JPH1142513A - Press-in join method of aluminum-made outer and iron-made inner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of obtaining joining force equal to or more than that in the past in the case of pressing an iron-made inner into an inner hole of an aluminum-made outer for join, by using a smaller and thinner member. SOLUTION: In this press-in join method, on a peripheral surface 2 of an inner 1, a plurality of protrusive streaks in parallel or at a tilt angle 30 deg. or less relating to an axial center in a height 7 to 200 μm are provided, also the peripheral surface 2 is formed in truncated cone shape having a lower bottom in a press fit forward side, in a press-in forward side of the inner 1 in an inner hole of an outer 5, a level difference part 51 into contact with an end face of the inner 1 is provided, also an inner hole diameter in a side of the level difference part 51 is formed larger than an inner hole diameter in an inlet side, in the inner hole of the outer 5, the inner 1 is pressed in by an interference fit along a ridge line of the protrusive streak.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of firmly press-fitting an inner member made of iron to a housing made of an aluminum alloy, and more particularly to a method of joining a member such as a valve seat for intake or exhaust of an internal combustion engine. Can be used.

[0002]

2. Description of the Related Art A valve seat of an internal combustion engine is known as a structure in which an iron member is press-fitted into a hole of an aluminum alloy member. This is a joining on a cylindrical surface, and press-fitting is performed at room temperature, shrink fit or cold fit with the dimensional relationship between the hole member (outer) and the shaft member (inner) being a tight fit.

[0003]

In order to strengthen the joint by press-fitting, it is necessary to increase the press-fitting amount of the interference fit or to increase the area of the joint surface. Is increased, and there is an increased concern that deformation or cracks or other defects may occur. In the latter case, the diameters and lengths of the two members are increased, resulting in inconveniences such as an increase in the size of the device and an increase in the amount of heat storage. In view of the above circumstances, an object of the present invention is to provide a method for easily generating a bonding force equal to or higher than that of the related art by using smaller and thinner members.

[0004]

In order to solve the above-mentioned problems, a joining method according to the present invention is arranged such that an outer peripheral surface serving as a joining surface of an iron inner is parallel to an axis or has an inclination angle of 30 ° or less and a height of 30 ° or less. And a plurality of ridges continuous or intermittent in the press-fitting direction, and the outer peripheral surface is formed in a truncated conical shape having a lower bottom on the press-fitting front side, and the inner hole of the inner hole of the aluminum outer is provided. On the press-fitting front side, a stepped portion is provided which is in contact with the end face of the inner, and the inner hole diameter on the stepped portion is formed larger than the inner hole diameter on the inlet side, and the inner is formed along the ridgeline of the ridge on the inner hole of the outer. It is characterized by press-fitting with interference fit. The “tilt angle” refers to an angle formed by a line intersecting a plane passing through the axis and the outer peripheral surface and the ridge.

[0005] The inner hole of the aluminum outer has a truncated cone shape having a lower bottom on the front side of the inner press fit, or a cylindrical shape parallel to the axis, and has a large diameter portion on the step side. The inner or outer truncated cone is characterized in that the difference in diameter between the lower and upper portions of the bottom other than the ridge is 10 to 40 μm.

In these methods, press-fitting is performed to a predetermined position under an impact force, and at least one of an inner hole of an aluminum outer and an iron inner is heated to a temperature of 400 to 600 ° C.
And press-fitting the inner into the outer, and then pressing the peripheral end face of the inner hole entrance of the outer to plastically deform the outer.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The outer in the present invention is intended to be made of an aluminum alloy, and its hole is formed by cutting. The iron inner is made of a molten material or a sintered alloy, is harder and stronger than the outer aluminum alloy, and is formed into a columnar or cylindrical shape.

The outer peripheral surface of the iron inner is frustoconical (tapered) having a lower bottom on the front side of the press-fitting. And one provided with a chamfer or a small diameter portion on the lower bottom side so as to be easily attached to the outer hole. As described later, the outer peripheral surface of the inner part corresponding to the valley portion of the ridge is set so that the fitting when press-fitting into the outer hole has the dimensional relationship of the interference fit. In addition, the difference in diameter between the lower and upper portions of the truncated cone other than the ridge (the difference in diameter between the upper and lower ends of the outer peripheral surface) is 10 to 40 μm.
It is. Since the outer hole and the inner are set in a dimensional relationship of the interference fit, if the diameter difference is too large, the bottom size of the inner becomes significantly larger than the inlet size of the outer hole. Since the inlet is sheared or pushed open to cause cracking, the upper limit is set to 40 μm and the thickness, shape, material and the like are taken into consideration. Also, the reason for forming the truncated cone (taper) having a lower bottom on the front side of the press-fitting of the iron inner is that when the press-fitting is performed, it is adapted to the large-diameter portion on the step portion side of the outer as described later. Therefore, a sufficient effect cannot be expected in a state where the diameter difference is small (close to a plain state) and less than 10 μm.

