JP3993547B2 - Crankshaft bearing structure in internal combustion engine - Google Patents

Description

  The present invention relates to a bearing structure that rotatably supports a crankshaft on a crankcase in an internal combustion engine.

  Generally, in a single-cylinder internal combustion engine for motorcycles or the like, a piston that is rotatably mounted on a crankcase via a pair of left and right rolling bearings on a crankcase and that is slidably engaged with a cylinder bore via a connecting rod on a crankpin of the crankshaft In this case, the outer race and the inner race of the pair of rolling bearings are connected to the crankcase. The bearings and the journal shaft of the crankshaft are press-fitted and fitted to prevent rattling due to rattling between them, maintaining the desired bearing function of the crankshaft and ensuring smooth and light rotation. It is desirable to do.

  However, as described above, when the left and right rolling bearings are press-fitted into both the crankshaft and the crankcase, there arises a problem that it is difficult to assemble the crankshaft to the crankcase and perform subsequent maintenance.

  Therefore, conventionally, in order to solve this problem, as shown in FIG. 9, when assembling the crankshaft to the crankcase, the right-hand side crankcase half is preliminarily placed before the crankshaft is assembled to the crankcase. The outer race of the rolling bearing is press-fitted and fitted, and the inner race of the left rolling bearing is press-fitted and fitted to the left journal shaft of the crankshaft, and when the crankshaft is assembled, the right journal shaft of the crankshaft is A left-side rolling bearing that is press-fitted into the inner race of the right-hand rolling bearing (the outer race is already press-fitted into the right-hand crankcase half), and then the inner race is already press-fitted into the left journal shaft of the crankshaft. Of the outer race on the left crankcase half So as to fit) by, so that to if easier subsequent maintenance as well as facilitate the assembly of the crankcase of the crankshaft.

  However, in this case, it is unavoidable that some “backlash” is generated between the outer race of the left rolling bearing and the bearing surface of the crankcase. Therefore, when the internal combustion engine is operated, There is a problem that not only a hitting sound is generated due to the above, but also a desired bearing function cannot be obtained.

Therefore, in Patent Document 1 below, a coil spring interposed between the outer surface of one of the pair of ball bearings (left side) outer race by a push plug having an inclined pressing surface and the presser plate. There has been proposed one that absorbs the “backlash” by pressing in the axial direction with the elastic force.
JP 2003-83080 A

  However, in the above-mentioned Patent Document 1, as shown in FIG. 10, the presser plate pushed outward by the coil spring in the free length state is detached from the positioning member during the assembly of the push plug. Therefore, the operator has to assemble the coil spring while compressing the coil spring or holding the presser plate by hand, and there is a problem that the assembly is troublesome and troublesome.

  The present invention has been made in view of such circumstances, and it is very easy and easy to assemble a backlash absorbing means having a push plug that presses an outer race of a rolling bearing in its axial direction into a crankcase. It is an object of the present invention to provide a crankshaft bearing structure in a novel internal combustion engine that can solve the above-mentioned problems.

In order to achieve the above object, according to the first aspect of the present invention, a crankshaft is rotatably supported by a crankcase via a rolling bearing, and a backlash absorbing means is provided between the outer race of the rolling bearing and the crankcase. In the bearing structure of the crankshaft in the internal combustion engine that absorbs radial play generated between the outer race of the rolling bearing and the bearing hole of the crankcase by the means,
The backlash absorbing means is provided movably on the crankcase and pushes the outer race of the rolling bearing in the radial direction of the crankshaft, a spring set plate bolted to the crankcase, a push plug and a spring set A spring member interposed between the plates and elastically biasing the push plug toward the outer race, and the spring set plate has a bent portion that is bent toward the crankcase, and the bent portion includes the spring The first feature is that when the member is in a free length state and the spring set plate is in a temporarily fastened state, the member is engaged with a positioning portion formed in the crankcase to be positioned.

  In order to achieve the above object, according to a second aspect of the present invention, in the first aspect of the present invention, the crankcase is integrally formed with a boss protruding from an outer surface thereof, and the push is pushed onto the boss. A plug is movably provided. On the other hand, a concave portion for receiving a free end of the spring member is formed in an intermediate portion of the spring set plate so as to face the boss portion. The second feature is that the boss and the recess are fitted to each other.

  Furthermore, in order to achieve the above-mentioned object, the invention of claim 3 is the one according to claim 1 or 2, wherein the positioning portion formed on the crankcase is arranged such that the spring set plate is disposed outside the crankcase. The third feature is that it is formed in a hawk shape that is open to the outer surface so that it can be received from the outside.

