Internal combustion engine

Abstract

To provide an internal combustion engine capable of suppressing oil agitation resistance when a bearing equipped with a retainer made of resin is used.SOLUTION: An engine is equipped with right and left crank bearings 50, 60 for supporting a crankshaft 21, and the left and right crank bearings 50, 60 are equipped with retainers 54, 64 made of resin. The retainers 54, 64 have first end face portions which face one sides in the axial direction of the crank bearings 50, 60 as unevenly-shaped portions 55, 65 formed with a plurality of protrusions for supporting a plurality of balls 53, 63, and second end face portions which face the other sides in the axial direction as unevenness suppression portions 56, 66 formed in a plane shape perpendicular to the axial direction. The retainers 54, 64 are disposed in the axial direction so that the unevenness suppression portions 56, 66 are located on the side of a central axis C2 of a cylinder.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an internal combustion engine. [Background technology]

[0002] In recent years, research and development has been conducted into improving fuel efficiency, which contributes to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy. For example, Patent Document 1 discloses a structure in which the ball retainer in a ball bearing is made of synthetic resin. Compared to metal retainers, resin retainers have the advantages of being superior in productivity, flexibility, wear resistance, corrosion resistance, etc., and also being lightweight. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-046069 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the conventional resin retainer is used in an internal combustion engine for a vehicle or the like in the technology for improving fuel economy, the uneven shape of the ball retaining side of the resin retainer tends to scoop up engine oil when used in an oil chamber, which poses the problem that the oil stirring resistance caused by the rotation of the bearing tends to increase.

[0005] Therefore, an object of the present invention is to provide an internal combustion engine that can reduce oil agitation resistance when a bearing with a resin retainer is used, thereby contributing to improved energy efficiency. [Means for solving the problem]

[0006] As a means for solving the above-mentioned problems, a first aspect of the present invention is an internal combustion engine (20) including a crankshaft (21) that converts a reciprocating motion of a piston (25) in a cylinder (23) into a rotational motion, and a crank bearing (50, 60) that supports a journal (21cL, 21cR) of the crankshaft (21), the crank bearing (50, 60) including a resin retainer (54, 64) that supports a plurality of balls (53, 63) between inner and outer rings (51, 52 or 61, 62), the retainer (54, 64) being disposed in an axial direction of the crank bearing (50, 60). a first end surface portion facing one side of the retainer (54, 64) is an uneven portion (55, 65) on which a plurality of protrusions (55c, 65c) supporting the plurality of balls (53, 63) are formed, and a second end surface portion facing the other side in the axial direction is an unevenness suppression portion (56, 66) formed in a plane perpendicular to the axial direction, or formed in an uneven shape with less height difference than the uneven portion (55, 65) when viewed in the radial direction of the crank bearing (50, 60), and the retainer (54, 64) is arranged such that the unevenness suppression portion (56, 66) is located on the side of the central axis (C2) of the cylinder (23) in the axial direction. According to this configuration, in a ball bearing (crank bearing) that supports a crankshaft, the end surface portion located on the central axis side of the cylinder is formed as an unevenness suppression portion formed into a flat shape or the like, thereby achieving the following effects. That is, the outer portion of the crank web of the crankshaft is adjacent to the central axis side of the cylinder in the crank bearing. A large amount of engine oil scooped up by the crank web adheres to the outer portion of the crank web. Since the end surface portion of the retainer has difficulty stirring this engine oil, a structure can be achieved that reduces the oil stirring resistance that occurs when the crank bearing rotates, and as a result, the fuel efficiency of the engine can be improved.

[0007] In a second aspect of the present invention, in the first aspect, the side of the crank bearing (60) facing the central axis (C2) of the cylinder (23) is located upstream of a supply path of engine oil to the crank bearing (60). According to this configuration, in the ball bearing (crank bearing) that supports the crankshaft, the end face located on the upstream side of the engine oil supply path is made into an unevenness suppression portion formed into a flat shape or the like, so that the end face of the retainer is less likely to stir the upstream engine oil present in large amounts on the outer part of the crank web. This makes it possible to achieve a structure that reduces the oil stirring resistance generated when the crank bearing rotates, and as a result, it is possible to improve the fuel efficiency of the engine.

[0008] A third aspect of the present invention is an engine according to the first or second aspect, further comprising a crankcase (22) that rotatably houses the crankshaft (21), and an oil reservoir (35) is formed between a crank web (21bR) of the crankshaft (21) and a bearing support portion (22dR) in the crankcase (22) that supports the crank bearing (60) and the crank bearing (60), and engine oil in the oil reservoir (35) is supplied to the engine through the oil reservoir. An annular oil branch portion (34) facing into the crank web (35) separates the oil into one supplied to the crank pin (21a) of the crankshaft (21) and one supplied to the crank bearing (60). A disk-shaped oil separator (33) with an open inner peripheral side is attached to the crank web (21bR) on the outer circumferential side of the oil branch portion (34), and the inner diameter of the oil separator (33) is larger than the outer diameters of the crank bearing (60) and the oil branch portion (34). According to this configuration, in a structure in which an oil reservoir is formed between the crank web, the bearing support portion, and the crank bearing, and engine oil is divided and supplied to the crank pin and the crank bearing by an oil branch portion in the oil reservoir, the inner diameter of the oil separator is larger than the outer diameter of the crank bearing and the oil branch portion, so that a nested structure can be formed in which the crank bearing and the oil branch portion are inserted into the inner periphery of the oil separator, and the oil reservoir and the oil branch structure can be configured compactly. In addition, the oil separator can filter impurities contained in the engine oil. Therefore, a structure can be formed that reduces the oil agitation resistance generated when the crank bearing rotates, and as a result, the fuel efficiency of the engine can be improved.