The ridges include those having a triangular, trapezoidal, semicircular, or tooth shape in cross section, or ridges formed on the outer peripheral surface when the inner cross section is polygonal. In that case, the edge of the ridgeline is clear, the one chamfered in an arc,
Any of those having a chamfered front side in the press-fitting direction can be applied. Also, the ridges are formed to have the same width and height in the vertical direction, but the width or height on the front side of the press-fitting is made small, and the width or height on the rear side is made large to facilitate press-fitting. There are cases. The ridge may be continuous from one end to the other end, or may be one or more divided in the middle of the ridge. The latter can be obtained by manufacturing the former, and then cutting the outer peripheral surface in the circumferential direction using a lathe or the like to remove a part of the ridge. When the protruding ridge is divided and approaches the protruding shape, the form of joining by press fitting becomes complicated, and the joining force becomes relatively high.

The protruding ridges on the outer peripheral surface of the iron inner strongly bite into the aluminum outer at the time of press-fitting, and a new surface of aluminum appears and joins in a state of being adhered to the iron inner. You. The height of the ridge from the outer peripheral surface is 7 to 200 μm when the outer peripheral surface is cylindrical.
m. If it is less than 7 μm, no remarkable effect is observed. When it is higher than 200 μm, it is possible to increase the bite of the inner ridge into the inner hole of the outer member, but on the other hand, it tends to cause galling, the material distortion becomes large, and when the outer wall is thin, cracks occur. This is not preferable because the possibility of occurrence is increased and the inner peripheral surface (the valley of the ridge) may not strongly contact the inner hole surface of the outer. As for the number of the ridges on the outer peripheral surface, about 10 to 50 suffices for a general size having a diameter of about 20 to 50 mm. In the inner case where the outer circumference is a polygonal column and the ridge is parallel to the axis,
For a structural member of a general size, the number of corners of the outer periphery is 3
It is in the range of 6 to 180 angles.

The ridge may be straight in the vertical direction,
If it is inclined in the circumferential direction like a helical gear (helical gear), it can be screwed in, the detachment of the outer from the mounting hole becomes more difficult, and the length of the joint can be made smaller. it can. If the ridge has a slope in the circumferential direction,
Like the helical gear formed by the powder metallurgy method, the helical gear can be easily manufactured by using a forming die in which a forming die or a punch can rotate. The inclination angle of the ridge is 30
It is necessary to set it to ゜ or less, and if it is larger than that, it becomes difficult to screw it into the mounting hole. In order to screw the inner member, when the inner member is columnar, at the end surface of the inner member or at an outer diameter portion that does not fit, or at least one of the inner periphery or the end surface when the inner member is cylindrical, a convex portion or a concave portion is formed. A rotary wrench is provided by using a wrench tool having projections and depressions engaging with the projections and depressions. The unevenness is preferably a ratchet-like shape on the end face and a polygonal shape on the inner diameter face.

The inner hole of the aluminum outer is provided with a step on the front side of the inner press-fitting for abutting on the end face of the inner. The inner hole diameter on the side of the step portion is larger than the inner hole diameter on the inlet side. As the vertical cross-sectional shape of such an inner hole,
A truncated cone (tapered) shape with a lower base on the step side, a frustoconical shape with only a plane near the lower base (parallel to the axis), a plane parallel to the vertical direction (plain cylindrical shape) In some cases, the step side is hollowed out to a large diameter. When the inner hole surface has a truncated cone (taper) shape, the difference in diameter between the lower and upper frustum-shaped portions other than the ridges is 10 to 40 μm, as in the case of the inner. Also, in the latter case where the inner hole is plain and the step side is large in diameter, the inner hole inlet is set to a size that can be tightly fitted with the upper bottom diameter of the inner, and the large diameter part is made to an appropriate size .

In the method of the present invention, an iron inner having a plurality of ridges on its outer peripheral surface is pressed into the outer hole along the ridge of the ridge. At the time of press-fitting, the ridge of the inner strongly hits the inner wall of the outer mounting hole, and that part of the inner wall slides in with a higher surface pressure than the other parts, and the inner wall is plastically deformed and a high tension is obtained. Can be Further, since the outer member is made of an aluminum alloy, the oxide film on the surface of the aluminum alloy is destroyed on the contact surface, metal adhesion to the inner member occurs, and the fixing force increases. Also, since the inner has a large diameter at the press-fit front and the outer hole has a narrow entrance side and a large diameter at the back, when it is press-fitted by moderate plastic deformation and elastic deformation, as in the case where the taper is fitted, The inner is prevented from coming out, and one is restrained by the step of the outer, so that a stronger joint can be obtained together with the adhesion and the tightening force described above. Due to such an effect, even if the length of the inner joint portion is made smaller than that of the conventional one, the joining force becomes equal to or more than
The member can be made thin and small without detaching during use.

