JP5215962B2 - Noise prevention structure for centrifugal cooling fan - Google Patents

Description

  The present invention relates to a noise prevention structure for a centrifugal cooling fan.

  Patent Document 1 discloses a structure of a conventional centrifugal cooling fan. This is a centrifugal cooling fan having a plurality of backward airfoil blades, the tips of the fans are connected, and the heights of all the blades from the blade standing surface of the impeller are equal. .

Japanese Examined Patent Publication No. 6-58115

  The present invention is intended to eliminate blade resonance noise corresponding to various rotational speeds of an internal combustion engine and to secure a sufficient air volume even at a low rotational speed.

The present invention solves the above problems, and the invention according to claim 1
In the noise prevention structure of the centrifugal cooling fan attached to the crankshaft of the internal combustion engine and generating cooling air by the impeller according to the changing rotational speed,
On impeller blade standing設面, blade group comprising a plurality of blades is erected, the height from the impeller mounting surface to each blade tip is a plurality of types, in the blades, next to the pair A noise prevention structure for a centrifugal cooling fan, wherein matching blades having the same height are arranged at a plurality of positions at predetermined intervals .

According to a second aspect of the present invention, in the noise prevention structure for the centrifugal cooling fan according to the first aspect , the pair of adjacent blades having the same height is the highest blade in the blade group. It is a feature.

According to a third aspect of the present invention, in the noise prevention structure for the centrifugal cooling fan according to the second aspect , the blade group is lower and higher than the pair of adjacent blades of the same height. A plurality of blades having different heights are provided, and blades having different heights are arranged before and after the pair of blades.

According to a fourth aspect of the present invention, in the noise prevention structure for the centrifugal cooling fan according to the third aspect , the cooling fan includes a mounting boss at a rotation center side end of the blade on the blade standing surface, and the boss A low blade is arranged on the rear side in the rotation direction.

According to a fifth aspect of the present invention, in the noise prevention structure for the centrifugal cooling fan according to the third aspect , the cooling fan includes a mounting boss at a rotation center side end of the blade on the blade standing surface, It is provided continuously with any one of the pair of blades.

According to a sixth aspect of the present invention, in the noise prevention structure for the centrifugal cooling fan according to the first , third, fourth, or fifth aspect , the planar shape of each blade is close to the center of rotation. The outer side is curved with a forward blade shape radially outward, a rear blade shape portion is added to the outer peripheral side, and is generally S-shaped.

According to a seventh aspect of the present invention, in the noise prevention structure for the centrifugal cooling fan according to the sixth aspect , the cooling fan is provided close to a radiator core portion of the radiator.

According to an eighth aspect of the present invention, in the noise prevention structure for the centrifugal cooling fan according to the seventh aspect , the blade group includes 18 blades, and three mounting bosses are provided. is there.

According to a ninth aspect of the present invention, in the noise prevention structure for the centrifugal cooling fan according to the seventh aspect , the shape of the edge of the blade on the radiator side is a shape orthogonal to the rotation axis.

In the invention of claim 1,
It is possible to reduce the blade resonance sound corresponding to the predetermined number of rotations of the internal combustion engine corresponding to the blade height.
In addition, since the cooling air between the pair of blades is radiated at a predetermined interval, the cooling air flowing out from other blades is guided by the cooling air in the radial direction described above, thereby reducing blade resonance noise. However, the cooling air can be sent out efficiently even at low rotation.

In the invention of claim 2,
The highest pair of blades can carry the largest amount of cooling air in the radial direction, and the guiding effect of the cooling air in the radial direction is increased, so that the cooling air can be efficiently delivered as a whole.

In the invention of claim 3,
Noise can be efficiently reduced by causing the cooling air flowing out from the front and rear blades of different heights to act on the radial cooling air flowing out from the pair of blades.

In the invention of claim 4,
By ensuring the height of the boss and securing the attachment strength to the mating member, it is possible to ensure the flow of cooling air from the blades on the rear side in the rotational direction of the boss.