[0009] A fourth aspect of the present invention is any one of the first to third aspects, further comprising a crankcase (22) that rotatably houses the crankshaft (21), and an opening (s4) for allowing engine oil to penetrate is formed between a crank web (21bL) of the crankshaft (21) and a bearing support portion (22dL) in the crankcase (22) that supports the crank bearing (50) and the crank bearing (50), and an inner surface (50a) of the crank bearing (50) on the central axis (C2) side of the cylinder (23) is located closer to the central axis (C2) of the cylinder (23) than an inner surface (22dL1) of the bearing support portion (22dL) on the central axis (C2) side of the cylinder (23). According to this configuration, an opening for allowing engine oil to enter is formed between the crank web, the bearing support portion, and the crank bearing, and the inner surface of the crank bearing is closer to the left crank web than the inner surface of the bearing support portion, thereby reducing the oil flow rate between the inner surface of the crank bearing and the outer surface of the crank web. This allows engine oil scooped up around the big end of the connecting rod as the crankshaft rotates to flow back to the oil reservoir through the opening between the crank web, the bearing support portion, and the left crank bearing, while preventing the engine oil in the opening from being supplied too much to the gap between the inner surface of the crank bearing and the outer surface of the crank web. In addition, since the unevenness suppression portion of the crank bearing retainer is located on the cylinder center side, the agitation of engine oil in the gap between the inner surface of the crank bearing and the outer surface of the crank web is also suppressed. As a result, the impact on fuel efficiency caused by an increase in oil agitation resistance is suppressed. Effect of the Invention

[0010] According to the present invention, it is possible to provide an internal combustion engine capable of suppressing oil agitation resistance when a bearing equipped with a resin retainer is employed. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a right side view of the power unit according to the embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along a crank axis and a cylinder axis of the power unit. [Diagram 3] FIG. 3 is an enlarged view of the periphery of a right crank bearing in FIG. 2. [Figure 4] FIG. 3 is an enlarged view of the left crank bearing and its surroundings in FIG. 2. [Diagram 5] 10 is an explanatory diagram showing the retainers of the left and right crank bearings as viewed from a radial direction. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the directions such as front, rear, left and right are the same as the directions in the vehicle described below unless otherwise specified. In addition, in the drawings used in the following description, an arrow FR indicating the front of the vehicle, an arrow LH indicating the left side of the vehicle, and an arrow UP indicating the top of the vehicle are shown at appropriate positions. In the drawings, a line CL indicates the left-right center of the engine 20 of the embodiment.

[0013] <Power unit> FIG. 1 shows the front part of a unit swing type power unit PU used in, for example, a scooter-type motorcycle (saddle-ride type vehicle). An engine (internal combustion engine) 20 serving as a drive source is provided at the front part of the power unit PU. A V-belt type continuously variable transmission (hereinafter simply referred to as transmission) 41 is provided integrally on one of the left and right sides (the left side in this embodiment) of the rear part of the power unit PU. The drive force of the engine 20 is transmitted to the drive wheels (rear wheels) of the motorcycle via the transmission 41 and the like. The power unit PU drives the rear wheels using the engine 20 as the main drive source to run the motorcycle. The power unit PU may include an electric motor as a drive source.

[0014] <Engine> 1 and 2, engine 20 is a single-cylinder engine with crankshaft 21 aligned along the vehicle width direction (left-right direction). Engine 20 includes a crankcase 22 that rotatably supports and houses crankshaft 21, a cylinder 23 that protrudes substantially horizontally (more specifically, slightly upwardly) forward from the front end of crankcase 22 and forms a cylinder hole therein, and a piston 25 that is fitted reciprocally in the cylinder hole and is connected to crank pin 21a of crankshaft 21 via a connecting rod 24.

[0015] In the figure, line C1 indicates the central axis of rotation (crank axis) of the crankshaft 21, and line C2 indicates the central axis of the cylinder bore of the cylinder 23 (cylinder axis, cylinder central axis). The crank axis C1 is parallel to the left-right direction. In this embodiment, the cylinder axis C2 is located at the left-right center CL of the engine 20. In this embodiment, "axially (or left-right) inner side" refers to the side closer to the cylinder axis C2 in the direction along the crank axis C1 (crank axis direction, left-right direction), and "axially (or left-right) outer side" refers to the side farther from the cylinder axis C2 in the crank axis direction.

