JPH10121921A - Valve seat for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress to harden a joining part of a valve seat and a cylinder head when the valve seat is welded with the cylinder head by forming the valve set in such as constitution that the half fusion and joining are carried out by welding with the cylinder head, and forming the joining part of the valve seat and the cylinder head of a material having low seizing performance. SOLUTION: A valve seat 1 consists of a main body part 1a made of an Fe sintering material (for example, an Fe-Mo-Co-Ni-C sintering material), and a joining part 1b made of a material having a low sintering performance (for example, an S10C material), and a part thereof is joined with an aluminum alloy made cylinder head 2 by the joining part 1b through a half fusing condition. Since the main body part 1a is formed of a material (a material including Mo, Ni) having abrasion resistance and the joining part 1b is formed of a material provided with a characteristic having a low sintering performance, it is suppressed to be quenched on welding, and generation of cracking is suppressed on welding and on operation of an engine so as to improve durability and reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve seat mounted on intake and exhaust ports of a cylinder head of an internal combustion engine.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 7-34965 discloses a method of joining a valve seat and a cylinder head with reference to FIG.
As shown in FIG. 5, a ring-shaped valve seat material 11A made of an iron-based sintered alloy is placed on the cylinder head 12 in a state of contacting the tapered surface 12b of the cylinder head 12, and the valve seat material 11A is energized while being pressed. By doing
There is a description that the valve seat member 11A and the cylinder head 12 are joined by resistance welding. Further, since the valve seat is required to have wear resistance, the valve seat material may include an element such as Mo or Ni that improves the wear resistance.

[0003]

Since the vicinity of the contact portion between the valve seat material 11A and the cylinder head 12 is rapidly heated and cooled during resistance welding, Mo, Ni, or other material having a property to promote hardenability is used. Valve seat material 11A
, The joint between the valve seat material 11A and the cylinder head 12 is quenched, becomes extremely hard and easily cracks, and the thermal fatigue characteristics of that portion deteriorate. Further, machining after welding is difficult, and the life of the cutting tool is also reduced. An object of the present invention is to provide a valve seat for an internal combustion engine that can prevent a joint portion with a cylinder head from being hardened during welding to the cylinder head.

[0004]

Means for Solving the Problems A valve seat according to the present invention for achieving the above object is as follows. What is claimed is: 1. A valve seat for an internal combustion engine, which is semi-melted and joined to a cylinder head by welding, wherein a joint with the cylinder head is made of a material having low hardenability.

In the valve seat of the internal combustion engine of the present invention, since the joint with the cylinder head is made of a material having low hardenability, the joint with the cylinder head of the valve seat is not hardened at the time of welding, and the hardness increases. Can be suppressed. As a result, generation of cracks is suppressed, thermal fatigue characteristics are improved, and machinability after welding is also improved.

[0006]

FIG. 1 shows a cross section of a cylinder head to which a valve seat of an internal combustion engine according to an embodiment of the present invention is joined.
FIG. 2 shows a method of joining a valve seat of an internal combustion engine to a cylinder head according to an embodiment of the present invention. Hereinafter, a valve seat 1 of an internal combustion engine according to an embodiment of the present invention will be described with reference to FIG. The valve seat 1 is made of a Fe-based sintered material (for example, Fe
-Mo-Co-Ni-C sintered material) and a joining portion 1b made of a material having low hardenability (for example, S10C material) formed in a layer on the cylinder head side of the body portion 1a. Become. The valve seat 1 is joined to the aluminum alloy cylinder head 2 at the joint 1b through a state in which a part is partially melted by resistance welding. The material of the valve seat 1 differs between the main body 1a and the joint 1b of the cylinder head. The main body 1a is made of a wear-resistant material (a material containing Mo and Ni) because it is repeatedly hit by a valve (an intake valve or an exhaust valve). The joint portion 1b of the valve seat 1 with the cylinder head is easily quenched by rapid heating and rapid cooling during welding, and therefore has a material having low hardenability, for example, S10C or less steel, SS500 or less steel, Cu-Ni material, Cu-Cr material, Cu-Mo material, C
It is formed from a u-Si material, a Cu-Co material, or the like.

Next, referring to FIG. 2, the valve seat 1 will be described.
A method of fixing the cylinder head to the cylinder head 2 will be described. First, the valve seat material 10 is made of S10C material, which includes a projection projecting in the axial direction and has a low hardenability at a joint portion 10b with the cylinder head, and a main body portion 1 as another portion.
Oa is formed of a sintered material of Fe-Mo-Co-Ni-C.
The cylinder head 2 having a valve seat mounting portion having a seat seating surface 2a and a side surface 2b having a tapered surface is formed by casting an aluminum alloy material. The side surface 2b may be formed with a concave portion 2c that is concave outward in the radial direction. Valve seat material 1
The formation of 0 and the formation of the valve mounting portion may be performed in any order. Next, the valve seat material 10 is inserted from the combustion chamber 3 side of the cylinder head 2, and the projection 10b of the valve seat material 10 is applied to the seat seating surface 2a, and the valve seat material 10 is placed on the seat seating surface 2a. Since the valve seat material 10 has the projection 10b, a gap is formed between the valve seat material 10 and the seat seat surface 2a except for the tip of the projection 10b. Further, since the side surface 2b of the cylinder head 2 is a tapered surface, a gap is formed between the valve seat material 10 and the side surface 2b (FIG. 2A).

