Centrifugal fan structure

Abstract

To suppress the occurrence of a high-pressure region between an outer peripheral portion of a centrifugal fan and a fan cover member, thereby reducing rotational resistance of the centrifugal fan.SOLUTION: A centrifugal fan (43) includes a plurality of blades (71) circumferentially spaced at a boss portion (61) attached to an end of a rotary shaft (31). Each blade (71) has a blade diameter-enlarging portion (71a) that extends radially outward relative to the base side of the boss portion (61). The fan further includes a first wall portion (82) that connects the outer peripheral edges of the respective blades (71) excluding the blade diameter-enlarging portions (71a) to one another, and a second wall portion (83) that connects the outer peripheral edges of the blade diameter-enlarging portions (71a) of the respective blades (71) to one another. The first wall portion (82) and the second wall portion (83) are connected to each other in a direction of the rotary shaft.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a centrifugal fan structure. [Background technology]

[0002] In recent years, research and development into centrifugal fans has been conducted to contribute to energy efficiency, ensuring that more people have access to affordable, reliable, sustainable and advanced energy. One known technology of this type is a configuration in which a labyrinth structure is provided on one side of the centrifugal fan on the intake side, with a circumferential fan-side rib extending in the axial direction of the drive shaft, to reduce backflow of air (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-110261 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in centrifugal fan technology, a challenge is to further reduce the rotational resistance of the fan. When the airflow around the centrifugal fan was examined, it was found that in the space between the outer periphery of the centrifugal fan and the fan shroud, in an area radially outward from the centrifugal fan and close to the intake port, almost no airflow occurs, and there is a risk of an area of ​​high internal pressure occurring. This high-pressure area increases the rotational resistance of the centrifugal fan. The present invention has been made in view of the above circumstances, and aims to prevent the occurrence of a high-pressure region between the outer periphery of the centrifugal fan and the fan cover, thereby reducing the rotational resistance of the centrifugal fan, and ultimately contributing to improved energy efficiency. [Means for solving the problem]

[0005] The centrifugal fan structure is a centrifugal fan for a forced-air-cooled power unit that is provided at the end of a rotating shaft, takes in air from the rotating shaft direction, and exhausts it radially outward, and the centrifugal fan is covered from the outside of the rotating shaft with a fan cover member.The centrifugal fan has a boss portion attached to the end of the rotating shaft and has a plurality of blades spaced apart in the circumferential direction, and each blade has an expanded blade portion that expands radially outward relatively toward the base of the boss portion, and has a first wall portion that connects the outer peripheral edges of the blades excluding the expanded blade portion, and a second wall portion that connects the outer peripheral edges of the blades at the expanded blade portion, and the first wall portion and the second wall portion are connected in the rotating shaft direction. [Effects of the Invention]

[0006] According to the present invention, it is possible to prevent a high-pressure region from occurring between the outer periphery of the centrifugal fan and the fan covering member, thereby reducing the rotational resistance of the centrifugal fan. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a side view of a saddle-ride type vehicle according to an embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] 3 is a diagram showing a schematic view of a first wall portion and a second wall portion together with the surrounding configuration. FIG. [Figure 5] FIG. 10 is a diagram showing the results of a simulation of the air flow around the blades when the fan is rotating. [Figure 6] 10A and 10B are diagrams showing the flow of air around the first wall portion and the second wall portion. [Figure 7] FIG. 10 is a diagram illustrating a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description, directions such as front, rear, left, right, up and down are the same as directions relative to the vehicle body unless otherwise specified. In addition, in each drawing, the symbol FR indicates the front of the vehicle body, the symbol UP indicates the upper side of the vehicle body, and the symbol LH indicates the left side of the vehicle body.

[0009] [Embodiment Mode] FIG. 1 is a side view of a saddle-ride type vehicle 10 according to an embodiment of the present invention. The saddle-ride type vehicle 10 is a vehicle that includes a body frame 11, a power unit 12 supported by the body frame 11, a front fork 14 that supports a front wheel 13 so as to be steerable, a swing arm 16 that supports a rear wheel 15, and a seat 17 for a passenger. The saddle-ride type vehicle 10 is a vehicle in which a passenger sits astride a seat 17. The seat 17 is provided above the rear part of the body frame 11.

[0010] The body frame 11 includes a head pipe 18 provided at the front end of the body frame 11, a front frame 19 located rearward of the head pipe 18, and a rear frame 20 located rearward of the front frame 19. The front end of the front frame 19 is connected to the head pipe 18. The seat 17 is supported by a rear frame 20 .

