Heating core assembly for heat gun

Abstract

The utility model discloses a heating core assembly for a heat gun, which belongs to the technical field of electric tools and comprises a sleeve, a core frame, a heating element and a ceramic ring, the core frame, the heating element and the ceramic ring are positioned in the sleeve, the heating element is arranged on the core frame, the ceramic ring is positioned at the downstream of the heating element, an air outlet cover is arranged in front of the core frame, and the air outlet cover is arranged in front of the core frame. A ceramic ring is arranged between the core frame and the air outlet cover, the ceramic ring comprises a mounting part and an outer ring located on the periphery of the fixing part, the mounting part and the outer ring are connected through a plurality of connecting ribs, a ventilating duct is formed between every two adjacent connecting ribs, and a breaking seam enabling the outer ring to be broken in the circumferential direction is formed in the outer ring. The outer ring of the ceramic ring is provided with the breaking seam, so that the ceramic ring is broken in the circumferential direction, the situation that the ceramic ring is damaged due to thermal expansion is avoided, and the service life of the ceramic ring is guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of electric tools, in particular to a heating core assembly for a hot air gun. Background Art

[0002] The heating core assembly is an important component of the hot air gun. The heating core assembly is provided with a heating wire that is heated by electricity. The airflow formed by the rotation of the fan driven by the motor flows through the heating core assembly to form a high-temperature hot air flow. The hot air flow can be used for welding components, removing components, removing old paint on metal surfaces, removing self-adhesive stickers, heating packaging films, heating packaging tubes, etc. In order to make the temperature of the hot air flow more uniform, a ceramic ring is usually provided downstream of the heating wire. The ceramic ring includes a mounting portion and an outer ring located outside the mounting portion. The hot air flow passes through the ceramic ring and then blows out. However, since the thermal expansion and contraction coefficient of the ceramic material is small, that is, the deformation is small, and the temperature of the hot air flow is high, the temperature of the ceramic ring is high, and the thermal stress generated by the ceramic ring during thermal expansion rises rapidly, especially the outer ring, which has a large thermal stress and is prone to rupture, affecting the service life of the ceramic ring. Utility Model Content

[0003] In order to solve the shortcomings and deficiencies in the above-mentioned prior art, the utility model provides a heating core assembly for a hot air gun, in which a disconnection seam is arranged on the outer ring of the ceramic ring so that the ceramic ring is disconnected in the circumferential direction, thereby preventing the ceramic ring from being damaged due to thermal expansion and ensuring the service life of the ceramic ring.

[0004] In order to achieve the above technical objectives, the utility model provides a heating core assembly for a hot air gun, comprising a sleeve, a core frame, a heating element and a ceramic ring, wherein the core frame, the heating element and the ceramic ring are located in the sleeve, the heating element is arranged on the core frame, the ceramic ring is located downstream of the heating element, a ceramic ring is arranged between the core frame and the air outlet cover, the ceramic ring comprises a mounting portion and an outer ring located at the outer periphery of the mounting portion, the mounting portion and the outer ring are connected by a plurality of connecting ribs, a ventilation duct is formed between two adjacent connecting ribs, and a disconnection seam is provided on the outer ring to disconnect it in the circumferential direction.

[0005] Preferably, there is at least one disconnecting seam, and the at least one disconnecting seam is arranged on the outer ring at intervals along the circumferential direction.

[0006] Preferably, the disconnection seam is located on the outer ring between two adjacent connecting ribs.

[0007] Preferably, a ventilation gap is provided between the connecting rib and the core frame, and the two adjacent ventilation passages are connected through the ventilation gap.

[0008] Preferably, the mounting portion is provided with a disconnection groove for partially disconnecting it.

[0009] Preferably, a through hole penetrating front to back is provided at the center of the core frame, and a ventilation hole corresponding to the through hole is provided on the mounting portion.

[0010] Preferably, the outer ring and the inner wall of the sleeve have an avoidance gap, and the avoidance gap penetrates along the front-to-back direction.

[0011] Preferably, a mounting bracket is provided between the ceramic ring and the core frame, the ceramic ring is connected to the core frame via the mounting bracket, and a vent is provided on the mounting bracket.