[0016] The crankcase 22 forms a crank chamber forming portion 22a that accommodates the left and right crank webs 21bL, 21bR and the crank pin 21a of the crankshaft 21. A lower portion of the crank chamber forming portion 22a is formed as an oil reservoir 22b that reserves engine oil. The cylinder 23 includes a cylinder block 23a directly connected to the front end of the crankcase 22, a cylinder head 23b connected to the front end of the cylinder block 23a, and a head cover 23c that covers the front end of the cylinder head 23b. A combustion chamber 23d is formed inside the cylinder 23.

[0017] The piston 25 is capable of sliding within the cylinder 23. The reciprocating motion of the piston 25 is transmitted to the crankshaft 21 via the connecting rod 24. The reciprocating motion of the piston 25 causes the crankshaft 21 to rotate about the crank axis C1. Intake system components are connected to an upper portion of the cylinder head 23b, and exhaust system components are connected to a lower portion of the cylinder head 23b. A valve train VM including a camshaft 27 is configured inside the front part of the cylinder head 23b. The valve train VM controls the intake and exhaust of the combustion chamber 23d by opening and closing valves (not shown). The opening and closing of the valves is controlled by the rotation of the camshaft 27. The camshaft 27 is linked to the crankshaft via a cam chain 30.

[0018] A driven sprocket 28 is attached to the left end of the camshaft 27. A cam drive sprocket 29 is supported on the left side of the crankshaft 21. An endless cam chain 30 is stretched between the driven sprocket 28 and the cam drive sprocket 29. The camshaft 27 rotates in conjunction with the rotation of the crankshaft 21, and opens and closes the intake and exhaust valves according to the intake and exhaust cam patterns. In the figure, the symbol P indicates a spark plug attached to the cylinder head 23b.

[0019] An ACG (AC Generator) 37 is housed in the right side of the crankcase 22 in the left-right direction. The ACG 37 is an outer rotor type rotating electric machine. The ACG 37 includes a stator 38 and an outer rotor 39. The stator 38 is fixed to the crankcase 22. The outer rotor 39 is fixed to the crankshaft 21. The outer rotor 39 has a cylindrical shape that covers the outer periphery of the stator 38. The ACG 37 functions as a generator, and may also function as a starter motor or an assist motor.

[0020] A fan 39a for cooling the ACG 37 and the cylinder 23 is attached to the right side of the outer rotor 39. A fan cover 39b for covering the fan 39a is attached to the right end of the crankcase 22 in the left-right direction. A cooling air intake 39c having a mesh-like grill is formed on the outer side surface of the fan cover 39b in the left-right direction. An air guide cover 39d is connected to the front of the fan cover 39b so as to cover the space to the right of the cylinder 23 of the air-cooled engine 20.

[0021] The space in which the ACG 37 and the fan 39a are disposed is separated from the oil chamber (crank chamber forming portion 22a and oil reservoir portion 22b) in the crankcase 22 by a right side wall 22cR of the crankcase 22. In the drawing, reference symbol 22sR denotes a seal member that provides an oil-tight seal between the crank insertion hole in the right side wall 22cR and the right extension shaft 21dR of the crankshaft 21.

[0022] <Transmission> 2, a transmission case 45 is connected to the left side of the crankcase 22 in the left-right direction. A transmission 41, the driving side of which is connected to the crankshaft 21, is housed inside the transmission case 45. The transmission 41 includes a drive pulley 42 supported on the left side of the crankshaft 21, a driven pulley supported on a driven shaft at the rear of the transmission case 45 (neither shown), and an endless V-belt 44 wound between the drive pulley 42 and the driven pulley.

[0023] The space in which the drive pulley 42 and therefore the transmission 41 are disposed (the space within the transmission case 45) is separated from the oil chamber (the crank chamber forming portion 22a and the oil reservoir portion 22b) in the crankcase 22 by a left side wall 22cL of the crankcase 22 and a left cover 22cL1 attached to the left side of the left side wall 22cL and spaced therefrom. In the drawing, the reference symbol 22sL indicates a seal member that provides an oil-tight seal between the crank insertion hole of the left cover 22cL1 and the left extension shaft 21dL of the crankshaft 21. A cam chain chamber 30a extending toward the cylinder 23 is provided between the left side wall 22cL and the left crank bearing 50.

[0024] The drive pulley 42 includes a drive side fixed pulley half 42a fixed to the crankshaft 21, and a drive side movable pulley half 42b supported on the crankshaft 21 on the left-right inner side (right side) of the drive side fixed pulley half 42a so as to be slidable in the crankshaft direction. A ramp plate 42c fixed to the crankshaft 21 is disposed on the left-right inner side (right side) of the drive side movable pulley half 42b. A weight roller 42d is housed between the drive side movable pulley half 42b and the ramp plate 42c. A belt groove having a V-shaped cross section is formed between the drive side fixed pulley half 42a and the drive side movable pulley half 42b.

