JP2013056363A - Method for manufacturing assembly type crank throw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems in manufacturing of a crank throw by forging as inequality of lateral bending angles to a workpiece, a pressure welding mark or thickness reduction of a bent outer surface, a wrinkle-like processing mark of a bent inner surface.SOLUTION: The method for manufacturing an assembly type crank throw includes: preparing a lower mold 2 having a recess 5 for forming a workpiece W and first and second tapered portions 6a, 6b provided on opposed surfaces in the recess 5, and an upper mold 3 protruded to and retreated from the recess 5 of the lower mold 2; and pressing down the workpiece W, which has 2W/(W-W) of substantially 1 and is longer than the upper end width of the lower mold 2, into the recess 5 of the lower mold 2 by the upper mold 3 at a position where the upper mold 3 passes through an angle-changed portion 11 at the boundary between the first tapered portion 6a and the second tapered portion 6b located deeper than the first tapered portion 6a in the lower mold 2, wherein Wis the thickness of the workpiece, Wis the lower end width of the upper mold, and Wis the opposite width within the recess at the angle-changed portion.

Description

  The present invention relates to a method for manufacturing an assembled crank throw.

A crankshaft used for a marine engine or the like has a pair of webs formed in a plate shape with respect to an axial middle portion of a journal shaft, and pins that hold the webs at a predetermined interval and in parallel with each other. It is the structure provided with the formed crank throw.
Conventionally, as a method of manufacturing such a crank throw by forging, two rotatable support rolls provided in parallel to each other and a punch that advances and retreats from above between both rolls. A method using a special forging device provided is known (see Patent Document 1).

  In the manufacturing method disclosed in Patent Document 1, a T-shaped material having a belt-like shape and a convex portion protruding downward in the longitudinal center is once manufactured, and further, the T-shaped material is formed on the T-shaped material. On the other hand, the bending material (secondary material) is used as a workpiece by performing a slight bending so that both ends in the longitudinal direction are slightly inclined upward. Then, the workpiece is placed so as to straddle both rolls (to be supported at two points), and the workpiece is pushed between the two rolls by lowering the punch and bent by 180 °, so that a predetermined amount is obtained. It was formed into a crank throw shape.

On the other hand, as another method for producing a crank throw by forging, there are a lower mold having a groove-shaped recess for forming a workpiece, and an upper part that advances and retreats from above the lower mold into the recess. A method using a mold-inserting forging apparatus provided with a mold is known (see, for example, Patent Document 2).
In the manufacturing method disclosed in Patent Document 2, a columnar material having a short axial length that covers the lower mold from the beginning at a shallow position in the recess (close to the recess entrance on the upper surface of the mold) is covered. Work material. Then, after inserting the workpiece into the recess of the lower mold, the workpiece is pressed down by lowering the upper mold, so that the workpiece is forged and deformed along the inner surface of the recess. In other words, a predetermined crank throw shape is formed.

Japanese Patent Laid-Open No. 6-179035 JP 52-111183 A

  When a long workpiece is employed as in the crank throw manufacturing method disclosed in Patent Document 1, there is a problem of imbalance between the left and right bending angles or the bending length that occurs when the workpiece is bent. In addition, problems such as pressure wrinkles (transfer wrinkles) and thinning caused by the lower mold occurring on the outer surface of the work material, and problems such as hook-shaped work wrinkles generated on the inner surface of the work material. It was found that various problems occur frequently (see FIG. 5). For this reason, the work material requires an excessive thickness in anticipation of the forging process, and a new problem has been confirmed that the yield is poor in terms of material.

  On the other hand, in the crank throw manufacturing method disclosed in Patent Document 1, as described above, after the T-shaped material is manufactured, the T-shaped material is slightly bent (see FIG. 2 in Patent Document 1). Since the material to be processed is applied, a preliminary bending apparatus is separately required and the number of processes is increased. As a result, there has been a great problem in terms of equipment and production efficiency. Further, since two supporting rollers are required, there is a problem that the apparatus is inevitably enlarged.