[0012] Preferably, the mounting portion is further provided with an air inlet slot arranged toward the core frame, the projection of the air inlet slot along the front-to-back direction is staggered with the projection of the mounting bracket along the front-to-back direction, and a connecting opening is provided between the air inlet slot and the ventilation hole.

[0013] Preferably, the sleeve is also provided with an air guide plate and a plurality of air guide ribs, and the air guide plates and the plurality of air guide ribs are located downstream of the ceramic ring, the projection of the air guide plates in the front-to-back direction covers the projection of the mounting part in the front-to-back direction, the plurality of air guide ribs are radially distributed with the air guide plates as the center, and an air guide duct is formed between two adjacent air guide ribs.

[0014] After adopting the above technical solution, the utility model has the following advantages:

[0015] 1. The heating core assembly for a hot air gun provided by the utility model has a disconnection seam on the outer ring that disconnects it in the circumferential direction, thereby reducing the thermal stress generated by the outer ring during thermal expansion or rapid temperature changes, reducing the risk of rupture of the outer ring, thereby ensuring the service life of the ceramic ring, meeting the use requirements of the ceramic ring in a high temperature environment, and also reducing other stress concentrations inside the outer ring, increasing its overall strength and stability, and effectively preventing the ceramic ring from cracking or breaking during use.

[0016] 2. There is at least one disconnection seam, which is arranged at intervals along the circumferential direction on the outer ring. The setting of at least one disconnection seam can reduce the stress concentration inside the outer ring, reduce the thermal stress of the outer ring under high-temperature working conditions, and further reduce the risk of rupture of the ceramic ring. The more disconnection seams there are, the better the thermal stress release effect inside the outer ring.

[0017] 3. The disconnection seam is located on the outer ring between two adjacent connecting ribs, which can effectively reduce the thermal stress of the outer ring, and the disconnected outer ring is connected to the mounting part through two adjacent connecting ribs, which can ensure the structural strength of the outer ring.

[0018] 4. A ventilation gap is provided between the connecting rib and the core frame. Two adjacent ventilation ducts are connected through the ventilation gap. Hot air can enter the adjacent ventilation duct through the ventilation gap, which can make the heat more evenly distributed on the surface of the ceramic ring and avoid local overheating of the ceramic ring and generate greater thermal stress.

[0019] 5. A disconnection groove is provided on the mounting part to partially disconnect it, so as to release the thermal stress on the mounting part, reduce the risk of cracking of the mounting part, and further ensure the service life of the ceramic ring.

[0020] 6. A through hole extending from front to back is provided at the center of the core frame, and a ventilation hole corresponding to the through hole is provided on the mounting portion, so that the hot air in the core frame can be directly output from the ventilation hole, reducing the resistance to the hot air, and the temperature of the hot air output from the core frame is relatively low, which can reduce the temperature of the ceramic ring and reduce the thermal stress of the ceramic ring.

[0021] 7. There is an avoidance gap between the outer ring and the inner wall of the sleeve, so that there is enough space between the outer ring and the inner wall of the sleeve to accommodate the radial expansion part of the outer ring due to heat, which is beneficial to avoid the expansion part of the outer ring squeezing the inner wall of the sleeve, thereby avoiding the outer ring and the inner wall of the sleeve from being squeezed and damaged.

[0022] 8. A mounting bracket is provided between the ceramic ring and the core frame. The ceramic ring is connected to the core frame through the mounting bracket. A vent is provided on the mounting bracket to facilitate the passage of hot air passing through the heating wire. The ceramic ring can effectively dissipate the heat of the hot air.

[0023] 9. The projection of the air inlet slot along the front-to-back direction is staggered with the projection of the mounting bracket along the front-to-back direction, which is beneficial to avoid the air inlet slot being blocked by the mounting bracket. A connecting port is provided between the air inlet slot and the ventilation hole, which can increase the air intake of the ventilation hole.

