JPH0620570B2 - Piston forging method - Google Patents

Description

The present invention relates to a method for forging a piston used in an internal combustion engine.

(Prior Art) The piston of the internal combustion engine is as shown in FIG. 14 and FIG. 15, and the piston (50) is provided on the head (51), the skirt (52), and the outer periphery of the skirt at opposite positions. A piston pin mounting boss (53) protruding inward and a pin hole (54) provided in the boss are provided, and the upper portion of the pin hole (54) of the boss (53) is undercut for weight reduction. Thus, a concave portion (55) is formed in the radial direction.

When manufacturing the above pistons, it is easy to form the undercut recesses (55) described above when performing by forging, and it is also easy to form the pin mounting boss portion. Machining after processing and the like increase, and the piston receives a high pressure, which complicates the management of the casting cavity and other manufacturing processes.

Therefore, a piston is obtained by forging, and in the case of forging, a disc-shaped billet is extruded backward to obtain a piston material, and the material is machined and finished to obtain a final product.

(Problems to be solved by the invention) In the piston obtained by the above forging, the product yield is improved because the structure is densified and there are no problems such as cavities due to forging, but by the conventional backward extrusion molding In particular, it is difficult to form the undercut recess on the inner wall of the piston, and because this cannot be formed, the surplus part increases and the machined part increases, which is disadvantageous in terms of productivity. As a result of the large number of processed parts, the material yield decreases.

The present invention has been made to solve the above problems, the objective is to form the piston by forging, the undercut recess can be formed by forging,
An object of the present invention is to provide a piston forging method which improves the outer shape and dimensional accuracy, minimizes machining, improves production efficiency, improves material yield, and is advantageous in cost.

(Means for solving the problems) The means for solving the above problems is to hold the piston material molded in the shape of an inverted cup with a die, set it between the upper and lower punches, and set the material with the upper punch. The upper punch is restrained from above, the lower punch is fitted and supported from below the material, and the side punch is inserted from the side to form a recess for the piston pin boss on the outer circumference of the material. A divided structure consisting of a plurality of members that protrude in the radial direction inside, and when the side punch is used to form the recess for the piston pin boss, a back pressure is applied to the upper punch to form a boss portion with the lower punch head. That is, an undercut concave portion in the radial direction is simultaneously formed on the inner wall of the upper material.

(Operation of the above means) According to the above means, the piston material boss inner wall between the lower punch and the lower punch due to the back pressure load applied to the upper punch at the time of forming by the side punch intrusion of the piston pin boss into the outer circumference of the piston material. Undercut recesses can be molded at the same time.

(Embodiment) Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 to 3 show the steps of piston forging in the order of material, molding material, and molded product, and FIGS. 2 and 3 are sectional views with 90 ° angle changed.

Figure 1 shows a thick disk-shaped material (A) called a billet.
As the material, for example, an aluminum alloy JIS2018 material is used. Instead of this, a sintered metal or the like may be used. Material above (A)
The preform is molded into a molding material (B) as shown in Fig. 2. The molding material (B) has an inverted cup shape with a head (B ₁ ), an axially long skirt (B ₂ ), and an axially short material. A padded thick portion (B ₃ ) is provided at a position facing the skirt portion. This molding material (B) is molded by forging as shown in Fig. 3 to obtain a molded product (C).
(C ₁ ), the further molded skirt (C ₂ ), the thick part (B
Piston pin boss including a recess (C ₃₎ in the radial direction inwardly projecting molded in ₃₎ (C _4), near the lower portion of the head (C ₁₎ at the projecting portion above the boss portion (C ₄₎ Equipped with an undercut recess (C ₆ ) protruding radially outward of the wall of the recess (C ₃ ) of the boss (C ₄ ) (C ₅ )
Is thinned, and this portion is drilled to form a piston pin hole.

FIGS. 4 to 13 show a concrete embodiment of piston forging together with the operation of the apparatus, in which the apparatus (1) has an upper die (2).
, Lower intermediate die (3), lower lower die (4), and lower die (4) with base (16)
(2) is provided with a hole (2a) for closely fitting the molding material (B) of the piston preformed from the billet (A). The intermediate die (3) has a sliding hole (3a) that is concentric with the hole (2a).
A recessed portion (3b) that spreads toward the end is formed in the middle portion or lower portion of the lower die, and a large-diameter space portion (4a) is provided in the lower die (4) so as to vertically pass therethrough.

