JP2007146909A - Sliding mechanism, crankshaft, manufacturing method for sliding mechanism, and manufacturing method for crankshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sliding mechanism, a crankshaft, a manufacturing method for the sliding mechanism, and a manufacturing method for the crankshaft for obtaining friction reduction effect effectively. <P>SOLUTION: In this sliding mechanism 1, the crankshaft 3, the manufacturing method for the sliding mechanism 1, and the manufacturing method for the crankshaft 3, a minute recessed part 6 is formed in a shaft sliding part 5 having a shaft 2 and a bearing 4 and sliding for the bearing 4 of the shaft 2, and tapered parts 7 which become thinner and thinner toward the direction of shaft end are formed at both ends in the axial direction of the shaft sliding part 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sliding mechanism, a crankshaft, a method for manufacturing a sliding mechanism, and a method for manufacturing a crankshaft.

  Conventionally, in order to reduce friction of a sliding portion of a sliding member provided on a crankshaft or the like of a vehicle engine, a method of forming a fine depression, a concave surface or a groove on the sliding surface of the sliding member has been performed. (For example, refer to Patent Document 1). In shaft sliding members, edge stress is generated, the contact at the end of the sliding part becomes severe, and initial wear and seizure may occur, and if the clearance is enlarged at the end of the sliding part, the end of the sliding part The minimum oil film thickness of the part increases and the initial wear and seizure resistance are improved. However, if processing is performed so as to increase the clearance of the end of the shaft member sliding member in which the fine concave portion is formed, the depth of the concave portion becomes shallow by the processing, and the friction reducing effect by the fine concave portion cannot be sufficiently exhibited.

In addition, when the hardness of the member in which the fine recess is formed varies, if the fine recess is processed under the same processing conditions, the depth of the fine recess becomes shallow in the hard part, and the soft part However, since the depth becomes deeper, variations occur in the depth, making it difficult to control the depth. This variation in depth is not preferable because, for example, if the fine concave portion is too deep, the friction characteristics deteriorate, and if it is too shallow, the friction reducing effect cannot be obtained sufficiently.
JP 2002-266848 A

  The present invention has been made to solve the above-described problems associated with the prior art, and can provide a sliding mechanism, a crankshaft, a sliding mechanism manufacturing method, and a crankshaft manufacturing capable of effectively obtaining a friction reducing effect. It aims to provide a method.

  The sliding mechanism according to the present invention that achieves the above object is a sliding mechanism having a shaft and a bearing, wherein a fine concave portion is formed in a shaft sliding portion that slides with respect to the bearing of the shaft, A taper portion that narrows toward the shaft end direction is formed at both ends in the axial direction of the shaft sliding portion.

  A crankshaft according to the present invention that achieves the above object is a crankshaft including a sliding mechanism having a shaft and a bearing, and a minute recess is formed in a shaft sliding portion that slides relative to the bearing of the shaft. In addition, a taper portion that narrows in the axial direction is formed at both axial ends of the shaft sliding portion.

  A manufacturing method of a sliding mechanism according to the present invention that achieves the above object is a manufacturing method of a sliding mechanism having a shaft and a bearing, wherein the sliding mechanism is formed on the shaft and slides with respect to the bearing and has both ends in the axial direction. After forming a minute recess in the shaft sliding part formed with low hardness of the part with the same applied pressure, the portion where the hardness of the shaft sliding part is formed is changed to the depth of the fine recess. Is processed to have a predetermined depth.

  A crankshaft manufacturing method according to the present invention that achieves the above object is a crankshaft manufacturing method including a sliding mechanism having a shaft and a bearing, and is formed on the shaft and slides relative to the bearing. In addition, after forming a minute concave portion in the shaft sliding portion formed with low hardness at both axial end portions with the same pressure, the portion where the hardness of the shaft sliding portion is formed low Processing is performed so that the depth of the recess becomes a predetermined depth.