  Furthermore, if there is a difference in rotation angle between the two support rollers during forging, there is a problem that the left and right bending angles become unbalanced when the workpiece is bent. The punch cannot be stopped or raised while the punch is being lowered (lowered). Therefore, the problem of the bending angle imbalance cannot be solved. Naturally, for the same reason, problems such as pressure welding (transfer defects) and thinning on the outer surface of the workpiece are eliminated, and the problem of hook-shaped processing defects on the inner surface of the workpiece is solved. It couldn't be done.

In the crank throw manufacturing method disclosed in Patent Document 2, the work material fitted from the beginning into the recess of the lower mold is forged and deformed so as to be along the inner surface of the recess only by the pressing force of the upper mold. It does not disclose a technique for solving the problem.
The present invention has been made in view of the above circumstances, and when manufacturing a crank throw by forging, it is possible to suppress an increase in the size of the apparatus, and the problem of the left and right bending angle imbalance with respect to the workpiece, To provide an assembly-type crank throw manufacturing method capable of solving various problems such as problems such as pressure welding (transfer) or thinning on the outer surface of the bent surface, and problems such as wrinkled processing on the inner surface of the bent surface. Objective.

In order to achieve the above object, the present invention has taken the following measures.
That is, the present invention is a manufacturing method for manufacturing a crank throw by bending a workpiece into a V shape, having a groove-shaped recess for forming the workpiece, and in the recess A lower mold having at least a first taper portion and a second taper portion whose inclination angle becomes larger in the depth direction in the depth direction on the opposing surface, and an upper die that advances and retreats from above the lower die into the recess. And at a position where the upper mold passes through the bend portion formed at the boundary between the first taper part and the second taper part deeper than the first taper part in the lower mold. 2W _t / (W _o −W _P ) is approximately 1, and a workpiece longer than the upper end width of the lower mold is placed on the lower mold, and then the upper mold is used. A crank throw is manufactured by reducing a workpiece into a recess of a lower mold.

However,
W _t : thickness of workpiece
W _P : lower end width of upper mold
W _o : opposing width in the recess at the bend portion

Further, when the work material is pressed down into the recess of the lower mold by the upper die, the first taper portion is bent so that the bending angle of the work material becomes larger than 60 °, and the second taper portion Then, it is good to perform bending so that it may become 60 degrees or less.

In addition, while the lower end of the upper mold passes through the bendable portion of the lower mold, the upper mold is pressed while being changed in the horizontal direction within the range of the following formula. Is preferred.

0 ≦ Pressure position ≦ W _PP / 3
However, W _PP : Upper end width of upper mold

Still further, immediately before the lower end of the upper mold passes through the bent portion of the lower mold, the reduction by the upper mold is temporarily stopped, and the descaling process is performed on the inner side of the bent portion of the workpiece. After that, it is preferable to resume the reduction by the upper mold.

  In the manufacturing method of the assembled crank throw according to the present invention, the problem of imbalance of the left and right bending angles with respect to the work material, the problem of pressure contact wrinkles (transfer wrinkles) and thinning of the outer surface of the bending, and the wrinkle processing of the inner surface of the bending Various problems such as the problem of wrinkles can be solved, and a crank throw can be manufactured reliably.

It is a figure explaining the manufacturing method of the assembly type crank throw concerning the present invention over time. It is the perspective view which showed the lower metal mold | die of the mold insertion forging apparatus. It is the front view which showed the mold insertion forging apparatus and the workpiece. It is the figure which demonstrated the manufacturing method of the assembly-type crank throw concerning this invention in detail in time. It is the figure which showed the various defects which generate | occur | produce at the time of manufacture of an assembly type crank throw.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
2 and 3 show the mold forging device 1 used in the method for manufacturing an assembled die crank throw according to the present invention.
The mold insertion forging device 1 includes a lower mold 2 installed on a floor surface or the like, and an upper mold 3 provided above the lower mold 2.

