JPH1149579A - Joined body by brazing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joined body which is provided with a brazing filler metal layer having uniform thickness and in which any local stress is prevented from being caused in a ceramic member even at the time of using the body as a tappet. SOLUTION: The production of this joined body comprises: placing a projecting part 5 having a specified height on a surface 2a to be joined by brazing of a metallic member 2 along the periphery of the surface 2a; interposing a brazing filler metal between the surface 2a to be joined of the metallic member 2 and the surface 3a to be joined of a ceramic member 3; placing a weight on the ceramic member 3; and melting the brazing filler metal. At this time, the molten brazing filler metal is compressed with the ceramic member 3 that is floated on the molten brazing filler metal, by the action of the weight, so that both the members 2 and 3 are substantially abutted on each other at the front end surface of the projecting part 5. Accordingly, the resulting brazing filler metal layer 4 between the surfaces 2a and 3a to be joined has almost the same constant thickness as the height of the projecting part 5, in the inner region surrounded by the projecting part 5. Since no projecting part exists in this inner region, any local large stress is not caused in the inner region of the surface 3a to be joined of the ceramic member 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazed joint formed by joining a metal member and a ceramic member by brazing, and more particularly, to an engine component such as an engine tappet, a valve lifter or a rocker arm. The present invention relates to a brazed joint (hereinafter, also simply referred to as a joined body) between a metal member and a ceramic member used for the like.

[0002]

2. Description of the Related Art Ceramics have been used in various fields because of their excellent properties such as heat resistance, thermal shock strength, mechanical strength at high temperatures, and abrasion resistance. However, it is rarely used alone, and is usually used as a joined body formed by brazing with a metal member. As a basic structure, for example, there is a cylindrical shape formed by joining a disk-shaped (circular thin plate) ceramic member and a cylindrical metal member. Based on this structure, various types of tappets such as engine tappets are used. Has been applied to parts.

However, in such a joined body, it is difficult to maintain the thickness of the brazing material layer uniformly with high precision. The reason is as follows. Conventionally, the thickness of the brazing material layer is controlled by controlling the amount of the brazing material to be used, that is, the thickness and the number of the brazing material foils, or the so-called brazing conditions such as the brazing temperature (time). It has been performed by adjusting to an appropriate material according to the brazing material to be used.
However, when the brazing material is melted, the ceramic member or the metal member becomes unstable because the ceramic member or the metal member floats on the molten solder on one flat brazing joint surface (hereinafter, also simply referred to as a joining surface). . Therefore, it is basically easy to cause unevenness in the thickness of the molten row before it is cooled and joined.
This tendency becomes more remarkable as the thickness of the brazing material layer increases.

[0004] In this brazing, in order to obtain a highly reliable joint by extruding voids and impurities in the brazing material, a weight is placed on an upper member of the joined body, and the joining surfaces are mutually connected. In general, excessive brazing material is positively protruded outside from the peripheral edge of the joint surface during pressurization and heating brazing. Therefore, in order to prevent the thickness from becoming uneven, it is conceivable to increase the weight (weight) to crush the molten solder.
It is not easy to crush this sufficiently to obtain a uniform thickness.

[0005] Further, in a joined body in which the members having a remarkable difference in thermal expansion coefficient, such as a metal and a ceramic, are brazed to each other, the stress generated in both members due to the difference is an intermediate coefficient of thermal expansion. In order to be absorbed (buffered) by the brazing material layer having an appropriate value, the brazing material layer may be made thicker over the entire joint surface. In response to such a demand, if the weight is increased, the brazing material layer becomes thinner as a whole, and a desired thickness cannot be secured, and the function as a buffer layer for absorbing the stress cannot be achieved.

[0006] As described above, it is difficult to control the thickness of the brazing material layer to a uniform thickness, particularly to a set value, and thus it is generally difficult to control the thickness of the brazing material layer. For tappets
0-80 μm). However, such non-uniformity of the thickness causes an inclination between the joining surface and the opposite surface (surface) of the ceramic member (plate).
Such a slope is a ceramic member that forms a cam sliding surface in the rotation when the joined body rotates itself around an axis by sliding with a cam like a tappet or a valve lifter. As a result, the rotation of the ceramic member becomes abnormal, resulting in uneven wear or breakage of the ceramic member.

