Water pump impeller structure

Abstract

To provide an impeller structure of a water pump which can increase a discharge quantity while suppressing the formation of cavitation.SOLUTION: In an impeller structure of a water pump having an impeller (70) which can push out a cooling medium by rotating it, the impeller (70) comprises pressing parts (76) for pressing the cooling medium, and the pressing part (76) is formed of: a first pressing part (77) having an angle (θ1) which is acute with respect to a tangent (T1) of a reference circle (C1) with a rotation center point (O) of the impeller (70) as a center; and a second pressing part (79) arranged on a rear side in a rotation direction (R) of the first pressing part (77), and having an angle (θ2) which is larger than that of the first pressing part (77) with respect to the tangent (T1).SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an impeller structure of a water pump. [Background technology]

[0002] Patent Document 1 describes an impeller for a water pump. The impeller in Patent Document 1 includes a base circle portion having a boss portion, a blade base portion extending radially from the base circle portion, a blade plate piece bent at a substantially right angle to the blade base portion and functioning as a portion for pushing cooling water, and a blade cover piece bent at a substantially right angle to the blade plate piece and facing the blade base portion. The blade plate piece described in Patent Document 1 is formed at a constant inclination angle so that the leading edge in the rotation direction is closer to the center of the base circle portion than the trailing edge in the rotation direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-2189 A Summary of the Invention [Problem to be solved by the invention]

[0004] In general, there are problems remaining with impellers in increasing the discharge volume. In the impeller described in Patent Document 1, when trying to increase the discharge volume, it is conceivable to increase the inclination angle of the impeller vanes to make it possible to apply high pressure to the cooling medium. However, in Patent Document 1, since the inclination angle of the impeller vanes is constant, there is a problem that when the inclination angle is increased, the pressure difference of the cooling water around the vanes tends to increase, making cavitation more likely to occur. The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide an impeller structure for a water pump that can increase the discharge volume while suppressing the occurrence of cavitation. [Means for solving the problem]

[0005] A first aspect of the water pump impeller structure is a water pump impeller structure including an impeller capable of pushing out a cooling medium by rotating the impeller, the impeller including a shaft portion and a vane portion provided on an outer circumferential side of the shaft portion, the vane portion including a plate-shaped extension portion extending from the shaft portion and a pressing portion bent toward one end in the axial direction with respect to the extension portion to press the cooling medium, the pressing portion being formed of a first pressing portion having an acute angle with respect to a tangent to a reference circle centered on a rotation center point of the impeller, and a second pressing portion provided rearward of the first pressing portion in the rotation direction and having a larger angle with respect to the tangent than the first pressing portion, the second pressing portion protruding rearward in the rotation direction from the extension portion. 。 Effect of the Invention

[0006] By providing a second pressing portion having a larger angle than the first pressing portion, the pressing force applied to the cooling medium by the pressing portion can be increased, and the discharge volume can be increased while suppressing the occurrence of cavitation compared to when the pressing portion is only the second pressing portion having a larger angle. [Brief description 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. [Diagram 2] FIG. 2 is a side view of the engine according to the present embodiment. [Diagram 3] 4 is a cross-sectional view taken along line IV-IV shown in FIG. 2. [Figure 4] FIG. 2 is a perspective view of the impeller of the present embodiment. [Diagram 5] FIG. 2 is a side view of the impeller of the present embodiment. [Figure 6] 6 is a view showing the axial line of the rotation shaft of the impeller of the present embodiment, corresponding to the view seen in the direction of the arrow VI in FIG. 5. [Figure 7] FIG. 7 is an enlarged view of a main part of FIG. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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, the symbol FR in each drawing 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-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 rider 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 fork 14 is supported by a head pipe 18 so as to be steerable left and right. The front wheel 13 is supported by an axle 13a provided at the lower end of the front fork 14. A steering handle 21 that is held by a rider is attached to the upper end of the front fork 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 about the pivot shaft 22. The rear wheel 15 is supported by an axle 15 a provided at the rear end of a 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 portion 24 that houses a reciprocating piston. An exhaust device 25 is connected to an exhaust port of the cylinder portion 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 his or her 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] 2 is a side view of the engine 12 according to the present embodiment, showing a cross section of the periphery of the water pump 50. The power unit 12 of this embodiment is a parallel two-cylinder, four-stroke, water-cooled engine. The engine 12 as the power unit of this embodiment will be described below. The engine 12 includes a crankcase 23 and a cylinder section 24. The cylinder section 24 includes, in order from the crankcase 23 side, a cylinder 31, a cylinder head 32, and a cylinder head cover 33. The engine 12 is an engine in which the cylinder axis of the cylinder section 24 extends upward and is inclined slightly forward when viewed from the side of the vehicle.

