JP6485487B2 - Reciprocating piston engine - Google Patents

Description

  The present invention includes a plurality of cylinders formed in a cylinder block and arranged in a specific direction, a plurality of pistons reciprocating in the plurality of cylinders, a plurality of connecting rods respectively connected to the plurality of pistons, and the specific direction And a reciprocating piston engine including a crankshaft that extends along the shaft and is commonly connected to the plurality of connecting rods.

  The reciprocating piston engine includes a piston that reciprocates in a cylinder and a crank mechanism that converts the reciprocating motion of the piston into a rotational motion. The crank mechanism includes a crankshaft including a crankpin and a crank journal, and a connecting rod that connects the crankshaft and a piston, and includes a plurality of types of bearing structures. Specifically, examples of the bearing structure portion include a connecting portion between a connecting rod and a crankpin, and a bearing portion formed on a crankshaft (crank journal) and a cylinder block. In these bearing structures, the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member are sliding surfaces that face each other.

  By reducing the frictional resistance of the sliding surface as much as possible, the fuel efficiency and output performance of the engine can be further improved. As a means for reducing frictional resistance, Patent Document 1 discloses that friction surfaces such as CVD diamond or DLC coating treatment and mirror polishing treatment are applied to sliding surfaces facing each other, and the relative speed of the shaft member or the bearing member is predetermined. A method is disclosed in which one of the two is levitated relative to the other when the value is greater than or equal to the value. In this case, since the sliding surfaces are not in contact with each other due to the levitation, the frictional resistance is reduced.

JP, 2006-121600, A

  However, in the method of Patent Document 1, it is necessary to coat the sliding surface with CVD diamond or DLC and further polish it, which greatly increases the labor and cost involved in the processing.

  An object of the present invention is to reduce frictional resistance in a crank mechanism in a reciprocating piston engine while suppressing labor and cost for processing.

In order to solve the above problems, the present invention is connected to a plurality of cylinders formed in a cylinder block and arranged in a specific direction, a plurality of pistons reciprocating in the cylinders, and the plurality of pistons, respectively. A reciprocating piston engine comprising: a plurality of connecting rods; and a crankshaft commonly connected to the plurality of connecting rods so as to rotate about an axis extending along the specific direction. A plurality of crank journals arranged along the axis of the crankshaft, and a plurality of crankpins arranged in the specific direction at positions spaced from the axis of the crankshaft, and the cylinder block includes an outer peripheral surface of each crank journal Each of the crank journals has a first inner peripheral surface that faces and slides relative to the outer peripheral surface. The connecting rods include a plurality of main bearings that are rotatably supported, and each connecting rod has a second inner peripheral surface that slides relative to the outer peripheral surface in opposition to the outer peripheral surface of each crankpin and A plurality of connecting rod side bearings for rotatably supporting the respective crank pins are provided, and a lubricating fluid is interposed between the first inner peripheral surface and the second inner peripheral surface and the outer peripheral surfaces facing each other. The first inner peripheral surface and the second inner peripheral surface each have a protruding shape portion that protrudes toward the outer peripheral surface facing each other and slides relative to the outer peripheral surface integrally with the inner peripheral surface. Each of the overhanging portions is located at the most projecting portion of the top portion, and is located farthest from each of the outer peripheral surfaces that are located on the downstream side in the sliding direction of the overhanging shape portion and facing each other. Each projecting shape part, When the separation distance between the top and the outer peripheral surface facing the top is the minimum clearance h1, and the separation distance between the bottom and the outer peripheral surface facing the bottom is the maximum clearance h2, the minimum clearance h1 and the maximum clearance h2 and is h2 / h1 = 1.5 to 5.0, is set in a range of, the said projecting shape portion kicked set on the inner peripheral surface of the second, the sliding of the projecting shape portion A microtextured structure portion having a plurality of grooves extending in a direction orthogonal to the direction, the groove of the microtextured structure portion has a downstream side in the sliding direction of the protruding shape portion provided with the microtextured structure portion deep upstream side has a slope surface becomes shallower, the overhang shape portion kicked set to the first inner peripheral surface located at both ends of the specific direction is not provided with the micro-textured structure portion projecting shape portion Reciprocating motion characterized by A piston engine is provided.

  According to this engine, the protruding portion is provided on each inner peripheral surface (first inner peripheral surface and second inner peripheral surface) of the main bearing portion and the connecting rod side bearing portion, and the dimensions thereof are as described above. By setting, when the crank journal and the crankpin rotate relative to these bearing portions, a lubricating fluid is supplied between the vicinity of the top of the protruding shape portion and the outer peripheral surfaces of the crank journal and the crankpin. By confining, the crank journal and the crankpin can be floated with respect to the inner peripheral surface of each bearing portion.

  Moreover, the projecting shape portion of the connecting rod side bearing portion is provided with a microtexture structure portion, and the lubricating fluid is repeatedly confined from a relatively wide space to a relatively narrow space by the inclined surface of the microtexture structure portion. However, the connecting rod side bearing portion and the crank pin can be circulated. Therefore, the confinement effect of the lubricating fluid can be enhanced and the crank pin can be more reliably floated from the connecting rod side bearing portion.

  However, among the main bearing parts formed in the cylinder block, those located at both ends in a specific direction have a large gap between the inner peripheral surface and the outer peripheral surface of the crankshaft as the crankshaft vibrates during engine operation. Prone. For this reason, if the micro-texture structure portion and thus the groove are provided also in the projecting shape portion of the main bearing portion located at both ends, an excessive gap is formed between the bottom portion of the groove and the outer peripheral surface of the crank journal. It becomes large and the lubricating fluid escapes through this gap, so that it becomes difficult to properly confine the lubricating fluid between the projecting shape portion and the outer peripheral surface of the crank journal.

  On the other hand, in the present embodiment, as described above, the protruding shape portion of the connecting rod side bearing portion is provided with the microtextured structure portion, while the main bearing portion is microscopically positioned at both ends in the specific direction. An overhanging shape portion that does not include the texture structure portion is provided. Therefore, in the connecting rod side bearing part, the buoyant force is reliably increased by the projecting shape part and the microtextured structure part, while the buoyant force by the projecting shape part is provided in the main bearing part located at both ends in the specific direction. It can be kept high, and the frictional resistance in the crank mechanism including these bearing portions can be appropriately reduced.

  Furthermore, the frictional resistance is reduced as described above by omitting the micro-texture structure part having a plurality of grooves and relatively difficult to process in the main bearing part located at both ends in a specific direction. However, labor and cost for processing can be reduced.

  In the above structure, the groove of the microtextured structure portion has a micro side top portion that is closest to the opposing outer peripheral surface, a micro side bottom portion that is the farthest portion, and a gap between the micro side top portion and the outer peripheral surface. Is the minimum gap h3, and the gap between the micro side bottom and the outer peripheral surface is the maximum gap h4, it is preferably set in the range of h4 / h3 = 1.5 to 5.0 ( Claim 2).

