Air filter for vehicle air compressor

Abstract

The invention belongs to the technical field of air compressors, and discloses an air filter for a vehicle air compressor, which comprises a filter assembly and a shell for accommodating the filter assembly, the filter assembly comprises a filter element shell as well as a molecular sieve filler, a silencing piece and a fastening piece which are arranged in the filter element shell; the filter element shell is provided with a gas inlet and a gas outlet; the molecular sieve filler comprises spherical molecular sieves with various particle sizes, the spherical molecular sieves with various particle sizes are separated by silencing pieces, and the particle sizes of the spherical molecular sieves are gradually increased along the direction from the gas inlet to the gas outlet; the fastener is arranged between the gas inlet and the molecular sieve filler and comprises a spring and a porous partition plate, the spring is used for being matched with the porous partition plate to form a fastening device, and the fastening device is used for pressing and fixing the molecular sieve filler in the filter element shell. According to the technical scheme, the service life of the molecular sieve in the filter can be prolonged, and noise generated in the working process can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of air compressors, and particularly relates to an air filter for a vehicle air compressor. Background Art

[0002] The automotive suspension system is an important component to ensure safe and comfortable vehicle driving; among them, compared with mechanical suspensions, air suspensions can actively adjust the vehicle chassis height, avoiding situations such as damage to the chassis due to too low a body and high resistance caused by too high a body at high speeds; in addition, considering that traditional suspension systems generally use metal parts as the main components, the air suspension system can significantly reduce the vehicle body weight and promote the improvement of the cruising range.

[0003] The air compressor is the core of the air supply unit, and high-pressure compressed air is generated by a single-stage reciprocating piston compressor; during the operation of the compressor, it is necessary to inhale air from the atmosphere, and the temperature of the compressed air rises, resulting in the precipitation of water vapor; in addition, during vehicle operation, the inhaled air quality is relatively poor, which can cause damage to the compressor or a reduction in performance over a long time. In view of the above situation, it is necessary to install a filter on the air compressor to achieve the purposes of purifying air, preventing water vapor condensation (exemplarily, fillers such as molecular sieves in the filter can adsorb water vapor to prevent it from condensing inside the compressor, thus avoiding problems such as rust and corrosion inside the compressor), and protecting the compressor from the influence of poor air quality.

[0004] At present, for the existing air filters for vehicle air compressors, after a long cumulative working time, the molecular sieves in the filter will be crushed, which will further cause the exhaust pipe to be blocked, resulting in compressor failures and performance reduction; in addition, the existing filters for vehicle air compressors will generate a certain amount of noise during the operation of the compressor. Summary of the Invention

[0005] The purpose of the present invention is to provide an air filter for a vehicle air compressor to solve one or more of the above existing technical problems. The air filter for a vehicle air compressor provided by the present invention extends the service life of the molecular sieves in the filter and reduces the noise generated during operation, thereby being able to extend the service life of the air compressor and improve the operating comfort during use.

[0006] To achieve the above object, the present invention adopts the following technical solutions: The present invention provides an air filter for a vehicle air compressor, comprising: a filtering component and a housing for accommodating the filtering component; The filtering component includes a filter element housing, and a molecular sieve filler, a silencing member, and a fastener disposed within the filter element housing; wherein, the filter element housing is provided with a gas inlet and a gas outlet; the molecular sieve filler includes spherical molecular sieves of multiple particle sizes, and the spherical molecular sieves of various particle sizes are separated by the silencing member, and along the direction from the gas inlet to the gas outlet, the particle size of the spherical molecular sieves gradually increases; the fastener is disposed between the gas inlet and the molecular sieve filler, and the fastener includes a spring and a porous partition, and the spring is used to cooperate with the porous partition to form a fastening device, and the fastening device is used to press and fix the molecular sieve filler within the filter element housing.

[0007] A further improvement of the technical solution of the present invention lies in that The silencing member is filled with porous sponge or filter paper.

[0008] A further improvement of the technical solution of the present invention lies in that The characteristic length ratio of the porous sponge and the spherical molecular sieve satisfies: ; In the formula, l is the length of the porous sponge, L is the length of the spherical molecular sieve.

