Frequency converter cooling device of generator set

Abstract

The invention relates to a frequency converter cooling device of a generator set, the frequency converter cooling device of the generator set comprises a heat dissipation box internally provided with a frequency converter main body, one end of the heat dissipation box is provided with a heat dissipation hole, and one end, far away from the heat dissipation hole, of the heat dissipation box is fixedly connected with a fan cover; during use, the double-shaft motor is started to drive the exhaust fan and the air reversing structure formed by assembling the annular connecting plate, the air blowing plate and the fixing bolt to rotate, the exhaust fan rotates to suck cold air into the exhaust pipes and convey the cold air into the fan cover, and the air reversing structure is installed in the fan cover. The direction of airflow can be changed through rotation of the air blowing plate, the airflow is conveyed to different positions in the heat dissipation box through the multiple air blowing pipes, direct blowing of the frequency converter body in multiple directions is achieved, rapid heat dissipation of the frequency converter body is achieved, and the problems that an existing air cooling heat dissipation device generally can only directly blow the side, close to a fan, of the frequency converter, and the cooling efficiency is low are solved as much as possible.

Description

Technical Field

[0001] The invention belongs to the technical field of frequency converter heat dissipation, and in particular relates to a frequency converter cooling device for a generator set. Background Art

[0002] The variable frequency drive (VFD) is a power control device that uses frequency conversion technology and microelectronics technology. It controls the speed of the AC motor by changing the frequency of the generator set's working power supply. The variable frequency drive will generate a lot of heat during operation. If it is not cooled in time, the internal temperature of the variable frequency drive will rise, which will affect its performance and reliability.

[0003] The existing method generally installs a fan on one side of the inverter, and uses wind to convey flowing air to act on the inverter to dissipate heat from the inverter. However, the flowing air can only blow directly to the part of the inverter close to the fan, and cannot blow directly to other positions of the inverter, which leads to low heat dissipation and cooling efficiency of the inverter. Summary of the invention

[0004] The purpose of the present invention is to provide a frequency converter cooling device for a generator set with a simple structure and reasonable design in order to solve the above problems.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] A frequency converter cooling device for a generator set comprises a heat sink in which a frequency converter body is installed, one end of the heat sink is provided with a heat dissipation hole, an end of the heat sink away from the heat dissipation hole is fixedly connected to a hood, a plurality of air blowing pipes are distributed in a ring around the hood, one end of the air blowing pipes is communicated with an inner cavity of the hood, the other end of the air blowing pipes is communicated with the inner cavity of the heat sink, an air reversing structure is rotatably connected in the inner cavity of the hood, an exhaust pipe is installed at one end of the hood away from the heat sink, a mounting bracket is fixedly installed in the exhaust pipe, a dual-axis motor is connected to the mounting bracket, one output shaft of the dual-axis motor is fixedly connected to the air reversing structure, an exhaust fan is fixedly connected to the other output shaft of the dual-axis motor, and a dust filter structure is fixedly installed at one end of the exhaust pipe close to the exhaust fan;

[0007] A section of the outer surface of the exhaust pipe located on the peripheral side of the dual-axis motor is fixedly connected to a cooling hood, and the cooling hood is annular in structure. Water inlet pipe joints and drain pipe joints are symmetrically installed on both sides of the cooling hood. One end of the water inlet pipe joint and the drain pipe joint passes through the side wall of the cooling hood and is fixed to the side wall of the cooling hood. Fins evenly distributed around the dual-axis motor are fixedly installed on the inner wall of the exhaust pipe.

[0008] As a further optimization scheme of the present invention, a plurality of heat sinks with annular structures are fixedly installed on the periphery of the inverter body, the inner walls of the heat sinks are fixed to the outer surface of the inverter body, through holes are provided on the plurality of heat sinks, a mounting seat is installed on the side of the inverter body away from the heat dissipation holes, and the inverter body is fixed to the inner wall of the heat dissipation box through the mounting seat.

[0009] As a further optimization scheme of the present invention, flow valves are installed in the middle sections of the multiple air blowing pipes, a temperature sensor for detecting the temperature of the inverter body at that position is installed at the connection between the inner wall of the heat sink and the air blowing pipe, a control circuit board is installed on the outer wall of the heat sink, and the flow valve and the temperature sensor are electrically connected to the control circuit board.

