JP2001130975A - Ceramic sliding part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramic sliding part attaining sufficient one-side hitting performances even under a severe use condition, having excellent fatigue- resistant performances. SOLUTION: A sliding end face 4a of a ceramic plate 4 is subjected to a curved crowning having a central side projecting from a standard level (f) of the end face with regarding a plane (f) including an outer edge 7 as the standard face of the end face. The radius of curvature of the crowning is different depending upon the position of the sliding face end 4a. When a distance from a central point 6 of the sliding end face 4a to the outer edge 7 is D, a position separated by 0.8D from a central point 6 is a boundary, a peripheral part 4b exists at an outer peripheral side, a central part 4d exists at a central side, an average value of the radius of curvature of the peripheral part 4b is R1 and an average value of the central part 4d is R2, a relation of the formula R1<R2 is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic slide suitable for a sliding part of a valve train such as a tappet, a rocker arm and a valve bridge of an internal combustion engine, and a piston of a hydraulic circuit operated by using an engine drive system. The present invention relates to a moving part and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, the number of sliding parts such as those described above has been increasing in which the sliding surface is formed of a ceramic member having excellent wear resistance. For example, mechanical sliding parts represented by engine parts for automobiles are used. In some cases, the cam sliding surface is formed of a ceramic body. Such mechanical sliding parts often form a convex crowning on the sliding surface in order to cause the parts to rotate during sliding for the purpose of preventing uneven wear or the like due to partial contact. The present inventors have also disclosed, for example,
In Japanese Patent Application Laid-Open No. 3-225728, wear-resistant parts (specifically, ceramics such as silicon nitride) having a smaller coefficient of thermal expansion than a joining base material (specifically, a metal body such as steel) are provided on a sliding surface. A method for forming a crowning shape on a sliding surface by heat differential bonding is disclosed.

[0003]

Problems to be Solved by the Invention
As the speeding-up progresses, the use environment of sliding parts such as tappets composed of the above-mentioned joints is becoming increasingly severe, and joints with higher durability are required. According to the study of the present inventors, in the case of a sliding component that has been crowned due to a difference in thermal expansion at the time of joining a metal body and a ceramic body, it is assumed that the sliding component is used under the above-described extremely severe conditions. It has been found that due to variations in crowning profiles among product lots, problems such as not necessarily exerting the effect of preventing the one-sided hitting or the durability performance of the ceramic body are likely to occur. .

[0004] For example, if the crowning is small (the radius of curvature of the sliding surface is large), it is not possible to prevent the originally intended one-sided contact. Since the contact area decreases and the surface pressure increases, there is a problem that the mating member is attacked and the mating member is worn, particularly when the sliding surface is formed of a ceramic body. Also, in the case of a tappet in which a ceramic body constituting a cam sliding surface is brazed to a metal body, if a partial contact with the cam occurs, stress concentrates on an outer peripheral portion of the ceramic body as the cam slides. ,
There is a problem that an outer peripheral portion of the ceramic body is chipped or a brazed portion is deformed, so that cracks and peeling are likely to occur from a bonding interface as a base point.

[0005] An object of the present invention is to control the amount of crowning formed under appropriate conditions to achieve a sufficient effect of preventing crowning by imparting crowning even under severe use conditions. An object of the present invention is to provide a ceramic sliding component capable of suppressing wear and the like.

[0006]

