JPH0979012A - Manufacturing method of engine cylinder head - Google Patents

Abstract

(57) Abstract: In a method of immersing and joining a valve seat base material in a cylinder head body by heating and pressure welding, the embedded amount of the valve seat base material varies. SOLUTION: The set state of the valve seat base material 20 on the cylinder head body 11 is such that the bottom surface 51 of the valve seat base material 20 is located at the apex 45 of the ridge 46 of the valve seat seating surface 40.
Are in line contact with each other, and an angle α formed by the valve seat seating surface 40 and the outer peripheral surface 50 of the valve seat base material 20 and an angle β formed by the valve seat seating surface 40 and the bottom surface 51 of the valve seat base material 20 are It was set to satisfy α ≧ β.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an engine cylinder head in which a valve seat is joined to an opening of a suction / exhaust port of a cylinder head body on the combustion chamber side.

[0002]

2. Description of the Related Art A four-cycle OHC type engine is generally used for vehicles such as automobiles, and the cylinder of the engine has recently been constructed by a combination of an aluminum alloy cylinder block and a cylinder head. There is. The cylinder head has a combustion chamber defined between a piston reciprocating in the cylinder block and an intake / exhaust port communicating with the combustion chamber. It is composed of a valve seat attached to the opening of each port on the combustion chamber side. The valve seat is attached to a portion where the valve face surfaces of the intake valve and the exhaust valve are in contact with each other. This valve seat is formed of an iron-based sintered alloy or the like having excellent wear resistance and high-temperature strength because the intake / exhaust valve is repeatedly contacted and exposed to high heat.

As a method for mounting the valve seat on the cylinder head body, a press-fitting method has been conventionally used. However, in this press-fitting type, the thermal resistance at the time of heat transfer to the cylinder head body is increased due to the difference in thermal conductivity due to different metals and the minute gap existing at the interface between the two, and as a result, the cylinder head It had a risk of causing abnormal combustion due to insufficient cooling and overheating of the valve. In order to eliminate such problems due to the press-fitting type, at the valve seat mounting part of the cylinder head body,
The powder laser of valve seat material with excellent heat resistance, abrasion resistance, and corrosion resistance is heated and melted to be clad.
A laser clad method has been proposed in which a valve seat is formed by machining the build-up layer (see, for example, JP-A-62-150014).

However, in this laser clad method,
When the powder of the valve seat material is melted, the cylinder head body side is also melted. Therefore, so-called material defects such as blowholes due to gas generation, shrinkage cavities due to solidification shrinkage, or disappearance of strength improvement treatment previously performed on the cylinder head main body occur, and there is a drawback that joint strength is insufficient or deformation is likely to occur. Have

Therefore, the present inventors propose a technique for joining the valve seat base material made of an iron-based sintered alloy by heating and pressure-bonding, as a solution to the drawbacks of the above-mentioned valve seat joining method. (Japanese Patent Laid-Open No. 5-287324).
This is because the aluminum alloy cylinder head body is electrically heated to generate a compositional flow, and at the same time, the valve seat base material is heated and pressure-bonded to be embedded in the cylinder head body. It is a method in which they diffuse to each other and both are firmly fixed without a gap.

FIG. 16 shows the method. FIG. 1 is an enlarged cross-sectional view of a part of the cylinder head body 1 and the valve seat base material 2. The annular valve seat base material 2 is set on the valve seat seating surface 3 formed on the cylinder head body 1 ( (State of broken line), after the valve seat base material 3 is buried in the cylinder head body 1, the valve seat base material 2
The surplus part of is ground and finished. FIG. 16 also shows the set buried amount range of the valve seat base material 2 with which the required bonding strength is obtained. According to this method, the valve seat base material 2 and the cylinder head body 1 are hardly melted, so that a material defect does not occur, and a thermal resistance between them is suppressed, and a cylinder head which does not generate a thermal influence is obtained.

