JP2001152814A - Tappet and attaching structure for tappet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an attaching structure for a tappet for sharply improving the durable service life of a tappet and for preventing excess damages to a sliding counterpart parts. SOLUTION: In this tappet 1, a stem shaped tappet stem part 1a positioned on a side opposite to a sliding surface 4a is penetrated and held on a cylindrical body hole 106. In the case where the tappet 1 is attached to the cylinder body hole 106, the relation 0.0022<=(ϕD-ϕd)/L<=0.004 is satisfied, when the hole diameter of the cylinder body hole 106 is defined as ϕD, an outer diameter of the tappet stem part 1a is defined as ϕd, and the length of the tappet stem part penetrated on the cylinder body hole 106 is defined as L.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tappet mainly used for an internal combustion engine of an automobile and a mounting structure for the tappet.

[0002]

2. Description of the Related Art A tappet used in an internal combustion engine of an automobile is a sliding component for transmitting a displacement amount due to rotation of a cam to a valve via a push rod. As a specific configuration, a shaft-like hole (hereinafter, referred to as
Abrasion-resistant materials such as cemented carbide, ceramics and cermets are attached to a metal body having a stem that moves up and down in the cylinder body by brazing, press fitting, etc. to form a sliding surface with the cam. Is widely known.

[0003] In such a tappet, the roundness and coaxiality of a stem portion inserted into the cylinder body hole correspond to the cylinder body hole due to the function of moving up and down along the cylinder body hole with the rotation of the cam. It is finished with high accuracy. In addition, in order to maintain the above-described function well, the sliding surface is configured to have a positional relationship perpendicular to the stem portion, thereby suppressing end surface run-out of the sliding surface. Note that the relationship between the squareness of the sliding surface and the stem here is as follows:
It is assumed that it is considered based on the positional relationship between the plane including the outer edge of the sliding surface and the central axis of the stem shaft. For example, in the case where the sliding surface is provided with a curved crowning (small curvature protruding at the center portion) in order to cause the tappet to rotate for the purpose of preventing uneven wear of the sliding surface, etc., FIG. As shown, the perpendicularity is considered based on the relationship between the plane f ′ including the outer edge 103b of the sliding surface 103a and the central axis O of the stem portion 102a.

[0004]

Incidentally, the perpendicularity between the sliding surface and the stem portion is, for example, a factor in manufacturing when the wear-resistant member constituting the sliding surface is mounted on the metal body, or the mounting of both. Due to the surface roughness and inclination of the surface, there may be some variation even in the same product lot. If there is a variation in the perpendicularity, as shown conceptually in FIG.
02a of the sliding surface 103a with respect to the direction of the central axis O of the sliding surface 02a. The runout θ1 is referred to as a relative contact angle (θ1 + θ2) when summed up with a cam taper angle θ2 provided on the cam side contact surface 201 with the tappet to promote rotation of the tappet. That is, the end face deflection θ1
Occurs, the pre-adjusted relative hitting angle increases. Furthermore, the variation of the relative hit angle is
Not only the influence on the tappet side, but also due to a cam or tappet engine mounting error.

[0005] When the relative contact angle varies, the contact of the cam with the sliding surface is likely to be localized. In particular, the contact point between the cam edge and the sliding surface from the sliding track of the cam becomes near the outermost peripheral portion. Cheap. For this reason, the cam contact area on the sliding surface is reduced, the surface pressure applied to the sliding surface from the cam is increased, and the stem is eccentric in the cylinder body hole. It is locally pressed against the cylinder body hole and is subjected to vertical movement. As a result, not only is it difficult to move the tappet in the axial direction, but also there is a risk that seizure or the like may occur between the tappet and the cylinder body hole, thereby reducing the durability life of the tappet.

[0006] It is an object of the present invention to provide a tappet and a tappet mounting structure capable of improving the durability life of the tappet even when the relative contact angle varies as described above.

[0007]

The tappet mounting structure of the present invention for solving the above-mentioned problems has a sliding surface with a cam and a shaft-like structure located on the opposite side to the sliding surface. A tappet having a stem portion, and a shaft-shaped cylinder body hole through which the stem portion is inserted, wherein the outer diameter of the stem portion is φd, the hole diameter of the cylinder body is φD, and the tappet is inserted into the cylinder body hole. When the length in the axial direction of the stem portion is L, the relationship of 0.0022 ≦ (φD−φd) /L≦0.004 is satisfied.

