JP4932682B2 - Piston for internal combustion engine - Google Patents

Description

  The present invention relates to a piston used in an internal combustion engine.

A piston for an internal combustion engine has a pair of piston piston skirts extending from an outer peripheral portion of a piston top portion whose top surface faces the combustion chamber to be in sliding contact with a cylinder inner wall, and supporting both ends of the piston pin from the back surface of the piston top portion. The pin boss protrudes.
The connecting rod is connected between the piston pin of the piston and the crank pin of the crankshaft, and the reciprocating motion in the piston cylinder is converted into the rotation of the crankshaft. Therefore, a large amount of force is applied to the pin boss that supports the piston pin of the piston. Join.

  Therefore, the pair of pin bosses that protrude from the back surface of the piston top part are reinforced by a pair of vertical ribs that extend to both sides of each pin boss substantially perpendicular to the central axis of the pin support hole of the pin boss and are connected to the piston skirt. .

  The piston disclosed in Patent Document 1 is further formed with a pair of horizontal ribs connecting between the pair of vertical ribs, and the vertical ribs are reinforced to withstand the force acting on the vertical ribs from the piston skirt. .

JP 2001-289117 A

  Since the horizontal ribs connect the pair of vertical ribs, the mutual deformation of the pair of vertical ribs due to the force acting on the vertical ribs from the piston skirt can be suppressed. There are places where it is difficult to withstand the force of deformation.

  The present invention has been made in view of the above points, and the object of the present invention is to sufficiently withstand all the forces acting on the longitudinal ribs that reinforce the pin boss with a simple structure, and to ensure sufficient strength and rigidity of the entire piston. It is the point which provides the piston for internal combustion engines which can do.

In order to achieve the above object, the invention according to claim 1 is characterized in that a pair of pin bosses (34, 34) supporting both ends of the piston pin (38) are formed to protrude from the back surface of the piston top (31), A pair of vertical ribs (35, 35) substantially perpendicular to the central axis of the pin support holes (34h, 34h) of the pin boss (34, 34) are formed on the back surface of the piston top (31). ) Extending from both sides to each other and connected to the piston skirt (33), and the pin support hole (34h) connecting the pair of vertical ribs (35, 35) to the back surface of the piston top (31). , 34h) is a pair of lateral ribs (36, 36) parallel to the central axis (Lp) of the piston for the internal combustion engine formed on both sides of the piston pin (38), on the back surface of the piston top (31). A pair of laterally extending ribs (37) extending from each of the pair of lateral ribs (36,36) connecting between the pair of longitudinal ribs (35,35) to both outer sides between the longitudinal ribs (35,35). , 37) Is formed by connecting the same piston wall extending piston to wall (32) (32), extending on both sides from the opposite respective inner portions of the pair of longitudinal ribs (35, 35) said pair of pin bosses (34, 34) is formed out, was the longitudinal ribs (35, 35) and a piston for an internal combustion engine, characterized in that the by transverse ribs (36, 36) and the transverse extension rib (37, 37) is parallel crosses shape is configured .

  According to a second aspect of the present invention, in the piston for an internal combustion engine according to the first aspect, the lower ends of the lateral ribs (36, 36) and the lateral extension ribs (37, 37) are pins of the pin boss (34, 34). It is located above the lowest end (Lv) of the support hole (34h, 34h), and the oil is injected obliquely from the lower side of the piston (30) toward the back surface of the piston top (31) by the piston jet. And

  According to a third aspect of the present invention, in the piston for an internal combustion engine according to the second aspect, the pair of laterally extending ribs (37, 37) is spaced from the pin boss (34, 34) on the side of the longitudinal rib (35, 35). The pin boss (34, 34) is sandwiched from both sides substantially equal to the outer diameter of the pin boss (34, 34), and the distance on the piston peripheral wall (32) side is smaller than the outer diameter of the pin boss (34, 34).

According to a fourth aspect of the present invention, in the piston for an internal combustion engine according to any one of the first to third aspects, the laterally extending ribs (37, 37) are formed from the back surface of the piston top (31). The protruding amount is formed so as to gradually decrease from the longitudinal rib (35, 35) side toward the piston outer peripheral side.