[0007]

However, even in the above method, the following problems to be solved remain. First, there is a variation in the amount of burial of the valve seat base material 2 with respect to the cylinder head body, and if the burial amount exceeds the set range, a problem occurs. That is, as shown in FIG. 17A, when the buried amount of the valve seat base material 2 is small, the pressure contact area is small, so that the bonding strength becomes insufficient and the valve seat base material 2 may be peeled off. FIG.
As shown in (b), when the valve seat base material 2 is buried too much, a hollow portion indicated by G is generated, and a gap is formed between the valve face and the valve face to impair the valve function. As shown in FIGS. 18 (a), (b), and (c), the variation in the amount of burial is caused when the valve seat base material 2 is in surface contact with the valve seat seating surface 3 (line contact in cross section). Due to the tolerance, the contact area changes as the relative positional relationship between the two changes. When the contact area changes, it is easily inferred that the amount of heat generated due to the resistance at the time of press contact varies, and thus the amount of burial varies.

Further, in the portion of the valve seat seating surface 3 where the valve seat base material 2 is in close proximity, the current density preferentially flows when the cylinder head body 1 is energized, so that the current density rises and is easily melted. . The valve seat base material 2 shown in FIG. 19 (a) has an outer peripheral surface 2a that is inclined so that the outer diameter becomes gradually smaller toward the cylinder head body 1 side, and the outer peripheral surface 2a is continuous with the outer peripheral surface 2a. It has a bottom surface 2b that is inclined so as to be unevenly distributed toward the cylinder head body 1 side toward the center. FIG.
As shown in 9 (b), the outer peripheral surface 2 of the valve seat base material 2
When a is close to the cylinder head body 1, the close portion H is likely to melt. Therefore, in the state where the valve seat base material 2 is buried and ground, the adjacent portion remains as a molten layer at the interface between the valve seat and the cylinder head body 1. Therefore, peeling of the valve seat is likely to occur.

The present invention has been made in view of the above circumstances, and is set in a method of burying a valve seat base material in a cylinder head body by heating and pressure welding so as to suppress variations in the burial amount of the valve seat base material. The purpose is to prevent the peeling of the valve seat by staying within the buried amount and preventing the molten layer from remaining.

[0010]

The present invention has been made to achieve the above object, and in Claim 1, an annular valve seat formed in an opening portion of a cylinder head body to a combustion chamber. In a method of manufacturing an engine cylinder head, in which an annular valve seat base material made of a material different from that of the cylinder head main body is set on the seating surface, and the valve seats are joined by heating and pressure welding, the valve seat seating surface is provided with two surfaces. An annular ridge protruding toward the inner peripheral side is formed, and the outer diameter of the valve seat base material, which is set on the valve seat seating surface, gradually decreases toward the cylinder head body side. Thus, the outer peripheral surface is inclined, and the bottom surface which is continuous with the outer peripheral surface and inclines so as to be unevenly distributed toward the cylinder head body side toward the axis center of the outer peripheral surface. It is characterized in that the bottom surface is brought into contact with the apex of the convex. According to a second aspect of the invention, in the invention of the first aspect, an angle α formed by the valve seat seating surface and the outer peripheral surface and an angle β formed by the valve seat seating surface and the bottom surface are set so as to satisfy α ≧ β. It is characterized by

[0011]

DETAILED DESCRIPTION OF THE INVENTION A. One Embodiment Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. A-1. Overall Structure of Cylinder Head FIG. 1 is a partial sectional view of a cylinder head according to the present invention, FIG.
1 is a view taken in the direction of arrow II in FIG. 1, and FIG. 3 is a sectional view showing a state in which the valve seat base material is set on the valve seat seating surface. FIG. 3 is an enlarged view of only a part of the cylinder head body and the valve seat base material. In these drawings, 11 is a cylinder head body of a 4-cycle OHC type engine. The cylinder head body 11 is made of aluminum alloy by casting. The cylinder head main body 11 is provided with a recess 12 for forming a combustion chamber defined between the piston and the piston that reciprocates in a cylinder block (not shown) toward the lower surface. Two intake ports 13 and two exhaust ports 14 that open to the recess 12 are formed on both sides of each. Note that FIG. 3 shows a state in which the lower surface of the cylinder head body 11 (the surface where the recess 12 is opened) is directed upward.

