| CPC H02K 9/06 (2013.01) [A47L 5/22 (2013.01); A47L 9/0081 (2013.01); F04D 25/0606 (2013.01); F04D 29/4253 (2013.01); F04D 29/441 (2013.01); F04D 29/5806 (2013.01); H02K 5/04 (2013.01); H02K 5/207 (2021.01); H02K 7/14 (2013.01); F05D 2250/52 (2013.01)] | 15 Claims | 

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               1. A centrifugal fan, comprising a housing, an impeller, a diffuser, a rotor assembly and a stator assembly, 
            wherein the centrifugal fan has an air inlet and an air outlet, the air inlet is disposed on the housing, the impeller and the diffuser are disposed in the housing, the impeller is disposed adjacent to the air inlet and is connected to the rotor assembly, the diffuser is located downstream of the impeller, the stator assembly is located downstream of the diffuser; 
                wherein the housing comprises a front housing and a rear housing connected to each other, a first air duct is enclosed among a rear inner wall of the front housing, a front inner wall of the rear housing and the diffuser, the first air duct is in communication with an outlet of the impeller and the air outlet, and an inner diameter size of the rear end of the rear inner wall is less than or equal to an inner diameter size of the front end of the front inner wall; 
                wherein the entirety of the first air duct is only formed by the rear inner wall of the front housing, the front inner wall of the rear housing and the diffuser and a longitudinal cross-section of the first air duct is U-shaped; 
                wherein the front inner wall of the rear housing comprises a first inner wall section, a second inner wall section, and a third inner wall section which are connected in sequence, a longitudinal cross-section of the first inner wall section is linear along the axial direction of the impeller, a longitudinal cross-section of the second inner wall section is in an arc shape which is concavely curved relative to the diffuser, a longitudinal cross-section of the third inner wall section is linear along the radial direction of the impeller, and the first inner wall section forms the front end of the front inner wall; and 
                wherein the diffuser comprises an annular plate, which is located radially outward of the impeller along the radial direction of the impeller, the annular plate comprises a front plane near the impeller, a rear plane near the stator assembly and a radial outer surface connected with the front plane and the rear plane and located between the front plane and the rear plane along the axial direction of the impeller, each of the front plane and the rear plane has a longitudinal cross-section in a straight line shape along the radial direction of the impeller respectively, the rear plane faces the third inner wall section of the rear housing, and an interval between the rear plane and the third inner wall section forms a part of the first air duct. 
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               11. A vacuum cleaner, comprising a centrifugal fan, 
            wherein the centrifugal fan comprises a housing, an impeller, a diffuser, a rotor assembly and a stator assembly; 
                wherein the centrifugal fan has an air inlet and an air outlet, the air inlet is disposed on the housing, the impeller and the diffuser are disposed in the housing, the impeller is disposed adjacent to the air inlet and is connected to the rotor assembly, the diffuser is located downstream of the impeller, the stator assembly is located downstream of the diffuser; 
                wherein the housing comprises a front housing and a rear housing which are connected to each other, a first air duct is enclosed among a rear inner wall of the front housing, a front inner wall of the rear housing and the diffuser, the first air duct is in communication with an outlet of the impeller and the air outlet, and an inner diameter size of the rear end of the rear inner wall is less than or equal to an inner diameter size of the front end of the front inner wall; 
                wherein the entirety of the first air duct is only formed by the rear inner wall of the front housing, the front inner wall of the rear housing and the diffuser and a longitudinal cross-section of the first air duct is U-shaped; 
                wherein the front inner wall of the rear housing comprises a first inner wall section, a second inner wall section, and a third inner wall section which are connected in sequence, a longitudinal cross-section of the first inner wall section is linear along the axial direction of the impeller, a longitudinal cross-section of the second inner wall section is in an arc shape which is concavely curved relative to the diffuser, a longitudinal cross-section of the third inner wall section is linear along the radial direction of the impeller, and the first inner wall section forms the front end of the front inner wall; and 
                wherein the diffuser comprises an annular plate, which is located radially outward of the impeller along the radial direction of the impeller, the annular plate comprises a front plane near the impeller, a rear plane near the stator assembly and a radial outer surface connected with the front plane and the rear plane and located between the front plane and the rear plane along the axial direction of the impeller, each of the front plane and the rear plane has a longitudinal cross-section in a straight line shape along the radial direction of the impeller respectively, the rear plane faces the third inner wall section of the rear housing, and an interval between the rear plane and the third inner wall section forms a part of the first air duct. 
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