Further, the tappet of the present invention has a sliding surface with the cam and an axial stem portion located on the opposite side to the sliding surface, and the stem portion is provided in the axial cylinder body hole. The diameter of the cylinder body hole should be φD
When the outer diameter of the stem is φd and the axial length of the stem inserted into the cylinder body hole is L, the relationship of 0.0022 ≦ (φD−φd) /L≦0.004 is satisfied. It is characterized by doing.

When the tappet is mounted in the cylinder body hole, a value obtained by standardizing the clearance amount (φD−φd) between the stem portion and the cylinder body hole by the axial length L of the stem portion falls within the above range. When set, the lifespan of the tappet is greatly improved. When the clearance in the above range is formed, it is possible to provide the tappet with a degree of freedom in sliding, particularly in a direction along the sliding surface. As a result, even when the relative contact angle varies and the surface pressure applied to the sliding surface from the cam increases, the tappet can easily escape in a direction in which the pressure is reduced, and the tappet (stem) is inserted into the cylinder body hole. Will be subjected to vertical movement. Therefore, even if the relative contact angle varies,
An increase in surface pressure applied to the sliding surface from the cam is reduced, and the stem is prevented from moving up and down while being pressed locally against the cylinder body hole. And local abrasion can be suppressed, and the durable life of the tappet can be greatly improved. Further, since the above-mentioned range specification is obtained by standardizing the clearance amount (φD−φd) by the stem length L, a high durability can be obtained for any tappet having a mounting structure that satisfies the clearance amount. It can have a long life.

The degree of freedom of the tappet depends strictly on the axial length (hereinafter, also referred to as the effective length L2) of the stem held (inserted) in the cylinder body hole.
It is preferable to standardize the clearance amount (φD−φd) by the axial length of the stem portion actually held (inserted), but generally, about 90 to 1 of the axial length L of the stem portion.
Since the effective length L2 is 00%, for the sake of convenience, there is almost no substantial problem even if the standardization is performed using the axial length L of the stem portion (of course, the clearance amount standardized by the effective length L2). Preferably fall within the above numerical range).

A standardized clearance amount (φD−φ
d) If / L is less than 0.0022, it becomes difficult for the tappet (stem) to move up and down in the cylinder body hole due to rotation of the cam, and seizure or the like occurs between the tappet and the cylinder body hole. In some cases, the effect of suppressing wear of the stem portion may not be sufficiently obtained. On the other hand, (φD
If -φd) / L exceeds 0.004, the degree of eccentricity of the stem portion in the cylinder body hole becomes large, and the tappet becomes large and easily rattles. Further, the sliding surface with the cam is displaced, so that the outer edge of the sliding surface comes into contact with the cam, that is, so-called outside contact is likely to occur, which may cause a problem in the durability life of the tappet. The above range is desirably 0.0
It is preferable that 025 ≦ φD−φd / L ≦ 0.0035.

[0012] The tappet has a structure in which the center axis of the metal member and the wear-resistant member are joined so that the central axes thereof are substantially coincident with each other. In the case of a tappet whose end surface is a sliding surface, a problem such as peeling or the like has conventionally been liable to occur at the joint. In particular, the wear-resistant member that forms the sliding surface is
In the case of a tappet brazed to a metal body on the side opposite to the sliding surface, the brazed interface is the weakest in terms of strength. The wearable member may peel off. Such peeling is likely to occur when a force in the shear direction is continuously applied to the brazed interface. In particular, if the relative contact angle varies, the contact of the cam with the sliding surface of the wear-resistant member may concentrate near the outermost peripheral portion of the sliding surface, and the interface joined by brazing may generate a large force in the shear direction. It may be received continuously. However, according to the present invention, the clearance in the above range is formed between the tappet and the cylinder body hole, so that the tappet has a degree of freedom in sliding, particularly in a direction along the sliding surface. Therefore, the stress in the shearing direction on the sliding surface is reduced, the peeling of the wear-resistant member can be effectively suppressed, and the durability life of the tappet can be significantly improved. In addition, as a wear-resistant member, a cemented carbide or a cermet may be mentioned, but it is preferable to use a ceramic having excellent mechanical strength and wear resistance.

[0013]

Embodiments of the present invention will be described below with reference to the embodiments shown in 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. The tappet 1 has a hole 106 in the cylinder body 105.
(Hereinafter also referred to as a cylinder body hole 106) to prevent, for example, lateral movement.