[0011] The front forks 14 are supported by a head pipe 18 so as to be steerable to the left and right. The front wheel 13 is supported by an axle 13a provided at the lower end of the front forks 14. A steering handle 21 that is held by the rider is attached to the upper end of the front forks 14.

[0012] The swing arm 16 is supported by a pivot shaft 22 that is supported by the body frame 11. The pivot shaft 22 is a shaft that extends horizontally in the vehicle width direction. The pivot shaft 22 is inserted into the front end of the swing arm 16. The swing arm 16 swings up and down around the pivot shaft 22. The rear wheel 15 is supported by an axle 15 a provided at the rear end of the swing arm 16 .

[0013] The power unit 12 is disposed between the front wheels 13 and the rear wheels 15 and is supported by the body frame 11. The power unit 12 is an internal combustion engine. The power unit 12 includes a crankcase 23 and a cylinder section 24 that houses a reciprocating piston. An exhaust device 25 is connected to an exhaust port of the cylinder section 24. The output of the power unit 12 is transmitted to the rear wheels 15 by a driving force transmission member that connects the power unit 12 and the rear wheels 15 .

[0014] The saddle-ride type vehicle 10 also includes a front fender 26 that covers the front wheel 13 from above, a rear fender 27 that covers the rear wheel 15 from above, a step 28 on which a rider places their feet, and a fuel tank 29 that stores fuel used by the power unit 12. The front fender 26 is attached to the front fork 14. The rear fender 27 and the step 28 are provided below the seat 17. The fuel tank 29 is supported by the body frame 11.

[0015] The saddle-ride type vehicle 10 is a motorcycle. The saddle-ride type vehicle 10 includes a body cover 30 that covers the body, such as the body frame 11. The power unit 12 is a unit swing engine in which the internal combustion engine and the swing arm 16 are integrally provided. The front frame 19 is located in front of the power unit 12. The rear frame 20 is located above the power unit 12. The front frame 19 includes a down frame 19a extending downward from the head pipe 18, and a lower frame 19b extending rearward from a lower portion of the down frame 19a. The rear frame 20 extends rearward and upward from the rear end of the lower frame 19b.

[0016] 2 is a right side view of the power unit 12. FIG. 3 is a cross-sectional view taken along line III-III in FIG. As shown in FIG. 2, the crankcase 23 rotatably supports the crankshaft 31, which extends horizontally in the vehicle width direction (left-right direction). An oil pan 23p is provided below the crankcase 23, functioning as an oil storage section that stores oil that lubricates various parts of the power unit 12. The oil pan 23p is located below the crankshaft 31, and the bottom surface of the oil pan 23p forms the bottom surface of the crankcase 23. The crankcase 23 is disposed in front of the rear wheel 15 and is connected to the rear end of the cylinder section 24. In this description, the direction relative to the vehicle body and the direction relative to the power unit 12 coincide with each other.

[0017] The cylinder section 24 extends forward from the front of the crankcase 23. A cylinder axis 24L of the cylinder section 24 extends forward at an angle close to horizontal. A drive pulley that constitutes part of a V-belt type continuously variable transmission is attached to the left portion of the crankshaft 31. The rotation of the crankshaft 31 is transmitted to the axle 15a of the rear wheel 15 via the V-belt type continuously variable transmission. The V-belt type continuously variable transmission is disposed inside the swing arm 16.

[0018] The right side surface of the crankcase 23 is covered by a fan cover 41. The fan cover 41 is a cover that covers a fan 43 (see FIG. 3) provided at the right end of the crankshaft 31 from the outside in the vehicle width direction, in other words, a cover that covers the crankshaft 31 and its surroundings. The fan cover 41 has an intake port 41a that opens to the outside in the vehicle width direction, and an outer peripheral frame 41g of the intake port 41a. The front edge of the fan cover 41 is connected to the rear edge of the shroud 44, and the space inside the fan cover 41 communicates with the internal space of the shroud 44. The fan cover 41 and the shroud 44 form a fan 43 shroud 45 that forms a space through which air blown by the fan 43 flows to the cylinder portion 24.

[0019] The fan shroud 45 is an example of the "fan covering member" of the present invention. The portion of fan shroud 45 surrounding intake port 41a is also referred to as a grill that forms an outer peripheral frame 41g of intake port 41a.