[0009] A further improvement of the technical solution of the present invention lies in that A one-way valve and a seal are provided at the gas outlet of the filter element housing.

[0010] A further improvement of the technical solution of the present invention lies in that The molecular sieve filler includes a first spherical molecular sieve with a smaller particle size and a second spherical molecular sieve with a larger particle size, and the first spherical molecular sieve and the second spherical molecular sieve are arranged in sequence along the direction from the gas inlet to the gas outlet.

[0011] A further improvement of the technical solution of the present invention lies in that The proportion relationship between the first spherical molecular sieve and the second spherical molecular sieve satisfies: ; In the formula, a is the proportion of the second spherical molecular sieve; b is the proportion of the first spherical molecular sieve.

[0012] A further improvement of the technical solution of the present invention lies in that The porous partition is a circular porous plate; The relationship between the diameter D, the pore diameter d, and the number of pores n of the circular porous plate satisfies: ; 。

[0013] A further improvement of the technical solution of the present invention lies in that the filter element housing is further provided with a return air inlet and a return air outlet; wherein, the return air inlet is close to the gas outlet and is located at the bottom of the filter element housing; the return air outlet is close to the gas inlet and is located at the top of the filter element housing; the return air inlet is used to introduce external dry gas.

[0014] A further improvement of the technical solution of the present invention lies in that it further includes: a one-way slow-release valve and a regeneration solenoid valve; wherein, the one-way slow-release valve is arranged at the return air inlet, and the regeneration solenoid valve is used to control the connection and disconnection of the one-way slow-release valve.

[0015] A further improvement of the technical solution of the present invention lies in that a bend for serving as a gas flow path is arranged between the return air inlet and the molecular sieve filler.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an air filter for a vehicle air compressor. Through the cooperation among the arranged spring, porous partition plate and sound-absorbing member, the compression of the molecular sieve filler is realized, solving the problem that relative movement occurs between molecular sieves and molecular sieves are crushed due to the influence of air flow impact and high temperature during long-term use of the current molecular sieves. Through the cooperation of the porous partition plate and the sound-absorbing member, when high-pressure air enters the filter, it first passes through the porous partition plate and then enters the sound-absorbing member, solving the problem that high-pressure air flow directly impacts the molecular sieve in the current filter and easily causes the molecular sieve to be crushed, and using the throttling effect of the porous partition plate and the sound-absorbing member, the air flow noise is significantly reduced; in addition, by filling two or more specifications of molecular sieves in the filter, using smaller-diameter spherical molecular sieves at the front and larger-diameter spherical molecular sieves at the rear, the problems that when filling molecular sieves with the same diameter, the smaller-diameter molecular sieves bring greater flow resistance and the larger-diameter molecular sieves cannot completely absorb droplets are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art; obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1It is a schematic diagram of the overall structure of an air filter for a vehicle air compressor in an embodiment of the present invention; Figure 2 It is a schematic diagram of the structure of the filter assembly in an embodiment of the present invention; Figure 3 It is a schematic diagram of the porous partition in an embodiment of the present invention; The explanations of the reference numerals in the figure are as follows: 1. Housing; 2. Filter element housing; 3. Sound-absorbing member; 4. Fastener; 5. Porous partition; 6. Molecular sieve filler; 7. Check valve; 8. Spring; 9. First spherical molecular sieve; 10. Second spherical molecular sieve. Specific embodiments

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; obviously, the described embodiments of the technical solutions are part of the embodiments of the present invention, rather than all the embodiments.