  According to the piston for the internal combustion engine according to claim 1, the pair of lateral ribs are connected between the pair of longitudinal ribs that extend from both sides of the pair of pin bosses on the back surface of the piston top portion and are coupled to the piston skirt. Since a pair of laterally extending ribs, each of which is further extended to both sides, are connected to the piston peripheral wall, the longitudinal ribs, the lateral ribs and the laterally extending ribs are formed in a cross beam shape on the back surface of the piston top. .

Therefore, not only the relative deformation of the pair of vertical ribs by the force acting from the piston skirt on the pair of vertical ribs that reinforce the pair of pin bosses, but also an integral deformation is easy to add the lateral extension rib to the horizontal rib. It can be suppressed by the configuration, and sufficient strength and rigidity of the entire piston can be ensured while structurally reducing the weight of the piston.
Since a pair of vertical ribs are formed extending from opposite inner portions of the pair of pin bosses to both sides, the force acting on the piston pin installed between the pair of pin bosses via the connecting rod is applied to the inner portion of the pin boss. It is possible to effectively disperse in the vertical ribs connected to the thin film, and it is possible to ensure the necessary strength while reducing the weight with thin vertical ribs.

According to the piston for an internal combustion engine according to claim 2, the lower end of the lateral rib is located above the lowermost end of the pin support hole of the pin boss, and oil flows from the lower side of the piston toward the back surface of the piston top by the piston jet. Since it is injected obliquely, the lateral ribs provided on both sides of the pin boss have a small amount of protrusion from the back surface of the piston top, and the oil injected from the piston jet easily gets over the lateral rib and the piston pin installed between the pin bosses It reaches the sliding part and can be sufficiently lubricated.
Further, since the laterally extending rib also has a small amount of protrusion, the oil jetted from the piston jet reaches the entire back surface of the piston top and can cool the piston efficiently.

According to the piston for an internal combustion engine according to claim 3, since the distance between the pair of laterally extending ribs on the longitudinal rib side is substantially equal to the outer diameter of the pin boss, the laterally extending ribs are arranged to extend the lateral ribs. Since the distance between the pair of lateral ribs is substantially equal to the outer diameter of the pin boss, both ends of the pin boss are supported by the pin support holes of the pin boss, and the oil injected from the piston jet slides on the piston pin. Can easily reach the part and lubricate well.
In addition, since the distance between the pair of laterally extending ribs on the piston peripheral wall side is smaller than the outer diameter of the pin boss, the portions of the longitudinal ribs and the laterally extending ribs that are connected to the piston skirt and the piston peripheral wall are evenly positioned in the circumferential direction. The rigidity of the whole piston can be increased.

According to the piston for the internal combustion engine according to claim 4 , the laterally extending rib is formed so that the protruding amount from the back surface of the piston top portion gradually decreases from the longitudinal rib side toward the piston peripheral wall side. Forming becomes easy, and concentration of meat during forging can be prevented particularly when forging.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
The internal combustion engine E according to the present embodiment is mounted on a motorcycle with a transmission M integrally provided behind the internal combustion engine E.
In the present embodiment, the front, rear, left and right coincide with the front, rear, left and right when the vehicle is used as a reference.

Referring to FIG. 1 which is a partially omitted side view of a motorcycle and FIG. 2 which is a plan view thereof, a main frame which is divided into two forks from a head pipe 2 of a vehicle body frame 1 and extends obliquely downward to the rear. 3 pivots the rear part downward to form a pivot plate 3p, and a pivot 4a and a pivot plate 3p at the lower end of a bracket 3b suspended from a position near the head pipe 2 from the center of the pair of left and right main frames 3 The internal combustion engine E is suspended from the main frame 3 by supporting the mounting brackets 11a, 11b, 11c of the crankcase 11 by the three supporting shafts 4a, 4b, 4c of the upper and lower support shafts 4b, 4c.
A rear fork 6 that supports a rear wheel (not shown) is pivotally supported at a front end so as to be swingable on a pivot shaft 5 installed at a center height position of the pair of left and right pivot plates 3p.