[0020] 3, a flywheel 50 that rotates integrally with the crankshaft 31 is fixed to the right side of the crankshaft 31. Reference symbol C1 in FIG. 3 indicates the center of the crankshaft 31, which will hereinafter be referred to as the crankshaft center. The flywheel 50 includes a disk portion 50a extending radially outward from the crankshaft 31, and a cylindrical portion 50b extending inward in the vehicle width direction from the outer periphery of the disk portion 50a. A generator 51 that generates electricity by the rotation of the crankshaft 31 is provided inside the flywheel 50. The generator 51 is an ACG (alternating current generator) and constitutes one of the auxiliaries of the power unit 12.

[0021] The fan 43 is provided on the outer side (right side) of the flywheel 50 and the generator 51 in the vehicle width direction. The fan 43 is a centrifugal fan that rotates integrally with the crankshaft 31 to draw in outside air through an intake port 41a (FIG. 2) provided in the fan cover 41 and blow it out in the centrifugal direction of the fan 43. The fan 43 and the generator 51 are provided coaxially with the crankshaft 31 and are rotating bodies that rotate integrally with the crankshaft 31. More specifically, the generator 51 has a rotor that rotates integrally with the crankshaft 31.

[0022] The shroud 44 surrounds the cylinder portion 24 with a gap therebetween, thereby covering approximately the entire circumference of the cylinder portion 24. The space between the shroud 44 and the cylinder portion 24 forms a cylinder cooling air passage that flows the air blown by the fan 43 around the cylinder portion 24. The air that has cooled the cylinder portion 24 is discharged from the gap around the connection port of the exhaust device 25, the gap around the oxygen sensor 24s1, and the like. As a result, the power unit 12 is configured as a forced air-cooling type in which the cylinder portion 24 is forcibly air-cooled by air blown by the fan 43 driven by the crankshaft 31.

[0023] The fan 43 is fastened to a side surface of the flywheel 50 on the outer side in the vehicle width direction. That is, the fan 43 is fixed to the end of the crankshaft 31 in the axial direction via the flywheel 50. The fan 43 rotates integrally with the crankshaft 31, thereby drawing in air from the direction of the rotation axis through the intake port 41a and discharging the air radially outward, which is the centrifugal direction. The fan 43 has a plurality of blades 71 spaced apart circumferentially on a boss portion 61 attached to the end of the crankshaft 31, and also has an annular top blade 81 that connects these blades 71 circumferentially of the fan 43. The crankshaft 31 is an example of the "rotating shaft" of the present invention.

[0024] The boss 61 has a disk-shaped base 62 centered on the rotation axis of the fan 43, and the boss 61 including the base 62 constitutes the base of the fan 43. A plurality of blades 71 are provided on the base 62. Note that in this embodiment, the boss 61, the base 62, and the plurality of blades 71 are integrally formed, but any of them may be formed separately.

[0025] The base portion 62 is formed in a mountain-shaped disk shape that retreats more inward in the vehicle width direction as it moves radially outward relative to the crankshaft center C1, which is the rotation axis of the fan 43. Each blade 71 extends radially outward from the peripheral edge of the boss portion 61 (the base portion 62 in this embodiment), and also extends outward in the vehicle width direction. The blades 71 have gradually longer lengths outward in the vehicle width direction as they move radially outward from the crankshaft center C1.

[0026] Each blade 71 has an expanded diameter blade portion 71a that expands radially outward relatively on the axial base end side (corresponding to the inner side in the vehicle width direction) of the fan 43. In other words, each blade 71 has a reduced diameter blade portion 71b that is positioned radially inward relatively on the tip end side (corresponding to the outer side in the vehicle width direction) of the fan 43. The outer diameter of the base end side of the base portion 62 is smaller than the outer circumference of the blade 71, and the blade expanded diameter portion 71a extends axially to the base end of the base portion 62 (the inner end in the vehicle width direction, corresponding to the base end of the fan 43).

[0027] The top blade 81 includes an annular first wall portion 82 that connects the reduced diameter blade portions 71b of each blade 71 to each other, and an annular second wall portion 83 that connects parts of the expanded diameter blade portions 71a of each blade 71 to each other, and the first wall portion 82 and the second wall portion 83 are connected in the rotational axis direction. The first wall portion 82 and the second wall portion 83 cover half of the outer peripheral surface of the blade 71 from the outer side of the blade 71 and outside in the crankshaft direction. This top blade 81 can improve the strength and rigidity of each blade 71.

