JP5106018B2 - Support structure for motorcycle crankshaft - Google Patents

Description

  The present invention relates to a crankshaft support structure in a reciprocating engine such as a vehicle.

Conventionally, in the above crankshaft support structure, a ball bearing for inserting a journal of the crankshaft with a cast iron bush integrally cast in an aluminum alloy crankcase and a steel bush press-fitted into the cast iron bush. There is one that supports the outer periphery (see, for example, Patent Document 1). This suppresses the occurrence of a clearance between the inner periphery of the bearing portion and the outer periphery of the iron alloy ball bearing when the aluminum alloy crankcase thermally expands.
JP 2003-184648 A

By the way, in the above conventional configuration, although the coefficient of thermal expansion of the bearing portion is slightly reduced, the structure of the bearing portion is complicated by having a double bush, and the press-fitting process of the steel bush is also added. There is a problem of end. Further, since the difference in coefficient of thermal expansion between the bearing portion and the ball bearing still exists, the occurrence of the clearance can be considered.
Therefore, the present invention provides a crankshaft support structure in which a ball bearing inserted through a crankshaft journal is supported by a bearing portion provided in an aluminum alloy crankcase. An object of the present invention is to effectively suppress generation of a clearance between a bearing portion and a ball bearing.

As a means for solving the above problem, the invention described in claim 1 includes an aluminum alloy crankcase (16) divided into a left case half (18) and a right case half (19), Left and right bearings (53) are respectively provided on left and right side walls (51) that are formed in the left case half (18) and the right case half (19) and are arranged to be orthogonal to the crank axis (C1), In a crankshaft support structure for a motorcycle in which a ball bearing (52) inserted through a journal (42) of a crankshaft (15) is supported by the left and right bearings (53), on the inner peripheral side of the left and right bearings (53) iron alloy bushing (54) formed integrally with the insert during molding, to form the intramural oil passage (59) to either of said left and right side walls (51), in the wall An oil passage connected to the road (59) formed in the bushing (54), the engine oil to be supplied from the bushing (54) to the crankpin (37) of the crankshaft (15), the right and left bearing portions ( 53), the radial thickness (b) of the bush support layer (55) for supporting the bush (54) from the outer peripheral side is 1/3 or less of the radial thickness (a) of the bush (54), And, in a cross-sectional view along the crank axis (C1), the outer peripheral surface in the radial direction of the bush (54) is located in the vicinity of the outer peripheral surface of the crank pin (37) far from the crank axis (C1). It is characterized by that.

The invention described in claim 2 is characterized in that the thickness (a) in the radial direction of the bush (54) is made larger than the thickness (c) in the axial direction of the bush (54).

According to the present invention , the ratio of the bush made of the iron alloy in the bearing portion is increased, and the thermal expansion coefficient of the bearing portion can be effectively brought close to the thermal expansion coefficient of the iron alloy. It is possible to effectively suppress the occurrence of clearance between the inner peripheral surface (bearing support surface) and the outer peripheral surface (supported surface) of the ball bearing, and to prevent generation of vibration and noise based on the clearance.
Further, it is only necessary to provide a single bush on the bearing portion, and the structure of the bearing portion and the processing process can be simplified.

According to the present invention , the decrease in bush support rigidity due to the thin bush support layer can be compensated by the rigidity of the bush itself, and the ratio of the bush in the bearing portion is increased, and the coefficient of thermal expansion is increased. Can be brought closer to the thermal expansion coefficient of the iron alloy more efficiently.

  Embodiments of the present invention will be described below with reference to the drawings. Note that the directions such as front, rear, left and right in the following description are the same as those in the vehicle unless otherwise specified. In the figure, the arrow FR indicates the front of the vehicle, the arrow LH indicates the left side of the vehicle, and the arrow UP indicates the upper side of the vehicle.

  A scooter type motorcycle 1 shown in FIG. 1 includes a head pipe 3 at a front end portion of a vehicle body frame 2, and supports a front fork 5 and a steering handle 6 that pivotally support the front wheel 4 on the head pipe 3 in a steerable manner. At the rear of the body frame 2, there is an integral swing type power unit (hereinafter referred to as a swing unit) 11 in which an engine 7 that is a prime mover of the motorcycle 1 is disposed at the front and a rear wheel 8 that is a drive wheel is disposed at the rear. Supported.

  The lower front portion of the swing unit 11 is supported by the lower rear portion of the vehicle body frame 2 via the link member 12 so as to be swingable up and down. On the other hand, the rear end portion of the swing unit 11 is supported by the rear end portion of the vehicle body frame 2 via a rear cushion 13 that is a shock absorber. The swing unit 11 can swing up and down together with the rear wheel 8 around the link member 12 as a pivot, and constitutes a so-called unit swing type rear suspension.