Under these circumstances, as shown in Japanese Patent Application Laid-Open No. 6-297139, a portion of the brazing material layer between the joining surfaces is
There is a technique in which a brazing material layer thickness holding means for maintaining the thickness of the brazing material layer is provided. For example, a protrusion having a height corresponding to the thickness of the brazing material layer set on the joining surface is formed, and the thickness of the brazing material layer is maintained at the height of the protruding portion. With this technique, by adjusting the height of the projections to the thickness of the brazing material layer, it is possible to obtain a joined body having a brazing material layer having a uniform thickness substantially as set.

[0008]

However, in an engine tappet or the like, the actual sliding surface (cam contact surface) of the cam contact surface formed by the ceramic member is a portion that is closer to the center than the peripheral edge. When the elastic modulus of the metal member (SNCM, SUS304, etc.) forming the joined body is compared with the elastic modulus of the brazing material, the former is much larger. Because of this, the protrusion is the same as the metal member (integral)
In the one provided on the part inward from the periphery of the joint surface, when used as a tappet, sliding with the cam,
Among the joining surfaces of the ceramic members, a large stress is locally generated at a portion corresponding to the convex portion of the metal member, and there is a risk that the life of the ceramic member may be shortened due to damage to the ceramic member.

The present invention has been made in view of such a problem, and an object thereof is to secure a uniform thickness of a brazing material layer in a brazed joint of a metal member and a ceramic member. In addition, even if the ceramic member is used as a tappet or the like, a local stress is not generated in the ceramic member so that the life of the ceramic member is extended.

[0010]

In order to achieve the above object, the present invention is directed to a brazed joint formed by joining a metal member and a ceramic member by brazing. And a protrusion (projection) having a constant height is provided along a peripheral edge of at least one of the brazing surfaces. Here, the convex portion is preferably located at a portion near the periphery including the periphery. Further, the convex portion is for preventing the thickness of the brazing material layer from becoming uneven, and its height is adjusted so that the thickness of the brazing material layer at an inward portion surrounded by the protruding portion is substantially constant. The thickness may be set to be substantially the same as or smaller than the thickness of the brazing material layer.

In such a joined body, a brazing material is interposed between the joining surfaces of the two members, and a weight is placed on one of the upper members so that the brazing material is compressed. It is brazed by heating and melting the brazing material. In the joining process, when the brazing material is reflowed, one of the members floating in the molten row compresses the molten brazing material layer by the weight. Then, the brazing material layer between the joining surfaces of the two members has an extremely small thickness at the distal end surface of the projection, and the two members are substantially in contact with each other at the distal end surface. That is,
Since the molten row is extremely thin at the convex portion, one member existing on the molten row is stabilized without being unstably floated. In addition, since the projection is provided along the periphery, there is no wobble. Therefore, the thickness of the brazing material layer between the joining surfaces is thinner at the tip end surface of the convex portion, but relatively thick at an inward portion surrounded by the convex portion, and is approximately the same as the height of the convex portion and has a uniform thickness. And one member is brazed without inclination.

According to a second aspect of the present invention, in a brazed joint formed by joining a metal member and a ceramic member by brazing, the metal member has a fixed height along a peripheral edge of a brazed joint surface of the metal member. It is characterized in that a projection is provided. In this case, since the ceramic member can be a flat plate (thin plate) having both main surfaces parallel to each other, the member does not have a complicated shape.

[0013] In any of the above means, the projection may be formed continuously along the periphery of the brazing joint surface, or may be formed along the periphery of the brazing joint surface. It may be formed discontinuously. In particular, if formed discontinuously, it is effective to extrude voids and impurities in the brazing material together with the excess molten solder from between the convex portions.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a joined body according to the present invention will be described in detail with reference to FIGS. However, the joined body 1 in this example is an engine tappet, and a ceramic member (circular thin plate) 3 serving as a cam contact surface is formed on a metal material 2 having a cup shape (bottomed cylindrical shape) forming a tappet body. 4 to be brazed. The metal member 2 is JIS SNCM630
The end face forming the joint surface 2a has a center line average roughness Ra: 0.3 μm and is flatly turned. However, the protrusion (projection) 5 has a constant width (3 in this example) so as to form a ring along the periphery of the joint surface 2a.
mm) W, constant height H, so as to protrude in a rectangular cross section. The height H of the projection 5 from the joining surface 2a is set to 50 μm in this example, and the height H is substantially the same as the set thickness of the brazing material layer 4 at the inward portion of the joining surface 2a surrounded by the projection 5. It is said.

On the other hand, the ceramic member 3 is a circular thin plate (diameter 31 mm, thickness 2 mm) made of a sintered body of silicon nitride (90 wt% Si 3 N 4, the rest sintering aid). The main surfaces (joining surfaces) 3a and 3b are ground and finished to a center line average roughness Ra: 0.8 μm.