[0016] The crankcase 23 includes an upper crankcase 23A and a lower crankcase 23B that vertically sandwich and support the crankshaft 40. A cylinder 31 extends obliquely upward from the upper crankcase 23A, and the upper crankcase 23A and the cylinder 31 are integrally formed.

[0017] The sides of the crankcase 23 in the vehicle width direction (left and right direction) are covered by a left crankcase cover (not shown) and a right crankcase cover 36. A water pump 50 is provided in front of the right crankcase cover 36. The water pump 50 includes an impeller 70 that rotates to pressurize the cooling water (cooling medium). The impeller 70 has a rotation axis (rotation center line) L1. In the side view shown in FIG. 2, the impeller 70 rotates about a rotation center point O through which the rotation axis L1 passes. The impeller 70 is disposed in a pump chamber 51. The pump chamber 51 includes a delivery chamber 51A in which the impeller 70 is disposed and which expands in a spiral shape, and a suction chamber 51B that communicates with the right side of the delivery chamber 51A (one axial end side of the rotation axis L1). A partition wall 52 that forms the delivery chamber 51A is formed at the front end of the delivery chamber 51A. A discharge passage 53 extending upward is formed in front of the partition wall 52. The discharge passage 53 communicates with the delivery chamber 51A of the pump chamber 51 on the upstream side, and communicates with a water jacket provided in the cylinder 31 on the downstream side.

[0018] A suction connection pipe 54 extending upward and forward is connected to the suction chamber 51B of the pump chamber 51. A radiator outlet hose 56 is connected to the suction connection pipe 54. The radiator outlet hose 56 is connected to a radiator 55 (see FIG. 1). In FIG. 1, the portion where the water pump 50 is disposed is covered with a cover 37.

[0019] A bypass passage hole 57 extending diagonally upward and rearward from the suction chamber 51B of the pump chamber 51 is in communication with the suction chamber 51B rearward of the suction connecting pipe 54. The bypass passage hole 57 is formed in the crankcase cover 36. A bypass communication hose 58 is connected to the bypass passage hole 57. The bypass communication hose 58 is connected to a bypass water jacket (not shown) provided in the cylinder 31.

[0020] In water pump 50, cooling water sucked into suction chamber 51B from suction connection pipe 54 or bypass passage hole 57 is pushed out by impeller 70 into discharge passage 53 and flows from discharge port 53A of discharge passage 53 into a water jacket (not shown) provided in cylinder 31. The water jacket branches downstream into an outflow passage flowing out to radiator 55 and a bypass passage flowing out to bypass communication hose 58, and a thermostat valve (not shown) is provided at the branching point.

[0021] During warm-up operation at the start of the engine 12, the cooling water discharged from the water pump 50 flows into the water jacket from the discharge passage 53, and is then caused to flow through the bypass flow passage, the bypass connecting hose 58, and the bypass passage hole 57 in that order by the thermostatic valve, before returning to the water pump 50.

[0022] In addition, when the temperature of the cooling water rises due to the warm-up operation of the engine 12, the cooling water discharged from the water pump 50 flows from the discharge passage 53 to the water jacket, and then, due to the thermostatic valve, flows in the order of the outflow passage flowing out to the radiator 55 side, the radiator 55, and the radiator outflow hose 56, before returning to the water pump 50. In this manner, the water pump 50 circulates the cooling water through the engine 12, the radiator 55, and the like.

