JP3463178B2 - Engine valve cotter groove forming method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an engine valve by hot squeeze forging, and more particularly to a method for forming a cotter groove at the tip of a stem.

[0002]

2. Description of the Related Art Generally, an engine valve is molded by hot squeeze forging through the steps shown in FIG.

FIG. 3A shows a material obtained by cutting a steel material into a cylindrical shape.
(Slag) (101) is shown, and this material (101) is heated to a required temperature and loaded into the lower mold (102) of the first step shown in FIG. 3 (B).

The lower mold (102) of the first step is an intermediate molded product.
The large-diameter head section (104) and the small-diameter stem (10)
Mold holes corresponding to the shapes of 5) are formed, and the heated material (101) is compressed by a punch (upper mold) (106) and forged to be processed into an intermediate molded product (103).

Next, the intermediate molded product (103) is loaded into the lower mold (107) of the second step shown in FIG. 3 (C).

In the lower die (107) of the second step, a die hole corresponding to the shape of the valve head (109) and the stem (105) of the engine valve (108) to be finally formed is formed. Yes, the head part (104) of the intermediate molded product (103) is punched (upper mold) (110)
And is compressed to form an umbrella-shaped valve head (109) to obtain a desired engine valve (108).

As shown in FIG. 4, the engine valve (111)
In some of them, a reduced diameter portion (114) having a diameter smaller than the shaft diameter of the main body of the stem (113) is provided at the tip of the stem (113).

At the reduced diameter portion (114), a cotter groove (115) with which a pair of cotters (not shown) engages when assembled in the engine.
Is engraved.

[0009]

A reduced diameter portion (114) is provided at the tip of the stem (113) in the engine valve (111) shown in FIG.
In order to form the cotter groove (115), conventionally, after forming the umbrella-shaped valve head (112) and the stem (113) by the process of FIG. 3 (C), they are machined, for example, ground by a centerless grinder. The method of forming is adopted.

Machining is also used to form a cotter groove in an ordinary engine valve having no reduced diameter portion (114). Therefore, an extra process is required in addition to the normal shaft grinding process, resulting in a problem that the time required for machining is long, the productivity is lowered, and the production cost is high.

Also, the grinding wheel for grinding has a short life,
There is also a problem that the replacement frequency is high. The present invention has been made to solve this inconvenience, and an object of the present invention is to provide a method for forming a cotter groove for an engine valve, in which the cotter groove is formed simultaneously by a hot squeeze forging step. And

[0012]

In order to achieve the above object, the present invention provides a valve head formation in a molding method in which a stem has a reduced diameter portion at its tip and a cotter groove is formed in the reduced diameter portion. A mold hole for forming a stem, a mold hole for forming a stem, a mold hole for forming a stem tip portion having a diameter smaller than that of the stem for forming a stem, and a mold hole having an inner diameter corresponding to the root diameter of the cotter groove and capable of expanding and contracting. After loading the raw material heated to a predetermined temperature on the upper part of the lower die that is connected in sequence from the top, press the material with a punch until it projects a required length from the lowest die hole, and then press the lowest die. It is characterized in that the end portion of the small diameter shaft projecting from the hole is forced upward by a lower punch positioned below the lower die to expand the diameter (claim 1).

Further, the present invention provides a molding method in which a cotter groove is formed at a tip portion of a stem having an equal diameter as a whole,
A mold hole for forming a valve head, a mold hole for forming a stem,
A material heated to a predetermined temperature is loaded into a lower mold in which a valley diameter of a cotter groove and an expandable / contractible mold hole corresponding to the inner diameter are sequentially arranged from the upper side, and then the material is predetermined from the lowest mold hole. It is characterized by strongly pressing with a punch until it projects to the length, and by expanding the diameter of the end of the small diameter shaft protruding from the lowest die hole upward with a lower punch located below the lower die. Claim 2).

[0014]

[Function] When the material loaded in the lower die is strongly pressed by the punch, the lower end of the stem has a reduced diameter portion formed by the die hole for forming the stem tip portion and a small diameter shaft formed by the die hole corresponding to the root diameter of the cotter groove. Is squeezed and formed, and the cotter groove is formed by pressing the lower end of the small diameter shaft upward with the lower punch.
(Claim 1).

When the lower punch strongly presses the lower end portion of the small diameter shaft formed by the die hole corresponding to the root diameter of the cotter groove below the die hole for forming the stem upward by the lower punch, the stem having the same diameter as a whole is formed. A cotter groove is formed at the lower end (claim 2).

When the mold hole for forming the cotter groove is formed by a pair of left and right movable dies that are relatively movable, the molded product after the cotter groove is formed can be easily extracted on the upper surface of the lower mold.
(Claim 3).