[0020] Based on the technical solutions disclosed in the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. In addition, the terms "include" and "have" and any of their variations are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0021] Please refer to Figure 1 , an air filter for a vehicle air compressor provided by an embodiment of the present invention includes: A filter assembly and a housing 1 for accommodating the filter assembly; The filter assembly includes a filter element housing 2 and a molecular sieve filler 6, a sound-absorbing member 3, and a fastener 4 disposed in the filter element housing 2; wherein, a gas inlet and a gas outlet are provided on the filter element housing 2; the molecular sieve filler 6 includes spherical molecular sieves of various particle sizes, and the spherical molecular sieves of various particle sizes are separated by the sound-absorbing member 3, and along the direction from the gas inlet to the gas outlet, the particle size of the spherical molecular sieve gradually increases; the fastener 4 includes a spring 8 and a porous partition 5, and the spring 8 is used to cooperate with the porous partition 5 to form a fastening device, and the fastening device is used to press and fix the molecular sieve filler 6 in the filter element housing 2.

[0022] In a further exemplary alternative technical solution, the spring 8 is fixedly arranged on the side of the porous partition 5 away from the molecular sieve filler 6, and the porous partition 5 is located between the gas inlet and the molecular sieve filler 6.

[0023] In the technical solution provided by the embodiment of the present invention, a spring, a porous partition and a sound-absorbing member are arranged in cooperation. The spring and the porous partition form a fastening device, and the sound-absorbing member serves as a separating device for the molecular sieve, realizing the pressing of the filter element sieve filler in the filter element housing, reducing the pulverization phenomenon of the molecular sieve during long-term use, and thus being able to extend the service life of the filter; the porous partition and the sound-absorbing member form a sound-absorbing device, effectively reducing the noise generated during the working process and improving the comfort during the operation process. Specifically, in the existing filter molecular sieve during long-term use, due to the continuous impact of the high-speed air flow, relative movement occurs between the molecular sieves, and the mutual friction between the molecular sieves causes their shape to change from a uniform spherical shape to a non-uniform shape, resulting in an increasing impact of the air flow, and at the same time causing an increase in the flow resistance, and finally pulverization occurs. The technical solution of the present invention can reduce the relative movement of the molecular sieve filler (i.e., molecular sieve particles) caused by the air flow impact by using a fastener. In addition, by using molecular sieves with different particle sizes, the specific surface area of a part of the molecular sieves can be reduced, resulting in less fragmentation caused by high-pressure impact, and finally realizing the effects of extending the service life of the molecular sieve and reducing the flow resistance. In addition, the sound-absorbing member and the porous partition together constitute a sound-absorbing device, effectively reducing the noise generated during the working process and improving the comfort.

[0024] In a preferred embodiment of the present invention, the sound-absorbing member 3 may include a mounting frame and porous sponge or filter paper filled therein.

[0025] In the technical solution of the embodiment of the present invention, the porous sponge or filter paper serves as a separating device for the molecular sieve, and at the same time cooperates with the porous partition to form a sound-absorbing device, which can reduce the noise when the high-pressure air flow passes through.

[0026] Specifically, to ensure the sound-absorbing effect and reduce the flow resistance loss in the sound-absorbing sponge, the relationship between the porous sponge and the spherical molecular sieve is obtained according to the following theoretical calculation and experimental verification: ; In the formula, is the flow resistance coefficient of the porous sponge; is the flow resistance coefficient of the molecular sieve; is the pressure difference before and after flowing through the filter, ; is the specific volume, ; In the filter, the ratio of the characteristic lengths of the porous sponge and the molecular sieve should satisfy: ; Wherein, l is the length of the sound-absorbing sponge, L is the length of the molecular sieve.

[0027] In a specific embodiment of the present invention, a check valve 7 and a seal are provided at the gas outlet of the filter element housing 2.

[0028] In the embodiment of the present invention, by providing a check valve and a seal, backflow can be prevented, the filtration efficiency can be improved, and dust can be prevented from entering.

[0029] Please refer to Figure 2 , in a preferred embodiment of the present invention, the molecular sieve filler 6 includes a first spherical molecular sieve 9 and a second spherical molecular sieve 10. The first spherical molecular sieve 9 with a smaller particle size is used at the front, and the second spherical molecular sieve 10 with a larger particle size is used at the back.

[0030] In the technical solution provided by the embodiment of the present invention, the technical means of hierarchical filtration increases the filtration area and improves the filtration efficiency; in addition, the technical means of hierarchical cooperation reduces the resistance, can increase the intake air volume, improve the air flow throughability, and can also reduce blockage and extend the service life.