Next, a current is applied between the valve seat material 10 and the seat mounting portion 2a while pressing the valve seat material 10 against the seat seating surface 2a. Due to the energization with pressurization, the valve seat material 10 flows when at least the metal of the projection 10b is semi-molten (FIG. 2).
(B)), filling the gap between the valve seat material 10 and the seat seating surface 2a and the gap between the valve seat material 10 and the side surface 2b (FIG. 2 (c)). It flows into the interior 2c to fill the recess 2c and solidifies to form a joint 1b with the cylinder head 2. Since the joining portion 1b is formed by semi-melting, flowing and solidifying the metal in the portion of the projection 10b,
It is made of S10C material.

Although the cylinder head 2 is formed of an aluminum alloy having a melting point of about 600 ° C., the heat capacity is large, and the aluminum alloy has a high thermal conductivity, so that the temperature hardly rises. However, only the area near the contact surface with the projection 10b is melted by a few μm. Therefore, the cylinder head 2 is metal-bonded to the projection 2 which is in a semi-molten state without being greatly deformed even when receiving a pressing force from the projection 10b. After welding, the valve seat 1 is machined into a desired shape and finished or deburred, and the valve seat 1 adhered to the valve seat mounting portion of the cylinder head 2 is obtained.

The shape and size of the projection 10b are determined so as to form the joint 1b after welding. Then, it is a portion which is brought into semi-melting by heating by resistance heating in contact with the cylinder head 2 during welding, and is formed of a conventional wear-resistant material (a material containing Mo and Ni). In the embodiment of the present invention, it is made of S10C material having low hardenability because it is hardened by rapid heating / quenching accompanying welding. Since the projection 10b is made of a material having low hardenability, quenching of the projection 10b during welding is suppressed, and an increase in the hardness of the joint 1b of the obtained valve seat 1 with the cylinder head 2 is suppressed. Have been.

Further, since the projection 10b of the valve seat material 10 is semi-melted to join the valve seat and the cylinder head, the joint strength is higher and the heat conduction is better than the method of press-fitting the valve seat into the cylinder head. As a result, the cooling performance around the combustion chamber can be improved, and the performance (output, torque, etc.) of the engine can be improved, and the heat resistance around the combustion chamber can be improved.

Next, the operation and effect of the embodiment of the present invention will be described. FIG. 3 shows a valve seat 1 of the embodiment of the present invention welded to a cylinder head 2 (the main body 1a is made of Fe-M
The hardness distribution of a cylinder head formed of an o-Co-Ni-C sintered material and a joint 1b with the cylinder head formed of an S10C material) is shown. And for comparison, FIG.
The hardness distribution between the valve head and the cylinder head in which the main body 1a and the joint 1b between the cylinder head and the cylinder head are made of the same material of Fe-Mo-Co-Ni-C sintered material is shown. As shown in FIG. 3, the valve seat 1 of the embodiment of the present invention
Since the hardness of the joint 1b with the cylinder head 2 is not significantly increased as much as the hardness of the joint between the valve seat and the cylinder head shown in FIG. 4, quenching during welding is suppressed, Cracks are less likely to occur. Therefore, cracking and peeling of the joint part with the cylinder head, which occurred when the conventional valve seat made of a material that only considers improving wear resistance and does not consider quenching during welding, was welded. Is solved by forming the joint 1b of the valve seat 1 with the cylinder head from a material having low hardenability.

When the concave portion 2c is formed on the side surface 2b, the solidified convex portion of the valve seat metal flowing into the concave portion 2c and the concave portion 2c are engaged in the axial direction of the valve seat. It is significantly improved, and furthermore, the quenching of the convex portion is suppressed, so that the increase in hardness is suppressed, and even when repeatedly hit with a valve, the occurrence of cracks and defects are suppressed,
Sufficient mounting strength is maintained. In addition, wear-resistant materials (Fe
-Mo-Co-Ni-C sintered material) is expensive, but the valve seat 1 of the embodiment of the present invention is partially made of inexpensive S10C material, so that the material cost is reduced.

[0014]

According to the present invention, since the joint between the valve seat and the cylinder head joined to the cylinder head by welding is made of a material having low hardenability, quenching during welding is suppressed. Thus, cracks are less likely to occur during welding and during operation of the engine, and durability and reliability are improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a valve seat welded to a cylinder head according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a method for joining a valve seat to a cylinder head according to an embodiment of the present invention.

FIG. 3 is a diagram showing hardness of a valve seat and a cylinder head according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating hardness of a valve seat and a cylinder head according to a comparative example.

FIG. 5 is a view showing a conventional method of joining a valve seat to a cylinder head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve seat 1b Joint 2 Cylinder head

Claims (1)

[Claims] 1. A valve seat for an internal combustion engine which is semi-melted and joined to a cylinder head by welding, wherein a joint with the cylinder head is made of a material having low hardenability. .