[0017]

1A and 1B show a first embodiment of the present invention.
(Embodiment of the invention described in claim 1) is shown, showing an example applied to an engine valve having a reduced diameter portion at the shaft end portion of the stem.

FIG. 1 (A) is based on the above-mentioned conventional technique.
The 1st process of forming an intermediate molding from a raw material is shown.

First, the hot squeeze forging device will be described. The lower die is an upper die (11), an upper die insert (12) closely attached to the lower die, and an upper die insert.
It is composed of a pair of left and right movable dies (13a) and (13b) for forming cotter grooves, which are provided in close contact with the lower surface of (12). The opposing end surfaces of the movable dies (13a) and (13b) are convex curved surfaces having a substantially semicircular cross section.

In the upper die (11), the shape of the large-diameter head portion (17) in the intermediate molded product and the complementary shape are formed in accordance with the lower die (102) of the first step in the conventional means of FIG. A mold hole (14) for forming a head portion and a mold hole (15) for forming a stem forming a shaft main body of the stem (18) are provided.

The upper die insert (12) has a die hole (16) for forming a reduced diameter portion having a diameter smaller than that of the die hole (15) for forming the stem.
Is provided.

The upper edge corner portion (20) facing the die cavity (15) of the upper die (11) in the die cavity (16) for forming the reduced diameter portion is chamfered into a curved surface, and the reduced diameter portion ( The proximal end of 19) and the stem (8) are smoothly continuous.

Movable dies (13a) (13b) for forming cotter grooves
Is closely attached to the lower surface of the upper die insert (12), and is provided so that it can be opened and closed relatively to the center axis of each mold cavity (14), (15), (16), and in the closed position. A mold hole (13c) corresponding to the shape of the cotter groove of the engine valve is formed between the facing surfaces of the movable dies (13a) and (13b).

The movable dies (13a), (13b) are constructed such that the diameter of the mold cavity (13c) is opened to at least the outer diameter of the reduced diameter portion (19).

Next, a description will be given of the procedure for hot squeezing and forging an intermediate molded product of an engine valve by using the forging device having the above structure.

First, a pair of left and right movable dies (13a, 13b) are closed around the axis to form a die hole (13c) having an inner diameter corresponding to the root diameter of the cotter groove in advance.

As shown in FIG. 1 (A), a heated material (not shown) is loaded into the mold cavity (14) through the upper opening of the upper die (11) and press-forged with a punch (21) from above. Then,
The material flows downward while plastically deforming along the inner surfaces of the mold cavities (14) and (15), and the head (17) and stem
(18) and are formed.

When the pressure forging is further continued, the stem (18)
The tip end of the is flowed into the mold hole (16) of the upper die insert (12) and is squeezed out to form a reduced diameter portion (19).

Furthermore, the tip of the reduced diameter portion (19) is smaller than the reduced diameter portion (19) by passing through the die cavity (13c) formed by a pair of left and right movable dies (13a), (13b). The small-diameter shaft (22) is squeezed downward and protrudes.

The outer diameter of the small diameter shaft (22) has a size that matches the root diameter (minimum diameter) of the cotter groove of the engine valve to be manufactured.

Next, with the punch (21) being lowered, the small diameter shaft (22) protruding below the movable dies (13a), (13b).
As shown in FIG. 2 (B), the bottom end of each of the lower punches (23) is formed on the upper surface of the lower punch (23) and has a bottomed hole (23a) having the same diameter as the diameter of the reduced diameter portion (19).
And press upward to compress.

By this compression, the protruding portion of the small diameter shaft (22) is plastically deformed by the bottomed hole (23a) to form the expanded diameter portion (24) having the same diameter as the reduced diameter portion (19). Along with the small diameter shaft (2
The cotter groove (25) is formed by plastically deforming the base portion of 2) along the inner surface shape of the die hole (13c).

After forming the cotter groove (25) and the enlarged diameter portion (24), the pair of left and right movable dies (13a, 13b) are moved outward, and the formed intermediate molded product is It can be extracted from the top opening of the die (11). The above cotter groove
In the molding step of (25), when the molding temperature of the small diameter shaft (22) is insufficient, it may be reheated by an appropriate heating means.

Then, the intermediate molded product is sent to the lower mold of the second step to mold the head part (17) into an umbrella-shaped valve head, and after finishing each part, as shown in FIG. The engine valve is obtained.

FIGS. 2A and 2B show a second embodiment of the present invention.
(Embodiment of the invention described in claim 2), showing a procedure for forming a cotter groove in a normal engine valve in which the entire stem has an equal diameter.

First, in the intermediate product molding process of FIG.
A pair of movable dies (26a) (26b) similar to those described above, which are provided in close contact with the lower surface of the upper die (11), are intended to be manufactured at the lower end portion of the stem (27) by the die holes (26c). A small diameter shaft (28) having the same diameter as the root diameter of the cotter groove of the engine valve is formed by squeezing.