In the following description, the up and down direction in FIG. 3 is referred to as the up and down direction (or the depth direction of a recess 5 described later) of the mold-inserting forging device 1, and the left-right direction in FIG. Direction or width direction.
First, an outline of the configuration and operation of the mold insertion forging device 1 will be described.
The lower mold 2 has a groove-shaped recess 5 in which the opening is recessed downward with the widthwise center of the upper end 2a being opened. The recess 5 is formed so as to pass through the lower mold 2 along the longitudinal direction of the groove. On the other hand, the upper mold 3 is sized to enter the recess 5 of the lower mold 2 and is formed in an inverted trapezoidal shape in which the lower end 3b is slightly narrower than the upper end 3a. The hydraulic pressure reduction device (not shown) moves forward and backward (up and down) from above the lower mold 2 into the recess 5.

  As the workpiece W, a material formed longer than the width of the upper end of the lower mold 2 (the length in the left-right direction of the entire mold across the upper portion of the recess 5) is employed. The workpiece W is formed in a band plate shape, and is provided with a convex portion d projecting downward (in the concave portion of the lower mold 2) at the center in the longitudinal direction. The workpiece W has a lower convex portion d facing the concave portion 5 of the lower mold 2 and both longitudinal ends projecting to the left and right sides of the lower mold 2 in the lower part. It is placed on the upper end 2 a of the mold 2.

  Accordingly, as shown in FIGS. 1 and 4, when the upper mold 3 is lowered with the workpiece W placed on the upper end 2 a of the lower mold 2, the workpiece W is moved closer to both ends in the longitudinal direction. In the state supported by the lower mold 2, the central part in the longitudinal direction is pushed downward by the upper mold 3. Therefore, the workpiece W is squeezed into the recess 5 of the lower mold 2 while being bent into a V shape, and is pressed against the opposing inner surfaces (left and right both sides) in the recess 5 to be forged. A predetermined crank throw shape is imparted to the workpiece W by this forging pressure.

In addition, although illustration is abbreviate | omitted, the recessed part 5 of the lower metal mold | die 2 is naturally provided with the convex part for giving the various shapes required for crank throw shape with respect to the opposing inner surface or groove bottom part. Is possible. Also, the upper mold 3 can be provided with a recess that is recessed upward from the lower end 3b.
Next, the detailed structure of the die-forging device 1 will be described.

In the lower mold 2, the concave portion 5 is provided with a taper portion 6 whose inclination angle increases with increasing depth in the depth direction with respect to the inner surfaces facing each other. The taper portion 6 includes at least a first taper portion 6a and a second taper portion 6b disposed at a position deeper than the first taper portion 6a.
In the present embodiment, the first taper portion 6a is disposed at a position (that is, the uppermost position in the depth direction) from the upper end portion 2a of the lower mold 2 into the recess 5, and the first taper portion 6a and the recess 5 The 2nd taper part 6b is arrange | positioned so that it may connect between bottom parts (namely, the lowest position of a depth direction). That is, the concave portion 5 of the lower mold 2 has a two-step inclined shape. Along with this, a first beveled portion 10 is generated at the boundary between the upper end portion 2a of the lower mold 2 and the first taper portion 6a, and a second bend angle is formed at the boundary between the first taper portion 6a and the second taper portion 6b. Part 11 is generated.

  In the lower mold 2, the inclination angle β (the angle on the acute angle side where the second taper portion 6 b rises from the horizontal plane) applied to the second taper portion 6 b is set to 70 ° ≦ β ≦ 85 °. If the inclination angle β is less than 70 °, it is difficult to make the final bent shape of the workpiece W smaller than 60 °. When the final bent shape cannot be smaller than 60 ° (in other words, when the bent shape is larger than 60 °), not only the work time in the finishing process, which is a process after the bending, is increased, but also in the finishing process. This is unsuitable because it increases the risk of wrinkling during work. Further, as the inclination angle β exceeds 85 ° and approaches 90 °, the workpiece W becomes unsuitable after being bent (cannot be taken out), which is inappropriate.