In the invention of claim 5,
While ensuring the height of the boss and securing the attachment strength to the mating member, it is possible to compensate for the decrease in cooling air on the rear side in the rotational direction due to the boss.

In the invention of claim 8,
Resonance noise at high rotation can be reduced by the backward blade shape portion on the outer peripheral side while securing the air volume at low rotation by the forward blade shape on the side close to the rotation center.

In the invention of claim 7,
The power unit can be reduced in size while preventing noise and ensuring air volume by installing the blade tips close to the heat radiating core.

In the invention of claim 8,
Since three mounting bosses are provided for stable mounting and a small number of mounting bosses, it is possible to prevent noise while securing a flow in the radial direction by a pair of high blades not provided with bosses and improving air flow. .

In the invention of claim 9,
The blade can be enlarged so that the edge on the radiator side is parallel to the plane of the heat dissipation core without tilting, and the power unit can be downsized by bringing the tip of the blade closer to the heat dissipation core, preventing noise and ensuring airflow. Can be planned.

1 is a left side view of a motorcycle 2 equipped with a power unit 1 according to an embodiment of the present invention. It is a longitudinal cross-sectional left view of the power unit 1. FIG. It is III-III sectional drawing of FIG. FIG. 3 is a right side view of the power unit 1 with a radiator 67 and a radiator cover 68 removed. 4 is a right side view of the power unit 1 in a state where a radiator 67 is attached to the right side of the radiator cooling fan 63. FIG. FIG. 4 is a right side view of the power unit 1 with a radiator cover 68 attached to the right side of the radiator 67. External view of radiator cooling fan 63, VIII-VIII sectional view of FIG. Development view of the blade cross section showing the arrangement of the blades 90 from the center of the impeller 88 7 is a perspective view of the outer surface of the impeller 88. FIG. FIG. 10 is an external view of the radiator cooling fan 63 according to another embodiment of an impeller 95.

  FIG. 1 is a left side view of a motorcycle 2 equipped with a power unit 1 according to an embodiment of the present invention. The body frame of the motorcycle 2 includes a head pipe, a main frame extending rearwardly from the headpipe, a pair of left and right rear frames connected to a rear portion of the main frame and extending rearwardly, and a plurality of other frames. It consists of and. A front wheel 4 is pivotally supported at the lower end of the front fork 3 rotatably supported by the head pipe, and a steering handle 5 is connected to the upper portion of the front fork 3.

  The power unit 1 is suspended by a bracket fixed to the rear frame via a hanger 6 (FIG. 2) and a support shaft 7 (FIG. 2) integrally formed at the front portion thereof. A rear cushion 8 is provided between a bracket 14 (FIG. 2) provided at the rear end of the power unit 1 and a rear bracket of the rear frame. As a result, the power unit 1 is suspended so as to be able to swing with its cylinder axis slightly raised forward. A rear wheel 10 is attached to a rear axle 9 (FIG. 3) that protrudes rightward from the rear portion of the power unit 1, and is driven by the power unit 1.

  An air cleaner 11 is provided above the power unit 1. A synthetic resin body cover 13 made of a plurality of parts is attached to the body frame and covers the power unit 1 and other devices.

  FIG. 2 is a left side view of the vertical cross section of the power unit 1. “Front / Rear / Left / Right” used in the description of the power unit corresponds to “Front / Rear / Left / Right” of the vehicle equipped with the power unit. In FIG. 2, the power unit 1 includes a front internal combustion engine 16 and a transmission device 17 extending rearward from the left side of the internal combustion engine 16. The transmission device 17 includes a V-belt type continuously variable transmission 18 and a gear reducer 19.

  The internal combustion engine 16 is a rocker arm type overhead valve type 4-stroke cycle single cylinder water-cooled internal combustion engine. A throttle body 21 is attached to the inlet pipe 20 attached to the intake port on the upper side of the cylinder head 25, and an air cleaner 11 (FIG. 1) is connected to the rear thereof. A fuel injection valve 22 is attached to the inlet pipe 20.