[0010] As a further optimization scheme of the present invention, the air reversing structure includes two annular connecting plates arranged in the inner cavity of the wind hood, a plurality of inclined blowing plates are arranged between the two annular connecting plates, and fixing bolts are screwed at the connection between the two ends of the blowing plates and the annular connecting plates, and a reversing impeller structure is formed together by the annular connecting plates, the blowing plates and the fixing bolts.

[0011] As a further optimization scheme of the present invention, connecting shafts are fixedly connected to the center positions of both ends of the reversing impeller structure, one of the connecting shafts passes through the side wall of the wind hood end and is rotatably connected to the side wall of the wind hood end, and the other connecting shaft is fixed to the output shaft of the dual-axis motor near one end of the wind hood.

[0012] As a further optimization scheme of the present invention, the wind hood and the adjacent ends of the exhaust pipe are integrally formed with a plurality of ear plates, the ear plates arranged on the wind hood correspond one to one with the ear plates arranged on the exhaust pipe, through holes are opened on the ear plates, and bolt structures for threadedly fixing the wind hood and the exhaust pipe are passed through the through holes.

[0013] As a further optimization scheme of the present invention, both ends of the cooling cover are bent inward to form side baffles of annular structure, the inner wall of the side baffle is welded and fixed to the outer wall of the exhaust pipe, and a cooling cavity for storing cooling water is formed between the two side baffles.

[0014] As a further optimization scheme of the present invention, the dust filtering structure includes a mounting ring fixedly mounted on the end of the exhaust pipe away from the wind hood, a dust filter net is arranged inside the mounting ring, and the peripheral side of the dust filter net is fixedly connected to the inner wall of the mounting ring.

[0015] As a further optimization scheme of the present invention, a bearing is installed in the center of the dust filter, the outer ring of the bearing is fixed to the dust filter, a rotating shaft is fixedly passed through the inner ring of the bearing, a fixing hole is opened at one end of the exhaust fan close to the rotating shaft, the end of the rotating shaft located in the exhaust pipe is fixed to the exhaust fan through the fixing hole, and a cleaning brush is fixedly installed on the end of the rotating shaft located outside the exhaust pipe, and the bristles of the cleaning brush are in sliding contact with the outer surface of the dust filter.

[0016] The beneficial effects of the present invention are as follows: when in use, the dual-axis motor is started to drive the exhaust fan and the air reversing structure formed by the annular connecting plate, the blast plate and the fixing bolt to rotate. The exhaust fan rotates to suck the cold air into the exhaust pipe and transport it to the wind hood. The air reversing structure is installed in the wind hood and can change the direction of the airflow by rotating the blast plate. The airflow is transported to different positions in the heat dissipation box through multiple blowing pipes, thereby realizing direct blowing of the inverter body in multiple directions, quickly dissipating the heat of the inverter body, and avoiding as much as possible the problem that the existing air-cooled heat dissipation device can generally only directly blow the inverter close to the fan side and has low cooling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the connection structure of the inverter body, the heat sink and the mounting base of the present invention;

[0018] Figure 2 It is an exploded view of the overall structure of the present invention;

[0019] Figure 3 It is a schematic diagram of the installation structure of the wind cover, the heat dissipation box and the air blowing pipe of the present invention;

[0020] Figure 4 The present invention Figure 3 A schematic diagram of the cross-sectional structure of;

[0021] Figure 5 It is a schematic diagram of the assembly structure of the air reversing structure of the present invention;

[0022] Figure 6 It is a schematic diagram of the internal structure of one end of the air extraction pipe of the present invention;

[0023] Figure 7 It is a schematic diagram of the internal structure of the other end of the air extraction pipe of the present invention;

[0024] Figure 8 The present invention Figure 7 A schematic diagram of the cross-sectional structure of;

[0025] Fig. 9 It is a schematic diagram of the connection structure of the dust filter screen, the cleaning brush and the mounting ring of the present invention.