[0024] 10. The air guide plate and multiple air guide ribs are located downstream of the ceramic ring. The projection of the air guide plate in the front-to-back direction covers the projection of the mounting part in the front-to-back direction. The multiple air guide ribs are radially distributed with the air guide plate as the center. An air guide duct is formed between two adjacent air guide ribs, so that the hot air with a lower temperature output from the mounting part is diffused to the surroundings through the guidance of the air guide ring, and then mixed with the hot air with a higher temperature output from the outer ring and output from the air guide duct, thereby making the temperature of the hot air output by the hot air gun more stable, which is beneficial to improving the operating effect of the hot air gun. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a structural diagram of the heating core assembly in this utility model patent;

[0026] Figure 2 This is an exploded view of the heating core assembly in this utility model patent;

[0027] Figure 3 This is a structural cross-sectional view of the heating core assembly in the utility model patent;

[0028] Figure 4 It is a partial structural diagram of the heating core assembly in this utility model patent;

[0029] Figure 5 This is a cross-sectional view of the heating core assembly from another perspective in the utility model patent;

[0030] Figure 6 This is a structural diagram of the ceramic ring in the heating core assembly of the utility model patent;

[0031] Figure 7 This is another perspective structural diagram of the ceramic ring in the heating core assembly of the utility model patent;

[0032] In the figure, 101, ceramic sleeve; 102, mica sleeve; 103, metal sleeve; 110, core frame; 111, ceramic positioning member; 112, mica sheet; 113, slot; 114, mounting slot; 115, heating zone; 116, through hole; 120, heating element; 130, ceramic ring; 131, mounting portion; 132, outer ring; 133, disconnection seam; 134, connecting rib; 135, ventilation duct; 136, groove; 137, ventilation hole; 138, air inlet slot; 139, connecting port; 140, mounting bracket; 141, positioning slot; 142, ventilation port; 150, air outlet cover; 151, air guide plate; 152, air guide rib; 153, air guide duct; 160, avoidance gap; 170, temperature protector; 180, conductive member. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following words indicating orientation or positional relationship such as "upper", "lower", "left", "right", "longitudinal", "lateral", "inner", "outer", "vertical", "horizontal", "top", "bottom", etc. are only based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device / element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0034] Combination Figures 1 to 7 The utility model provides a heating core assembly for a hot air gun, comprising a sleeve, a core frame 110, a heating element 120 and a ceramic ring 130. The core frame 110, the heating element 120 and the ceramic ring 130 are located in the sleeve, the heating element 120 is arranged on the core frame 110, the ceramic ring 130 is located downstream of the heating element 120, the ceramic ring 130 comprises a mounting portion 131 and an outer ring 132 located at the outer periphery of the mounting portion 131, the mounting portion 131 and the outer ring 132 are connected by a plurality of connecting ribs 134, a ventilation duct 135 is formed between two adjacent connecting ribs 134, and a disconnection seam 133 is provided on the outer ring 132 to disconnect it in the circumferential direction.

[0035] When the hot air gun is working, the temperature of the hot air after being heated by the heating element 120 is relatively high. When the hot air passes through the ceramic ring 130, the temperature of the ceramic ring 130 rises rapidly. The outer ring 132 is provided with a disconnection seam 133 that disconnects it in the circumferential direction. The thermal stress generated by the outer ring 132 during thermal expansion or sudden temperature changes can be reduced, thereby reducing the risk of rupture of the outer ring 132, ensuring the service life of the ceramic ring 130, and meeting the requirements for use of the ceramic ring 130 in a high temperature environment. It can also reduce other stress concentrations inside the outer ring 132, increase its overall strength and stability, and effectively prevent the ceramic ring 130 from cracking or breakage during use.

[0036] Preferably, the disconnected seam 133 is located on the outer ring 132 between two adjacent connecting ribs 134 , which can effectively reduce the thermal stress of the outer ring 132 , and the disconnected outer ring 132 is connected to the mounting portion 131 through two adjacent connecting ribs 134 , which can ensure the structural strength of the outer ring 132 .