  3 is a cross-sectional view taken along the line III-III in FIG. In FIG. 3, the shell of the internal combustion engine 16 comprises a crankcase 23, a cylinder block 24, a cylinder head 25, and a cylinder head cover 26, which are sequentially connected to the front of the crankcase 23. The crankcase 23 is a left and right split type, and is composed of a left crankcase 23L and a right crankcase 23R.

  The crankshaft 27 is rotatably supported by ball bearings 28A and 28B supported by the crankcase 23. The piston 29 is slidably fitted in a cylinder hole 30 formed in the cylinder block 24. The piston 29 is connected to the crankpin 32 of the crankshaft 27 via the connecting rod 31, and when the piston 29 reciprocates, the crankshaft 27 is driven to rotate. A combustion chamber 33 is formed on the bottom surface of the cylinder head 25 so as to face the top surface of the piston 29. The spark plug 34 is attached to the cylinder head 25 so as to incline to the left with respect to the central axis of the cylinder hole 30.

  In the left half of FIG. 3, the V-belt continuously variable transmission 18 is covered with a transmission case 37. The transmission case 37 includes a transmission case right side member 37R and a transmission case left side member 37L. The transmission case right member 37R is formed integrally with the left crankcase 23L. The transmission case left side member 37L is coupled to the transmission case right side member 37R by a bolt. The gear reducer 19 is covered with the rear portion of the transmission case right member 37R and the gear case 38. The gear case 38 is coupled to the transmission case right member 37R by a bolt.

  The drive shaft of the V-belt type continuously variable transmission 18 is the crankshaft 27 itself, and the drive pulley 40 of the V-belt type continuously variable transmission 18 is provided at the left extension of the crankshaft 27. The driven shaft 41 of the V-belt type continuously variable transmission 18 is pivotally supported by the transmission case left side member 37L, the transmission case right side member 37R, and the gear case 38 via bearings 42A, 42B, and 42C. . A driven pulley 44 is provided on the driven shaft 41 via a centrifugal clutch 43. An endless V-belt 45 is stretched between the driving pulley 40 and the driven pulley 44.

  When the rotational speed of the crankshaft 27 increases, in the drive pulley 40, the weight roller 40C between the movable half 40B and the ramp plate 40D moves outward by centrifugal force, and the movable half 40B is pushed. The interval between the fixed half 40A and the movable half 40B of the drive pulley 40 is narrowed, and the winding diameter of the V belt 45 is increased. As a result, the tension of the V-belt 45 increases, so that on the driven pulley 44 side, the movable half 44B moves against the biasing force of the coil spring 44D, and the interval between the fixed half 44A and the movable half 44B increases. As a result, the rotational speed of the driven pulley 44 increases according to the dimensional ratio of the winding diameter of the V belt 45. When the driven pulley 44 rotates beyond a predetermined rotational speed, the rotation is transmitted to the clutch inner 43B of the centrifugal clutch 43 through the rotating sleeve 44C, the clutch inner 43B comes into contact with the clutch outer 43A, and the centrifugal clutch 43 enters the connected state. The driven shaft 41 is driven to rotate.

  In the gear reducer 19, the input shaft is the driven shaft 41. The rear axle 9 integrally coupled with the rear wheel 10 is pivotally supported by the transmission case right member 37R and the gear case 38. An intermediate shaft 46 is pivotally supported by the transmission case right member 37R and the gear case 38 in the middle between the driven shaft 41 and the rear axle 9. The torque of the driven shaft 41 is transmitted to the rear axle 9 via the driven shaft pinion 41a, the intermediate shaft large diameter gear 47, the intermediate shaft 46, the intermediate shaft pinion 46a, and the rear axle large diameter gear 48. The rear axle 9 is greatly decelerated with respect to the driven shaft 41, and the rear wheel 10 coupled to the rear axle 9 is driven to decelerate.

