JPH11210882A - Connecting structure for piston and connecting rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly slide a connecting rod relating to a semicylindrical bolster abutting to the flat underface of a piston crown part. SOLUTION: A semicylindrical bolster 3 is brought into contact with the flat underface central part of a piston crown part 2a. A bearing plate 16 having a circular arc-shaped cross-section is brought into contact with the underface of the bolster 3. A pair of left and right arms 44 having circular arc-shaped cross-sections extended to a crank shaft direction is provided in a small end part of a connecting rod 6. A seat cylinder 5 is supported in an inner space of a skirt part 11. The arm 44 is nipped between a cylindraical protrusion in the underface of the bearing plate 16 and a cylindrical recess in the upperface of the seat cylinder 5. A cylindrical recess in the upperface of the arm 44 is slidable with respect to the central part of the cylindrical protrusion in the underface of the bearing plate 16, and a cutout is provided in both end parts 16c in the circumferential direction of the cylindrical protrusion in the underface of the bearing plate 16 not to bring the both end parts 16c into slide contact with the cylindrical recess in the upperface of the arm 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connecting structure between a piston and a connecting rod in which the swing center of the connecting rod in an internal combustion engine is brought closer to the top surface of the piston so as to increase the displacement. The present invention relates to a connection structure between a piston and a connecting rod, in which a connecting rod slides smoothly on a semi-cylindrical pillow in contact with a lower surface.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 9-89107 filed earlier by the present applicant.
The connecting structure of the piston and the connecting rod disclosed in the publication, the component parts, the piston, the inner sleeve, a pillow that abuts on the back surface of the combustion chamber of the piston and the upper surface of the arm at the small end of the connecting rod,
Consists of a seat cylinder that abuts the lower surface of the connecting rod arm and a coupling ring that connects the inner sleeve and the seat cylinder. The seat cylinder is supported to bring the pivot center of the connecting rod and the center of gravity of the piston closer to each other. The protruding piece of the skirt portion to be set is set at the upper part of the skirt portion. Further, a pillow is directly superimposed on the back surface of the combustion chamber of the piston to reduce the number of superposed surfaces after assembly, thereby reducing the accumulated tolerance. The gap between the sliding surface and the overlapping surface of each part is
It is determined by the dimensional tolerance of each part of the seat cylinder and the piston.

However, as a result of incorporating the above-described structure into an engine and performing a test run of the engine, it has been found that there are the following problems to be improved.

(A) Since the integrated tolerance of each component is large, the gap between the sliding surface and the superposed surface varies, the oil film on the sliding surface is not stabilized, and the surface is easily roughened by fretting of the piston.

(B) Since the range in which the relative movement of the pillow and the connecting rod does not occur in the operating range from the top dead center to the bottom dead center of the piston does not occur, the land portion of the piston when the connecting rod swings. Alternatively, a rotational force that presses the lower end portion against the cylinder, that is, a rotational force about the pivot center of the piston acts on the piston. For this reason, wear of the piston ring, wear of the skirt, and wear of the cylinder become remarkable. In addition, when the connecting rod swings after the piston hits the cylinder, a high surface pressure acts on the sliding surface between the pillow and the connecting rod, so that the boundary lubrication state is attained. Become.

(C) Since the number of parts is large and high-precision machining is required, machining cost is increased and assembly is troublesome.

(D) In the process of increasing the swing angle about the swing center of the piston, the land or lower end of the piston is pressed against the peripheral wall of the cylinder, and the piston is forced by the sliding surface between the pillow and the connecting rod. Relative sliding occurs. At this time, the sliding surface is in a boundary lubrication state, no oil film is formed on the circumferential end of the sliding surface between the pillow and the connecting rod, and friction occurs due to metal contact.
At this time, a horizontal component force in the direction opposite to the swinging direction of the connecting rod is also applied to the pressing force of the piston, and the circumferential end of the sliding surface is significantly worn.

(E) The sliding surface of the connecting rod is submerged in the cylindrical recess of the seat cylinder. In this state, when the connecting rod swings, an oil film is formed on the circumferential end of the sliding surface of the connecting rod. It is not formed, and wear due to metal contact becomes significant.

