JP2010127164A - Piston pin support structure for piston crank mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide piston pin support structure for a piston crank mechanism, preventing galling of a groove opening end face in an axial working groove of a circumferential groove for clip by an end part of a circlip, and smoothening rotation of the circlip in the rotation generating no friction stress in the circlip. <P>SOLUTION: In the piston pin support structure for a piston crank mechanism, the axial groove 8 for work intersects with the circumferential groove 7 for clip of a pin hole 5 and is directed in the axial direction, and is cut in more deeply than the circumferential groove 7 for clip. The circumferential groove 7 for clip is divided by the axial groove 8 for work, and mutually-opposed groove opening end parts thereof are enlarged to form enlarged groove parts 7B. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a support structure for a piston pin for connecting a connecting rod to a piston in a piston / crank mechanism.

  Generally, in a piston / crank mechanism in an internal combustion engine, a piston pin boss portion opposed to the back surface of a piston that reciprocates in a cylinder protrudes, and a piston pin is rotatably inserted into a coaxial pin hole of both piston pin boss portions, The small end portion of the connecting rod is connected to the central portion of the piston pin pivotally supported at both ends.

Piston pins having both ends inserted into the respective pin holes of both piston pin boss portions are restricted from moving in the axial direction by circlips fitted to the inner peripheral surfaces of both pin holes, and are prevented from coming off.
A circlip, which is an annular clip that is partially cut out in a C-shape, is formed in the vicinity of the outer opening end of the inner peripheral surface of the pin hole of the piston pin boss portion, forming a circumferential groove for clip. The piston pin is prevented from coming off by the portion protruding from the circumferential groove for clip of the circlip (see, for example, Patent Document 1).

Japanese Patent No. 3548451

In the pin hole structure of the piston disclosed in Patent Document 1, the inner periphery of the outer end of the pin hole is such that the circlip once fitted into the circumferential groove for clip of the pin hole can be deformed and removed inward in the radial direction. A concave portion is formed on the surface by cutting out from the opening end surface in the axial direction.
The recessed portion is a work axial groove that is cut deeper than the clip circumferential groove in the axial direction across the circumferential groove formed in the circumferential direction. The clip circumferential groove is the work axial direction. The circlip divided by the groove and fitted in the circumferential groove for the clip will straddle the working axial groove, so that a tool is inserted into the working axial groove, and the circlip is reduced in diameter from the outside. The circlip can be removed.

Lubricating oil is interposed between the pin hole of the piston pin boss part and the piston pin so that the piston pin can rotate, and while the reciprocating piston transmits power through the piston pin and the connecting rod connected thereto, The piston pin rotates.
The circlip that contacts the end face of the rotating piston pin may rotate together. However, if there is a working axial groove, the circlip rotates and its C-shaped defect (mating part) In some cases, both end portions of the circlip face the working axial groove, and at that time, both end portions of the circlip are slightly expanded outward by the working axial groove.

Thus, when both ends of the circlip are spread outward even a little, the circlip is rotated by contacting one end of the circlip with the groove opening end surface of the circumferential groove for the clip divided by the working axial groove. Rotation is restricted and galling may occur.
Further, when the rotating piston pin comes into contact with the circlip whose rotation is restricted, frictional stress is generated between the circlip and the piston pin may not be able to rotate well.

  The present invention has been made in view of the above points, and an object of the present invention is to prevent the circlip of the groove opening end surface in the working axial groove of the circumferential groove for the clip by the end of the circlip and the circlip Is provided with a piston pin support structure for a piston / crank mechanism that smoothly rotates and does not generate frictional stress on the circlip.

  To achieve the above object, the invention according to claim 1 is a piston pin in which both ends are pivotally supported by a pin hole of a pair of piston pin bosses projecting from the back surface of a piston reciprocatingly moving in a cylinder, and a connecting rod is connected. In the piston pin support structure of the piston / crank mechanism in which the circlip fitted into the circumferential groove for clip formed in the pin hole is regulated and prevented from coming off, it intersects with the circumferential groove for clip in the pin hole. The axial groove for working is formed by cutting deeper than the circumferential groove for clip in the axial direction, and the groove opening ends facing each other of the circumferential groove for clip divided by the axial groove for work are formed. A piston pin support structure for a piston / crank mechanism, wherein an expansion groove is formed by expanding.

  According to a second aspect of the present invention, in the piston pin support structure of the piston / crank mechanism according to the first aspect, the expansion groove portion of the circumferential groove for the clip gradually increases both the groove depth and the groove width. And expanding so as to reach the groove opening end face.

  According to a third aspect of the present invention, in the piston pin support structure of the piston / crank mechanism according to the first aspect, the circumferential groove for the clip has a circular arc shape in cross section, and the widening groove portion has an inner diameter in a circular arc shape in cross section. It is characterized by being gradually enlarged and expanded so as to reach the groove opening end face.