The aluminum alloy used as the material of the cylinder head body 11 is an Al-Si-Mg-based aluminum alloy defined as JIS AC4C. The reason why this material is selected is that the valve seat described later can be joined most strongly as compared with the case of using other aluminum alloys. As shown in FIG. 1, an intake valve 17 and an exhaust valve 18 are attached to the upper wall portions of the intake port 13 and the exhaust port 14 via valve guides 15 and 16, respectively. Opening 1 of both ports 13 and 14
A valve seat seating surface 40 is formed on 3a and 14a, and a valve seat 19 described later is joined to the valve seat seating surface 40. The valve guide 15,
16 is press-fitted and fixed in a valve guide hole 11a formed in the cylinder head body 11. The valve guide hole 11a is formed so that its axis C coincides with the axis of the openings 13a and 14a of the ports 13 and 14, respectively. In addition, 8 in FIG. 2 is a plug attachment hole.

The valve seat 19 shown in FIG. 1 is joined by press-contacting the annular valve seat base material 20 shown in FIG. 3 to the valve seat seating surface 40 under heating conditions, and finished. It is the latter one. As shown in FIG. 3, the valve seat seating surface 40 has the opening 1
A plane 41 orthogonal to the axes of 3a and 14a, first and second inner tapered surfaces 42 and 43 continuous from the plane 41 to the ports 13 and 14, and an outer tapered surface 44 continuous to the recess 12.
It is composed of Plane 41 and first inner tapered surface 4
The two convex surfaces of No. 2 form an annular projection 46 that protrudes toward the inner peripheral side of the openings 13a and 14a and has an apex 45 of an obtuse angle.

As shown in FIG. 3, the valve seat base material 20 is formed by covering the surface of an iron-based sintered alloy annular body 21 with a copper film 22. In the present embodiment, as the material of the annular body 21, a material in which copper is infiltrated is adopted from the viewpoint that resistance heat is unlikely to be internally generated during energization, which will be described later. The film 22 is formed by electroplating the torus 21 so that the film thickness is 0.1 μm to 30 μm.

The valve seat base material 20 has an annular shape as a whole, but its axial cross section has an outer peripheral surface 50,
It is formed of a bottom surface 51, an inner peripheral surface 52 and an upper surface 53. As shown in FIG. 3, the outer peripheral surface 50 is inclined so that the outer diameter becomes gradually smaller toward the cylinder head body 11 side, and the bottom surface 51 is continuous with the outer peripheral surface 50.
Cylinder head body 1 gradually increases toward the axis
It is inclined so as to be unevenly distributed on the first side. The inner peripheral surface 52 is an inclined surface 52a that is substantially parallel to the outer tapered surface 44 of the valve seat seating surface 40, and an axially extending surface 52b that extends in parallel to the axial direction from the inner peripheral end of the inclined surface 52a. It is formed from and. The upper surface 53 connects the outer peripheral surface 50 and the inclined surface 52 a, and is formed substantially parallel to the flat surface 41 of the valve seat seating surface 40.

As shown in FIG. 3, when the valve seat base material 20 is set on the valve seat seating surface 40, the bottom surface 51 contacts the apex 45 of the ridge 46, and the large-diameter side end portion is the recess 12. Angle α formed by the outer tapered surface 44 and the outer peripheral surface 50 that make up the valve seat seating surface 40.
And the angle β formed by the first inner tapered surface 42 and the bottom surface 51 forming the valve seat seating surface 40 is set to satisfy α ≧ β.

A-2. Joining Method of Valve Seat Base Material The valve seat base material 20 is bonded to the valve seat seating surface 40 of the cylinder head body 11 by using the press device 24 shown in FIGS. 5 and 7. In this press device 24, a lower platen 26 is fixed to a lower portion of a base 25, and an upper platen 27 is disposed above the lower platen 26 so as to come in contact with and separate from the lower platen 26 so as to be lifted and lowered. There is. The upper platen 27 is a cylinder device 2 mounted on the upper part of the base so that the axis of the upper platen 27 is oriented vertically.
The lower end of the rod 28a, which is the working end of 8, is fixed.

