JP2009228731A - Crankshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crankshaft which is constituted by connecting a pair of crankshaft halves each having a crank web which is continuously provided to a journal part in one piece and has a weight part in a position which is offset from the axis of the journal part by a crank pin, both ends of which are press-fitted into a press-fitting hole provided to the crank web, the crankshaft which suppresses a distortion/deformation amount caused by the press fitting of the crank pin, and reduces a time required for correction work, and increases productivity. <P>SOLUTION: The thinning sections 60, 61 of the surroundings of the press-fitting holes 52, 53, which are arranged on the sides of the weight parts 50c, 51c, are provided to the surfaces of the crank webs 50b, 51b facing each other, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  According to the present invention, a pair of crankshaft halves, in which a crank web having a weight portion at a position offset from an axis of the journal portion is integrally connected to the journal portion, is connected to the weight portion with respect to the axis of the journal portion. Relates to a crankshaft that is connected to a press-fit hole provided in the crank web at a position offset to the opposite side by a crank pin that presses both ends.

Such a crankshaft is already known from Patent Document 1 and the like.
Japanese Patent Publication No. 05-769

  By the way, the crankpin may be formed in a hollow shape in order to guide oil that performs lubrication with the large end portion of the connecting rod, and both ends of such a hollow shape crankpin are connected to a pair of crank webs. When the cylinder is press-fitted into the press-fitting hole, the crank pin is deformed so that both ends are crushed into a barrel shape. At this time, in the crank web of the crankshaft half, the crankshaft was assembled by connecting both crankshaft halves via crankpins because the rigidity on the journal side was larger than the rigidity on the opposite side. In this state, the crankshaft is in a deformed deformation state so that both crank webs are inclined toward the side where the weight portions are separated from each other. Therefore, after the press-fitting operation of the crankpin, an operation for correcting the distortion deformation as described above is required. When the deformation amount is large, the correction operation takes time, and the productivity is lowered.

  The present invention has been made in view of such circumstances, and provides a crankshaft that can suppress the amount of distortion deformation caused by press-fitting of a crankpin and reduce the time required for correction work to increase productivity. The purpose is to do.

  In order to achieve the above object, the invention according to claim 1 is a pair of crankshaft halves in which a crank web having a weight portion is integrally connected to the journal portion at a position offset from the axis of the journal portion. A crankshaft connected by a crank pin that presses both ends into press-fitting holes provided in the crank web at a position that is offset to the opposite side of the weight part with respect to the axis of the journal part. Of these, the lightening portions arranged on the weight portion side are provided on the surfaces of the crank webs facing each other.

  According to a second aspect of the invention, in addition to the configuration of the first aspect of the invention, the crank pin inserted into the large end portion of the connecting rod so as to be relatively rotatable is inserted into the large end portion of the connecting rod and the crank pin. An oil passage for guiding oil for lubricating the gap is provided coaxially so that one end is opened to one end of the crankpin and the other end is closed.

  Furthermore, in the invention described in claim 3, in addition to the configuration of the invention described in claim 1 or 2, the thinning portion has a groove shape having side surfaces facing each other and a closed end surface connecting the side surfaces. A bent portion having a curvature radius of less than ½ of the width of the thinned portion is formed between the both side surfaces and the closed end surface.

  According to the first aspect of the present invention, the lightening portions arranged on the weight portion side of the periphery of the press-fitting hole are provided on the mutually opposing surfaces of the crank web. A difference in rigidity around the press-fitting hole can be suppressed to a small value, whereby the amount of distortion deformation due to the press-fitting of the crank pin can be suppressed to a small value, and the productivity of the crankshaft can be increased. Moreover, although the amount of oil supply is relatively small on the rotation center side of the crankshaft, the oil supply performance of the thrust surface between the connecting rod and the connecting rod is improved by holding the oil in the lightening portion when the lightening portion is grooved. Can be achieved.

  According to the second aspect of the present invention, an oil passage for guiding oil for lubricating between the large end of the connecting rod and the crankpin is provided coaxially in the crankpin, while simplifying the oil passage. The amount of distortion deformation of the crankshaft can be kept small.