[0031] Explanatorily, regarding the air passing through the molecular sieve as passing through a throttling device, there is: ; In the formula, is the specific internal energy before flowing through the filter, ; is the pressure before flowing through the filter, ; is the specific volume before flowing through the filter, ; is the specific internal energy after flowing through the filter, ; is the pressure after flowing through the filter, ; is the specific volume after flowing through the filter, ; When designing, in order to reduce the flow resistance loss in the molecular sieve, large-diameter molecular sieves should be used as much as possible, thereby increasing the gap size between the molecular sieve particles. According to experiments and theoretical calculations, when using two types of molecular sieves, the proportion of large-diameter molecular sieves (the second spherical molecular sieve 10) is a, and the proportion of small-diameter molecular sieves (the first spherical molecular sieve 9) is b. The two should satisfy: .

[0032] In a preferred embodiment of the present invention, the air filter for a vehicle air compressor further includes: A regeneration solenoid valve is used to realize the regeneration of the spherical molecular sieves in the molecular sieve filler 6. The filter element housing 2 is further provided with a return air inlet and a return air outlet; the return air inlet is close to the gas outlet and is located at the bottom of the filter element housing 2; the return air outlet is close to the gas inlet and is located at the top of the filter element housing 2; a one-way slow-release valve is arranged at the return air inlet for introducing external dry gas.

[0033] In the technical solution of the embodiment of the present invention, the regeneration solenoid valve realizes the regeneration of the molecular sieves in the filter by controlling its opening. Specifically, the regeneration solenoid valve is opened through an external power supply, so that the high-pressure dry air flow passes through the one-way slow-release valve and flows through the molecular sieves from the back pressure side, absorbs the moisture in the molecular sieves, and completes the regeneration process.

[0034] Please refer to Figure 3 , in a preferred embodiment of the present invention, the porous partition plate 5 is a circular porous plate, and its aperture and the number of holes are designed to avoid the direct impact of the high-pressure air flow on the molecular sieves and reduce the gas flow resistance.

[0035] Explanatorily, the anti-impact structure includes a porous partition plate 5 and a sound-absorbing member 3; when designing the circular porous plate, if the aperture is too small, it will cause an increase in the gas flow resistance, and if the aperture is too large, it will cause the high-pressure air flow to directly impact the molecular sieves, resulting in the fragmentation of the molecular sieves; if the number of holes is too small, the throttling effect will be obvious when the gas flows through, and the flow resistance will increase, and if the number of holes is too large, it will increase the impact on the molecular sieves; therefore, it is necessary to comprehensively consider the aperture size and the number of holes when designing the porous partition plate. After comprehensive consideration of calculation and experiment, when designing the orifice plate, for the diameter D of the metal plate and the aperture d, it should satisfy: ; For the number of holes n should satisfy: .

[0036] In a specific embodiment of the present invention, an air filter for a vehicle air compressor is provided. The fastener 4 arranged at the front part (the part close to the gas inlet) of the air filter includes a spring 8 and a porous partition plate 5. The spring 8 is fixed at the connection between the porous partition plate 5 and the cylinder and is fixed with bolts. The connection is sealed by an O-ring. Through the spring 8, the molecular sieve filler 6 in the filter can obtain a certain pre-tightening force, so that during use, even after the molecular sieves absorb a certain amount of water, they will not generate relative movement under the impact of the air flow, avoiding the wear between the molecular sieves, thereby playing a role in extending the service life; in addition, through the porous partition plate 5, the direct impact of the high-pressure air flow on the molecular sieve filler 6 is avoided, and the impact loss caused by the high-pressure air flow is reduced, which can also play a role in extending the service life of the molecular sieve filler 6.

[0037] In a further preferred technical solution, a porous sponge is arranged behind the porous partition. The purpose is to play a sound-absorbing role through the porous sponge, reducing the noise of the high-pressure air flow. At the same time, the porous sponge can also adsorb a certain amount of particulate dust, avoiding the direct impact on the molecular sieve and causing the molecular sieve to be crushed, and further extending the service life of the molecular sieve.