Above the upper die (2), an upper punch (5) slidably fitted in the hole (2a) is arranged, and the upper punch (5) is hung from the upper die (6). As shown in FIG. 5 and FIG. 6, the holder (17) is hung and fixed on the lower surface of the upper mold (6), and the holder (17) is fixed.
As shown in Fig. 6, there are rectangular guide slots that are long in the left-right direction.
(18) is formed, on the other hand, the punch guide (19) is fixed to the lower surface of the long hole (18) of the holder (17) so as to close the lower surface of the long hole (18),
A guide hole formed in the guide (19) at the upper part of the upper punch (5)
The punch (5) is equipped with a flange (5a) at the upper end of the punch (5) to prevent falling from the hole (19a), and the neck (5b) to have a hole ( 19a).

An inclined surface (5c) is formed on the upper end surface of the upper punch (5), a receiving block (20) for back pressure load is arranged on the upper punch (5), and a lower surface of the block (20) is provided. An opposite inclined surface (20c) is formed to contact the inclined surface (5c) of the upper punch upper surface, and the block (20) has a flat (bottom) surface rectangular shape as shown in FIG. Fitted slidably in the left-right direction in the figure, usually facing the center of the long hole (18) in the left-right direction, the upper punched surface (5c) and the lower tilted surface (20a) of the lower punch (5). ) Is in contact with. On one side (20b) of the block (20) that is vertically long, the pressure rod (2
The tip (21a) of 1) abuts, and the piston (21b) provided at the base of the rod (21) is a cylinder formed horizontally in the holder (17).
It is fitted inside (22), the rear side of the piston (21b) of the cylinder (22) is connected to the pressure oil line (23), and the line (23) is the hydraulic source.
(23a), chuck valve (23b), relief valve (23c)
The front side of the piston (21b) of the cylinder (22) is connected to the exhaust pressure passage (24) provided in the holder (17).

Cams (7), (7) are installed on the left and right sides of the lower surface of the upper die (6), while 180 ° apart so that the lower part of the upper die (2) sandwiches the lower part of the hole (2a). Lateral hole-shaped guide holes (2b), (2b) are formed, and side punches (8), (8) are horizontally slidably fitted in the guide holes (2b), (2b). At the opposite tips, the molding parts (8a), (8
a) is formed, and the side punches (8), (8) extending outward from the guide holes (2b), (2b) have the cams (7),
Cam portions (8b), (8b) that engage with (7) are provided.

The lower punch (9) is provided so as to face the upper punch (5), and at the forging set position, the upper forming part (9a) is the hole (2a) of the upper die (2).
The middle part (9b) is the hole of the middle die (3) facing the middle part or the lower part.
It faces as it is slidably fitted to (3b). The punch (9) consists of three parts, the left and right side members (10), (11), and the intermediate member (12) .The upper part of the side members (10), (11) is symmetrical to each outside. Protrusions (10a), (11a) that bulge in the lower neck (10b), (1
1b) and necks (10b), (11b) are provided with symmetrically inclined bases (10c), (11c) on the outer sides, and the necks (10b), (11b) are side punches (8), (8). ) Corresponding to the molding parts (8a), (8a) of the side member (1
The inner surfaces of (0), (11) facing each other are flat, and the upper part (12a) of the intermediate member (12) is sandwiched between them, and the top part (12b)
Forms a connecting surface with the tops (10d) and (11d) of the side members (10) and (11).

At the bases (10c), (11) of the side members (10), (11), horizontal outwardly extending bottom end receiving surfaces (10e), (11e) are formed at the base ends of the holes (3a). ) Arm part (1
0f) and (11f) hang down, and the inside of the arm (10f) and (11f) forms recesses (10g) and (11g) from the middle to the bottom, and the lower part of the arm (10h) and (11h) Are bent symmetrically so as to expand outwardly, while the intermediate part (12c) of the intermediate member (12) is in contact with both sides of the intermediate parts of the arm parts (10f) and (11f).
Furthermore, the lower part (12d) expands to face between the lower parts (10h) and (11h),
The intermediate member (12) is fixed and erected on the base (16). The lower part of the arm (10h), (11h) has recesses (10i), (11i) at the lower end,
Cylinders (13) that can be embedded vertically on the left and right in the base (16),
Engage the upper ends of the rods (13a) and (14a) of (14) to
The upper ends of a) and (14a) are pins (13b) and (14b) and are recessed (10i) and (11i).
Engage and connect with the long holes (10j), (11j) formed in the vertical wall of the.