The swing unit 11 is integrally formed with a front engine 7 and a rear left power transmission mechanism 14.
The engine 7 is a water-cooled four-stroke OHC single-cylinder engine in which the rotation axis (crank axis) C1 of the crankshaft 15 is aligned in the left-right direction (vehicle width direction), and the cylinder 17 is moved forward from the front end of the crankcase 16. It is made to project substantially horizontally (inclined slightly to the front in detail). In FIG. 1, symbol C2 indicates the axis of the cylinder 17 (cylinder axis).

Referring to FIG. 2, the crankcase 16 is divided into left and right case halves 18 and 19 with a dividing plane orthogonal to the left and right direction as a boundary.
The left case half 18 of the crankcase 16 is integrally formed with a left case body 21 that protrudes leftward from the left side of the rear part and then extends rearward. The left case main body 21 constitutes a transmission case 23 in the power transmission mechanism 14 together with a left case cover 22 attached to the left side thereof.

  A belt-type continuously variable transmission mechanism 24 in the power transmission mechanism 14 is accommodated in the transmission case 23, and a drive pulley 25 of the belt-type continuously variable transmission mechanism 24 is coaxially supported on the left side portion of the crankshaft 15. . A kick starter device 26 is disposed outside the belt-type continuously variable transmission mechanism 24 in the vehicle width direction in the transmission case 23. A fan 25 a for introducing cooling air into the transmission case 23 is provided on the left side of the drive pulley 25.

  On the other hand, a right case cover 28 that supports the radiator 27 is attached to the right side of the right case half 19 of the crankcase 16. Inside the right case cover 28, a generator 29 that is a generator of the motorcycle 1 is provided coaxially with the crankshaft 15. The outer rotor 29a located on the right side of the generator 29 is supported on the right side portion of the crankshaft 15 so as to be integrally rotatable. A fan 29b for supplying cooling air to the radiator 27 adjacent to the right side is provided on the right side of the outer rotor 29a. The outer rotor 29a has a cup shape that opens to the right, and a stator coil 29c supported by the right case half 19 is disposed inside the outer rotor 29a.

The cylinder 17 of the engine 7 includes a cylinder body 31 directly attached to the front end portion of the crankcase 16, a cylinder head 32 attached to the front end portion of the cylinder body 31, and a head cover 33 attached to the front end portion of the cylinder head 32. It has.
A piston 35 defining a combustion chamber 34 is fitted in the cylinder body 31 so as to be able to reciprocate, and a small end portion of a connecting rod 36 is swingably connected to the piston 35 via a piston pin 35a. A crank pin 37 of the crankshaft 15 is rotatably connected to a large end portion of the crankshaft 15 via a roller bearing 38. In the figure, reference numeral 39 denotes a spark plug that faces the combustion chamber 34.

  The crankshaft 15 includes left and right crank webs 41 that support the crank pins 37, left and right journals 42 that project outward from the left and right crank webs 41, and left and right support shafts 43 that extend further left and right outward from the left and right journals 42. Are integrally formed. The crankshaft 15 is configured as an assembly type in which left and right crank webs 41, a journal 42 and a support shaft 43 are respectively integrated into a left and right divided body, and the left and right divided bodies are integrally coupled via a crank pin 37.

A drive sprocket 45 for driving the camshaft 44 in the cylinder head 32 is provided coaxially on the proximal end side of the right support shaft 43.
The cam shaft 44 is disposed in parallel with the crankshaft 15 in the cylinder head 32, and the left and right side portions thereof are rotatably supported by the cylinder head 32. Driven sprocket 46 to the right end of the camshaft 44 is mounted coaxially, cam chain 47 is wound on said drive sprocket 45 and the driven sprocket 46. A cam chain chamber 47 a that houses the cam chain 47 is provided on the right side of the cylinder 17.
When the camshaft 44 is rotationally driven in conjunction with the crankshaft 15, the intake / exhaust valves supported in the cylinder head 32 are driven to open / close the intake / exhaust ports (both not shown).

  On the right side of the cylinder head 32, a water pump 48 that circulates cooling water to each part of the engine is provided coaxially with the camshaft 44 and integrally rotatable. The cooling water inlet (or discharge port) of the water pump 48 is connected to the cooling water outlet (or inlet) of the radiator 27 via the cooling water hose 48a. A water jacket 49 for flowing cooling water from the water pump 48 is appropriately formed inside the cylinder head 32 and the cylinder body 31.

Immediately to the right side of the drive sprocket 45, the drive gear 45a of the oil pump drive (not shown) is provided. The oil pump is located, for example, at the lower inner side of the crankcase 16, and engine oil discharged from the oil pump is supplied to the periphery of the connecting rod 36 through the crankpin 37 and the like, and is cammed through the cylinder body 31 and the cylinder head 32 and the like. Supplied around the shaft 44.

