Improved rotor of permanent magnet brushless direct current motor

Abstract

The invention provides an improved rotor of a permanent magnet brushless direct current motor, and relates to the field of motors. The improved rotor of the permanent magnet brushless direct current motor comprises a shell, a rear cover is arranged at the rear end of the shell, a grating is fixedly connected to the rear end of the inner wall of the rear cover, an electric hydraulic rod is fixedly connected to the center of the outer wall of the front end of the grating, and a rod body of the electric hydraulic rod is sleeved with a rotating disc. The outer wall of the rotating disc is fixedly connected with a plurality of fan blades, and the output end of the electric hydraulic rod is rotationally connected with a second clutch disc. The electric hydraulic rod drives the second clutch disc to stretch out, then the second clutch disc slowly makes contact with the first clutch disc, then the first clutch disc drives the second clutch disc to rotate, then the second clutch disc drives the rotating disc to rotate through the fixing column, and therefore the rotating disc drives the fan blades to rotate; when the direct current motor is started, external air is sucked and exhausted from the vent groove, so that the motor is cooled, and the load when the direct current motor is started can be reduced.

Description

Technical Field

[0001] The invention relates to the field of motors, and in particular to an improved rotor of a permanent magnet brushless DC motor. Background Art

[0002] A permanent magnet brushless DC motor is an electric motor that uses the interaction between the stable magnetic field generated by permanent magnets and current to achieve rotor rotation without relying on carbon brushes and commutators. The rotor is the rotating part of the motor and an important component of the permanent magnet brushless DC motor. The use and structural design of its permanent magnets play a key role in the performance and efficiency of the motor. Therefore, an improved rotor of a permanent magnet brushless DC motor is proposed.

[0003] When the permanent magnet brushless DC motor is started, the rotor shaft directly drives the fan to rotate to cool the motor. The overall temperature is relatively low at startup. When the internal temperature does not reach the normal temperature, the efficiency and output power of the motor may be affected. At the same time, when used in some areas with lower temperatures, the fan is directly driven to rotate at startup, so that the motor needs a longer time to reach the normal operating temperature. Driving the fan at startup will increase the starting load of the motor to a certain extent. In addition, when the existing permanent magnet brushless DC motor is assembled, the rotor cannot be effectively and quickly installed on the shaft. Therefore, an improved rotor of a permanent magnet brushless DC motor is proposed. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the deficiencies in the prior art, the present invention provides an improved rotor for a permanent magnet brushless DC motor, which solves the problem that a traditional motor drives a fan to rotate when started, thereby requiring a long time to reach an optimal operating temperature.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] An improved rotor of a permanent magnet brushless DC motor comprises a housing, a front cover is arranged at the front end of the housing, a rear cover is arranged at the rear end of the housing, a grille is fixedly connected to the rear end of the inner wall of the rear cover, an electric hydraulic rod is fixedly connected to the center of the front end outer wall of the grille, a rotating disk is sleeved on the rod body of the electric hydraulic rod, a plurality of blades are fixedly connected to the outer wall of the rotating disk, a second clutch plate is rotatably connected to the output end of the electric hydraulic rod, and a plurality of fixing columns are fixedly connected to the edge of the rear end outer wall of the second clutch plate;

[0009] The inner wall of the shell is fixedly connected with a plurality of stators, the outer walls of the stators are sleeved with stator windings, the rear end of the inner wall of the shell is fixedly connected with a sealing plate, a rotating shaft is arranged inside the shell, the rear end of the rotating shaft penetrates the sealing plate and is fixedly connected with a first clutch plate, the rear end of the rotating shaft is fixedly connected with a limiting plate, the middle part of the rotating shaft is fixedly connected with a plurality of clamping plates, a liquid injection groove is provided on the front end outer wall of the rotating shaft, a movable cavity is provided inside the rotating shaft, a plurality of movable plates are arranged inside the movable cavity, the outer wall of one side of the movable plate away from the inner center of the rotating shaft is fixedly connected with a fixed plate, a liquid flow pipe is provided at the rear end of the liquid injection groove, and a one-way valve is sleeved on the body of the liquid flow pipe;