  According to this configuration, the microtexture structure portion is provided by setting the minimum gap h3 and the gap ratio h4 / h3 between the minimum gap h3 and the maximum gap h4 within the above numerical range in the microtexture structure portion. The levitation force applied to the bearing portion thus provided can be further increased, and the frictional resistance can be significantly reduced.

  In the above-described configuration, the grooves of the microtexture structure portion are the opening edges of the grooves, and the downstream edge and the upstream edge in the sliding direction of the protruding shape portion where the grooves are formed, and these edges A deepest micro side bottom located between the parts, a first surface between the downstream edge and the bottom, and a second surface between the upstream edge and the micro side bottom. An outer peripheral surface facing the protruding shape portion provided with the microtextured structure portion is a surface parallel to a sliding direction of the protruding shape portion, and the first surface and the second surface are A flat surface having an inclination with respect to the outer peripheral surface facing the projecting shape portion in which a groove including the first surface and the second surface is formed, and the inclination of the first surface is the surface of the second surface It is preferable that the second surface is larger than the inclination and the second surface is the inclined surface.

  According to this configuration, the flow of the lubricating fluid spreads in the region of the first surface having a relatively large inclination, and the flow of the lubricating fluid is gradually performed by the second surface (the inclined surface) having a relatively small inclination. The operation of being trapped in is repeated so that a good levitation force is generated.

  In the above configuration, the first surface of the microtexture structure portion is set to have an inclination angle with respect to the outer peripheral surface facing the projecting shape portion provided with the microtexture structure portion in a range of 70 ° to 90 °. (Claim 4).

  According to this configuration, most of the width of the groove can be configured by the second surface functioning as the inclined surface in the sliding direction of the bearing portion where the microtextured structure portion is provided. Therefore, the confinement effect of the lubricating fluid can be enhanced.

  In the above-described configuration, the pitch in which the plurality of grooves of the microtexture structure portion are arranged in the sliding direction of the protruding shape portion provided with the microtexture structure portion is set in a range of 1 μm to 1 mm. Preferred (claim 5).

  According to this configuration, the pitch of the plurality of grooves is optimized, and a larger levitation force can be generated.

  As described above, according to the present invention, it is possible to reduce the frictional resistance in the crank mechanism as much as possible while suppressing labor and cost for processing.

It is a schematic sectional drawing of a reciprocating piston engine. It is the II-II sectional view taken on the line of FIG. It is sectional drawing which shows a crankshaft and a connecting rod schematically when a piston exists in a top dead center. It is sectional drawing which shows a crankshaft and a connecting rod roughly when a crank angle advances from a top dead center. It is sectional drawing which expanded and showed the connecting rod side bearing metal vicinity. It is a schematic diagram for demonstrating the profile of an overhang | projection shape part. It is a graph which shows the relationship between the clearance ratio which is ratio of the minimum clearance gap between the 1st sliding surface and the 2nd sliding surface, and the maximum clearance, and a load capacity coefficient. It is a schematic perspective view of a connecting rod side bearing metal. It is sectional drawing which expanded and showed the microtexture structure part. It is sectional drawing which showed typically the flow of the lubricating fluid in a micro texture structure part. It is the figure which expanded and showed the crankshaft periphery. It is a figure for demonstrating the relationship between a crank journal and a main bearing metal. 10 is a cross-sectional view showing a microtexture structure portion according to Modification Example 1. FIG. 10 is a cross-sectional view showing a microtexture structure portion according to Modification 2. FIG.

(1) Overall structure of engine Hereinafter, a reciprocating piston engine according to an embodiment of the present invention will be described based on the drawings. FIG. 1 is a schematic sectional view of a reciprocating piston engine 100. 2 is a cross-sectional view taken along line II-II in FIG.

  The reciprocating piston engine 100 includes a plurality of pistons 5 that reciprocate in the cylinder 2. The reciprocating piston engine 100 includes a crank mechanism that includes a plurality of connecting rods 8 connected to the plurality of pistons 5 and a crankshaft 7 connected to the plurality of connecting rods 8 in common. The reciprocating piston engine 100 is an in-line multi-cylinder engine in which a plurality of cylinders 2 are arranged in a specific direction, and the crankshaft 7 extends in a specific direction, that is, a cylinder arrangement direction (hereinafter also referred to as a cylinder arrangement direction). As the piston 5 reciprocates, the crankshaft 7 rotates around an axis X1 (hereinafter referred to as the crank center axis X1 as appropriate) extending in the cylinder arrangement direction. In the example of FIG. 1, the reciprocating piston engine 100 is a four-cylinder engine having four cylinders 2. The reciprocating piston engine 100 is a four-cycle engine, for example. In the following description, the vertical direction in FIG. 1 and the reciprocating direction of the piston 5 will be described simply as the vertical direction as appropriate.

  The reciprocating piston engine 100 includes a cylinder block 3 formed with a plurality of cylinders 2 each having a cylindrical inner peripheral surface, and a cylinder head 4 attached to the cylinder block 3.

  A combustion chamber 6 is defined in the cylinder 2 by a crown surface 5 A of the piston 5, an inner peripheral wall 2 A of the cylinder 2, and a lower surface of the cylinder head 4. When the fuel / air mixture burns in the combustion chamber 6, the piston 5 is pushed down. An intake port 9 and an exhaust port 10 communicating with the combustion chamber 6 are formed in the cylinder head 4. In FIG. 2, illustrations of an intake valve and an exhaust valve that open and close the opening portions of the ports 9 and 10, an ignition plug, and the like are omitted.

  An upper end portion 81 of a connecting rod 8 is connected to the piston 5. Specifically, the upper end portion 81 of the connecting rod 8 and the piston 5 are connected by a cylindrical piston pin 59 extending in a direction parallel to the crank central axis X1. The connecting rod 8 is connected to the piston 5 so as to be swingable around the central axis of the piston pin 59.

(2) Structure around the crankshaft A substantially disc-shaped flywheel 91 and a substantially disc-shaped crank pulley 92 are attached to both ends of the crankshaft 7 in the cylinder arrangement direction.

  The crankshaft 7 includes a plurality of crank journals 71, a plurality of crank pins 72, and a crank arm 73 that connects the crank journal 71 and the crank pins 72, which are arranged in the cylinder arrangement direction. A balance weight 74 is provided at the end of the crank arm 73 opposite to the end on the side connected to the crank pin 72.

  The crank journal 71 is a portion that serves as a rotating shaft of the crankshaft 7. The crank pin 72 is a portion connected to a lower end portion 82 (hereinafter referred to as a connecting rod large end portion 82) of the connecting rod 8, and is provided at a position corresponding to each connecting rod large end portion 82. In the present embodiment, as the reciprocating piston engine 100 is an in-line four-cylinder engine, four crank pins 72 are arranged at substantially equal intervals in the cylinder arrangement direction.

  3 is a cross-sectional view schematically showing the crankshaft 7 and the connecting rod 8 when the piston 5 is at the top dead center, and FIG. 4 is a cross-sectional view showing these when the crank angle has advanced from the top dead center. is there. A detailed structure around the crankshaft 7 will be described with reference to FIGS. 3, 4, and 2.