  According to the first feature of the invention of claim 1, when the “backlash absorbing means” comprising the push plug, the spring member and the spring set plate is assembled to the crankcase, the spring member remains in a free length state, that is, the spring load is reduced. Since the spring set plate can be positioned without being applied, the operator can assemble the “backlash absorbing means” to the crankcase without compressing the spring member or pressing the spring set plate. The assembly workability can be greatly improved. Moreover, since the spring set plate has a bent portion bent toward the crankcase side, the bent portion can be received by the positioning portion on the crankcase side without protruding the spring set plate larger than the crankcase. The space occupied for assembling the “backlash absorbing means” can be narrow.

  According to the second feature of the invention of claim 2, in addition to the first feature, the boss portion formed in the crankcase and the recess of the spring set plate in the assembled state of the “backlash absorbing means”. Are fitted to each other, so that the “backlash absorbing means” can be stored compactly on the outer surface of the crankcase, and there is no part that protrudes greatly.

  Furthermore, according to the third feature of the invention of claim 3, in addition to the first or second feature, the positioning operation of the spring set plate to the crankcase is easy.

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

  In the accompanying drawings, FIG. 1 is a longitudinal sectional side view of an essential part of an internal combustion engine having a bearing structure for a crankshaft of the present invention, FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 4 is an enlarged sectional view taken along line 4-4 of FIG. 3, FIG. 5 is an enlarged sectional view taken along line 5-5 of FIG. 3, and FIG. 6 is a backlash absorbing means. FIG. 7 is a perspective view of the movement restraining member, and FIG. 8 is an operation view showing a state when the backlash absorbing means is assembled.

  1 and 2, an OHC type four-cycle single-cylinder internal combustion engine E includes a cylinder block CB, a cylinder head CH fixed on the deck surface, and a left and right fixed to the lower part of the cylinder head CH. A split crankcase CC and a head cover HC attached to the upper surface of the cylinder head CH are provided. A cylinder 1 having a cylinder sleeve 2 provided at the center of the cylinder block CB includes a piston 3. A combustion chamber 4 is formed in the cylinder head CH so as to be slidably fitted and facing the top surface of the piston 3. A small end portion of the connecting rod 5 is rotatably connected to the piston pin of the piston 3, and a large end portion of the connecting rod 5 is rotatably connected to the crank pin 7 of the crankshaft 6. The crankshaft 6 is rotatably supported by the crankcase CC via left and right rolling bearings BB and BR which will be described later.

  The crankcase CC is formed by casting a light alloy such as iron or aluminum, and the left crankcase half 10 and the right crankcase half 11 are integrally connected by a plurality of bolts 14. A left cover 12 is covered on the outer surface of the left crankcase half 10 by a bolt 15, and a right cover 13 is covered on the outer surface of the right crankcase half 11 by a bolt 16. Fixed to. The left and right crankcase halves 10 and 11 are integrally formed with left and right journal walls 10j and 11j facing each other with a space therebetween, and these left and right journal walls 10j and 11j are on the same axis. The left and right bearing holes 18, 19 (the left bearing hole 18 is larger in diameter than the right bearing hole 19) are opened, and the bearing surfaces of the left and right bearing holes 18, 19 are made of Fe that is cast when the crankcase is cast. It is formed by a cast ring. In the left and right bearing holes 18 and 19, the left and right journal shaft portions 6jl and 6jr of the crankshaft 6 are rotatably supported via the left and right side rolling bearings BB and BR. As clearly shown in FIG. 4, the left side rolling bearing BB is constituted by a ball bearing, and the right side rolling bearing BR is constituted by a roller bearing. The inner race 22 of the left rolling bearing, that is, the ball bearing BB, is press-fitted into the left journal shaft portion 6jl of the crankshaft 6, and the outer race 23 is loosely fitted into the bearing hole 18 of the left journal wall 10j (in the radial direction). A little backlash). The outer race 23 of the ball bearing BB is extended axially outward (in a direction away from the cylinder axis) from the inner race 22, and an “circulation suppression means S” described later is formed on the inner peripheral surface of the extension 23 e. , And the hook portion 40f of the movement suppressing member 40 is detachably engaged with the engagement groove 41. As shown in FIG. 4, between the engagement groove 41 and the hook portion 40f, the outer race 23 can be allowed to move slightly in the axial direction with respect to the hook portion 40f. A slit is provided in

  Further, the inner race 26 of the right side rolling bearing, that is, the roller bearing BR is inserted into the right journal shaft portion 6jr of the crankshaft 6, and the outer race 27 is pressure-fitted into the bearing hole 19 of the right journal wall 11j. The After the inner race 26 is inserted into the right journal shaft portion 6jr of the crankshaft 6, the inner race 26 is fixed to the right journal shaft portion 6jr of the crankshaft 6 by the gear group 62 and the centrifugal filter 63 (see FIG. 1). ) Together with the nut from the shaft end of the crankshaft 6.