[0026] In the figure: 1. Inverter body; 2. Heat sink; 3. Through hole; 4. Mounting seat; 5. Heat sink; 6. Heat dissipation hole; 7. Wind hood; 8. Air blow pipe; 9. Flow valve; 10. Temperature sensor; 11. Ring connecting plate; 12. Blower plate; 13. Fixing bolt; 14. Connecting shaft; 15. Exhaust pipe; 16. Mounting bracket; 17. Dust filter; 18. Exhaust fan; 19. Fixing hole; 20. Mounting ring; 21. Dust filter; 22. Bearing; 23. Cleaning brush; 24. Ear plate; 25. Through hole; 26. Bolt structure; 27. Cooling hood; 28. Fin; 29. ​​Water inlet pipe joint; 30. Drain pipe joint; 31. Control circuit board. DETAILED DESCRIPTION

[0027] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0028] Example 1

[0029] like Figure 1 - Figure 8 As shown, a frequency converter cooling device for a generator set comprises a heat sink 5 in which a frequency converter body 1 is installed, a plurality of heat sinks 2 with annular structures are fixedly installed around the frequency converter body 1, the inner wall of the heat sink 2 is fixed to the outer surface of the frequency converter body 1, and through holes 3 are opened on the plurality of heat sinks 2, so that the heat exchange area of ​​the frequency converter 1 can be increased through the heat sink 2, thereby improving the cooling efficiency of the frequency converter body 1, and a mounting seat 4 is installed on the side of the frequency converter body 1 away from the heat dissipation hole 6, and the frequency converter body 1 is fixed to the inner wall of the heat sink 5 through the mounting seat 4;

[0030] A heat dissipation hole 6 is provided at one end of the heat dissipation box 5, and the air after cooling the inverter body 1 installed inside the heat dissipation box 5 can be discharged through the heat dissipation hole 6, taking away the heat generated by the inverter body 1 when working, thereby cooling the inverter body 1;

[0031] One end of the heat dissipation box 5 away from the heat dissipation hole 6 is fixedly connected with a wind cover 7, and a plurality of air blowing pipes 8 are distributed in a ring around the wind cover 7. One end of the air blowing pipes 8 is connected to the inner cavity of the wind cover 7, and the other end of the air blowing pipes 8 is connected to the inner cavity of the heat dissipation box 5. When external air enters the wind cover 7, it can be transported to the heat dissipation box 5 through the plurality of air blowing pipes 8, and act on various positions of the inverter main body 1, so as to perform all-round heat dissipation on the inverter main body 1 installed in the heat dissipation box 5;

[0032] An air reversing structure is rotatably connected in the inner cavity of the wind hood 7. The air reversing structure includes two annular connecting plates 11 arranged in the inner cavity of the wind hood 7. A plurality of obliquely arranged blasting plates 12 are arranged between the two annular connecting plates 11. Fixing bolts 13 are screwed at the connection between the two ends of the blasting plates 12 and the annular connecting plates 11. A reversing impeller structure is formed between the annular connecting plates 11, the blasting plates 12 and the fixing bolts 13. The reversing impeller structure is used to rotate in the inner cavity of the wind hood 7. The airflow direction is changed by rotating the obliquely arranged blasting plates 12, so that the air entering the inner cavity of the wind hood 7 is quickly transported to the heat dissipation box 5 through the blowing pipe 8.

[0033] An exhaust pipe 15 is provided at one end of the hood 7 away from the heat sink 5. A plurality of ear plates 24 are integrally formed at the adjacent ends of the hood 7 and the exhaust pipe 15. The ear plates 24 provided on the hood 7 correspond to the ear plates 24 provided on the exhaust pipe 15 one by one. A through hole 25 is provided on the ear plate 24. A bolt structure 26 for screwing and fixing the hood 7 and the exhaust pipe 15 is passed through the through hole 25, so as to connect the exhaust pipe 15 and the hood 7 to form an integral structure.