[0028] First wall portion 82 is formed in a position and shape that points toward outer peripheral frame 41g of intake port 41a. Here, outer peripheral frame 41g of intake port 41a has cylindrical portion 41t that is recessed outward in the vehicle width direction, and the structure that includes this cylindrical portion 41t increases the strength of outer peripheral frame 41g. The inner peripheral portion of the tubular portion 41t integrally includes a cylindrical frame portion 41w that supports a mesh portion 41m that covers the intake port 41a in a breathable manner, and an inner peripheral protruding rib 41p that protrudes inward in the vehicle width direction from the frame portion 41w. The inner peripheral protruding rib 41p is a circumferential rib that is arranged coaxially with the crankshaft center C1 when viewed in the axial direction of the crankshaft 31. The outer cylindrical portion that constitutes the outer peripheral part of the cylindrical portion 41t extends parallel to the inner cylindrical portion along the vehicle width direction, and integrally has an outer peripheral protruding rib 41q on the outer periphery of the inner peripheral protruding rib 41p that protrudes more inward in the vehicle width direction than the inner peripheral protruding rib 41p.

[0029] The first wall portion 82 is formed in a ring shape oriented toward the opening between the inner peripheral protruding rib 41p and the outer peripheral protruding rib 41q of the cylindrical portion 41t in a side cross-sectional view shown in Figure 3 (corresponding to a cross-sectional view of the fan 43 cut along the rotation axis direction). Therefore, the portion of blade 71 surrounded by first wall portion 82 is formed to have the same outer diameter as intake port 41a provided at a position opposite blade 71. This allows the diameter of the outer peripheral end portion on the intake side of blade 71 to be reduced within a range that allows sufficient air to be drawn in from intake port 41a.

[0030] Furthermore, the first wall portion 82, the inner circumferential protruding rib 41p and the outer circumferential protruding rib 41q allow the path passing between them to be a curved path, thereby preventing foreign matter flowing in from the intake port 41a from moving through this path to the outer circumferential side of the fan.

[0031] 4 is a diagram schematically illustrating the first wall portion 82 and the second wall portion 83 together with the surrounding configuration. In FIG. 4, symbol W1 indicates a portion of the air flow from the intake port 41a, and symbol W2 indicates a portion of the air flow from the fan 43. The first wall portion 82 extends parallel to the axis of the crankshaft 31. Therefore, the first wall portion 82 does not obstruct the intake from the intake port 41a, and can guide the air from the intake port 41a along the crankshaft 31.

[0032] 3, the first wall portion 82 is oriented toward the gap (corresponding to the opening of the cylindrical portion 41t) between the inner peripheral protruding rib 41p and the outer peripheral protruding rib 41q of the cylindrical portion 41t, and does not obstruct communication between the inner peripheral space of the inner peripheral protruding rib 41p and the outer peripheral space of the outer peripheral protruding rib 41q. Therefore, as shown by arrow Wx in FIG. 3, air on the outer peripheral side of the outer peripheral protruding rib 41q can flow toward the inner peripheral side of the inner peripheral protruding rib 41p. Furthermore, since the first wall portion 82 is positioned closer to the intake port 41a, it is possible to prevent the air W1 from the intake port 41a from flowing directly between the first wall portion 82 and the inner peripheral protruding rib 41p, and it is also possible to guide the air from the intake port 41a along the crankshaft 31.

[0033] As shown in Figures 3 and 4, the second wall portion 83 extends radially outward from the vehicle widthwise inner end of the first wall portion 82 along the outer edge of the blade expanded diameter portion 71a, and is formed in a linear shape extending at an acute angle θ1 with respect to the crankshaft center C1. 4, the second wall portion 83 does not obstruct the flow of air W2 from the fan 43 in the centrifugal direction. Furthermore, the inner circumferential surface of the second wall portion 83 can guide a portion of the air W1 from the fan 43 in a direction at an acute angle with respect to the crankshaft 31. In this configuration, the second wall portion 83 guides a portion of the intake air W1 obliquely radially outward, thereby making it possible to guide a portion of the air from the fan 43 into the space X (FIG. 3) between the outer circumferential surface of the second wall portion 83 and the fan shroud 45.

[0034] The air that has flowed into the space X passes through gaps around the first wall portion 82, flows in the direction indicated by the arrow Wx in FIG. 3, and merges with the intake air W1. That is, the second wall portion 83 functions as a guide that guides a portion of the intake air W1 to flow into the space X. In addition, the first wall portion 82 functions as a guide that causes the air that has flowed into the space X to merge with the intake air W1.