Further, the angle φ1 of the first beveled portion 10 and the angle φ2 of the second beveled portion 11 are such that φ1 is 120 ° or more and φ2 is 140 ° or more. In addition, the sum of these angles φ1 and φ2 is set to satisfy 275 ° ≦ φ1 + φ2 ≦ 290 °.
By satisfying these conditions, the bending angle θ of the workpiece W is suppressed within a predetermined range (so that strong bending is not performed at a stretch), and the workpiece W by the first taper portion 6a is suppressed. During the transition from the initial bending to the secondary bending by the second tapered portion 6b, the workpiece W can be guided in a surface contact state by the first tapered portion 6a. As a result, it is possible to prevent pressure wrinkles (transfer wrinkles) and thinning due to the lower mold 2 generated on the outer surface of the workpiece W being bent. As a result, there is no wrinkle of 60 ° or more with respect to the workpiece W. Can be bent.

Furthermore, the internal dimension of the recess 5 of the lower mold 2 and the outer dimension of the upper mold 3 are related as follows in relation to the thickness of the workpiece W.
That is, 2W _t / (W _o −W _P ) is substantially 1 at a position where the upper die 3 passes through the second bendable part 11 while rolling down the workpiece W. Preferably, 0.9 ≦ 2W _t / (W _o −W _P ) ≦ 1.1. By satisfying this condition, when the work material W is bent, the material flow generated on the surface of the work material W or inside thereof becomes smooth, and the work iron appearing like a wrinkle on the surface of the work material W. Can be prevented.

Here, when 2W _t / (W _o −W _P ) is less than 0.9, the gap between the lowered upper die 3 and the second taper portion 6b is not filled with the workpiece W. In other words, a shortage of deformable material occurs, and surplus or wrinkles generated on the bent inner surface of the workpiece W cannot be crushed. When 2W _t / (W _o −W _P ) exceeds 1.1, an excessive state of deformed material is formed in the gap portion between the upper mold 3 and the second taper portion 6b, and the lower mold 2 and the upper mold An excessive reduction force acts on the mold 3, which leads to an increase in the size of the apparatus and becomes inappropriate.

In addition, the 1st beveled part 10 and the 2nd bendable part 11 may be formed so that an edge may arise in a mutually adjacent part, and may be formed by chamfering by a round surface or an inclined surface.
Next, a usage mode of the die-insertion forging apparatus 1, that is, a method for manufacturing an assembled crank throw according to the present invention will be described.
First, the workpiece W is placed on the upper end portion 2a of the lower die 2 in a state where the longitudinal direction thereof is in the left-right direction while the upper die 3 of the die-insertion forging device 1 is made to rise and stand by. In this state, the upper mold 3 is lowered, and the workpiece W is pressed down into the recess 5 while being bent into a V shape by the upper mold 3.

  In the initial stage of reduction, the workpiece W is supported by the first beveled portion 10 generated at the boundary between the upper end portion 2a of the lower mold 2 and the first taper portion 6a, while the central portion in the longitudinal direction is the upper mold 3. Therefore, the workpiece W is bent so as to follow the inclination angle α of the first taper portion 6a. As a result, the workpiece W is bent within a range in which the bending angle θ is larger than 60 °.

  In the process in which the workpiece W is bent, it is confirmed whether there is a left-right imbalance in the bending angle and the bending length of the workpiece W along the first tapered portion 6a. The confirmation operation for this purpose may be performed by visual observation by the operator, or may be performed by a detection device using an image recognition system or the like. In addition, when performing the confirmation work, it is preferable that the lowering (lowering) by the upper mold 3 is temporarily stopped or the upper mold 3 is slightly raised in some cases.

When the left and right imbalances are detected in the bending angle and the bending length of the workpiece W by this confirmation work, the lower end portion 3b of the upper mold 3 (the portion that presses down the workpiece W) is Before passing through the second bendable section 11 of the lower mold 2, the pressure position of the upper mold 3 is changed in the horizontal direction (left-right direction) toward the direction in which the imbalance should be corrected. In this way, the lower mold 3 is continuously pressed down. Changing of the pressure position of the upper die 3, the width of the upper end portion 3a of the upper die 3 at the W _PP, within a range that satisfies the following expression.