[0034] A mounting bracket 16 is fixedly installed in the exhaust pipe 15, and a double-shaft motor 17 is connected to the mounting bracket 16. Connecting shafts 14 are fixedly connected to the center positions of both ends of the reversing impeller structure. One of the connecting shafts 14 passes through the side wall of the end of the wind hood 7 and is rotatably connected to the side wall of the end of the wind hood 7. The other connecting shaft 14 is fixed to the output shaft of the double-shaft motor 17 near one end of the wind hood 7. An exhaust fan 18 is fixedly connected to the other output shaft of the double-shaft motor 17. The mounting bracket 16 is provided to fix the double-shaft motor 17. The two output shafts of the dual-axis motor 17 are respectively fixed to the air reversing structure and the exhaust fan 18. When the dual-axis motor 17 is started, it can drive the exhaust fan 18 and the air reversing structure to rotate at the same time. The rotation of the exhaust fan 18 can draw air from the external environment into the exhaust pipe 15 and transport it to the wind hood 7 along the exhaust pipe 15. When the air ring structure rotates, the air flow direction is changed by rotating the inclined blower plate 12, and the air entering the inner cavity of the wind hood 7 is quickly transported to the heat dissipation box 5 through the blowing pipe 8.

[0035] It should be noted that, when the inverter cooling device of the generator set is used, the inverter body 1 is first installed in the heat sink 5 through the mounting seat 4, and then the double-shaft motor 17 installed in the inner cavity of the exhaust pipe 15 is started, and the exhaust fan 18 and the air reversing structure formed by the annular connecting plate 11, the blast plate 12 and the fixing bolt 13 are driven by the double-shaft motor 17 to rotate. During the rotation process, the exhaust fan 18 can suck the cold air in the external environment into the exhaust pipe 15, and transport the cold air to the wind cover 7 along the exhaust pipe 15. The annular connecting plate 11, the blast plate 12 and the fixing bolt 13 are driven by the double-shaft motor 17. The air reversing structure formed by the assembly of the wind plate 12 and the fixing bolt 13 is installed in the wind cover 7. When the air reversing structure rotates, the air flow direction can be changed by rotating the blower plate 12, and the air flow is transported to the heat sink 5 through multiple air blowing pipes 8 installed between the heat sink 5 and the wind cover 7, and directly blows the inverter body 1 from multiple directions, thereby realizing rapid heat dissipation of the inverter body 1, and avoiding as much as possible the problem that the existing air-cooled heat dissipation device can generally only directly blow the part of the inverter close to the fan side, and cannot directly blow other positions of the inverter, resulting in low heat dissipation and cooling efficiency of the inverter.

[0036] Example 2

[0037] Further improvements are made on the basis of Example 1, such as Figure 2 and Figure 6-Figure 8 As shown: a section of the outer surface of the exhaust pipe 15 located on the side of the dual-axis motor 17 is fixedly connected to a cooling hood 27, the cooling hood 27 is annular in structure, and both ends of the cooling hood 27 are bent inward to form side baffles of annular structure, the inner wall of the side baffle is welded and fixed to the outer wall of the exhaust pipe 15, and a cooling chamber for storing cooling water is formed between the two side baffles, and water inlet pipe joints 29 and drainage pipe joints 30 are symmetrically installed on both sides of the cooling hood 27, one end of the water inlet pipe joint 29 and the drainage pipe joint 30 both penetrate the side wall of the cooling hood 27 and are fixed to the side wall of the cooling hood 27, and fins 28 equidistantly distributed around the dual-axis motor 17 are fixedly installed on the inner wall of the exhaust pipe 15.

[0038] Since the ambient air is affected by the ambient temperature, when the ambient temperature is high, the user can connect an external water inlet pipe to the water inlet pipe joint 29 and connect an external drain pipe to the drain pipe joint 30, transport cold water to the cooling chamber through the external water inlet pipe, and discharge excess cold water through the external drain pipe, so that the cooling water can circulate in the cooling chamber and maintain a low temperature. The low-temperature cooling water in the cooling chamber can exchange heat with the air sucked in through the exhaust pipe 15 through the fins 28, thereby reducing the temperature of the air and improving the heat dissipation efficiency of the inverter body 1.

[0039] Example 3

[0040] Further improvements are made on the basis of Example 2, such as Figure 3 and Figure 4As shown, flow valves 9 are installed in the middle sections of multiple blowing pipes 8, and temperature sensors 10 for detecting the temperature of the inverter body 1 at the connection between the inner wall of the heat sink 5 and the blowing pipe 8 are installed. A control circuit board 31 is installed on the outer wall of the heat sink 5, and the flow valves 9 and the temperature sensor 10 are electrically connected to the control circuit board 31.