[0023] FIG. 3 is a cross-sectional view taken along line III-III shown in FIG. The crankcase 23 has a crank chamber 23C that houses the crankshaft 40. A speed change chamber (not shown) that houses a speed change mechanism (not shown) is formed behind the crank chamber 23C.

[0024] The crankshaft 40 extends in the vehicle width direction and is rotatably supported by the crankcase 23. A piston (not shown) is connected to the crankshaft 40 via a connecting rod (not shown). The piston is slidably housed in the cylinder portion 24 (see FIG. 2). A rotor (not shown) constituting a generator (not shown) is fixed to the left end (the other axial end) of the crankshaft 40. The rotor is disposed outside the crankcase 23 and is covered by a generator cover (not shown). A drive gear 41 is disposed between the rotor and the crankcase 23. The drive gear 41 is fixed to the crankshaft 40. The drive gear 41 meshes with a driven gear 42. The driven gear 42 is fixed to the left end of a balancer shaft 43.

[0025] The balancer shaft 43 is rotatably supported by the crankcase 23. The balancer shaft 43 has a rotation axis L2. The balancer shaft 43 is disposed parallel to the crankshaft 40. A balancer weight 44 is fitted to the right end (one axial end) of the balancer shaft 43. The balancer weight 44 is disposed outside the crankcase 23. The balancer weight 44 is formed with a relief recess 44A that avoids contact with the water pump 50.

[0026] A water pump 50 is provided on the right end side of the balancer shaft 43. The water pump 50 has a pump case 60. The pump case 60 is composed of the right-side crankcase cover 36 and a pump base case 61 fastened to the inner surface (left surface) of the crankcase cover 36. The pump base case 61 is fastened to the crankcase cover 36 with a plurality of bolts 62. An endless seal member 63 is provided between the pump base case 61 and the crankcase cover 36.

[0027] The pump base case 61 is formed with a cylindrical shaft support portion 61A that protrudes to the left. The shaft support portion 61A rotatably supports a pump shaft 64. The pump shaft 64 is rotatably supported by the shaft support portion 61A via a pair of ball bearings 65, 65 arranged in the axial direction. An annular seal member 66 is provided between the outer peripheral surface of the pump shaft 64 and the inner peripheral surface of the shaft support portion 61A on the right side of the ball bearings 65, 65. In addition, a mechanical seal 67 is provided between the outer peripheral surface of the pump shaft 64 and the inner peripheral surface of the shaft support portion 61A on the right side of the seal member 66. The pump shaft 64 has a rotation axis L1 as a rotation center. The pump shaft 64 is arranged so that the rotation axis L1 is coaxial with the rotation axis L2 of the balancer shaft 43. An impeller 70 is fixed to the right end (one axial end) of the pump shaft 64. The impeller 70 is arranged in the pump chamber 51.

[0028] A convex portion 43A is provided at the right end of the balancer shaft 43. A concave portion 64A is provided at the other end of the pump shaft 64, with which the convex portion 43A of the balancer shaft engages. The convex portion 43A of the balancer shaft 43 engages with the concave portion 64A of the pump shaft 64, causing the pump shaft 64 to rotate integrally with the balancer shaft 43. Note that instead of the configuration of the convex portion 43A and the concave portion 64A of this embodiment, a convex portion may be provided at the other end of the pump shaft 64, and the balancer shaft 43 may be provided with a concave portion that engages with the convex portion of the pump shaft 64.

[0029] The pump chamber 51 and the discharge passage 53 are formed by the groove shapes between the mating surfaces of the crankcase cover 36 and the pump base case 61. In addition, the pump base case 61 is formed with a tubular discharge port 53A that protrudes toward the crankcase 23 side.