Lower platen 26 and upper platen 27
Has a structure in which power is supplied from a power supply device (not shown) via the conductive members 26a and 27a, respectively. The conductive member 27a connected to the upper platen 27 is configured to be deformed or moved up and down according to the lifting operation of the upper platen 27. Further, in this embodiment, the upper platen 27 serves as an anode and the lower platen 26 serves as a cathode. On the upper part of the base that supports the cylinder device 28, a laser beam is reflected by a reflecting member 29 fixed to the front part of the upper platen 27.
A laser displacement meter 30 that measures the amount of displacement of the upper platen 27 from the distance from 9 is attached.

The valve seat base material 2 is pressed by the pressing device 24.
In order to join 0, first, the lower electrode 31 is fixed on the lower platen 26, and the cylinder head body 11 is placed and fixed on the lower electrode 31. At this time, the cylinder head body 11 is positioned so that the recess 12 side faces upward and the axis line at the opening of the port that joins the valve seat base material 20 coincides with the axis line of the rod 28a of the cylinder device 28. deep.

Next, as shown in FIG. 7, the guide rod 32 is fitted into the valve guide hole 11a of the port for joining the valve seat base material 20 from the recess 12 side. This guide rod 32
Is a metal round bar 32a whose outer peripheral surface is covered with an insulating material 32b such as alumina, and is inserted into the valve guide hole 11a and positioned and held by a stopper 32c. It is formed to have a length projecting upward from the end face. In the present embodiment, the insulating material 32b is formed by spraying a ceramic material such as alumina onto the round bar 32a, and then polishing and finishing.

Next, the valve seat base material 20 is overlaid on the port opening, and the valve seat base material 20 is covered with the upper electrode 33.
Put. The upper electrode 33 has a through hole 33a formed in the axial center of a metal columnar body, into which the guide rod 32 is fitted, and has a lower end portion with an inclined surface 52 of the valve seat base material 20.
a taper surface 33b that is in close contact with a (FIG. 3) and a positioning peripheral surface 33c that is in close contact with the axially extending surface 52b over the entire circumference.
And form. A magnetic body 33d for magnetically attracting the valve seat base material 20 is fixed to the lower end of the upper electrode 33.

That is, by fitting the guide rod 32 into the through hole 33a of the upper electrode 33, the upper electrode 3
3 is positioned coaxially with the opening of the port of the cylinder head body 11. Further, by bringing the tapered surface 33b and the peripheral surface 33c into close contact with the valve seat base material 20, the valve seat base material 20 is positioned by the fitting so as to be coaxial with the port opening.

After placing the upper electrode 33 on the valve seat base material 20 in this manner, the upper electrode 33 is rotated to inspect whether the valve seat base material 20 is securely fitted.
Then, the cylinder device 28 is driven to drive the upper platen 2
7 is lowered and brought into close contact with the upper electrode 33. At this time,
The lower surface of the upper platen 27 and the upper surface of the upper electrode 33 are made parallel to each other. Next, the cylinder device 28 is driven to lower the upper platen 27, and the valve seat base material 20 is pressed against the cylinder head body 11 through the upper electrode 33 with a constant pressure. At this time, the direction of the pressure applied to the valve seat base material 20 is the upper electrode 3
Since the moving direction of 3 is restricted by the guide rod 32, it coincides with the axial direction of the openings 13a and 14a. Therefore, the valve seat base material 20 is pressed along the axes of the openings 13a and 14a with the axes aligned with each other.

The pressing force is changed based on the pressing force pattern shown in FIG. That is, a relatively low constant first pressure P ₁ is applied at the beginning of the joining process, and thereafter a relatively high constant second pressure P ₂ is applied until the end of the descent.

After starting the pressurization by the first pressing force P ₁ ,
When the upper platen 27 becomes stable, the distance between the upper platen 27 and the reflecting member 29 is measured by the laser displacement meter 30, and this distance is recorded as the lowering start position of the upper platen 27. In addition, after a lapse of a certain time from the start of pressurization by the first pressing force P ₁ , a voltage is applied to the platen 27 and the lower platen 26 so that a voltage is applied between these platens, that is, the upper electrode 3
3, a current is passed through the valve seat base material 20, the cylinder head body 11, and the lower electrode 31. At this time, the current flows from the upper electrode 33 toward the cylinder head body 11.
The current value at this time is changed based on the energization pattern shown in FIG.

