JP3070490B2 - How to fix the valve seat to the cylinder head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for fixing a valve seat of an internal combustion engine to a cylinder head.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 7-34965 discloses FIG.
As shown in the figure, a ring-shaped valve sheet material 11A coated with a surface treatment material 16 is placed on the cylinder head 13 in a state of contacting the tapered surface 13b of the cylinder head 13, and electricity is supplied while pressurizing the valve sheet material 11A. Accordingly, there is a description that the cylinder head 13 having a smaller deformation resistance than the valve seat member 11A is plastically deformed, and the valve seat member 11A is joined so as to be embedded in the tapered surface of the cylinder head 13. At the joint between the valve seat material 11A and the cylinder head 13 obtained by the above method, a layer of an intermetallic compound or a solid solution of the valve seat and the surface treatment material, the surface treatment material Since the layer, the surface treatment material, and the layer of the intermetallic compound or solid solution of the cylinder head are formed in this order, the valve seat and the cylinder head are metallically connected.

[0003]

During operation of the internal combustion engine, the valve seat is subjected to a thermal stress generated in the valve seat due to a difference in the coefficient of thermal expansion between the valve seat and the cylinder head. If the connection is broken, a crack may occur in the joint surface between the valve seat and the cylinder head, and the valve seat may fall off the cylinder head. An object of the present invention is to provide a method of fixing a valve seat to a cylinder head, which can prevent the valve seat from falling off the cylinder head even when a metallic connection is broken.

[0004]

The method of the present invention for achieving the above object is as follows. Forming a projection projecting in the axial direction on the valve seat material, forming a concave portion recessed radially outward on the side surface of the valve seat mounting portion having a seat surface and a side surface on the cylinder head; The projection of the material is applied to the seat surface of the valve seat mounting part, and the valve seat material is energized between the valve seat material and the valve seat mounting part while the valve seat material is pressed against the seat surface side of the valve seat mounting part, and is semi-melted by resistance heating There is no valve seat that closes the valve seat material to the valve seat mounting part by filling the gap between the valve seat material and the side surface including the concave part of the valve seat mounting part with at least the metal of the projection part of the valve seat material. Mechanically engaging and metallically joining the valve seat to the cylinder head. Method of fixing to the cylinder head.

According to the method of the present invention, when the valve seat is energized while being pressurized, at least the metal in the projection portion is semi-molten and flows radially outward and inward of the valve seat material. Filling the gap between the material and the valve seat mounting surface of the cylinder head and the gap between the valve seat material and the valve seat mounting side including the cylinder head recess,
While being metallically connected to the cylinder head, the cylinder head is mechanically engaged with the concave portion of the cylinder head in the axial direction while being prevented from falling off the cylinder head. Therefore, even if the metal connection with the cylinder head is broken, the valve seat does not fall off the cylinder head because it is engaged with the concave portion of the cylinder head.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view for explaining a step of fixing a sintered valve seat to a cylinder head according to an embodiment of the present invention, and FIG. 2 shows a valve seat obtained by the embodiment of the present invention. 2 shows a fixed cylinder head. 1 and 2, a method of fixing the valve seat to the cylinder head will be described below. First, iron-based (Fe-Mo-
Valve seat material 1 made of sintered material of Co-Ni-C)
A (for example, an inner diameter of 20 mm and an outer diameter of 25 mm) is formed with a projection 2 (for example, a height of 3 mm) having a triangular cross section that protrudes in the axial direction, and is used for the valve seat mounting portion of the aluminum alloy cylinder head 3. Seat 3a and side 3
b, a concave portion 4 (for example, a depth of 1 mm and a height of 1 mm) is formed on the entire circumference of the side surface 3b of the valve seat mounting portion having the width b. Then, the valve seat material 1A is inserted into the valve seat mounting portion from the combustion chamber 5 side of the cylinder head 3, and the projection 2 of the valve seat material 1A is applied to the seating surface 3a of the valve seat mounting portion of the cylinder head. 1A is placed on the seat surface 3a of the valve seat mounting portion. The valve seat material 1A and the cylinder head 3 are projected by the projection 2 of the valve seat material 1A.
A gap is formed between the valve seat mounting portion seating surfaces 3a except for the tip of the projection 2. Further, since the side surface 3b of the valve seat mounting portion of the cylinder head 3 is a tapered surface that expands in the radial direction from the concave portion 4 side toward the combustion chamber 5, the valve seat material 1A and the side surface of the valve seat mounting portion of the cylinder head 3 are formed. A gap is formed between 3b. (FIG. 1 (a)) Next, while pressurizing the valve seat material 1A to the seat surface 3a side of the valve seat mounting portion, electricity is supplied between the valve seat material 1A and the valve seat mounting portion. By the energization accompanied by the pressurization, at least the metal of the projection 2 portion of the valve seat material 1A flows into a semi-molten state (FIG. 1B), and the valve seat material 1A and the cylinder head 3
1 and the gap between the valve seat material 1A and the side surface 3b of the valve seat mounting portion including the recess 4 of the cylinder head (FIG. 1).
(C)) The valve seat 1 is solidified and mechanically engaged and metal-joined to the valve seat mounting portion of the cylinder head 3. After being fixed to the cylinder head 3, the valve seat 1 is machined into a desired shape and finished or deburred.