  As shown in FIGS. 1 and 3, between the crankshaft 6 and the cylinder 1, the left journal wall 10 j of the left crankcase half 10 is close to the upper outer side of the ball bearing BB, and the ball bearing BB A “backlash absorbing means A” for absorbing the “backlash” in the radial direction between the outer race 23 and the bearing hole 18 is provided along the axial direction of the crankshaft 6.

  As shown clearly in FIGS. 3, 4, and 6, the “backlash absorbing means A” includes a push plug 30, a coil spring 31, and a spring set plate 32. The push plug 30 is formed in a hollow cylindrical shape having a bottom, and an inclined surface 30s is formed at a corner portion of the bottom end side wall. The push plug 30 is slid into a cylindrical hole 35 formed in a boss portion 34 obliquely above the ball bearing BB of the left journal wall 10j and having an axis in the axial direction of the crankshaft 6 (perpendicular to the cylinder axis). It is movably fitted.

  As shown in FIG. 4, a corner portion 23c having an arcuate cross section of the outer race 23 of the ball bearing BB protrudes into the cylindrical hole 35, and the inclined surface 30s of the push plug 30 is brought into contact with the corner 23c. The The coil spring 31 is accommodated in the push plug 30, and an outer end thereof projects outward from an opening end surface of the push plug 30. The spring set plate 32 is formed to be elongated in the radial direction of the crankshaft 6, and is bent inward with a base portion 32b having a bolt hole 33 opened, an intermediate portion 32n having a recess d for receiving a spring on the inner surface. The base 32b is bolted to the outer surface of the left crankcase half 10 by mounting bolts 38, and the spring receiving recess d of the intermediate portion 32n is formed as described above. The outer end of the coil spring 31 is received, and the free end 32f is formed to be narrower than the intermediate portion 32n, and is formed in a C shape in a side view (see FIG. 2) formed integrally with the left crankcase half. It is received in the hawk-like positioning portion 36 (see FIG. 5) to stop its rotation, that is, to be positioned.

  Thus, when assembling the “backlash absorbing means A” to the left crankcase half 10, the spring set plate 32 is loosely temporarily attached to the left crankcase half 10 with the mounting bolts 38, as shown in FIG. With the end of the free length coil spring 31 received by the spring receiving recess d of the intermediate portion 32n, the bent portion b of the free end 32f of the spring set plate 32 is connected to the fork-like positioning portion 36 of the left journal wall 10j. By engaging with, the rotation can be stopped and positioning can be performed, so that the operator does not have to perform troublesome operations such as compressing the coil spring 31 or pressing the spring set plate 32 by hand so as not to rotate. , "Backlash absorbing means A" can be assembled. When the mounting bolt 38 is tightened, as shown by the chain line in FIG. 8, the assembly of the “backlash absorbing means A” is completed, and in this assembled state, the boss portion 34 and the spring set of the left crankcase half 10 are completed. The concave portion d of the intermediate portion 32n of the plate 32 can be fitted to each other, whereby the “backlash absorbing means A” can be compactly accommodated on the outer surface of the crankcase 10 and partially protrudes to the outside. There is no place. As described above, since the “backlash absorbing means A” can be assembled from the outside of the left crankcase half 10, the assembling workability is very good.

  As shown in FIG. 4, in the assembled state of “backlash absorbing means A”, the spring set plate 32 presses the push plug 30 inward via the coil spring 31, and the ball is moved by the inclined surface 30 s of the push plug 30. The outer race 23 of the bearing BB is pressed with a pressing force F obliquely downward. The outer race 23 is pressed in the radial direction by the vertical component force Fr of the pressing force F, that is, the radial component force Fr of the crankshaft 6, and this pressing force causes a gap between the outer peripheral surface of the outer race 23 and the bearing hole 18. The radial play can be absorbed, that is, eliminated, and the crankshaft 6 can be accurately supported without play against the radial load of the crankshaft 6 caused by the explosive force applied to the piston 3. Generation of a hitting sound can be prevented in advance.