  The internal combustion engine E is a water-cooled single-cylinder four-stroke internal combustion engine. Referring to FIG. 3, the crankcase 11 that supports the crankshaft 20 in the left-right direction, which is also the vehicle width direction of the vehicle, A crank chamber Cc in which the shaft 20 is disposed is formed, and a mission chamber Cm that is partitioned by a vertical partition wall 11m and accommodates the transmission M is formed at the rear of the crank chamber Cc, and below the crank chamber Cc. An oil pan chamber Co that stores oil by being partitioned by a substantially horizontal partition wall 11o is integrally formed.

  The single-cylinder four-stroke internal combustion engine E includes a cylinder block 12 having one cylinder 12a on the crank chamber Cc of the crankcase 11, and a cylinder coupled to the upper portion of the cylinder block 12 by a head bolt via a gasket. An engine body including a head 13 and a cylinder head cover 14 coupled to the upper part of the cylinder head 13 is provided.

The cylinder block 12, the cylinder head 13, and the cylinder head cover 14 stacked on the crankcase 11 extend upward from the crankcase 11 in a slightly tilted posture.
Thus, the upper half of the crankcase 11 of the internal combustion engine E in which the cylinder is tilted backward is the crank chamber Cc, and the latter half is the mission chamber Cm.
The oil pan chamber Co below the crank chamber Cc is a chamber inside the oil pan 15 that extends downward from the crankcase 11 and is integrally formed.

  The internal combustion engine E supported by the main frame 3 is suspended below the main frame 3 between the bracket 3b and the pivot plate 3p, and is inclined upward from the lower crankcase 11 and extends upward. , Of the cylinder head 13 and the cylinder head cover 14, the cylinder head 13 and the cylinder head cover 14 are located between the pair of left and right main frames 3, 3.

  In the transmission chamber Cm of the crankcase 11, a main shaft 21 and a counter shaft 22 of the transmission M are disposed in parallel to the crank shaft 20 so as to be directed in the horizontal direction. An output shaft is formed by penetrating leftward and projecting outside, and a drive chain sprocket 23 is fitted to the projecting left end.

  The counter shaft 22 is located near the front of the pivot shaft 5 that supports the rear fork 6, and a drive chain 24 wound around a drive chain sprocket 23 fitted to the counter shaft 22 is provided at the rear end of the rear fork 6. A chain transmission mechanism is constructed over a driven chain sprocket (not shown), and power is transmitted to the rear wheel side.

The cylinder head 13 has an intake passage 16i that is an extension of the intake port 13i obliquely upward from the front surface, and a throttle body 17 is connected between the pair of left and right main frames 3, 3 to the intake passage 16i. The upstream side of 17 intake passages is open.
An exhaust passage 16e, which is an extension of the exhaust port 13e, extends rearward substantially horizontally from the rear surface of the cylinder head 13 tilted slightly rearward, and an exhaust pipe 18 is connected to the left and right main frames 3 in the exhaust passage 16e. , 3 are connected.

  The connection outlet of the exhaust passage 17 is located on the right side of the vehicle body, and as shown in FIG. 2, the upstream connection end 18a of the exhaust pipe 18 is connected to the exhaust passage 16e on the right side of the center axis Lb in the left-right direction of the vehicle body. Has been.

  The exhaust pipe 18 connected to the exhaust passage 17 on the rear surface of the cylinder head 13 tilted backward in this manner and extending rearward substantially horizontally extends in the transmission chamber Cm in which the transmission M in the rear half of the crankcase 11 is accommodated. The upper space curves to the left and turns downward while gradually descending, passes under the left main frame 3 and extends obliquely forward and downward along the left side of the cylinder block 12 of the internal combustion engine E. When it reaches the lower end of the crankcase 11 (the lower end of the oil pan 15) after reaching the front of the case 11 and suddenly downwards, the lower end of the oil pan 15 is moved backward at the approximate center in the left-right direction of the vehicle body. It is connected to the muffler 19 (see FIGS. 1 and 2).