  In the sliding mechanism according to the present invention configured as described above, since the tapered portion is formed at both ends in the axial direction of the shaft sliding portion, the clearance between the shaft and the bearing at both ends is increased, and the minimum oil film thickness is increased. Thus, the initial wear and seizure at both ends can be prevented, and the friction reducing effect by the fine recess can be effectively obtained.

  In the crankshaft according to the present invention configured as described above, since the taper portions are formed at both ends in the axial direction of the shaft sliding portion, the clearance between the shaft and the bearing at both ends is increased, and the minimum oil film thickness is reduced. The initial wear and seizure at both ends can be prevented, and the friction reducing effect by the fine recess can be effectively obtained.

  In the manufacturing method of the sliding mechanism according to the present invention configured as described above, the shaft sliding portion formed with low hardness at both ends in the axial direction is formed with a fine concave portion with the same applied pressure. The depth of the recess is deep at both ends in the direction. After this, the sliding mechanism having a friction reducing effect can be manufactured by finishing so that the depth of the fine recess becomes a predetermined depth.

  In the crankshaft manufacturing method according to the present invention configured as described above, the axial sliding direction is formed in the axial sliding portion formed with low hardness at both axial end portions with the same applied pressure. The depth of the recess is deep at both ends. Thereafter, finishing is performed so that the depth of the fine recesses becomes a predetermined depth, whereby a crankshaft having a friction reducing effect can be manufactured.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a sliding mechanism according to the present embodiment, and FIG. 2 is an enlarged cross-sectional view of a portion indicated by symbol A of the sliding mechanism of FIG.

  For example, the crankshaft 3 of the vehicle engine is connected via a slide bearing 4 to a connecting rod that receives fuel combustion pressure from a piston and transmits power to the crankshaft side.

  The slide bearing 4 is fixed to a connecting rod (not shown). As shown in FIG. 1, a crank pin 2 (shaft) formed on the crankshaft 3 is pivotally attached to the slide bearing 4, and the sliding mechanism 1. Is configured.

  The crankpin 2 has a shaft sliding portion 5 having a length L1 in the axial direction and pivotally attached to the bearing 4, and a surface of the shaft sliding portion 5 has a plurality of minute portions as shown in FIG. A concave portion 6 is formed. The fine recess 6 can hold lubricating oil and has an effect of reducing friction between the shaft sliding portion 5 and the bearing 4.

  At both ends in the axial center direction of the shaft sliding portion 5, taper portions 7 that are tapered toward the end portion direction are formed, and flat portions 8 are formed between the taper portions 7 at both ends.

  When the length L2 of the tapered portion 7 is 1/10 or less of the axial length L1 on one side, the effects of wear resistance and seizure resistance are not sufficiently exhibited against the edge stress. Further, when the length L2 of the tapered portion 7 is ¼ or less of the axial length L1 on one side, the initial wear resistance and seizure resistance are improved. Since the length L3 of the supporting flat portion 8 is reduced, the portion receiving the load is reduced, the pressure is increased, the oil film is thinned over the entire area, and the friction characteristics are deteriorated. In addition, due to a decrease in hardness due to a decrease in the length L3 of the flat portion 8, a decrease in strength also becomes a problem.

  For this reason, the taper portion length L2 of the shaft sliding portion 5 is 1/10 or more of the axial length L of the shaft sliding portion 5 at both axial direction end portions of the shaft sliding portion 5. Preferably, the flat portion 8 has a length L3 that is not less than ½ of the axial length L1.

  Therefore, for example, in the case of a crankshaft having an axial length L1 of 20 mm, the shaft sliding portion 5 is preferably formed with tapered portions 7 having a length L2 of 2 mm or more and 5 mm or less at both ends. . Moreover, although mentioned later, the fine recessed part 6 is deeply formed in the axial direction both ends of the shaft sliding part 5 by processing conditions. For this reason, when the taper length L2 is ¼ or less of L1, a texture region that is too deep remains in the processing of the taper portion, and when ¼ or more of L1, the taper portion is left. This is not preferable because the portion where the fine recess 6 has an appropriate depth is shallowed during the processing.