Means for Solving the Problems and Actions / Effects In a ceramic sliding part, the contact between the sliding end face and the mating member is one of the factors that greatly influence the durability of the sliding end face formed by the ceramic body. Can be Therefore, crowning is applied to the sliding end face in order to prevent one-side contact at the sliding end face. However, as a ceramic sliding part, for example, when a tappet whose sliding end surface is a cam sliding surface is considered, the processing accuracy of a block hole on the engine side to which the tappet is assembled and the processing accuracy of a cam as a mating member (for example, a cam taper) And cam width), there is a concern that the cam may hit the edge (single contact) on the outermost periphery of the cam sliding end surface.
The crowning formation amount must be determined by assuming the upper limit of the intersection of the processing accuracy. Therefore, it is necessary to increase the amount of formation of the crowning, in other words, to reduce the radius of curvature of the crowning to prevent one-side contact. However, as the amount of crowning increases, the surface pressure between the cam and the cam sliding surface increases, and the sliding end surface is formed of a ceramic body having excellent mechanical strength. To cause wear such as uneven wear and pitching. The inventors of the present invention have conducted intensive studies, and as a result, one-sided contact with the mating member is affected by the amount of crowning formed near the outer edge of the sliding end face, while the attack on the mating member due to an increase in surface pressure is reduced. It has been found that these factors depend on the amount of crowning formed near the center of the sliding end face, and that these factors can occur because the radius of curvature of the crowning is formed almost uniformly. The invention was completed.

In other words, according to the structure of the ceramic sliding component of the present invention, in a ceramic sliding component having a sliding end face made of ceramic, the sliding end face is formed by using a plane including the outer edge as an end face reference plane. A curved crowning whose central side protrudes from the end surface reference surface is formed, a boundary point is defined at an arbitrary point on the sliding end surface that is separated from the center point, and the boundary point is defined as an outer edge from the boundary point within the sliding end surface. When the portion toward the center is defined as the peripheral portion, and the portion toward the center from the boundary point is defined as the center, the average value R1 of the radius of curvature of the crowning corresponding to the peripheral portion is the average value R2 of the radius of curvature of the crowning corresponding to the central portion. Satisfies the relationship of R1 <R2.

As described above, by adopting a structure in which the average value of the radius of curvature of the crowning is adjusted (changed) at a predetermined point on the sliding end surface, it is possible to prevent the one-sided contact with the counterpart member. In addition, it is possible to effectively suppress an attack or the like on a mating member due to an increase in surface pressure, and to provide a ceramic sliding component having excellent slidability.

Specifically, it is preferable that a distance between the center point and the outer edge of the sliding end face in a direction parallel to the end face reference plane be D, and a position corresponding to 0.8D from the center point be a boundary point. For example, when the ceramic sliding component is used as a tappet, the load tends to be higher on the peripheral side than at 0.8D during high-speed rotation, so that the average value of the radius of curvature of the crowning is set at 0.8D as a boundary. The adjustment should be made as described above.

The radius of curvature of the crowning is 0.8D.
May change discontinuously (in two stages) or continuously in a radial section including at least 0.8D. In this case, 0.8
At the position D, a smoother sliding end face can be formed. It is also possible to continuously change the radius of curvature of the crowning over the entire sliding end face.

It is preferable that R1 and R2 satisfy the relationship of 5 × R1 <R2. By giving such a difference in the average value of the radii of curvature of the crowning, even under severe use conditions, the effect of preventing an attack on a partner member due to an increase in surface pressure, and a sufficient effect of preventing the one-side hit by the crowning become more remarkable. In addition, it is possible to provide a ceramic sliding component having extremely excellent slidability and durability.

On the other hand, the surface roughness of the sliding end face can be made greater at the peripheral portion than at the central portion. Since the peripheral portion of the sliding end face subjected to the above-mentioned crowning has few opportunities to come into contact with the mating member, the surface roughness of this portion can be made larger than that of the central portion. In this case, in a manufacturing process such as polishing to be described later, the processing efficiency in the peripheral portion is improved, which is economical. Further, the effect of retaining oil such as lubricating oil in the peripheral portion having a rough surface is also achieved. It is preferable that the center has a small roughness due to a sliding effect.
In addition, the surface roughness referred to here is an arithmetic average roughness defined in JIS-B0601, and the cutoff value and the evaluation length are measured by adopting the values recommended by the JIS. Say.

The ceramic forming the sliding end face can be brazed to a metal body through a brazing material layer, for example, but other methods such as friction welding may be used.