[0041] A plurality of temperature sensors 10 are installed at the position where the air blowing pipe 8 is connected to the inner wall of the heat sink 5, and are used to detect the temperature of the inverter body 1 at this position and transmit the temperature information to the control circuit board 31. When the exhaust temperature of one of the air blowing pipes 8 is low and the exhaust temperature of other air blowing pipes 8 is high, the control circuit board 31 can adjust the air flow in each air blowing pipe 8 by controlling the flow valve 9, so that the plurality of air blowing pipes 8 blow air into the heat sink 5 at different air flow rates. The exhaust flow at the position with lower temperature is reduced, and the exhaust flow at the position with higher temperature is increased, thereby ensuring uniform heat dissipation of the inverter body 1.

[0042] Example 4

[0043] Further improvements are made to the technology in Example 3, such as Figure 2 and Fig. 9 As shown, a dust filter structure is fixedly installed at one end of the exhaust pipe 15 close to the exhaust fan 18, and the dust filter structure includes a mounting ring 20 fixedly installed on the end of the exhaust pipe 15 away from the wind hood 7, and a dust filter screen 21 is arranged inside the mounting ring 20. The circumference of the dust filter screen 21 is fixedly connected to the inner wall of the mounting ring 20, and a bearing 22 is installed in the center of the dust filter screen 21. The outer ring of the bearing 22 is fixed to the dust filter screen 21, and a rotating shaft is fixedly penetrated through the inner ring of the bearing 22. A fixing hole 19 is opened at one end of the exhaust fan 18 close to the rotating shaft, and the end of the rotating shaft located in the exhaust pipe 15 is fixed to the exhaust fan 18 through the fixing hole 19. A cleaning brush 23 is fixedly installed on the end of the rotating shaft located outside the exhaust pipe 15, and the bristles of the cleaning brush 23 are in sliding contact with the outer surface of the dust filter screen 21.

[0044] A dust filter 21 is provided to filter the air through the dust filter 21, so as to prevent dust and impurities in the environmental control from entering the heat sink 5 as much as possible and adhering to the inverter body 1, thereby affecting the heat dissipation efficiency of the inverter body 1. A rotating shaft is provided to connect the end of the exhaust fan 18 with the cleaning brush 23. When the dual-axis motor 17 drives the exhaust fan 18 to rotate and inhale air into the exhaust pipe 15, the cleaning brush 23 can be synchronously driven to rotate through the rotating shaft to filter and brush off the dust retained on the dust filter 21, so as to prevent the mesh of the dust filter 21 from being clogged due to dust adhesion, thereby affecting the problem of the exhaust fan 18 inhaling air into the exhaust pipe 15.

[0045] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A frequency converter cooling device for a generator set, comprising a heat sink (5) in which a frequency converter body (1) is installed, wherein one end of the heat sink (5) is provided with a heat dissipation hole (6), and characterized in that: The end of the heat dissipation box (5) away from the heat dissipation hole (6) is fixedly connected to a wind cover (7), and a plurality of air blowing pipes (8) are distributed in an annular manner around the wind cover (7). One end of the air blowing pipe (8) is communicated with the inner cavity of the wind cover (7), and the other end of the air blowing pipe (8) is communicated with the inner cavity of the heat dissipation box (5). An air reversing structure is rotatably connected in the inner cavity of the wind cover (7). An exhaust pipe (15) is installed at the end of the wind cover (7) away from the heat dissipation box (5). A mounting bracket (16) is fixedly installed in the exhaust pipe (15), and a double-axis motor (17) is connected to the mounting bracket (16). One output shaft of the double-axis motor (17) is fixedly connected to the air reversing structure, and an exhaust fan (18) is fixedly connected to the other output shaft of the double-axis motor (17). A dust filter structure is fixedly installed at one end of the exhaust pipe (15) close to the exhaust fan (18); A cooling hood (27) is fixedly connected to a section of the outer surface of the exhaust pipe (15) located on the peripheral side of the dual-axis motor (17); the cooling hood (27) is an annular structure; water inlet pipe joints (29) and drainage pipe joints (30) are symmetrically installed on both sides of the cooling hood (27); one end of each of the water inlet pipe joints (29) and the drainage pipe joints (30) passes through the side wall of the cooling hood (27) and is fixed to the side wall of the cooling hood (27); and fins (28) are fixedly installed on the inner wall of the exhaust pipe (15) and are evenly distributed around the dual-axis motor (17).