  Further, the minimum oil film thickness of the taper portion is not sufficiently increased when the reduction amount of the shaft diameter with respect to the shaft diameter of the flat portion is 2 μm or less. In addition, when the reduction amount of the shaft diameter is 6 μm or more, the oil film thickness at both ends increases, but the oil film at the taper-up portion becomes thin, and the minimum oil film thickness moves to the round-up portion, There is concern about wear and seizure at this part.

  Therefore, the minimum shaft diameter of the tapered portion of the shaft sliding portion is preferably a value obtained by subtracting a value of 2 μm or more and 6 μm or less from the shaft diameter of the flat portion.

  Unlike the present embodiment, when the tapered portion 7 is not formed in the shaft sliding portion 5, edge stress is usually generated at both ends in the axial direction of the shaft sliding portion 5 and the contact state becomes severe. In particular, when used under severe conditions where the oil film becomes thin between the shaft sliding portion 5 and the bearing 4, the oil film is absorbed into the fine recess 6 and the seizure resistance deteriorates with respect to the very thin oil film. Become. Therefore, by forming both end portions of the shaft sliding portion 5 in a tapered shape as in this embodiment, the shaft diameter of the shaft sliding portion 5 can be reduced and the clearance can be increased. The minimum oil film thickness at both ends of the portion 5 can be increased, and the friction reducing effect by the fine recesses 6 can be effectively obtained.

  Moreover, when the depth of the fine recessed part 6 formed in the shaft sliding part 5 is too deep, load capacity will fall and a friction characteristic will deteriorate. Moreover, when the depth of the fine recessed part 6 is too shallow, a friction reduction effect is not fully expressed. Therefore, it is preferable that the depth of the fine recessed part 6 formed in the shaft sliding part 5 is distributed within a range of 0.5 μm or more and 4.5 μm or less.

  Next, a method for manufacturing the sliding mechanism according to this embodiment will be described.

  In the workpiece before being formed into the crankpin 2, the tapered portion 7 and the fine recess 6 are not yet formed in the processed portion where the shaft sliding portion 5 is formed. This processed portion has a distribution of hardness, and is formed with low hardness at both ends in the axial direction.

  First, processing is performed to form fine concave portions 6 on the processed surface of the workpiece. There are various methods for forming the fine recesses 6. In this embodiment, for example, a micro indentation method is used. This method is a processing method in which a concave portion is formed by transferring the shape of a tool by pressing a tool having a plurality of convex portions at the tip against the processing surface.

  In this tool, the shape and distribution of each projection are uniform, and the tool is pressed against the machining surface with a uniform applied pressure to form a depression on the machining surface. Therefore, the processing conditions of the fine recess 6 with respect to the processed surface are substantially the same in all parts of the processed surface except for the hardness distribution of the processed portion. Therefore, as a result, the recessed part 6 is deeply formed in the site | part in which the hardness of the both ends of a process part is formed low.

  Next, a finishing process is performed to remove the raised portion formed around the fine recess 6. At this time, the depth of the recesses 6 formed deep at both ends of the processed portion can be distributed within the range of 0.5 μm or more and 4.5 μm or less, which is the preferred depth described above. If the depth of the fine concave portion 6 becomes too deep at both axial end portions of the shaft sliding portion 5 having low hardness, the load capacity is reduced and the frictional characteristics are deteriorated. By adjusting the depth by performing finishing after the processing, it is possible to sufficiently exhibit the friction reducing effect.

  In this finishing process, for example, the taper portion 7 can be processed at the same time. In this way, by processing the fine recesses 6 and then processing the tapered portions 7 at both ends, the minimum oil film thickness generated at the end of the shaft sliding portion 5 can be increased, and the initial wear and anti-fire resistance can be increased. It becomes possible to improve adherence. Further, at the same time as processing the taper portion 7, the depth of the fine concave portion 6 formed deep at both ends of the processed portion can be reduced to a preferable depth, and a friction reducing effect can be sufficiently exhibited. Moreover, in this process, since the hardness of the both ends of a process part is low, the taper part 7 can be processed easily.