(F) The explosion load acting on the top surface of the piston is transmitted to the connecting rod through the pillow, but the width of the pillow is smaller than the diameter of the piston. The portions corresponding to both sides of the crankshaft) are deformed downward, and fatigue cracks are generated in the thin bottom wall portion of the combustion chamber due to the repeated load.

(G) Since the inner sleeve and the seat cylinder are inserted inside the piston, it is necessary to machine almost the entire inner surface of the piston, which makes it difficult to reduce processing costs and mass-produce.

[0011]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to make it possible for a connecting rod to smoothly slide on a semi-cylindrical pillow abutting on a flat lower surface of a piston crown. Another object of the present invention is to provide a connection structure between a piston and a connecting rod.

[0012]

In order to solve the above-mentioned problems, according to the present invention, a semi-cylindrical pillow is abutted on the center of a flat lower surface of a piston crown, and a crankshaft is attached to a small end of a connecting rod. A pair of left and right arms having an arcuate cross section extending in the direction, supporting a seat cylinder in the inner space of the skirt portion, and connecting the arms with a cylindrical convex portion on the lower surface of the pillow and a cylindrical concave portion on the upper surface of the seat cylinder. Sandwiched between
The cylindrical concave portion on the upper surface of the arm is slidable with respect to the central portion of the cylindrical convex portion on the lower surface of the pillow, and both ends in the circumferential direction of the cylindrical convex portion on the lower surface of the pillow are in the cylindrical concave portion on the upper surface of the arm. It is characterized in that it does not slide.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, an arc-shaped bearing plate is brought into contact with the lower surface of a semi-cylindrical pillow in contact with the flat lower surface of a piston crown, and the lower surface of the bearing plate is brought into contact with a cylindrical projection. An H-shaped oil groove is provided. The circumferential central portion of the cylindrical projection on the lower surface of the bearing plate is in sliding contact with the cylindrical recess on the upper surface of the connecting rod arm, and both circumferential ends of the cylindrical projection on the lower surface of the bearing plate are on the upper surface of the connecting rod arm. It is cut out so as not to slide on the cylindrical recess.

When the connecting rod swings, the cylindrical concave portion on the upper surface of the arm formed at the small end of the connecting rod smoothly moves against the cylindrical convex portion on the lower surface of the bearing plate abutting against the lower surface of the semi-cylindrical pillow. Slide.
The sliding friction between the bearing plate and the arm of the connecting rod is reduced, the rotational force acting on the piston about the pivot point of the connecting rod as a fulcrum is reduced, and fretting applied to the cylinder by the piston is suppressed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS.
A recess as a combustion chamber 46 is provided on the upper surface of a, and a plurality of ring grooves 4 are provided in the upper half portion of the outer peripheral wall, that is, the land portion 10. The lower surface 14 of the bottom wall of the combustion chamber 46 is flattened. An annular cooling cavity 19 is formed in the crown 2 a so as to surround the combustion chamber 46. An inlet hole 31 and an outlet hole 32 are connected to the opposite side of the cooling cavity 19a in the circumferential direction. The flat upper surface 3a of the semi-cylindrical or semicylindrical pillow 3 abuts against the lower surface 14 of the crown 2a, more specifically, a circular depression surrounded by a peripheral wall 14a. Hatching is omitted from the piston body in FIGS.

At the small end of the connecting rod 6, a pair of left and right arms 44 having an arc-shaped cross section or a gutter-like shape projecting in the direction of the crankshaft are integrally formed. The upper surface 44a of the pair of left and right arms 44 forms a continuous cylindrical concave portion. A pair of arms 44 is swingably held between the bearing plate 16 and the seat cylinder 5 engaged with the lower surface 3 b of the pillow 3. Thus, the swing center o of the connecting rod 6 approaches the center of gravity g of the entire piston.

As shown in FIG. 7, cutouts 3c are provided at both left and right ends of the upper surface 3a of the pillow 3. As shown in FIGS. 1 and 8, both circumferential end portions 16 c of the lower surface 16 b of the bearing plate 16 are thinner than the central portion, and only the central portion of the lower surface 16 b
The upper surface 44a of the arm 44 is not in contact with the upper surface 44a of the arm 44, and the circumferential end 16c is not in contact with the upper surface 44a of the arm 44.
4a to prevent friction due to metal contact. An H-shaped oil groove 43 is formed at the center of the lower surface 16b of the bearing plate 16,
Lubricating oil is supplied to the oil groove 43 from an oil supply passage 15 provided inside the connecting rod 6.