That is,
0 ≦ Pressure position ≦ W _PP / 3

Here, “0” means that the position is not changed (there is no substantial movement amount), and “W _PP / 3” means the absolute value (movement amount to the right and left). To change the pressing position of the upper mold 3, the upper mold 3 is stopped and the upper mold 3 is slightly raised, and the upper mold 3 is moved in the horizontal direction or the lower mold 3 is moved. This may be done by moving 2 in the horizontal direction.

Further, prior to executing the change of the pressing position for the upper mold 3, the descaling process is performed. This descaling process can be performed by blowing high-pressure water or high-pressure air to the inside of the bent portion of the workpiece W. Depending on the case, a brush-like or spatula-like sliding contact member may be slid inside the bent portion of the workpiece W so as to sweep or scrape the scale.
This descaling operation may be performed after the pressure position of the upper mold 3 is changed.

  This descaling process is performed immediately before the lower end 3b of the upper mold 3 passes through the second bendable section 11 of the lower mold 2, and at this time, the reduction (lowering) by the upper mold 3 is temporarily stopped. Shall be allowed to. Here, “immediately before” means that the workpiece W is undergoing initial bending by the first taper portion 6a and before the workpiece W exceeds the second bendable portion 11, further speaking, The state before receiving the secondary bending action by the second taper portion 6b.

After execution of the descaling process, the reduction by the upper mold 3 is resumed, and the second taper portion 6b is bent so that the bending angle θ of the workpiece W is 90 ° or less. Thereby, a shape required as a crank throw shape is given to the workpiece W.
As is clear from the above detailed description, in the method of manufacturing an assembled crank throw according to the present invention, a plurality of tapered portions 6 are provided in the recess 5 of the lower mold 2 so that the workpiece W is bent stepwise. Therefore, there is a problem of imbalance of the left and right bending angles with respect to the work material W, a problem of pressure welding (transfer defect) and thinning of the outer surface of the bending, and a problem of wrinkle processing of the inner surface of the bending. Various problems can be solved. Naturally, an apparatus for applying a preliminary bending to the workpiece W is not necessary, and therefore, the number of steps involved in the preliminary bending is not increased. As a result, there is no problem in terms of equipment and work.

The relationship between the internal dimension of the recess 5 of the lower mold 2 and the outer dimension of the upper mold 3 and the thickness of the workpiece W in the mold forging device 1 is “2 W _t / (W _o −W _P )” and “defective The result of conducting a reduced model experiment (an experiment with a 1/5 model) for “occurrence of occurrence” is shown below.
In the reduction model experiment, the lower mold 2 shown in FIGS. 2 and 3 has a width dimension of the upper end portion 2a (the length in the left-right direction of the entire mold straddling the upper part of the recess 5) of 650 mm. The vertical dimension (height) was 550 mm. For reference, the first beveled portion φ1 = 128 °, and the first beveled portion 10 was rounded with a radius of 100 mm. The second taper angle β = 82 °, the second variable angle portion φ2 = 150 °, and the second variable angle portion 11 was rounded with a radius of 200 mm.
The experimental results are shown in Table 1.

In Table 1, the “two-step taper” has a first taper portion 6a, a second taper portion 6b, and a bend portion formed therebetween, and is the mold 2 of the present invention. “One-step taper” is a conventional mold having one taper portion and no bendable portion.
In Table 1, the “first-stage taper bending angle” is the bending angle θ of the workpiece W at the first taper portion 6a, and the “second-stage taper bending angle” is the second taper portion 6b. Is the bending angle θ of the workpiece W.