  According to a fourth aspect of the present invention, in the piston pin support structure of the piston / crank mechanism according to the first aspect, the expanding groove portion is formed by chamfering a groove opening edge of the circumferential groove for the clip. It is characterized by doing.

  According to a fifth aspect of the present invention, in the piston pin support structure of the piston / crank mechanism according to the fourth aspect, a plurality of cutting edges are formed at an outer peripheral end portion of the rotating disk, and the circumferential groove for the clip is formed by machining. Using a tool, insert the cutting edge of the cutting tool into the groove opening end of the circumferential groove for the clip and move it in the groove depth direction and the groove width direction to move the groove opening edge of the clip circumferential groove. The expanding groove is formed by chamfering.

  According to the piston pin support structure of the piston / crank mechanism according to claim 1, the groove opening end portions facing each other of the circumferential groove for clip divided by the working axial groove are widened so that the expanding groove portion is formed. Because it is formed, even if the end of the rotating circlip is a work axial groove that divides the circumferential groove for the clip and expands slightly outward, it enters into the expanded groove of the circumferential groove for the clip, and the groove opening The occurrence of galling due to contact with the end face is avoided, and the circlip is not restricted from rotating, so that frictional stress is not generated on the circlip between the rotating piston pins.

  According to the piston pin support structure of the piston / crank mechanism according to claim 2, the expansion groove portion of the circumferential groove for the clip gradually increases both the groove depth and the groove width to reach the groove opening end surface. Therefore, even if the end of the rotating circlip expands slightly outward in the working axial groove, it enters into the expanded groove part of the groove opening end part of the expanded circumferential groove for the clip, The circlip can be smoothly rotated while being gradually reduced in size by being guided by a smooth groove that gradually reduces the diameter of the expansion groove, and the frictional stress of the circlip is reduced between the circlip and the rotating piston pin. Generation can be prevented as much as possible.

According to the piston pin support structure of the piston / crank mechanism according to claim 3,
Since the circumferential groove for clip has a cross-sectional arc shape, the expanding groove portion is gradually expanded to reach the groove opening end surface by gradually expanding the inner diameter of the cross-sectional arc shape,
Even if the end of the rotating circlip extends slightly outward in the working axial groove, it enters into the expanded groove at the expanded groove opening end of the circumferential groove for the clip, and gradually expands the expanded groove The circlip can be smoothly rotated while being gradually reduced in size by being guided by a smooth groove having a reduced diameter and a similar groove having an arc shape in cross section. Generation of frictional stress of the circlip can be prevented as much as possible.
Further, the processing of the circumferential groove for clip is easy including the processing of the expanded groove portion.

  According to the piston pin support structure of the piston / crank mechanism according to claim 4, the groove opening edge is formed by chamfering the groove opening edge of the circumferential groove for clip, so that the groove opening edge is chamfered. The expanded groove portion can be formed by a simple processing operation that can be done, and the cost increase can be suppressed.

  According to the piston pin support structure of the piston / crank mechanism according to claim 5, the cutting tool is used in which a plurality of cutting blades are formed at the outer peripheral end portion of the rotating disk and the circumferential groove for the clip is formed. A cutting edge for turning the tool is inserted into the groove opening end of the circumferential groove for clip and moved in the groove depth direction and the groove width direction to chamfer the groove opening edge of the clip circumferential groove, thereby expanding the expansion. Since the opening groove is formed, both the circumferential groove for the clip and the expansion groove are processed by the same cutting tool, so there is no need to replace the cutting edge, and the circumferential groove for the clip and the expansion groove are Processing can be performed continuously, and the number of processing steps can be reduced.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
The piston / crank mechanism according to the present embodiment is applied to a reciprocating internal combustion engine. FIG. 1 shows a connecting rod connected via a piston pin 20 and a piston 1 reciprocating in a cylinder of the internal combustion engine. FIG. 2 is a front view showing a part of 25, a back view of the piston 1 is shown in FIG. 2, and a cross-sectional view of the piston 1 is shown in FIG.

The piston 1 includes a piston head 2 having a piston top surface on the combustion chamber side, a piston skirt portion 3 in which an outer peripheral portion of the piston head 2 extends to the back surface side, and a pair of piston pin bosses protruding from the back surface of the piston head 2 The part which consists of the parts 4 and 4 and the piston pin boss | hub parts 4 and 4 of the piston skirt part 3 oppose is missing.
Three ring grooves 2 r are formed on the outer peripheral surface of the piston head 2.