As shown in FIGS. 1 and 3, the lower surface 1 of the crown 2a
The connection between the skirt 4 and the skirt 11 can be rounded in a dome shape. That is, although the curved surface 26 is formed as it is, the four bosses 2 projecting downward are formed on the periphery of the lower surface 14.
0 is provided, and the upper surface of the seat cylinder 5 is brought into contact with the flat lower surface 23 of the boss portion 20. The lower surface 5b of the seat cylinder 5 is formed in a conical surface. In the illustrated embodiment, the peripheral edge of the upper surface of the seat cylinder 5 is chamfered in a tapered shape, and a gap is provided between the peripheral edge of the upper surface of the seat cylinder 5 and the dome-shaped lower surface of the crown 2a.

As shown in FIGS. 2 and 4, the seat cylinder 5 is provided with an opening 5c which is elongated in a direction perpendicular to the crankshaft so that the connecting rod 6 can be inserted during assembly. A pair of cylindrical recesses 5a are provided on the upper surface, specifically, on the left and right walls of the opening 5c.
Is formed. A lower surface 44b that forms a cylindrical convex surface of the arm 44 is
It is swingably supported by the cylindrical recess 5 a of the seat cylinder 5. An oil sump 2 is provided in a gap between the end wall surface of the cylindrical concave portion 5a and the end surface of the arm 44.
9 (FIG. 2) are formed to allow relative sliding in the crankshaft direction between the piston 2 and the connecting rod 6, and the arrangement interval of the cylinders in the cylinder block and the connecting rod 6 are connected to the crankshaft.
Oil from the outlet hole 32 of the cooling cavity 19 is absorbed by the oil sump 29,
Through the sliding portion between the lower surface 44b of the arm 44 and the cylindrical recess 5a of the seat cylinder 5. The dimension a of the opening 5c is longer than the entire length of the arm 44, and the dimension b of the opening 5c in the crankshaft direction is
4 is made wider. Open the pair of arms 44 in the direction 5
c, the small end of the connecting rod 6 is opened 5c.
When the connecting rod 6 is rotated by 45 °, a pair of arms 4
4 can be engaged and supported in the cylindrical recess 5a. Four notches 7 a and four protrusions 7 are formed on the outer peripheral wall of the seat cylinder 5, and the conical surface of the lower surface 5 b of the protrusion 7 is supported by the conical surface 37 formed on the upper surface of the locking ring 33. Is done. The seat cylinder 5 is inserted into the skirt portion 11 so that the projecting piece 7 of the seat tube 5 passes between the projecting pieces 8 projecting radially inward from the inner peripheral wall of the skirt portion 11, Next, when the seat cylinder 5 is rotated about 22.5 °, the projection 7 of the seat cylinder 5 overlaps with the projection 8 of the skirt portion 11, and the projection 33 of the locking ring 33 will be described later.
supported on a.

As shown in FIG. 5, the locking ring 33 has four projecting pieces 33a and four notches 33b formed on the outer peripheral edge thereof, and holes 21 for locking a tool at both ends in the circumferential direction. Is done. A notch hole 31a aligned with the inlet hole 31 and a notch hole 42a through which a locking bolt 38 described later is inserted are provided in the inner peripheral edge of the locking ring 37. The locking ring 33 is a projection 33
a is supported on the protrusion 8 of the skirt portion 11. In order to support the locking ring 33 on the protruding piece 8, the locking ring 33 is inserted into the skirt 11 so that the protruding piece 33 a passes between the protruding pieces 8 of the skirt 11. Insert and rotate about 22.5 °. However, if the locking ring 33 is contracted and closed to some extent by the tool engaged with the hole 21, and the projection ring 33 a is inclined to some extent, the projection 33 a can be directly engaged with the projection 8.
An annular ridge 41 for suppressing eccentricity of the locking ring 33 is integrally formed on the lower surface 5b of the seat cylinder 5 so that the locking ring 33 is concentrically mounted on the skirt portion 11.