  The lower surface of the crankcase 11 is at the lowest position with the front part of the oil pan 15 projecting downward, forming an inclined surface that rises toward the rear, and is generally horizontal below the rear mission chamber 11, A muffler 19 connected to the pipe 18 extends rearward along the lower surface of the crankcase 11.

The vehicle body frame 1 is entirely covered with a vehicle body cover in which synthetic resin cover members divided into respective parts are connected. In particular, the left and right sides of the internal combustion engine E are covered with a body cover 7.
The body cover 7 covers the lower part of the internal combustion engine E so as to be along the lower surface of the muffler 19.

  Referring to FIG. 4, the crankcase 11 coupled to the lower part of the cylinder block 12 is a left crankcase that is a pair of cases divided into left and right by a plane that includes the cylinder axis Lc and is orthogonal to the crankshaft 20. 11L and the right crankcase 11R are configured to be coupled by bolts with their mating surfaces aligned.

A crankshaft 20 rotatably supported in a left and right direction in a crank chamber Cc formed by combining left and right crankcases 11L and 11R is moved left and right from left and right crank webs 20w and 20w connected by crank pins 20p. The shaft bodies 20L and 20R are integrally molded in a shape extending coaxially.
The left and right shaft bodies 20L and 20R of the crankshaft 20 are adjacent to the crank webs 20w and 20w, which are journal portions 20Lj and 20Rj.

The space between the main bearing portions 11Lb and 11Rb of the left and right crankcases 11L and 11R is the crank chamber Cc, and the left and right crank webs 20w and 20w are accommodated. The left and right journal portions 20Lj and 20Rj respectively hold the metal bearings 25 and 25. Via the main bearings 11Lb and 11Rb.
The lower part of the cylinder 12a of the cylinder block 12 is fitted into a circular opening formed above the crank chamber Cc by combining the left and right crankcases 11L and 11R, and the piston 30 is fitted in the cylinder bore 12b of the cylinder 12a so as to be slidable back and forth. Combined.

  A piston pin 38 is installed between a pair of pin bosses 34, 34 projecting from the back surface of the piston top 31 of the piston 30, and a small end is pivotally supported by the piston pin 38, and a large end is connected to the crankpin 20 p of the crankshaft 20. The piston 30 and the crankshaft 20 are connected by a connecting rod 39 that is pivotally supported via a large end metal 39a to form a crank mechanism.

  The left crankcase 11L is formed with a chain chamber Ccc on the left side of the left main bearing portion 11Lb, and the left shaft body 20L protruding to the left from the left main bearing portion 11Lb of the crankshaft 20 penetrates the chain chamber Ccc and further to the left An oil pump drive sprocket 20os and a drive cam chain sprocket 20cs are formed in the portion corresponding to the chain chamber Ccc through the opening on the left side wall of the crankcase 11L, and the outer rotor 26r of the AC generator 26 is fitted to the left end. Has been.

An inner stator 26s around which a coil of the AC generator 26 is wound is fixed to a left side cover 40 that closes the opening of the crank chamber Cc and the oil pan 15 on the left side wall of the left crankcase 11L. An AC generator 26 in which the outer rotor 26r that holds the motor rotates is configured.
The left side cover 40 has a bowl shape, and a cylindrical portion 41 protruding from the center of the bottom surface is put on the left end portion of the crankshaft 20, and the stator core of the inner stator 26s is fixed to the cylindrical portion 41 by a bolt 26b. The

  On the other hand, the balancer drive gear 27a and the main drive gear 28a are fitted to the right shaft body 20R that protrudes to the right from the right main bearing portion 11Rb of the right crankcase 11R in the crankshaft 20 from the vicinity of the main bearing portion 11Rb. It is fixed by a flange bolt 29 via 29w (see FIG. 4).

  The balancer drive gear 27a meshes with a balancer driven gear (not shown) provided at the right shaft end of the front balancer shaft 55 (see FIG. 3), and is rotationally driven in the reverse direction at a constant speed with the crankshaft 20. The primary vibration generated by the reciprocating motion of the piston 30 is reduced.

