阅读说明：本技术 滑动部件 (Sliding component ) 是由 高桥育朗 于 2020-04-06 设计创作，主要内容包括：本发明的一个方面涉及的滑动部件具备与凸轮的外表面抵接的滑动面和设置于滑动面的螺旋状或多个圆环状的槽,滑动面具有包含该滑动面的中心的圆形的中央区域和位于比中央区域靠外侧处的第一环状区域,中央区域中的槽的宽度L2相对于槽的间距L1的比率R-(C)大于第一环状区域中的槽的宽度L2相对于槽的间距L1的比率R-(O1)。(A sliding member according to one aspect of the present invention includes a sliding surface that abuts an outer surface of a cam, and a spiral or plurality of annular grooves provided on the sliding surface, the sliding surface having a circular central region including a center of the sliding surface and a first annular region located outside the central region, and a ratio R of a width L2 of the groove in the central region to a pitch L1 of the groove C Greater than the ratio R of the width L2 of the slots in the first annular region to the spacing L1 of the slots O1 。)

1. A sliding member is provided with:

a sliding surface abutting against an outer surface of the cam; and

a spiral or a plurality of annular grooves provided on the sliding surface,

the sliding surface has a circular central region including a center of the sliding surface and a first annular region located outside the central region,

a ratio R of a width L2 of the slots in the central region to a pitch L1 of the slots_CA ratio R greater than a width L2 of the slots in the first annular region relative to a spacing L1 of the slots_O1。

2. The sliding member according to claim 1,

the grooves are formed such that the ratio of the width L2 to the pitch L1 becomes smaller stepwise or continuously as approaching the outer side from the center side of the sliding surface.

3. The sliding member according to claim 1 or 2,

the grooves are formed such that the distance L1 becomes larger stepwise or continuously as the distance from the center side of the sliding surface becomes closer to the outer side.

4. The sliding member according to any one of claims 1 to 3,

ratio R_CIs 0.2 to 0.8 inclusive.

5. The sliding member according to any one of claims 1 to 4,

ratio R_O1Is more than 0.1And 0.6 or less.

6. The sliding member according to any one of claims 1 to 5,

ratio R_C/R_O1More than 1 and 8 or less.

7. The sliding member according to any one of claims 1 to 6,

the groove is formed in a spiral shape, and the spiral groove is formed continuously or intermittently from one end portion to the other end portion.

8. The sliding member according to any one of claims 1 to 6,

the groove is formed in a plurality of annular shapes, and each of the annular grooves is formed continuously or intermittently in the circumferential direction.

9. The sliding member according to any one of claims 1 to 8,

the depth of the groove is 100-400 nm.

10. The sliding member according to any one of claims 1 to 9,

the sliding surface is formed of a hard coating.

11. The sliding member according to claim 10,

the hard coating is an amorphous hard carbon film.

12. The sliding member according to any one of claims 1 to 11,

the sliding surface further has a second annular region located outside the first annular region and along a peripheral edge of the sliding surface.

13. The sliding member according to claim 12,

of the grooves in the second annular regionRatio R of width L2 to spacing L1 of the slots_O2A ratio R less than a width L2 of the slots in the first annular region relative to a spacing L1 of the slots_O1。

14. The sliding member according to claim 13,

ratio R_O2Is 0.05 to 0.4 inclusive.

15. The sliding member according to claim 13 or 14,

ratio R_O1/R_O2More than 1 and not more than 12.

16. The sliding member according to claim 12,

no grooves are formed in the second annular region.

17. The sliding member according to any one of claims 1 to 16,

the sliding member is a valve lifter or a shim.

Technical Field

The present invention relates to a slide member which is in slide contact with a counterpart member.

Background

A sliding member such as a valve lifter is used in a valve drive mechanism provided in an internal combustion engine. The valve lifter is in sliding contact with the outer peripheral surface of the cam of the camshaft, and the rotation of the camshaft acts on the opening and closing of the valve. In order to reduce the friction loss of sliding parts, techniques for improving the retention of lubricating oil on the sliding surface have been studied (see patent documents 1 to 3).