FIG. 2 is an enlarged view of the tappet 1. In the tappet 1, a metal body (hereinafter, also referred to as tappet fitting) 2 and a ceramic body (hereinafter, also referred to as ceramic plate) 4 are joined via a brazing material layer 3 in such a manner that their central axes are substantially coincident. It has a structure. 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 a body part (tappet stem portion (stem portion)) 1a having a circular cross section, and the other end. A sliding base 1b having a larger diameter than the tappet stem 1a is integrally formed on the end side. On the other hand, the ceramic plate 4 is formed in a disk shape as a sintered body of silicon nitride,
b is overlapped and joined to the flat tip surface. The brazing material forming the brazing material layer 3 is a Cu-based or Ag-based brazing material. And the brazing material layer 3 of the ceramic plate 4
The end surface opposite to the end in contact with the cam 100 is a sliding end surface (sliding surface) 4a with the cam 100. The sliding end face 4a of the ceramic plate 4 is provided with a curved crowning (a small curvature with a central portion projecting) whose center side projects from the end face reference plane f, with the plane f including the outer edge thereof as an end face reference plane. (The drawing is slightly exaggerated).

The tappet 1 having such a shape is inserted and held in the cylinder body hole 106 as shown in FIG. 1, and the mode thereof will be described with reference to FIG. The shaft-shaped tappet stem 1a located on the opposite side of the sliding surface 4a of the tappet 1 is inserted with a predetermined clearance into the cylinder body hole 106, and can be moved up and down in the axial direction by the clearance. ing. That is, when the cam 100 (FIG. 1) moves up and down by its own displacement, the valve 10
1 (FIG. 1).

By the way, as shown in FIG.
Is the center axis O of the tappet 1 (FIG. 3B).
1 (a), the tappet 1 is rotatable around the axis O1 with the rotation of the cam 100, thereby preventing uneven wear of the sliding surface 4a.
In this case, the sliding trajectory of the cam 100 with respect to the sliding surface 4a has a shape that sweeps a circular area (hereinafter, referred to as a sliding area) as shown by a broken line in FIG. In a general tappet, if the outer diameter of the sliding surface 4a is γ and the outer diameter of the sliding area is δ, δ / γ is set to about 0.8 to 1.2. The sliding area overlaps the area outside of 80% of the moving surface outer diameter (that is, the projected cross-sectional outer diameter) γ. When δ / D is larger than 1.0, it means that the entire end face of the ceramic plate 4 is used as a sliding surface.

Here, when the rotation of the cam 100 is low, such as during idling, as shown by a broken line in FIG.
The impact force applied to the tappet 1 from the cam 100 becomes maximum near the center of the sliding end face 4a, which is the peak of crowning. However, in the high-speed rotation state, an extremely large impact force is applied near the outer peripheral edge of the sliding end face 4a due to the inertial force of the valve train as shown by the solid line in the drawing. The perpendicularity between the sliding end face 4a and the tappet stem 1a or the tappet 1
When the relative contact angle, which is adjusted in advance due to the engine mounting error, varies, the contact of the cam 100 with the sliding end face 4a is likely to occur, and the contact of the cam 100 is caused near the outer peripheral edge of the sliding end face 4a. It is easy to be. At this time, the stem portion 1a and the cylinder body hole 106
Is small, the degree of freedom of the tappet 1 to move up and down is small, and the stem portion 1a tends to eccentrically move in the cylinder body hole 106, so that the tappet 1 moves in the axial direction. It will be difficult. In this case, seizure or the like may occur between the stem portion 1a and the cylinder body hole 106. In addition, impact stress (stress in the shearing direction) is concentrated on the brazing material layer 3, which may cause the brazing material to be peeled and the ceramic plate 4 to be peeled off.

On the other hand, as shown in FIG. 5A, when the center axis O1 of the tappet 1 is slightly displaced and the tappet is given a swing width, the impact force applied to the tappet 1 is dispersed and the stress concentration is increased. Less. When the clearance between the tappet stem portion 1a and the cylinder body hole 106 is increased, the relative contact angle tends to increase greatly, and the cam 100 protrudes from the sliding surface 4a as shown in FIG. An external hit occurs at the outer edge of the sliding surface 4a. The outer contact may cause chipping or chipping on the sliding surface, which may cause a serious problem in the durability of the tappet 1. Further, if the clearance amount is large, the tappet stem portion 1a may rattle, and the wear amount of the tappet stem portion 1a may be increased.

Therefore, in the present embodiment, as shown in FIG. 3, when the diameter of the cylinder body hole 106 is φD, the outer diameter of the tappet stem 1a is φd, and the length is L, The clearance between 1a and the cylinder body hole 106 is defined in the range of 0.0022 ≦ (φD−φd) /L≦0.004. The cylinder body hole diameter φD has various sizes depending on the engine design, and the outer diameter φd of the tappet stem portion 1a is preferably determined so as to satisfy the above range for any cylinder body hole. In this embodiment, for example, φD = 18.00 mm, φd
= 17.830 mm, L = 60.0 mm, and (φ
D−φd) /L≒0.0028. The effective length L2 of the tappet stem portion 1a actually inserted into the cylinder body hole 106 is 90% of the length L of the stem portion.
It is about 100% (for example, 92%).