  In the right half of FIG. 3, a cam chain drive sprocket 50 is formed adjacent to the ball bearing 28B of the crankshaft 27, and the cam chain 51 is wound around. The cam chain 51 reaches the cam chain driven sprocket 54 provided on the cam shaft 53 inside the cylinder head 25 and the cylinder head cover 26 via the cam chain chamber 52. A water pump 55 is formed at the end of the cam shaft 53. With the rotation of the crankshaft 27, the cooling water sent out from the discharge port 55a of the water pump 55 flows through the water jacket 56 of the cylinder block 24 and the water jacket 57 of the cylinder head 25 and is sent to the radiator 67. . Next to the cam chain drive sprocket 50, a balancer drive gear 58 is provided.

  An AC generator 60 is provided on the right extension of the crankshaft 27. The alternator stator 61 is fixedly attached to an alternator attachment portion 64 attached to the right crankcase 23R. The AC generator rotor 62 is fixed to the right end of the crankshaft 27 and rotates together with the crankshaft 27. A centrifugal cooling fan 63 is attached to the outer surface of the AC generator rotor 62. This is to draw outside air into the radiator 67 and promote cooling in the radiator 67.

  On the right side of the centrifugal radiator cooling fan 63, a radiator 67 is attached via a radiator holding member 66 attached to the right crankcase 23R. The right side of the radiator 67 is covered with a radiator cover 68 that guides cooling air to the radiator 67. A circular opening 66 a for circulating cooling air is provided in a portion of the radiator holding member 66 between the centrifugal radiator cooling fan 63 and the radiator 67. The diameter of the opening 66a is slightly larger than the outer diameter of the blade group of the radiator cooling fan 63.

  FIG. 4 is a right side view of the power unit 1 in a state where the radiator 67 and the radiator cover 68 are removed. The alternator stator 61, the alternator rotor 62, and the radiator cooling fan 63 are shown by dividing the space at the right end of the crankshaft 27 into three parts. The alternator stator 61 is on the farthest side, the radiator cooling fan 63 is provided on the foremost side, and the alternator rotor 62 is provided in the middle. In the drawing, an opening edge 66b of the opening 66a of the radiator holding member 66 shown in FIG. 3 is indicated by a two-dot chain line. Cooling air sucked into the AC generator 60 accommodation chamber side by the radiator cooling fan 63 is discharged from an upper cooling air exhaust port 97 and a lower cooling air exhaust port (not shown) of the AC generator 60 accommodation chamber.

An oil pan 35 is provided at the lower part of the crankcase 23, and a cylindrical oil supply port 71 connected to the oil pan 35 is erected obliquely rearward for oil supply into the crankcase 23, and an oil supply port cap 72 is provided.
A water pump 55 is provided on the right side of the cylinder head 25 and the cylinder head cover 26. A V-belt type continuously variable transmission 18 and a gear reducer 19 are provided behind the crankshaft 27. A rear wheel mounting seat 15 is provided on the rear axle 9.

  FIG. 5 is a right side view of the power unit 1 with a radiator 67 attached to the right side of the radiator cooling fan 63. The radiator 67 is disposed on the front side of the fuel filler port 71. Above and below the radiator 67, an upper tank 73 and a lower tank 74 for storing water are arranged.

  The upper tank 73 is provided with a cooling water inflow joint 73a, and the lower tank 74 is provided with a cooling water outflow joint 74a. The cooling water flowing in from the cooling water inflow joint 73a flows from the radiator upper tank 73 via the heat radiating core 75 toward the radiator lower tank 74, and is cooled by the outside air flowing from the side to the heat radiating core 75 to be cooled. It flows out from the water outflow joint 74a. The radiator 67 includes a water supply port 76 and a water supply port cap 77 in the upper tank 73.