As a method of adjusting the radius of curvature of the sliding end face of the ceramic body as described above, there is a method of increasing the thickness of the ceramic body at the central portion and decreasing the thickness at the peripheral portion. In order to form such a sliding end face shape, for example, there is a method of grinding the sliding end face. In this case, for example, in a flat plate-shaped ceramic body, the peripheral portion thereof is subjected to more grinding to form a crowning larger than the central portion, while the central portion is formed to be smaller than the peripheral portion to form a crowning. If the grinding is performed less than the peripheral portion, the thickness of the ceramic body is increased at the central portion and reduced at the peripheral portion as described above. In addition, the thickness referred to here indicates a distance in a direction orthogonal to the end face reference plane.

As a method of crowning the sliding end surface of the ceramic body, there is a method of utilizing a difference in thermal expansion between the ceramic body and the metal body to be brazed. In this case, in order to increase the radius of curvature of the central portion, the metal body and the ceramic body are joined by brazing the portion facing the peripheral portion of the sliding end surface in the joining surface, and the center of the sliding end surface is joined. The part facing the part can be non-joined. On the other hand, between the metal body and the ceramic body, a cushioning member having a smaller area than the joint surface between them is arranged at a position facing the center of the sliding end surface, and the cushioning member does not exist in the joint surfaces. In the remaining portion, the metal body and the ceramic body can be brazed and joined, while the joining surfaces opposed to the central portion can be brazed to each other via a cushioning member. In this case, since the thermal stress is relaxed at the joint surface opposite to the central portion where the cushioning member is arranged, the radius of curvature of the crowning formed at the central portion is
It becomes larger than the peripheral part which is not affected by the cushioning member. The cushioning member can be composed mainly of a soft metal such as Cu or Ni, for example, and has a function of relaxing the thermal stress by its own plastic deformation. Further, the buffer member may be made of a material such as W alloy or Kovar having a linear expansion coefficient between the ceramic part and the metal body part.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an overhead valve mechanism using a tappet as a ceramic sliding component of the present invention. The tappet 1 and the push rod 103 move up and down by the rotation of the cam 100, and open and close the valve 101 via the rocker arm 102. FIG. 2 is an enlarged view of the tappet 1. The tappet 1 includes a metal body (hereinafter, also referred to as tappet fitting) 2 and a ceramic body (hereinafter, also referred to as ceramic plate) via a brazing material layer 3.
4 has a structure in which its central axes are almost coincident with each other. The tappet fitting 2 is made of an iron-based material, and has an axial push rod insertion hole 1c at one end side of the main body 1a having a circular cross section, and the main body 1a at the other end. Also has a shape in which the large-diameter sliding base portion 1b is integrally formed. On the other hand, the ceramic plate 4 is formed in a disc shape as a sintered body of silicon nitride, and is overlapped and joined to the flat distal end surface of the sliding base 1b. In addition, brazing material layer 3
Is used as a brazing material. The end face of the ceramic plate 4 opposite to the side in contact with the brazing material layer 3 is a sliding end face 4 a with the cam 100.

The sliding end face 4a of the ceramic plate 4 has
As shown in an exaggerated manner, a curved surface crowning (small curvature with a central portion protruding) whose central side protrudes from the end surface reference surface f is provided with a plane f including the outer edge 7 as an end surface reference surface. . The radius of curvature of the crowning is
It depends on the position of the sliding end face 4a. Specifically, the distance from the center point 6 of the sliding end face 4a to the outer edge 7 in the direction parallel to the end face reference plane f is D, and the distance is 0.8D from the center point 6. A position is defined as a boundary point, a portion of the sliding end face from the boundary point toward the outer edge 7 is defined as a peripheral portion 4b, a portion from the boundary point toward the center point 6 is defined as a central portion 4d, and a radius of curvature of the peripheral portion 4b. It is assumed that R1 <R2, where R1 is the average value of R and R2 is the average value of the radius of curvature of the central portion 4d. More specifically, the relationship of R1 × 5 <R2 is satisfied. For example, in the case of this embodiment, R1 is about 2500 mm,
2 is about 20,000 mm.

Such a crowning shape is formed by grinding as described below, and the amount of grinding is increased in the peripheral portion 4b to form a crowning having a small radius of curvature, and conversely, in the central portion 4d. The amount has been reduced. Therefore, the thickness of the ceramic plate 4 (the distance in the direction orthogonal to the end face reference plane f) is large at the central portion 4d and small at the peripheral portion 4b.