[0030] When the engine 12 is driven, the crankshaft 40 rotates, and power from the crankshaft 40 is transmitted to the balancer shaft 43 via the drive gear 41 and the driven gear 42. That is, when the engine 12 is driven, the balancer shaft 43 rotates, and the pump shaft 64 and the impeller 70 rotate integrally with the balancer shaft 43. The rotation of the impeller 70 inside the pump case 60 causes the cooling water to circulate through the cooling path. The water pump 50 of the present embodiment is made up of the pump case 60, the pump shaft 64, the ball bearings 65, the seal member 66, the mechanical seal 67, the impeller 70, and the like.

[0031] Fig. 4 is a perspective view of impeller 70 of the present embodiment. Fig. 5 is a side view of impeller 70 of the present embodiment. Fig. 6 is a view seen in the direction of arrow VI in Fig. 5, and is a view showing the axial line of rotation axis L1 of impeller 70 of the present embodiment. The impeller 70 of the present embodiment is formed from a single metal plate. The impeller 70 is a press-formed product obtained by pressing a single base metal plate. The impeller 70 is a press-formed impeller.

[0032] The impeller 70 has a rotation direction R (see FIG. 6). The impeller 70 is configured to be able to push out the cooling water by rotating in the rotation direction R. The impeller 70 is supported by the pump shaft 64 and rotates integrally with the pump shaft 64. The rotation axis L1 of the impeller 70 corresponds to the rotation axis L1 of the pump shaft 64.

[0033] The impeller 70 includes a circular shaft portion 71 to which the pump shaft 64 is connected, and a plurality of blades 74 provided on the outer periphery of the shaft portion 71 . The shaft portion 71 is shaped to bulge in multiple steps toward one axial end of the rotating shaft L1, and the inner surface side, which is the other axial end of the rotating shaft L1, is recessed in multiple steps. The shaft portion 71 includes a large diameter portion 72 and a small diameter portion 73 that is coaxial with the large diameter portion 72 and has a smaller diameter than the large diameter portion 72. The small diameter portion 73 protrudes toward the one axial end side relative to the large diameter portion 72. The inner diameter of the small diameter portion 73 is formed to be smaller than the outer diameter of the pump shaft 64, and the pump shaft 64 is press-fitted into the small diameter portion 73 (see FIG. 3). The inner diameter of the large diameter portion 72 is also formed to be smaller than the outer diameter of the rotating portion of the mechanical seal 67, and the rotating portion of the mechanical seal 67 is press-fitted into the large diameter portion 72 (see FIG. 3).

[0034] The blade portions 74 are provided at equal intervals in the circumferential direction on the outer circumferential side of the shaft portion 71. The impeller 70 has a rotationally symmetric shape with respect to the center point O of rotation. In particular, in this embodiment, an even number of blade portions 74 are provided. Since there is an even number of blade portions 74 and they are provided at equal intervals, the impeller 70 is point-symmetric with respect to the center point O of rotation. Therefore, for each blade portion 74, there is a paired blade portion 74 on the opposite side of the center point O of rotation. As a result, when the impeller 70 rotates and presses the cooling water, the stress applied to the impeller 70 can be easily uniformed over the entire impeller 70.

[0035] The blade portion 74 includes a plate-shaped extension portion 75 extending from the large diameter portion 72 of the shaft portion 71 in a tangential direction of the large diameter portion 72, and a pressing portion 76 (see FIG. 5) bent toward one end in the axial direction relative to the extension portion 75. The extension portion 75 is a portion that follows the shape of the base metal plate. When viewed from the axial line (see FIG. 6), the extension portion 75 is in the shape of a strip extending tangentially toward the downstream side in the rotation direction R. The extension portion 75 extends from the base end (the other axial end) of the large diameter portion 72 (see FIG. 5). The extension portion 75 includes a rotational front side 75A and a rotational rear side 75B. The rotational front side 75A is formed shorter than the rotational rear side 75B.