[0035] FIG. 5 is a diagram showing the results of a simulation of the air flow around the blades 71 when the fan is rotating. 5, a high-velocity air flow Wa is formed on the inner circumferential side of the fan 43, heading toward the space toward the cylinder portion 24. The first wall portion 82 and the second wall portion 83 are located away from the air flow Wa, and therefore do not interfere with the air flow Wa or function as a guide to smooth the air flow Wx. In addition, a relatively slow air flow Wb is formed that flows radially outward along the outer peripheral surface of the second wall portion 83, and a slow air flow Wx is formed that passes through the gap between the first wall portion 82 and the inner protruding rib 41p of the tubular portion 41t.

[0036] FIG. 6 is a diagram showing the air flow around the first wall portion 82 and the second wall portion 83 based on the simulation results of FIG. 6, the air flows Wb and Wx form a flow Wc that causes air to flow into the space X between the outer peripheral surface of the second wall portion 83 and the fan shroud 45. This flow Wc prevents air from being blocked in the space X and causing pressure in the space X to increase. In addition, this flow Wc makes the air flow Wa from the fan 43 toward the space of the cylinder portion 24 smoother, making it easier to increase the cooling air that cools the cylinder portion 24.

[0037] By preventing the space X from becoming high pressure, the rotational resistance of the fan 43 is reduced. The reduction in the rotational resistance of the fan 43 reduces the energy loss associated with the rotation of the fan 43, thereby reducing the energy consumption of the power unit accordingly. In addition, the responsiveness of the power unit to acceleration requests is improved, which is advantageous for improving the driving performance of the saddle-ride type vehicle 10.

[0038] In the example shown in Figures 4 and 6, the second wall portion 83 is formed in a linear shape extending from the first wall portion 82 at an acute angle θ1 with respect to the crankshaft center C1, but this shape is not limited to this. 7, the second wall portion 83 may have a shape that follows a curve that continues from the first wall portion 82 in a side cross-sectional view of the fan 43. This configuration allows the direction of the air flowing along the first wall portion 82 to be gradually changed, which is advantageous in reducing the rotational resistance of the fan 43. Note that forming the second wall portion 83 in a linear shape has the advantages of making it easier to manufacture the second wall portion 83 and also making it easier to change the angle θa of the second wall portion 83.

[0039] As described above, the centrifugal fan structure of this embodiment includes fan 43 of a forced-air-cooled power unit that is provided at the end of crankshaft 31, which is a rotating shaft. Fan 43 takes in air from the direction of the rotating shaft and exhausts it radially outward, and fan 43 is covered from the outside of crankshaft 31 by fan shroud 45. Fan 43 includes a plurality of blades 71 circumferentially spaced from boss 61 attached to the end of crankshaft 31, and each blade 71 has an expanded-diameter blade portion 71a that expands radially outward relative to the base of boss 61. Fan 43 includes first wall portion 82 that connects the outer circumferential edges of each blade 71 excluding the expanded-diameter blade portions 71a, and second wall portion 83 that connects the outer circumferential edges of each blade 71 at the expanded-diameter blade portions 71a, and the first wall portion 82 and second wall portion 83 are connected in the direction of the rotating shaft.

[0040] 5 and 6 , the intake air is guided radially outward by the inner circumferential surface of the second wall portion 83, and a portion of the guided air flows into the space X between the outer circumferential surface of the second wall portion 83 and the fan shroud 45 and is then discharged from the gap between the outer circumferential surface of the first wall portion 82 and the fan shroud 45. This prevents a high-pressure region from occurring between the outer circumferential portion of the fan and the fan shroud 45, thereby reducing the rotational resistance of the fan 43. Furthermore, the air discharged from the gap between the outer circumferential surface of the first wall portion 82 and the fan shroud 45 can be merged with the intake air, which facilitates an increase in the airflow rate of the fan 43. In this way, the rotational resistance of the fan 43 can be reduced while the airflow rate can be increased, so that the energy consumption of the power unit 12 can be reduced while maintaining sufficient cooling performance, contributing to energy efficiency. In addition, the responsiveness of the power unit 12 to acceleration requests can be improved, which is advantageous for improving the driving performance of the saddle-ride type vehicle 10.

[0041] 3, that is, in a cross-sectional view of fan 43 cut along the direction of the rotational axis, the angle formed between second wall portion 83 and crankshaft 31 is an acute angle. This configuration makes it easier to blow the intake air toward cylinder portion 24, which is the target to be cooled, and also makes it easier to guide a portion of the air to the outer periphery of second wall portion 83 and flow between the outer periphery of the fan and fan shroud 45.