  Circulation in the internal combustion engine 16 of the cooling water flowing out from the radiator lower tank 74 is performed as follows. First, the cooling water flowing out from the radiator lower tank 74 is sent from the cooling water outflow joint 74a to the temperature detection type switching valve 79 through the radiator outflow hose 78. During normal operation of the internal combustion engine 16, the cooling water is sucked into the water pump 55 from the temperature detection type switching valve 79 through the water pump suction cylinder 80, and from the discharge port 55 a of the water pump 55 through the discharge hose 81. It is sent to the water jacket 56 (FIG. 3) of the cylinder block 24. The water jacket 56 of the cylinder block communicates with the water jacket 57 (FIG. 3) of the cylinder head 25. The cooling water that has flowed through these water jackets 56 and 57 and cooled the cylinder block 24 and the cylinder head 25 becomes hot, and the radiator inflow hose 86 and the cooling water are cooled from the branch connection pipe 85 provided on the upper right side of the cylinder head 25. It returns to the radiator upper tank 73 through the water inflow joint 73a. The above cooling water circulation path is during normal operation of the internal combustion engine 16.

  During the warm-up operation when the internal combustion engine 16 is not sufficiently warmed up, the temperature detection type switching valve 79 closes the valve of the water path that flows from the radiator lower tank 74 via the radiator outlet hose 78, and connects the bypass hose 87 from the branch connection pipe 85. Open the valve of the water path that flows in. Thereby, the cooling water is sent to the water jackets 56 and 57 without passing through the radiator and circulated. When the cooling water temperature rises, the temperature detection type switching valve 79 closes the water path from the bypass hose 87, opens the water path flowing in from the radiator lower tank 74, and performs the cooling water circulation during the normal operation described above.

  FIG. 6 is a right side view of the power unit 1 with a radiator cover 68 attached to the right side of the radiator 67. The louver 69 formed on the radiator cover 68 is composed of a plurality of blade plates 69a, and the plurality of blade plates 69a are provided in parallel in a forwardly inclined shape. A water supply port protection part 68 a is provided at the upper part of the radiator cover 68, and a lower tank protection part 68 b is provided at the lower part of the radiator cover 68.

  7 is an external view of the radiator cooling fan 63, FIG. 8 is a sectional view taken along the line VIII-VIII in FIG. 7, FIG. 9 is an exploded view of the blade section as seen from the center of the impeller 88, and FIG. 7 is an external perspective view of an impeller 88. FIG. The fan 63 is a fan in which a large number of forward-facing blades 91 are erected on the outer peripheral portion of the approximately conical blade erection surface 88a. The height of the impeller 88 from the mounting reference surface 88b is not uniform, and three types of blades are arranged in a predetermined order. This is to reduce the blade resonance noise corresponding to a predetermined internal combustion engine speed corresponding to the blade height. A fan in which a large number of forward blades 91 are erected can send a large amount of air at low speed.

  In the following description, in the text and the drawings, the highest blade is denoted by T (Tall), the lowest blade is denoted by S (Short), and the blade having the intermediate height between the blade T and the blade S described above. Are distinguished by attaching a symbol M (Middle). In FIG. 7, there are 18 blades, 12 of which are blades T. There are 6 pairs of high blades T adjacent to each other, and these 6 pairs are equally arranged, leaving room for one blade between them. The arrow W in the figure is the direction of rotation of the impeller. Since the two high blades T form a set, the high blade on the front side in the rotational direction is represented by Ta, and the high blade on the rear side in the rotational direction is represented by Tb. The centers of each pair of blades Ta and Tb of the six pairs of high blades Ta and Tb are arranged at equal intervals L (FIG. 9).

  Three of the six blades Ta and Tb are connected to the blade Tb on the impeller center side of the blade Tb on the rear side in the rotation direction W of the two blades Ta and Tb constituting the set. A mounting boss 93 is provided. The mounting boss 93 is provided with a bolt insertion hole 93a for mounting the impeller 88 to the AC generator rotor 62 (FIG. 3). Coil cooling air holes 94 for the AC generator stator 61 are provided on both sides of the mounting boss 93. The hole 94 communicates with a hole provided at a corresponding position of the AC generator rotor 62, and circulates air around the coil of the AC generator stator 61 to cool the coil.