As shown in FIG. 9, in order to prevent the rotation of the piston 2 with respect to the connecting rod 6 and to obtain the circumferential positioning of the piston 2, a locking bolt 38 is provided with a locking ring 33.
And the screw hole 42 of the boss portion 20 of the piston 2 through the notch hole 42 a of the seat 2 and the hole 42 b of the seat cylinder 5.

During operation of the engine, oil injected from an oil jet (not shown) passes through the notch 31a of the locking ring 33, the inlet 31b of the seat cylinder 5, and the inlet 31 of the piston 2.
After entering the annular cooling cavity 19 shown in FIGS. 1 and 2 and cooling and cooling the crown 2a, it is dropped from the outlet hole 32 of the piston 2 into the oil reservoir 29 of the seat cylinder 5, and the cylindrical recess 5a of the seat cylinder 5 is formed. And arm 4
4 lubricates the sliding portion of the lower surface 44b and returns to the crankcase.
By separating the circumferential end 44c of the lower surface 44b of the arm 44 of the connecting rod 6 upward from the cylindrical recess 5a of the seat cylinder 5, high contact pressure metal contact when the connecting rod 6 swings is prevented. Lubricating oil from a hydraulic pump (not shown) is supplied from the oil supply passage 15 inside the connecting rod 6 to the upper surface 44 a of the pair of arms 44 and the bearing plate 16.
Lubricating the sliding portion of the lower surface 16b.

The locking ring 33 shown in FIG. 5 is wedge-engaged between the protruding piece 8 of the skirt portion 11 and the protruding piece 7 of the seat cylinder 5 by elastic expanding force. At 33, the locking ring 33 is expanded by the expanding means 35. That is, the end of the screw shaft 35a is engaged with one end of the locking ring 33, while the end of the nut member 35c screwed to the screw shaft 35a is engaged with the other end of the locking ring 33. The retaining ring 33 is expanded and fixed by the locking nut 35b.

According to the present invention, the use of the elastic locking ring 33 made of spring steel or the like allows the dimensional accuracy to be controlled by the lower surface 14 of the crown 2a and the lower surface 23 of the boss 20. , And the dimensional accuracy of other portions can be reduced. Also, the projecting piece 3 of the locking ring 33
The wedge engagement of the conical surface 37 of the seat 3 with the lower surface 5b of the seat cylinder 5 eliminates play in the vertical direction of the seat cylinder 5, and the clearance between the lower surface 16b of the bearing plate 16 and the upper surface 44a of the arm 44. Is stabilized, so that the conventional superficial surface roughness due to fretting of the piston 2 is eliminated.

The embodiment shown in FIGS.
The thickness of the bottom wall is smaller than that of the embodiment of FIGS.
A circular reinforcing plate 30 is engaged with the depression 4 to increase the rigidity of the piston 2, and the other configuration is the same as that shown in FIGS.

In each of the above-described embodiments, the pillow 3 and the bearing plate 16 are separately provided in order to reduce the range occupied by the bearing plate 16 made of an expensive and heavy bearing material and to reduce the processing cost and the weight. However, both may be integrated.

[0027]

According to the present invention, as described above, a semi-cylindrical pillow is brought into contact with the center of the flat lower surface of the piston crown, and a small end of the connecting rod is formed into an arc-shaped cross section extending in the crankshaft direction. 1
With a pair of arms, supporting a seat cylinder in the inner space of the skirt portion, sandwiching the arm between a cylindrical projection on the lower surface of the pillow and a cylindrical recess on the upper surface of the seat cylinder, The cylindrical concave portion on the upper surface of the arm is slidable with respect to the central portion of the cylindrical convex portion, and both ends in the circumferential direction of the cylindrical convex portion on the lower surface of the pillow do not slide on the cylindrical concave portion on the upper surface of the arm. When the connecting rod swings, smooth sliding of the cylindrical concave portion on the upper surface of the connecting rod arm with respect to the cylindrical convex portion on the lower surface of the bearing plate abutting on the lower surface of the semi-cylindrical pillow is obtained. Can be

In particular, a relief is provided at the circumferential end of the lower surface of the bearing plate (the thickness is reduced), and an H-shaped oil groove is provided at the lower surface of the bearing plate, so that the arm of the bearing plate and the connecting rod are provided. Abnormal wear of the sliding surface with the upper surface of the can be prevented.