  The transmission M disposed in the transmission chamber Cm behind the crank chamber Cc has a shift operated by the main shaft 21 and the counter shaft 22 provided with a main gear group 21g and a counter gear group 22g, respectively, and a shift operation mechanism. And a gear change mechanism 52 having a drum 53 and shift forks 54a, 54b, 54c (see FIG. 3).

The main shaft 21 is located at substantially the same vertical position as the crankshaft 20, is rotatably supported by the left and right crankcases 11L and 11R via bearings 21b and 21b, and is provided at a portion protruding rightward from the right bearing 21b. A plate friction type transmission clutch 50 is arranged, and a primary driven gear 28b provided in the transmission clutch 50 meshes with the main drive gear 28a to constitute a primary reduction mechanism.
The transmission clutch 50 includes a large number of clutch plates 50p, and is operated by a clutch operation mechanism to transmit and shut off the power of the crankshaft 20 to the transmission M.

  The counter shaft 22 is positioned obliquely above and behind the main shaft 21, is rotatably supported by the left and right crankcases 11L and 11R via bearings 22b and 22b, and is arranged at the left end protruding outward from the left bearing 22b. A chain drive sprocket 23 is fitted.

  Accordingly, the power of the internal combustion engine E is transmitted from the crankshaft 20 to the transmission M via the primary reduction mechanisms 28a and 28b and the clutch 45, and in the meshing of the main gear group 21g and the counter gear group 22g of the transmission M. The shifted output is transmitted from the counter shaft 22 to a chain driven sprocket (not shown) via a chain transmission mechanism, and further to a rear wheel via a secondary reduction mechanism (not shown).

A right side cover 45 is placed on the right side surface of the right crankcase 11R on the sides of the crank chamber Cc and the transmission chamber Cm excluding the oil pan 15.
The right side cover 45 has a cylindrical portion 45a that covers the periphery of the transmission clutch 50, a circular opening 45b is formed at an axial position of the crankshaft 20, and a pump body 45c of the water pump 56 above the circular opening 45b. The opening of the cylindrical portion 45a is covered with a clutch cover 46, the circular opening 45b is fitted with a lid member 47, and the water pump body 45c is covered with a water pump cover 48.

  The internal combustion engine E includes a DOHC type valve mechanism, and referring to FIGS. 3 and 4, the cylinder head 13 corresponds to the cylinder 12 a and faces the piston 30 in the cylinder axial direction in the combustion chamber 60. The combustion chamber 60 has a pair of intake ports 13i that open to the left and right of the front half, and a pair of exhaust ports 13e that open to the left and right of the rear half of the combustion chamber 60. 61 is attached with the tip facing the combustion chamber 60.

  An intake valve 62 and an exhaust valve 63, which are slidably supported by valve guides 64i and 64e integrally fitted to the cylinder head 3, are driven by a valve operating device 65 provided in the internal combustion engine E, and are thus connected to an intake port. The intake opening of 13i and the exhaust opening of the exhaust port 27 are opened and closed in synchronization with the rotation of the crankshaft 20.

  The valve operating device 65 is provided in a valve operating chamber 14v formed by the cylinder head 13 and the cylinder head cover 14, and is an intake camshaft 66 disposed in the left-right direction above the pair of left and right intake valves 62. An exhaust camshaft 67 disposed on the left and right pair of exhaust valves 63 so as to be directed in the left-right direction is rotatably supported so as to be sandwiched between the cylinder head 13 and the cam holders 68i and 68e.

  The cam lobe 66c of the intake camshaft 66 is in contact with the upper surface of the valve lifter 62l that covers the upper end of the intake valve 62 biased upward by the valve spring 62s, and the intake valve 62 is rotated by the rotation of the cam lobe 66c integrated with the intake camshaft 66. Similarly, the cam lobe 67c of the exhaust camshaft 67 is in contact with the upper surface of the valve lifter 63l that covers the upper end of the exhaust valve 63 biased upward by the valve spring 63s, and is integrated with the exhaust camshaft 67. The exhaust valve 63 is opened / closed at a required timing by the rotation of the cam lobe 67c.