The energization pattern is such that after the first current I ₁ is passed for a time t ₁ , a rest time r ₁ is once given, and then a second current I ₂ having a higher current value than the first current I ₁ is applied for a time t 1. _{After two} flows, the rest time r ₂ is given again, and finally the second current I ₂
A third current I ₃ having a higher current value than that is passed for a time t ₃ and the current value is set to 0 while the second pressing force P ₂ is being applied at the end of the joining. That is, the current value is gradually increased. The conversion from the first pressing force P ₁ to the second pressing force P ₂ is performed while the second current I ₂ is flowing and after the time t ₄ after switching to the second current I ₂ . Further, on the intake port 13 side and the exhaust port 14 side, the current value (current density) to be flown is changed so as to be larger on the exhaust port 14 side (for example, about 1.1 times). Below, the specific example of the electric current value in FIG. 8, time, and pressurizing force is shown.

A. Current value Intake port side I ₁ = 64kA, I ₂ = 68kA, I ₃
= 72 kA Exhaust port side I ₁ = 70 kA, I ₂ = 75 kA, I ₃
= 80 kA (both ± 4 kA) b. Time (common to both intake port side and exhaust port side) t ₁ , t ₂ , t ₃ = 0.1 second (6/60 seconds) t ₄ = 0.05 second (3/60 seconds) r ₁ , r ₂ = 1/60 second c. Pressurization (common to both intake port side and exhaust port side) P ₁ = 12kN P ₂ = 24kN

At this time, as shown in FIG. 3, in the valve seat base material 20, the bottom surface 51 has the ridges 4 of the cylinder head body 11.
6 is in line contact with the apex 45, and the area of contact between the two is extremely small, so that the electrical resistance due to energization increases and this contact portion generates heat. This resistance heat is conducted to the entire contact interface between the valve seat base material 20 and the cylinder head body 11. When the temperature of the interface between the valve seat base material 20 and the cylinder head body 11 rises in this way, the material metals (copper of the film 22 and the cylinder head body 1 that are in pressure contact with each other in the solid state).
1 aluminum alloy) atoms become actively moving, and these atoms diffuse into each other.

Due to the mutual diffusion of atoms as described above, the composition in the vicinity of the interface becomes a eutectic alloy of the copper forming the film 22 and the aluminum alloy of the cylinder head body 11, and the composition of pure copper and cylinder Head body 11
At a temperature lower than that of the aluminum alloy, the solid phase can be changed to the liquid phase. A state near the interface at this time is schematically shown in FIG. In FIG. 9, the eutectic alloy layer in which the mutual diffusion of atoms occurs and the eutectic alloy is generated is indicated by a symbol A.

Subsequently, the temperature near the interface further rises,
When a part of the eutectic alloy layer changes to the liquid phase, the atom diffusion phenomenon becomes more active, and the interface between the solid phase and the liquid phase expands as the eutectic alloy layer grows. While the liquid phase of the eutectic alloy layer proceeds, the aluminum alloy of the cylinder head main body 11 adjacent to the eutectic alloy layer is such that the valve seat base material 20 is pressed by the first pressurizing force P _1. By the fact that the temperature is raised by resistance heat,
It causes plastic flow (plastic deformation). Since this plastic flow occurs substantially symmetrically in the up-and-down direction in FIG. 9 around the first contact portion, the liquid phase eutectic alloy is multiplied by the plastic flow to obtain the contact portion as shown in FIG. Be excluded outside of. In FIG. 10, the excluded portion of the eutectic alloy is indicated by the symbol B. At this time, the valve seat base material 20
By partially eutectic alloying the film 22 and removing it from the contact portion, a part of the torus 21 comes into contact with the aluminum alloy, and a diffusion phenomenon of atoms occurs between them. A portion where this diffusion phenomenon occurs is indicated by a symbol C in FIG.