[0036] In two extension portions 75 adjacent to each other in rotational direction R, an arc-shaped notch 75C is formed in the base portion of a rotational rear edge 75B of the leading extension portion 75 in rotational direction R and a rotational front edge 75A of the trailing extension portion 75 in rotational direction R. Notch 75C can suppress stress concentration acting on the base of blade portion 74, i.e., the base of extension portion 75, when blade portion 74 presses the cooling water.

[0037] The pressing portion 76 at the tip of the extension portion 75 is a portion obtained by bending a base metal plate at a right angle. The pressing portion 76 is in the shape of a plate along the rotation axis L1. When viewed from the axial line (see FIG. 6), the pressing portion 76 is inclined so that a rotational front end (inlet end) 77A is closer to the rotation axis L1 than a rotational rear end (outlet end) 79B.

[0038] Pressing portion 76 presses the cooling water when impeller 70 rotates. As shown in Fig. 6, pressing portion 76 has a pair of surfaces in the thickness direction, including high-pressure surface 76A that presses the cooling water, and low-pressure surface 76B on the opposite side in the thickness direction to high-pressure surface 76A. High-pressure surface 76A and low-pressure surface 76B each extend from a front end 77A in the rotational direction to a rear end 79B in the rotational direction.

[0039] The pressing portion 76 is formed to be larger in the rotational direction R than the width of the extending portion 75. The pressing portion 76 has a rotational rear end 79B that protrudes rearward in the rotational direction R beyond a rotational rear side 75B of the extending portion 75. As shown in FIG. 5, the pressing portion 76 is formed so that the amount of protrusion in the axial direction of the rotation axis L1 is larger than the large diameter portion 72 of the shaft portion 71 and smaller than the small diameter portion 73 of the shaft portion 71.

[0040] The pressing portion 76 of this embodiment includes a flat first pressing portion 77 connected to the extension portion 75, a curved portion 78 that is curved toward the high pressure surface 76A side with respect to a rotational direction rear end 77B of the first pressing portion 77, and a flat second pressing portion 79 that extends from the rotational direction rear end of the curved portion 78. The first pressing portion 77, the curved portion 78, and the second pressing portion 79 are portions of the base metal plate where the pressing portion 76 is bent. The first pressing portion 77, the curved portion 78, and the second pressing portion 79 are formed by bending the portion of the pressing portion 76. The second pressing portion 79 is formed in a portion of the pressing portion 76 that protrudes rearward in the rotational direction R from the rotational direction rear edge 75B of the extension portion 75.

[0041] When the impeller 70 rotates, in each pressing portion 76, the first pressing portion 76 is located on the upstream side in the relative flow direction of the cooling medium, and the second pressing portion 79 is located on the downstream side. An inclined portion 79C is formed at one axial end of the second pressing portion 79, inclining from the rotational front end 79A to the rotational rear end 79B. The inclined portion 79C is formed axially closer to the one axial end than the large diameter portion 72 of the shaft portion 71 and closer to the other axial end than the tip (one axial end) of the small diameter portion 73 of the shaft portion 71 (see FIG. 5).

[0042] FIG. 7 is an enlarged view of a main portion of FIG. Here, in the axial view of the impeller 70 (see FIG. 6), a first reference circle (reference circle) C1 is assumed to be a virtual circle centered on the rotation center point O of the impeller 70 and passing through the rotation direction front end (inlet end) 77A of the first pressing portion 77. In this embodiment, the first reference circle C1 is assumed to pass through the rotation direction front end 77A of the low pressure surface 76B of the pressing portion 76. In this case, it is possible to assume a first tangent (tangent line) T1 that passes through the rotation direction front end 77A of the pressing portion 76 with respect to the first reference circle C1.

[0043] At this time, the first pressing portion 77 has an acute angle θ1 with respect to the first tangent T1 when viewed from the axial line. Specifically, the first pressing portion 77 is formed such that, in the low pressure surface 76B of the pressing portion 76, the angle θ1 formed by a straight line L77 connecting a rotational direction front end 77A and a rotational direction rear end 77B of the first pressing portion 77 with the first tangent T1 when rotating in the opposite direction to the rotational direction R from the first straight line L77 toward the first tangent T1 is an acute angle. Therefore, when the impeller 70 rotates in the rotational direction R, the first pressing portion 77 can press the cooling water to move it radially outward.