At the time of press-fitting, the press-fitting speed may be relatively small at 10 mm / sec or less,
By performing press-fitting under an impact force of about m or more, the tension force of the inner and outer members can be increased. In the case of high-speed press-fitting, the load of press-fitting increases, but the tightening force at the inner hole entrance of the aluminum outer can be made high, and adhesion tends to occur.

If the aluminum outer is press-fitted in a slightly softened state, the press-fitting becomes easier. For that purpose, the outer inner hole or the iron inner may be heated. The effect is large when applying a ridge in which the ridge is inclined in a helical shape. The temperature is between 400 and 600C, with 500C being optimal. If the temperature is too low, the effect of heating is small, and if the temperature is too high, the materials of both members change, and post-treatment is required, which is not preferable. There is a method in which an iron inner having little change in material due to heating is heated, fitted into a hole of an aluminum outer, and the outer is heated by heat conduction. In addition, it is desirable that the solution and the aged aluminum alloy have as little material change as possible,
It is preferable to heat only the vicinity of the inner hole while cooling the outer member.

[0016] By interposing a coating of copper, tin, zinc alloy solder or the like on the joining surface, the joining force is further increased. The coating is desirably formed on the outer peripheral surface of the iron inner by plating or applying a metal paint.

After the press-fitting, when the peripheral end face of the inner hole of the aluminum outer is pressed with a punch to cause plastic deformation and work hardening, the tightening force near the entrance of the outer inner hole is increased to improve the joining. Can be. In particular, when the press-fit amount of the outer and the inner is set to be large, or when the inlet of the outer is expanded by the inner, the effect is great, and the joining is more reliable.

[0018]

The present invention will be described below with reference to examples. FIG.
1A is a plan view of the inner 1, and FIG. 1B is a side view thereof. FIG. 1A is a schematic diagram showing the ridges 3 larger than the actual dimensional ratio, and FIG. 1B is a schematic diagram showing the ridges 3 only by line segments. The inner 1 is a member made of an iron alloy having a truncated cone having a lower bottom below the outer peripheral surface 2, and having a triangular cross section on the outer peripheral surface 2 and a ridge having a height of 30 μm.
The difference between the upper base diameter and the lower base diameter on the outer peripheral surface 2 is 20 μm. The inner 1 was made of a sintered alloy steel, and was manufactured by powder molding with a mold, sintering and sizing.

FIG. 2 is a side view schematically showing an example of the shape of the inner 1. 2 (a) is a truncated cone, FIG. 2 (b) is a crowned cone, and FIG. 2 (c) is a truncated cone having only a lower end in a cylindrical shape, and all have the same effect.

FIG. 3 is a longitudinal sectional view schematically showing an example of the shape of the inner hole of the outer 5. FIG. 3A shows a truncated cone shape, and FIG.
(B) is a truncated cone with a cylindrical shape near the lower step,
FIG. 3C shows a plain cylindrical shape having a truncated cone shape having a large diameter near the lower step portion. Further, FIG.
As in (c), the large-diameter portion has a disk shape. The outer 5 is cast and heat-treated, and the hole is formed by cutting. 3 (a) to 3 (d), the difference between the upper bottom diameter and the lower bottom diameter of the hole is set to be substantially the same as in the case of the inner 1, and is 20 μm. It is preferable that the diameter of the inlet of the hole is in an interference fit when the inner diameter of the inner surface of the inner surface of the inner surface 1 is fitted to the upper surface of the inner surface 2 and has the same size. A step portion 51 is formed at the lower bottom of the hole so that the large diameter portion 52 can contact the inner 1.

FIG. 4 is a partial longitudinal sectional view for explaining a state in which the outer 5 and the inner 1 are press-fitted and joined. At the time of press-fitting, the outer 5 is set on the base 6 of the press, and the inner 1 is press-fitted into the hole of the outer 5 by the pressing punch 7. The pushing punch 7 has a thrust bearing (not shown), and rotates following the inner 1 rotating along the inclined ridge. In some cases, it may be better to engage the upper end surface of the inner 1 with the lower end surface of the pushing punch 7 by providing unevenness and mechanically rotating the pushing punch 7 for press-fitting. The inner 1 shown is that shown in FIG. 1, and the outer 5 is shown in FIG.
The shape shown in FIG.