The average values R1 and R2 of the radii of curvature of the central portion 4d and the peripheral portion 4b change continuously in a radial section including at least 0.8D. That is, in the section including 0.8D, the sliding end face 4
No step is formed on a, and a smooth sliding surface is formed. On the other hand, the surface roughness of the sliding end face 4a is larger in the peripheral part 4b than in the central part 4d in consideration of the sliding efficiency and the like.

Next, as the Fe-based material constituting the metal body 2, various types of carbon steel, alloy steel (including stainless steel or heat-resistant steel), or cast iron can be used. For example, JIS
The following can be exemplified (the unit of the composition is% by weight). (1) Ni-Cr-Mo steel for machine structure: SNCM630
(C: 0.25 to 0.35, Si: 0.15 to 0.3
5, Mn: 0.35 to 0.60, Ni: 2.5 to 3.
5, Cr: 2.5 to 3.5, Mo: 0.5 to 0.7, residual Fe (unit: wt%, the same applies hereinafter)), SNCM439
(C: 0.36-0.43, Si: 0.15-0.3
5, Mn: 0.6 to 0.90, Ni: 1.6 to 2.0,
Cr: 0.6 to 1.0, Mo: 0.15 to 0.3, residual F
e), SNCM447 (C: 0.44-0.50, S
i: 0.15 to 0.35, Mn: 0.6 to 0.90, N
i: 1.6 to 2.0, Cr: 0.6 to 1.0, Mo:
0.15 to 0.3, residual Fe) and the like. (2) Cr-Mo steel for machine structure: SCM445 (C: 0.
43 to 0.48, Si: 0.15 to 0.35, Mn:
0.6-0.85, Cr: 0.9-1.2, Mo: 0.
15-0.3, residual Fe) and the like. (3) Cr steel for machine structure: SCr440 (C: 0.43 ~
0.48, Si: 0.15 to 0.35, Mn: 0.6 to
0.85, Cr: 0.9-1.2, residual Fe), SCr4
15 (C: 0.13-0.18, Mn: 0.60-0.
85, Cr: 0.90 to 1.20, residual Fe (unit:% by weight)) and the like. (4) Carbon steel for machine structure: S50C (C: 0.47-0.
53, Mn: 0.6-0.9, residual Fe) and the like.

The ceramic body 4 can be mainly composed of, for example, silicon nitride. Silicon nitride has excellent mechanical strength, abrasion resistance and corrosion resistance.
Sufficient strength and durability can be ensured even in a valve train sliding component used in a high temperature, high load, corrosive and severe environment. Note that, other than silicon nitride, sialon, silicon carbide, aluminum nitride, and the like can also be used.

The brazing material for forming the brazing material layer 3 may be an Ag-based brazing material containing Ag as a main component. Ag-based brazing filler metals usable in the present invention include Ag
-Cu-Ti-based brazing material (Cu: 20 to 40, Ti: 0.
5-4, balance Ag (unit: wt%, the same applies hereinafter)), Ag
-Cu-In-Ti-based brazing material (Cu: 15-30, I
n: 8 to 15, Ti: 0.5 to 4, and the balance Ag). The thickness of the brazing material layer when using an Ag-based brazing material is as follows:
It is preferable to adjust in the range of 5 to 60 μm. Thickness 60
If it exceeds μm, the bonding strength may be reduced. On the other hand, if the thickness is less than 5 μm, it may lead to poor bonding (insufficient bonding area ratio).

On the other hand, if a Cu-based brazing material containing Cu as a main component is used, the heat resistance of the brazing material layer, and the high-temperature bonding strength of the joined body can be further increased. By using a Cu-based brazing material containing 80% by weight or more of Cu, a joined body particularly excellent in heat resistance of a joined portion can be obtained. As a Cu-based brazing material, specifically, Cu
-Al-Si-Ti-based brazing material can be used. By setting the content of Cu to 80% by weight or more as described above, the heat resistance of the brazing material layer becomes particularly good. Al mainly serves to adjust the melting point of the brazing material, and the higher the content, the lower the melting point of the brazing material. On the other hand, Si enhances the flowability of the liquid phase formed by melting the brazing material, and contributes to the formation of a joint structure with few defects such as voids. However, if the Si content is less than 0.1% by weight, the effect of improving the fluidity of the liquid phase becomes poor, and if it exceeds 8% by weight, the brazing material layer becomes brittle, which may lead to a decrease in bonding strength.