As a part of the eutectic alloy layer is removed from the contact portion and the aluminum alloy causes plastic flow as described above, the valve seat base material 20 starts to be buried in the cylinder head body 11. . After the valve seat base material 20 starts to be buried in this way, the pressing force is increased to the second pressing force P ₂ . As the applied pressure increases, the amount of plastic flow of the aluminum alloy increases, and the amount of eutectic alloy to be excluded increases accordingly. As a result, a eutectic alloy made of a copper-aluminum alloy is newly generated in the unreacted portion of the contact portion, and the above-described phenomenon is repeated, and the eutectic alloy layer is liquid-phased and further eliminated. Along with this, a region where atoms mutually diffuse at the interface between the iron-based sintered alloy, which is the material of the annular body 21, and the aluminum alloy also expands.

The above reaction is allowed to proceed based on the pattern of energization and pressing force shown in FIG.
The valve seat base material 20 is joined. Not only while the current is flowing, but also after the power supply is cut off, the reaction proceeds until the temperature drops to the temperature at which the reaction cannot be performed, and the formation of the eutectic alloy layer → liquid layering → exclusion accompanied by plastic flow, And the phenomenon of mutual diffusion of atoms between the iron-based sintered alloy and the aluminum alloy occur simultaneously, the valve seat base material 20 continues to be buried, and as shown in FIG. It will be buried inside.

When the buried amount no longer increases, the pressurization by the cylinder device 28 is stopped and the laser displacement meter 30
After determining the final position of the upper platen 27 from the distance between the upper platen 27 and the reflecting member 29, the upper platen 27 is raised and the cylinder head body 11 is removed from the press device 24. It should be noted that the average current value and the total energization time are also obtained by the time all steps are completed. Next, the total burial amount of the valve seat base material 20 is obtained by calculating the height difference between the lowering start position and the final position of the upper platen 27. When this value is not within the range of a predetermined allowable value, it is considered that the joining is defective. In this embodiment, the allowable value is 0.5.
mm to 2.5 mm. Although the allowable value varies depending on the material of the cylinder head body 11, it is preferably about 1 mm to 1.5 mm.

The final finishing of the cylinder head is shown in FIG.
As shown in FIG. 1, the unnecessary portion is removed from the cylinder head body 11 to which the valve seat base material 20 is joined by mechanical processing such as grinding as shown in FIG. By performing this final finishing process, the torus 21
Unnecessary portions and the film 22 are removed, and the reference numeral C in FIG.
Cylinder head body 1 through the diffusion region of atoms shown by
The valve seat 19 joined to 1 is obtained. here,
In the valve seat 19, the dimensions A (projection line length that determines the projection area), B (maximum thickness), and θ (angle between the outer peripheral surface and the machined surface) in FIG. 12 are A ≧ 2 and B ≧ 0. .9, θ ≧
It is formed so as to satisfy the relationship of 30 °.

A-3. Effect of one embodiment The valve seat 19 and the cylinder head body 11 are firmly fixed to each other by atomic diffusion without a gap. Therefore, the thermal resistance of both is small, and the cooling performance of the cylinder head can be improved. Further, as described above, since the cylinder head body 11 does not melt during the manufacturing process,
Material defects such as blowholes and shrinkage cavities during solidification do not occur.

When the valve seat base material 20 is set on the valve seat seating surface 40, as shown in FIG.
The bottom surface 51 is in line contact with the apex 45 of the ridge 46. That is, the valve seat base material 20 is not in surface contact with the valve seat seating surface 40. When they are in surface contact, as described above, the buried amount of the valve seat base material 20 varies due to the influence of the processing tolerance. However, in the present embodiment, since the line contact is made, the contact area is always constant regardless of which valve seat base material 20, and therefore the calorific value is constant and the variation in the buried amount is suppressed, and the set buried position is reduced. It fits within the quantity. Therefore, a predetermined wall thickness is always maintained, and sufficient bonding strength can be obtained without fear of peeling, and
Good valve function is demonstrated without causing defects such as lack of meat.

As shown in FIG. 3, when the valve seat base material 20 is set on the valve seat seating surface 40, the angle α between the outer peripheral surface 50 and the outer taper surface 44, the bottom surface 51 and the first inner taper are set. The angle β with the surface 42 is set so as to satisfy α ≧ β. As a result, in the valve seat base material 20, the bottom surface 51 is closer to the cylinder head body 11 than the outer peripheral surface 50. Therefore,
As shown in FIG. 4, the electric current is not concentrated on the outer peripheral surface 50 side but dispersed, and rather flows preferentially from the bottom surface 51 side to the cylinder head body 11. For this reason, in the cylinder head body 11, the current density of the portion facing the bottom surface 51 becomes high, and it becomes easy to melt. However, the molten layer is removed outside the interface by the pressurization of the valve seat base material 20 and does not remain. As a result, the valve seat 19 is not peeled off due to a material defect.