By setting the amount of clearance (φD−φd) / L, which is standardized by the axial length L of the stem portion, in the above range, the tappet 1 can have a degree of freedom in sliding. When the tappet 1 receives a force from the cam 100, the tappet 1 can easily escape in a direction in which the pressure is reduced. Accordingly, an increase in surface pressure applied to the sliding surface 4a from the cam 100,
The shear stress or the like on the sliding surface 4a is reduced, and as a result,
Early wear and uneven wear of the tappet stem 1a can be suppressed,
Further, the joining life between the ceramic body 4 and the tappet fitting 2 can be improved, and the durability life of the tappet 1 can be greatly improved.

As the Fe-based material constituting the tappet fitting 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, such as tappets.
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, when 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 generally 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. 6, in the joining direction of the metal body and the ceramic body, the cation component having the highest content among 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. 7A, the push rod insertion hole may be extended to a position into the sliding base 2b, or as shown in FIG. The base 2b may have substantially the same diameter, and the whole may be configured in a cup shape.

[0029]

EXAMPLES In order to confirm the performance of the tappet 1 of the present invention, a prototype was manufactured under the following conditions. First, as a steel material, forged alloy steel SNCM630 specified in JIS,
A tappet fitting (metal body) 2 having the shape shown in FIG. 2 was produced by mechanical grinding. On the other hand, Si ₃ N ₄ raw material 10
Al ₂ O ₃ —Y ₂ O ₃ based sintering aid is added to 1 part by weight
0 parts by weight and a forming binder were blended and formed into a plate shape by a mold press. And that after the molded body was de binder, after normal pressure presintered at 1700 ° C. in N ₂ gas atmosphere, forms a gas pressure at 1700 ° C. · 100 atm with N ₂ gas atmosphere, firing the disc-shaped I got a body. Both surfaces of the fired body thus obtained were ground to form a ceramic plate 4 (thickness: 1.5 mm, outer diameter: 30 mm). Then, a brazing material foil is interposed between the tappet fitting 2 and the ceramic plate 4 and brazed in a vacuum atmosphere to form a tappet (A type) having the shape shown in FIG. 2 and FIG. 7B. Tappets (B type) having the shapes shown were produced. The brazing material foil used was an Ag-Cu-In-Ti-based brazing material (Ag: 60w).
t%, In: 12 wt%, Ti: 1 wt%, balance Cu,
The thickness is 0.040 mm), the brazing condition is 800 ° C. × 2 hr in a vacuum atmosphere, and the cooling rate after brazing is 10
° C / min.

Note that the stem length L is 60 mm for the A-type tappet, and 90 mm for the B-type tappet, and the clearance (φD−φd) between the tappet stem portions 1 a and 2 a and the cylinder body hole 106 is the A-type tappet. And B types, respectively, were prepared in the range of 15 to 450 μm shown in Table 1.

Next, these tappets were mounted on a cam motoring tester, and a durability test was performed under the following conditions.
Each of the A-type and B-type tappets was attached to a 12000 cc in-line 6-cylinder diesel engine, and a tappet stem 1
In order to increase the abrasion of the a and the impact force on the sliding surface 4a, the oil temperature is 100 ° C. (deteriorated oil equivalent to traveling 50,000 km in the market) and the cam rotation speed is 2,000 rpm (rated × 150
%), A tappet clearance of 1 mm (standard value × 3), and a set load at the nose top position were set to twice the standard specifications, and the test was performed for up to 1000 hours. Ultrasonic flaw detection is performed every predetermined time on the way. If the bonding area ratio changes by 1% or more (corresponding to the occurrence of peeling), it is determined that the durability limit has been reached, and the test time at that time is determined as the durability time. Was. Table 1 shows the above results. The number of measurements is n = 2 under each condition (data is individually displayed as A type 1, A type 2, B type 1, B type 2).

[0032]

[Table 1]

From these results, in the case of type A, when the clearance amount is 120 μm or more, good durability of about 400 hours or more is exhibited, and when the clearance amount is 180 μm or more,
High durability of 1000 hours or more was shown. On the other hand, in the case of type B, when the clearance amount is 180 μm or more, about 4
In the case of 50 hours or more and 240 μm or more, high durability of 1000 hours or more was exhibited. In this result, type A and B
Table 2 shows data in the case where the amount of clearance is normalized by dividing the amount of clearance by the stem length L in consideration of the difference in the durability of the mold due to the stem length L of the tappet.

