JPH0256978B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a die forging method for a crank arm with a half journal used as a material for a welded crankshaft.

(Prior Art) In recent years, marine diesel engines have tended to have lower speeds and higher torque in order to achieve low fuel consumption and high efficiency.

Under these circumstances, the crankshaft, which is one of the engine's power transmission components, has been replaced with a welded journal structure instead of the conventional shrink-fit construction in order to reduce weight and transmit large torque. It is being done.

As shown in FIGS. 1A and 1B, the crankshaft material 101 to be welded at the journal part includes a crank pin part 102, both crank arm parts 103, 103,
Both half journal parts 104, 104 are connected.

The present applicant proposed a die forging method for a crank arm member in which the crank pin portion and the crank journal portion are welded at two locations in Japanese Patent Application No. 58-27659 entitled “Die Forging Method for Crank Arm Members.” This is a different manufacturing method. Furthermore, it is also possible to apply the bending forging method or the ring forging method disclosed in Japanese Patent Publication No. 35-612 filed by the present applicant entitled "Mold Forging Method for Crank Arm".

That is, in the bending forging method, the crank pin part 102'a, both crank arm parts 103'a, and both half journal parts 10 shown in FIG.
A material with 4'a formed thereon is prepared, and a crank arm with a half-journal part is manufactured through a bending process as shown in FIG. In the ring forging method,
As shown in FIG. 12, using the ring member shown in FIG. 12A, the back cut hole widening step shown in FIG. Two crank arms with half-journal parts are manufactured through the forming/pin hole enlarging process and the finishing process shown in E of the same figure. However, the above two methods have complicated manufacturing processes and low yields.
The cost will be high.

It is also possible to apply the R-R forging method and the T-R forging method, but this would be inappropriate for small lot production of large crank arms due to high equipment costs.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and is made of a prismatic material with a rectangular cross section, and includes an upper end surface of both crank arm parts, an upper half part of both half journal parts, and both crank arm parts. an upper mold having a molded surface and a through hole in the center forming the upper three outer surfaces of the upper mold, the lower end surfaces of both crank arm parts, the lower half of the crank pin part, and the lower three outer surfaces of both crank arm parts. A half-journal can be made with a small number of steps by using a lower mold having a molding surface that forms a lower half of both half-journal parts, an insert, and a split plate that forms an upper half of a crank pin part. This provides a die forging method for manufacturing crank arms with attached crank arms.

(Example) A die forging method for a crank arm with a half journal according to the present invention will be described with reference to the drawings.

First, the molds and accessories used in carrying out the present invention will be explained based on FIGS. 2 to 5. Figure 2 A and B show the upper mold 1. 1a is a rectangular cross-section hole into which a part of the rectangular column material 100 (hereinafter referred to as the material) shown in FIG. semicircular grooves connected to both sides of the rectangular cross-section hole 1a;
1c is a half-journal part 104 in the center of the upper mold 1 in order to insert the insert 3 or split plate 4 to be described later.
The through holes 1d are provided on both sides of the rectangular cross-sectional hole 1a and are guide grooves of the upper mold connected to both sides of the through hole 1c. That is, the upper mold 1 has the upper end surfaces 1 of both crank arm parts.
03a, a molded surface forming the upper halves of both half journal parts 104, and the upper three outer surfaces of both crank arm parts, and a through hole 1c in the center.

Figure 3 A and B show the lower mold 2. 2a is material 10
It is a hole with a rectangular cross section into which 0 is inserted, and the end surfaces 2c on both sides thereof are formed to fit the lower end surfaces 103b of both crank arms, and the end surfaces 2c on both sides of the end portion
e is the inclined side surface 103 of the tip of both crank arms.
c. A semicircular concave projection 2f for forming a crank pin portion 102 is provided at the intermediate portion of both end surfaces 2c. Further, both guide grooves 2d of the lower die for guiding the split plate 4 are connected to both guide grooves 1d of the upper die. Each of the grooves 2b is a semicircular groove that is connected to both sides of the rectangular cross-sectional hole 2a, and is combined with both semicircular grooves 1b of the upper die to form both half journal parts 104, respectively. Therefore, the lower mold 2 has a molding surface that forms the lower end surfaces of both crank arms, the lower half of the crank pin, and the lower three outer surfaces of the crank arm.

FIGS. 4A and 4B show the insert 3 having a rectangular cross section that is inserted to close the through hole 1c of the upper mold.

5A and 5B show the split plate 4 inserted through the through hole 1c and guided to both guide grooves 1d and 2d. A semicircular recess 4a is formed at the tip, and the split plate 4 is press-fitted into the center of the material 100. The material 100 is divided to form the inner surfaces of both crank arm parts 103, and the crank pin part 10 is formed in cooperation with the semicircular concave projection 2f.
form 2.

Next, the process of die forging a crank arm with a half journal using the above die and accessories will be explained with reference to FIGS. 6 to 10.

(1) In the first step, as shown in Fig. 7, the material 100 heated to the hot working temperature is inserted into the rectangular cross-sectional hole 2a of the lower mold, and the rectangular cross-sectional hole 1a of the upper mold is inserted into the material 100.
The upper mold 1 is placed so as to cover the upper part of the mold 00, and the through hole 1c of the upper mold is closed with the insert 3.