As is clear from Table 1, 0.90 ≦ 2 W _t / (W _o −W) in order to prevent defects such as wrinkled wrinkles, press contact wrinkles, and left and right bending imbalances from occurring. It was confirmed that _P ) ≦ 1.03. However, in the upper limit, it has been experimentally confirmed that 1.1 can be used as a guide if the allowable maximum principal stress acting on the lower mold 2 is 500 MPa or less. In addition, the presence or absence of wrinkled wrinkles, pressure welding wrinkles, and left-right bending imbalance is based on visual confirmation. A wrinkled wrinkle (evaluation Δ) when 2 W _t / (W _o −W _P ) = 0.85 means a situation where it can be used as a product through a great deal of rework, and should be avoided if possible It is an occurrence state.

Further, by satisfying 0.90 ≦ 2W _t / (W _o −W _P ) ≦ 1.03, the working time (the time required from FIG. 4 (a) to FIG. 4 (e)) can be significantly reduced. The inventors have confirmed. Furthermore, the inventors of the present application have greatly contributed to correcting the uneven bending of the workpiece W by the first taper portion 6a, and the forging pressure of wrinkles generated by the workpiece W by the second taper portion 6b, It has been confirmed that it greatly contributes to the drawing.

The present invention is not limited to the above-described embodiment, and can be appropriately changed according to the embodiment.
For example, in the lower mold 2, the taper portion 6 has an inclination angle larger than that of the first taper portion 6 a and between the first taper portion 6 a and the second taper portion 6 b. A plurality of tapered portions such as a third tapered portion, a fourth tapered portion,. In that case, the second beveled portion described in the embodiment is a corner portion that is formed at the boundary between the tapered portion A and the subsequent tapered portion B, and the tapered angle of the tapered portion B is 70 ° or more. . For example, when the third taper portion is formed so as to follow the first taper portion 6a and the taper portion of the third taper portion has a taper angle of 70 ° or more, the boundary between the first taper portion 6a and the third taper portion is This is the second beveled section described in the above embodiment.

  Further, when the work material W is rolled down by the upper mold 3, when the generation of scale is not recognized, or when the generation amount of the scale is small enough not to cause the processing flaw, the descaling process may be omitted. Is possible.

DESCRIPTION OF SYMBOLS 1 Mold insertion forging apparatus 2 Lower mold | type 2a Upper end part 3 Upper mold | type 3a Upper end part 3b Lower end part 5 Recessed part 6 Tapered part 6a 1st taper part 6b 2nd taper part 10 1st bend part 11 2nd bend part W Work material d Convex part

Claims (4)

A manufacturing method for manufacturing a crank throw by bending a workpiece into a V shape,
A groove-shaped concave portion for forming the workpiece is provided, and at least a first taper portion and a second taper portion whose inclination angle increases at a deeper position in the depth direction on the opposing surface in the concave portion. Prepare a lower mold and an upper mold that advances and retreats from above the lower mold into the recess,
2 W _t / (W _o −) at a position where the upper mold passes through the bend portion formed at the boundary between the first taper part and the second taper part deeper than the first taper part in the lower mold. W _P ) is approximately 1, and a workpiece that is longer than the upper end width of the lower mold is placed on the lower mold,
Thereafter, the crank throw is manufactured by pressing the workpiece into the concave portion of the lower mold with the upper mold, and the manufacturing method of the assembled crank throw.
However,
W _t : thickness of workpiece
W _P : lower end width of upper mold
W _o : opposing width in the recess at the bend portion When rolling down the workpiece into the recess of the lower mold by the upper mold,
The first taper portion is bent so that a bending angle of the workpiece is larger than 60 °, and the second taper portion is bent so as to be 60 ° or less. The manufacturing method of the assembly type crank throw described. While the lower end portion of the upper mold passes through the bendable portion of the lower mold, the upper mold is pressed while being horizontally changed within the range of the following formula. A method of manufacturing an assembled crank throw according to claim 1 or 2.

0 ≦ Pressure position ≦ W _PP / 3
However, W _PP : Upper end width of upper mold
Immediately before the lower end of the upper mold passes through the bend of the lower mold, the reduction by the upper mold is temporarily stopped,
Descale processing is performed on the inside of the bent portion of the workpiece,
Thereafter, the reduction by the upper mold is resumed. The method of manufacturing an assembled crank throw according to any one of claims 1 to 3.