  Further, according to the invention described in claim 3, the radius of curvature of the bent portion formed between the inner peripheral side surface and the outer peripheral side surface of the groove-shaped cutout portion and the closed end surface is 1 / of the width of the groove. By setting it to less than 2, a part of the closed end face of the lightening portion can be made flat, and the amount of strain deformation of the crankshaft can be kept small.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 4 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a motorcycle power unit, FIG. 2 is an enlarged longitudinal sectional view of a crankshaft, and FIG. FIG. 4 is an enlarged view of a portion indicated by an arrow 4 in FIG.

  First, in FIG. 1, for example, a power unit P mounted on a motorcycle includes an OHC type internal combustion engine E which is a single-cylinder four-cycle and a transmission device T provided between the internal combustion engine E and an axle 10 of a rear wheel. Composed.

  The engine body 11 of the internal combustion engine E has a crankcase 13 that rotatably supports a crankshaft 12 having a rotation axis parallel to the axis of the axle 10, and a cylinder bore 17 in which a piston 18 is slidably fitted. The cylinder block 14 coupled to the crankcase 13, the cylinder head 15 coupled to the cylinder block 14 on the opposite side to the crankcase 13, and the head cover 16 coupled to the cylinder head 15 on the opposite side to the cylinder block 14. It consists of.

  A combustion chamber 21 is formed between the cylinder block 14 and the cylinder head 15 so that the top of the piston 18 faces. The piston 18 is connected to the crankshaft 12 via a connecting rod 19 and a crankpin 20. A spark plug 22 facing the combustion chamber 21 is attached to the right side surface of the cylinder head 15.

  The crankcase 13 includes a pair of case halves 13a and 13b that include an axis of the cylinder bore 17 and are coupled by a plane orthogonal to the axis of the crankshaft 12, and the crankshaft 12 is composed of both case halves 13a and 13b. It is supported rotatably. Thus, a ball bearing 23 is interposed between the crankshaft 12 and the one case half 13a, and a ball bearing 24 is interposed between the crankshaft 12 and the other case half 13b.

  An intake valve (not shown) and an exhaust valve (not shown) are disposed in the cylinder head 15 so as to be openable and closable. The intake valve and the exhaust valve are provided between the cylinder head 15 and the head cover 16. A valve operating mechanism 25 that opens and closes is accommodated. The camshaft 26 provided in the valve mechanism 25 transmits the rotational power of the crankshaft 12 through a timing transmission mechanism 28 provided with a cam chain 27 at a reduction ratio of 1/2. 27 is housed in a cam chain chamber 29 formed over the cylinder block 14, the cylinder head 15 and the head cover 16 so as to be able to run.

  The outer rotor 31 of the generator 30 is fixed to one end portion of the crankshaft 12 outside the crankcase 13, and the stator 32 surrounded by the outer rotor 31 is attached to the case half 13 a of the crankcase 13. The generator cover 33 is fixed.

  A transmission case 35 extending to the left side of the rear wheel is connected to the crankcase 13 while facing the front in the running direction of the motorcycle. The transmission case 35 includes a case main body 36 integrally connected to the case half 13 b of the crankcase 13 and extending rearward, and a transmission chamber 39 formed between the case main body 36 and the case main body 36. A left side cover 37 fastened to the main body 36 from the left side, and a right side cover 38 fastened to the right rear portion of the case main body 36 by forming a gear chamber 40 between the case main body 36 and the rear wheel axle. 10 is rotatably supported by the rear part of the case main body 36 and the right side cover 38.

  The transmission device T includes a V-belt type continuously variable transmission 41 accommodated in the transmission chamber 39 and a reduction gear mechanism 42 provided between the continuously variable transmission 41 and the axle 10 and accommodated in the gear chamber 40. It consists of.