Documents of the prior art

Patent document 1: japanese Kokai publication Sho-51-68904

Patent document 2: japanese laid-open patent publication No. 11-157954

Patent document 3: japanese laid-open patent publication No. 2007-46660

Disclosure of Invention

Problems to be solved by the invention

In recent years, for the purpose of further reducing friction, improving fuel economy, and the like, the viscosity of lubricating oil has been reduced. When a lubricating oil having a lower viscosity than conventional lubricating oils is used, there is still room for further improvement in the structure of the sliding surface such as a conventional valve lifter in order to maintain low friction loss at the sliding surface.

The invention provides a sliding component which can realize low friction loss on a sliding surface even under the condition of using low-viscosity lubricating oil.

Means for solving the problems

A sliding member according to an aspect of the present invention includes: a sliding surface abutting against an outer surface of the cam; and a spiral or a plurality of annular grooves provided on the sliding surface, the sliding surface having a circular central region including a center of the sliding surface and a first annular region located outside the central region, a ratio R of a width L2 of the groove in the central region to a pitch L1 of the groove_CGreater than the ratio R of the width L2 of the slots in the first annular region to the spacing L1 of the slots_O1. The sliding surface is formed of a hard coating such as an amorphous hard carbon film.

As described above, the spiral or annular grooves are formed in the central region and the first annular region of the sliding surface. Ratio R in the central region_CIs greater than the ratio R in the first annular region_O1This means that the grooves are formed relatively more densely in the central region, and on the other hand, the grooves are formed sparsely in the first annular region. With this configuration, according to the sliding member of the present invention, even when a low-viscosity lubricant is used, a sufficiently low friction loss can be set at the sliding surface. That is, by densely forming the grooves in the central region where the cam receives a relatively strong pressing force, a sufficient amount of the lubricating oil can be held in the central region, and the frictional resistance can be sufficiently reduced. On the other hand, since the pressing force applied to the first annular region from the cam is weaker than that applied to the central region, the friction resistance can be maintained in a sufficiently small state even if the grooves are formed more sparsely than the central region. If the grooves are formed densely in the first annular region to the same extent as in the central region, the frictional resistance is rather increased.

The groove may be formed such that the ratio of the width L2 to the pitch L1 becomes gradually smaller as the groove approaches the outer side from the center side of the sliding surface, or may be formed such that the groove becomes continuously smaller. That is, the sliding surface may transition from a region where the grooves are densely formed (central region) to a region where the grooves are sparsely formed (first region) in a stepwise manner as the sliding surface moves from the center side to the outer side, or may transition continuously. For example, when the groove width L2 is substantially constant, the grooves may be formed such that the pitch L1 becomes gradually or continuously larger as the distance from the center side of the sliding surface becomes outward.

When the groove is formed spirally, the spiral groove may be formed continuously from one end portion to the other end portion, or may be formed intermittently. When the grooves are formed in a plurality of annular shapes, the annular grooves may be formed continuously in the circumferential direction or intermittently.

The sliding surface may further include a second annular region located outside the first annular region and along a peripheral edge of the sliding surface. In the second annular region, the grooves may be formed more sparsely than in the first annular region. In the case of this mode, the ratio R of the width L2 of the groove in the second annular region to the pitch L1 of the groove_O2Is smaller than the spacing of the width L2 of the slot in the first annular region relative to the slotRatio R of L1_O1. Alternatively, no groove may be formed in the second annular region.

Effects of the invention

According to the present invention, a sliding member is provided that can achieve sufficiently low friction loss on a sliding surface even when a low-viscosity lubricating oil is used.

Drawings

Fig. 1(a) and 1(b) are sectional views showing a part of a valve mechanism of an internal combustion engine to which a sliding member according to an embodiment of the present invention is applied.

Fig. 2 is a sectional view showing the valve lifter shown in fig. 1.

Fig. 3 is a plan view schematically showing one embodiment of a groove formed in a sliding surface of a valve lifter.

Fig. 4(a) to 4(c) are enlarged cross-sectional views schematically showing grooves formed in the sliding surface.

Fig. 5 is a plan view schematically showing another mode of the valve lifter of the groove.

Fig. 6 is a plan view schematically showing another mode of the valve lifter of the groove.

Fig. 7 is a plan view schematically showing another mode of the valve lifter of the groove.

Fig. 8(a) and 8(b) are plan views schematically showing valve lifters of modified examples of the grooves.

Fig. 9 is a plan view schematically showing another mode of the valve lifter of the groove.