  The intake camshaft 66 and the exhaust camshaft 67 are fitted with driven cam chain sprockets 66s and 67s at their left shaft ends, respectively, and the left shaft body of the two driven cam chain sprockets 66s and 67s and the crankshaft 20 A cam chain 69 is bridged between the drive cam chain sprocket 20cs formed in 20L (see FIG. 6), and the rotational power of the crankshaft 20 is passed between the intake camshaft 66 and the exhaust camshaft 67 via the cam chain 69. The rotation is transmitted, and the intake cam shaft 66 and the exhaust cam shaft 67 rotate in synchronization with the crankshaft 20, and the intake valve 62 and the exhaust valve 63 are driven to open and close.

  Piston jet oil passages J1 and J2 are formed in the right main bearing portion 11Rb and the left main bearing portion 11Lb of the crankcase 11 that supports the crankshaft 20 of the internal combustion engine E, respectively. Oil is injected obliquely upward into the cylinder bore 12b by the jet nozzles N1 and N2 provided at the downstream ends of the paths J1 and J2 (see FIGS. 3 and 4), and the piston 30 reciprocally slides in the cylinder bore 12b. It is possible to cool the piston 30 from the back surface by slanting it against the back surface.

The structure of the piston 30 to which the oil is injected will be described in detail below with reference to FIGS.
The piston 30 is formed by forging, and a piston peripheral wall 32 having a flat cylindrical shape extends slightly from the outer peripheral portion of the piston top portion 31, and a piston that forms a pair of front and rear from the front and rear portions of the piston peripheral wall 32 facing each other. Skirts 33, 33 are further formed to extend downward, and the pair of left and right pin bosses 34, 34 project downward from the back surface 31b of the piston top 31.
The pin bosses 34, 34 protrude downward from the piston skirts 33, 33.

The top surface of the piston top portion 31 is formed with intake valve recesses 31i, 31i that are slightly recessed behind the front half to escape the intake valves 62, 62 on the left and right sides. Some exhaust valve recesses 31e, 31e are formed.
A piston ring groove 32 a is formed on the outer peripheral surface of the piston peripheral wall 32.

  Referring mainly to FIG. 6, a pair of left and right vertical ribs that are substantially perpendicular to the central axis of pin support hole 34h of pin bosses 34, 34 (hereinafter referred to as pin hole central axis Lp) on back surface 31b of piston top 31 35 and 35 are formed to extend from the respective inner portions of the pair of left and right pin bosses 34 and 34 to the front and rear sides and to be connected to the piston skirts 33 and 33.

A pair of front and rear horizontal ribs 36 and 36 connecting the pair of left and right vertical ribs 35 and 35 are formed in parallel to the pin hole central axis Lp on both front and rear sides of the piston pin 38 installed on the pair of left and right pin bosses 34 and 34. Has been.
The front and rear lateral ribs 36, 36 are formed so that their distance from each other is somewhat separated from the outer diameter of the pin boss 34, and the lower ends of the lateral ribs 36, 36 are located above the lowest end Lv of the pin support hole 34h. (See FIGS. 9 and 10).

  The piston 30 has a laterally extending rib 37 that extends further from the lateral ribs 36, 36 connecting the pair of longitudinal ribs 35, 35 to the back surface 31b of the piston top 31 and extends outwardly between the longitudinal ribs 35, 35. , 37 extend to the piston peripheral wall 32 and are connected to the piston peripheral wall 32.

As shown in FIG. 9, the laterally extending rib 37 is formed such that the amount of protrusion from the back surface 31b of the piston top 31 gradually decreases from the longitudinal rib 35 side (pin boss 34 side) toward the piston peripheral wall 32 side. Therefore, the concentration of meat during forging can be prevented, and forging is facilitated.
The lowermost end of the laterally extending rib 37 is substantially the same as the lowermost end of the lateral rib 36 and is substantially at the same height as the pin hole central axis Lp of the pin support hole 34h (see FIG. 9).