[0010] A plurality of iron cores are arranged in the middle of the shaft body of the rotating shaft, a mounting groove is provided at the center of the outer wall of the front end of the iron core, a plurality of slots are provided on the inner wall of the mounting groove, a rotor winding is sleeved on the outer wall of the iron core, a junction box is fixedly connected to one side of the outer wall of the shell, and the outer wall of the iron core is provided with anti-rust paint;

[0011] Through the above technical solution, by spraying anti-rust paint on the outside of the iron core, and then using silicon steel sheets on the iron core, the overall anti-rust performance of the rotor can be effectively improved, thereby indirectly improving the overall performance of the DC motor, thereby avoiding the problem of rust on the iron core due to exposure of the iron core to humid air in the later stage.

[0012] Furthermore, bearings are provided at the centers of the sealing plate and the inner wall of the front cover, and the inner walls of the bearings are fixedly connected to the shaft body respectively;

[0013] Through the above technical solution, bearings are arranged at the center of the sealing plate and the inner wall of the front cover, and the inner walls of the bearings are fixedly connected to the shaft body respectively, so that the shaft can be supported and the shaft can be rotated better.

[0014] Furthermore, a plurality of heat sinks are fixedly connected to the outer wall of the shell;

[0015] Through the above technical solution, a plurality of heat sinks are fixedly connected through the outer wall of the shell, thereby better cooperating with the fan blades to improve the heat dissipation effect.

[0016] Furthermore, the lower end of the outer wall of the shell is fixedly connected to two support seats;

[0017] Through the above technical solution, two support seats are fixedly connected through the lower end of the outer wall of the shell, so that the motor can be placed better.

[0018] Furthermore, a plurality of air holes are provided on the rear end outer wall of the second clutch plate, the outer walls of the first clutch plate and the second clutch plate on the side close to each other are tightly fitted, and the rear end outer wall of the fixing column is fixedly connected to the edge of the front end outer wall of the rotating disk;

[0019] Through the above technical scheme, a plurality of air holes are opened through the rear end outer wall of the second clutch plate, and the outer walls on the side where the first clutch plate and the second clutch plate are close to each other are tightly fitted, so that when the first clutch plate and the second clutch plate are fitted, the air holes can better discharge the heat generated by friction, and then the rear end outer wall of the fixed column is fixedly connected to the edge of the front end outer wall of the rotating disk, so that the second clutch plate can better drive the rotating disk to rotate.

[0020] Furthermore, a placement groove is provided inside the rotating disk, and the rotating disk is rotationally connected to the electric hydraulic rod through the placement groove;

[0021] Through the above technical scheme, a placement groove is opened inside the rotating disk, and the rotating disk is rotatably connected to the electric hydraulic rod through the placement groove, so that the second clutch plate can better drive the rotating disk to rotate, thereby rotating the fan blades, thereby cooling the motor.

[0022] Furthermore, the inner wall of the mounting groove is tightly fitted with the outer wall of the rotating shaft, the clamping groove is clamped with the clamping plate, and the outer wall of one side of the limiting plate and the fixing plate close to the middle of the rotating shaft are tightly fitted with the front outer wall of the front core and the rear outer wall of the rear core;

[0023] Through the above technical scheme, the inner wall of the installation groove is tightly fitted with the outer wall of the rotating shaft, and the clamping groove is clamped with the clamping plate, so that the iron core can be fixed on the shaft body more firmly, and then the outer wall on one side close to the middle of the rotating shaft is tightly fitted with the front end outer wall of the front end iron core and the rear end outer wall of the rear end iron core through the limiting plate and the fixing plate, so that the iron core can be fixed more firmly through the limiting plate and the fixing plate.

[0024] Furthermore, the movable cavity is connected to the liquid injection groove through a liquid flow pipe, and a sealing gasket is provided on the outer wall of the movable plate;

[0025] Through the above technical solution, the movable cavity and the liquid injection groove are connected through the liquid flow pipe, and the outer wall of the movable plate is provided with a sealing gasket, so that multiple iron cores can be better fixed through the fixed plate, avoiding the problem of more troublesome installation in the past.