  Thus, the direction in which the pressing force exerted on the ball bearing BB by the “backlash absorbing means A” is made to substantially coincide with the direction in which the maximum pressure (explosion pressure) applied to the piston 3 acts. That is, in this internal combustion engine, since the position of the piston that receives the maximum explosion pressure is when the piston is slightly behind the top dead center, as shown in FIG. A direction along the cylinder axis LL at a position slightly deviated from the cylinder axis LL toward the rotation direction of the crankshaft 6 (arrow R direction in FIG. 2, counterclockwise) as viewed from the axial direction of the crankshaft 6 Thus, the direction of the pressing force exerted on the ball bearing BB by the “backlash absorbing means A” can be made substantially coincident with the direction of the maximum pressure that the crankshaft 6 receives from the piston 3, and the ball bearing BB Thus, the crankshaft 6 is accurately supported.

  By the way, as shown in FIG. 4, a component force Fs in the horizontal direction, that is, the axial direction of the crankshaft 6 is generated by the pressing force F applied to the outer race 23 by the push plug 30 of the “backlash absorbing means A”. The axial force of the outer race 23 is inevitably generated in the outer race 23 by the component force Fs, and this thrust force acts as a force for moving the outer race 23 of the ball bearing BB in the axial direction.

  Therefore, in this embodiment, the “movement restraining means S” described below can receive the thrust force and restrain the outer race 23 from moving in the axial direction.

  Next, the “movement restraining means S” will be described. This is a ball bearing BB in which a plurality of, in this embodiment, three movement restraining members 40 and a hook portion 40f of the movement restraining member 40 are loosely engaged. And an engaging groove 41 formed on the inner peripheral surface of the outer race 23. As shown in FIG. 7, the movement suppressing member 40 is formed in an elongated plate shape, and a hook portion 40f bent in a C-shaped cross section is integrally formed at the tip portion thereof. As shown in FIGS. 2 and 3, the three movement restraining members 40 are radially arranged on the outer side of the left crankcase half 10 at substantially equal intervals in the circumferential direction, and their outer ends are The ball bearing BB is fixed to the outer surface of the left crankcase half by a mounting bolt 43 on a concentric circle. The three movement restraining members 40 are oriented toward the center of the ball bearing BB, and hook portions 40f at the inner ends thereof are bent toward the inner surface of the outer race of the ball bearing BB, and are formed in engagement grooves 41 formed on the inner surface. Each is engaged. Between each hook part 40f and the engagement groove | channel 41, some slits are provided in those axial directions. The engagement between the hook portion 40f and the engagement groove 41 can suppress the axial movement of the outer race 23 of the ball bearing BB. As a result, the thrust force is received by the right ball bearing (see Patent Document 1). The roller bearing BR having a small diameter (compared to the ball bearing BB) can be adopted as the right rolling bearing as in this embodiment. As shown in FIGS. 2 and 3, the three movement suppressing members 40 are arranged at intervals in the circumferential direction of the ball bearing BB, thereby preventing the ball bearing BB from falling.

  Thus, the “movement restraining means S” includes a movement restraining member 40 fixed to the outer surface of the left crankcase half 10 and an engagement groove 41 formed on the inner peripheral surface of the outer race 23 of the ball bearing BB. Therefore, the structure is simple. When the left crankcase half 10 is mounted on the left crankcase half 10, the left crankcase half 10 need not be provided with a mounting shape such as a notch. There is no loss of strength. Further, since the “movement restraining means S” can be assembled from the outside of the left crankcase half 10, it is easy to assemble and requires special equipment and jigs for the assembly. do not do.

  As shown in FIGS. 1 and 2, a driving sprocket 51 for timing drive of the valve camshaft 50 is fixed to the outside of the ball bearing BB of the crankshaft 6, and this driving sprocket 51 is connected via an endless chain 52. The driven sprocket 53 is fixed to the valve camshaft 50 that is rotatably supported by the cylinder head CH. The rotation of the crankshaft 6 is transmitted to the valve camshaft 50 via the drive sprocket 51, the endless chain 52, and the driven sprocket 53. Below the crankshaft 6, a chain drop prevention plate 54 is fixed to the left crankcase half 10 by a plurality of bolts 55 for preventing the chain 52 from falling off. As shown in FIG. 2, the chain drop prevention plate 54 has an arcuate portion facing and close to the arcuate lower surface of the chain 52 suspended by the drive sprocket 51. Can be prevented from falling off.