Circular pin holes 5 and 5 into which the piston pins 20 are inserted are coaxially drilled in the piston pin boss portions 4 and 4 facing each other.
In each pin hole 5, broach grooves 6 and 6 directed in the axial direction parallel to the central axis XX are formed on the inner peripheral surface thereof obliquely on the left and right sides of the central axis XX.
The broach groove 6 is a stress reducing groove that releases compressive deformation due to the thrust load of the piston pin 20.

Further, a circumferential groove 7 for a clip that makes one round in the circumferential direction is formed in the vicinity of the outer opening end on the inner circumferential surface of each pin hole 5.
The circumferential groove 7 for the clip intersects the two axially directed broach grooves 6 and 6, and the groove depths of both are shallow with approximately the same degree.
A circlip 10 that is C-shaped and elastically expands in diameter in the clip circumferential groove 7 is fitted to prevent the piston pin 20 from coming off (see FIG. 3).

One of the two broach grooves 6, 6 has a working axial groove 8 cut out from the opening end surface to the middle in the axial direction on the inner peripheral surface of the pin hole 5 from the broach groove 6. Deeply cut and formed.
The working axial groove 8 having a deep groove depth intersects with the clip circumferential groove 7 having a shallow groove depth formed in the circumferential direction, thereby dividing the clip circumferential groove 7.

  Therefore, since the circlip 10 that is elastically expanded and fitted in the clip circumferential groove 7 straddles the work axial groove 8, a tool is inserted into the work axial groove 8, The circlip 10 can be removed from the circumferential groove 7 for clips by reducing the diameter of the circlip 10 from the outside.

The groove depth and the groove width are gradually increased at both ends of the opposing circumferential groove 8 of the clip circumferential groove 8 divided by the working axial groove 8 so as to reach the groove opening end faces 8s and 8s. Expanding groove portions 7B and 7B are formed (see FIGS. 4, 5, and 7).
The clip circumferential groove 8 has an arc shape in cross section, and the widened groove portion 7B at the end portion divided by the work axial groove 8 of the clip circumferential groove 8 gradually expands the inner diameter of the arc shape in cross section. As a result, both the groove depth and the groove width are gradually increased and expanded so as to reach the groove opening end face 8s to form a tapered surface.

  The piston 1 has the structure as described above. As shown in FIG. 3, the small end portion of the connecting rod 25 is inserted between a pair of piston pin boss portions 4 and 4 protruding from the back surface of the piston head 2, The piston hole 20 is inserted so that the circular hole is coaxial with the pin holes 5 and 5, and the connecting rod 25 is pivotally supported at the center of the piston pin 20 supported by the pin holes 5 and 5 at both ends.

  The piston pin 20 has a length between the clip circumferential grooves 7 and 7 of the pin holes 5 and 5 and is sandwiched between circlips 10 and 10 fitted in the clip circumferential grooves 7 and 7, respectively. In this way, the movement in the axial direction is restricted and is prevented from coming off.

  When disassembling for maintenance or the like, as described above, a tool is inserted from the outside of the pin hole 5 into the working axial groove 8 to reduce the diameter of the circlip 10 from the outside and remove it from the circumferential groove 7 for clip. The piston pin 20 can be extracted from the pin hole 5 and the small end portion of the connecting rod 25, and the connecting rod 25 can be removed from the piston 1.

The power of the piston 1 that reciprocates in the cylinder is transmitted to the rotation of the crankshaft via a connecting rod 25 that connects the piston pin 20 and the crankpin of the crankshaft.
Lubricating oil is interposed between the pin hole 5 of the piston pin boss portion 4 and the piston pin 20 so that the piston pin 20 can be rotated. The reciprocating piston 1 is connected to the piston pin 20 and the connecting rod 25 connected thereto. The piston pin 20 rotates due to friction with the connecting rod 25 while power is transmitted via.

The circlip 10 fitted in the circumferential groove 7 for the clip may also rotate together when the end surface of the rotating piston pin 20 contacts.
When the C-shaped circlip 10 rotates, as shown in FIG. 7, both ends of the circlip 10 with the C-shaped defect portion may face the working axial groove 8, and the clip Both ends of the circlip 10 whose diameter is restricted by the circumferential groove 7 are released by the working axial groove 8 and slightly expand outward due to elasticity.

When the circlip 10 is further rotated in a state where the end portion is expanded outward, the end portion of the circlip 10 can enter the expanded groove portion 7B at the end portion of the circumferential groove 7 for clips.
If the expanding groove 7B is not formed at the end of the clip circumferential groove 7 as in the prior art, the end extending outside the rotating circlip 10 is in contact with the groove opening end surface 8s. In addition, the circlip 10 is restricted from rotating, and the circlip 10 is in contact with the circlip 10, and frictional stress is generated between the circlip 10 and the piston pin 20. To do.