[0038] The molecular sieves with different particle sizes are filled in two layers behind the porous sponge. From front to back, they are 4A molecular sieve spheres with a diameter of 1.6 mm to 2.5 mm and 4A molecular sieve spheres with a diameter of 3 mm to 5 mm respectively. The two layers of molecular sieves are separated by a porous sponge. By arranging two layers of molecular sieves, it is possible to absorb the water in the high-pressure air and reduce the flow resistance. And using small-diameter molecular sieves in the front part, the force on a single molecular sieve particle under the direct impact of the high-pressure air flow is small, and it is less likely to break, thus extending the service life. The porous sponge between the two layers of molecular sieves ensures that even if the molecular sieve breaks, the powder of the previous layer of molecular sieve will not enter the next layer, which can not only extend the service life of the next layer of molecular sieve but also avoid the loss of the filtering effect after the molecular sieve is crushed.

[0039] In a further preferred technical solution, a gas flow path is arranged in the center of the filter, and a one-way slow-release valve is arranged at the bottom of the filter. The filter front part and the back pressure side are connected through the gas flow path. When the compressor is working, the one-way slow-release valve is in the closed state, and the high-pressure gas can only enter the back pressure side through the molecular sieve of the filter. When the compressor stops working and the molecular sieve in the filter needs to be regenerated, the one-way slow-release valve opens at this time, and the high-pressure gas on the back pressure side flows through the molecular sieve in the filter through the gas flow path and is discharged, so that the water in the molecular sieve is absorbed by the dry gas, realizing the regeneration of the molecular sieve. In an exemplary technical solution, the regeneration solenoid valve is fixed to the filter housing by bolts, sealed by an O-ring, and the one-way electromagnetic slow-release valve is controlled through an external power supply. By using a reasonable solenoid valve and adding a gas flow path bend between the solenoid valve and the filter molecular sieve, the direct impact of the high-pressure air flow is reduced, the loss of the molecular sieve in the filter is reduced, and thus the service life of the filter is extended.

[0040] In summary, the embodiments of the present invention elaborate in detail an air filter for a newly designed vehicle air compressor. Through structural design and material selection, this air filter effectively solves multiple technical problems existing in existing air filters, significantly improving the performance and service life of the filter. Specifically, the present invention realizes the tight compaction of the molecular sieve filler through the synergistic effect of combining a spring, a porous partition plate, and porous sponge. This design effectively addresses the impact of airflow shock and high-temperature environment on the stability of the molecular sieve during long-term use. In traditional filters, the molecular sieve is prone to relative movement due to the long-term dynamic impact of airflow and high-temperature action, which can lead to the crushing of molecular sieve particles, affecting the filtration effect and the service life of the filter. The design of the present invention ensures the stability of the molecular sieve filler through the continuous pressure provided by the spring, combined with the fixing and supporting effects of the porous partition plate and porous sponge, effectively preventing the crushing of the molecular sieve, thereby extending the service life of the filter and maintaining its high filtration performance. Further, the present invention makes an innovation in the combined use of the porous partition plate and porous sponge. When high-pressure air enters the filter, it first passes through the porous partition plate, which plays a role in initially dispersing and slowing down the airflow velocity. Subsequently, the air enters the porous sponge layer, and the fine structure of the sponge further refines the airflow, avoiding the direct impact of high-pressure airflow on the molecular sieve, thereby reducing the risk of molecular sieve crushing caused by direct impact. At the same time, the throttling effect of the porous partition plate and the sponge significantly reduces the noise generated when the airflow passes through the filter, improving the comfort of the overall working environment of the vehicle air compressor. In addition, the present invention also optimizes the filling strategy of the molecular sieve. In traditional filters, molecular sieves of the same diameter are usually filled, but this often results in a large flow resistance caused by small-diameter molecular sieves, while large-diameter molecular sieves cannot completely absorb droplets, affecting the filtration efficiency. To address this problem, the present invention proposes a solution of filling two or more specifications of molecular sieves. In the front part of the filter, small-diameter spherical molecular sieves are used. These molecular sieves have a large specific surface area and can effectively capture tiny particles and moisture in the air. In the rear part of the filter, large-diameter spherical molecular sieves are used. These molecular sieves have better permeability and adsorption capacity, can further absorb residual droplets and impurities, and at the same time reduce the flow resistance. This layered filling strategy not only ensures the filtration efficiency but also reduces the flow resistance, achieving a perfect combination of filtration performance and energy efficiency. Summarizing, the air filter for the vehicle air compressor provided by the embodiments of the present invention, through the ingenious cooperation of the spring, the porous partition plate, the porous sponge, and the novel design of the molecular sieve filling strategy, effectively solves problems such as molecular sieve crushing, large airflow noise, and the contradiction between flow resistance and filtration efficiency existing in existing filters, providing a more efficient, reliable, and quiet filtration solution for the vehicle air compressor.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific implementation manners of the present invention or make equivalent substitutions, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. An air filter for a vehicle air compressor, characterized in that, Comprising: A filtering component and a housing (1) for accommodating the filtering component; The filtering component includes a filter element housing (2), a molecular sieve filler (6), a silencing member (3), and a fastener (4) disposed within the filter element housing (2); wherein, the filter element housing (2) is provided with a gas inlet and a gas outlet; the molecular sieve filler (6) includes spherical molecular sieves of various particle sizes, and the spherical molecular sieves of various particle sizes are separated by the silencing member (3), and along the direction from the gas inlet to the gas outlet, the particle size of the spherical molecular sieves gradually increases; the fastener (4) is disposed between the gas inlet and the molecular sieve filler (6), and the fastener (4) includes a spring (8) and a porous partition (5), and the spring (8) is used to cooperate with the porous partition (5) to form a fastening device, and the fastening device is used to press and fix the molecular sieve filler (6) within the filter element housing (2).