The active metal component Ti (Zr or Hf
Exceeds 10% by weight), the amount of interfacial reaction products with the ceramic body (the object to be bonded) increases, and the bonding strength decreases. Therefore, the content of the active metal is preferably 10% by weight or less. Is preferably adjusted within a range of 5% by weight or less. The content of Al is appropriately adjusted in the range of 0.1 to 5% by weight in consideration of the content of Si and the active metal component and the target melting point (solidus temperature) of the brazing material. In addition, other Cu-based brazing materials include Cu-Pd-Si-T
i-based, Cu-Si-Ti-based, Cu-Si-based and the like can be used.

When a Cu-based brazing material is used, the thickness of the brazing material layer is preferably adjusted within the range of 30 to 100 μm. If the thickness exceeds 100 μm, the bonding strength may be reduced. On the other hand, if the thickness is less than 30 μm, it may lead to poor bonding (insufficient bonding area ratio).

Incidentally, each adjacent boundary (or bonding interface) between the brazing material layer 3 and the metal body 2 or the ceramic body 4 is often unclear due to component diffusion or the like. More specifically, a diffusion layer or a reaction layer (hereinafter, collectively referred to as diffusion /
Reaction layer). In the present specification, as shown in FIG. 4, in the joining direction of the metal body and the ceramic body, the cation component having the highest content among the cation components such as metal ions or silicon ions constituting the ceramic body (hereinafter, referred to as When the concentration of the main cation component is analyzed from the ceramic body side to the brazing material layer side, the position where the analysis value level of the main cation component concentration becomes 1/2 of the average concentration Cm is defined as the ceramic body. It shall be determined as the boundary BX with the brazing material layer. Similarly, when the concentration of the metal component having the highest content (hereinafter, referred to as a main metal component) among the metal components constituting the metal body is analyzed from the metal body side toward the brazing material layer side, the main metal component The position at which the analytical value level of the concentration is の of the average concentration Mm is determined as the boundary BY between the metal body and the brazing material layer. Then, the distance between the two boundaries is defined as the thickness t of the brazing material layer (however, if a distribution occurs in the thickness of the brazing material layer, the average value thereof is used).
Such analysis is performed by a known method such as electron probe microanalyzer (EPMA), EDS (energy dispersive X-ray spectroscopy) and WDS (wavelength dispersive X-ray spectroscopy), and Auger electron spectroscopy (AES). Can be implemented.

In the present invention, the shape of the tappet is not limited to that shown in FIG. For example, as shown in FIG. 5A, the push rod insertion hole 2c is
(b).
As shown in (1), the main body 2a and the sliding base 2b may have substantially the same diameter, and the whole may be configured in a cup shape. Further, as long as the sliding portion is formed of ceramic, it can be applied to a sliding component other than the tappet.

Hereinafter, a method for forming the crowning shape of the tappet 1 will be described. First, a metal body 20 having a flat joining surface and a ceramic body 40 having a flat sliding surface and a flat joining surface corresponding to an end surface opposite to the sliding end surface are brazed and joined, as shown in FIG. The joined body 100 with the brazing material layer 30 interposed therebetween is obtained. Next, grinding is performed on the sliding end surface 40a of the obtained joined body 100. Processing is as shown in FIG.
As shown in FIG. 5, spherical edge crowning can be performed on the sliding end surface using a cylindrical grindstone (hereinafter, also referred to as a cup grindstone) 50. Specifically, the cup grinding stone 5
The central axis O2 of 0 is inclined at a predetermined angle with respect to the central axis O1 of the joined body 100, and both are relatively approached while rotating both about their own central axes,
This is performed by grinding on the end face of the cup grindstone 50. By appropriately changing the angle θ, it is possible to obtain spherical surfaces having various radii of curvature. The larger the angle θ, the smaller the radius of curvature.