FIG. 10 is a graph showing the results of examples and comparative examples.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

< valve mechanism >

Fig. 1 shows a part of a valve train of an internal combustion engine to which a sliding member according to an embodiment of the present invention is applied. Fig. 1(a) is a cross section of a state where the valve lifter is raised and the valve is closed, and fig. 1(b) is a cross section of a state where the valve lifter is lowered and the valve is opened.

The valve lifter 10 shown in fig. 1(a) corresponds to the sliding member of the present embodiment, and is provided in the cylinder bore 22 of the cylinder head 20. The cam 24 that slides on the sliding surface 11 of the valve lifter 10 is attached to the camshaft and rotates with the rotation of the camshaft by a drive system or the like. Since the cam 24 has a cam profile in which the distance from the center of rotation to the outer peripheral sliding surface is not constant, the force pressing the sliding surface 11 of the valve lifter 10 changes due to the rotation of the cam 24. As shown in fig. 1(a) and 1(b), the valve lifter 10 moves in the cylinder bore 22 in accordance with the rotation of the cam 24, and the valve 26 connected to the valve lifter 10 is opened and closed. The valve 26 is constantly biased upward (toward the cam side) in the figure by a valve spring 28 disposed on the outer periphery. The opening operation of the valve 26 (see fig. 1 b) is performed when the protruding portion of the cam 24 presses the sliding surface 11. The cam 24 and the valve lifter 10 are lubricated by supplying lubricating oil from a lubricating oil supply unit (not shown) provided on the camshaft side. The force with which the cam 24 presses the valve lifter 10 is maximized when the protruding tip end portion (cam nose) of the cam 24 reaches the vicinity of the central region of the sliding surface 11. Further, as the rotation speed of the camshaft becomes higher, the sliding speed with the valve lifter 10 also increases.

< valve lifter >

Fig. 2 is a sectional view of the valve lifter 10, and fig. 3 is a plan view of the valve lifter 10. As shown in the above figures, the valve lifter 10 has a cylindrical shape with one side open, and specifically, includes a cylindrical skirt portion 12, a crown portion 13 integrally formed with the skirt portion 12 at one end side, i.e., an upper end portion, in the central axis X direction of the skirt portion 12, and an amorphous hard carbon film 15 provided on an upper surface (an end surface on the opposite side to the skirt portion 12 side) of the crown portion 13. A circular boss portion 14 is provided near the center of the lower surface (main surface on the skirt 12 side) of the crown portion 13. The boss portion 14 abuts an upper end (stem) of the valve 26. A tapered chamfered portion is formed at the boundary between the skirt portion 12 and the sliding surface 11.

As shown in fig. 3, the sliding surface 11 has a circular shape, and the cam 24 slides in the direction of the arrow S shown in fig. 3 in a partial region thereof (a sliding range Sa indicated by a broken line in fig. 3). That is, an arrow S indicates a sliding direction of the cam 24, and a contact point between the cam 24 rotating in one direction and the sliding surface 11 reciprocates in the direction along the arrow S. A sliding range Sa indicated by a broken line indicates a moving range of the cam 24 sliding along the arrow S. When sliding with the cam 24, the center position of the cam width may be set to a position slightly offset to the outer circumferential side from the center axis of the valve lifter crown surface for the purpose of rotating the valve lifter 10 around the center axis thereof in the cylinder bore 22, and the sliding range Sa of the cam may be slightly larger than the cam width in consideration of the offset.

The sliding surface 11 of the present embodiment is formed of a hard coating such as a metal nitride, carbide, carbonitride, boride, hard plating layer, or amorphous hard carbon film by Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD). The sliding surface 11 is preferably formed of an amorphous hard carbon film 15. The material of the body portion (skirt portion 12, crown portion 13, and boss portion 14) of the valve lifter 10 may be a carburized material of an SCM material based on JIS standards, or may be other steel materials, castings, iron-based alloys, titanium alloys, aluminum alloys, high-strength resins, and the like.

As shown in fig. 3, a spiral groove 16 is formed in the sliding surface 11, centering on a central axis X (hereinafter, simply referred to as "axis X") of the sliding surface 11. The groove 16 is formed continuously from an end portion on the outer peripheral side of the sliding surface 11 to an end portion in the central portion (near the axis X). The grooves 16 may be formed by irradiating the amorphous hard carbon film 15 with laser light. For example, the laser beam is irradiated from the outer peripheral side to the center side of the sliding surface 11 in the radial direction while the valve lifter before the groove 16 is formed is rotated around the axis X. At this time, the groove 16 shown in fig. 3 can be formed by controlling the rotation speed of the valve lifter, the moving speed of the laser beam, the irradiation intensity of the laser beam, and the like. Examples of usable laser light include an ultra-short pulse laser and a linearly polarized laser. As the laser for forming the groove 16, an ultrashort pulse laser having a pulse interval of picoseconds to femtoseconds is preferably used.