  The crank journal 71 has a cylindrical shape centered on the crank central axis X1. The crank journal 71 is rotatably supported around the crank center axis X1 by an annular main bearing metal (main bearing portion) 35 fitted in a bearing hole 31 formed in the cylinder block 3. The main bearing metal 35 is a sliding bearing in which a band-shaped metal circle is formed in an annular shape.

  The bearing hole 31 into which the main bearing metal 35 is fitted is formed in a wall member extending in a direction orthogonal to the crank central axis X1 provided in the cylinder block 3 (specifically, the lower block). The wall members are provided in the vicinity of both ends of the cylinder block 3 in the cylinder arrangement direction and at portions corresponding to the intermediate positions of the adjacent cylinders 2. The crank journal 71 is provided in the vicinity of both ends of the crankshaft 7 in the cylinder arrangement direction and between the adjacent crank pins 72. In this embodiment, as the reciprocating piston engine 100 is an in-line four-cylinder engine, five crank journals 71 and five main bearing metals 35 are provided.

  The crank pin 72 is located radially outside the crankshaft 7 with respect to the crank journal 71 and rotates around the crank central axis X1 at a position radially outside the crank journal 71. The crank pin 72 has a cylindrical shape centered on a line extending in parallel with the crank central axis X1.

  The crank pin 72 is rotatable relative to the connecting rod large end portion 82 by an annular connecting rod side bearing metal 85 (a connecting rod side bearing portion) fitted in a bearing hole 82 a formed in the connecting rod large end portion 82. It is supported. In the present embodiment, the connecting rod side bearing metal 85 is also formed of a band-shaped metal member, like the main bearing metal 35.

  As shown in FIG. 4, when the piston 5 and the connecting rod 8 reciprocate, the connecting rod large end portion 82 swings with respect to the crankpin 72, and the crankpin 72 rotates around the crank central axis X1 as indicated by an arrow C1. (Rotates clockwise in FIG. 4). As a result, the crankpin 72 rotates around the central axis of the crankpin 72 relative to the connecting rod large end portion 82 and the connecting rod side bearing metal 85 as shown by an arrow C2 ′ (in the example of FIG. 4). The crank pin 72 rotates counterclockwise with respect to the connecting rod side bearing metal 85).

  Thus, when the piston 5 reciprocates, the crank pin 72 and the connecting rod side bearing metal 85 rotate relatively to each other, and the outer peripheral surface 72a of the crank pin 72 is in relation to the inner peripheral surface 85a of the connecting rod side bearing metal 85. Slide. That is, the connecting rod side bearing metal 85 slides in a predetermined direction C2 (a direction opposite to the C2 ′) relative to the outer peripheral surface 72a of the crankpin 72. The connecting rod side bearing metal 85 has an inner peripheral surface (second inner peripheral surface) 85a that functions as a sliding surface 85a that slides along the predetermined direction C2 with respect to the outer peripheral surface 72a of the crankpin 72. ing. The inner peripheral surface 85a of the connecting rod side bearing metal 85 and the outer peripheral surface 72a of the crank pin 72 are opposed to each other with a gap G1.

  When the piston 5 reciprocates, the crank journal 71 rotates with respect to the main bearing metal 35 as indicated by the arrow C3 ′ (in the example of FIG. 4, the crankshaft 7 and the crank journal 71 are reciprocated by the piston 5). The outer peripheral surface 71a of the crank journal 71 slides in a predetermined direction C3 (a direction opposite to the C3 ′) relative to the inner peripheral surface 35a of the main bearing metal 35. To do. The main bearing metal 35 has an inner peripheral surface (first inner peripheral surface) 35a that functions as a sliding surface 35a that slides along the predetermined direction C3 with respect to the outer peripheral surface 71a of the crank journal 71. Yes. The outer peripheral surface 71a of the crank journal 71 and the inner peripheral surface 35a of the main bearing metal 35 face each other with a gap G2.

Lubricating fluid F is interposed in the gaps G1 and G2. The lubricating fluid F may be either liquid or gas, for example, air (viscosity = 1.8 × 10 ⁻⁵ [Pa · s]), water (8.9 × 10 ⁻⁴ [Pa · s]). ) Or 0W-20 class low viscosity oil (6.8 × 10 ⁻³ [Pa · s]).

  In this embodiment, low-viscosity oil is supplied to the gaps G1 and G2. Briefly, the cylinder block 3 and the crankshaft 7 are formed with an oil flow path 60 that connects the outside of the cylinder block 3 and the gaps G1 and G2, from an oil pan (not shown) to an oil pump (not shown). The low-viscosity oil pumped up by the drawing is supplied to the gaps G1 and G2 through these oil passages 60.

  In the present embodiment, the connecting rod side bearing metal 85 and the main bearing metal 35 are structured to reduce sliding resistance, that is, frictional resistance between the crankpin 72 and the crank journal 71 when the crankshaft 7 rotates. Is adopted. This structure will be described next.

(2-1) Projection Shape Section The sliding surface (inner peripheral surface) 35a of the main bearing metal 35 and the sliding surface (inner peripheral surface) 85a of the connecting rod side bearing metal 85 are cross sections orthogonal to the crank central axis X1. 2, the outer peripheral surface 71a of the crank journal 71 (hereinafter referred to as a “sliding surface 71a” as appropriate) and the outer peripheral surface 72a of the crank pin 72 (hereinafter referred to as “sliding surface 72a” as appropriate) projecting from each other. It has a protruding part M. In the present embodiment, the entire sliding surfaces 35a and 85a function as an overhanging shape portion M that protrudes toward the sliding surfaces 71a and 72a. In FIG. 4, the overhanging shape portion M is exaggeratedly drawn, but in actuality, it is a shape having a micron-order overhang that is difficult to distinguish visually. The projecting shape portion M slides in predetermined directions C2 and C3 with respect to the sliding surfaces 71a and 72a integrally with the sliding surfaces 35a and 85a.

  The projecting shape portion M is a macro side top portion (top portion) P1 that is the portion that projects most toward the sliding surfaces 71a and 72a, and a macro side that is the portion that is the furthest away from the sliding surfaces 71a and 72a. It has a bottom Q1. The macro side bottom portion (bottom portion) Q1 is provided on the downstream side of the sliding directions C2 and C3 of the sliding surfaces 35a and 85a with respect to the macro side top portion P1. In the present embodiment, in the sliding directions C2 and C3, the macro side top portion P1 is located on the most upstream side, and the macro side bottom portion Q1 is located on the most downstream side by making a round in the circumferential direction. Further, in the present embodiment, the projecting shape portion M has a spiral shape that gradually increases in diameter from the macro side top portion P1 toward the macro side bottom portion Q1 in the cross section orthogonal to the crank center axis X1, and the macro side top portion It protrudes most at P1, then retreats rapidly outward in the radial direction, and is connected to the macro side bottom Q1.

  When the sliding surfaces 35a and 85a slide with respect to the sliding surfaces 71a and 72a in the projecting shape portion M, a force acts to lift the sliding surfaces 35a and 85a from the sliding surfaces 71a and 72a. These sliding resistances are reduced.