Specifically, first, as shown in FIG.
The angle θ1 is set to 1.5 ° ≦ θ1 ≦ 2.0 °, and spherical processing with a relatively small radius of curvature (corresponding to R1) is performed by the grindstone 50 (for example, grain size ♯800) around the sliding end face 40a. Apply to the part. Thereafter, as shown in FIG.
2 is an angle smaller than θ1, 1.0 ° ≦ θ2 <1.5 °
Is set, and spherical processing is performed on the center of the sliding end face with a relatively large radius of curvature (corresponding to R2) by the grindstone 50.

For example, when θ1 is 1.5 ° and the particle size is # 80
By using the whetstone 50 of 0, the radius of curvature R1 is approximately 2500 mm and the arithmetic average roughness R
a is formed about 0.1 μm, while θ2 is 1.
By using the grindstone 50 having a grain size of # 2500 at 0 °, the radius of curvature R2 is about 20,000 at the center 4d.
mm, a spherical surface having an arithmetic average roughness Ra of about 0.03 μm is formed, and a crowned tappet 1 as shown in FIG. 2 is obtained. In addition to the angle θ being changed in two stages as described above, the angle is continuously changed between θ1 and θ2, and the radius of curvature continuously changes from R1 to R2 at the sliding end face. It is also possible to perform spherical processing.

In addition to the above-described grinding, a crowning shape as shown in FIG. 2 can be formed by the following method. For example, as shown in FIG. 7, a buffer plate (buffer member) 60 can be inserted between the metal body 20 and the ceramic body 40 and brazed. The buffer plate 60 is made of a material mainly composed of a soft metal such as Cu or Ni.
At the time of cooling after brazing, etc., it functions to reduce thermal stress generated between the metal body 20 and the ceramic body 40. Note that the buffer plate 60 may be made of a material having an intermediate linear expansion coefficient between the ceramic body 40 and the metal body 20, such as a W alloy or Kovar.

The cushioning plate 60 is brazed to the concave portion 21 formed at the center of the joining end face of the metal body 20 via the metal-side brazing material layer 31 and installed. Then, the joining end face 22 in which the concave portion 21 is not formed in the metal body 20
, The ceramic body 40 is brazed through the brazing material layer 30. In addition, the brazing material layer 30 is also brazed to the ceramic body 40 side of the buffer plate 60 via the brazing material layer 30. In this way, the tappet 1 brazed and joined via the buffer plate 60 has a sliding end face of the ceramic body 4 having a crowning shape as shown in FIG. 7B. That is, the buffer plate 6
The sliding end face 4d in the central part where the
The thermal stress is relaxed by this, so that a crowning having a large radius of curvature (average value of the radius of curvature) is formed.
The sliding end face 4b of the peripheral portion where 0 is not installed is greatly affected by the thermal stress, and a crowning having a small radius of curvature (average value of the radius of curvature) is formed. In the present embodiment, the buffer plate 60 is provided by providing the concave portion 21 in the metal body 20. However, the buffer plate may be provided by providing the concave portion in the ceramic body 40. In FIG. 7, the thickness of the brazing material layer is exaggerated.

Further, as shown in FIG. 8, the above-mentioned crowning shape is formed by brazing and joining the peripheral portion side and the central portion side of the joining surface of the metal body 20 and the ceramic body 40 to each other. It is also possible. In particular,
A convex portion 33 protruding from the joint end surface is provided at the center of the joint end surface of the metal body 20, and brazing is performed only on the outer periphery of the convex portion 33. In the tappet 1 manufactured by such a method, the sliding end face of the ceramic body 4 is shown in FIG.
The crowning shape as shown in FIG. That is, the peripheral portion 4b of the sliding end face of the brazed ceramic body 40 is greatly affected by the thermal stress, and a crowning having a small radius of curvature (average value of the radius of curvature) is formed. The center portion 4d of the end surfaces is not joined, so that it is hardly affected by thermal stress, and a crowning having a large radius of curvature (average value of the radius of curvature) is formed.