[0042] 7, second wall portion 83 is formed in a shape that follows a curve that continues from first wall portion 82 in a side cross-sectional view of fan 43. This configuration allows the direction of air flowing along first wall portion 82 to be gradually changed, which is advantageous for reducing the rotational resistance of fan 43 and reducing the airflow resistance.

[0043] 3, top blade 81, which is made up of first wall portion 82 and second wall portion 83, covers half of the outer circumferential surface of blade 71 from the outer circumferential side of blade 71 and from the outer side in the crankshaft direction. This configuration can block the cooling air flowing toward fan shroud 45 on the upstream side of fan 43, which is advantageous for reducing the rotational resistance of fan 43 and increasing the amount of air blown. Note that the expression "covering half of the outer circumferential surface of blade 71" does not strictly mean a configuration that covers half of the outer circumferential surface of blade 71, but may also mean a configuration that covers approximately half of the outer circumferential surface of blade 71 (a range before and after half), for example, a configuration that covers a range of one-third to two-thirds.

[0044] Furthermore, the portion of blade 71 surrounded by first wall portion 82 is formed with the same outer diameter as intake port 41a provided at a position opposite blade 71. With this configuration, the diameter of the outer peripheral end portion on the intake side of blade 71 can be reduced within a range that allows sufficient air to be drawn in through intake port 41a, thereby reducing the weight of blade 71. Reducing the weight of blade 71 further reduces the rotational resistance of fan 43, making it easier to further suppress the energy consumption of the power unit and further improve the responsiveness of the power unit to acceleration requests. Note that the phrase "formed with the same outer diameter as intake port 41a" does not strictly mean limited to a configuration in which the blade is formed with the same outer diameter as intake port 41a, but may also mean a configuration in which the blade is formed with an outer diameter approximately the same as intake port 41a (a range around the same outer diameter), for example, a configuration in which the blade is formed with an outer diameter in the range of 1 / 3 to 2 / 3 of the outer diameter of intake port 41a.

[0045] Furthermore, the blade enlarged diameter portion 71a continues to the base end of the fan 43, making it easier to send out a powerful cooling air current. Furthermore, the outer diameter of the base of fan 43 is smaller than the outer periphery of the fan, and the expanded diameter portions of blades 71 extend toward the base end of fan 43. With this configuration, the fan outlet, which corresponds to the downstream end of fan 43, can be widened, making it easier to improve the efficiency of fan 43.

[0046] In this embodiment, the first wall portion 82 connects the outer peripheral edges of the blades 71, excluding the expanded-diameter blade portions 71a, and directs the first wall portion 82 toward the outer peripheral frame 41g of the intake port 41a. This configuration reinforces the blades 71 with the first wall portion 82, while preventing air drawn into the fan 43 from directly flowing between the first wall portion 82 and the outer peripheral frame 41g of the intake port 41a. Furthermore, by allowing air that flows into the outer peripheral sides of the first wall portion 82 and the second wall portion 83 to pass through the gap between the first wall portion 82 and the outer peripheral frame 41g of the intake port 41a, it is possible to effectively prevent a high-pressure region from occurring between the outer periphery of the fan and the fan shroud 45. This reduces the rotational resistance of the fan 43 and allows air passing between the first wall portion 82 and the outer peripheral frame 41g of the intake port 41a to merge with the drawn-in air, thereby increasing the blown air volume. In this way, the rotational resistance of the fan 43 can be reduced while the airflow rate can be increased, so that the energy consumption of the power unit can be reduced while maintaining sufficient cooling performance, contributing to energy efficiency. Also, the responsiveness of the power unit 12 to acceleration requests can be improved, which is advantageous for improving the driving performance of the saddle-ride type vehicle 10.

[0047] Additionally, outer peripheral frame 41g of intake port 41a has a cylindrical portion 41t that is recessed on the side opposite to the intake direction, and first wall portion 82 is oriented toward the opening of cylindrical portion 41t. With this configuration, the diameter of the outer peripheral end portion on the intake side of blade 71 can be reduced within a range larger than the diameter of intake port 41a, allowing sufficient air to be taken in through intake port 41a while reducing the weight of blade 71. Reducing the weight of blade 71 can further reduce the rotational resistance of fan 43, making it easier to further suppress energy consumption of the power unit and further improve the responsiveness of the power unit to acceleration requests.

[0048] Furthermore, the first wall 82 is oriented toward the opening between the inner circumferential protruding rib 41p that constitutes the inner circumferential portion of the cylindrical portion 41t and the outer circumferential protruding rib 41q that constitutes the outer circumferential portion of the cylindrical portion 41t. With this configuration, the first wall 82, the inner circumferential protruding rib 41p, and the outer circumferential protruding rib 41q bend the path that passes between them, making it difficult for foreign matter that has flowed in from the outside to enter.

[0049] Furthermore, since the first wall portion 82 is located on the outer peripheral edge of the blade, the first wall portion 82 does not obstruct the flow of air toward the blade 71, and the air can flow smoothly toward the blade 71. Furthermore, since the second wall portion 83 is also located on the outer peripheral edge of the blade, the second wall portion 83 does not impede the flow of air toward the blade 71, and the air can flow smoothly toward the blade 71.

[0050] In addition, the rotation axis of the centrifugal fan structure is the crankshaft 31, and the first wall portion 82 has a ring shape parallel to the crankshaft 31, so that the air taken in from the direction of the crankshaft 31 can flow smoothly toward the fan 43. Furthermore, since the second wall portion 83 has a ring shape that extends radially outward as it goes toward the inside of the crankshaft 31, the intake air can be guided toward the inside of the crankshaft 31 and radially outward, making it easier to flow toward the object to be cooled, such as the cylinder portion 24.

[0051] [Other embodiments] The above-described embodiment merely shows one aspect of the present invention, and any modifications and applications are possible without departing from the spirit of the present invention.

[0052] For example, the positions, shapes, etc. of the first wall portion 82 and the second wall portion 83 may be changed as appropriate within the scope of preventing the generation of a high-pressure region between the outer periphery of the fan and the fan shroud 45. For example, the first wall portion 82 may have a shape that gradually increases in diameter toward the base end side of the fan 43 in the axial direction. Furthermore, in the above embodiment, the present invention has been described as being applied to the centrifugal fan structure of the saddle-ride type vehicle 10 shown in FIG. 1, but the present invention may also be applied to centrifugal fan structures of any saddle-ride type vehicle, centrifugal fan structures of vehicles other than saddle-ride type vehicles, or centrifugal fan structures used in devices other than vehicles.

[0053] [Configuration supported by the above embodiment] The above embodiment supports the following configurations.

[0054] (Configuration 1) A centrifugal fan of a forced-air-cooled power unit is provided at the end of a rotating shaft, takes in air from the direction of the rotating shaft, and exhausts it radially outward, in a centrifugal fan structure in which the centrifugal fan is covered from the outside of the rotating shaft with a fan cover member, the centrifugal fan has a plurality of blades spaced circumferentially on a boss portion attached to the end of the rotating shaft, each blade has a blade expansion portion that expands radially outward relatively toward the base side of the boss portion, and has a first wall portion that connects the outer peripheral edges of the blades excluding the blade expansion portion, and a second wall portion that connects the outer peripheral edges of the blades at the blade expansion portion, in which the first wall portion and the second wall portion are connected in the direction of the rotating shaft. With this configuration, the intake air is guided radially outward by the inner circumferential surface of the second wall portion, and a portion of the guided air flows into the space between the outer circumferential surface of the second wall portion and the fan cover member and is then discharged through the gap between the outer circumferential surface of the first wall portion and the fan cover member. This prevents a high-pressure region from occurring between the outer circumferential surface of the fan and the fan cover member, reducing the rotational resistance of the centrifugal fan. Furthermore, the air discharged through the gap between the outer circumferential surface of the first wall portion and the fan cover member can be merged with the intake air, making it easier to increase the airflow volume of the centrifugal fan.

[0055] (Configuration 2) The centrifugal fan structure according to Configuration 1, wherein the angle formed between the second wall portion and the rotation shaft is an acute angle in a side cross-sectional view of the centrifugal fan. This configuration makes it easier to blow the intake air toward the object to be cooled, and also makes it easier to guide a portion of the air to the outer periphery of the second wall portion and flow between the outer periphery of the fan and the fan covering member.

[0056] (Configuration 3) The centrifugal fan structure according to configuration 1 or 2, wherein the second wall portion has a shape that follows a curve that continues from the first wall portion in a cross-sectional side view of the centrifugal fan. According to this configuration, the direction of the air flowing along the first wall portion can be changed gradually, which is advantageous for reducing the rotational resistance of the centrifugal fan.