2. The air filter for a vehicle air compressor according to claim 1, wherein The silencing member (3) is filled with porous sponge or filter paper.

3. The air filter for a vehicle air compressor according to claim 2, wherein The characteristic length ratio of the porous sponge and the spherical molecular sieve satisfies: ； In the formula, l is the length of the porous sponge, L is the length of the spherical molecular sieve.

4. The air filter for a vehicle air compressor according to claim 1, wherein A one-way valve (7) and a seal are provided at the gas outlet of the filter element housing (2).

5. The air filter for a vehicle air compressor according to claim 1, wherein The molecular sieve filler (6) includes a first spherical molecular sieve (9) with a smaller particle size and a second spherical molecular sieve (10) with a larger particle size, and the first spherical molecular sieve (9) and the second spherical molecular sieve (10) are arranged in sequence along the direction from the gas inlet to the gas outlet.

6. The air filter for a vehicle air compressor according to claim 5, wherein The proportion relationship between the first spherical molecular sieve (9) and the second spherical molecular sieve (10) satisfies: ； In the formula, a is the proportion of the second spherical molecular sieve; b is the proportion of the first spherical molecular sieve.

7. The air filter for a vehicle air compressor according to claim 1, wherein The porous partition (5) is a circular porous plate; The diameter D, the aperture d, and the number of holes of the circular perforated plate n satisfy the relationship: ； 。 8. The air filter for a vehicle air compressor according to claim 1, wherein The filter element housing (2) is further provided with a return air inlet and a return air outlet; Wherein, the return air inlet is close to the gas outlet and is at the bottom of the filter element housing (2); the return air outlet is close to the gas inlet and is at the top of the filter element housing (2); the return air inlet is used to introduce external dry gas.

9. The air filter for a vehicle air compressor according to claim 8, wherein Further comprising: a one-way slow-release valve and a regeneration solenoid valve; Wherein, the one-way slow-release valve is disposed at the return air inlet, and the regeneration solenoid valve is used to control the connection and disconnection of the one-way slow-release valve.

10. An air filter for a vehicle air compressor according to claim 8, characterized in that a bend for serving as a gas flow path is provided between the air return inlet and the molecular sieve filler (6).

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