[0026] Furthermore, a plurality of ventilation grooves are provided at the edge of the front end outer wall of the rear cover, and the ventilation grooves are connected with the interior of the rear cover;

[0027] Through the above technical solution, a plurality of ventilation grooves are opened at the edge of the outer wall of the front end of the rear cover, and the ventilation grooves are connected with the interior of the rear cover, so that the motor can be better cooled.

[0028] (III) Beneficial effects

[0029] The present invention provides an improved rotor for a permanent magnet brushless DC motor. It has the following beneficial effects:

[0030] 1. The present invention provides an improved rotor of a permanent magnet brushless DC motor. After the motor is started for a period of time, when the temperature of the DC motor reaches the optimal working temperature and continues to rise, the second clutch plate is driven to extend through the electric hydraulic rod, and then the second clutch plate is slowly brought into contact with the first clutch plate, and then the first clutch plate drives the second clutch plate to rotate, and then the second clutch plate drives the rotating disk to rotate through the fixed column, so that the rotating disk drives the fan blades to rotate, so that the fan blades absorb external gas and discharge it from the ventilation groove, thereby cooling the DC motor. This avoids the problem that the fan is driven to rotate at startup, which may cause the DC motor to take a long time to reach the optimal working temperature, and can effectively reduce the load of the DC motor at startup.

[0031] 2. The present invention provides an improved rotor of a permanent magnet brushless DC motor, which is achieved by sleeved multiple iron cores on a rotating shaft through mounting grooves, aligning the clamping grooves with clamping plates, and then installing the iron cores on the rotating shaft. After installation, hydraulic oil is injected into the fluid pipe through the injection groove, and then the hydraulic oil enters the interior of the movable cavity through a one-way valve to push the movable plate to move, thereby causing the movable plate to drive the fixed plate to move, thereby fixing the multiple iron cores on the upper end of the rotating shaft, so that the iron cores can be quickly installed.

[0032] 3. The present invention provides an improved rotor of a permanent magnet brushless DC motor. By spraying anti-rust paint on the outside of the iron core and then using silicon steel sheets as the iron core, the overall anti-rust performance of the rotor can be effectively improved, thereby indirectly improving the overall performance of the DC motor, thereby avoiding the problem of rust on the iron core due to exposure of the iron core to humid air in the later stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is an axonometric view of the present invention;

[0034] Figure 2 It is a rear view of the present invention;

[0035] Figure 3 It is a rear cross-sectional view of the present invention;

[0036] Figure 4 It is a front cross-sectional view of the present invention;

[0037] Figure 5 An exploded view of the present invention;

[0038] Figure 6 It is a schematic diagram of the structure of the back cover and other components in the present invention;

[0039] Figure 7 It is a schematic diagram of the structure of the rotating shaft and other components in the present invention;

[0040] Figure 8 is a cross-sectional view of the rotating shaft in the present invention;

[0041] Fig. 9 It is a schematic diagram of the structure of the rotor in the present invention;

[0042] Fig.10 It is a side view of the heat dissipation fan and other structures in the present invention.

[0043] Among them, 1. shell; 2. back cover; 3. ventilation groove; 4. junction box; 5. support seat; 6. rotating shaft; 7. front cover; 8. heat sink; 9. fan blades; 10. grille; 11. sealing plate; 12. first clutch plate; 13. second clutch plate; 14. fixing column; 15. electric hydraulic rod; 16. air vent; 17. iron core; 18. bearing; 19. liquid injection groove; 20. stator winding; 21. stator; 22. rotating disk; 23. placement groove; 24. rotor winding; 25. fixing plate; 26. limit plate; 27. clamping plate; 28. movable plate; 29. ​​movable cavity; 30. sealing gasket; 31. liquid flow pipe; 32. one-way valve; 33. anti-rust paint; 34. installation groove; 35. clamping groove. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] like Figure 1-10 As shown, an embodiment of the present invention provides an improved rotor of a permanent magnet brushless DC motor, comprising a housing 1, a front cover 7 is provided at the front end of the housing 1, a rear cover 2 is provided at the rear end of the housing 1, a grille 10 is fixedly connected to the rear end of the inner wall of the rear cover 2, an electric hydraulic rod 15 is fixedly connected to the center of the front end outer wall of the grille 10, a rotating disk 22 is sleeved on the rod body of the electric hydraulic rod 15, a plurality of blades 9 are fixedly connected to the outer wall of the rotating disk 22, a second clutch plate 13 is rotatably connected to the output end of the electric hydraulic rod 15, and a plurality of fixing columns 14 are fixedly connected to the edge of the rear end outer wall of the second clutch plate 13;