[0037] Specific, combined Figures 2 to 5 As shown, the heating element 120 includes a plurality of heating wires spirally wound around the outer periphery of the core frame 110, the core frame 110 includes four ceramic positioning members 111 and two mica sheets 112, a slot 113 is provided on the mica sheet 112, the two mica sheets 112 are cross-arranged and cooperate with each other through the slot 113 to form four heating zones 115, the four ceramic positioning members 111 are respectively located in the four heating zones 115, a plurality of mounting grooves 114 spaced along the axial direction are provided on the ceramic positioning member 111, the heating wire is passed through the mounting groove 114, a clamping portion is provided between adjacent heating wires, a clamping groove cooperating with the clamping portion is provided on the mica sheet 112, the clamping portion cooperates with the clamping groove to install the heating wire in the corresponding heating zone 115, which is beneficial to reduce the uneven distribution of the heating wire or the occurrence of the heating wire being fitted due to thermal expansion and contraction. Among them, a mounting bracket 140 is provided on the mica sheet 112, and a positioning slot 141 that can cooperate with the mica sheet 112 is provided on the mounting bracket 140. The positioning slot 141 cooperates with the mica sheet 112 to make the mica sheets 112 relatively fixed. The ceramic ring 130 is fixedly connected to the mounting bracket 140, and a vent 142 is provided on the mounting bracket 140, which is conducive to the passage of hot air passing through the heating wire. The ceramic ring 130 can effectively dissipate the heat of the hot air.

[0038] It is understandable that the arrangement of the mica sheets 112 and the ceramic positioning members 111 is not limited to the above description and drawings. The mica sheets 112 can also be set in three, four, five or other appropriate numbers, and the ceramic positioning members 111 can also be set in three, four, five or other appropriate numbers.

[0039] It is understandable that the arrangement of the heating wire and the mounting groove 114 is not limited to the above description and drawings. The mounting groove 114 can also be arranged to be distributed at intervals along the circumferential direction. Accordingly, the heating wire is arranged in the mounting groove 114 along the front-to-back direction.

[0040] In order to make the hot air in the heating zone 115 output more timely, combined with Figure 6 and Figure 7 As shown, in this embodiment, the projection of the ventilation duct 135 in the front-to-back direction covers the projection of the heating zone 115 in the front-to-back direction, so that the hot air in the heating zone 115 can be output more smoothly from the ventilation duct 135, reducing the resistance to the circulation of the hot air.

[0041] Among them, the combination Figure 4 and Figure 6 As shown, a ventilation gap is provided between the connecting rib 134 and the core frame 110, and two adjacent ventilation channels 135 are connected through the ventilation gap, and hot air can enter the adjacent ventilation channel 135 through the ventilation gap, so that the heat can be more evenly distributed on the surface of the ceramic ring 130, avoiding local overheating of the ceramic ring 130 and generating large thermal stress. Specifically, a groove 136 is provided on one side of the connecting rib 134 close to the core frame 110, and the groove 136 forms a ventilation gap.

[0042] In order to further facilitate the passage of hot air, the disconnection slit 133 is arranged toward the core frame 110 and penetrates along the front-to-back direction, so that the hot air can pass directly and the resistance to the passage of the hot air can be reduced.

[0043] It is understandable that the arrangement of the disconnecting slits 133 is not limited to the above description and the drawings. The disconnecting slits 133 can also be arranged obliquely along the front-to-back direction to increase the contact area with the ceramic ring 130 and improve the heat dissipation effect.

[0044] Combination Figure 6 and Figure 7 As shown, since the circumferential size of the outer ring 132 is large, the release effect of thermal stress is related to the distance. Preferably, in this embodiment, two disconnecting slits 133 are provided, and the two disconnecting slits 133 are arranged on the outer ring 132 at intervals along the circumferential direction, so that the thermal stress on the ceramic ring 130 can be better released, further reducing the risk of rupture of the outer ring 132.

[0045] It can be understood that the number and arrangement of the disconnecting slits 133 are not limited to the above description and the drawings. The disconnecting slits 133 can be one, three, four or other suitable numbers, and the disconnecting slits 133 can also be arranged in a suitable arrangement such as equidistant arrangement to avoid local stress concentration in the outer ring 132.

[0046] Combination Figure 3 and Figure 5As shown, due to the fact that the outer ring 132 may expand in the radial direction as well as the circumferential direction during thermal expansion, in this embodiment, an avoidance gap 160 is provided between the outer ring 132 and the inner wall of the sleeve. The avoidance gap 160 is connected in the front-to-back direction, so that there is enough space between the outer ring 132 and the inner wall of the sleeve to accommodate the radially expanded part of the outer ring 132 due to heat, which helps to avoid the expanded part of the outer ring 132 squeezing the inner wall of the sleeve, thereby avoiding the outer ring 132 and the inner wall of the sleeve from being squeezed and damaged.