In the above, the molding material (B) from above the hole (2a) of the upper die (2)
The material (B) is placed at the upper limit, and the lower end of the material (B) is supported on the receiving surfaces (10e), (11e) of the left and right side members (10), (11) of the lower punch (9), and the punch upper part ( 9a) is loosely fitted in the inner diameter of the material (B) to support the head (B ₁ ) from below, and the forming part (9a) of the lower punch (9)
FIG. 8 shows such a set state in which they are integrated.

Next, lower the upper punch (5) by lowering the upper die (6), and fit the upper punch (5) into the hole (2a) of the upper die (2) to form the molding material (B).
Press the head (B ₁ ) of the upper part from above, while lowering the upper mold (6)
(7), (7)) also descended, and the slope (7a) of this was the side punch.
The side punches (8) and (8) are symmetrically moved inward as a result of engaging the slopes (8c) of the cams (8b) of (8) and (8). The forming parts (8a), (8a) of the intruder penetrate inward in the radial direction from the outer periphery of the forming material (B), plastically deform the thick part (B ₃ ) to deform inward, and the thick part (B side members of the ₃₎ lower punch (9) (10), (neck of 11) (10b) is pressed and deformed in (11b), whereas, the molding part penetrated into the thick portion (B ₃₎ (8a) min The meat tends to flow upward as well, and the protrusions (10a), (11a) of the inner side punches (10), (11) face the upper part of the forming part (8b) at the forward limit. Enter the lower side of this, wrap the protrusions (10a), (11b),
On the other hand, the end face of the base end of the forming part (8a) of the side punches (8), (8)
(8d) and (8d) contact the outer peripheral surface of the thick part (B ₂ ) of the material (B) and pressurize it at the intrusion forming limit of the forming part (8a), and the flow of the meat radially outward. Regulate. This allows the piston pin boss (C
₄ ), the recess (C ₃ ) is molded by the molding part, and the projections (10a), (1
In a), the undercut recess (C ₆ ) is formed above the pin boss (C ₄ ). This is shown in FIG.

During the formation of the above undercut recess (16), the tissue penetrating into the outer circumference of the piston material (B) of the side punches (8), (8) flows under the top part (8a) of the lower punch (8), and The surplus tends to flow upwards, but at this time, the upper punch (5) is made of material.
Apply back pressure from above so that it does not move upward while touching the top of (B). The back pressure is the piston (21
b) The rod (22), which is obtained by introducing hydraulic pressure to the back side and is connected to the piston (21b) by the introduction of hydraulic pressure, moves left in FIG. 5, and as a result, the receiving block (20) moves left and the slope (20a ) (5c)
The action of lowers the upper punch (5) and thus the upper punch (5)
Is a material that corresponds to the pressure during molding of the side punches (8), (8).
Press (B) from above and press the upper meat to form the undercut recess (B6) with the lower punch (8) when forming the pin recess by the side punches (8), (8). .

After forming, raise the upper punch (5) and at the same time side punch
Move (8) and (8) backwards to release the molded product (C) from the constraints of the punches (5), (8) and (8). Next, the cylinders (13) and (14) are driven to raise the rods (13a) and (14a), and the side members (10) and (11) of the lower punch (9) connected to them are moved upwards. The lower part (10h) of the arm part (10f) of this part abuts the slope (3c) on this side of the concave part (3b), while the intermediate member (12) is fixed by the upward movement of the punch. While sliding from the inside of the upper part of (11),
Facing the recesses (10g) and (11g) of 0) and (11), they come off in this state,
The side member (10) is the opposite side member (11) due to the guiding action of the slope (3c).
The inner surfaces (10k) and (11k) of the upper part come into contact with each other at the end. The movement of the side member (10) to the right in the figure is not obstructed by the engagement of the rod (13) with the pin (13b) due to the long hole (10j), and the member (10) hits the member (11). Upon contact, the protrusion (10a) is pulled out from one of the undercut recesses (C ₆ ) of the molded product (C). This is shown in FIG.