  FIG. 5 is an enlarged sectional view showing the vicinity of the connecting rod side bearing metal 85. Here, the operation of the connecting rod side bearing metal 85 will be described with reference to FIG. When the sliding surface 85a of the connecting rod side bearing metal slides in the direction C2 along the circumferential direction of these surfaces with respect to the sliding surface 72a, that is, the outer peripheral surface 72a of the crank pin 72, the lubricating fluid F existing in the gap G1 is generated. Then, a flow in the inflow direction H10 opposite to the sliding direction C2 occurs. That is, the lubricating fluid F flows from the macro side bottom portion Q1 having a large channel area toward the macro side top portion P1 having a small channel area. As a result, the lubricating fluid F is confined between the sliding surface 85a and the sliding surface 72a in the vicinity of the macro side apex P1. The lubricating fluid F that has lost its destination generates a drag in a direction that expands the sliding surface 85a and the sliding surface 72a, and this drag lifts the sliding surfaces 35a and 85a from the sliding surfaces 71a and 72a. It works to let you.

  Similarly, in the main bearing metal 35, when the sliding surface 35a slides with respect to the sliding surface 71a, the lubricating fluid F is in contact with the sliding surface 85a and the sliding surface 72a in the vicinity of the macro side top portion P1. The levitation force is generated between the inner peripheral surface 35a of the main bearing metal 35 and the outer peripheral surface 71a of the crank journal 71.

  Here, the drag becomes the highest in the vicinity of the macro side apex P1 where the flow path area of the lubricating fluid F is the smallest. Therefore, in the present embodiment, the macro-side top portion P1 is disposed at a portion where the sliding surfaces 35a and 85a and the sliding surfaces 71a and 72a are most likely to come into contact so that the levitation force can be effectively obtained. It is like that. Specifically, when an explosion load (in-cylinder combustion pressure) generated by combustion of the air-fuel mixture in the combustion chamber 6 is applied to the piston 5, it is very high in a predetermined region of the crank pin 72 and the crank journal 71. The load is transmitted so that both can easily come into contact with each other. Therefore, the macro side apex P1 is disposed in the load transmission regions R1 and R2.

  For example, when the reciprocating piston engine 100 is a compression self-ignition type engine, the in-cylinder combustion pressure is highest in the range of crank angle = 0 ° to 20 °. Therefore, in the present embodiment, as shown in FIG. 3, in the main bearing metal 35 and the connecting rod side bearing metal 85, the axial center of the upper end portion 81 of the connecting rod 8, that is, the piston, with the piston 5 positioned at the top dead center. In the vicinity of a point where a line segment 8A connecting the central axis of the pin 59 and the axial center of the connecting rod large end portion 82, that is, the rotation center line of the crank pin 72 intersects the sliding surfaces 35a, 85a, Has been placed. In the present embodiment, the connecting rod side bearing metal 85 has a macro side top portion P1 disposed at the upper portion of the intersection, and the main bearing metal 35 has the macro side top portion P1 disposed at the lower portion of the intersection. ing.

<Macro profile>
In order to effectively develop the sliding levitation action by the protruding shape portion M, it is necessary to optimize the profile. What is important in this profile is the minimum gap h1 which is the distance between the macro side top portion P1 and the sliding surfaces 71a and 72a, and the distance between the macro side bottom portion Q1 and the sliding surfaces 71a and 72a. It is a gap ratio h2 / h1 which is a ratio with the maximum gap h2. It is also important to set the minimum gap h1 within an optimum range. This point will be described with reference to the schematic diagram of FIG.

  In the following description using FIG. 6, the sliding member B having the sliding surface SB made of an inclined surface slides in the sliding direction H1 along the sliding surface SA of the predetermined sliding member A. Explain when. The sliding surface SB has a top portion P that is the portion closest to the sliding surface SA, and a bottom portion Q that is disposed on the downstream side in the sliding direction H1 of the top portion P and is farthest from the sliding surface SA. The shape is gradually separated from the sliding surface SA from the upstream side to the downstream side in the sliding direction H1.

  When the sliding member B slides in the sliding direction H1 at the speed U, the sliding levitation force W generated between the sliding surface SB and the sliding surface SA is obtained by the following equation (1). be able to.

  In the formula (1), η is the viscosity of the lubricating fluid F interposed between the sliding surface SB and the sliding surface SA, and B is the length of the sliding surface SB in the sliding direction (the top portion P in FIG. 6). C is the length in the direction perpendicular to the sliding direction H1 of the sliding surface SB (the length in the direction perpendicular to the paper surface of FIG. 6), and U is the sliding of the sliding surface SB. Speed. h1 is the minimum gap, which is the distance between the top portion P and the sliding surface SA, that is, the minimum value of the gap G between the sliding surface SB and the sliding surface SA. m is the above-mentioned gap ratio, and the minimum gap h1 and the maximum gap h2 when the distance between the macro side bottom Q and the sliding surface SA, that is, the maximum value of the gap G is the maximum gap h2. The ratio is expressed by m = h2 / h1.

In equation (1), if the second item is the load capacity coefficient Kw (Kw = 6 / (m−1) ² {lnm−2 (m−1) / (m + 1)}), the sliding levitation force W is This is proportional to the load capacity coefficient Kw.

  FIG. 7 is a graph showing the relationship between the load capacity coefficient Kw and the gap ratio m. As shown in this graph, the sliding levitation force W becomes maximum when the gap ratio m is 2.2, and becomes smaller as the gap ratio m is separated from this value. From this finding, a high sliding levitation force W can be obtained if the gap ratio m is set in the vicinity of 2.2. Specifically, by setting the gap ratio m in the range of 1.5 to 5.0, the sliding levitation force W can be made equal to or higher than the line C in FIG. In this case, as the sliding levitation force W, a high value that is 60% or more of the maximum value (value when the gap ratio m is 2.2) can be obtained.

  Based on equation (1), the sliding levitation force W increases as the minimum gap h1 decreases. However, the minimum gap h1 that is too small increases the coefficient of friction generated between the sliding surface SA and the sliding surface SB. That is, there exists an optimum range in which the friction coefficient can be kept small for the minimum gap h1. The magnitude of the friction coefficient corresponds to the magnitude of friction during sliding levitation of the sliding surface SB. The smaller the friction coefficient, the better the sliding levitation can be realized. From this viewpoint, the desirable minimum gap h1 is in the range of 0.5 μm to 2.0 μm. When h1 exceeds 2.0 μm, the tendency of the sliding levitation force W to become smaller becomes significant from the above equation (1). On the other hand, when h1 is less than 0.5 μm, the coefficient of friction increases, and the tendency to inhibit good sliding levitation becomes significant.

From the above, as the profile of the projecting shape portion M provided in the main bearing metal 35 and the connecting rod side bearing metal 85,
Gap ratio m = h2 / h1 = 1.5-5.0
It is desirable to set it within the range. further,
Minimum gap h1 = 0.5 μm to 2.0 μm
It is desirable to set it within the range.