After the valve seat base material 20 is buried,
As shown in FIG. 12, the finished valve seat 19 is formed so as to satisfy the relationship of A ≧ 2, B ≧ 0.9, θ ≧ 30 °. In the valve seat 19,
In order to prevent the cylinder head body 11 from sinking due to the explosion pressure or the seating impact of the valve face and damage to itself,
It is important that the area of the interface with the cylinder head body 11 and thus the surface pressure applied to the cylinder head body 11 is kept below a certain level, and the rigidity of itself is secured above a certain level. As a result of the experiment, as shown in FIG. 13, if the projection line length A is smaller than 2, the allowable surface pressure will be exceeded. Therefore, the projection line length A is preferably A ≧ 2. Also, FIG.
As shown in 4, when the wall thickness B is less than 0.9, the bending deformation rate is large, and when it is 0.9 or more, the bending deformation rate does not increase any more. Therefore, the wall thickness B is preferably B ≧ 0.9. Furthermore, FIG.
As shown in FIG. 5, if the angle θ between the outer peripheral surface 50 and the machined surface is not secured at least 30 °, that is, if the cross-sectional area is not secured as much, the probability that the valve seat 19 peels off increases. Therefore, θ ≧ 30 ° is desirable.

The current density at the time of joining the valve seat base material 20 is larger on the exhaust port 14 side than on the intake port 13 side. Exhaust port side valve seat 19
Is always exposed to high-temperature exhaust gas, and therefore is in a higher temperature environment than the intake port side, and it is preferable that the projection line length (projection area) is ensured to be larger than that of the intake port 13 side. As shown in FIG. 2, by making the current density on the exhaust port 14 side larger than that on the intake port 13 side, the projection line length of the valve seat 19 is secured on the exhaust port 14 side, so that depression or deformation is unlikely to occur. Become. Also,
On the intake port 13 side, a sufficiently large area of the opening 13a can be secured without sacrificing the distance between the valve seats 13.

When the valve sheet base material 20 is joined, good joining can be performed by adopting a pattern of energization and pressing force as shown in FIG. That is, since the current value is gradually increased in three steps across the _two pause times r ₁ and r ₂ , the temperature of the interface does not rise excessively, and the cylinder head body 11 melts to cause the liquid phase. Can be prevented from changing to. Further, if an excessive current is continued to flow without giving a rest time, the temperature of the annular body 21 of the valve seat base material 20 exceeds the phase transformation point of the steel as a result of the temperature rise due to resistance heating of the steel itself, and Martensitic transformation occurs in the cooling process. In this case, the hardness increases and the material lacks in toughness, so that the valve seat cannot sufficiently function. In addition, at the pressurizing force, a relatively small first pressurizing force P ₁ is applied at _first to prevent a sudden impact from being applied to the valve seat base material 20, and then the second current I ₂ is applied. Good joining can be performed by increasing the second applied pressure P ₂ during the process.

B. Modifications The present invention is not limited to the above-described embodiment, and various modifications can be made as follows. Cylinder head body 11 and valve seat base material 20
The material of is not limited to the above-mentioned one embodiment, and may be any material as long as a eutectic alloy is formed between the two. INDUSTRIAL APPLICABILITY The present invention can be applied not only to automobile engines but also to any engine such as motorcycle engines.

[0042]

As described above, according to the present invention,
Since the valve seat base material is set in line contact with the valve seat seating surface of the cylinder head body, when the valve seat base material is joined to the cylinder body by heating and pressure contact, the calorific value is constant and the variation in the buried amount is suppressed. Therefore, a predetermined wall thickness is always maintained, and sufficient bonding strength can be obtained without fear of peeling. (Claim 1). The current at the time of joining is not concentrated on the outer peripheral surface side of the valve seat and is dispersed, and the ratio of the current flowing from the bottom surface side to the cylinder head body increases, so the current density of the part facing the bottom surface becomes high and it becomes easier to melt, Since the molten layer is removed and does not remain outside the interface due to the pressurization of the valve sheet base material, peeling of the valve sheet due to material defects does not occur. (Claim 2).