[0044] Further, in the axial view, the second pressing portion 79 has a larger angle θ2 with respect to the first tangent T1 than the first pressing portion 77. Specifically, on the low pressure surface 76B of the pressing portion 76, the second pressing portion 79 is formed such that, among the angles that a second straight line L79 connecting a rotational direction front end 79A and a rotational direction rear end 79B of the second pressing portion 79 makes with the first tangent T1, the angle θ2 when rotating from the second straight line L79 toward the first tangent T1 in the opposite direction to the rotational direction R is larger than the angle θ1 of the first pressing portion 77. Therefore, when the impeller 70 rotates, the cooling water is likely to be pushed by the first pressing portion 77 with a gentle slope, and then by the second pressing portion 79 with a steep slope.

[0045] In particular, in the present embodiment, the angle θ2 between the second pressing portion 79 and the first tangent T1 in the axial view is equal to or smaller than the angle θ3 between the radial straight line (straight line) L78 connecting the curved portion 78 and the rotation center point O, and the first tangent T1. Specifically, in the low pressure surface 76B of the pressing portion 76, the angle between the radial straight line L78, which is a straight line connecting the midpoint of the curved portion 78, i.e., the midpoint P between the rear end 77B in the rotation direction of the first pressing portion 77 and the front end 79A in the rotation direction of the second pressing portion 79, and the rotation center point O, and the first tangent T1 is the angle θ3 when the radial straight line L78 rotates in the opposite direction to the rotation direction R toward the first tangent T1. At this time, the second pressing portion 79 is formed so that the angle θ2 of the second pressing portion 79 is equal to or smaller than the angle θ3.

[0046] In other words, the second straight line L79 of the second pressing portion 79 is parallel to the radial straight line L78, or the angle θ2 does not become larger than that from the state shown in Fig. 7. That is, in the axial view (see Fig. 6), a second reference circle (second reference circle) C2 is assumed to be a virtual circle centered on the rotation center point O of the impeller 70 and passing through the midpoint P, and a second tangent T2 is assumed to pass through the midpoint P on the second reference circle C2. At this time, the second pressing portion 79 is formed so that the angle θ4 formed by the second straight line L79 and the second tangent T2 when rotating from the second straight line L79 toward the second tangent T2 in the opposite direction to the rotation direction R is 90 degrees or less. Therefore, by reducing the angle of the pressing portion 76 having the first pressing portion 77 and the second pressing portion 79, the pressure difference generated by the pressing portion 76 can be reduced, and the occurrence of cavitation can be suppressed.

[0047] Furthermore, the second pressing portions 79 provided at positions symmetrical with respect to the rotation center point O overlap on a radial line L78 (see FIG. 6). Therefore, the stress applied to the impeller 70 can be more easily made uniform.

[0048] Generally, by steeply inclining the pressing portion that presses the cooling water along the radial direction of the impeller, the pressing force on the high-pressure surface side becomes high and the discharge amount becomes large, but in this case, the low-speed flow area tends to expand on the low-pressure surface side of the pressing portion. This increases the pressure difference of the cooling water around the pressing portion, making it easy for cavitation to occur. In contrast, the pressing portion 76 of the present embodiment includes the first pressing portion 77 and the second pressing portion 79, so that pressure is applied to the cooling water in stages, making it easy to reduce the pressure difference, and it becomes easy to increase the discharge amount while suppressing the occurrence of cavitation.

