JP2006226442A - Assembly of piston and connecting rod - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a piston and a connecting rod to be assembled to each other in a regular positional relationship to prevent wrong assembly thereof. <P>SOLUTION: This assembly of the piston and the connecting rod is composed of: the piston 14 having a piston body 42 with piston ring grooves 41 formed on its circumferential surface and boss parts 45 and 46 for respectively fitting ends of a piston pin 16 thereto; and the connecting rod 15 having a piston-side connection part 48 with a pin insertion hole 48a formed therein; and the piston 14 is attached to the connecting rod 15 by the piston pin 16. A recessed part 51 is formed on the piston-side connection part 48 of the connecting rod 15; and the piston body 42 is provided with a projecting part 52 entering into the recessed part 51 in an assembled form of the piston 14 with the connecting rod 15. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an assembly of a piston and a connecting rod designed to improve assemblability, and more particularly to a piston and connecting rod assembly for a general-purpose engine having a connecting rod provided with a scraper.

  The engine has a crankcase that rotatably supports the crankshaft, and a cylinder in which a piston is reciprocally incorporated. The piston and the crankshaft are connected by a connecting rod, and the reciprocating motion of the piston is cranked through the connecting rod. It is transmitted to the rotational movement of the shaft. As described in Patent Document 1, a piston pin attached to a piston is assembled in a pin insertion hole provided in a piston side connecting portion at one end of a connecting rod, and a crankshaft side connecting portion at the other end is attached to a pin insertion hole. The crankshaft crankpin can be assembled. The boss hole formed in the piston and into which the piston pin is fitted is formed to be shifted from the radial center of the piston by a predetermined offset amount. Further, a scraper for scraping up lubricating oil, that is, engine oil accommodated in the crankcase is provided at the other end portion of the connecting rod of the general-purpose engine or the like, that is, the crankshaft side connecting portion.

  Therefore, when assembling the piston and the connecting rod, the piston pin is arranged so that the orientation of the front and back of the connecting rod is a predetermined direction with respect to the piston when viewed from the direction along the boss hole. It is necessary to fit into the boss hole and the pin insertion hole of the connecting rod.

  If the connecting rod is reversed and assembled to the piston, the engine will not be able to achieve the desired performance, and the recess or recess formed on the upper surface of the piston corresponding to the intake / exhaust valve will be the normal position. When the valve is opened, the intake / exhaust valve comes into contact with the top surface of the piston, which hinders engine operation and cannot be shipped as a product. The engine assembled in this way is removed in the inspection process, and the production efficiency of engine assembly production is reduced.

In order to detect whether or not the piston is erroneously assembled to the cylinder block, an erroneous assembly detection device for the piston has been developed as described in Patent Document 2.
Japanese Patent Laid-Open No. 10-196785 JP 2001-296209 A

  As described in Patent Document 1, the piston body is provided with a boss portion into which one end portion of the piston pin is fitted and a boss portion into which the other end portion is fitted. A boss hole is formed, and an accommodation space is formed between the boss portions into which the piston side connecting portion of the connecting rod enters. The piston connecting part of the conventional connecting rod has almost the same shape at both ends of the pin insertion hole. When assembling the connecting rod to the piston, the connecting side of the connecting rod faces the piston side. Even if the portion is inserted into the housing space, the connecting rod and the piston can be connected using the piston pin.

  Therefore, when assembling the piston and connecting rod, when manually setting the piston pin and connecting rod against the device that inserts the piston pin into the boss hole of the piston and the pin insertion hole of the connecting rod, Even if the direction of the connecting rod and the connecting rod are reversed, the operator may not notice it. The connecting rod assembled to the piston has an asymmetrical crankshaft end, so the operator can easily determine which side to assemble and set it on the device, The piston is substantially symmetrical when viewed from either end side of the piston pin hole, and it is not easy to determine the orientation of the piston during assembly, and there is a risk of erroneous assembly.

  An object of the present invention is to enable the piston and the connecting rod to be assembled in a normal positional relationship, and to prevent the occurrence of erroneous assembly.

  An assembly of a piston and a connecting rod according to the present invention includes a piston main body having a piston ring groove formed on an outer peripheral surface thereof, and a boss part integrally provided in the piston main body and fitted to both ends of the piston pin. A piston-connecting rod assembly having a piston-side connecting portion in which a pin insertion hole is formed and a connecting rod connected to the piston by passing the piston pin through the pin insertion hole, A rod-side uneven portion is provided at the piston-side connecting portion of the connecting rod, and a piston-side uneven portion that enters the rod-side uneven portion under the assembled state of the piston body and the connecting rod is formed in the piston body. It is characterized by providing.

  The piston and connecting rod assembly according to the present invention is characterized in that a concave portion is formed on one end face of the piston-side connecting portion, and a convex portion that enters the concave portion is formed on the piston body.