(2) In the second step, as shown in FIG. 8, the upper die 1 and the insert 3 are pressed until they come into contact with the lower die 2 using a press not shown, and the material 100 is pushed into the lower die 2. Upper mold semicircular groove 1b and lower mold semicircular groove 2b
bulge into the circular groove formed by.

(3) In the third step, as shown in Fig. 9, the insert 3 is removed, the split plate 4 is inserted into the through hole 1c of the upper mold, and the upper mold 1 is left in a free state, and only the split plate 4 is shown in the figure. The material 100 is pressed into the material 100 by an external press to fill the space of the lower die 2, and the semicircular concave portion 4a of the split plate and the semicircular concave protrusion 2 of the lower die are
A crank pin portion 102 is formed with f. At this time, a part of the material 100 extruded into the space formed by both semicircular grooves 1b and 2b causes the upper mold
rises slightly.

(4) In the fourth step, as shown in Fig. 10, with the split plate 4 in a free state, only the upper mold 1 is pressed and the lower mold 2 is pressed.
Both half-journal parts 104 are formed by both semicircular grooves 1b and 2b in close contact with each other.

Through the above four steps, the die forging of the crank arm with a half journal is completed.

(Structure of the Invention) The die forging method for a crank arm with a half journal according to the present invention includes, as a die and its accessories,
An upper mold having a molded surface forming the upper end surfaces of both crank arm parts, upper half parts of both half journal parts, and upper three outer surfaces of both crank arm parts, and a through hole in the center part, and both crank arm parts. a lower mold having a molded surface forming a lower end surface, a lower half of the crank pin part, the lower three outer surfaces of both crank arm parts, and a lower half of both half journal parts, a nest, and a crank pin part; (1) Insert a material made of a rectangular columnar material with a rectangular cross section heated to hot working temperature into the lower mold, and place the upper mold on the material. The first step is to close the through hole of the upper mold with the insert, (2) the second step is to press the upper mold together with the insert and bring the upper mold into contact with the lower mold, (3) to move the insert from the upper mold. The third step of removing and inserting the split plate into the through hole of the upper mold, leaving the upper mold in a free state, and pressing only the split plate into the material; (4) inserting the split plate into the upper mold with the split plate in a free state; This is a die forging method for a crank arm with a half journal, in which the above four steps are carried out in sequence: the fourth step is to press the chisel into close contact with the lower mold.

(Effect of the invention) Therefore, the following effects are obtained.

(a) A crank arm material with a half journal could be provided using a simple mold and a small number of steps.

(b) Since it is molded using a closed mold, the shape is close to the final shape of the product, with high precision and a high yield.

(c) The high pressure generated within the mold provides a sufficient training effect, and high reliability is expected when used as a crankshaft.

(d) Compared to the R-R method and the T-R method, no special equipment is required, the initial cost of the mold is low, and it is suitable for small-lot production of large crank arms.

[Brief explanation of drawings]

Fig. 1A is a front view of the crankshaft material to be welded at the journal part, Fig. 1B is a side view of the same, Fig. 2A is a sectional view of the upper die used in the present invention, and Fig. 2B is a sectional view of the upper die used in the present invention. Figure 2A is a sectional view taken along the - line, Figure 3A is a sectional view of the lower mold used in the present invention, Figure 3B is a sectional view taken along the - line in Figure 3A, and Figure 4A is a sectional view of the insert. Front view, Figure 4B is a side view of the insert, Figure 5A is a front view of the split plate, Figure 5B is a side view of the split plate, and Figure 6 is a perspective view of the material used in the present invention. , FIG. 7 is a sectional view explaining the first step according to the present invention, and FIG. 8 is a cross-sectional view explaining the second step,
Fig. 9 is a sectional view illustrating the third step, Fig. 10 is a cross-sectional view illustrating the fourth step, Fig. 11 A and B are process explanatory diagrams of a forging method for a crank arm with a half journal by the bending forging method, and Fig. 12 Figures A, B, C, D,
E is a process explanatory diagram of a forging method for a crank arm with a half journal using a ring forging method. 1...Upper mold, 1a...Rectangular cross section hole, 1b...Semicircular groove, 1c...Through hole, 2...Lower mold, 2a...Rectangular cross section hole, 2b...Semicircular groove, 2c...Tip surface, 2e...Both sides of tip part , 2f... semicircular concave projection, 3... nest, 4
...Split plate, 4a...Semicircular recess.

Claims (1)

[Scope of Claims] 1. A mold and its accessories include a mold cutting surface forming the upper end surfaces of both crank arm parts, the upper half of both half journal parts, and the upper three outer surfaces of both crank arm parts, and the center. an upper mold having a through hole in the part;
A lower mold having a molded surface forming the lower end surfaces of both crank arms, the lower half of the crank pin, the lower three outer surfaces of both crank arms, and the lower half of both half journal parts; (1) Insert a material made of a rectangular columnar material with a rectangular cross section heated to hot working temperature into the lower mold, and place the upper mold on top of the material. (2) a second step of pressing the upper mold together with the insert to bring the upper mold into contact with the lower mold; (3) inserting the upper mold into contact with the lower mold; The third step is to remove the child from the upper mold and insert the split plate into the through hole of the upper mold, leaving the upper mold free and pressing only the split plate into the material. (4) Freeing the split plate A method for die forging a crank arm with a half-journal, characterized in that the above four steps are sequentially performed, including a fourth step of pressing only the upper mold to bring it into close contact with the lower mold.