Thus, the joined body 1 of this embodiment is manufactured (joined) as follows. First, the joining surface 2a of the metal member 2
And a predetermined foil-like brazing material is concentrically placed on the joint surface 2a. However, the brazing material in this example has a diameter of 3
0-mm, 0.05-mm thick, In-Ti-
Cu-Ag system (In; 15.0%, Ti; 1.0%, C
u; 23%, Ag; 60%). The ceramic member 3 is positioned concentrically on the joining surface 2a of the metal member 2 with the brazing material sandwiched therebetween, and a weight (not shown) having a predetermined weight (for example, 150 g) is placed thereon. Then, an appropriate pressure is applied to the joint surfaces 2a and 3a.

Under these conditions, a vacuum is applied at 780 ° C. for 30 minutes.
Hold for 2 minutes and cool with N2 gas replacement. When the brazing material is melted in the heating process, the ceramic member 3 is floated on the melting row.
a and 3a are crushed between each other, and excess brazing material flows out beyond the front end surface (upper surface) of the convex portion 5 on the peripheral edge of the joining surface 2a. On the other hand, the ceramic member 3
The portion near the peripheral edge of “a” substantially comes into contact with the protrusion 5 on the joint surface 2 a of the metal member 2, and the thickness of the brazing material on the protrusion 5 is minimized. The figures are exaggerated for explanation. In this case, since the molten solder is not crushed any more, the thickness of the brazing material layer 4 at the inner portion surrounded by the convex portion 5 at that time is substantially equal to the height H of the convex portion 5. Will be retained. Therefore, by cooling under this,
The brazed joint 1 forms a brazing material layer 4 having a desired uniform thickness at an inward portion surrounded by the convex portion 5.

As will be understood from the above, according to the joined body 1 of the present invention, the thickness of the brazing material layer 4 does not substantially become smaller than the height H of the projection 5. Therefore, the weight of the weight can be set relatively large. Incidentally, the product of the above embodiment was cut at one center perpendicular to the center of the joining surface 3a of the ceramic member 3, and the thickness of the brazing material layer 4 at a portion surrounded by the convex portion was measured by a metallographic microscope. The difference in thickness was within 10 μm, and in the case where a metal member and a ceramic member having a flat joining surface were brazed under the same conditions, the peripheral edge of the joining surface (one diameter direction) was 80 μm.

Since the thickness of the brazing material layer 4 can be made substantially uniform, the inclination of the main surface (cam contact surface) 3b on the side opposite to the joining surface 3a of the ceramic member 3 can be made substantially nil. . Therefore, the normal rotation of the tappet is not impaired, and uneven wear due to cam half-contact is prevented. In addition, since the thickness of the brazing material layer 4 is maintained substantially uniformly at the height H of the convex portion 5, the height H of the protruding portion 5 is formed at a predetermined height, so that the brazing material layer 4 is formed. By itself, it can also serve to buffer the stress caused by the difference between the coefficients of thermal expansion of the two members 2 and 3.

Further, since the convex portion 5 is provided along the periphery of the joining surfaces 2a and 3a, the brazing material layer 4 has no convex portion 5 at the inner portion surrounded by the convex portion.
Is a uniform thickness. Therefore, even if the cam slides on the first main surface 3b of the ceramic member 3, a large stress is not locally generated at the inward portion of the joining surface 3a of the ceramic member 3, so that the ceramic member 3 is damaged. Hard to invite. Note that the thickness of the brazing material layer 4 at the inward portion surrounded by the protrusions 5 is substantially the same as or slightly greater than the height H of the protrusions 5. Therefore, the height H of the convex portion 5 may be set to be extremely smaller than the thickness of the brazing material layer 4 to be set.

In the above embodiment, the case where the convex portion 5 is formed on the joint surface 2a of the metal member 2 has been described. However, the convex portion 5 is formed on the joint surface 3a of the ceramic member 3 without being provided on the metal member 2. May be. Further, as shown in FIG. 3, the protrusions 5 and 15 may be formed along the periphery of the joint surfaces 2a and 3a of the metal member 2 and the ceramic member 3. When the projections 5 and 15 are provided on both the members 2 and 3 as described above, the brazing material layer 4 at the inward portion surrounded by the projections.
Is equal to or greater than the sum of the heights of the projections 5 and 15 of the two members 2 and 3, so that when securing the predetermined thickness of the brazing material layer,
One convex portion can be lowered.