  Moreover, since the depth of the fine recessed part 6 which became deep too much can be adjusted simultaneously with the removal of the rising part generated at the time of formation of the fine recessed part 6, the control of the depth of the recessed part 6 can be performed without increasing the number of processing steps. It can be done easily.

<Experimental example>
In order to investigate the influence of the depth of the fine concave portion 6 on the friction coefficient, a test piece in which the depth of the fine concave portion 6 was actually changed was manufactured, and a friction test was performed.

  3A and 3B are views showing an inner cylinder of a test apparatus for verifying the present embodiment, in which FIG. 3A is a side view of the inner cylinder, and FIG. 3B is a sectional view taken along line III-III in FIG. 4 is a view showing an outer cylinder of a test apparatus for verifying the present embodiment, (A) is a side view of the outer cylinder, (B) is a sectional view taken along line IV-IV of (A), FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a test apparatus, FIG. In addition, the unit of the dimension in a figure is mm.

  Table 1 shows the test conditions.

  As shown in FIGS. 3 to 5, the test apparatus 10 includes an inner cylinder 11 and an outer cylinder 12. The outer cylinder 12 is obtained by press-fitting an aluminum metal 14 having an inner diameter of 45 mm into a steel cylinder 13 having an outer diameter of 60 mm.

  The inner cylinder 11 is a carburizing and tempering material of steel (SCM420H steel) having an outer diameter of 43 mm and an axial curvature radius R of 700 mm. Both the inner cylinder 11 and the outer cylinder 12 have a width of 20 mm.

  An AC servomotor (not shown) is attached to each of the inner cylinder 11 and the outer cylinder 12, and the rotation can be independently controlled. An inner cylinder 11 is arranged inside the outer cylinder 12 and an oil film is formed between the inner cylinder 11 and the outer cylinder 12 by immersing the inner cylinder 11 and the outer cylinder 12 in an oil bath containing 5 W 30 SJ oil. Thus, the friction torque generated during the relative sliding motion was measured by a torque sensor (not shown) attached to the rotating shaft to which the inner cylinder 11 is attached, and the friction coefficient was calculated.

  In the experiment, the measurement was performed with a radial load of 200 N and an oil temperature of 80 ° C. The speed conditions were set such that the rotational speed u1 of the inner cylinder 11 and the rotational speed u2 of the outer cylinder 12 were u1 = 5 m / s and u2 = −1 m / s, respectively. This condition is such that the relative sliding speed (| u1-u2 |) is relatively slow, the average rolling speed ((u1 + u2) / 2) is high, and the minute recess 6 rotates at a higher speed than the counterpart metal. is there. Further, the speed condition at this time is a condition in which the oil film thickness is formed relatively thick as about 0.5 to 1 μm.

  FIG. 6 is a partial plan view showing the outer peripheral surface of the inner cylinder.

  As shown in FIG. 6, a fine recess 6 was formed on the surface of the inner cylinder 11, and the fine shape of the recess 6 was formed by microindent processing. After forming the fine shape of the concave portion 6, the bulge formed at the edge portion of the concave portion 6 was removed with a wrapping film having a particle size of 9 μm and used for the test. Table 2 shows the specifications of the fine shapes of the recesses of the experimental example and the comparative example.

  The comparative example is a test condition for the case where the fine concave portion 6 is not formed and has a surface having a roughness equivalent to the current level, and is for comparison with the experimental example. In this experimental example, the evaluation was carried out by changing only the depth without changing the surface shape or arrangement of the fine recesses 6.

  In the experimental example, the surface is finished to Ra = 0.02 mm by LAP processing, and the depth of the fine recess 6 is 1.3 μm in Experimental example 1, 2.4 μm in Experimental example 2, and 3. The thickness was 6 μm, and in Experimental Example 4, the thickness was 6.8 μm.