  The continuously variable transmission 41 includes a drive pulley 43 connected to the other end of the crankshaft 12 outside the crankcase 13, a rear portion of the case main body 36, and a right cover 38 having an axis parallel to the crankshaft 12. And a driven pulley 46 that is mounted on a driven shaft 44 that is rotatably supported by a rotary clutch 45 via a centrifugal clutch 45, and a drive pulley 43 and an endless V-belt 47 that is wound around the driven pulley 46.

  Thus, the drive pulley 43 includes a ramp plate 48 fixed to the crankshaft 12 and a plurality of weight rollers 49 accommodated in a floating state between the drive pulley 43 and the crankshaft 12 according to an increase in the rotational speed of the crankshaft 12. It operates to increase the contact radius to the V-belt 47 in response to the 12 radial outward movements.

  On the other hand, the driven pulley 46 operates so that the contact radius of the V-belt 47 becomes smaller as the contact radius of the V-belt 47 to the drive pulley 43 becomes larger, and thereby, between the crankshaft 12 and the driven shaft 44. A continuously variable transmission according to the rotation of the crankshaft 12 is performed.

  The reduction gear mechanism 42 is provided between the driven shaft 44 and the axle 10 and is housed in the gear chamber 40. After the rotational power of the driven shaft 44 in the continuously variable transmission 41 is reduced by the reduction gear mechanism 42, It is transmitted to the wheel axle 10.

  In FIG. 2, the crankshaft 12 is formed by connecting a pair of crankshaft halves 50 and 51, which are respectively forged and formed, via a crankpin 20, and one crankshaft half 50 includes a journal portion 50a. Further, a crank web 50b having a weight part 50c is integrally connected to a position offset from the axis of the journal part 50a, and the other half crankshaft 51 is connected to the journal part 51a. A crank web 51b having a weight portion 51c is integrally provided at a position offset from the center.

  Press-fitting holes 52 and 53 are provided at positions offset from the weight portions 50c and 51c with respect to the axis of the journal portions 50a and 51a of the crank webs 50b and 51b in both crankshaft halves 50 and 51, respectively. The both ends of the crankpin 20 are press-fitted into the press-fitting holes 52 and 53.

  As shown in FIG. 1, a needle bearing 54 is interposed between the crank pin 20 and the large end 19a of the connecting rod 19, and the crank pin 20 is lubricated toward the needle bearing 54 side. An oil passage 55 for guiding the oil for use is provided coaxially so that one end is open to one end of the crankpin 20 on the crankshaft half 50 side and the other end is closed, and the inner end is passed through the oil passage 55. Thus, the outer end of the passage hole 56 provided in the crankpin 20 is opened to the outer periphery of the crankpin 20.

  On the other hand, in the journal portion 50a of the crankshaft half 50, an oil passage 57 for guiding oil supplied from the generator cover 33 side opens one end to the generator cover 33 side and closes the other end. A passage hole 58 that is provided coaxially and allows the inner end of the oil passage 57 to pass through the inner end thereof is located inside the ball bearing 23 (see FIG. 1) interposed between the crankcase 13 and the crankshaft 12. On the other hand, the journal pin 50a is provided at the end of the crankshaft half 50 near the crank web 50b so that the outer end faces the one end side of the crankpin 20.

  A guide plate 59 for guiding the oil guided from the passage hole 58 to the oil passage 55 of the crankpin 20 is formed on the surface of the crank web 50b on the side of the journal portion 50a of the crank web 50b by caulking or the like. Mounted.

  By the way, in the crank webs 50b and 51b of both crankshaft halves 50 and 516, the thickness in the direction along the axis of the journal portions 50a and 51a is uneven around the press-fitting holes 52 and 53. Since the rigidity of the portion on the 51a side is larger than the rigidity of the portion on the opposite side of the journal portions 50a and 51a with respect to the axis of the press-fit holes 52 and 53, both end portions of the crank pin 20 are inserted into the press-fit holes 52 and 53. In a state where the crankshaft 12 is assembled by press-fitting, the crankshaft 20 may be distorted and deformed so that both the crank webs 50b and 51b are inclined to the side where the weight portions 50c and 51c are separated from each other.

