JP2001121239A - Forging method of cone part in engine valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce forging energy by plastically deforming locally only the part requiring the hardness in the bulging part of a cone part. SOLUTION: The bulging part 8 is formed at the cone part 6a as the portion of a valve face part in an engine valve 6 before forging, and the portion corresponding to the valve face part 7b in this bulging part 8 is locally pressed and plastically deformed in the state of holding the cone part 6a in a die hole 9a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forging method in which a portion requiring hardness can be plastically deformed with a small forging energy when work hardening a valve face portion of an engine valve.

[0002]

2. Description of the Related Art A valve face of an intake / exhaust valve used in an internal combustion engine is an important part for maintaining the airtightness of a cylinder, and is required to have high wear resistance.

In order to satisfy this requirement, an engine valve is formed of a metal material having a face-centered cubic lattice structure, for example, a Ni-based heat-resistant alloy of Inconel (trade name), and a work hardening treatment is performed on a valve face portion. It has been practiced to increase hardness and abrasion resistance.

FIGS. 5 and 6 show a conventional forging method for work-hardening the valve face of the engine valve. In FIG. 5, (1) shows an engine valve intermediate product before forging made of a Ni-base heat-resistant alloy (hereinafter abbreviated as a valve intermediate product). A protrusion (2) is formed.

[0005] After inserting the valve intermediate product (1) vertically into the die hole (3a) of the die (3) in the forging device as shown in the figure, the punch (4) is turned into the die hole (3a). To lower by a predetermined stroke. The mold hole (3a) is substantially complementary to the umbrella portion of the engine valve to be molded, but only the inner diameter at the upper end is enlarged so as not to restrict the flow of meat during forging.

As shown in FIG. 6, when the punch (4) is lowered, the bulging portion (2) of the valve intermediate product (1) is plastically deformed, so that a prototype engine valve (5) is obtained. Can be The outer diameter portion of the umbrella portion (5a) in the original product (5) is cut by machining as indicated by an imaginary line, and is finished to a predetermined outer diameter. A valve is obtained.

[0007]

In the above-described conventional forging method, the entire fork portion including the bulging portion (2) is pressed to be plastically deformed, and free forging is performed without restricting the flow of meat. The umbrella portion (5a) expands in diameter, and the processing cost when performing the finishing process on the outer diameter portion becomes large.

In addition, although the outer peripheral end of the umbrella (5a) does not need to be work-hardened, the part is also plastically deformed, so that a large forging energy is required, and a large engine valve for a ship or the like is required. Then, it is necessary to install a forging device having a large compression capacity.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is intended to prevent the outside diameter of an umbrella portion from expanding by locally plastically deforming only a portion of a bulging portion which requires work hardening. It is an object of the present invention to provide a method for forging an umbrella portion of an engine valve, which suppresses a processing allowance at the time of finishing while suppressing the forging and enables plastic deformation with a small forging energy.

[0010]

According to the present invention, the above-mentioned problem is solved as follows. (1) A bulge portion is formed in the umbrella portion of the portion that will be the valve face portion of the engine valve before forging, and the portion of the bulge portion corresponding to the valve face portion is accommodated in the mold hole. In this state, plastic deformation is performed by pressing locally.

(2) In the above item (1), the inner diameter of the mold hole is made substantially equal to the maximum outer diameter of the head portion of the engine valve before forging.

(3) In the above item (1) or (2), a slight gap is formed between the outer peripheral surface of the punch for pressing the bulging portion and the mold hole, and the excess when pressing the bulging portion is formed. Meat flows into the gap.

[0013]

1 to 4 show the method of the present invention in the order of steps. FIG. 1 shows an engine valve intermediate product before forging applied to the present invention (hereinafter abbreviated as a valve intermediate product).
It shows the umbrella part (6a) side of (6), and the valve intermediate product (6)
For example, a precipitation hardening type Ni-base heat resistant alloy (NCF80A, N
CF751).

The maximum outer diameter of the lower end of the umbrella portion (6a) in the valve intermediate product (6) is indicated by an imaginary line, and the forged engine valve is
(7) The umbrella part (7a) is almost equal in diameter to the maximum outer diameter,
A bulging portion (8) similar to the conventional one is formed in a portion corresponding to the tapered valve face (7b).

An umbrella portion (6a) of the valve intermediate product (6) having the above shape.
After being heated to about 600 ° C., it is vertically inserted into a bottomed mold hole (9a) of a die (9) in a forging device schematically shown in FIG. The inside diameter of the mold hole (9a) is the umbrella part (6a) of the valve intermediate product (6).
The outer diameter of the umbrella is substantially equal to the outer diameter of the umbrella, so that the umbrella (6a) can be held and held without play.

[0016] The punch (10) of the forging device is a valve intermediate product.
It has a cylindrical shape that allows the shaft part of (6) to be inserted with a margin, and its lower end has an outer diameter slightly smaller than the inner diameter of the mold hole (9a) and a lower inner peripheral surface having a C-shaped cross section. Pressing surface (10a)
An annular compression section (10b) is provided in series.