  Next, test results will be described with reference to FIG.

  FIG. 7 is a graph showing the relationship between the depth of the minute recesses and the ratio of change in the friction coefficient in this experimental result.

  The vertical axis of FIG. 7 represents the increase or decrease of the friction coefficient in the experimental example relative to the comparative example. The lower the friction coefficient is, the lower the friction coefficient is compared to the comparative example, and the higher the friction coefficient is, the worse it is. Represents that. As shown in the figure, it can be confirmed that the friction coefficient can be greatly reduced by appropriately setting the depth h of the recess 6. In addition, when the depth h of the fine recess 6 is too deep, the friction is abruptly deteriorated, so it is important not to become too deep. From this experimental result, it is preferable that the friction is reduced when the depth h of the fine recess 6 formed in the shaft sliding portion 5 is 0.5 μm or more and 4.5 μm or less. It could be confirmed.

  FIG. 8 is a graph showing the depth distribution in the axial direction of the shaft sliding portion processed by the conventional micro-indent processing, and FIG. 9 shows the measurement result of the hardness test of the journal portion of the crankpin. Is a graph showing the measurement results, (B) is a cross-sectional view of the journal portion showing the measurement position.

  The micro indent (plastic) process described above is applied to the method of processing a 3D fine shape with a controlled cross-sectional shape when reducing the friction by forming a fine recess 6 on an actual crankshaft. Actually, a minute recess 6 is formed on the crankshaft.

  In the conventional crankpin, as shown in FIG. 8, the depth of the minute concave portion is too deeper than the target value of 3 μm at both end portions of 20 mm that is the contact width of the metal in the shaft sliding portion. Although the depth of the fine recess is controlled by processing with a constant load with respect to the hardness of the workpiece, both ends of the crank pin, which is the workpiece, cannot be induction hardened so Is falling. This is also apparent from the hardness measurement result of the journal portion of the crankpin shown in FIG.

  Accordingly, the processed portion of the crank pin 2 has a distribution of hardness, and the hardness of both end portions in the axial direction is formed low, so that both end portions where the minute recesses 6 are formed deeply are tapered. By forming, the depth of the fine recessed part 6 can be controlled, forming a taper shape.

<Example of analysis>
It is known that edge stress is generated at the end portion of the bearing width in the journal portion of the crankpin, and the contact becomes the most severe. From the calculation result, the thickness of the oil film is the thinnest at the end. The oil film thickness when the shaft diameter is tapered at both ends of the metal width was obtained by analysis.

  FIG. 10 is a plan view showing an outline of the shape of the shaft sliding portion used in the calculation of the comparative example and the analysis example. (A) is a comparative example, (B) analysis example 1, and (C) is analysis example 2. Indicates. In addition, the unit of the dimension in a figure is mm.

  As shown in FIG. 10, the comparative example is a flat shaft, whereas in the first analysis example, the shaft diameter reduction at the end of the bearing width (the end of the tapered portion) is 6 μm (one side machining allowance is 3 μm). In Analysis Example 2, the amount of decrease in the shaft diameter at the end of the bearing width was 10 μm (one-side machining allowance: 5 μm).

  FIG. 11 is a graph showing the minimum oil film thickness with respect to the position in the bearing axial direction.