[0057] (Configuration 4) A centrifugal fan structure according to any one of configurations 1 to 3, wherein the first wall portion and the second wall portion cover half of the outer peripheral surface of the blade from the outer peripheral side of the blade and outside in the crankshaft direction. This configuration can block the cooling airflow toward the fan shroud on the upstream side of the fan, which is advantageous in reducing the rotational resistance of the fan, etc. Note that the phrase "covering half of the outer circumferential surface of the blade" does not, in the strict sense, be limited to a configuration in which half of the outer circumferential surface of the blade is covered.

[0058] (Configuration 5) A centrifugal fan structure according to any one of configurations 1 to 4, wherein the portion of the blade surrounded by the first wall portion has the same outer diameter as an intake port provided in a position opposite the blade. With this configuration, the diameter of the outer peripheral end of the blade on the intake side can be reduced within a range that allows sufficient air to be drawn in through the intake port, thereby reducing the weight of the blade. Reducing the weight of the blade further reduces the rotational resistance of the fan, making it easier to reduce the energy consumption of the power unit and improve the responsiveness of the power unit to acceleration requests. Note that the phrase "formed to the same outer diameter as the intake port" does not, in the strict sense, be limited to a configuration in which the blade is formed to the same outer diameter as the intake port.

[0059] (Configuration 6) The centrifugal fan structure according to any one of Configurations 1 to 5, wherein the blade expansion portion continues to a base end of the centrifugal fan. This configuration makes it easier to forcefully send out cooling air.

[0060] (Configuration 7) The centrifugal fan structure according to any one of configurations 1 to 6, wherein the outer diameter of the base of the centrifugal fan is smaller than the outer periphery of the fan, and the expanded diameter portions of the blades extend toward the base ends. According to this configuration, the fan outlet, which corresponds to the downstream end of the centrifugal fan, can be set wide, making it easier to increase the efficiency of the centrifugal fan. [Explanation of symbols]

[0061] 10 Saddle-type vehicle 12 Power unit (internal combustion engine) 23 Crankcase 24 Cylinder section 31 Crankshaft (rotating shaft) 41 Fan cover 41a Air intake 41g outer frame 41t Cylindrical part 41p Inner protruding rib 41q Outer rim protruding rib 43 Fan (Centrifugal Fan) 44 Shroud 45 Fan shroud (fan covering member) 61 Boss section 71 Blade 71a Blade expansion section 81 Top Blade 82 1st wall section 83 Second wall section C1 Crankshaft center (rotation axis center)

Claims

1. A centrifugal fan (43) for a forced air-cooled power unit is provided at an end of a rotating shaft (31), takes in air from the direction of the rotating shaft (31) and exhausts it radially outward, and the centrifugal fan (43) is covered from the outside of the rotating shaft (31) with a fan covering member (45), The centrifugal fan (43) includes a boss portion (61) attached to an end of the rotating shaft (31) and a plurality of blades (71) spaced apart in the circumferential direction, each blade (71) having an expanded-diameter blade portion (71 a) that expands radially outward relatively toward a base side of the boss portion (61), The blade (71) includes a first wall portion (82) that connects the outer peripheral edges of the blades (71) excluding the blade enlarged diameter portion (71a) to each other, and a second wall portion (83) that connects the outer peripheral edges of the blade enlarged diameter portion (71a) to each other, and the first wall portion (82) and the second wall portion (83) are connected in the direction of the rotation axis. Centrifugal fan structure.

2. In a side cross-sectional view of the centrifugal fan (43), the angle formed between the second wall portion (83) and the rotation shaft (31) is an acute angle. The centrifugal fan structure according to claim 1 .

3. The second wall portion (83) has a shape that follows a curve that continues from the first wall portion (82) in a side cross-sectional view of the centrifugal fan (43). The centrifugal fan structure according to claim 1 .

4. The first wall portion (82) and the second wall portion (83) cover half of the outer peripheral surface of the blade (71) from the outer peripheral side of the blade (71) and the outer side in the crankshaft direction. The centrifugal fan structure according to claim 1 .

5. The portion of the blade (71) surrounded by the first wall portion (82) has the same outer diameter as the intake port (41a) provided at a position opposite to the blade (71). The centrifugal fan structure according to claim 1 .

6. The blade enlarged diameter portion (71a) is continuous to the base end of the centrifugal fan (43). The centrifugal fan structure according to claim 1 .

7. The outer diameter of the base of the centrifugal fan (43) is smaller than the outer periphery of the fan, and the blade enlarged diameter portion (71a) extends toward the base end. The centrifugal fan structure according to claim 1 .

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