2. The inverter cooling device of a generator set according to claim 1, characterized in that: A plurality of heat sinks (2) of annular structure are fixedly mounted on the peripheral side of the inverter body (1); the inner wall of the heat sink (2) is fixed to the outer surface of the inverter body (1); through holes (3) are provided on the plurality of heat sinks (2); a mounting seat (4) is mounted on the side of the inverter body (1) away from the heat dissipation hole (6); and the inverter body (1) is fixed to the inner wall of the heat dissipation box (5) via the mounting seat (4).

3. The inverter cooling device of a generator set according to claim 1, characterized in that: A flow valve (9) is installed in the middle section of each of the plurality of air blowing pipes (8); a temperature sensor (10) for detecting the temperature of the inverter body (1) at the connection between the inner wall of the heat sink (5) and the air blowing pipe (8); a control circuit board (31) is installed on the outer wall of the heat sink (5); and the flow valve (9) and the temperature sensor (10) are both electrically connected to the control circuit board (31).

4. The inverter cooling device of a generator set according to claim 1, characterized in that: The air reversing structure comprises two annular connecting plates (11) arranged in the inner cavity of the wind cover (7), a plurality of obliquely arranged blast plates (12) are arranged between the two annular connecting plates (11), fixing bolts (13) are screwed at the connection points between the two ends of the blast plates (12) and the annular connecting plates (11), and a reversing impeller structure is formed between the annular connecting plates (11), the blast plates (12) and the fixing bolts (13).

5. The inverter cooling device of a generator set according to claim 4, characterized in that: Connecting shafts (14) are fixedly connected at the center positions of both ends of the reversing impeller structure, one of the connecting shafts (14) passes through the end side wall of the wind hood (7) and is rotatably connected to the end side wall of the wind hood (7), and the other connecting shaft (14) is fixed to the output shaft of the dual-shaft motor (17) close to one end of the wind hood (7).

6. The inverter cooling device of a generator set according to claim 1, characterized in that: A plurality of ear plates (24) are integrally formed at adjacent ends of the wind hood (7) and the exhaust pipe (15); the ear plates (24) arranged on the wind hood (7) correspond one to one with the ear plates (24) arranged on the exhaust pipe (15); a through hole (25) is provided on the ear plate (24); a bolt structure (26) for screwing and fixing the wind hood (7) and the exhaust pipe (15) is passed through the through hole (25).

7. The inverter cooling device of a generator set according to claim 1, characterized in that: The two ends of the cooling cover (27) are bent inward to form a side baffle plate with an annular structure. The inner wall of the side baffle plate is welded and fixed to the outer wall of the exhaust pipe (15). A cooling cavity for storing cooling water is formed between the two side baffle plates.

8. The inverter cooling device of a generator set according to claim 1, characterized in that: The dust filtering structure comprises a mounting ring (20) fixedly mounted on one end of the exhaust pipe (15) away from the wind cover (7), a dust filter net (21) being arranged inside the mounting ring (20), and the peripheral side of the dust filter net (21) being fixedly connected to the inner wall of the mounting ring (20).

9. The inverter cooling device of a generator set according to claim 8, characterized in that: A bearing (22) is installed at the center of the dust filter (21), the outer ring of the bearing (22) is fixed to the dust filter (21), and a rotating shaft is fixedly penetrated through the inner ring of the bearing (22). A fixing hole (19) is opened at one end of the exhaust fan (18) close to the rotating shaft, and the end of the rotating shaft located in the exhaust pipe (15) is fixed to the exhaust fan (18) through the fixing hole (19), and a cleaning brush (23) is fixedly installed on the end of the rotating shaft located outside the exhaust pipe (15), and the bristles of the cleaning brush (23) are in sliding contact with the outer surface of the dust filter (21).

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