  As shown in FIG. 11, it was confirmed that the minimum oil film thickness at the end of the bearing width in Analysis Examples 1 and 2 with respect to the comparative example was increased compared to the comparative example. However, as in Analysis Example 2, if the amount of processing is increased too much, the minimum oil film thickness region moves to the taper-shaped cut-off portion (the boundary portion between the flat portion 8 and the taper portion 7). In addition, since the oil film becomes thinner, the frictional state deteriorates. Thus, when the reduction amount of the shaft diameter is 6 μm or more, the oil film thickness at both ends increases, but the oil film at the taper-up portion becomes thin and the minimum oil film thickness moves to the round-up portion. Therefore, there is a possibility that wear or seizure occurs at this portion. Further, when the reduction amount of the shaft diameter is 2 μm or less, the minimum oil film thickness is not sufficiently increased. Therefore, it can be confirmed that the minimum shaft diameter of the tapered portion 7 of the shaft sliding portion 5 is preferably a value obtained by subtracting a value of 2 μm or more and 6 μm or less from the shaft diameter of the flat portion.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, the present invention can be applied to other sliding portions instead of the shaft sliding portion 5 of the crankshaft.

It is sectional drawing which shows the sliding mechanism which concerns on this embodiment. It is an expanded sectional view of the site | part shown with the code | symbol A of the sliding mechanism of FIG. It is a figure which shows the inner cylinder of the test apparatus for verifying this embodiment, (A) is a side view of an inner cylinder, (B) is sectional drawing which follows the III-III line of (A). It is a figure which shows the outer cylinder of the test apparatus for verifying this embodiment, (A) is a side view of an outer cylinder, (B) is sectional drawing which follows the IV-IV line of (A). It is a schematic diagram which shows a test apparatus, (A) is a schematic diagram which shows the whole test apparatus, (B) is a fragmentary sectional view which follows the VV line of (A). It is a fragmentary top view which shows the outer peripheral surface of an inner cylinder. It is a graph which shows the relationship between the depth of the fine recessed part in this experimental result, and the ratio of the change of a friction coefficient. It is a graph which shows the depth distribution in the axial direction of the shaft sliding part processed by the conventional micro indent process. The measurement result of the hardness test of the journal part of a crankpin is shown, (A) is a graph which shows a measurement result, (B) is sectional drawing of the journal part which shows a measurement position. It is a top view which shows the outline of the shape of the shaft sliding part used for the calculation of a comparative example and an analysis example, (A) shows a comparative example, (B) analysis example 1 and (C) show analysis example 2. It is a graph which shows the minimum oil film thickness with respect to a bearing axial direction position.

Explanation of symbols

1 sliding mechanism,
2 Crankpin (shaft),
3 Crankshaft,
4 bearings,
5 axis sliding part,
6 recess,
7 Taper part,
8 flat part,
L1 Length of shaft sliding part,
L2 taper length,
L3 The length of the flat part.

Claims (22)