[0049] As described above, according to the embodiment to which the present invention is applied, in the impeller structure of the water pump including the impeller 70 capable of pushing out the cooling water by rotating, the impeller 70 includes a pressing portion 76 that presses the cooling water, and the pressing portion 76 is formed of a first pressing portion 77 having an acute angle θ1 with respect to a first tangent T1 of a first reference circle C1 centered on the rotation center point O of the impeller 70, and a second pressing portion 79 that is provided on the rear side of the first pressing portion 77 in the rotation direction R and has a larger angle θ2 with respect to the first tangent T1 than the first pressing portion 77. Therefore, by providing the second pressing portion 79 with a larger angle than the first pressing portion 77, the pressing force of the pressing portion 76 on the cooling water can be increased, and the discharge amount can be increased while suppressing the occurrence of cavitation, compared to the case in which the pressing portion 76 includes only the second pressing portion 79 with a larger angle.

[0050] In this embodiment, a curved portion 78 whose angle with respect to the first tangent T1 changes is provided between the first pressing portion 77 and the second pressing portion 79, and the angle θ2 formed by the second pressing portion 79 and the first tangent T1 is equal to or smaller than the angle θ3 formed by the first tangent T1 and a radial straight line L78 connecting the curved portion 78 and the rotation center point O. Therefore, by suppressing the angle of the pressing portion 76, the pressure difference generated by the pressing portion 76 can be suppressed, and the occurrence of cavitation can be suppressed.

[0051] In this embodiment, a notch 75C is provided at the base of the extension portion 75 that forms the pressing portion 76. Therefore, stress concentration at the base of the extension portion 75 can be suppressed.

[0052] In the present embodiment, the pressing portion 76 is bent at a right angle to the extending portion 75. Therefore, the extending portion 75, the pressing portion 76, and the like can be formed by pressing a single base metal plate, and the impeller 70 can be formed by press molding.

[0053] Furthermore, in this embodiment, an even number of pressing portions 76 are provided, and the pressing portions 76 are disposed at positions symmetrical with respect to the rotation center point O. Therefore, the stress applied to the impeller 70 can be easily made uniform.

[0054] Furthermore, in this embodiment, the second pressing portions 79 provided at positions symmetrical with respect to the rotation center point O overlap on the straight line L78. Therefore, the stress applied to the impeller 70 can be more easily made uniform.

[0055] [Other embodiments] The above-described embodiment merely shows one aspect of the present invention, and any modification and application can be made without departing from the spirit and scope of the present invention.

[0056] In the above embodiment, an even number of blades 74 are provided. However, an odd number of blades 74 may be provided.

[0057] In the above embodiment, the first reference circle C1, the first straight line L77, the midpoint P, the second straight line L79, etc. are defined on the low pressure surface 76B of the pressing portion 76, but the first reference circle C1, the first straight line L77, the midpoint P, the second straight line L79, etc. may be defined on the high pressure surface 76B of the pressing portion 76. In addition, the first reference circle C1, the first straight line L77, the midpoint P, the second straight line L79, etc. may be defined on the center line of the pressing portion 76 in the thickness direction.

[0058] In the above embodiment, a motorcycle having a front wheel 13 and a rear wheel 15 has been used as an example of saddle-ride vehicle 10, but the present invention is not limited to this, and the present invention can be applied to a three-wheel saddle-ride vehicle having two front or two rear wheels, or a saddle-ride vehicle having four or more wheels.

[0059] [Configuration supported by the above embodiment] The above embodiment supports the following configurations.

[0060] (Configuration 1) A water pump impeller structure having an impeller that can push out a cooling medium by rotating the impeller, the impeller having a pressing portion that presses the cooling medium, the pressing portion being formed of a first pressing portion having an acute angle with respect to a tangent to a reference circle centered on the rotation center point of the impeller, and a second pressing portion that is provided rearward in the rotational direction of the first pressing portion and has a larger angle with respect to the tangent than the first pressing portion. According to this configuration, by providing a second pressing portion having a larger angle than the first pressing portion, the pressing force applied to the cooling medium by the pressing portion can be increased, and the discharge volume can be increased while suppressing the occurrence of cavitation compared to when the pressing portion consists only of the second pressing portion having a larger angle.