[0025] In the drive pulley 42, when the rotation speed of the crankshaft 21 (engine rotation speed) increases, the weight roller 42d moves to the outer periphery of the drive pulley 42 by centrifugal force, and the driving side movable pulley half 42b moves to the driving side fixed pulley half 42a. In response to this movement of the driving side movable pulley half 42b, the width of the belt groove between the driving side fixed pulley half 42a and the driving side movable pulley half 42b decreases, and the winding diameter of the V-belt 44 of the V-belt 44 increases. At this time, in the driven pulley (not shown), the width of the belt groove increases due to the tension of the V-belt 44, and the winding diameter of the V-belt 44 decreases. In this way, the transmission 41 changes the winding diameter of the V-belt 44 continuously according to the rotation speed of the crankshaft 21, automatically and steplessly changing the gear ratio. The rotational driving force of the crankshaft 21 (driving force of the engine 20) is transmitted to the rear wheels, which are the driving wheels, via the transmission 41.

[0026] <Crankshaft> 2, the crankshaft 21 is rotatably supported within the front portion of the crankcase 22 via a pair of left and right ball bearings (rolling bearings, hereinafter referred to as crank bearings) 50, 60. The crankshaft 21 generates rotational motion about the crank axis C1 from the reciprocating motion of the piston 25. The crankshaft 21 is integrally rotatable with a pair of left and right crank webs 21bL, 21bR including a crank arm and a counterweight, a pair of left and right journals 21cL, 21cR protruding outward in the left-right direction along the crank axis C1 from each of the left and right crank webs 21bL, 21bR, and a pair of left and right extension shafts 21dL, 21dR further extending outward in the left-right direction along the crank axis C1 from each of the left and right journals 21cL, 21cR.

[0027] For example, each of the left and right crank webs 21bL, 21bR has a disk shape centered on the crank axis C1. 3, a plate-shaped oil separator 33 is attached to the outer side surface (right side surface) of the right crank web 21bR in the left-right direction. The oil separator 33 is formed in a disk shape with an opening on the inner peripheral side. The oil separator 33 is provided in an annular shape along the outer circumferential side of the right side surface of the right crank web 21bR. An outer circumferential edge portion 33a of the oil separator 33 fits into the outer circumferential side of the right side surface of the right crank web 21bR, and the remaining portion is disposed spaced to the right from the right side surface of the right crank web 21bR. The oil separator 33 rotates integrally with the right crank web 21bR and collects foreign matter in the engine oil in the oil reservoir 35 between the oil separator 33 and the right crank web 21bR on the outer periphery of the oil reservoir 35 by the centrifugal force caused by the rotation of the crankshaft 21, thereby making it possible to prevent the foreign matter from being supplied to sliding contact parts such as the right crank bearing 60, the crank pin 21a, and the big end 24a of the connecting rod 24.

[0028] The left and right journals 21cL, 21cR are rotatably supported by being inserted into left and right crank bearings 50, 60, respectively. The left and right crank bearings 50, 60 are fitted into and held in bearing support portions 22dL, 22dR of the left and right side walls 22cL, 22cR of the crankcase 22.

[0029] A cam drive sprocket 29 and a pump drive gear 31 are supported on the base end side (left journal 21cL side) of the left extension shaft 21dL so as to be rotatable together, in that order from the left journal 21cL side. A cam chain 30 is wound around the cam drive sprocket 29. A driven gear of an oil pump (not shown) meshes with the pump drive gear 31. The pump drive gear 31 may be a sprocket. A drive pulley 42 of a transmission 41 is supported on the tip side of the left extension shaft 21dL so as to be rotatable together. An outer rotor 39 of the ACG 37 is supported on the right extension shaft 21dR so as to be rotatable integrally therewith.

[0030] The left and right crank webs 21bL, 21bR are disposed opposite to each other in the crankshaft direction with a gap therebetween that allows the connecting rod 24 to be inserted therethrough. The left and right crank webs 21bL, 21bR each have a crank arm as a prescribed circumferential position. Both ends of the crank pin 21a are supported on the tip side (position eccentric from the crank axis C1) of the left and right crank arms. A big end 24a of the connecting rod 24 is rotatably fitted onto the crank pin 21a. Left and right journals 21cL, 21cR are integrally provided on the left and right outer sides of the left and right crank webs 21bL, 21bR, respectively.

[0031] <Crank bearing> 2, 3 and 5, each crank bearing 50, 60 includes an outer race 51, 61 and an inner race 52, 62, a plurality of balls (steel balls) 53, 63 sandwiched between the outer race 51, 61 and the inner race 52, 62, and a retainer (holder) 54, 64 for rotatably holding the plurality of balls 53, 63. The retainers 54, 64 in the embodiment are not metal products manufactured by subjecting an iron plate to press molding or the like, but are resin molded products integrally molded from high-strength synthetic resin such as polyacetal. Hereinafter, the axial direction, circumferential direction and radial direction of each crank bearing 50, 60 may be simply referred to as the axial direction, circumferential direction and radial direction, respectively.