The sliding surface 11 is divided into, for example, three regions from the central portion to the peripheral portion according to the form of the groove 16. That is, the sliding surface 11 has a circular central region Ac including the center of the sliding surface 11, a first annular region a1 located on the outer side of the central region Ac, and a second annular region a2 located on the outer side of the first annular region a 1. The central region Ac is circular and preferably has a diameter corresponding to the width of the sliding range Sa of the cam (width W in fig. 3). That is, the diameter of the central region Ac is preferably equal to or larger than the width W. The first annular region a1 is a region between the central region Ac and the second annular region a 2. The second annular region a2 is a region along the peripheral edge of the sliding surface 11.

As shown in fig. 3, the grooves 16 are formed more densely in the central region Ac than in the first annular region a 1. That is, as shown in fig. 4(a) and 4(b), the ratio R of the width L2 of the groove in the central region Ac to the pitch L1 of the groove 16_CGreater than the ratio R of the width L2 of the slots in the first annular region A1 to the spacing L1 of the slots_O1. In the present embodiment, the width L2 of the grooves 16 is substantially constant, and the pitch L1 of the grooves 16 in the central region Ac is set smaller than the pitch L1 of the grooves in the first annular region a 1. The width L2 of the groove 16 is, for example, 20 to 200 μm, or 50 to 160 μm or 80 to 120 μm. From the viewpoint of reducing friction in the low rotation region, the depth of the groove 16 is preferably 100 to 400nm, and may be 100 to 300nm or 150 to 250 nm.

Ratio R of grooves 16 in the central region Ac_CFor example, the concentration of the metal oxide is 0.2 to 0.8, and may be 0.3 to 0.7 or 0.4 to 0.6. By making the ratio R of the central region Ac_CThe lubricating oil content of 0.2 or more facilitates the retention of the lubricating oil in the central region Ac, while the content of 0.8 or less suppresses the increase in sliding resistance due to excessive lubricating oil.

Ratio R of slots 16 in first annular region a1_O1Less than the above ratio R_C. Ratio R of the first annular region A1_O1For example, the concentration of the metal oxide is 0.1 to 0.6, and may be 0.1 to 0.5 or 0.2 to 0.4. By making the ratio R of the first annular region A1_O1When the amount is 0.1 or more, the lubricant oil is easily retained in the first annular region a1, while when the amount is 0.6 or less, the increase in the sliding resistance due to the excessive lubricant oil can be suppressed. Ratio R_C/R_O1For example, the content is more than 1 and 8 or less, and may be 1.1 to 3.

As shown in fig. 4(b) and 4(c), the ratio R of the width L2 of the grooves in the first annular region a1 to the pitch L1 of the grooves 16₀₁Greater than the ratio R of the width L2 of the slots in the second annular region A2 to the spacing L1 of the slots_O2. As described above, the width L2 of the grooves 16 is substantially constant, and the pitch L1 of the grooves 16 in the first annular region a1 is set smaller than the pitch L1 of the grooves in the second annular region a 2. Ratio R of the second annular region A2_O2For example, the content is 0.05 to 0.4, and may be 0.1 to 0.4 or 0.2 to 0.3. By making the ratio R of the second annular region A2_O2Being 0.4 or less, the increase in sliding resistance due to excessive lubricating oil can be suppressed. Ratio R_O1/R_O2For example, the content is more than 1 and not more than 12, and may be 1.1 to 3.

The cross-sectional shape of the groove 16 is not particularly limited. For example, as shown in fig. 4(a) to 4(c), the side surface and the bottom surface may be continuous in a curved shape, or may be clearly divided into side surfaces and bottom surfaces. The groove 16 may have a V-groove shape formed on both sides.