  A low blade S is erected in a room where a blade on the rear side in the rotation direction W of the blade Tb connected to the mounting boss 93 enters. In the room where the remaining blades enter, the blades M having an intermediate height are erected. As described above, 18 blades are erected uniformly. In FIG. 7, the blades M and S are distinguished from each other with different hatchings. 9 and 11 are also given the same hatching so that they can be distinguished.

  In the blade group, since the pair of blades Ta and Tb are the highest blades, the most radial cooling air can be carried. The cooling air flowing out from the low blades M or S is guided by the cooling air in the radial direction, and the cooling air can be efficiently sent out even at a low rotation.

  Noise can be efficiently reduced by causing the cooling air flowing out from the front and rear low blades M and S to act on the cooling air in the radial direction flowing out from the pair of blades Ta and Tb.

  A low blade S is disposed on the rear side of the mounting boss 93 in the rotation direction W. The height of the mounting boss 93 is secured to secure the mounting strength to the mating member, and the air volume cannot be expected from the blade S on the rear side in the rotation direction W of the mounting boss 93. The height of the blades S on the side is reduced to contribute to noise reduction. Moreover, since the blade | wing S of the back side of the rotation direction W is low, the increase in resistance has decreased.

  Mounting bosses 93 are provided on three of the six high blades Ta and Tb of the blade group. The mounting boss 93 is stabilized at three locations, and noise is prevented by improving the air volume by the flow in the radial direction by the three pairs of high blades Ta and Tb having no mounting boss 93.

  The shape of the edge 90 a on the radiator side of the blade 90 is orthogonal to the rotation axis, that is, parallel to the surface of the heat dissipation core 75 of the radiator 67. As a result, the tip of the blade 90 can be brought close to the heat radiating core 75 (FIG. 3), so that the power unit 1 can be reduced in size and noise can be prevented and air volume can be secured.

  FIG. 11 is an external view of the radiator cooling fan 63 according to another embodiment of the impeller 95. An impeller 95 of the cooling fan 63 is provided with an S-shaped flat blade 96 as a whole by adding a rear blade 92 to the outer peripheral side of the forward blade 91 of the above-described embodiment. Resonance noise at high rotation can be reduced by the rearward-facing blade 92 on the outer periphery while securing the air volume at low rotation by the inner front-facing blade 91.

As described in detail above, the following effects are brought about in the embodiment.
(1) In the impeller 88 having a blade shape with a radially outwardly forward blade shape, it is possible to reduce blade resonance noise corresponding to a predetermined rotational speed of the internal combustion engine 16 corresponding to the height of the blade 90.
(2) Since the cooling air between the pair of high blades Ta and Tb is radiated at a predetermined interval and eventually at an equal interval, while maintaining the rotation balance of the fan, Since the cooling air flowing out from the other blades M and S is guided, the cooling air can be efficiently sent out even at a low rotation.
(3) The highest pair of blades Ta and Tb can carry the largest amount of cooling air in the radial direction, and the guiding effect of the cooling air in the radial direction is increased, so that the cooling air can be efficiently sent out as a whole. Can do.
(4) The cooling air flowing out from the blades M and S at different heights on the front and rear can be applied to the cooling air in the radial direction flowing out from the pair of blades Ta and Tb, so that noise can be reduced efficiently.
(5) Since the air volume cannot be expected on the rear side of the mounting boss 93 in the rotational direction W, a lower blade S is provided on the rear side in the rotational direction W, thereby contributing to noise reduction.
(6) Since the blades S on the rear side in the rotational direction W of the pair of blades Ta and Tb are low in height, the increase in resistance is small, so the cooling air on the rear side in the rotational direction W is reduced by the boss. Can be supplemented.
(7) In the blades 96 of the impeller 95 (FIG. 11), while keeping the air volume at low rotation by the forward blades 91 on the side close to the rotation center, the resonance sound at high rotation is generated by the rear blades 92 on the outer peripheral side. Can be reduced.
(8) The power unit 1 can be miniaturized by installing the blade 90 close to the heat dissipation core 75. Moreover, noise prevention and air volume can be ensured.
(9) Three mounting bosses 93 are provided to stabilize the mounting, and a flow in the radial direction is ensured by a pair of high blades Ta and Tb that are not provided with the mounting boss 93 to improve the air volume and prevent noise. Can do.
(10) Since the edge of the blade 90 on the radiator 67 side is enlarged so as to be parallel to the plane of the heat radiating core 75, the tip of the blade 90 is brought close to the heat radiating core 75 to reduce the size of the power unit. It is possible to prevent noise and secure air volume.