However, since the expanding groove portion 7B is formed at the end portion of the circumferential groove 7 for the clip, such a situation can be avoided.
That is, the end portion of the rotating circlip 10 can enter the expanded groove portion 7B formed at the end portion of the circumferential groove 7 for the clip without contacting the groove opening end surface 8s, thereby causing galling. Furthermore, it is guided by a groove having a smooth taper surface that gradually decreases in diameter of the expanding groove portion 7B, and moves while gradually reducing the expansion to reach the circumferential groove 7 for the clip, and the circlip 10 is smooth. The rotation can be maintained, and the generation of the frictional stress of the circlip 10 with the rotating piston pin 20 can be prevented by rotating by itself.

The clip circumferential groove 7 is cut by a cutting tool 30 having a plurality of cutting edges formed at the outer peripheral end of a rotating disk. The same cutting tool 30 is used to cut the end of the clip circumferential groove 7. The expanded groove portion 7B can be processed and formed.

4 and 5, the disc-shaped cutting tool 30 is inserted into the axial position that forms the circumferential groove 7 for the clip inside the pin hole 5, and the rotating cutting blade is arranged on the inner periphery. The circumferential groove 7 for clips is formed by cutting the surface into a predetermined depth and cutting it once along the inner peripheral surface.

  Then, the cutting tool 30 is advanced in the centrifugal direction (groove depth direction) at a position corresponding to the working axial groove 8 to cut deeper than the circumferential groove 7 for clip, and then cut. By moving the tool 30 in the axial direction (groove width direction) and gradually retracting it in the center direction on both the inner side and the outer side in the axial direction, the tool 30 is divided by the working axial groove 8 of the circumferential groove 7 for clips. Further, the widened groove portions 7B and 7B having tapered surfaces can be formed by chamfering both groove opening edges.

  In this way, since both the clip circumferential groove 7 and the expanded groove portion 7B are formed by machining with the same cutting tool 30, the cutting blade replacement work is not required, and the clip circumferential groove 7 and the expanded groove portion 7B are not required. Can be processed continuously, and the number of processing steps can be reduced.

It is the front view which showed a part of connecting rod connected via the piston and piston pin of the internal combustion engine which concerns on one embodiment of this invention. It is a reverse view of a piston. It is an exploded view which shows the cross section of a piston, a piston pin, a connecting rod, and a circlip. It is a principal part expanded sectional view of a piston. It is the VV sectional view taken on the line of FIG. It is an expansion perspective view of the piston pin boss | hub part of a piston. It is a principal part expansion perspective view of a pin hole and a circlip.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piston, 2 ... Piston head, 3 ... Piston skirt part, 4 ... Piston pin boss part, 5 ... Pin hole, 6 ... Broach groove, 7 ... Circumferential groove for clips, 7B ... Expanding groove part, 8 ... For work Axial grooves,
10 ... Circlip, 20 ... Piston pin, 25 ... Connecting rod,
30 ... Cutting tool.

Claims (5)

A piston pin that is pivotally supported at both ends by a pin hole of a pair of piston pin bosses protruding from the back of the piston that reciprocates in the cylinder and is connected to a connecting rod is fitted into a circumferential groove for a clip formed in the pin hole. In the piston pin support structure of the piston / crank mechanism in which the circlip is restricted and prevented from coming off,
Crossing the circumferential groove for clip of the pin hole and oriented in the axial direction, the working axial groove is formed by cutting deeper than the circumferential groove for clip,
Piston pin support structure for a piston / crank mechanism, wherein the groove opening end portions facing each other of the circumferential groove for clip divided by the working axial groove are expanded to form an expanded groove portion .   2. The piston crank according to claim 1, wherein the expanding groove portion of the clip circumferential groove is expanded so as to gradually increase both the groove depth and the groove width to reach the groove opening end surface. Piston pin support structure of the mechanism.   2. The clip circumferential groove has a circular arc shape in cross section, and the expanding groove portion is expanded so as to gradually expand an inner diameter of the circular arc shape in a cross section to reach a groove opening end surface. Piston pin support structure of the piston / crank mechanism.   2. A piston pin support structure for a piston / crank mechanism according to claim 1, wherein the expanding groove portion is formed by chamfering a groove opening edge of the circumferential groove for the clip. Using a cutting tool in which a plurality of cutting edges are formed at the outer peripheral end of the rotating disk and the circumferential grooves for clips are formed by machining,
The cutting edge of the cutting tool is inserted into the groove opening end of the clip circumferential groove and moved in the groove depth direction and the groove width direction to chamfer the groove opening edge of the clip circumferential groove. 5. The piston pin support structure for a piston / crank mechanism according to claim 4, wherein the expansion groove is formed.

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