The sliding friction between the bearing plate and the arm of the connecting rod is reduced, the rotational force acting on the piston about the swing center of the connecting rod is reduced, and fretting applied to the cylinder by the piston is suppressed.

Since the reinforcing plate is interposed between the flat lower surface of the piston crown and the upper surface of the pillow, the strength can be reduced even if the wall thickness of the lower wall of the combustion chamber, that is, the wall contacting the pillow, is reduced. Secure,
The piston can be made lightweight.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a connecting structure of a piston and a connecting rod according to the present invention.

FIG. 2 is a front sectional view of a connection structure between the piston and a connecting rod.

FIG. 3 is a bottom view of only the piston main body in the connection structure.

FIG. 4 is a bottom view of the seat cylinder in the connection structure.

FIG. 5 is a bottom view of the locking ring in the connection structure.

FIG. 6 is a bottom view showing a modified embodiment of the locking ring in the connection structure.

FIG. 7 is a perspective view of a pillow in the connection structure.

FIG. 8 is a bottom view of the bearing plate in the connection structure.

FIG. 9 is a front cross-sectional view showing a piston rotation stopping structure in the connection structure.

FIG. 10 is a side sectional view of a connecting structure of a piston and a connecting rod according to a modified embodiment of the present invention.

FIG. 11 is a front sectional view of a connecting structure of the piston and the connecting rod.

[Description of Signs] 2: Piston 2a: Crown 3: Pillow 3a: Upper surface 5:
Seat cylinder 5a: Cylindrical recess 5b: Lower surface 5c: Opening 6: Connecting rod 7: Projection piece 7
a: Notch 8: Protrusion 11: Skirt 14: Lower surface
15: Oil supply passage 16: Bearing plate 16b: Lower surface 16c: End 19: Cooling cavity 20: Boss 23:
Lower surface 26: Top wall 29: Oil reservoir 30: Reinforcement plate 31:
Inlet hole 32: Outlet hole 33: Locking ring 33a: Projection piece 33b: Notch 37: Conical surface 38: Detent bolt

Claims (5)

[Claims] A skirt having a semi-cylindrical pillow in contact with a flat lower central portion of a crown portion of a piston, and a pair of left and right arms having an arc-shaped cross section extending in a crankshaft direction at a small end of a connecting rod. A seat cylinder is supported in the inner space of the part, the arm is sandwiched between a cylindrical convex part on the lower surface of the pillow and a cylindrical concave part on the upper surface of the seat cylinder, and a central part of the cylindrical convex part on the lower surface of the pillow. On the other hand, the cylindrical concave portion on the upper surface of the arm is slidable, and both ends in the circumferential direction of the cylindrical convex portion on the lower surface of the pillow are configured not to slide on the cylindrical concave portion on the upper surface of the arm. , Connecting structure of piston and connecting rod. 2. A semi-cylindrical pillow abuts a central portion of a flat lower surface of a piston crown portion, a bearing plate having an arc-shaped cross section abuts a lower surface of the pillow, and a small end portion of a connecting rod in a crankshaft direction. A pair of left and right arms extending in an arcuate cross section is provided, and a seat cylinder is supported in the inner space of the skirt. The arm is formed by a cylindrical projection on the lower surface of the bearing plate and a cylindrical recess on the upper surface of the seat cylinder. The cylindrical concave portion on the upper surface of the arm is slidable with respect to the central portion of the cylindrical convex portion on the lower surface of the bearing plate, and both ends of the cylindrical convex portion on the lower surface of the bearing plate in the circumferential direction are the arms. The connecting structure of the piston and the connecting rod according to claim 1, wherein the connecting structure is configured not to be in sliding contact with the cylindrical concave portion on the upper surface of the piston. 3. An oil groove for holding lubricating oil is formed on at least one of a lower surface of the pillow or the bearing plate and an upper surface of the arm.
A connecting structure of the piston and the connecting rod according to claim 1 or 2. 4. The piston and connecting rod according to claim 1, wherein an oil reservoir that is open upward is formed between an end of the cylindrical recess on the upper surface of the seat cylinder and an end of the arm. Connection structure. 5. The connecting structure of a piston and a connecting rod according to claim 1, wherein a reinforcing plate is interposed between a flat lower surface of the piston crown and an upper surface of the pillow.