[0032] The retainer 54, 64 is annular about the crank axis C1. The retainer 54, 64 has a first end surface portion facing one axial side of the crank bearing 50, 60 as an uneven portion 55, 65 having a plurality of protrusions formed thereon for supporting a plurality of balls 53, 63, and a second end surface portion facing the other axial side as an unevenness suppressing portion 56, 66 formed in a plane perpendicular to the axial direction.

[0033] 5, the uneven portion 55, 65 has a base end surface 55a, 65a that is a specified distance away from the flat surface 56a, 66a of the unevenness suppressing portion 56, 66 on one axial side, and a plurality of pockets 55b, 65b are formed by cutting out the base end surface 55a, 65a at equal intervals in the circumferential direction. Each pocket 55b, 65b is a circular recess having approximately the same diameter as each ball 53, 63, and rotatably accommodates and holds each ball 53, 63. Each pocket 55b, 65b has one axial side cut out and open on the base end surface 55a, 65a, and both radial sides open on the inner and outer circumferential surfaces of the retainer 54, 64, respectively.

[0034] The uneven portion 55, 65 has a plurality of retaining claws 55c, 65c protruding from the base end face 55a, 65a to one side in the axial direction so that the inner peripheral surface of each pocket 55b, 65b extends from the base end face 55a, 65a to one side in the axial direction when viewed from the radial direction of the center of the crank axis C1. Each pocket 55b, 65b can hold more than half the circumference of the outer peripheral surface of each ball 53, 63, but the retaining claws 55c, 65c extend the inner peripheral surface to widen the range in which the outer peripheral surface of each ball 53, 63 is held, and the ball 53, 63 is prevented from falling out of each pocket 55b, 65b. The uneven portion 55, 65 is formed in an uneven shape when viewed from the radial direction of the center of the crank axis C1 by a part of each ball 53, 63 and the retaining claws 55c, 65c protruding from the base end face 55a, 65a.

[0035] The irregularity suppressing portion 56, 66 forms a flat surface 56a, 66a perpendicular to the axial direction on the other axial side of the retainer 54, 64. For example, the flat surface 56a, 66a is formed substantially flush with the flat surfaces 56a, 66a on the other axial sides of the outer races 51, 61 and the inner races 52, 62 (corresponding to the flat surfaces 56a, 66a on the other axial sides of the crank bearings 50, 60). The flat surfaces 56a, 66a may be formed on one axial side (inside the crank bearings 50, 60) of the flat surfaces 56a, 66a on the other axial sides of the outer races 51, 61 and the inner races 52, 62.

[0036] The unevenness suppression portion 56, 66 in the embodiment is formed in a flat shape perpendicular to the axial direction, but is not limited to this configuration. For example, the unevenness suppression portion 56, 66 may have a certain degree of unevenness when viewed from the radial direction. A certain degree of unevenness means a gentle uneven shape with less height difference than the uneven shape portion 55, 65 when viewed from the radial direction (a shape that makes it difficult to stir engine oil). The unevenness suppression portion 56, 66 may have unevenness in a cross section along the radial direction, but in this case, it is sufficient that the uneven shape in the cross section extends continuously in the circumferential direction and is formed in a flat shape or a gentle uneven shape when viewed from the radial direction. In other words, the unevenness suppressing portions 56, 66 may have any shape that makes it more difficult to agitate engine oil than the uneven shape portions 55, 65 when the crank bearings 50, 60 rotate.

[0037] <Crank bearing arrangement> Referring to Figures 3 to 5, the left and right crank bearings of the embodiment are arranged so that the flat surfaces 56a, 66a of each retainer 54, 64 are located on the inner surfaces 50a, 60a (the left side surface in the right crank bearing 60, and the right side surface in the left crank bearing 50) closer to the cylinder axis C2.

[0038] First, the arrangement of the right crank bearing 60 and the surrounding structure will be described. 3, the right side surface (outer surface in the crank axial direction) s1 of the right crank web 21bR forms a displacement surface s2 offset to the left by a specified amount, leaving inner and outer convex shapes t1, t2 on the inner and outer periphery, respectively. In the embodiment, the outermost surface (plane perpendicular to the crank axis C1) on which the right tip ends (projecting ends) of the inner and outer convex shapes t1, t2 are located is defined as the right side surface (outer surface) s1 of the right crank web 21bR. A part of the displacement surface s2 is formed by the right end surface of the crank pin 21a. Note that the displacement surface s2 may be regarded as a part of the right side surface of the right crank web 21bR.