  According to the present invention, the piston side uneven portion is provided on the piston, and the rod side uneven portion is provided on the connecting rod so that both the uneven portions enter each other when the piston and the connecting rod are assembled. When assembling the rod, the connecting rod and the piston cannot be assembled unless they are assembled in the proper orientation. Thereby, generation | occurrence | production of the incorrect assembly of a piston and a connecting rod is prevented, and the assembly production efficiency of an engine can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1A is a schematic view showing a general-purpose engine equipped with an assembly of a piston and a connecting rod of the present invention, and FIG. 1B is a schematic view along a line 1B-1B in FIG. FIG.

  As shown in FIG. 1, this general-purpose engine has a crankcase 11 on which a crankshaft 10 is rotatably mounted. The crankcase 11 is composed of a case body 11a and a case cover 11b attached to the case body 11a. The crankcase 11 is provided with a cylinder 12. A piston 14 is incorporated in the cylinder bore 13 of the cylinder 12 so as to be reciprocally movable. The piston 14 is connected to the crankshaft 10 via a connecting rod 15, and is provided at a piston side connecting portion at one end of the connecting rod 15. A piston pin 16 to be assembled to the piston 14 is inserted into the pin insertion hole, and the crankshaft side connecting portion at the other end is assembled to a crankpin 17 provided on the crankshaft 10.

  In order to start the engine on the crankshaft 10, as shown in FIG. 1A, a support shaft 21 is fixed to an engine cover 18 attached to the crankcase 11, and a recoil pulley 22 is attached to the support shaft 21. A recoil rope 24 having a recoil knob 23 provided at the tip is wound around the recoil pulley 22. The recoil pulley 22 is provided with an engagement member 26 that can be engaged with a flywheel 25 attached to the crankshaft 10. When the recoil rope 24 is pulled out and the recoil pulley 22 is rotated, the engagement member 26 becomes a flywheel. 25, the crankshaft 10 can be driven manually to start the engine.

  When the generator is driven using this general-purpose engine, the generator is incorporated in the crankshaft 10, and when the power sprayer is driven, the shaft of the sprayer is connected to the crankshaft 10. Become. A cooling fan 27 for generating cooling air around the engine is attached to the crankshaft 10 via a flywheel 25.

  The cylinder head 29 attached to the cylinder 12 includes an intake valve 31 for opening and closing an intake port for supplying an air-fuel mixture to the combustion chamber 30 in the cylinder 12, and an internal combustion chamber 30 as shown in FIG. An exhaust valve 32 is provided for opening and closing an exhaust port for discharging the combustion exhaust gas. In order to drive the intake valve 31 and the exhaust valve 32, as shown in FIG. 1, a sprocket 34 is fixed to the camshaft 33 rotatably mounted on the cylinder head 29 and fixed to the crankshaft 10. A chain 36 is stretched between the sprocket 35 and the sprocket 34, and the intake valve 31 and the exhaust valve 32 are driven via the valve operating mechanism 37 by the camshaft 33 driven by the crankshaft 10.

  The bottom of the crank chamber 38 formed inside the crankcase 11 is an oil pan, in which the lubricating oil 39 is accommodated, and in order to splash the lubricating oil 39 on the lubricating oil requesting portion, FIG. As shown in (B), a scraper 40 is provided on the cap 15a provided on the connecting portion of the connecting rod 15 on the crankshaft side.

  2 is a partially cutaway front view showing an assembly of a piston and a connecting rod according to an embodiment of the present invention, and FIG. 3A is an enlarged cross-sectional view in the direction along line 3A-3A in FIG. 3B is a partially cut away arrow view in the direction along the line 3B-3B in FIG. 3A, and FIG. 4 is a bottom view of the piston 14. FIG.

  As shown in FIGS. 2 and 3, the piston 14 has a plurality of piston ring grooves 41 formed on the outer peripheral surface thereof, and has a crown portion, that is, a piston main body 42. As shown in FIGS. 3 and 4, the piston main body 42 is provided with skirt portions 43, 44 that are opposed to each other in the circumferential direction, and each skirt portion 43, 44 faces the crankshaft 10. It protrudes from the main body 42 and has an arc shape along the circumferential direction of the piston main body 42. As shown in FIGS. 3A and 4, the piston body 42 has two boss portions 45 and 46 projecting integrally with the piston body 42, and the boss portions 45 and 46 are formed on the skirt portions 43 and 44. In contrast, the piston main body 42 is provided at a position shifted by 90 degrees in the circumferential direction. A piston-side connecting portion 48 provided at one end of the connecting rod 15 enters a housing space 47 formed between both boss portions 45 and 46.

  Boss holes 45 a and 46 a into which the end portions of the piston pins 16 are fitted are formed in the respective boss portions 45 and 46, and pins through which the piston pins 16 are inserted into the piston side connecting portions 48 of the connecting rod 15. An insertion hole 48a is formed. Therefore, the connecting rod 15 is connected to the piston 14 via the piston pin 16 by inserting the piston pin 16 into these holes with the boss holes 45a, 46a and the pin insertion hole 48a being aligned. Is done.