The hard coating constituting the sliding surface 11 can be formed of a nitride, carbide, carbonitride of a metal such as Ti or Cr, a boride such as BN, a hard Cr plating layer, an amorphous hard carbon film, or the like by Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD), and is particularly preferably formed of an amorphous hard carbon film. Amorphous hard carbon is called diamond-like carbon (DLC), hydrogenated amorphous carbon (a-c: H), i-carbon, diamond-like carbon, or the like, and the bond (sp) of diamond structure is bonded to carbon in the structure³Type bond) and graphite structure (sp)²Type bonds) are present in admixture. By forming the sliding surface 11 with the amorphous hard carbon film 15, wear of the sliding surface 11 accompanying sliding with the cam 24 can be suppressed, performance degradation of the valve lifter 10 can be prevented, and the service life of the valve lifter 10 can be increased.

The thickness of the amorphous hard carbon film 15 is, for example, 0.4 to 10 μm. If the thickness of the amorphous hard carbon film 15 is 0.4 μm or more, the valve lifter 10 has sufficient durability. On the other hand, if the thickness of the amorphous hard carbon film 15 is 10 μm or less, it is possible to suppress an excessive increase in internal stress in the film, and to easily suppress occurrence of chipping and peeling. The thickness of the amorphous hard carbon film 15 may be 0.7 to 2.0 μm from the viewpoint of productivity of the valve lifter 10. The depth of the groove provided on the sliding surface is set to be smaller than the thickness of the amorphous hard carbon film.

The amorphous hard carbon film 15 can be formed, for example, by using an arc ion plating apparatus having a graphite cathode in an evaporation source. According to this apparatus, the amorphous hard carbon film 15 can be formed through a process of generating vacuum arc discharge between the graphite cathode and anode in a vacuum atmosphere, evaporating and ionizing the carbon material from the surface of the carbon anode, and depositing carbon ions on the upper surface of the crown portion 13 to which a negative bias voltage is applied.

The amorphous hard carbon film 15 may or may not contain hydrogen, but preferably does not substantially contain hydrogen (hydrogen content is less than 5 atomic%) from the viewpoint of achieving a low friction coefficient. Specifically, the hydrogen content of the amorphous hard carbon film 15 is preferably less than 5 atomic%, more preferably less than 3 atomic%, still more preferably less than 2 atomic%, and particularly preferably less than 1 atomic%. If the amorphous hard carbon film 15 does not substantially contain hydrogen, it is confirmed that the dangling bonds of the carbon atoms on the surface of the amorphous hard carbon film 15 are not terminated by hydrogen, and thus the oily agent-constituting molecules having OH groups in the lubricating oil are easily adsorbed on the surface of the amorphous hard carbon film 15, thereby exhibiting an extremely low friction coefficient. In addition, amorphous hard carbon containing substantially no hydrogen has excellent heat conduction characteristics. The Hydrogen content of the amorphous hard carbon film 15 can be measured by Rutherford Backscattering Spectroscopy (RBS), Hydrogen Forward Scattering spectroscopy (HFS).

In order to form the amorphous hard carbon film 15 containing substantially no hydrogen, the film formation may be performed without introducing a carbon-based gas. Further, the water remaining on the wall surface in the device may contain less than 5 atomic% of hydrogen. Water droplets characteristically formed in the arc ion plating enter the amorphous hard carbon film 15 to reduce the film strength. By using a filter arc type device equipped with a magnetic filter, water droplets can be reduced. The amorphous hard carbon film 15 formed by using this apparatus has sufficiently small water droplets, is sufficiently homogeneous, and has excellent wear resistance.

The embodiments of the present invention have been described above in detail, but the present invention is not limited to the above embodiments. For example, in the above-described embodiment, the spiral groove 16 continuously formed from one end portion to the other end portion is exemplified, but the groove 16 may be formed intermittently. The grooves may not be spiral, and instead of the spiral grooves 16, a plurality of concentric grooves 17 may be formed on the sliding surface 11 as shown in fig. 5. The plurality of annular grooves 17 may be formed continuously in the circumferential direction or intermittently.

In the above embodiment, the second annular region a2 has the grooves 16 formed more sparsely than the first annular region a1, but the grooves may not be formed in the second annular region a2 (see fig. 6), or the grooves 16 may be formed more continuously and sparsely than the first annular region a1 (see fig. 7). The form of the second annular region a2 may be appropriately selected depending on the type and viscosity of the lubricating oil.