The left and right side walls 51 that are substantially orthogonal to the crank axis C1 of the crankcase 16 (the left and right case halves 18 and 19) have left and right bearing portions 53 that support the left and right journals 42 of the crankshaft 15 via left and right ball bearings 52. Each is provided.
The left and right bearing portions 53 are formed so that the periphery of a through hole formed in the left and right side walls 51 at the center of the crank axis C1 is thick (wide) in the axial direction for supporting the left and right ball bearings 52. The circumferential side is constituted by left and right bushes 54.

Here, the crankcase 16 (left and right case halves 18, 19) is, for example, a cast product made of an aluminum alloy (for example, JIS5302), and the crankshaft 15 is made of an iron alloy (for example, JIS4051). For example, it is a forged product. The coefficient of linear expansion as the coefficient of thermal expansion of the crankcase 16 (aluminum alloy) is approximately 2.4 × 10 ⁻⁵ / K, and the coefficient of linear expansion as the coefficient of thermal expansion of the crankshaft 15 (iron alloy) is approximately 1. 2 × 10 ⁻⁵ / K.

  Further, the outer race and the inner race of the left and right ball bearings 52 are made of an iron alloy having a thermal expansion coefficient equivalent to that of the crankshaft 15 (for example, JIS 4805), and the left and right bushes 54 are also made of the crankshaft 15 (for example, JIS5502). It is made of an iron alloy having the same thermal expansion coefficient.

  The left and right bushes 54 are annular with the crank axis C1 as the center, and the cross-sectional shape orthogonal to the circumferential direction has a substantially rectangular shape having two sides substantially parallel to the crank axis C1 and two sides orthogonal to the crank axis C1. Is done. The outer race of the left and right ball bearings 52 is press-fitted and held on the inner peripheral side of the left and right bushes 54, and the left and right journals 42 are inserted and held on the inner peripheral side of the left and right ball bearings 52.

  Referring to FIG. 3A, the left and right bushes 54 are inserted at the time of molding of the crankcase 16 (left and right case halves 18 and 19), which is a cast product made of an aluminum alloy, so that the outer peripheral side and the left and right outer sides thereof are inserted. The crankcase 16 is integrally held while being supported. Hereinafter, a portion (aluminum alloy layer) that supports the left and right bushes 54 from the outer peripheral side in the thick portion of the left and right bearing portions 53 is referred to as a bush support layer 55. 3A shows the left bearing portion 53, the configuration shown in this figure also has the right bearing portion 53 unless otherwise specified.

  The left and right outer portions of the thick portion of the left and right bearing portions 53 are left and right bush outer support portions 56 that support the left and right bushes 54 from the left and right outer sides. ) Are left and right bearing outer support portions 57 that support the left and right outer sides of the outer race of the left and right ball bearings 52.

  The left and right bearing portions 53 are asymmetrical for the sake of convenience such as formation of an oil passage for engine oil in the crankcase 16. For example, in the right bearing portion 53, an oil passage that is continuous with an oil passage 59 (see FIG. 2) formed in the right side wall 51 is appropriately formed in the right bush 54, and engine oil is supplied from the right bush 54 to the crank pin 37 side. It can be supplied.

  By the way, when the bush support layer 55 made of aluminum alloy is thicker than the bush 54 made of iron alloy, the bush 54 is excessively expanded by being dragged by the thermal expansion of the bush support layer 55, and the bearing portion 53. The overall thermal expansion coefficient approaches the thermal expansion coefficient of the aluminum alloy. For this reason, when the engine is hot, the inner peripheral surface of the bearing portion 53 (bush 54) is larger in diameter than the outer peripheral surface of the ball bearing 52 made of iron alloy, and a clearance may be generated therebetween.

  On the other hand, in the bearing portion 53, as shown in FIG. 3A, the radial thickness b of the bush support layer 55 is smaller than the radial thickness a of the bush 54 (specifically, 1 / The ratio of the bushing 54 in the bearing portion 53 is increased to bring the thermal expansion coefficient of the entire bearing section 53 close to the thermal expansion coefficient of the iron alloy. The bush support layer 55 may be cut out.

  Here, the curve J in FIG. 3B shows the change in the linear expansion coefficient of the entire bearing portion 53 with respect to the ratio b / a obtained by dividing the radial thickness b of the bush support layer 55 by the radial thickness a of the bush 54. Is shown. The curve J is obtained from a plurality of actually measured values of the linear expansion coefficient obtained by changing the ratio b / a. In the figure, straight line A represents the linear expansion coefficient of the aluminum alloy, and straight line F represents the linear expansion coefficient of the iron alloy.