  Therefore, the groove-shaped thinned portions 60, 60 arranged on the weight portions 50c, 51c side of the periphery of the press-fitting holes 52, 53 have a difference in rigidity around the press-fitting holes 52, 53 in the crank webs 50b, 51b. In order to keep the crank webs 50b, 51b opposite to each other in order to keep them small by reducing the rigidity due to the formation of the thinned portions 60 ..., each of the thinned portions 60 ... is press-fitted as shown in FIG. It is formed in an arc shape in a range of an angle α centered on the axis of the press-fitting holes 52 and 53 at a position spaced from the inner peripheral surface of the holes 52 and 53 by a distance L.

  As shown in FIG. 4, the lightening portion 60 has an inner peripheral side surface 60a and an outer peripheral side surface 60b facing each other, and a closed end surface 60c connecting the inner peripheral side surface 60a and the outer peripheral side surface 60b, Cutting is performed so as to have a depth d2 shorter than the press-fit depth d1 into the press-fit holes 52 and 53 of the crankpin 20, but the inner peripheral side surface 60a and the outer peripheral side surface 60b, and the closed end surface 60c, In between, bent portions 60d and 60e having a curvature radius less than ½ of the width W of the thinned portion 60 are formed, and the closed end surface 60c is formed as a flat surface.

  Next, the operation of the first embodiment will be described. The crank webs 50b, 51b of the pair of crankshaft halves 50, 51 are press-fitted at both ends into press-fitting holes 52, 53 provided in the crank webs 50b, 51b. In the crankshaft 12 connected by the crank pin 20 to be squeezed, a groove-shaped hollow portion 60 disposed on the weight portions 50c, 51c side provided around the press-fit holes 52, 53 on the crank webs 50b, 51b. , 60 are provided on the surfaces of the crank webs 50b, 51b facing each other.

  By reducing the rigidity due to the formation of the thinned portions 60..., The difference in rigidity around the press-fitting holes 52 and 53 in the crank webs 50 b and 51 b can be suppressed to be small, thereby causing distortion of the crankshaft 12 due to press-fitting of the crankpin 20. The amount of deformation can be kept small, and the productivity of the crankshaft 12 can be increased.

  Here, when the press-fitting depth d1 of the crank pin 20 to the press-fitting holes 52 and 53 is 13.5 mm, the distance L from the inner peripheral surface of the press-fitting holes 52 and 53 to the thinned parts 60. As a result of changing the angle α and the depth d2 of the thinned portion 60, the crankshaft 12 has a distance L of 2 mm, the angle α is 180 degrees, and the depth d2 of the thinned portion 60 is 5 mm. It was found that the distortion deformation of can be suppressed most effectively.

  Moreover, although the oil supply amount is relatively small on the rotation center side of the crankshaft 12, the thrust surface between the connecting rod 19 and the large end portion 19a is maintained by holding oil in the grooved portion 60. The oil supply performance can be improved.

  Further, the groove-shaped cutout portion 60 has an inner peripheral side surface 60a and an outer peripheral side surface 60b that face each other, and a closed end surface 60c that connects the inner peripheral side surface 60a and the outer peripheral side surface 60b. Between the side surface 60a and the outer peripheral side surface 60b, and the closed end surface 60c, bent portions 60d and 60e having a radius of curvature less than 1/2 of the width W of the thinned portion 60 are formed. The closed end surface 60c is formed as a flat surface, and the deformation of the crankshaft 12 can be effectively suppressed by adopting the shape of the hollow portion 60... In which the closed end surface 60c is formed flat. .

  Further, an oil passage 55 for guiding the oil for lubricating between the large end portion 19a of the connecting rod 19 and the crank pin 20 to the crank pin 20 opens one end to one end of the crank pin 20 and closes the other end. Since the oil passage 55 is simplified, the amount of distortion deformation of the crankshaft 12 can be suppressed small.

  Next, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 is a sectional view corresponding to FIG. 2, FIG. 6 is a sectional view taken along line 6-6 of FIG. Portions corresponding to one embodiment are only shown with the same reference numerals and are not described in detail.