  The peak height DA, which is the maximum gap h2, and the difference h2-h1 between the maximum gap h2 and the minimum gap h1, is naturally determined by setting h1 and m. A preferable peak height DA is in the range of 0.25 μm to 8.0 μm from (h1_min × m_min−h1_min) to (h1_max × m_max−h1_max).

  The desired minimum gap h1 is a gap that is desired when the sliding member B, that is, the overhanging portion M and the piston 5 are actually performing a sliding operation. Therefore, it is desirable to determine the normal temperature design value so that the minimum gap h1 is ensured in a state where the crank journal 71 and the crank pin 72 rotate and slides with respect to the bearing metals 35 and 85 in a thermally expanded state.

  The sliding surface, that is, the outer peripheral surface 71a of the crank journal 71 and the outer peripheral surface 72a of the crank pin 72 are surfaces having high smoothness, and the minimum gap h1 is set to a value larger than the surface roughness of these outer peripheral surfaces 71a and 72a. It is desirable to set. This is to prevent the sliding surfaces 35a and 85a from coming into contact with the sliding surfaces 71a and 72a during sliding levitation. For example, when the surface roughness (arithmetic average roughness Ra) of the outer peripheral surface 71a of the crank journal 71 and the outer peripheral surface 72a of the crank pin 72 is 0.6 μm, the contact is reduced when the minimum gap h1 is set to 0.5 μm. Can occur. In order to avoid this contact, the minimum gap h1 is desirably set to be about twice or more the surface roughness of the outer peripheral surface 71a of the crank journal 71 and the outer peripheral surface 72a of the crankpin 72.

(2-2) Micro-textured structure portion of connecting rod side bearing metal The connecting rod-side bearing metal 85 is provided with a micro-textured structure portion 40 for enhancing the levitation force in addition to the overhanging shape portion M. That is, the micro-texture structure 40 is superimposed on the sliding surface (inner peripheral surface) 85a of the connecting rod side bearing metal 85 in order to assist the levitation created by the macro profile of the protruding portion M. ing. FIG. 8 is a perspective view schematically showing the connecting rod side bearing metal 85.

  In the present embodiment, a high load is applied to the crankpin 72 in a region near the region R1 where the macro side top portion P1 is disposed so that a levitation force can be effectively obtained while suppressing the processing region of the microtextured structure portion 40 to a small extent. And a sliding surface (inner peripheral surface) 85a of the connecting rod side bearing metal 85 in the same manner as the regions R1 and R11 by applying a high inertia force from the piston 5 to the region R11 where the pressure is transmitted. The microtextured structure portion 40 is provided in a region R12 where the sliding surface (outer peripheral surface) 72a of the crank pin 72 is likely to come into contact. On the other hand, in the present embodiment, the microtexture structure portion 40 is provided over the entire sliding surface 85a in the cylinder arrangement direction (direction orthogonal to the sliding direction of the connecting rod side bearing metal 85).

  FIG. 9 is an enlarged view of a part of FIG. 3, and is a cross-sectional view orthogonal to the cylinder arrangement direction, showing the microtexture structure portion 40 in an enlarged manner.

  The microtextured structure portion 40 has a plurality of grooves 41 extending in the cylinder arrangement direction formed on the sliding surface 85a of the connecting rod side bearing metal 85 (that is, the direction orthogonal to the sliding direction of the connecting rod side bearing metal 85 with respect to the crank pin 72). Consists of. Each groove 41 is a minute groove having a groove width on the order of microns, and is arranged at a predetermined pitch in the sliding direction of the connecting rod side bearing metal 85 with respect to the crank pin 72. The direction in which the groove 41 extends may not be completely orthogonal to the sliding direction, and may be inclined from the orthogonal direction as long as the effect of levitation described later is obtained. For example, the groove 41 may extend in a direction inclined by about 10 ° to 20 ° with respect to the orthogonal direction.

<Groove structure and action>
In this embodiment, the plurality of grooves 41 included in the microtextured structure section 40 form a sawtooth shape in a cross section orthogonal to the cylinder arrangement direction.

  Specifically, the outer peripheral surface 72a of the crankpin 72 is a cylindrical surface as described above, and each of the grooves 41 is a portion farthest from the micro side top portion 42 which is the portion closest to the outer peripheral surface 72a of the crankpin 72. And a slant surface 44 between the micro side top portion 42 and the micro side bottom portion 43. The inclined surface 44 is an inclined surface in which the downstream side in the sliding direction C2 of the connecting rod side bearing metal 85 with respect to the crank pin 72 is deep and the upstream side is shallow.

  The opening edge of one groove 41 includes an upstream edge 41U which is an upstream opening edge in the sliding direction C2 of the connecting rod side bearing metal 85 and a downstream edge 41D which is a downstream opening edge. These edge parts 41U and 41D are also a pair of micro side top parts 42 adjacent to the up-down direction. In other words, the micro side top portion 42 of one groove 41 also serves as the downstream side edge portion 41 </ b> D of the groove 41 adjacent to the upper side of the one groove 41. That is, there is no flat portion such as a plateau portion between adjacent grooves 41, and a plurality of grooves 41 are continuously provided in the vertical direction. Accordingly, the groove pitch L1 is the same as the vertical length (groove width) between the upstream edge 41U and the downstream edge 41D.

  The groove 41 has a first surface 45 between the downstream side edge portion 41 </ b> D and the micro side bottom portion 43, and a second surface 46 between the upstream side edge portion 41 </ b> U and the micro side bottom portion 43. The first surface 45 is a plane extending in the radial direction of the crank pins 72 and the cylinder arrangement direction. The second surface 46 is a flat surface that is inclined with respect to the outer peripheral surface 72 a of the crankpin 72 and extends in the cylinder arrangement direction. However, the second surface 46 is not an orthogonal surface like the first surface 45 but a plane having a relatively gentle inclination. In the present embodiment, the second surface 46 is the inclined surface 44 described above. Further, the width of the second surface 46 (inclined surface 44) in the sliding direction matches the groove width (groove pitch L1).

  The plurality of grooves 41 can be formed by various cutting processes using a minute cutting blade. For example, the necessary groove 41 can be formed by bringing the cutting blade into contact with the sliding surface (inner peripheral surface of the connecting rod side bearing metal 85) 85a while rotating the piston 5 with a lathe. Further, when the groove 41 is provided only in a partial region of the sliding surface 85a, it is necessary by an elliptical vibration cutting process in which a minute cutting blade is in contact with the inner peripheral surface 85a while drawing an elliptical or circular locus. The groove 41 can be formed.

  FIG. 10 is a view corresponding to FIG. 9, and is a cross-sectional view schematically showing the flow FA of the lubricating fluid F during sliding between the crankpin 72 and the connecting rod side bearing metal 85. When the connecting rod side bearing metal 85 moves downstream in the sliding direction C2 at the speed H1, the gap G1 between the inner peripheral surface 85a of the connecting rod side bearing metal 85 and the outer peripheral surface 72a of the crank pin 72 is lubricated. The ionic fluid F flows relatively toward the upstream side in the sliding direction C2, and a flow FA that flows from the downstream side to the upstream side in the sliding direction C2 is formed in the gap G1. This flow FA is a laminar flow.