  As shown in FIG. 3A, a concave portion 51 is provided as a rod-side concavo-convex portion on one end surface of the piston-side connecting portion 48 of the connecting rod 15, and the piston 14 and the connecting rod 15 are assembled in the assembled state. A convex portion 52 that enters into the concave portion 51 is provided as a piston-side concave / convex portion on the piston main body 42, and the convex portion 52 projects into the accommodation space 47 from the inner surface of one boss portion 46. When the engine is driven, the connecting rod 15 swings with respect to the piston 14 within a range of a predetermined angle in FIG. 2, and the connecting rod 15 swings with respect to the piston 14 within this swinging angle range. The concave portion 51 is provided in a range of a predetermined angle θ in the swinging direction so that the convex portion 52 does not come into contact with the piston-side connecting portion 48 of the connecting rod 15 even if it moves.

  Therefore, when the connecting rod 15 is assembled to the piston 14, the piston side connecting portion 48 of the connecting rod 15 is inserted into the accommodation space 47 of the piston 14. The piston-side connecting portion 48 is inserted into the accommodating space 47 so as to face the convex portion 52 of the piston 14. With the piston side connecting portion 48 inserted to a predetermined position, the piston pin 16 is inserted from one side of the two boss portions 45 and 46, and both the boss holes 45a and 46a and the pin insertion hole 48a are inserted. The piston pin 16 is fitted. Thereby, the piston 14 and the connecting rod 15 are assembled via the piston pin 16. If the piston side connecting portion 48 is inserted such that the concave portion 51 of the connecting rod 15 faces the opposite side with respect to the convex portion 52, the convex portion 52 interferes with the piston side connecting portion 48 of the connecting rod 15. Therefore, the piston side connecting portion 48 cannot be inserted into the accommodation space 47 to a predetermined position, and the piston pin 16 cannot be fitted into the pin insertion hole 48a.

  Thus, when the piston 14 and the connecting rod 15 are assembled, the concave portion 51 into which the convex portion 52 provided in the piston 14 enters is provided in the piston-side connecting portion 48, and the opposite side of the piston-side connecting portion 48 is provided. Since the recess 51 is not provided on the end face, when the operator sets these in the assembly device for assembling the piston 14 and the connecting rod 15, the orientation of the connecting rod 15 and the piston 14 is set to an appropriate direction. If it is not set, assembly cannot be performed. Therefore, since the connecting rod 15 cannot be set with respect to the piston 14 in a state where the connecting rod 15 is reverse to the normal direction, the piston 14 and the connecting rod 15 are always assembled in a normal positional relationship. Thus, there is no occurrence of erroneous assembly, and the assembly production efficiency of the engine can be improved.

  FIG. 5 is a sectional view showing a part of an assembly of a piston and a connecting rod according to another embodiment of the present invention, and FIG. 5 shows the same part as FIG. In the case shown in FIG. 5, a convex portion 52 a is provided on one end face of the piston side connecting portion 48 of the connecting rod 15 as a rod side concave and convex portion, and the convex portion 52 is projected under the assembled state of the piston 14 and the connecting rod 15. A recess 51a into which the portion 52a enters is provided as a piston side uneven portion in the piston main body 42, and the recess 51a is provided at a position shifted by 180 degrees in the circumferential direction of the piston pin 16 with respect to the protrusion 52 shown in FIG. It has been. Thus, even if the concavo-convex relationship is reversed from the case shown in FIG. 3, it is possible to prevent erroneous assembly of the piston 14 and the connecting rod 15.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, the illustrated engine is a single-cylinder general-purpose engine, but is not limited to a single-cylinder, and the present invention can be applied to various engines other than the general-purpose engine.

(A) is the schematic which shows the general purpose engine with which the assembly of the piston of this invention and a connecting rod is mounted | worn, (B) is the schematic of the direction in alignment with the 1B-1B line | wire in (A). It is a partially cutaway front view showing an assembly of a piston and a connecting rod according to an embodiment of the present invention. (A) is an expanded sectional view of the direction in alignment with the 3A-3A line in FIG. 2, (B) is a partially notched arrow line view of the direction in alignment with the 3B-3B line in (A). It is a bottom view of a piston. It is sectional drawing which shows a part of assembly of the piston which is other embodiment of this invention, and a connecting rod.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Crankshaft 11 Crankcase 12 Cylinder 14 Piston 15 Connecting rod 16 Piston pin 17 Crank pin 40 Scraper 41 Piston ring groove 42 Piston main body 45, 46 Boss part 51 Recessed part (rod side uneven part)
52 Convex part (piston side uneven part)

Claims (2)

Piston body having a piston ring groove formed on the outer peripheral surface, a piston having a boss part integrally provided in the piston body and fitted to both ends of the piston pin, and a piston side connection having a pin insertion hole formed A piston and connecting rod assembly having a connecting rod connected to the piston by passing the piston pin through the pin insertion hole,
A rod side uneven portion is provided on the piston side connecting portion of the connecting rod,
An assembly of a piston and a connecting rod, wherein the piston body is provided with a piston-side uneven portion that enters the rod-side uneven portion under the assembled state of the piston body and the connecting rod.   2. The piston / connecting rod assembly according to claim 1, wherein a concave portion is formed on one end face of the piston-side connecting portion, and a convex portion that enters the concave portion is formed on the piston body. Connecting rod assembly.

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