  In this way, the piston 30 has the longitudinal ribs 35, 35, the lateral ribs 36, 36 and the laterally extending ribs 37, 37 formed in a cross beam shape as a whole on the back surface 31b of the piston top portion 31, and the inside of the piston peripheral wall 32 has a cross beam shape. It is divided into nine compartments.

Since the piston 30 reciprocally sliding in the piston bore 12b of the cylinder 12a is connected to the connecting rod 39 via the piston pin 38, a force that rotates (swings) about the piston pin 38 acts. The piston skirts 33 and 33 suppress the swing.
That is, force is applied to the piston skirts 33, 33 from the inner peripheral surface of the cylinder 12a, and a pair of vertical ribs 35, 35 that connect the piston skirts 33, 33 are supported by this force.

  Therefore, force is applied from the piston skirts 33, 33 to the pair of longitudinal ribs 35, 35 that reinforce the pair of pin bosses 34, 34, but the lateral ribs 36, 36 are connected between the pair of longitudinal ribs 35, 35. Therefore, the relative deformation of the pair of vertical ribs 35, 35 is suppressed, and the laterally extending ribs 37, 37 extend to both sides of the lateral rib 36 and are connected to the piston peripheral wall. , 35 is also suppressed.

  The ribs 37, 37 are simply added to the horizontal rib 36, and ribs are formed on the back surface 31b of the piston top 31 in a cross-beam shape. Strength and rigidity can be ensured.

  Between the lateral ribs 36, 36, the small diameter end of the connecting rod 39 is set to be larger than the outer diameter of the pin boss 34. Therefore, the sliding of the piston pin whose both ends are supported by the pin support holes 34h of the pin boss 34 The oil injected from the piston jet easily reaches the part and can be sufficiently lubricated.

  Further, the opposing laterally extending ribs 37, 37 as extensions of the lateral ribs 36, 36 have a distance on the longitudinal rib 35 side substantially equal to the outer diameter of the pin boss 34, but an interval on the piston peripheral wall 32 side is the pin boss 34. Since the outer rib is formed smaller than the outer diameter of the piston ribs 33 and 33 and the piston ribs 33 and 33 and the piston peripheral wall 32 are located evenly in the circumferential direction, further increasing the rigidity of the entire piston. ing.

  As described above, as shown in FIGS. 3 and 4, the piston 30 in which the cross-shaped ribs are formed on the back surface 31 b of the piston top 31 is formed on the right main bearing 11 Rb and the left main bearing 11 Lb of the crankcase 11. The jet nozzles N1 and N2 are provided to inject oil obliquely from below toward the piston top back surface 31b.

  The lower ends of the horizontal ribs 36, 36 connecting the vertical ribs 35, 35 are located above the lowermost end Lv of the pin support hole 34h and have a small protruding amount, so that they are jetted obliquely upward from below by the jet nozzles N1, N2. The oil passes over the lateral ribs 36 and 36 by the reciprocating motion of the piston 30 and reaches both the central compartment and the front and rear compartments, particularly the central compartment between the pin bosses 34 and 34 on which the piston pin 38 is installed. Is sufficiently injected with oil to sufficiently lubricate the sliding portion of the piston pin 38.

  Since the lateral extension rib 37 has a small projecting amount in the same manner as the lateral rib 36, the oil jetted obliquely from the two jet nozzles N1, N2 toward the piston top back surface 31b reaches the left and right three compartments, and the piston The piston can be efficiently cooled by reaching the entire top rear surface 31b.

  Further, the piston 30 extends from both inner portions of the pair of pin bosses 34, 34 facing each other to form a pair of vertical ribs 35, 35, and is thus constructed between the pair of pin bosses 34, 34. The force acting on the piston pin 38 via the connecting rod 39 can be effectively distributed to the longitudinal ribs 35, 35 connected to the inner portions of the pin bosses 34, 34, and the thin longitudinal ribs 35, 35 reduce the weight. Necessary strength can be ensured while planning.