In the above embodiment, the groove 16 is formed to the vicinity of the central axis X of the central region Ac (see fig. 3 and 6), but as shown in fig. 8 a and 8 b, an unprocessed portion of the groove may be locally provided in the vicinity of the central axis X of the central region Ac. That is, the central region Ac may have a central portion Ax where no groove is formed. This is because the central portion Ax can easily hold the lubricating oil without forming the groove 16 or the groove 17. The groove 16 or the groove 17 is not formed in the central portion Ax, so that the processing is easy. The ratio of the diameter of the central portion Ax to the diameter of the central region Ac is, for example, 0.1 to 0.6, or 0.15 to 0.5. The form of the central region Ac may be appropriately selected depending on the type and viscosity of the lubricant oil.

In the above embodiment, the form in which the sliding surface 11 has the second annular region a2 is exemplified, but the sliding surface 11 may not have the second annular region a 2. In this case, the first annular region a1 extends from the peripheral edge of the central region Ac to the peripheral edge of the sliding surface 11.

As shown in fig. 3 and 5 to 8, the pitch of the grooves 16 may be different in stages when the transition from the central region Ac to the first annular region a1 is made, but the pitch of the grooves 16 may be continuous (see fig. 9). Examples of the curve drawn by the groove 16 shown in fig. 9 include an involute curve (expansion line) and a logarithmic spiral. In the case where the pitch of the grooves 16 is continuously widened, the boundary between the central region Ac and the first annular region a1 is not necessarily clear, but the boundary between the central region Ac and the first annular region a1 may be defined based on the width of the sliding range Sa of the cam (width W in fig. 3). For example, a circular region having the same diameter as the width W may be defined as the central region Ac. Alternatively, the boundary of the width L2 and the pitch L1 may be defined based on the ratio of the width L2 to the pitch. For example, a region where the ratio is 0.5 or more may be set as the central region Ac, and a region outside a point where the ratio is less than 0.5 may be set as the first annular region a 1.

In the above embodiment, the valve lifter is exemplified as the sliding member, but the sliding member according to the present invention may be applied to other members such as a spacer of a cam follower member and a lifter.

Examples

The present invention will be described below based on examples. The present invention is not limited to the following examples.

< example >

A valve lifter having the same structure as that shown in fig. 3 except that the sliding surface is composed of the central region and the first annular region and does not have the second annular region was produced. The valve lifter of the present embodiment has the following configuration.

Material of the sliding surface: amorphous hard carbon film (hydrogen content: less than 5 atomic%)

Diameter of sliding surface: 29mm

The form of the groove: continuous helical shape

Depth of groove: 0.2 μm

Groove spacing L1: 0.2mm (central zone), 0.3mm (first annular zone)

Width of groove L2: 0.1mm

Central region: to a radius of 6mm

First annular region: area from 6mm to 14.5mm of radius

Ratio R of the central region_C(L2/L1)：0.5

The ratio R of the first annular region_O1(L2/L1)：0.33

Groove processing method: laser machining

< comparative example 1 >

A valve lifter was produced in the same manner as in the example, except that grooves were formed at regular intervals on the sliding surface. The groove of the comparative example has the above-described form.

The form of the groove: continuous helical shape

Depth of groove: 0.2 μm

Groove spacing L1: 0.2mm

Width of groove L2: 0.1mm

Ratio (L2/L1): 0.5

< comparative example 2 >

A valve lifter was produced in the same manner as in the example, except that no groove was formed in the sliding surface.

< confirmation of Friction reducing Effect >

The outer surface of the cam was slid against the sliding surface of the valve lifter of comparative example 2, and the torque (Nm) of the camshaft was measured. The rotational speed of the camshaft is varied stepwise from 200rpm to 2500 rpm. Similarly, the torque of the camshaft was measured using the valve lifters of example and comparative example 1, respectively. Fig. 10 graphically shows the friction reduction rate (%) calculated by the following formula.

Friction reduction ratio (%) ("torque of comparative example 2) - (torque of example or comparative example 1) ]/(torque of comparative example 2) × 100

As shown in the graph of fig. 10, the embodiment obtains a friction reduction effect superior to that of the comparative example 1 over the entire range of the rotation speed of the camshaft from 200rpm to 2500 rpm.

Industrial applicability

According to the present invention, a sliding member is provided that can achieve sufficiently low friction loss on a sliding surface even when a low-viscosity lubricating oil is used.

Description of the reference numerals

11 … sliding surface, 15 … amorphous hard carbon film, 16 … spiral groove, 17 … circular groove, 24 … cam, Ac … central region, a1 … first circular region, a2 … second circular region.