  Here, each of the grooves 41 has the inclined surface 44 in which the downstream side in the sliding direction C2 is deep and the upstream side is shallow as described above. Therefore, when the connecting rod side bearing metal 85 slides, the laminar flow FA flows while repeating the operation of being confined from a relatively wide space to a relatively narrow space. That is, the flow FA is gradually confined in a narrow space, that is, a region having a small flow passage area, and the density is increased by the inclined surface 44 that narrows the gap G with the outer peripheral surface 72a of the crankpin 72 as it goes upward. Due to such a confinement action, the inner circumferential surface 85a of the connecting rod side bearing metal 85 is given a force in a direction away from the outer circumferential surface 72a of the crankpin 72, that is, a large levitation force floating on the crankpin 72. become. Thereby, the sliding resistance between the inner peripheral surface 85a of the connecting rod side bearing metal 85 and the outer peripheral surface 72a of the crankpin 72 is reduced.

<Profile of micro-texture structure>
The technical idea shown in FIGS. 6, 7, and Expression (1) can also be applied to the profile of the microtexture structure portion 40. That is, when the distance between the micro side top portion 42 and the outer peripheral surface 72a of the crankpin 72 is the minimum clearance h3, and the distance between the micro side bottom portion 43 and the outer peripheral surface 72a of the crankpin 72 is the maximum clearance h4, It is desirable to set the gap ratio m = h4 / h3 in the range of 1.5 to 5.0. Note that the minimum gap h3 is naturally 0.5 μm to 2.0 μm, similar to the minimum gap h1 for the protruding shape portion M. Further, the maximum gap h4 and the groove depth D (h4-h3) are naturally determined by setting the minimum gap h3 and the gap ratio m.

  Also for this micro profile, the minimum gap h3 is set to a value larger than the surface roughness of the outer peripheral surface 72a of the crankpin 72, for example, about twice or more the surface roughness of the outer peripheral surface 72a of the crankpin 72. Is desirable.

  The groove pitch L1 of the plurality of grooves 41 is desirably set in the range of 1 μm to 1 mm, preferably in the range of 5 μm to 100 μm. None of the microtextured structure portions 40 composed of the grooves 41 having the groove pitch L1 that is too short and the groove pitch L1 that is too long can exhibit the above-described confinement action satisfactorily. By setting the groove pitch L1 in the above range, a large levitation force can be generated.

(2-3) Relationship between main bearing metal and microtextured structure portion Here, if the microtextured structure portion 40 is provided as described above, the levitation force is increased. However, the microtexture structure portion 40 has a structure having a plurality of grooves 41. Therefore, if the microtextured structure portion 40 is provided on the protruding shape portion M of the main bearing metal 35, the levitation force may be reduced. This point will be described.

  FIG. 11 is an enlarged view of the periphery of the crankshaft 7 in FIG. In FIG. 11, a part of oblique lines indicating a cross section is omitted so that the drawing becomes clear.

  When the piston 5 is reciprocated, the crankshaft 7 is given an inertial force due to reciprocating or rotational (peristaltic) motion of the piston 5, connecting rod 8, crankpin 72, balance weight 74, and the like. Oscillates so that the crank central axis X1 swings in the vertical direction and / or in the direction perpendicular thereto.

  Here, as described above, the flywheel 91 and the crank pulley 92 having relatively large weights are connected to both ends of the crankshaft 7 in the cylinder arrangement direction. Therefore, the amplitude of the crank central axis X1 increases as it approaches the ends of the crankshaft 7 in the specific direction. In the middle of the vibration of the crank central axis X1, the vibration in the vertical direction or the like as indicated by a line L92 indicated by a broken line in FIG. 11 is compared with a line L91 extending straight in the cylinder arrangement direction as indicated by a chain line in FIG. It begins to lean greatly in the direction. Specifically, the crank journal 71 provided on the crank central axis X1 is greatly inclined with respect to the line L91. In FIG. 11, the case where the crank center axis X1 swings in the vertical direction has been described. However, when the crank center axis X1 swings in a direction perpendicular to the paper surface of FIG. It vibrates so that the amplitudes at both ends in the direction of the central axis X1 are maximized.

  FIG. 12 is a cross-sectional view showing a state in which the crank journal 71 is inclined with respect to the line L91. As shown in FIG. 12, when the crank journal 71 is relatively inclined with respect to the line L91, the outer peripheral surface (sliding surface) 71a of the crank journal 71 and the inner peripheral surface (sliding surface) of the main bearing metal 35 are obtained. ) The separation distance from 35a becomes excessively large near the end in the direction along the line L91.

  Therefore, if the groove 41 of the microtextured structure portion 40 is formed on the inner peripheral surface 35a of the main bearing metal 35, the size of the gap G2 between the bottom of the groove 41 and the outer peripheral surface 71a of the crank journal 71 is excessive. Will become bigger. Then, as shown by the arrow in FIG. 12, the lubricating fluid F escapes from the space between the inner peripheral surface 35a of the main bearing metal 35 and the outer peripheral surface 71a of the crank journal 71 through this relatively large gap. Therefore, the effect of the levitation force by the projecting shape portion M is reduced.

  Therefore, in the present embodiment, the microtextured structure portion 40 is provided in the projecting shape portion M of the connecting rod side bearing metal 85, while the microtextured structure portion 40 is not provided in the projecting shape portion M of the main bearing metal 35. That is, the protruding shape portion M of the main bearing metal 35 is a protruding shape portion that does not include the microtexture structure portion 40.

  Here, as described above, the amplitude of the crankshaft 7 is greatest at both ends of the crankshaft 7 in the cylinder arrangement direction. In other words, as shown in FIG. 11, this amplitude is small at the center portion of the crankshaft 7 in the cylinder arrangement direction. Therefore, the microtexture structure portion 40 may be omitted only in the main bearing metal 35 at both ends in the cylinder arrangement direction, and the microtexture structure portion 40 may be provided in the main bearing metal 35 except for these in addition to the protruding shape portion M. Good. In particular, since the amplitude and inclination of the crank journal 71 located at the center of the crankshaft 7 in the cylinder arrangement direction are small, the micro-texture structure portion 40 is provided on the main bearing metal 35 located at the center of the main bearing metal 35 in the cylinder arrangement direction. If provided, this makes it possible to increase the levitation force.

(3) Operation and the like As described above, in the present embodiment, the protruding shape portion M is provided on the inner peripheral surface 35a of the main bearing metal 35 and the inner peripheral surface 85a of the connecting rod side bearing metal 85, and the minimum gap h1 is provided. By setting the clearance ratio m as described above, when the crankshaft 7 is rotated, the outer peripheral surface 71a of the crank journal 71 and the crankpin 72 are opposed to the portion near the macro side top portion P1 of the protruding portion M. The lubricating fluid F can be confined between the outer peripheral surface 72a of the two. As a result, the crank journal 71 and the crank pin 72 can be levitated with respect to the projecting shape portion M and the bearing metals 35 and 85. Therefore, the sliding resistance between the crank journal 71 and the crank pin 72 and the bearing metals 35 and 85 can be reduced.

  In addition, in the present embodiment, the micro-texture structure portion 40 is provided on the protruding shape portion M provided on the inner peripheral surface 85a of the connecting rod side bearing metal 85 facing the outer peripheral surface 72a of the crankpin 72, and the connecting rod side bearing is provided. The inclination of the inner circumferential surface 85a of the metal 85 extends in the cylinder arrangement direction, that is, the direction orthogonal to the sliding direction of the inner circumferential surface 85a of the connecting rod side bearing metal 85 with respect to the crankpin 72, and the downstream side of the sliding direction is deeper and the upstream side is shallower. A plurality of grooves 41 having a surface 44 are formed.

  For this reason, the flow FA of the lubricating fluid F is gradually confined in a narrow space by the inclined surface 44 to increase its density, whereby the gap between the inner peripheral surface 85a of the connecting rod side bearing metal 85 and the outer peripheral surface 72a of the crank pin 72 is increased. A large levitation force can be generated, and the sliding resistance between them can be further reduced.

  Furthermore, in the present embodiment, the microtexture structure portion 40 is provided on the inner peripheral surface 85a of the connecting rod side bearing metal 85 as described above, while the microtexture structure portion 40 is provided on the inner peripheral surface 35a of the main bearing metal 35. Absent. Therefore, as described above, the micro-texture structure 40 and thus the groove 41 are provided on the inner peripheral surface 35a of the main bearing metal 35, so that the gap between the main bearing metal 35 and the crank journal 71 is increased, and the gap is lubricated. It is possible to avoid the trapping of the ionic fluid F, and it is possible to ensure a high sliding reduction effect by the overhanging shape portion M provided in the main bearing metal 35. Further, it is not necessary to form the microtextured structure portion 40 and thus the micro-sized groove in the main bearing metal 35, and the labor of processing can be greatly reduced.

  In the present embodiment, in the microtextured structure portion 40 provided on the connecting rod side bearing metal 85, the gap between the micro side top portion 42 and the outer peripheral surface (sliding surface) 72a of the crankpin 72 is set to the minimum gap h3. The gap between the side bottom 43 and the outer peripheral surface 72a of the crank pin 72 is defined as a maximum gap h2, and these are set in a range of h4 / h3 = 1.5 to 5.0. In addition, a minimum gap h3 that is a gap between the micro side apex 42 and the outer peripheral surface 72a of the crankpin 72 is set in a range of h3 = 0.5 μm to 2.0 μm. For this reason, the outer peripheral surface 72a of the crank pin 72 can be floated more satisfactorily from the inner peripheral surface 85a of the connecting rod side bearing metal 85, and the sliding resistance can be significantly reduced.

  In the present embodiment, the first surface 45 between the lower edge 41D of the groove 41 of the microtextured structure 40 and the micro side bottom 43, the upstream edge 41U of the groove 41, and the micro side bottom 43 The second surface 44 is a plane inclined with respect to the outer peripheral surface 72a of the crankpin 72, and the first surface 45 is more than the second surface 44 with respect to the outer peripheral surface 72a of the crankpin 72. The second surface 44 functions as the inclined surface 44.

  Therefore, after spreading the flow of the lubricating fluid F in the region of the first surface 45 having a relatively large inclination, the flow of the lubricating fluid F is gradually confined by the second surface 44 having a relatively small inclination. Thus, a high levitation force can be reliably applied between the connecting rod side bearing metal 85 provided with the microtextured structure 40 and the outer peripheral surface 72a of the crankpin 72.

  In particular, the inclination angle of the first surface 45 with respect to the outer peripheral surface 72a is set to 90 ° so that the first surface 45 extends in a direction orthogonal to the outer peripheral surface 72a of the crankpin 72, and the groove 41 Most of the vertical width can be configured by the second surface 44 functioning as the inclined surface 44. Therefore, the confinement effect of the lubricating fluid F can be enhanced.

  Further, since the pitch in which the plurality of grooves 41 are arranged in the vertical direction is set in the range of 1 μm to 1 mm, a larger levitation force can be generated.

(4) Modifications Although the embodiment of the present invention has been described above, the present invention is not limited to this.

  For example, the lubricating fluid F is not limited to air but may be water or oil.

  The formation region of the groove 41 (microtextured structure portion 40) is not limited to the above, and may be the entire region of the inner peripheral surface 85a of the connecting rod side bearing metal 85 or the like.

  However, if the inner peripheral surface 85a of the connecting rod side bearing metal 85 is provided only in the regions R11 and R12 where the inner peripheral surface 85a and the crank pin 72 are easily in contact with each other, it has a micro-sized groove and is relatively processed. As described above, the sliding resistance generated when an explosive load is applied can be effectively reduced while reducing the processing area of the difficult microtexture structure portion 40 to improve workability and cost.

  Further, as described above, the microtexture structure portion 40 is omitted only in the main bearing metal 35 at both ends in the cylinder arrangement direction, and the microtexture structure portion is added to the main bearing metal 35 except for these in addition to the protruding shape portion M. 40 may be provided. In this case, the levitation force between the main bearing metal 35 and the crank journal 71 can be increased.

  In the above embodiment, the groove 41 has a sawtooth shape in the sliding direction (vertical direction), but the inclined surface 44 is deeper on the downstream side (lower side) in the sliding direction and on the upstream side (upper side). ) May be deformed as long as it has a tendency to become shallower. For example, the micro side bottom portion 43 may not be an acute angle but may be an R surface. Further, the inclined surface 44 may be a gentle convex surface or a concave surface.

<Modification 1>
FIG. 13 is a cross-sectional view of the inner peripheral surface 150S of the sliding portion (conrod-side bearing metal or main bearing metal excluding both ends in the cylinder arrangement direction) 150 provided with the microtextured structure portion 40a according to the first modification. In the above-described embodiment, the example in which the first surface 45 of the groove 41 is a plane extending in a direction orthogonal to the sliding surface 200S has been described. Modification 1 shows an example in which the first surface 45 is a surface inclined from the orthogonal direction.

  The groove 41 of the microtextured structure portion 40a includes a first surface 45 between the micro side top portion 42 and the micro side bottom portion 43 that is the downstream side edge portion 41D, and the micro side top portion 42 that is the upstream side edge portion 41U and the micro side surface 42. 2nd surface 46 between the side bottom parts 43 is included. Both the first surface 45 and the second surface 46 are flat surfaces that are inclined with respect to the sliding surface 200S. The first surface 45 has an inclination angle θ1 with respect to the sliding surface 200S, and the second surface 46 has an inclination angle θ2 with respect to the sliding surface 200S. Here, the first surface 45 is a surface (θ1> θ2) having a larger inclination than the second surface 46. A desirable range of the inclination angle θ1 of the first surface 45 with respect to the sliding surface 200S is 70 ° to 90 °. The inclination angle θ2 of the second surface 46 is preferably sufficiently small with respect to θ1, and can be selected from a range of about 10 ° to 55 °, for example.

  The first surface 45 is desirably a plane orthogonal to the sliding surface 200S, but may be a plane inclined with respect to the direction orthogonal to the above-mentioned limitation. In the groove 41 having the first surface 45 as described above, the laminar flow (flow FA) of the lubricating fluid F flows through the gap G between the outer peripheral surface 150S of the sliding portion 150 and the sliding surface 200S in the inflow direction. When flowing along H2, the width of the laminar flow suddenly expands in the region of the first surface 45 having a relatively large inclination angle θ1, and the second surface 46 (inclination surface 44) having a relatively small inclination angle θ2. The operation of gradually confining the laminar flow is repeated. A good levitation force is generated by the operation of the laminar flow.

<Modification 2>
FIG. 14 is a cross-sectional view of the outer peripheral surface 150S of the sliding portion 150 including the microtexture structure portion 40b according to the second modification. In the above-described embodiment, the example in which the plurality of grooves 41 are closely connected in the sliding direction (vertical direction) H1 has been described. In the second modification, an example in which a plateau is provided between adjacent grooves 41 is shown.

  The microtextured structure part 40 b includes a plurality of grooves 41 and a plateau part 49 disposed between the adjacent grooves 41. The plateau part 49 is a plane substantially parallel to the sliding surface 200S. The plateau portion 49 is a plane extending between the micro-side apex portion 42 that becomes the upstream edge portion 41U of the one groove 41 and the downstream edge portion 41D of the groove 41 adjacent to the upper side of the one groove 41. In this case, the groove pitch L1 is obtained by adding the groove width L2 that is the length of the upstream edge 41U to the downstream edge 41D of the groove 41 in the sliding direction H1 and the length of the plateau portion 49. . Thus, even if the plateau part 49 exists between the grooves, the levitation force can be generated as long as the plateau part 49 is not too long with respect to the groove width L2.

  The plateau portion 49 is desirably a surface having high smoothness. This is because the plateau portion 49 is a surface at the same height as the micro-side top portion 42 that defines the minimum gap h1, and if the smoothness is low, contact with the sliding surface 200S becomes a problem. In this case, the minimum gap h1 between the micro side top portion 42 and the sliding surface 200S is larger than the total surface roughness obtained by adding the surface roughness of the sliding surface 200S and the surface roughness of the plateau portion 49. It is desirable to set. For example, when the arithmetic average roughness Ra of the outer peripheral surface 72a of the crankpin 72 and the plateau portion 49 is both 0.5 μm, the minimum gap h1 is a value that exceeds these combined surface roughnesses of 1 μm, preferably twice or more. It is desirable to set it to a value.

2 cylinder 5 piston 7 crankshaft 8 connecting rod 71 crank journal 71a outer peripheral surface 72 a crank pin 72a crankpin of the outer peripheral surface 40 micro texture structure 41 groove 42 micro-side top 43 micro-side bottom F lubricating fluid M overhang shape of the crank journal Part P1 Macro side top (top of the overhanging part)
Q1 Macro side bottom (bottom of overhanging part)

Claims (5)

A plurality of cylinders formed in a cylinder block and arranged in a specific direction, a plurality of pistons reciprocating in the cylinders, a plurality of connecting rods respectively connected to the plurality of pistons, and the specific direction A reciprocating piston engine comprising a crankshaft commonly connected to the plurality of connecting rods so as to rotate about an extending axis;
The crankshaft includes a plurality of crank journals arranged along the axis of the crankshaft, and a plurality of crankpins arranged in the specific direction at positions spaced from the axis of the crankshaft,
The cylinder block has a first inner peripheral surface that slides relative to the outer peripheral surface facing the outer peripheral surface of each crank journal, and a plurality of main blocks that rotatably support the respective crank journals. Including bearings,
Each connecting rod has a second inner peripheral surface that slides relative to the outer peripheral surface in opposition to the outer peripheral surface of each crankpin, and a plurality of connecting rods that rotatably support the respective crankpins. Including side bearings,
A lubricating fluid is interposed between the first inner peripheral surface and the second inner peripheral surface and the outer peripheral surfaces facing each other,
The first inner peripheral surface and the second inner peripheral surface each have a protruding shape portion that protrudes toward the outer peripheral surface facing each other and slides relative to the outer peripheral surface integrally with the inner peripheral surface,
Each of the projecting shape portions is located at the most projecting portion, and is located farthest from the outer peripheral surfaces that are located on the downstream side of the projecting shape portion in the sliding direction and facing each other. Including the bottom,
In each projecting shape portion, the separation distance between the top portion and the outer peripheral surface facing the top portion is a minimum clearance h1, and the separation distance between the bottom portion and the outer peripheral surface facing the bottom portion is a maximum clearance h2. The minimum gap h1 and the maximum gap h2 are
h2 / h1 = 1.5-5.0,
Is set to the range of
Wherein said projecting shape portion kicked set to the second inner peripheral surface includes a micro texture structure having a plurality of grooves extending in a direction orthogonal to the sliding direction of the projecting shape portion,
The groove of the microtextured structure portion has an inclined surface where the downstream side is deep and the upstream side is shallow with respect to the sliding direction of the overhanging shape portion provided with the microtextured structure portion,
Wherein said projecting shape portion eclipse set the first inner circumferential surface, a reciprocating piston, wherein the micro is projecting shape portion having no texture structure, and being located at both ends of the specific direction engine. The reciprocating piston engine according to claim 1,
A portion of the groove of the microtextured structure portion that is closest to the opposing outer peripheral surface is a micro side top portion, and a farthest portion is a micro side bottom portion, and a gap between the micro side top portion and the outer peripheral surface is a minimum gap h3. When the gap between the micro side bottom and the outer peripheral surface is the maximum gap h4,
h4 / h3 = 1.5-5.0,
A reciprocating piston engine characterized by being set in a range of The reciprocating piston engine according to claim 1 or 2,
The groove of the microtextured structure portion is an opening edge of the groove, and a downstream edge and an upstream edge in the sliding direction of the protruding portion where the groove is formed, and between the edges. A deepest micro-side bottom located; a first surface between the downstream edge and the bottom; and a second surface between the upstream edge and the micro-side bottom;
The outer peripheral surface facing the protruding shape portion provided with the microtextured structure portion is a surface parallel to the sliding direction of the protruding shape portion,
The first surface and the second surface are flat surfaces having an inclination with respect to the outer peripheral surface facing the projecting shape portion in which a groove including the first surface and the second surface is formed,
The inclination of the first surface is greater than the inclination of the second surface;
A reciprocating piston engine, wherein the second surface is the inclined surface. The reciprocating piston engine according to claim 3,
The first surface of the microtextured structure portion is set to have a tilt angle of 70 ° to 90 ° with respect to the outer peripheral surface facing the protruding shape portion provided with the microtextured structure portion. Reciprocating piston engine characterized by The reciprocating piston engine according to any one of claims 1 to 4,
The pitch in which the plurality of grooves of the microtexture structure portion are arranged in the sliding direction of the protruding shape portion provided with the microtexture structure portion is set in a range of 1 μm to 1 mm. A reciprocating piston engine.