[0039] The outer peripheral edge 33a of the oil separator 33 is fitted to the inner peripheral side of the outer convex shape t2. The oil separator 33 includes a plate-shaped portion 33b extending from the outer peripheral edge 33a to the inner peripheral side. The plate-shaped portion 33b is in the form of a flat plate perpendicular to the crank axis C1, and is disposed with a gap between it and the displacement surface s2. The plate-shaped portion 33b is spaced apart from the displacement surface s2 in the axial direction. The inner peripheral end of the plate-shaped portion 33b is disposed close to the outer peripheral side of the annular protrusion 34 that protrudes from the inner surface (left surface) 22dR1 on the cylinder axis C2 side of the right bearing support portion 22dR and forms an annular shape around the crank axis C1. A region R1 is formed between the plate-shaped portion 33b of the oil separator 33 and the displacement surface s2 of the right crank web 21bR. A region R2 is formed between an inner surface (surface on the cylinder axis C2 side, left surface) 60a of the right crank bearing 60 and the displacement surface s2 of the right crank web 21bR on the inner peripheral side of the annular protrusion 34. These regions R1, R2 form an oil reservoir 35 that is in communication with each other. Engine oil is supplied to the oil reservoir 35 from an oil supply port (not shown) that opens to the inner surface 22dR1 of the right bearing support portion 22dR.

[0040] An in-pin oil passage 21a1 is formed in the crank pin 21a along the axis of the crank pin 21a. The right end of the in-pin oil passage 21a1 opens to the right side at the right end surface of the crank pin 21a and faces the oil reservoir 35. The engine oil in the oil reservoir 35 flows into the in-pin oil passage 21a1 of the crank pin 21a and is supplied to the sliding contact portion between the crank pin 21a and the big end 24a of the connecting rod 24 through a radial oil passage 21a2 that is partially formed in the circumferential direction of the crank pin 21a and extends in the radial direction. This engine oil is further supplied to the sliding contact portion between the small end 24b of the connecting rod 24 and the piston pin 25a through an oil passage (not shown) formed in the connecting rod 24.

[0041] A part of the engine oil in the oil reservoir 35 flows into the region R2 on the right crank bearing 60 side, with the annular protrusion (oil branch portion) 34 as the boundary, and is supplied to the right crank bearing 60. The engine oil supplied to the right crank bearing 60 is used for lubrication of the right crank bearing 60, and then flows down to the bottom of the crankcase 22 and is returned to the oil reservoir 22b. A flat portion (unevenness suppressing portion 66) of the resin retainer 64 faces the axially inner surface (left surface) of the right crank bearing 60, suppressing resistance caused by stirring the engine oil in the oil reservoir 35 when the retainer 64 rotates. As a result, the impact on fuel economy caused by increased oil stirring resistance is suppressed.

[0042] As described above, the engine 20 in the above embodiment includes the crankshaft 21 that converts the reciprocating motion of the piston 25 in the cylinder 23 into rotational motion, and the left and right ball bearings (crank bearings) 50, 60 that support the left and right journals 21cL, 21cR of the crankshaft 21, respectively. The left and right crank bearings 50, 60 each include a resin retainer 54, 64 that supports a plurality of balls 53, 63 between the inner and outer races (outer races 51, 61 and inner races 52, 62), The retainers 54, 64 have a first end surface portion facing one axial side of the right crank bearing 50, 60 as an uneven portion 55, 65 on which a plurality of protrusions (retaining claws 55c, 65c) that support the plurality of balls 53, 63 are formed, and a second end surface portion facing the other axial side as an unevenness suppression portion 56, 66 formed in a plane perpendicular to the axial direction, and the retainers 54, 64 of the left and right crank bearings 50, 60 are arranged in the axial direction so that the unevenness suppression portion 56, 66 is located on the side of the central axis C2 of the cylinder 23. According to this configuration, the end surface portion located on the central axis C2 side of the cylinder 23 in the left and right ball bearings (crank bearings) 50, 60 supporting the crankshaft 21 is formed as the unevenness suppression portion 56, 66 formed in a flat shape or the like, thereby achieving the following effects. That is, the outer parts of the left and right crank webs 21bL, 21bR of the crankshaft 21 are adjacent to the central axis C2 side of the cylinder 23 in the left and right crank bearings 50, 60. A large amount of engine oil scooped up by the left and right crank webs 21bL, 21bR adheres to the outer parts of the left and right crank webs 21bL, 21bR. In particular, an oil reservoir 35 is formed at least on the outer part of the right crank web 21bR. Since the end surface portion of the retainer 54, 64 is less likely to stir this engine oil, a structure can be formed that reduces the oil stirring resistance generated when the left and right crank bearings 50, 60 rotate, and as a result, the fuel efficiency of the engine 20 can be improved.

[0043] In the above-mentioned engine 20, at least the central axis C2 side of the cylinder 23 in the right crank bearing 60 is located upstream of a supply path of engine oil to the right crank bearing 60. According to this configuration, in the right ball bearing (crank bearing) 60 supporting the crankshaft 21, the end surface portion located on the upstream side of the engine oil supply path is formed as the unevenness suppression portion 66 having a flat shape or the like, so that the end surface portion of the retainer 64 is less likely to stir the upstream engine oil present in large amounts on the outer portion of the right crank web 21bR. This makes it possible to achieve a structure that reduces the oil stirring resistance generated when the right crank bearing 60 rotates, and as a result, the fuel efficiency of the engine 20 can be improved.