  27 ... Crankshaft, 63 ... Centrifugal radiator cooling fan, 67 ... Radiator, 88 ... Impeller, 88a ... Blade standing surface, 88b ... Installation reference plane, 88c ... Center of rotation, 90 ... Blade, 90a ... Radiator side edge 91 ... Forward blades, 92 ... Backward blades, 93 ... Mounting bosses, 95 ... Impeller (other embodiments), 96 ... Blades (other embodiments), Ta ... High blades (front side in the rotation direction), Tb ... High blades (rear side in the rotation direction), M ... Medium height blades, S ... Low blades

Claims (9)

In the noise prevention structure of the centrifugal cooling fan (63) attached to the crankshaft (27) of the internal combustion engine and generating cooling air by the impeller according to the changing rotational speed,
A blade group consisting of a plurality of blades (Ta, Tb, M, S) is erected on the blade standing surface (88a) of the impeller (88, 95), and each blade tip from the blade wheel mounting surface (88b). height to is a plurality of types,
A structure for preventing noise from a centrifugal cooling fan , wherein a pair of adjacent blades (Ta, Tb) having the same height are arranged at a plurality of locations at predetermined intervals in the blade group . The noise prevention structure for a centrifugal cooling fan according to claim 1 , wherein the pair of adjacent blades (Ta, Tb) having the same height are the highest blades in the blade group. The blade group includes, in addition to the pair of adjacent blades (Ta, Tb) of the same height, a plurality of blades (M, S) that are lower and different in height, and the pair of blades (Ta, T, The structure for preventing noise from a centrifugal cooling fan according to claim 2 , wherein blades having different heights are arranged before and after Tb). The cooling fan (63) includes a mounting boss (93) at the rotation center side end of the blade on the blade standing surface (88a), and a low blade (S) is provided on the rear side in the rotation direction of the boss (93). The noise prevention structure of the centrifugal cooling fan according to claim 3 , wherein the structure is disposed. The cooling fan (63) includes a mounting boss (93) at the blade rotation center side end of the blade standing surface (88a), and the boss (93) is one of the pair of blades (Ta, Tb). The noise prevention structure for a centrifugal cooling fan according to claim 3 , wherein the structure is provided continuously with the blades of the centrifugal cooling fan. The plane shape of each of the blades (96) is curved with a blade shape (91) facing outward in the radial direction on the side close to the center of rotation, and a backward blade shape portion (92) is added to the outer peripheral side. 6. The noise prevention structure for a centrifugal cooling fan according to claim 1 , wherein the structure is S-shaped. The structure for preventing noise from a centrifugal cooling fan according to claim 6 , wherein the cooling fan (63) is provided in the vicinity of the heat radiating core of the radiator (67). 8. The noise prevention structure for a centrifugal cooling fan according to claim 7 , wherein the blade group includes 18 blades and three mounting bosses (93) are provided. Noise prevention structure of the centrifugal cooling fan of claim 7, wherein the shape of the radiator-side edge of the blade (90, 96) is a rotating shaft perpendicular shape.

Images