[0034]

EXAMPLE The performance of the tappet (joint) 1 of the present invention was confirmed.
In order to do this, a prototype was manufactured under the following conditions. First, steel
As the material, alloy steel SNCM630 specified in JIS,
And SNCM439 by forging and mechanical grinding
In the shape shown in FIG. 2, t1 = 50 mm and d = φ18 mm
Tappet fitting 2 was produced. On the other hand, Si₃N₄Raw material 10
0 parts by weight, Al₂O₃-Y₂O₃Sintering aid 10
Parts by weight and 5 parts by weight of the molding binder.
And then debindered, then N ₂Gas atmosphere
Baking at 1700 ° C. for 2 hours.
Obtained. Polishing both sides of the fired body thus obtained
A backing plate 4 was prepared. In FIG. 2, D1 = φ30
mm, t2 = 1.5 mm (corresponding to the thickness of the ceramic plate)
It is. Then, the tappet fitting 2 and the ceramic plate 4
And brazing in a vacuum atmosphere
By joining, a tappet 1 having a shape shown in FIG. 2 is obtained.
Was. The tappet test items are steel, brazing material, brazing
The tapping temperature was changed and the two types of tappets I and I shown in Table 1 were changed.
I prepared.

[0035]

[Table 1]

The sliding end face of the tappet I produced by brazing under such conditions, ie, the ceramic plate 4
The crowning having a radius of curvature of about 5625 mm was formed almost uniformly on the sliding end face of No. 1, while the crowning having a radius of curvature of about 1607 mm was formed almost uniformly on the sliding end face of Tappet II.

Next, as shown in Table 2, tappets I and II having different average values of curvature radii R1, R2 and φD2 / φD1 were manufactured by the processing method shown in FIG. As shown in FIG. 2, φD2 / φD1 is an outer diameter φD2 of the central portion 4d and an outer diameter φD of the peripheral portion 4b.
It represents the ratio to 1. Tappet No. Nos. 1 to 8 are comparative examples in which the sliding end face 4a of the ceramic body 4 has a substantially uniform radius of curvature (referred to as R2 for convenience). Reference numerals 9 to 24 denote embodiments of the present invention, which have different radii of curvature at the peripheral portion (radius of curvature R1) and the central portion (radius of curvature R2), and have different φD2 / φD1 respectively. In addition, the curvature radii R1 and R2 of crowning were calculated by averaging the data of 5 points or more each with a shape measuring instrument or a three-dimensional measuring instrument.

Each of the tappets obtained in this way was
The motoring test was performed by assembling a 00 cc V-type 12-cylinder diesel engine. The operating conditions were implemented with the following settings to increase wear and impact force. The number of rotations of the cam is 2400 rpm (rated × 150%), the tappet clearance is 0 mm, and the durability time is 1000 hours. All of these conditions are severe, assuming a shock equivalent to traveling 1 million km on a real vehicle. Using an engine oil equivalent to traveling for 50,000 km, the engine temperature is relatively high and the engine temperature is relatively easy to rise. Is formed.

The evaluation of the ceramic state after the endurance was as follows.
Samples in which the bonding area ratio by ultrasonic flaw detection changed by 1% or more before and after endurance (corresponding to the occurrence of peeling) were regarded as NG, and those with less than that were judged as acceptable (OK). After the motoring test, for a ceramic body having no chipping, cracking, or the like, the abrasion test evaluated the abrasion generated on the cam and the tappet. The evaluation of abrasion was performed by measuring the cross-sectional shape with a surface roughness meter and taking the value of the most worn portion. Table 2 shows the results.