The angle of inclination of the pressing surface (10a) is substantially the same as the angle of the valve face (7b) of the forged engine valve (7), and the length thereof is in the radial direction of the valve face (7b). It is almost equal to the length.

As shown in FIG. 3, when the punch (10) is lowered by a predetermined stroke and the compression part (10b) is pushed into the mold hole (9a), the bulging part in the valve intermediate product (6) is formed. (8)
The portion corresponding to the valve face (7b) is locally pressed by the pressing surface (10a) and is plastically deformed.

At this time, the excess meat (11) (11) of the bulging portion (8)
In the compression portion (10b), the fluid flows upward along the outer peripheral surface, and the excess meat (11) on the outer peripheral portion flows into the gap between the mold hole (9a) and the compression portion (10b). As a result, the valve face (7'b) of the forged engine valve (7 ') is locally work-hardened.

Then, as shown in FIG. 4, the engine valve (7 ') removed from the mold hole (9a) is subjected to finish processing and, at the same time, the excess meat (11) is removed to manufacture the engine valve (7). An engine valve (12) having a predetermined shape is obtained. As in the embodiment described above, the umbrella portion (6a) of the valve intermediate product (6) is attached to the die (9).
After holding and holding without looseness in the mold hole (9a), punch
When the bulging portion (8) is pressed and plastically deformed by the compressing portion (10b) of (10), the outer diameter of the umbrella portion does not increase and the finishing process is performed on the outer diameter portion as in the conventional case. The processing allowance at the time of application becomes extremely small.

In addition, the bulging portion (8) is locally plastically deformed only at a portion where hardness is required, and the excess meat (11) at that time is formed along the inner and outer peripheral surfaces of the compression portion (10b). Since it is made to escape upward, the forging energy can be small, and an inexpensive forging device having a small compression capacity can be used.

Furthermore, a large deformation strain can be given with a small forging energy, so that the valve face portion (7'b)
The hardness is greatly increased.

The present invention is not limited to the above embodiment. In the above embodiment, the valve intermediate product (6) is forged with the umbrella portion (6a) side facing downward.
The umbrella (6a) is placed upward on a die having the same shape as the above-mentioned punch (10), and the umbrella (6a) is forged from above with a punch having the same shape as the above-mentioned die (9). You may make it.

The shape and size of the bulging portion (8) can be appropriately determined depending on the engine valve to be obtained by forging.

[0025]

According to the first aspect of the present invention, the bulging portion of the umbrella portion is plastically deformed by pressing only the portion corresponding to the valve face portion requiring hardness, so that forging energy is small. And a small and inexpensive forging device can be used. Further, since the bulging portion is plastically deformed in the mold hole, it is possible to prevent the outer diameter of the umbrella portion from expanding more than necessary.

According to the second aspect of the present invention, it is possible to almost completely prevent the outer diameter of the umbrella portion from expanding, so that the machining allowance at the time of finishing is extremely reduced.

According to the third aspect of the present invention, the surplus meat when the bulging portion is pressed is dispersed along the outer peripheral surface of the pressing punch without being concentrated at one location and flowing. , The forging energy and the load acting on the punch are reduced.

[Brief description of the drawings]

FIG. 1 is a front view of an umbrella portion side of an intermediate engine valve product before forging used in one embodiment of the present invention.

FIG. 2 is a central longitudinal sectional front view showing a state in which a valve intermediate product is accommodated in a die hole of a die of a forging device in order to plastically deform a bulging portion.

FIG. 3 is a longitudinal sectional front view showing a state in which a bulging portion is plastically deformed by lowering a punch.

FIG. 4 is a front view of the engine valve after forging is finished to remove excess meat.

FIG. 5 is a front view of a central longitudinal section in a state where a valve intermediate product in a conventional forging method is inserted into a die of a forging device.

FIG. 6 is a vertical sectional front view showing a state in which the swelling portion is plastically deformed by lowering the punch.

[Explanation of symbols]

 (6) Valve intermediate product (6a) Head (7) (7 ') Forged engine valve (7a) Head (7b) (7'b) Valve face (8) Swell (9) Die ( 9a) Mold hole (10) Punch (10a) Pressing surface (10b) Compression part (11) Excess meat

Claims (3)

[Claims] A bulge portion is formed in an umbrella portion of a portion to be a valve face portion of an engine valve before forging, and a portion of the bulge portion corresponding to the valve face portion is formed by inserting the umbrella portion into a mold hole. A method of forging an umbrella portion of an engine valve, wherein the umbrella portion is plastically deformed by being locally pressed while being housed in the engine valve. 2. The method according to claim 1, wherein the inner diameter of the mold hole is substantially equal to the maximum outer diameter of the head portion of the engine valve before forging. 3. A slight gap is formed between the outer peripheral surface of the punch for pressing the bulging portion and the mold hole, so that excess meat when pressing the bulging portion flows into the gap. The method for forging an umbrella part in an engine valve according to claim 1 or 2, characterized in that: