claim 34 or 35, wherein, The return outlet includes a plurality of return sub-outlets, and the plurality of return sub-outlets are arranged at intervals in the width direction of the second housing; Alternatively, the return outlet extends along the width direction of the second housing.

44. The air duct assembly according to claim 34 or 35, wherein, The return outlet is tapered from the inside to the outside.

45. The air duct assembly according to claim 44, wherein, The connection between the orifice wall of the return outlet and the wall surface of the second housing is smoothly transitioned.

46. The air duct assembly according to claim 34 or 35, wherein The extension line of the orientation of the return outlet of the return channel passes through the fan, and the included angle with the outer peripheral tangent of the fan is θ, and the θ is less than or equal to 15 degrees and greater than or equal to 0 degrees; Alternatively, the extension line of the orientation of the return outlet of the return channel passes through from the outside of the fan, and the included angle with the outer peripheral tangent of the fan is β, and the β is less than or equal to 45 degrees and greater than or equal to 0 degrees.

47. The air duct assembly according to claim 46, wherein, The θ is equal to 0 degrees or the β is equal to 0 degrees, so that the extension line of the orientation of the return outlet of the return channel coincides with the outer peripheral tangent of the fan.

48. The air duct assembly according to claim 34 or 35, wherein, The return channel is curved.

49. The air duct assembly according to any one of claims 34 to 48, wherein, The second housing includes a volute tongue and a diffuser cavity bottom shell connected to each other, and the volute tongue and the diffuser cavity bottom shell define the cavity bottom surface of the diffuser cavity; Wherein, the outer wall surface of the volute tongue includes a guiding surface and a diffusing surface, the guiding surface is configured to guide the air flow in the fan cavity to flow into the diffuser cavity, the guiding surface extends from the side of the volute tongue facing the fan to the diffuser cavity, the diffusing surface is connected between the guiding surface and the top surface of the diffuser cavity bottom shell, and the diffusing surface and the top surface of the diffuser cavity bottom shell constitute the cavity bottom surface of the diffuser cavity; Wherein, the return inlet is opened on the top surface of the diffuser cavity bottom shell.

50. The air duct assembly according to claim 49, wherein, The return inlet is located at a position on the top surface of the diffuser cavity bottom shell closer to the diffusing surface than the guiding surface.

51. The air duct assembly according to any one of claims 34 to 48, wherein, The second shell includes a volute tongue and a diffuser cavity bottom shell connected to each other, and the volute tongue and the diffuser cavity bottom shell define the cavity bottom surface of the diffuser cavity; The outer wall surface of the volute tongue includes a guide surface and a pressure diffuser surface, the guide surface is configured to guide the airflow in the fan cavity to flow into the pressure diffuser cavity, the guide surface extends from the volute tongue toward the fan side to the pressure diffuser cavity, the pressure diffuser surface is connected between the guide surface and the top surface of the pressure diffuser cavity bottom shell, and the pressure diffuser surface and the top surface of the pressure diffuser cavity bottom shell constitute the cavity bottom surface of the pressure diffuser cavity; The return inlet is formed by the connection between the diffusion surface and the top surface of the diffusion chamber bottom shell.

52. The air duct assembly according to any one of claims 34 to 48, wherein, The second shell includes a volute tongue and a diffuser cavity bottom shell connected to each other, and the volute tongue and the diffuser cavity bottom shell define the cavity bottom surface of the diffuser cavity; The outer wall surface of the volute tongue includes a guide surface and a pressure diffuser surface, the guide surface is configured to guide the airflow in the fan cavity to flow into the pressure diffuser cavity, the guide surface extends from the volute tongue toward the fan side to the pressure diffuser cavity, the pressure diffuser surface is connected between the guide surface and the top surface of the pressure diffuser cavity bottom shell, and the pressure diffuser surface and the top surface of the pressure diffuser cavity bottom shell constitute the cavity bottom surface of the pressure diffuser cavity; The diffusion surface is provided with the reflux inlet.

53. The air duct assembly according to claim 1, wherein, The first shell and the second shell at least include: a head and a third guide portion; The portion of the head facing the airflow channel is at least configured as the volute tongue, and the portion of the head facing away from the airflow channel is at least configured as a first return air surface, and the first return air surface extends from the diffuser cavity to the fan cavity; The third air guide portion has a second return air surface spaced apart to correspond to the first return air surface, a return inlet and a return outlet are formed between the first return air surface and the second return air surface, the return inlet faces the diffuser cavity, the return outlet faces the fan cavity, and the return channel extends from the return inlet to the return outlet.

54. The air duct assembly according to claim 53, wherein, The first shell at least includes the third air guide portion and a first plate body, the first plate body is integrally extended from the third air guide portion toward the downstream of the air flow, and the first plate body is at least configured as a part of the bottom wall of the pressure diffuser cavity; The head is independently arranged from the first shell, the second return air surface of the third air guide portion is spaced apart from the first return air surface on the side away from the air flow channel, and the return inlet, the return flow channel and the return outlet are surrounded by the first return air surface and the second return air surface.

55. The air duct assembly according to claim 53, wherein, The first shell at least includes the head and a first plate, the first plate is integrally extended from the head toward the downstream of the airflow, and the first plate is at least configured as a part of the bottom wall of the diffuser cavity, and the reflux inlet is formed through the bottom wall of the diffuser cavity; The third air guide portion is independently arranged from the first shell, and the third air guide portion includes a mounting portion and a guide portion. The mounting portion is fixedly mounted on the first shell at the edge of the return inlet, and is spaced apart on the side of the first return air surface away from the air flow channel. The return outlet and the return channel are surrounded by the first return air surface via the guide portion.

56. The air duct assembly according to claim 53, wherein, One of the first return air surface and the second return air surface is provided with at least one second guide rib, and the other of the first return air surface and the second return air surface is in contact with at least one second guide rib.

57. The air duct assembly according to claim 56, wherein: The second guide convex rib is convexly disposed on the first return air surface and is integrally formed with the first return air surface, and the second return air surface abuts against the second guide convex rib; and / or, The second flow-guiding convex rib is integrally formed with the second return air surface at the return air inlet, and the first return air surface abuts against the second flow-guiding convex rib.

58. The air duct assembly according to claim 57, wherein, One of the first return air surface and the second return air surface is provided with a plurality of the second guide ribs, and the plurality of the second guide ribs are arranged side by side and at intervals along the transverse direction of the return air channel, and the plurality of the second guide ribs divide the return inlet of the return air channel into a plurality of sub-inlets, and the transverse direction of the return air channel is perpendicular to the direction of airflow flowing in the return air channel and perpendicular to the direction of the first return air surface toward the second return air surface.

59. The air duct assembly according to claim 56, wherein, The second flow-guiding rib extends along the longitudinal direction of the return channel and from the return inlet of the return channel to the side where the return outlet is located, and the longitudinal direction of the return channel is the direction of airflow flow in the return channel; One of the first return air surface and the second return air surface is provided with a plurality of the second guide ribs, and the plurality of the second guide ribs are arranged side by side and at intervals along the transverse direction of the return air channel, and the transverse direction of the return air channel is perpendicular to the direction of airflow flowing in the return air channel and perpendicular to the direction from the first return air surface toward the second return air surface.

60. The air duct assembly according to claim 59, wherein: In the transverse direction of the return channel, the distances between two adjacent second flow guiding ribs are equal; or, In the transverse direction of the return channel, the return channel includes a plurality of return air zones arranged side by side, the air flow pressures of two adjacent return air zones are different, the spacing between two adjacent second guide ribs in the return air zone with larger air flow pressure is a1, and the spacing between two adjacent second guide ribs in the return air zone with smaller air flow pressure is a2, and a2>a1.

61. The air duct assembly according to claim 56, wherein, At least one of the second air guide ribs provided on one of the first return air surface and the second return air surface has two first surfaces arranged opposite to each other, and the two first surfaces are respectively arranged to be perpendicular or at an obtuse angle to one of the first return air surface and the second return air surface.

62. The air duct assembly according to claim 61, wherein, The second air guide rib has a second surface connected between the two first surfaces, and the second surface abuts against the other of the first return air surface and the second return air surface.

63. The air duct assembly according to claim 53, wherein, In the direction from the reflux inlet of the reflux channel toward the reflux outlet, the vertical distance between the two first surfaces gradually decreases or remains unchanged.

64. The air duct assembly according to claim 53, wherein, The head includes a first component and a second component which are independent of each other. The first component forms the volute tongue, the second component forms the first air return surface, and the first component is detachably mounted on the second component.

65. The air duct assembly according to claim 64, wherein, A first matching portion extends from both ends of the first component toward a side away from the airflow channel, and a second matching portion extends from both ends of the second component toward one side of the airflow channel. The first matching portion of each section is correspondingly overlapped with the outer side of each second matching portion, wherein the first matching portion at one end faces the pressure diffuser cavity to form a part of the bottom wall of the pressure diffuser cavity, and the first matching portion at the other end faces the return flow channel to form a part of the first return air surface.

66. The air duct assembly according to claim 65, wherein, At least one first protrusion is formed on the surface of the first matching portion facing the third guide portion, and a plurality of second protrusions are formed on the surface of the second component facing the third guide portion, and each of the first protrusions is connected with one of the second protrusions to form a second guide rib.

67. The air duct assembly according to claim 66, wherein, The air duct assembly also includes a plurality of second clamping blocks, each of which is protruding from one of the second flow guide ribs and is integrally formed with the second flow guide rib; the second return air surface is provided with a plurality of clamping openings, each of which is plugged into one of the clamping openings.

68. The air duct assembly according to claim 66, wherein, The air duct assembly further includes a plurality of second clamping blocks, each of which is integrally formed with one of the second protrusions, and the second clamping blocks extend to fit the surface of the first protrusion that is docked with the second protrusion.

69. An indoor unit, wherein, Comprising the air duct assembly as described in any one of claims 1 to 68.

70. The indoor unit according to claim 69, wherein, The indoor unit is a duct unit, and the fan is a cross-flow fan.

71. A heating, ventilation and air conditioning system, wherein, It comprises an outdoor unit and an indoor unit as described in claim 69 or 70, and the indoor unit forms a refrigerant cycle with the outdoor unit.

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