[0047] It is understandable that a compressible buffer may also be provided between the outer ring 132 and the inner wall of the sleeve. The buffer releases the stress generated by the outer ring 132 through compression deformation. The buffer may also support the outer ring 132 and improve the installation stability of the outer ring 132 .

[0048] Combination Figure 5 As shown, since the air cannot directly penetrate into the core frame 110, heat is easily accumulated inside the core frame 110. Therefore, in this embodiment, a through hole 116 is provided at the center of the core frame 110, which runs through the front and back, so that air can enter the core frame 110 through the through hole 116, which is conducive to reducing the temperature inside the core frame 110 and ensuring the service life of the core frame 110. Accordingly, a ventilation hole 137 corresponding to the through hole 116 is provided on the mounting portion 131, so that the hot air output from the core frame 110 can be directly output from the ventilation hole 137, reducing the resistance to the hot air, and the temperature of the hot air output from the core frame 110 is lower than that of the hot air output from the heating area 115, which can reduce the temperature of the ceramic ring 130, thereby reducing the thermal stress of the ceramic ring 130.

[0049] It is understandable that the mounting portion 131 may not be provided with the ventilation holes 137 , which can improve the structural strength of the mounting portion 131 , and the hot air output from the core frame 110 can be directly output from the ventilation duct 135 to reduce the temperature of the outer ring 132 .

[0050] Combination Figure 5As shown, since the mounting bracket 140 may block the ventilation hole 137 and the ventilation duct 135, in the present embodiment, two adjacent ventilation ducts 135 are connected by a groove 136, and hot air can enter the adjacent ventilation duct 135 through the groove 136, so that the heat can be more evenly distributed on the surface of the ceramic ring 130, thereby avoiding local overheating of the ceramic ring 130 and generating greater thermal stress. In addition, the mounting portion 131 is also provided with an air inlet groove 138 arranged toward the core frame 110, and the projection of the air inlet groove 138 along the front-to-back direction is staggered with the projection of the mounting bracket 140 along the front-to-back direction, which is beneficial to avoid the air inlet groove 138 from being blocked. A connecting port 139 is provided between the air inlet groove 138 and the ventilation hole 137, which can increase the air intake of the ventilation hole 137. In addition, since the air inlet groove 138 is not arranged to pass through the mounting portion 131, the structural strength of the mounting portion 131 can also be guaranteed.

[0051] It can be understood that in other embodiments, the mounting portion is also provided with a disconnection groove for partially disconnecting the mounting portion, so as to release the thermal stress on the mounting portion and avoid cracking of the mounting portion.

[0052] Combination Figure 1 As shown, in order to further make the temperature of the hot air output by the hot air gun more uniform, in this embodiment, an air outlet cover 150 is further provided downstream of the ceramic ring 130, and the air outlet cover 150 includes an air guide plate 151 and a plurality of air guide ribs 152. The projection of the air guide plate 151 in the front-to-back direction covers the projection of the mounting portion 131 in the front-to-back direction. The plurality of air guide ribs 152 are radially distributed with the air guide plate 151 as the center, and an air guide duct 153 is formed between two adjacent air guide ribs 152, so that the hot air with a lower temperature output from the mounting portion 131 is diffused to the surroundings through the guidance of the air guide ring, and then mixed with the hot air with a higher temperature output from the outer ring 132 and then output from the air guide duct 153, so that the temperature of the hot air output by the hot air gun is more stable, which is beneficial to improving the operating effect of the hot air gun.

[0053] Combination Figure 2 and Figure 3As shown, finally, in this embodiment, the heating core assembly also includes a temperature protector 170 and a conductive member 180. The thermal conductive member and the temperature protector 170 are arranged at the rear end of the mica sheet 112. The conductive member 180 is used to connect the heating element 120 to the power supply circuit. The temperature protector 170 is connected in parallel with the heating element 120 to adjust the power-carrying current of the heating element 120 and control the temperature of the heating element 120, so as to make the heating core assembly safer to use. The sleeve includes a ceramic sleeve 101 sleeved on the outside of the core frame 110, a mica sleeve 102 sleeved on the outside of the ceramic sleeve 101, and a metal sleeve 103 sleeved on the outside of the ceramic sleeve 101. The axial length of the ceramic sleeve 101 is equal to the axial length of the mica sleeve 102, the axial length of the ceramic sleeve 101 is slightly larger than the axial length of the core frame 110, and the front end of the ceramic sleeve 101 extends forward beyond the front end of the core frame 110. The length of the metal sleeve 103 is slightly larger than the mica sleeve 102, and the front end of the metal sleeve 103 extends forward beyond the front end of the mica sleeve 102. The ceramic ring 130 is located in the metal sleeve 103. The metal sleeve 103 usually has good thermal conductivity, which enables the heat of the ceramic ring 130 to be quickly conducted through the metal sleeve 103 and dissipated to the surrounding environment, thereby reducing the temperature of the ceramic ring 130 and thus reducing the thermal stress inside the ceramic ring 130.

