JP4819748B2 - Method for manufacturing rocker arm - Google Patents

Description

  The present invention relates to a method for manufacturing a rocker arm for opening and closing a valve in a valve operating mechanism in an internal combustion engine of a vehicle, for example.

  In a valve mechanism of an internal combustion engine for a vehicle, a rocker arm is provided for converting the rotational motion of a cam that rotates in conjunction with a crankshaft into the reciprocating motion of a valve stem in a valve such as an intake valve or an exhaust valve. Yes. This rocker arm opens and closes the valve by swinging the pivot shaft at the end in the longitudinal direction as a fulcrum with the rotation of the cam and moving the valve stem up and down by the end on the swing side. is there.

  The rocker arm has a valve stem contact side end portion having a U-shaped cross section on one end side in the longitudinal direction, and is configured such that the valve stem is in contact with the bottom wall (connection wall) thereof. Furthermore, a pair of valve stem guide walls extending along the longitudinal direction are provided on both sides of the lower surface of the connecting wall of the valve stem contact side end, and the valve stem is disposed between the guide walls, The horizontal displacement of the rocker arm with respect to the valve stem is prevented.

  Since such a rocker arm has a complicated shape and also requires high rigidity, conventionally, it has been generally manufactured by forging or precision casting (lost wax).

  However, in recent years, as the internal combustion engine has increased in speed and output, reduction in weight of the rocker arm is desired in order to reduce the inertia weight, and many techniques for manufacturing the rocker arm by press working have been proposed.

  When manufacturing a rocker arm by press working, after obtaining an intermediate product with a U-shaped cross section by bending, a thickened portion is formed at the guide wall forming portion at the end of the valve stem contacting side of the intermediate product. A method of forming the thickened portion to form a valve stem guide wall is well known.

For example, in the method of manufacturing a rocker arm shown in Patent Document 1 below, the entire side wall is pressed downward against the valve stem contact side end formed into a U-shaped cross section by bending, After increasing the thickness on both sides of the bottom surface of the bottom wall at the contact end, the increased thickness portion is pressed inward from both sides to form the increased thickness portion in a downward projecting shape. A stem guide wall is formed.
JP 2001-198641 (Claims, FIG. 4-12)

  In the conventional method of manufacturing a rocker arm shown in Patent Document 1, a vertically movable mold for pressing both side walls downward, and a left and right (horizontal) direction movable mold for pressing the thickened portion inwardly from both sides. Therefore, it is necessary to press work from four directions, up, down, left and right. That is, since the direction of movement of the mold is different for each process, there is a problem that processing becomes difficult and productivity is lowered. In addition, since the movement of the mold becomes complicated, the molding equipment itself becomes complicated, and there is a problem that the equipment becomes large and heavy.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a rocker arm manufacturing method capable of improving productivity, simplifying equipment, and reducing size and weight.

  In order to achieve the above object, the present invention is summarized as follows.

[1] It has both side walls that extend in a predetermined direction and are arranged in parallel, and one end side connection wall that connects the lower portions on one end side in the longitudinal direction of the both side walls, A first step of obtaining a first intermediate product provided with a raised portion in an upwardly projecting manner;
By pushing the build-up portion of the first intermediate product downward with a pressing mold and causing the outer portions of both side walls to plastically flow downward, the meat filling portions are respectively formed on the outer sides of the lower end side portions of the both side walls. A second step of obtaining a second intermediate product;
A third intermediate product in which the meat filling portions on both sides are respectively formed on the rough forming wall portion by cutting the inside of the meat filling portion on both sides of the one end side connecting wall of the second intermediate product from the lower side by a cutting die. A third step of obtaining
By forming the one end side connecting wall of the third intermediate product with a finishing die, the rough forming wall portions on both sides are formed on the valve stem guide wall, and the valve stem contact surface is formed between the valve stem guide walls. And a fourth step of obtaining a formed rocker arm.

  [2] The method for manufacturing a rocker arm according to the preceding item 1, wherein an inclined surface that gradually increases toward the outside is formed on the inner side of the built-up portion at the upper edge of both side walls of the first intermediate product.

[3] In the first step, the flat plate product is bent in a U-shape to form both side walls on both sides of the one end side connecting wall, and the both side walls are constrained on the outer side surfaces of both side walls. Pressing the inner corner part at the upper edge of the upper part, and projecting the outer part upwardly to form the build-up part,
3. The method for manufacturing a rocker arm according to item 1 or 2, wherein the bending step and the imposition step are performed simultaneously.

  [4] The method for manufacturing a rocker arm according to any one of items 1 to 3, wherein a width of the cutting die is set larger than a distance between the side walls.

  [5] Any one of items 1 to 4 described above, wherein at least one of the first to fourth steps is performed while restraining both sides of the one end side connection wall and both side walls in the rocker arm longitudinal direction. The manufacturing method of the rocker arm as described in any one of.