  From the description of FIG. 3 (b), the bearing thickness 55 is decreased by decreasing the radial thickness b of the bush support layer 55 and increasing the radial thickness a of the bush 54 (by decreasing the ratio b / a). It can be seen that the linear expansion coefficient of the entire portion 53 decreases and approaches that of the iron alloy. In addition, it can be seen that in the range where the ratio is 1/3 or less, the ratio of reduction in the linear expansion coefficient of the entire bearing portion 53 is increased. That is, if the ratio b / a is 1/3 or less, the linear expansion coefficient of the entire bearing portion 53 can be brought close to that of the iron alloy efficiently.

  3A, in the bearing portion 53, the axial thickness c of the bush 54 is substantially the same as the radial thickness a (specifically, the radial thickness a). Is set to be slightly thicker than the axial thickness c). As a result, the cross-sectional shape orthogonal to the circumferential direction of the bush 54 is a substantially square shape, and a reduction in the bush support rigidity due to the thin bush support layer 55 is ensured in a balanced manner by the rigidity of the bush 54 itself.

  As described above, the crankshaft support structure in the above embodiment supports the ball bearing 52 through which the journal 42 of the crankshaft 15 is inserted by the bearing portion 53 provided in the crankcase 16 made of aluminum alloy, A bush 54 made of an iron alloy is provided on the inner peripheral side of the bearing portion 53, and the radial thickness b of the bush support layer 55 that supports the bush 54 from the outer peripheral side in the bearing portion 53 is set in the radial direction of the bush 54. 1/3 or less of the thickness a.

According to this configuration, the ratio of the iron alloy bushing 54 in the bearing portion 53 is increased, and the coefficient of thermal expansion of the bearing portion 53 can be brought close to the coefficient of thermal expansion of the iron alloy efficiently. The occurrence of a clearance between the inner peripheral surface (bearing support surface) of the bush 54 and the outer peripheral surface (supported surface) of the ball bearing 52 at the time is effectively suppressed, and the generation of vibration and noise based on the clearance is prevented. be able to.
Further, it is only necessary to provide the bearing portion 53 with a single bush 54, and the structure of the bearing portion 53 and the processing steps can be simplified.

  Further, in the above crankshaft support structure, the bush support rigidity is obtained by making the bush support layer 55 thin by making the thickness a in the radial direction of the bush 54 larger than the thickness c in the axial direction of the bush 54. Can be compensated for by the rigidity of the bush 54 itself, and the ratio of the bush 54 to the bearing portion 53 is increased, and the thermal expansion coefficient of the bearing section 53 is made closer to the thermal expansion coefficient of the iron alloy more efficiently. be able to.

The present invention is not limited to the above-described embodiments, and is applicable not only to motorcycles but also to various vehicles such as three-wheel or four-wheel vehicles, various transport equipment such as aircraft and ships, and further to cranks. Applicable to all reciprocating engines having a shaft.
The configuration in the above embodiment is an example of the present invention, and it goes without saying that various modifications can be made without departing from the gist of the present invention, including the number of engine cylinders and their arrangement.

1 is a left side view of a motorcycle according to an embodiment of the present invention. FIG. 3 is a developed cross-sectional view along the crank axis of the engine of the motorcycle. (A) is an enlarged view of the bearing part in FIG. 2, (b) is a graph which shows the change of the linear expansion coefficient accompanying the dimension change of the said bearing part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 15 Crankshaft 16 Crankcase 42 Journal 52 Ball bearing 53 Bearing part 54 Bush 55 Bush support layer a Bush radial thickness b Bush radial thickness c Bush axial thickness

Claims (2)

An aluminum alloy crankcase (16) divided into a left case half (18) and a right case half (19);
Left and right bearing portions (53) are provided on left and right side walls (51) respectively formed on the left case half (18) and the right case half (19) and arranged to be orthogonal to the crank axis (C1). ,
In the crankshaft support structure for a motorcycle that supports the ball bearing (52) inserted through the journal (42) of the crankshaft (15) with the left and right bearings (53),
An iron alloy bush (54) is integrally provided on the inner peripheral side of the left and right bearings (53) with an insert at the time of molding ,
An in-wall oil passage (59) is formed in any one of the left and right side walls (51), and an oil passage continuing to the in-wall oil passage (59) is formed in the bush (54). 54) engine oil can be supplied to the crankpin (37) side of the crankshaft (15),
The radial thickness (b) of the bush support layer (55) for supporting the bush (54) from the outer peripheral side in the left and right bearing portion (53) is 1 of the radial thickness (a) of the bush (54). / 3 or less,
And, in a cross-sectional view along the crank axis (C1), the outer peripheral surface in the radial direction of the bush (54) is located in the vicinity of the outer peripheral surface of the crank pin (37) far from the crank axis (C1). A crankshaft support structure for a motorcycle . The crankshaft support structure for a motorcycle according to claim 1, wherein a thickness (a) in the radial direction of the bush (54) is made larger than a thickness (c) in the axial direction of the bush (54). .

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