[0046] A plurality of stators 21 are fixedly connected to the inner wall of the housing 1, and the outer walls of the stators 21 are sleeved with stator windings 20. A sealing plate 11 is fixedly connected to the rear end of the inner wall of the housing 1. A rotating shaft 6 is arranged inside the housing 1. The rear end of the rotating shaft 6 penetrates the sealing plate 11 and is fixedly connected to the first clutch plate 12. A limiting plate 26 is fixedly connected to the rear end of the shaft body of the rotating shaft 6. A plurality of clamping plates 27 are fixedly connected to the middle part of the shaft body of the rotating shaft 6. A liquid injection groove 19 is provided on the outer wall of the front end of the rotating shaft 6. A movable cavity 29 is provided inside the rotating shaft 6. A plurality of movable plates 28 are arranged inside the movable cavity 29. A fixed plate 25 is fixedly connected to the outer wall of the movable plate 28 on one side away from the inner center of the rotating shaft 6. A liquid flow pipe 31 is provided at the rear end of the liquid injection groove 19. A one-way valve 32 is sleeved on the body of the liquid flow pipe 31.

[0047] A plurality of iron cores 17 are arranged in the middle of the shaft body of the rotating shaft 6, a mounting groove 34 is provided at the center of the outer wall of the front end of the iron core 17, a plurality of slots 35 are provided on the inner wall of the mounting groove 34, a rotor winding 24 is sleeved on the outer wall of the iron core 17, a terminal box 4 is fixedly connected to one side of the outer wall of the housing 1, and an anti-rust paint 33 is provided on the outer wall of the iron core 17;

[0048] By spraying anti-rust paint 33 on the outside of the iron core 17 and then using silicon steel sheets on the iron core 17, the anti-rust performance of the entire rotor can be effectively improved, thereby indirectly improving the overall performance of the DC motor, thereby avoiding the problem of rust on the iron core 17 due to exposure of the iron core 17 to humid air in the later stage.

[0049] Bearings 18 are provided at the center of the sealing plate 11 and the inner wall of the front cover 7, and the inner walls of the bearings 18 are respectively fixedly connected to the shaft body of the rotating shaft 6. Bearings 18 are provided at the center of the sealing plate 11 and the inner wall of the front cover 7, and the inner walls of the bearings 18 are respectively fixedly connected to the shaft body of the rotating shaft 6, so that the rotating shaft 6 can be better rotated while supporting the rotating shaft 6. A plurality of heat sinks 8 are fixedly connected to the outer wall of the shell 1, and a plurality of heat sinks 8 are fixedly connected to the outer wall of the shell 1, so that the heat dissipation effect can be better cooperated with the fan blades 9. The lower end of the outer wall of the shell 1 is fixedly connected to two support seats 5, and the lower end of the outer wall of the shell 1 is fixedly connected to two support seats 5, so that the motor can be better placed.

[0050] A plurality of air holes 16 are provided on the rear end outer wall of the second clutch plate 13, and the outer walls of the first clutch plate 12 and the second clutch plate 13 on the side close to each other are tightly fitted. The rear end outer wall of the fixing column 14 is fixedly connected to the edge of the front end outer wall of the rotating disk 22. A plurality of air holes 16 are provided on the rear end outer wall of the second clutch plate 13, and the outer walls of the first clutch plate 12 and the second clutch plate 13 on the side close to each other are tightly fitted. When the first clutch plate 12 and the second clutch plate 13 are fitted, the air holes 16 can better discharge the heat generated by friction, and then the rear end outer wall of the fixing column 14 is fixedly connected to the edge of the front end outer wall of the rotating disk 22, so that the second clutch plate 13 can better drive the rotating disk 22 to rotate.