[0044] The engine 20 includes a crankcase 22 that rotatably houses the crankshaft 21, and an oil reservoir 35 is formed between at least a right crank web 21bR of the crankshaft 21 and a right bearing support portion 22dR that supports the right crank bearing 60 in the crankcase 22 and the right crank bearing 60. Engine oil in the oil reservoir 35 is separated into a portion to be supplied to the crank pin 21a of the crankshaft 21 and a portion to be supplied to the right crank bearing 60 by an annular oil branch portion (annular protrusion 34) facing into the oil reservoir 35. A disk-shaped oil separator 33 that is open on its inner peripheral side is attached to the right crank web 21bR on the outer circumferential side of the oil branch portion 34, and the inner diameter of the oil separator 33 is larger than the outer diameters of the right crank bearing 60 and the oil branch portion 34. According to this configuration, an oil reservoir 35 is formed between the right crank web 21bR, the right bearing support portion 22dR, and the right crank bearing 60, and engine oil is divided and supplied to the crank pin 21a and the right crank bearing 60 by an oil branching portion 34 within the oil reservoir 35. Since the inner diameter of the oil separator 33 is larger than the outer diameter of the right crank bearing 60 and the oil branching portion 34, a nested structure can be formed in which the right crank bearing 60 and the oil branching portion 34 are inserted into the inner periphery of the oil separator 33, and the oil reservoir 35 and oil branching structure can be configured compactly.

[0045] Here, the axially inner side surfaces 50a, 60a of the left and right crank bearings 50, 60 are positioned to protrude a predetermined amount toward the central axis C2 of the cylinder 23 relative to the axially inner side surfaces 22dL1, 22dR1 of the left and right bearing support portions 22dL, 22dR of the crankcase 22. As a result, the axially inner side surfaces 50a, 60a of the left and right crank bearings 50, 60 are disposed closer to the left and right crank webs 21bL or 21bR on the same side than the axially inner side surfaces 22dL1, 22dR1 of the left and right bearing support portions 22dL, 22dR. In other words, the axially inner parts of the left and right crank bearings 50, 60 protrude axially inward from the axially inner side surfaces 22dL1, 22dR1 of the left and right bearing support portions 22dL, 22dR. Further, the axially inner side surfaces 22dL1, 22dR1 of the left and right bearing support portions 22dL, 22dR are disposed so as to be farther away from the left and right crank webs 21bL or 21bR on the same side than the axially inner side surfaces 50a, 60a of the left and right crank bearings 50, 60.

[0046] Next, the arrangement of the left crank bearing 50 and the surrounding structure will be described. 4, a gap between the axially inner side surface 22dL1 of the left bearing support portion 22dL and the axially outer side surface s3 of the left crank web 21bL serves as an opening s4 for supplying engine oil to the left crank bearing 50. A part of the engine oil that has infiltrated into the opening s4 from above the left crank web 21bL infiltrates into a gap s5 between the inner side surface 50a of the left crank bearing 50 and the outer side surface s3 of the left crank web 21bL, and is supplied to the left crank bearing 50. The gap s5 has a narrower axial width than the opening s4. After being used for lubricating the left crank bearing 50, the engine oil that has been supplied to the left crank bearing 50 flows down to the bottom of the crankcase 22 and is returned to the oil reservoir 22b. The flat portion (unevenness suppressing portion 56) of the resin retainer 54 faces the axially inner surface 50a (right surface) of the left crank bearing 50, suppressing resistance caused by stirring the engine oil in the gap s5 when the retainer 54 rotates. As a result, the impact on fuel economy caused by increased oil stirring resistance is suppressed.

[0047] In this way, in the engine 20, an opening s4 for allowing engine oil to penetrate is formed between the left crank web 21bL of the crankshaft 21 and the left bearing support portion 22dL that supports the left crank bearing 50 in the crankcase 22 and the left crank bearing 50, and the inner surface 50a on the cylinder axis C2 side of the left crank bearing 50 is located closer to the cylinder axis C2 than the inner surface 22dL1 on the cylinder axis C2 side of the left bearing support portion 22dL. According to this configuration, an opening s4 through which engine oil can enter is formed between the left crank web 21bL and the left bearing support portion 22dL and the left crank bearing 50, and the inner surface 50a of the left crank bearing 50 is closer to the left crank web 21bL than the inner surface 22dL1 of the left bearing support portion 22dL, thereby narrowing the gap s5 between the inner surface 50a of the left crank bearing 50 and the outer surface s3 of the left crank web 21bL and reducing the oil flow rate. This allows engine oil scooped up around the big end 24a of the connecting rod 24 as the crankshaft 21 rotates to flow back to the oil reservoir 22b through the opening s4 between the left crank web 21bL and the left bearing support portion 22dL and the left crank bearing 50, while preventing too much engine oil from being supplied to the gap s5 between the inner surface 50a of the left crank bearing 50 and the outer surface s3 of the left crank web 21bL. In addition, since the unevenness suppression portion 56 of the retainer 54 of the left crank bearing 50 is located on the central axis C2 side of the cylinder 23, agitation of engine oil in the gap s5 between the inner surface 50a of the left crank bearing 50 and the outer surface s3 of the left crank web 21bL is also suppressed. As a result, the impact on fuel economy due to an increase in oil agitation resistance is suppressed.

