JPH07189628A - Joined type valve seat - Google Patents

Abstract

PURPOSE:To always provide a high sealing function without producing cracks. CONSTITUTION:A joined type valve seat 1 is made of a Cu alloy or am autstenitic iron alloy and this is joined with a cylinder head 10 by resistance welding. Since as a material of the joined type valve seat 1 the Cu alloy having large expansiveness (expansion by breaking) is selected, the cylinder head 10 cast by an alluminum alloy is expanded by heat, and thus even when large expansion is generated in a circumferential direction in the joined type valve seat 1, no crack of a radial direction occurs therein. Also, since as a material of the joined type valve seat the austenitic iron alloy whose thermal expansion coefficient is close to that of the cylinder head 10 is selected, no excessive thermal stress is generated in a joined boundary between the joined type valve seat 1 and the cylinder head 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint type valve seat joined to a cylinder head of an internal combustion engine by resistance welding.

[0002]

2. Description of the Related Art In the field of internal combustion engines,
The number of valves is increasing as part of higher speeds, and multiple intake and exhaust ports are placed close to each cylinder, so the distance between each port is becoming shorter. When press-fitting is conventionally performed on the periphery of the intake / exhaust port, there arises a problem such as cracking due to insufficient distance between the ports of the cylinder head.

Therefore, attempts have been made to join the valve seat to the periphery of the intake / exhaust ports of the cylinder head by resistance welding or the like.

[0004]

However, when the conventional valve seat made of an iron-based sintered material is joined, or when the engine assembled by joining the valve seats is operated, the valve seat is cracked in the radial direction. This may occur and the sealing function of the valve seat may deteriorate. This radial cracking of the valve seat means that internal stress due to heating and cooling is generated in the valve seat during joining, and the coefficient of thermal expansion of the aluminum alloy cast cylinder head, which is the object to be joined, is much higher than that of the valve seat. It is considered that tensile stress is generated in the circumferential direction of the valve seat during engine operation due to its large size.

Therefore, in order to prevent the occurrence of such radial cracking of the valve seat, various structural and joining techniques have been devised, but all of them require high-precision control and are poor in productivity. , Difficult to achieve.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a joining type valve seat which can always achieve a high sealing function without cracking.

[0007]

In order to achieve the above object, the present invention comprises a joint type valve seat made of a Cu-based alloy or an austenite-based iron-based alloy, which is joined to a cylinder head of an internal combustion engine by resistance welding. It is characterized by

[0008]

According to the present invention, since a Cu-based alloy having a large toughness (breaking elongation) is selected as the material of the joining type valve seat, the joining type valve seat is circularly expanded due to the thermal expansion of the aluminum alloy cast cylinder head. Even if a large circumferential elongation occurs, the joint type valve seat does not crack in the radial direction, and the joint type valve seat stably exhibits a high sealing function. This Cu-based alloy is a material that has both high wear resistance and bondability, and as a method for manufacturing a bonded valve seat using this material, there are casting method, powder sintering method, and cutting from rolled material. There are three outings.

Further, according to the present invention, since the austenite base iron-based alloy having a thermal expansion coefficient close to that of the material of the cylinder head (aluminum alloy casting) is selected as the material of the joint type valve seat, the joint type valve seat Excessive thermal stress does not occur at the joint interface with the cylinder head, so abnormal deformation or cracking does not occur in the joint type valve seat, and a stable and high sealability is secured in the joint type valve seat. In addition, the austenite base iron-based alloy is F
It is obtained by adding Mn and Ni to the e-based base material in specified ranges.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 and 2 are perspective cutaway views of an intake port portion of a cylinder head showing a state before and after joining a valve seat.

In FIGS. 1 and 2, reference numeral 10 is a cylinder head made of a lightweight aluminum alloy casting, and a ring-shaped tapered surface 11a is formed on the periphery of an intake port 11 by machining. .