[0034]

[Table 2]

As described above, the clearance amount is set to the stem length L.
In the case of dividing by A, both A type and B type are (φD−φd) / L
= 0.002 or more indicates good durability.
FIG. 8 is a graph in which the value of (φD−φd) / L is plotted on the X axis and the durability time is plotted on the Y axis. From this graph, for any of the samples, (φD−φd) / L = 0.
It turns out that it has high durability at 0022 or more.

[0036]

Example 2 The same samples as in Example 1 were evaluated for the amount of wear at the stem. In the evaluation of abrasion, the degree of abrasion at the time when the sample became NG within 1000 hours in Example 1 was evaluated. The degree of wear was measured. In addition, the measurement of the abrasion degree was performed by measuring the outer diameter of the stem portion using a micrometer and using a non-contact laser shape measuring instrument. Table 3 shows the results.

[0037]

[Table 3]

From these results, it can be seen that in the case of type A, when the clearance amount is 300 μm or more, the stem portion is greatly worn, while in the case of type B, the clearance amount is 3 μm.
It can be seen that when the thickness is 90 μm or more, the wear is large. Table 4 shows data obtained by normalizing the result by dividing the clearance amount by the stem length L, similarly to the first embodiment.

[0039]

[Table 4]

As described above, the clearance amount is set to the stem length L.
When (φD−φd) /L=0.004 or less, it can be seen that neither A-type nor B-type is significantly worn. Taking the value of (φD−φd) / L on the X axis,
FIG. 9 shows a graph in which the amount of wear is plotted on the Y axis. From this graph, (φD−φd) /
It can be seen that by setting L = 0.004 or less, it is possible to suppress wear of the stem. Note that (φD−φ
d) If the value of / L is too small (for example, less than 0.0022), the tappet stem 1
a becomes difficult to move up and down in the cylinder body hole 106, seizure may occur between the tappet 1 and the cylinder body hole 106, and the effect of suppressing the wear of the tappet stem 1a is sufficiently obtained. Not always.

[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 details of a tappet mounting structure of the present invention.

FIG. 4 is an explanatory diagram showing an arrangement relationship between a cam and a tappet together with a cam sliding range and an impact force distribution.

FIG. 5 is an explanatory diagram showing an outside contact of a cam to a tappet sliding surface.

FIG. 6 is an explanatory view showing the concept of a brazing material layer.

FIG. 7 is a longitudinal sectional view showing some modified examples of the tappet.

FIG. 8 is a graph showing a relationship between a durability time and a value obtained by standardizing a clearance amount by a stem length.

FIG. 9 is a graph showing a relationship between a wear amount of a stem portion and a value obtained by standardizing a clearance amount by a stem length.

FIG. 10 is a diagram for explaining a positional relationship between a crowned tappet and a cam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tappet 1a Tappet stem part (stem part) 2 Tappet fitting (metal body) 4 Ceramic plate (ceramic body) 4a Sliding end surface (sliding surface) 100 Cam 106 Cylinder body hole

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G016 AA05 AA19 BB02 BB06 BB08 BB19 CA08 CA11 CA41 CA56 EA01 EA07 EA14 EA24 FA33 GA02

Claims (5)

[Claims] 1. A tappet having a sliding surface with a cam, a shaft-shaped stem portion located on the opposite side to the sliding surface, and a shaft-shaped cylinder body hole through which the stem portion is inserted. In the structure, when the outer diameter of the stem portion is φd, the hole diameter of the cylinder body is φD, and the axial length of the stem portion inserted into the cylinder body hole is L, 0.0022 ≦ (φD -Φd) /L≦0.004. A tappet mounting structure characterized by satisfying the relationship: 2. The tappet has a structure in which central axes of a metal body and a wear-resistant member are substantially coincident with each other, and the tappet is bonded to the metal body of the wear-resistant member. The tappet mounting structure according to claim 1, wherein an end surface opposite to the end is the sliding surface. 3. The wear-resistant member forming the sliding surface,
The tappet mounting structure according to claim 2, wherein a surface opposite to the sliding surface is brazed to the metal body. 4. The tappet mounting structure according to claim 2, wherein the wear-resistant member is made of a ceramic body. 5. A tappet having a sliding surface with a cam and an axial stem portion located on the opposite side to the sliding surface, wherein the stem portion is inserted into an axial cylinder body hole. When the hole diameter of the cylinder body hole is φD, the outer diameter of the stem portion is φd, and the axial length of the stem portion inserted into the cylinder body hole is L, 0.0022 ≦ (φD−φd A tappet characterized by satisfying the following relationship: /L≦0.004.