[0051] A placement groove 23 is opened inside the rotating disk 22, and the rotating disk 22 is rotatably connected to the electric hydraulic rod 15 through the placement groove 23. A placement groove 23 is opened inside the rotating disk 22, and the rotating disk 22 is rotatably connected to the electric hydraulic rod 15 through the placement groove 23, so that the second clutch plate 13 can better drive the rotating disk 22 to rotate, thereby rotating the fan blades 9, thereby cooling the motor.

[0052] The inner wall of the mounting groove 34 fits tightly with the outer wall of the rotating shaft 6, the clamping groove 35 is clamped with the clamping plate 27, and the outer wall of the limiting plate 26 and the fixing plate 25 on one side close to the middle of the rotating shaft 6 fits tightly with the front outer wall of the front end iron core 17 and the rear outer wall of the rear end iron core 17. The inner wall of the mounting groove 34 fits tightly with the outer wall of the rotating shaft 6, and the clamping groove 35 is clamped with the clamping plate 27, so that the iron core 17 can be fixed on the shaft body of the rotating shaft 6 more firmly, and then the outer wall of the limiting plate 26 and the fixing plate 25 on one side close to the middle of the rotating shaft 6 fits tightly with the front outer wall of the front end iron core 17 and the rear outer wall of the rear end iron core 17, so that the iron core 17 can be fixed more firmly through the limiting plate 26 and the fixing plate 25.

[0053] The movable cavity 29 is connected with the liquid injection groove 19 through the liquid flow tube 31, and the outer wall of the movable plate 28 is provided with a sealing gasket 30. The movable cavity 29 is connected with the liquid injection groove 19 through the liquid flow tube 31, and the outer wall of the movable plate 28 is provided with a sealing gasket 30, so that the multiple iron cores 17 can be better fixed through the fixed plate 25, avoiding the problem of more troublesome installation in the past. A plurality of ventilation grooves 3 are opened at the edge of the front end outer wall of the rear cover 2, and the ventilation grooves 3 are connected with the interior of the rear cover 2. A plurality of ventilation grooves 3 are opened at the edge of the front end outer wall of the rear cover 2, and the ventilation grooves 3 are connected with the interior of the rear cover 2, so that the motor can be better cooled.

[0054] Working principle: During assembly, multiple iron cores 17 are sleeved on the rotating shaft 6 through the installation grooves 34, and then the card slots 35 are aligned with the card plate 27, and then the iron core 17 is installed on the rotating shaft 6. After installation, hydraulic oil is injected into the flow pipe 31 through the injection groove 19, and then the hydraulic oil enters the inside of the active chamber 29 through the one-way valve 32 to push the active plate 28 to move, so that the active plate 28 drives the fixed plate 25 to move, so that multiple iron cores 17 are fixed to the upper end of the rotating shaft 6, so that the iron core 17 can be quickly installed, and then the front cover 7 is fixed to the housing 1 by bolts, and the rear cover 2 is connected to the housing 1 by threads, and then in daily use, through The rotating shaft 6 is connected to the object, and then when the temperature of the motor is too high, the electric hydraulic rod 15 is used to drive the second clutch plate 13 to extend, and then the second clutch plate 13 is slowly brought into contact with the first clutch plate 12, and then the first clutch plate 12 drives the second clutch plate 13 to rotate, and then the second clutch plate 13 drives the rotating disk 22 to rotate through the fixed column 14, so that the rotating disk 22 drives the fan blades 9 to rotate, so that the fan blades 9 absorb external gas and discharge it from the ventilation groove 3, thereby cooling the DC motor, so that the load can be effectively reduced when the DC motor is initially started, and the damage to the motor caused by the motor temperature being too low can be effectively avoided.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An improved rotor of a permanent magnet brushless DC motor, comprising a housing (1), characterized in that: The front end of the housing (1) is provided with a front cover (7), the rear end of the housing (1) is provided with a rear cover (2), the rear end of the inner wall of the rear cover (2) is fixedly connected to a grille (10), the center of the front end outer wall of the grille (10) is fixedly connected to an electric hydraulic rod (15), the rod body of the electric hydraulic rod (15) is sleeved with a rotating disk (22), the outer wall of the rotating disk (22) is fixedly connected to a plurality of blades (9), the output end of the electric hydraulic rod (15) is rotatably connected to a second clutch plate (13), and the edge of the rear end outer wall of the second clutch plate (13) is fixedly connected to a plurality of fixing columns (14); The inner wall of the housing (1) is fixedly connected to a plurality of stators (21), the outer walls of the stators (21) are sleeved with stator windings (20), the rear end of the inner wall of the housing (1) is fixedly connected to a sealing plate (11), a rotating shaft (6) is arranged inside the housing (1), the rear end of the rotating shaft (6) passes through the sealing plate (11) and is fixedly connected to a first clutch plate (12), the rear end of the shaft body of the rotating shaft (6) is fixedly connected to a limiting plate (26), and the middle part of the shaft body of the rotating shaft (6) is fixedly connected to a A plurality of clamping plates (27) are connected, a liquid injection groove (19) is provided on the front end outer wall of the rotating shaft (6), a movable cavity (29) is provided inside the rotating shaft (6), a plurality of movable plates (28) are provided inside the movable cavity (29), a fixed plate (25) is fixedly connected to the outer wall of one side of the movable plate (28) away from the inner center of the rotating shaft (6), a liquid flow pipe (31) is provided at the rear end of the liquid injection groove (19), and a one-way valve (32) is sleeved on the pipe body of the liquid flow pipe (31); A plurality of iron cores (17) are arranged in the middle of the shaft body of the rotating shaft (6); a mounting groove (34) is provided at the center of the outer wall of the front end of each iron core (17); a plurality of clamping grooves (35) are provided on the inner wall of each mounting groove (34); a rotor winding (24) is sleeved on the outer wall of each iron core (17); a terminal box (4) is fixedly connected to one side of the outer wall of the housing (1); and an anti-rust paint (33) is provided on the outer wall of each iron core (17).