  On the opposite surfaces of the crank webs 50b and 51b of the crankshaft halves 50 and 51 to be formed by forging, a lightening portion 61 arranged on the weights 50c and 51c side of the periphery of the press-fitting holes 52 and 53 is provided. , 61 are provided. In FIG. 6, in order to clearly show the thinned portion 61, the region of the thinned portion 61 is indicated by a grid-like oblique line.

  These thinning portions 61... Project from the mutually facing surfaces of the crank webs 50 b and 51 b and cut out part of cylindrical projections 62 and 63 surrounding the end portions of the press-fit holes 52 and 53. It has an arc shape with the outer peripheral side opened, and is formed at the same time as forging of the crankshaft halves 50 and 51.

  Also in the second embodiment, as in the first embodiment, the difference in rigidity around the press-fitting holes 52 and 53 in the crank webs 50b and 51b can be suppressed by the reduction in rigidity due to the formation of the thinned portions 61. As a result, the amount of deformation of the crankshaft 12 due to the press-fitting of the crankpin 20 can be kept small, and the productivity of the crankshaft 12 can be increased.

  In addition, since it is unnecessary to form the thinned portions 61 through post-processing after forging the crankshaft halves 50 and 51, productivity can be further increased.

  The formation of the lightening portions 61 is not limited to the simultaneous molding at the time of forging the crankshaft halves 50 and 51. In the case of small-scale production, the machine after the forging of the crankshaft halves 50 and 51 is formed. The thinned portion 61 may be formed by processing so as to keep the amount of distortion deformation small.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.

1 is a longitudinal sectional view of a motorcycle power unit according to a first embodiment; It is an expansion longitudinal cross-sectional view of a crankshaft. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. FIG. 4 is an enlarged view of a portion indicated by an arrow 4 in FIG. 2. It is sectional drawing corresponding to FIG. 2 of 2nd Example. FIG. 6 is a sectional view taken along line 6-6 of FIG.

Explanation of symbols

12 ... crankshaft 19 ... connecting rod 19a ... large end 20 of connecting rod ... crank pins 50, 51 ... crankshaft halves 50a, 51a ... journal parts 50b, 51b .... Crank webs 50c, 51c ... Weight parts 52, 53 ... Press-fitting holes 55 ... Oil passages 60, 61 ... Meat removal parts 60a, 60b ... Side face 60c ... Closed end face 60d, 60e ・ ・ ・ Folding part

Claims (3)

  A pair of crank webs (50b, 51b) having weight portions (50c, 51c) integrally connected to the journal portions (50a, 51a) at positions offset from the axis of the journal portions (50a, 51a). A crankshaft half (50, 51) is provided on the crank web (50b, 51b) at a position offset to the opposite side of the weight (50c, 51c) with respect to the axis of the journal (50a, 51a). In a crankshaft formed by connecting both ends of the press-fitting holes (52, 53) with crank pins (20), the crankshaft is arranged on the weight part (50c, 51c) side of the periphery of the press-fitting holes (52, 53). Are formed on the mutually opposing surfaces of the crank webs (50b, 51b), respectively. Crankshaft, characterized in that eclipsed.   The crank pin (20) inserted through the large end (19a) of the connecting rod (19) in a relatively rotatable manner is lubricated between the large end (19a) of the connecting rod (19) and the crank pin (20). The crankshaft according to claim 1, wherein an oil passage (55) for guiding oil is provided coaxially so that one end is opened to one end of the crank pin (20) and the other end is closed.   The said lightening part (60) is a groove-shaped thing which has the side surface (60a, 60b) which mutually opposes, and the obstruction | occlusion end surface (60c) which connects between those side surfaces (60a, 60b), The said both sides | surfaces Between the (60a, 60b) and the closed end surface (60c), there are curved portions (60d, 60e) which are bent with a radius of curvature of less than half the width of the thinned portion (60), respectively. The crankshaft according to claim 1, wherein the crankshaft is formed.

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