[Brief description of drawings]

FIG. 1 is a side sectional view showing a valve seat according to an embodiment of the present invention.

FIG. 2 is a view on arrow II in FIG.

FIG. 3 is a side sectional view showing a state in which a valve seat base material is set on a valve seat seating surface.

FIG. 4 is a side sectional view showing a state where the valve seat base material is buried in the valve seat seating surface.

FIG. 5 is a plan view showing a pressing device for joining the valve seat to the port opening of the cylinder head.

FIG. 6 is a side view showing a pressing device for joining the valve seat to the port opening of the cylinder head.

FIG. 7 is a side cross-sectional view showing a state where an electrode is brought into contact with a valve seat base material.

FIG. 8 is a diagram showing a pattern of energization and pressure.

FIG. 9 is a side cross-sectional view showing a state in which an alloy layer made of the metallic material of the film of the valve seat base material and the metallic material of the cylinder head body is formed.

FIG. 10 is a side cross-sectional view showing a state where the metal material of the cylinder head body is in plastic flow.

FIG. 11 is a side sectional view showing a state where the valve seat base material is buried in the cylinder head body.

FIG. 12 is a side sectional view showing a state where the valve seat is finished.

FIG. 13 is a graph showing an example of the relationship between the projected line length of the valve seat and the surface pressure.

FIG. 14 is a graph showing an example of the relationship between the wall thickness of the valve seat and the bending deformation rate.

FIG. 15 is a graph showing an example of the relationship between the outer peripheral surface of the valve seat and the probability of peeling.

FIG. 16 is a side sectional view for explaining a conventional method of joining a valve seat base material to a cylinder head body.

17 (a) is a side sectional view showing a defect when the valve seat base material has a small embedded amount, and FIG. 17 (b) is a side sectional view showing a defect when the valve seat base material has an excessively embedded amount. is there.

18 (a), (b) and (c) are side sectional views showing a state where the valve seat base material is in surface contact with the cylinder head body.

FIG. 19 (a) is a side sectional view showing a set state in which the outer peripheral surface of the valve seat is closer to the cylinder head body than the bottom surface, and FIG. 19 (b) shows the valve seat base material buried in the valve seat seating surface. FIG. 3 is a side cross-sectional view showing a state in which

[Explanation of symbols]

11 ... Cylinder head body, 13a ... Intake port side opening, 14a ... Exhaust port side opening, 19 ... Valve seat, 20 ... Valve seat base material, 40 ... Valve seat seating surface, 41 ... Plane (two surfaces) One surface), 42 ... first inner tapered surface (the other surface of the two surfaces), 45 ... vertex, 46 ... ridge, 50 ... outer peripheral surface of valve seat base material, 5
1 ... Bottom of valve seat base material.

Claims (2)

[Claims] 1. An annular valve seat base material made of a material different from that of the cylinder head body is set on an annular valve seat seating surface formed in an opening of the cylinder head body toward the combustion chamber, and then heated and pressure-welded. A method for manufacturing an engine cylinder head, in which a valve seat is joined to a valve seat by forming a ring-shaped protrusion on the seating surface of the valve seat, the annular projection being formed of two surfaces and protruding toward the inner peripheral side of the opening. The base material, when set on the seating surface of the valve seat, has an outer peripheral surface that inclines so that the outer diameter becomes gradually smaller toward the cylinder head body side, and is continuous to this outer peripheral surface, And a bottom surface that is inclined so as to be unevenly distributed toward the cylinder head main body side, and the bottom surface is in contact with the apex of the ridge. Method for manufacturing an engine cylinder head. 2. An angle α formed between the valve seat seating surface and the outer peripheral surface and an angle β formed between the valve seat seating surface and the bottom surface in a state where the valve seat base material is set on the valve seat seating surface. And α is α ≧ β, the method for manufacturing an engine cylinder head according to claim 1, wherein