2. The improved rotor of a permanent magnet brushless DC motor according to claim 1, characterized in that: A bearing (18) is provided at the center of the inner wall of the sealing plate (11) and the front cover (7), and the inner wall of the bearing (18) is respectively fixedly connected to the shaft body of the rotating shaft (6).

3. The improved rotor of a permanent magnet brushless DC motor according to claim 1, characterized in that: A plurality of heat sinks (8) are fixedly connected to the outer wall of the housing (1).

4. The improved rotor of a permanent magnet brushless DC motor according to claim 1, characterized in that: The lower end of the outer wall of the shell (1) is fixedly connected to two support seats (5).

5. The improved rotor of a permanent magnet brushless DC motor according to claim 1, characterized in that: The rear end outer wall of the second clutch plate (13) is provided with a plurality of air holes (16); the outer walls of the first clutch plate (12) and the second clutch plate (13) on one side close to each other are tightly fitted; and the rear end outer wall of the fixing column (14) is fixedly connected to the edge of the front end outer wall of the rotating disk (22).

6. The improved rotor of a permanent magnet brushless DC motor according to claim 1, characterized in that: A placement groove (23) is provided inside the rotating disk (22), and the rotating disk (22) is rotationally connected to the electric hydraulic rod (15) via the placement groove (23).

7. The improved rotor of a permanent magnet brushless DC motor according to claim 1, characterized in that: The inner wall of the mounting groove (34) is tightly fitted with the outer wall of the rotating shaft (6), the clamping groove (35) is clamped and matched with the clamping plate (27), and the outer wall of one side of the limiting plate (26) and the fixing plate (25) close to the middle of the rotating shaft (6) are tightly fitted with the front outer wall of the front iron core (17) and the rear outer wall of the rear iron core (17).

8. The improved rotor of a permanent magnet brushless DC motor according to claim 1, characterized in that: The movable chamber (29) is connected to the liquid injection groove (19) via a liquid flow pipe (31), and a sealing gasket (30) is provided on the outer wall of the movable plate (28).

9. The improved rotor of a permanent magnet brushless DC motor according to claim 1, characterized in that: A plurality of ventilation grooves (3) are provided at the edge of the front end outer wall of the rear cover (2), and the ventilation grooves (3) are connected to the interior of the rear cover (2).

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