Next, move only the rod (14a) of the cylinder (14) upwards,
As a result, the right side member (11) rises until the lower part (11h) of the arm portion comes into contact with this because the slope (3d) on this side is distant radially outward, while the left side member (10) The slope (3c) is left due to the upper limit of movement, the molded product (C) also rises at the upper limit of the member (11), and the protrusion (10a) at the upper part of the member (10) is biased inward. Therefore, the molded product (C) rises together with the member (11) without contacting the inner diameter of the molded product, and the protrusion (10) from the molded product to the member (10)
a) is extracted. This is shown in FIG.

As the member (11) continues to rise further, the member (11) shifts inward due to the action of the slope (3d), while the molded product is held by the clamp (15), which causes the protrusion of the member (11). The part (11a) moves inward, and the protrusion (11a) is removed from the undercut recess on this side, while the member (10) is lowered and returned to the molding position.
This is shown in FIG. 13, and subsequently, the member (11) is moved down to the molding position to complete the delivery of the molded product.

As described above, a molded product as shown in FIG. 3 was obtained.

In this way, the member (B) is simultaneously forged with the piston pin boss and the undercut recess, and the molded product is discharged.

(Effects of the Invention) According to the present invention as described in detail above, it is possible to simultaneously forge-mold the pin boss portion of the piston and the concave portion thereof while forging, and especially between the side punch and the lower punch. Since a back pressure was applied to the upper punch when forming the pin boss, the undercut recess can be accurately formed with high precision while keeping the tissue secret, and the machining of the undercut can be eliminated, minimizing the machining. In addition to improving production efficiency, the material yield is also improved by the above, which is advantageous in terms of cost, and because it is forging, the dimensional accuracy is also improved.
In addition to contributing to the reduction of machining, there are great advantages such as the fact that the top of the piston can be formed at the same time by pressing the head of the material.

[Brief description of drawings]

The drawings show an embodiment of the present invention and are shown in FIGS.
The figure shows the molding process. Fig. 1 is a view of the material, Fig. 2 is a cross-sectional view of the preformed material, Fig. 3 is a cross-sectional view of the molded product, and 4
FIG. 5 is a vertical sectional view of the forming apparatus, FIG. 5 is an enlarged view of the upper punch back pressure mechanism, FIG. 6 is a sectional view taken along the line 6-6 of FIG. 5, FIG. 7 is a plan view of the lower punch, and FIG. Diagram of preformed material set state,
FIG. 9 is a cross-sectional view of a molding state, FIG. 10 is a cross-sectional plan view showing the relationship between the lower punch and the side punches, and FIGS. 11 to 1
Fig. 3 is a cross-sectional view showing the molding product payout process step by step.
FIG. 14 is a sectional view of the piston, and FIG. 15 is a bottom view of the same. In the drawing, (B) is the piston material, (C) is the molded product, (C ₃ ) is the recess for the pin boss, (C ₄ ) is the boss, (2) is the die, (5) is the upper punch, and (20) ), (21) and (22) are back pressure load mechanisms, (8) is a side punch, (9) is a lower punch, and (10), (11) and (12) are lower punch dividing members.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koichi Watanabe 1-10-1 Shin-Sayama, Sayama-shi, Saitama Prefecture Within Honda Engineering Co., Ltd. (72) Tsutomu Takai 1-10-1 Shin-sayama, Sayama-shi, Saitama Prefecture Within Da Engineering Co., Ltd.

Claims (1)

[Claims] 1. A step of setting a piston material formed into a reverse cup shape by surrounding it with a die and setting it between upper and lower punches, and restraining the material from above with an upper punch and fitting a lower punch from below the material. And supporting the side punches from the outer periphery of the material inward in the radial direction of the material to form a recess for the piston pin boss, and the lower punch has a head inside the piston material In a divided structure composed of a plurality of members protruding in a direction, a back pressure is applied to the upper punch at the time of forming the piston pin boss concave portion by the side punch, and a material inner wall above the boss portion is formed between the upper punch and the lower punch head. A method for forging a piston, which comprises a step of simultaneously forming an undercut concave portion in a radial direction.