On the other hand, 1 is a ring-shaped joined valve seat according to the present invention (hereinafter simply referred to as a valve seat), and the valve seat 1 has a large toughness (elongation at break),
Cu-based alloys that combine high wear resistance and bondability (for example,
Cu-Ni-Si alloy, Cu-Be alloy, Cu-Cr alloy), or an austenite base iron-based alloy (for example, JIS-SUH31 equivalent material) whose expansion coefficient is close to that of the material of the cylinder head 10 (aluminum alloy casting): S
US304, 301S, 316, INCONEL). There are three methods of manufacturing the valve seat 1 using a Cu-based alloy: a casting method, a powder sintering method, and shaving from a rolled material. Further, the austenite base iron-based alloy is obtained by adding Mn and Ni to the Fe-based base material in the specified range.

The physical and mechanical properties of the Cu-based alloy and austenite-based iron-based alloy selected as the material for the valve seat 1 are shown in the table below.

[0015]

[Table 1] In addition, () in the above table shows an estimated value.

Next, the joining process of the valve seat 1 according to the present invention to the cylinder head 10 by resistance welding will be described with reference to FIG.
A description will be given based on (a) to (d).

First, as shown in FIG. 3 (a), the valve seat 1 is set in a state in which the protrusion 1a thereof abuts on the tapered surface 11a of the peripheral edge of the intake port 11 of the cylinder head 10, and the electrode 20 makes the tapered surface 11a. The pressure is applied between and, and then the power is supplied.

When the joint surface between the valve seat 1 and the cylinder head 10 and its vicinity (welded portion) are heated to the melting temperature or a temperature close to the melting temperature, the energization is cut off. Then, the cylinder head 10 made of an aluminum alloy casting having a hardness lower than that of the valve seat 1 is plastically deformed as shown in FIG. 3B, and the valve seat 1 is joined in a state of being embedded in the cylinder head 10.

Thereafter, the joint portion is cooled, and the joint portion is machined along a cut surface C shown by a chain line in FIG. 3 (c). As a result, as shown in FIG. The intake port 11 of the cylinder head 10 is finished into a shape
It is joined and integrated with the peripheral edge (see FIG. 2).

Thus, according to the present embodiment, since the Cu-base alloy having a large toughness (elongation at break) is selected as the material of the valve seat 1, the cylinder head 10 made of the aluminum alloy casting is thermally expanded, so that the valve is formed. Even if the seat 1 is greatly stretched in the circumferential direction, the valve seat 1 is not cracked in the radial direction, and the valve seat 1 stably exhibits a high sealing function.

Further, according to the present embodiment, as the material of the valve seat 1, an austenitic base iron-based alloy having a thermal expansion coefficient close to that of the material of the cylinder head 10 (aluminum alloy casting) is selected. Excessive thermal stress does not occur at the joint interface with the cylinder head 10, and therefore abnormal deformation or cracking does not occur in the valve seat 1, and the valve seat 1 has stable and high sealing performance.

Although only the joining of the valve seat to the intake port side has been described above, it goes without saying that the joining to the exhaust port side can be similarly performed.

[0023]

As is apparent from the above description, according to the present invention, a joint type valve seat is made of a Cu-based alloy or an austenite-based iron-based alloy and is joined to a cylinder head of an internal combustion engine by resistance welding. As a result, the junction-type valve seat has an effect of always achieving a high sealing function without cracking.

[Brief description of drawings]

FIG. 1 is a cutaway perspective view of an intake port portion of a cylinder head showing a state before joining a valve seat.

FIG. 2 is a cutaway perspective view of an intake port portion of a cylinder head showing a state after joining a valve seat.

FIG. 3 is an explanatory diagram showing a joining process by resistance welding of a valve seat to a cylinder head.

[Explanation of reference numerals] 1 junction type valve seat 10 cylinder head 11 intake port 20 electrode

Claims (1)

[Claims] 1. A bonded valve seat, which is made of a Cu-based alloy or an austenite-based iron-based alloy and is bonded to a cylinder head of an internal combustion engine by resistance welding.