[0007] For example, F
e-Ni-Cr-Si-C, Fe-Mo-Co-Cr-
A conductive material having excellent wear resistance such as C is used. The concave portion 4 mechanically engages with the solidified portion of the valve seat 1 rushing into the concave portion 4 to prevent the valve seat 1 from falling off.
It is formed continuously or discontinuously in the circumferential direction on the side surface 3 b of the valve seat mounting portion of the port 6 of the cylinder head 3. The shape of the projection 2 is such that when the projection 2 is energized while being pressurized, the plastic flow is greatest in the vicinity of the contact surface with the cylinder head 3 and the valve seat material 1A and the seating surface of the valve seat mounting portion of the cylinder head 3 The width of the cross section becomes smaller toward the tip so that the gap 3a and the gap between the valve seat material 1A and the side surface 3b of the valve seat mounting portion including the recess 4 of the cylinder head 3 can be filled.

Next, the operation of the embodiment of the present invention will be described.
In the method of the embodiment of the present invention, the valve seat material 1A (having a melting point of about 1200 to 1300 ° C.) is energized while being pressurized, so that the metal near the contact portion of the projection 2 of the valve seat material 1A with the cylinder head 3 is formed. Generates heat due to resistance and rises to a temperature close to the melting point, and becomes a semi-molten state. The projection 2 in the semi-molten state has a gap between the valve seat material 1A and the seating surface 3a of the valve seat mounting portion of the cylinder head 3 and the valve seat material 1
The fluid flows into a gap between A and the side surface 3b of the valve seat mounting portion including the concave portion 4 of the cylinder head. Since the pressurizing and energizing of the valve seat material 1A are continued even while the metal is flowing, the flowing metal is maintained in a semi-molten state due to heat generation due to resistance near the contact portion with the cylinder head 3. Although the cylinder head 3 is formed of an aluminum alloy having a melting point of about 600 ° C., since the heat capacity is large and the aluminum alloy has a high thermal conductivity, even if the projection 2 is close to 1000 ° C., And the vicinity of the contact surface only melts a few μm. Therefore, the cylinder head 3 is metal-bonded to the projection 2 (including the flowed portion) which is in a semi-molten state without being greatly deformed even under the pressure from the projection 2. As described above, the metal in the projection portion is semi-molten and the valve seat material 1A and the cylinder head 3
When the valve seat 1 solidifies by filling the gap between the seating surface 3a of the valve seat mounting portion and the gap between the valve seat material 1A and the side surface 3b of the valve seat mounting portion including the concave portion 4 of the cylinder head 3, It is metal-bonded to the cylinder head 3 and mechanically engages with the concave portion 4 of the cylinder head 3 by axially engaging the solidified portion flowing into the concave portion 4. Therefore, even if the metal connection between the valve seat 1 and the cylinder head 3 is broken, the valve seat 1 is prevented from falling off from the cylinder head 3 by mechanical engagement with the recess 4 of the cylinder head 3.