  1 and 2, a flywheel 61 having an ACG outer rotor 60 fixed thereto is fixed to the left end portion of the crankshaft 6, and a gear group 62 linked to a mission, balancer, etc. is connected to the right end portion, and The centrifugal oil filter 63 is fixed.

  Next, the operation of this embodiment will be described.

  Now, when the internal combustion engine E is operated, the crankshaft 6 supported by the crankcase 6 via the ball bearing BB and the roller bearing BR is rotationally driven. At this time, the outer race 23 of the ball bearing BB, Radial “backlash” generated between the bearing holes 18 of the left crankcase half 10 can be absorbed by the “backlash absorbing means A”, and the occurrence of hitting sound due to the “backlash” can be prevented in advance. In addition, the crankshaft 6 can be accurately supported by the bearings BB and BR to ensure smooth and light rotation.

  Further, the axial movement of the outer race 23 of the ball bearing BB that is forced by the attachment of the “backlash absorbing means A” can be restrained by the “movement restraining means S”, so that the crankshaft 6 is supported. One of the pair of rolling bearings can be a roller bearing (smaller diameter and higher rigidity than the ball bearing), and the internal combustion engine E can be made compact.

  As mentioned above, although the Example of this invention was described, this invention is not limited to the Example, A various Example is possible within the scope of the present invention.

  For example, a roller bearing or other rolling bearing may be used instead of the left ball bearing, and a needle bearing or other rolling bearing may be used instead of the right roller bearing.

Longitudinal sectional side view of an internal combustion engine having a crankshaft bearing structure of the present invention Sectional view along line 2-2 in FIG. Enlarged cross-sectional view along line 3-3 in FIG. Sectional view along line 4-4 in FIG. Enlarged sectional view taken along line 5-5 in FIG. Push plug perspective view Perspective view of movement restraining member Operational diagram showing the state when the backlash absorbing means is assembled Diagram showing the process of assembling the crankshaft to the crankcase Operational diagram showing the state when assembling the conventional backlash absorbing means

Explanation of symbols

6 ... Crankshaft 10 ... Crankcase (left crankcase half)
18 .... Bearing hole 23 ... Outer race 30 ... Push plug 31 ... Spring member (coil spring)
32 ... Spring set plate 34 ... Boss part 36 ... Positioning part A ... Backlash absorbing means BB ... Rolling bearing (ball bearing)
b ... Bending part d ... Concave part

Claims (3)

  The crankshaft (6) is rotatably supported on the crankcase (10) via the rolling bearing (BB), and the backlash absorbing means (A) is provided between the outer race (23) of the rolling bearing (BB) and the crankcase (10). This backlash absorbing means (A) absorbs radial backlash generated between the outer race (23) of the rolling bearing (BB) and the bearing hole (18) of the crankcase (10). In the bearing structure of the crankshaft in the internal combustion engine, the backlash absorbing means (A) is movably provided in the crankcase (10), and the outer race (23) of the rolling bearing (BB) is attached to the crankshaft (6). Push plug (30) for pressing in the radial direction, spring set plate (32) bolted to the crankcase (10), and push plug 30) and a spring member (31) interposed between the spring set plate (32) and elastically urging the push plug (30) toward the outer race (23), and the spring set plate (32) includes: The bent portion (b) is bent toward the crankcase (10). The bent portion (b) has the spring member (31) in a free length state and the spring set plate (32) is temporarily fixed. A crankshaft bearing structure in an internal combustion engine characterized by being engaged with a positioning portion (36) formed in a crankcase (10) when in a state.   The crankcase (10) is integrally formed with a boss portion (34) protruding from the outer surface thereof, and the push plug (30) is movably provided on the boss portion (34), while the spring set plate ( 32) is formed with a recess (d) that faces the boss portion (34) and receives the free end of the spring member (31), and the spring set plate (32) is completely assembled. The bearing structure for a crankshaft in an internal combustion engine according to claim 1, wherein the boss portion (34) and the concave portion (d) are fitted to each other. The positioning portion (36) formed on the crankcase (10) is formed in a fork shape that is open to the outer surface so that the spring set plate (32) can be received from the outside of the crankcase (10). 3. A bearing structure for a crankshaft in an internal combustion engine according to claim 1, wherein the bearing structure is a crankshaft.

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