[0040]

[Table 2]

As is clear from the results, the relationship between R1 and R2 (R1 <R2, preferably 5 × R) regardless of the material of the metal body (steel) or the brazing material and the brazing conditions.
1 <R2) passed the motoring endurance test, and the sliding end face of the ceramic body after the endurance had no chipping or cracks. No significant wear had occurred. On the other hand, in the case of the comparative example, no matter what value the uniform radius of curvature was set, chipping or cracking occurred on the sliding end face of the ceramic body, or pitching wear occurred on the cam. In addition, about the tappet of an Example, for example, N
o. Comparing 9 to 12, the value of φD2 / φD1 is 75
Cam wear and tappet wear (wear of the sliding end face of the ceramic body) tend to increase as the value is smaller than 90%. From this, it can be seen that the boundary between the central portion and the peripheral portion having different radii of curvature is preferably set at a position where the value of φD2 / φD1 is 80 to 90%.

[Brief description of the drawings]

FIG. 1 is a front view of an overhead valve mechanism including a tappet of the present invention.

FIG. 2 is an enlarged view of the tappet of FIG.

FIG. 3 is an enlarged view showing a sliding end surface of the tappet of FIG. 1;

FIG. 4 is an explanatory view showing the concept of a brazing material layer.

FIG. 5 is a longitudinal sectional view showing some modified examples of the tappet.

FIG. 6 is a diagram illustrating a processing method for forming crowning on a tappet.

FIG. 7 is a diagram showing a modification of the tappet.

FIG. 8 is a diagram showing a different modification of the tappet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tappet (ceramic sliding part) 2 Tappet fitting (metal body) 3 Brazing material layer 4 Ceramic plate (ceramic body) 4a Sliding end surface 4b Peripheral part 4d Central part 50 Grinding stone 60 Buffer plate (buffer member)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // B23K 103: 18 B23K 103: 18 F term (reference) 3G016 AA04 BA18 BA19 BB06 BB08 BB09 BB21 CA06 CA09 CA14 CA19 CA34 EA01 EA02 EA14 FA30 FA33 FA34 GA02 4G026 BA17 BB26 BF16 BF17 BG02 BG23 BH03

Claims (9)

[Claims] 1. A ceramic sliding component having a sliding end face made of ceramic, wherein the sliding end face has a curved surface shape whose central side protrudes from the end face reference plane with a plane including an outer edge thereof as an end face reference plane. Is formed, a boundary point is defined at an arbitrary point away from the center point on the sliding end face, and a portion of the sliding end face from the boundary point toward the outer edge is defined as a peripheral portion, and from the boundary point When the portion toward the central point is the center, the average value R1 of the radius of curvature of the crowning corresponding to the peripheral portion is R1 <R with respect to the average value R2 of the radius of curvature of the crowning corresponding to the center.
2. A ceramic sliding part which satisfies the relationship of 2. 2. A distance between the center point and an outer edge of the sliding end face in a direction parallel to the end face reference plane is D, and a position corresponding to 0.8D from the center point is the boundary point. The described ceramic sliding parts. 3. The ceramic sliding component according to claim 1, wherein R1 and R2 satisfy a relationship of 5 × R1 <R2. 4. The ceramic sliding part according to claim 1, wherein a surface roughness of the sliding end face is rougher in the peripheral part than in the central part. 5. An end face opposite to a sliding end face of the ceramic body is a joining surface, and the joining surface is brazed to a joining surface of the metal body via a brazing material layer.
A ceramic sliding part according to any one of the above. 6. The ceramic sliding component according to claim 1, wherein the thickness of the ceramic body is increased on the side of the central portion and reduced on the side of the peripheral portion. 7. In the ceramic body, a portion facing the peripheral portion in the joining surface is joined to the metal body by brazing, while facing the central portion in the joining surface. The ceramic sliding component according to claim 5, wherein the portion is not joined. 8. The method according to claim 8, wherein the metal body and the ceramic body are
A cushioning member having an area smaller than that of the joining surfaces is disposed at a position facing the central portion, and the metal body and the ceramic body are brazed at the remaining portion of the joining surface where the cushioning member does not exist. The ceramic sliding component according to any one of claims 5 to 7, wherein, while being joined, the joining surfaces facing the center portion are joined by brazing via a buffer member. 9. The ceramic sliding component according to claim 1, wherein said sliding end surface is configured as a tappet having a cam sliding surface.