FIG. 3 shows a valve seat 1 of a cylinder head 3 (having a recess 4 in a side surface 3b of a valve seat mounting portion of the cylinder head 3) on which a valve seat 1 obtained by a method according to an embodiment of the present invention is mounted. And the joining strength between the cylinder head 3 and the cylinder head 3 (the load required to remove the valve seat from the cylinder head). As a comparative example, the valve seat and the cylinder of the cylinder head equipped with the valve seat obtained by the same method as the embodiment of the present invention except that the concave portion 4 is not provided on the side surface 3b of the valve seat mounting portion of the cylinder head 3 Shows the bonding strength with the head. From FIG. 3, it is clear that the embodiment in which the mechanical engagement and the metal connection are performed has higher bonding strength than the comparative example in which only the metal connection is performed, and a recess is formed in the side surface 3 b of the cylinder head 3. It can be seen that the fitting strength is improved by fitting the valve seat 1 into the recess 4. The deeper the recess 4 is, the larger the fitting allowance between the valve seat 1 and the cylinder head 3 is, and the more reliable the joining is. When the valve seat material is press-fitted into the cylinder head, it is not easy to make the recess deeper because only the thermal expansion and elastic deformation allow the recess to be formed. Since the semi-molten material flows in, the fitting margin can be easily increased.

[0010]

According to the present invention, the valve seat material is pressed against the seat surface of the valve seat mounting portion of the cylinder head,
By energizing between the valve seat material and the valve seat mounting portion of the cylinder head, at least the metal of the projection portion is semi-melted and flows, and the metal between the valve seat material and the seating surface of the seat mounting portion of the cylinder head. Since the gap and the gap between the side surface including the recess of the cylinder head are filled, the valve seat is mechanically engaged with the recess of the cylinder head and is metal-bonded. Therefore, the joining strength between the valve seat and the cylinder head and the joining reliability are improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method of fixing a valve seat to a cylinder head according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a cylinder head to which a valve seat obtained according to an embodiment of the present invention is fixed.

FIG. 3 is a diagram comparing the load obtained by removing the valve seat fixed to the cylinder head from the cylinder head with that obtained by the example of the present invention and that obtained by the comparative example.

FIG. 4 is a view showing a conventional method of fixing a cylinder head of a valve seat.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve seat 1A Valve seat material 2 Projection 3 Cylinder head 3a Seat surface 3b Side surface 4 Recess

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-105309 (JP, A) JP-A-8-74657 (JP, A) JP-A-7-103070 (JP, A) JP-A-7-107 189628 (JP, A) JP-A-7-34965 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02F 1/24 B23K 11/14 F01L 3/22

Claims (1)

(57) [Claims] An axially projecting projection is formed on a valve seat material, and a concave portion is formed on a side of a valve seat mounting portion having a seating surface and a side surface, and is recessed outward in a radial direction on a cylinder head. The process and the projection of the valve seat material are applied to the seat surface of the valve seat mounting part, and while the valve seat material is pressed against the seat surface of the valve seat mounting part, a current is applied between the valve seat material and the valve seat mounting part, At least the metal of the projection part of the valve seat material that has been semi-melted due to heat generation fills the gap between the valve seat material and the seat surface of the valve seat mounting part and the side surface including the concave part, and the valve seat material adheres to the valve seat mounting part Mechanically engaging and metal-bonding the valve seat to the cylinder head. Method of fixing the valve seat of the cylinder head that.