In the above description, the cross-sectional shape of the convex portion 5 is square (rectangular), but the convex portion in the present invention is not limited to this. In addition, as shown in FIG.
It is preferable from the standpoint of strength that the inner wall surface 5a is tapered or the corner formed by the wall surface and the joining surface 2a is arc-shaped.

In the case where the joined body according to the present invention is subjected to a large stress at a portion inward of the periphery of the ceramic member as in the case where the joined body according to the present invention is used as an engine tappet, the ceramic member corresponding to the portion is subjected to the stress. In order to generate stress on average, it is preferable that the width W of the convex portion be as small as possible. In addition, in this case, the area of the thick brazing material layer at the inward portion surrounded by the convex portion becomes relatively large, and the effect as a buffer material for stress due to the difference in thermal expansion coefficient between the two members increases. Because. The width W depends on the size or diameter of the joining surface. However, it is preferable that the width W be as small as possible in a tappet or a valve lifter as long as the positioning of both members at the time of brazing is not hindered.

As in the above-described embodiment (see FIG. 2), the projection is preferably formed in a ring shape continuously along the periphery of the brazing joint surface. However, although not shown, one part is formed in a notch shape or, as shown in FIG. 5, the projection 25 is divided into a plurality of parts in plan view along the periphery of the brazing joint surface 2a. May be formed discontinuously. By doing so, as described above, the voids and impurities contained in the brazing material are extruded from the projections 25 and between the projections 25 conveniently.

In the above embodiment, the metal member is the tappet body for the engine, and the ceramic member forms the cam contact surface. However, the ceramic member to which the present invention can be applied is not limited to this. In addition, the brazing material, by metallizing the joining surface of the ceramic member,
It is also possible to use other than active low. As the brazing material, those having various compositions may be used according to the joined body.

[0026]

As is clear from the above description, the joined body according to the present invention has the following effects. That is, in the process of brazing the two members, the joined body is joined by, for example, placing a weight on the upper ceramic member and heating the material under the weight to reflow the brazing material between the joining surfaces. At this time, the ceramic member in a state of being floated on the molten solder compresses the molten solder material layer by the weight. Thus, the brazing material layer between the joining surfaces of the two members has an extremely small thickness at the leading end surface of the convex portion provided along the peripheral edge of the metal member, and the two members are substantially at the leading end surface of the convex portion of the metallic member. Contact state. That is, the ceramic member is stabilized without being unstably floated on the molten solder existing on the joining surface of the metal member. Therefore, the thickness of the brazing material layer between the joining surfaces is thinner at the tip end surface of the convex portion, but is substantially equal to or larger than the height of the convex portion at the inner portion surrounded by the convex portion. It will be thick. Therefore,
The ceramic member is brazed without inclination.

In addition, since the convex portion is located on the peripheral edge of the joining surface, the thickness of the brazing material layer at the inner portion surrounded by the convex portion is uniform. That is, since there is no convex portion on the inward portion, a large stress is not locally generated on the inward portion of the joining surface of the ceramic member. Therefore, even when used as an engine tappet or the like, the ceramic member has Less likely to cause damage.

[Brief description of the drawings]

FIG. 1 is a front view and an enlarged sectional view of a main part of an embodiment of a brazed joint according to the present invention.

FIG. 2 is a plan view of a joining surface of a metal member forming the joined body of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of a main part of another embodiment of a projection.

FIG. 4 is an enlarged sectional view of a main part of another embodiment of a projection.

FIG. 5 is a plan view showing another example of the projection on the joining surface of the metal member forming the joined body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Joined body 2 Metal member 2a Brazing joint surface of metal member 3 Ceramic member 3a Brazing joint surface of ceramic member 4 Row material layer 5,15,25 Convex part

Claims (4)

[Claims] 1. A brazed joint formed by joining a metal member and a ceramic member by brazing, wherein the metal member and the ceramic member have a constant height along a peripheral edge of at least one of the brazed joint surfaces of the metal member and the ceramic member. A brazed joint comprising a projection. 2. A brazed joint formed by joining a metal member and a ceramic member by brazing, wherein a protrusion having a constant height is provided along a peripheral edge of a brazing joint surface of the metal member. A brazed joint. 3. The brazed joint according to claim 1, wherein the convex portion is provided continuously along a peripheral edge of the brazed joint surface. 4. The brazed joint according to claim 1, wherein the protrusions are provided discontinuously along a peripheral edge of the brazed joint surface.