When the iron inner 1 is pushed into the hole of the aluminum outer 5, the ridge 3 is provided to be inclined like a helical gear, so that the inner 1 rotates so as to be screwed in.
The ridges 3 bite into the outer 5 to plastically deform the outer 5, and the outer peripheral surface 2 mainly deforms the outer 5 elastically. The rubbed surfaces of both members are in a cohesive state, and when the pushing is completed, the outer 5 is in a state of firmly gripping the inner 1 by elasticity. By the press-fitting, the lower bottom portion of the inner 1 comes into contact with the step portion 51 of the outer 5 and is accommodated in the large-diameter portion 52, so that the above-mentioned actions are hardly separated and a strong joint is obtained.

In the case of the above embodiment, the inlet 5 of the outer 5
The press-fit amount of the portion 3 is smaller than the large-diameter portion 52. Then, when the outer punch 8 presses the end face around the entrance 53 of the outer 5 and plastically deforms it, the inner 1 is more strongly squeezed and squeezed.

Since a stronger joining force can be obtained as compared with the conventional press-fitting joining, members having the same diameter but shorter joining length can be obtained.

[0025]

As described above, in the joining method of the present invention, the stepped portion is provided in the outer hole, and the inner hole diameter on the stepped portion side is formed larger than the inner hole diameter on the inlet side. It has a ridge in shape and is press-fitted from the bottom side, so the joining of both members by the ridge, the tightening force by interference fit, and the retaining effect by the combination of the step portion and the large diameter portion The connection between the two members can be further strengthened. Therefore, it is possible to further reduce the height and volume of the member, and it is possible to realize weight reduction, improvement in heat dissipation, and the like.

[Brief description of the drawings]

FIG. 1A is a plan view of an inner used in the present invention, and FIG. 1B is a side view thereof.

FIGS. 2A to 2C are side views schematically showing examples of inner shapes.

3 (a) to 3 (d) are longitudinal sectional views schematically showing examples of the shape of an inner hole of an outer.

FIG. 4 is a partial longitudinal sectional view illustrating a state in which an outer and an inner are press-fitted and joined.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner 2 Outer peripheral surface 3 Convex stripe 5 Outer 6 Base 7 Push punch 8 Outer punch 51 Step part 52 Large diameter part 53 Inlet

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jun Ehira, Nissan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture (72) Inventor Kunio Maki Nissan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture ( 72) Inventor Sadayuki Abo 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa

Claims (7)

[Claims] 1. A method for press-fitting and joining an iron inner into an inner hole of an aluminum outer, wherein an outer peripheral surface serving as a joining surface of the iron inner is parallel or inclined with respect to an axis.
゜ Below, the height is 7 to 200 μm, and a plurality of ridges continuous or intermittent in the press-fitting direction are provided, and the outer peripheral surface is formed in a truncated cone shape having a lower bottom on the press-fitting front side,
At the inner press-fitting front side of the inner hole of the aluminum outer, a stepped portion that comes into contact with the end face of the inner is provided,
The inner hole diameter on the step side is formed larger than the inner hole diameter on the inlet side,
A method of press-fitting an aluminum outer and an iron inner, wherein the outer and the inner are press-fitted along the ridge line of the ridge by interference fit. 2. An inner hole of the aluminum outer having a truncated conical shape having a lower bottom on the front side of the inner press-fit, or a cylindrical shape parallel to the axis and having a large diameter portion on the step portion side. 2. The method of press-fitting an aluminum outer and an iron inner according to claim 1, wherein: 3. The difference in diameter of the inner or outer truncated cone-shaped lower and upper portions other than the ridges is 10 to 40 μm.
3. The method of press-fitting an aluminum outer and an iron inner according to claim 1 or 2, wherein m is m. 4. The method of press-fitting an aluminum outer and an iron inner according to claim 1, wherein the press-fitting is performed by press-fitting to a predetermined position under an impact force. 5. The method according to claim 5, wherein at least one of the vicinity of the inner hole of the aluminum outer member and the iron inner member has a temperature of 400 to
The method of press-fitting an aluminum outer and an iron inner according to any one of claims 1 to 4, wherein the press-fitting is performed while heating to 0 ° C. 6. The aluminum outer according to claim 1, wherein, after the inner is press-fitted into the outer, the outer end is plastically deformed by pressing a peripheral end surface of an inner hole entrance of the outer. Press-fitting method between steel and iron inner. 7. The engine according to claim 1, wherein the outer is a cylinder head of an internal combustion engine, and the inner is a valve seat made of an iron-based sintered alloy.
7. The method of press-fitting an aluminum outer and an iron inner according to any one of items 1 to 6, above.