Next, in the step of FIG. 2B, the small diameter shaft
When (28) is strongly pressed upward by the lower punch (29) having the bottomed hole (29a) having the same diameter as the diameter of the stem (27), the small diameter shaft
(28) is plastically deformed by the bottomed hole (29a) and the stem
A cotter groove (30) is formed at the same time when the diameter is expanded to the same diameter as (27).

As described above, according to the molding method of the present invention, in the primary hot squeeze forging step of the engine valve, the reduced diameter portion (19) of the tip portion of the stem (18) and the cotter groove (25). (3
0) is formed at the same time.

Therefore, unlike the conventional case, the step of forming the reduced diameter portion and the cotter groove by machining after forming the basic shape of the engine valve by hot squeeze forging becomes unnecessary, and the number of working steps is reduced. The productivity is improved and the tool life is extended.

Further, since the amount of cutting by machining can be reduced at the stage of material, the amount of material used can be saved and the manufacturing cost can be reduced. Furthermore, the reduced diameter part (19)
Since the cotter grooves (25) and (30) portions are hardened by forging, the mechanical strength (particularly tensile strength) of the portions is significantly increased as compared with conventional machined products.

In the above embodiment, the reduced diameter portion (19) and the cotter grooves (25) and (30) are formed in the primary process, but the primary process is omitted and the secondary process is performed. Sometimes formed.

[0042]

According to the present invention, the following effects can be obtained. (a) Since the reduced diameter portion and the cotter groove at the tip of the stem are formed at the same time in the hot squeeze forging step without machining, the productivity is greatly improved.

(B) The time required for machining such as finishing process is shortened and the life of the cutting tool is extended.

(C) The mechanical strength of the reduced diameter portion and the cotter groove is increased, and the amount of material used can be saved.

[Brief description of drawings]

FIG. 1 shows a first embodiment of the present invention and a main part of a hot squeeze forging device for carrying out the same. (A) is a step of forming a reduced diameter portion and a small diameter shaft, and (B) is a cotter groove. It is a process of forming.

FIG. 2 shows a second embodiment of the present invention, in which (A) is a small diameter shaft forming step and (B) is a cotter groove forming step.

FIG. 3 is a schematic view showing a process of forming an engine valve by conventional hot squeeze forging, in which (A) is a raw material, (B) is a primary process, and (C) is a secondary process.

FIG. 4 is an external view showing an engine valve having a reduced diameter portion at a tip portion of a stem.

[Explanation of symbols]

(11) Upper die (12) Upper die insert (13a) (13b) Movable die (13c) Mold hole for forming cotter groove (14) Mold hole for forming valve head (15) Mold hole for stem formation (16) Mold hole for forming reduced diameter part (17) Valve head (18) Stem (19) Reduced part (20) Corner (21) Upper punch (22) Small diameter shaft (23) Lower punch (24) Expanded part (25) cotter groove (26a) (26b) Movable die (26c) Mold hole for forming cotter groove (27) Stem (28) Small shaft (29) Lower punch (30) cotter groove

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Claims (3)

(57) [Claims] 1. A molding method for forming a cotter groove in the reduced diameter portion, wherein the stem has a reduced diameter portion at its tip, and a mold hole for forming a valve head, a mold hole for forming a stem, and a stem formation. A stem for forming the stem tip, which has a smaller diameter than that of the mold cavity, and a mold cavity with an inner diameter corresponding to the root diameter of the cotter groove, which can be expanded and contracted in sequence from the top to the predetermined temperature. After loading the heated material, the material is strongly pressed with a punch until it protrudes from the lowermost mold hole by a required length, and the end of the small diameter shaft protruding from the lowermost mold hole is placed below the lower mold. A method for forming a cotter groove for an engine valve, which is characterized in that the lower punch positioned causes a strong upward pressure to expand the diameter. 2. A molding method for forming a cotter groove at the tip of a stem having the same diameter as a whole, which corresponds to a mold hole for forming a valve head, a mold hole for forming a stem, and a root diameter of the cotter groove. After loading a material heated to a predetermined temperature on the upper part of a lower mold in which a mold hole having an inner diameter that can be expanded and contracted is sequentially connected from above, the material is protruded from the lowest mold hole by a predetermined length. Cutter groove molding for engine valves, characterized in that the end of the small-diameter shaft that is pressed by the punch and protrudes from the lowest mold hole is pressed upward by the lower punch located below the lower mold to expand the diameter. Processing method. 3. The engine according to claim 1, wherein the mold hole forming the cotter groove is formed by a pair of left and right movable dies closely contacted with the lower surface of the lower mold so as to be relatively movable. Valve cotter groove molding method.