  A sliding mechanism having a shaft and a bearing, wherein a minute concave portion is formed in a shaft sliding portion that slides with respect to the bearing of the shaft, and a shaft end direction is provided at both ends in the axial direction of the shaft sliding portion. A sliding mechanism characterized in that a taper portion that narrows toward the back is formed.   The sliding mechanism according to claim 1, wherein the shaft sliding portion has a hardness distribution, and the hardness is low at both axial end portions of the shaft sliding portion.   The taper portion has a length within a range of 1/10 or more and 1/4 or less of an axial length of the shaft sliding portion from both axial ends of the shaft sliding portion. The sliding mechanism according to claim 1, wherein the sliding mechanism is characterized.   The minimum shaft diameter of the tapered portion is a value obtained by subtracting a value of 2 μm or more and 6 μm or less from a shaft diameter of a flat portion formed between the tapered portions of the shaft sliding portion. The sliding mechanism of any one of Claims 1-3.   The distribution of the depth of the fine recess formed in the shaft sliding portion is in the range of 0.5 μm or more and 4.5 μm or less. The sliding mechanism described in 1.   A crankshaft comprising a sliding mechanism having a shaft and a bearing, wherein a minute recess is formed in a shaft sliding portion that slides with respect to the bearing of the shaft, and the shaft sliding portion has both axial ends. The crankshaft is characterized in that a tapered portion is formed which narrows toward the axial end direction.   The crankshaft according to claim 6, wherein the shaft sliding portion has a distribution in hardness, and the hardness is low at both axial end portions of the shaft sliding portion.   The taper portion has a length within a range of 1/10 or more and 1/4 or less of an axial length of the shaft sliding portion from both axial ends of the shaft sliding portion. The crankshaft according to claim 6 or 7, characterized in.   The tapered portion has a length within a range of 2 mm or more and 5 mm or less of an axial length of the shaft sliding portion from each axial end portion of the shaft sliding portion. The crankshaft according to claim 8.   The minimum shaft diameter of the tapered portion is a value obtained by subtracting a value of 2 μm or more and 6 μm or less from a shaft diameter of a flat portion formed between the tapered portions of the shaft sliding portion. The crankshaft according to any one of claims 6 to 9.   11. The depth distribution of the minute recesses formed in the shaft sliding portion is in a range of 0.5 μm or more and 4.5 μm or less. 11. Crankshaft as described in   A method of manufacturing a sliding mechanism having a shaft and a bearing, wherein the same addition is applied to a shaft sliding portion that is formed on the shaft and slides with respect to the bearing and has low hardness at both axial end portions. Sliding characterized in that after forming a minute recess by pressure, the portion where the hardness of the shaft sliding portion is formed is processed so that the depth of the minute recess becomes a predetermined depth. Mechanism manufacturing method.   After forming the minute recesses in the shaft sliding portion, forming the minute recesses removes the bulge portion formed around the recess, and at the same time, the shaft slides at both axial ends of the shaft sliding portion. The method of manufacturing a sliding mechanism according to claim 12, wherein a tapered portion that narrows toward the end portion is processed.   The taper portion has a length in a range of 1/10 or more and 1/4 or less of an axial length of the shaft sliding portion from each axial end portion of the shaft sliding portion. The method for manufacturing a sliding mechanism according to claim 12 or 13, wherein the sliding mechanism is processed.   The minimum shaft diameter of the tapered portion is processed so as to be a value obtained by subtracting a value of 2 μm or more and 6 μm or less from the shaft diameter of the flat portion formed between the tapered portions of the shaft sliding portion. The manufacturing method of the sliding mechanism of any one of Claims 12-14 characterized by the above-mentioned.   16. The depth distribution of fine recesses formed in the shaft sliding portion is processed so as to be within a range of 0.5 μm or more and 4.5 μm or less. The manufacturing method of the sliding mechanism of any one of these.   A method of manufacturing a crankshaft having a sliding mechanism having a shaft and a bearing, wherein the shaft sliding portion is formed on the shaft and slides relative to the bearing and has low hardness at both axial end portions. In addition, after forming a minute recess with the same pressure, the portion where the hardness of the shaft sliding portion is formed is processed so that the depth of the minute recess becomes a predetermined depth. A method for manufacturing a crankshaft.   After forming the minute recesses in the shaft sliding portion, forming the minute recesses removes the bulge portion formed around the recess, and at the same time, the shaft slides at both axial ends of the shaft sliding portion. The method for manufacturing a crankshaft according to claim 17, wherein a tapered portion that narrows toward an end portion is processed.   The taper portion has a length in a range of 1/10 or more and 1/4 or less of an axial length of the shaft sliding portion from each axial end portion of the shaft sliding portion. The method for manufacturing a crankshaft according to claim 17 or 18, wherein the crankshaft is processed.   The tapered portion is processed so as to have a length within a range of 2 mm or more and 5 mm or less of an axial length of the shaft sliding portion from each axial end portion of the shaft sliding portion. The method of manufacturing a crankshaft according to claim 19.   The minimum shaft diameter of the tapered portion is processed so as to be a value obtained by subtracting a value of 2 μm or more and 6 μm or less from the shaft diameter of the flat portion formed between the tapered portions of the shaft sliding portion. The method for manufacturing a crankshaft according to any one of claims 17 to 20, wherein:   The depth distribution of fine concave portions formed in the shaft sliding portion is processed so as to be within a range of 0.5 µm or more and 4.5 µm or less. The manufacturing method of the crankshaft of any one of these.

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