[0054] In order to improve the structural strength of the heating core assembly, in the present embodiment, the air outlet cover 150 and the metal sleeve 103 are integrally injection molded. When high-speed hot air passes through the air outlet cover 150, no large floating vibration will occur between the air outlet cover 150 and the metal sleeve 103, and the air outlet noise is small.

[0055] It is understandable that the connection method between the air outlet cover 150 and the metal sleeve 103 is not limited to the above description and drawings. The air outlet cover 150 and the metal sleeve 103 can also be detachably connected to facilitate the later replacement and maintenance of the air outlet cover 150.

[0056] In addition to the above preferred embodiments, the present invention has other implementation modes. Those skilled in the art can make various changes and modifications based on the present invention. As long as they do not deviate from the spirit of the present invention, they should all fall within the scope defined in the claims of the present invention.

Claims

1. A heating core assembly for a hot air gun, comprising a sleeve, a core frame, a heating element and a ceramic ring, wherein the core frame, the heating element and the ceramic ring are located in the sleeve, the heating element is arranged on the core frame, and the ceramic ring is located downstream of the heating element, characterized in that: The ceramic ring includes a mounting portion and an outer ring located at the outer periphery of the mounting portion. The mounting portion and the outer ring are connected by a plurality of connecting ribs, a ventilation passage is formed between two adjacent connecting ribs, and a disconnection seam is provided on the outer ring to disconnect it in the circumferential direction.

2. The heating core assembly for a hot air gun according to claim 1, characterized in that: There is at least one breaking seam, and the at least one breaking seam is arranged on the outer ring at intervals along the circumferential direction.

3. The heating core assembly for a hot air gun according to claim 1, characterized in that: The disconnection seam is located on the outer circle between two adjacent connection ribs.

4. The heating core assembly for a hot air gun according to claim 1, characterized in that: A ventilation gap is provided between the connecting rib and the core frame, and the two adjacent ventilation passages are connected through the ventilation gap.

5. The heating core assembly for a hot air gun according to claim 1, characterized in that: The mounting portion is provided with a disconnection groove for partially disconnecting the mounting portion.

6. The heating core assembly for a hot air gun according to claim 1, characterized in that: A through hole penetrating front to back is arranged at the center of the core frame, and a ventilation hole corresponding to the through hole is arranged on the mounting portion.

7. The heating core assembly for a hot air gun according to claim 1, characterized in that: The outer ring and the inner wall of the sleeve have an escape gap, and the escape gap penetrates along the front-to-back direction.

8. The heating core assembly for a hot air gun according to claim 1, characterized in that: A mounting bracket is also provided between the ceramic ring and the core frame, the ceramic ring is connected to the core frame through the mounting bracket, and a vent is provided on the mounting bracket.

9. The heating core assembly for a hot air gun according to claim 8, characterized in that: The mounting portion is also provided with an air inlet slot arranged toward the core frame, the projection of the air inlet slot along the front-to-back direction is staggered with the projection of the mounting bracket along the front-to-back direction, and a connecting port is provided between the air inlet slot and the ventilation hole.

10. The heating core assembly for a hot air gun according to claim 1, characterized in that: The sleeve is also provided with an air guide plate and a plurality of air guide ribs, which are located downstream of the ceramic ring. The projection of the air guide plate in the front-to-back direction covers the projection of the mounting portion in the front-to-back direction. The plurality of air guide ribs are radially distributed with the air guide plate as the center, and an air guide duct is formed between two adjacent air guide ribs.

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