[0048] The present invention is not limited to the above embodiment, and for example, the internal combustion engine of the present embodiment may be applied to vehicles other than saddle-type vehicles such as motorcycles. Furthermore, the application is not limited to vehicles, and may be applied to various vehicles and moving bodies such as various transport equipment such as aircraft and ships, construction machinery, industrial machinery, etc. Furthermore, the present invention may be widely applied to equipment other than vehicles that has an internal combustion engine, such as hand-pushed lawnmowers, cleaning machines, generators, etc. The configurations in the above-described embodiments are merely examples of the present invention, and various modifications are possible without departing from the gist of the present invention, such as replacing the components of the embodiments with well-known components. [Explanation of symbols]

[0049] 20 Engine (internal combustion engine) 21 Crankshaft 21a Crank pin 21bL, 21bR Left and right crank webs 21cL, 21cR Left and right journals 22 Crankcase 22dL, 22dR Left and right bearing support parts 22dL1,22dR1 Axial inner surface 23 Cylinder 25 Piston 35 Oil Sump 29 Cam drive sprocket (power transmission component) 30 Cam chain 33 Oil separator 34 Annular protrusion (oil branching part) 50,60 Left and right crank bearings 50a, 60a Axial inner surface 51,61 Outer race 52,62 Inner race 53,63 Ball 54,64 Retainer 55,65 Uneven shape part 55c,65c Holding claw (protrusion) 56,66 Unevenness suppression part C1 Crank axis C2 Cylinder axis (center axis) PU Power Unit s4 opening VM valve train

Claims

1. A crankshaft (21) that converts the reciprocating motion of a piston (25) in a cylinder (23) into a rotational motion; Crank bearings (50, 60) supporting journals (21cL, 21cR) of the crankshaft (21); In an internal combustion engine (20) comprising: The crank bearing (50, 60) includes a resin retainer (54, 64) that supports a plurality of balls (53, 63) between inner and outer rings (51, 52 or 61, 62), The retainer (54, 64) is a first end surface portion of the crank bearing (50, 60) facing one side in the axial direction is formed as an uneven portion (55, 65) on which a plurality of protrusions (55c, 65c) supporting the plurality of balls (53, 63) are formed; a second end surface portion facing the other side in the axial direction is an unevenness suppression portion (56, 66) formed in a flat shape perpendicular to the axial direction, or formed in an uneven shape having a smaller height difference than the uneven shape portion (55, 65) when viewed in the radial direction of the crank bearing (50, 60); a side of the crank bearing (60) toward a center axis (C2) of the cylinder (23) in the axial direction is an upstream side of a supply path of engine oil to the crank bearing (60), The retainer (54, 64) is disposed such that the irregularity suppression portion (56, 66) is located on the central axis (C2) side of the cylinder (23) in the axial direction. An internal combustion engine characterized by:

2. The crank bearings (50, 60) are provided in a pair in the axial direction, The internal combustion engine according to claim 1, characterized in that the unevenness suppression portions (56, 66) of the retainers (54, 64) of the pair of crank bearings (50, 60) are both located on the central axis (C2) side of the cylinder (23) in the axial direction.

3. A crankcase (22) that rotatably houses the crankshaft (21), an oil reservoir (35) is formed between a crank web (21bR) of the crankshaft (21) and a bearing support portion (22dR) supporting the crank bearing (50, 60) in the crankcase (22) and the crank bearing (50, 60); The engine oil in the oil reservoir (35) is divided by an annular oil branch portion (34) facing into the oil reservoir (35) into a portion to be supplied to the crank pin (21 a) of the crankshaft (21) and a portion to be supplied to the crank bearings (50, 60), A disk-shaped oil separator (33) having an opening on its inner peripheral side is attached to the crank web (21bR) on the outer peripheral side of the oil branch portion (34), The inner diameter of the oil separator (33) is larger than the outer diameters of the crank bearings (50, 60) and the oil branch portion (34).

3. An internal combustion engine according to claim 1 or 2.

4. A crankcase (22) that rotatably houses the crankshaft (21), an opening (s4) for allowing engine oil to enter is formed between a crank web (21bL) of the crankshaft (21) and a bearing support portion (22dL) in the crankcase (22) that supports the crank bearing (50, 60) and the crank bearing (50, 60); An inner surface (50a) of the crank bearing (50, 60) on the central axis (C2) side of the cylinder (23) is located closer to the central axis (C2) of the cylinder (23) than an inner surface (22dL1) of the bearing support portion (22dL) on the central axis (C2) side of the cylinder (23).

3. An internal combustion engine according to claim 1 or 2.

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