  The central compartment into which the piston pin 38 on the back surface 31b of the piston top 31 is installed and the small end of the connecting rod 39 is inserted forms a large recess, but the piston top corresponding to the large bottom wall of this center recess The top surface of 31 is provided with a protrusion 31r formed between the intake valve recesses 31i, 31i and the exhaust valve recesses 31e, 31e, and this protrusion 31r acts as a reinforcing rib to ensure strength and rigidity. .

1 is a partial side view of a motorcycle on which an internal combustion engine according to an embodiment of the present invention is partially omitted. It is the same top view. It is a sectional side view of this internal combustion engine. It is the IV-IV sectional view taken on the line in FIG. It is a top view of this piston. It is the same bottom view. It is a VII arrow line view in FIG. FIG. 6 is a view taken along arrow VIII in FIG. 5. It is the IX-IX sectional view taken on the line in FIG. FIG. 6 is a sectional view taken along line XX in FIG. 5.

Explanation of symbols

E ... Internal combustion engine, M ... Transmission,
11 ... Crank case, Cc ... Crank chamber, Cm ... Mission chamber, Co ... Oil pan chamber, 11L ... Left crank case, 11R ... Right crank case, 11Lb, 11Rb ... Main bearing, 12 ... Cylinder block, 12a ... Cylinder, 13 ... Cylinder head, 14 ... Cylinder head cover, 15 ... Oil pan, 20 ... Crankshaft, 20p ... Crank pin, 20Lj, 20Rj ... Journal part,
J1, J2 ... piston jet oil passage, N1, N2 ... jet nozzle,
30 ... Piston, 31 ... Piston top, 32 ... Piston peripheral wall, 33 ... Piston skirt, 34 ... Pin boss, 35 ... Vertical rib, 36 ... Horizontal rib, 37 ... Horizontal extension rib, 38 ... Piston pin, 39 ... Connecting rod, 39a ... Big end metal,
60 ... combustion chamber, 62 ... intake valve, 63 ... exhaust valve, 65 ... valve drive.

Claims (4)

A pair of pin bosses (34, 34) that support both ends of the piston pin (38) are formed to protrude from the back surface of the piston top (31),
A pair of vertical ribs (35, 35) substantially perpendicular to the central axis of the pin support holes (34h, 34h) of the pin boss (34, 34) are formed on the back surface of the piston top (31). 34) extending from each side and connected to the piston skirt (33),
A pair of lateral ribs (36, 36) parallel to the central axis (Lp) of the pin support holes (34h, 34h) connecting the pair of longitudinal ribs (35, 35) to the back surface of the piston top (31). In the piston for the internal combustion engine formed on both sides of the piston pin (38),
The pair of lateral ribs (36, 36) connecting the pair of longitudinal ribs (35, 35) to the back surface of the piston top (31) is further extended to both outer sides between the longitudinal ribs (35, 35). A pair of laterally extending ribs (37, 37) extending to the piston peripheral wall (32) and connected to the piston peripheral wall (32),
The pair of vertical ribs (35, 35) are formed to extend from both inner portions facing the pair of pin bosses (34, 34) to both sides,
A piston for an internal combustion engine, wherein the vertical ribs (35, 35), the horizontal ribs (36, 36), and the horizontal extension ribs (37, 37) form a cross beam shape. The lower ends of the lateral ribs (36, 36) and the laterally extending ribs (37, 37) are located above the lowest end (Lv) of the pin support holes (34h, 34h) of the pin bosses (34, 34),
2. A piston for an internal combustion engine according to claim 1, wherein oil is injected obliquely from below the piston (30) toward the back surface of the piston top (31) by the piston jet.   The pair of laterally extending ribs (37, 37) has an interval on the vertical rib (35, 35) side substantially equal to the outer diameter of the pin boss (34, 34), and sandwiches the pin boss (34, 34) from both sides. 3. The piston for an internal combustion engine according to claim 2, wherein a distance on the piston peripheral wall (32) side is formed smaller than an outer diameter of the pin boss (34, 34). The laterally extending ribs (37, 37) are formed such that the amount of protrusion from the back surface of the piston top (31) gradually decreases from the longitudinal rib (35, 35) side toward the piston outer peripheral side. The piston for an internal combustion engine according to any one of claims 1 to 3, wherein:

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