[0061] (Configuration 2) A water pump impeller structure according to configuration 1, characterized in that a curved portion is provided between the first pressing portion and the second pressing portion, the angle of which with respect to the tangent line changes, and the angle formed by the second pressing portion and the tangent line is less than or equal to the angle formed by a straight line connecting the curved portion and the rotation center point and the tangent line. According to this configuration, by reducing the angle of the pressing portion, the pressure difference generated by the pressing portion can be reduced, and the occurrence of cavitation can be suppressed.

[0062] (Configuration 3) The water pump impeller structure according to configuration 2, characterized in that a notch is provided at a base of the extension portion forming the pressing portion. According to this configuration, it is possible to suppress stress concentration at the base of the extension portion.

[0063] (Configuration 4) The water pump impeller structure according to configuration 3, wherein the pressing portion is bent at a right angle to the extension portion. According to this configuration, the impeller can be formed by press molding.

[0064] (Configuration 5) The impeller structure of a water pump according to any one of Configurations 2 to 4, characterized in that an even number of the pressing portions are provided, and the pressing portions are arranged at positions symmetrical with respect to the rotation center point. This configuration makes it easier to equalize the stress applied to the impeller.

[0065] (Configuration 6) The water pump impeller structure according to configuration 5, wherein the second pressing portions provided at positions symmetrical with respect to the rotation center point overlap on the straight line. With this configuration, the stress applied to the impeller can be made more uniform. [Explanation of symbols]

[0066] 70 Impeller 75 Stretching section 75C Cutout 76 Pressing part 77 First pressing part 78 Song section 79 Second pressing part C1 First Reference Circle (Reference Circle) T1 1st tangent (tangent) L78 Radial straight line (straight line) O Rotation center point R Rotation direction θ1 angle θ2 angle θ3 angle

Claims

1. In the impeller structure of a water pump, the impeller (70) is provided to rotate and push out a cooling medium, The impeller (70) includes a shaft portion (71) and a blade portion (74) provided on an outer circumferential side of the shaft portion (71), The blade portion (74) includes a plate-shaped extension portion (75) extending from the shaft portion (71), and a pressing portion (76) bent toward one end in the axial direction relative to the extension portion (75) to press the cooling medium, the pressing portion (76) is formed of a first pressing portion (77) having an acute angle (θ1) with respect to a tangent (T1) of a reference circle (C1) centered on the rotation center point (O) of the impeller (70), and a second pressing portion (79) provided rearward of the first pressing portion (77) in the rotation direction (R) and having a larger angle (θ2) with respect to the tangent (T1) than the first pressing portion (77); The water pump impeller structure is characterized in that the second pressing portion (79) protrudes rearward in the rotation direction (R) beyond the extension portion (75).

2. The first pressing portion (77) and the second pressing portion (79) are flat plate-shaped, 2. The water pump impeller structure according to claim 1, wherein a curved portion (78) whose angle with respect to the tangent line (T1) changes is provided between the first pressing portion (77) and the second pressing portion (79).

3. A curved portion (78) whose angle with respect to the tangent line (T1) changes is provided between the first pressing portion (77) and the second pressing portion (79), 3. The water pump impeller structure according to claim 1, wherein an angle (θ2) formed between the second pressing portion (79) and the tangent (T1) is equal to or smaller than an angle (θ3) formed between a straight line (L78) connecting the curved portion (78) and the rotation center point (O) and the tangent (T1).

4. 4. The water pump impeller structure according to claim 3, wherein a notch (75C) is provided at a base of the extension portion (75) that forms the pressing portion (76).

5. 5. The water pump impeller structure according to claim 4, wherein the pressing portion (76) is bent at a right angle to the extending portion (75).

6. 6. The water pump impeller structure according to claim 3, wherein an even number of the pressing portions (76) are provided, and the pressing portions (76) are arranged at positions symmetrical with respect to the rotation center point (O).

7. 7. The water pump impeller structure according to claim 6, wherein the second pressing portions (79) provided at positions symmetrical with respect to the rotation center point (O) overlap on the straight line (L78).

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