  According to the manufacturing method of the rocker arm of the invention [1], the pressing direction is specified in the vertical direction, so that the processing can be performed smoothly, the processing speed can be improved, and the productivity can be improved. Furthermore, since the mold only needs to be moved in the vertical direction, the production facility can be simplified and reduced in size and weight.

  According to the method for manufacturing a rocker arm of the invention [2], since the inside of the built-up portion is formed on an inclined surface that gradually increases toward the outside, the amount of flow of meat when the built-up portion is pushed in is increased. More than the inside, the meat filling portion can be reliably formed on the outside of the both side portions of the lower end of the both side walls.

  According to the rocker arm manufacturing method of the invention [3], since the bending process and the imposition process are performed at the same time, the number of processes can be reduced and the production can be reduced as compared with the case where these processes are performed separately. Efficiency can be further improved.

  According to the rocker arm manufacturing method of the invention [4], when the inside of the meat filling portion of the second intermediate product is cut in the third step, it is possible to prevent the shear stress from concentrating on the cutting position and to generate a crack. Can be prevented. Further, the space between both valve stem guide walls can be widened, and a sufficiently large valve stem contact surface can be formed.

  According to the method for manufacturing a rocker arm of the invention [5], since the both ends of the connecting wall on one end side and the rocker arm length direction on both side walls in the intermediate product are constrained during the vertical pressing process, The flow in the direction can be effectively prevented, and the processing accuracy can be improved.

  Hereinafter, the manufacturing method of the rocker arm which is an embodiment of the present invention is explained in detail based on a drawing. As shown in FIGS. 1 (d) and 2, the rocker arm (10) manufactured in the present embodiment includes a pair of side walls (20) extending in the longitudinal direction and arranged in parallel, and both side walls (20 ) Between one end side connection wall (30) for connecting one end side in the longitudinal direction (valve stem contact side) and the other end side lower part of both side walls (20), and has a pivot engagement recess (41). The other end side connection wall (40) is comprised. Furthermore, the shaft fixing hole (16) is formed in the intermediate part of both side walls (20). A pair of valve stem guide walls (35) parallel to the longitudinal direction are formed on both sides of the lower surface side of the one end side connecting wall (30). A space between the guide walls (35) is configured as a valve stem contact surface (30a) for supporting a valve stem contact having a predetermined curvature.

  In FIG. 2, in order to facilitate understanding of the invention, it is shown in an upside down state with respect to the actual use state (the same applies to the following FIGS. 3 to 5).

  In order to manufacture the rocker arm (10) having the above-described structure, as shown in FIG. 3, first, a flat blank product (11) having a shape in which a predetermined region of a steel plate as an original plate is punched and both sides protrude in an arc shape. Get.

  Next, as shown in FIG. 4, by punching a punch for punching into the flat blank product (11), the middle region of the flat blank product (11) is punched out to form a drum-shaped central hole (15). At the same time, a predetermined area on both sides is punched out to form circular shaft fixing holes (16) to obtain a flat blank product (12) with holes.

  Further, the end intermediate region of the flat blank product (11) is recessed by overhanging to form a hemispherical pivot engaging recess (41).

  In this embodiment, the flat plate product is constituted by the flat blank product (11) and the flat blank product (12) with holes.

  The blanking process for punching the original plate, the drilling process for the center hole (15), the drilling process for the shaft fixing hole (16), and the overhang forming process for the pivot engaging recess (41) are limited. It is not a thing and you may carry out in any procedure. For example, all of these processes may be performed simultaneously, two or more processes may be performed simultaneously, and each process may be performed sequentially.

  Next, as shown in FIG. 1A and FIGS. 5 to 7, the flat plate blank product (12) with holes is bent into a U shape (inverted U shape) and arranged in parallel. It has both side walls (20) and one end side connection walls (30) that connect lower portions on one end side in the longitudinal direction of both side walls (20), and is built up on the outer side at the upper edge of both side walls (30). The first intermediate product (1) provided with the part (25) is produced.

  The bending punch (50) used for this bending process is provided with a pressing part (51) for pressing the flat plate blank product (12) with holes at the tip. Further, the both sides of the proximal end side of the pressing portion (51) of the bending punch (50), that is, the connecting portion between the pressing portion (51) and the body portion, gradually becomes narrower as the punch width goes toward the distal end side. In this way, inclined surfaces are formed, and the inclined surfaces on both sides thereof are configured as a pair of imposition portions (52).

  This bending punch (50) is driven into the flat plate blank product (12) with holes supported by the fixed mold (55), so that the blank product (12) becomes U by the pressing portion (51) at the tip. It is pushed and bent into a letter shape. At the same time, the portion corresponding to the inner corner portion of the both side walls (20) of the blank product (12) is pushed in by the pair of imposition portions (52), and the material inside the upper end surface of the both side walls (20) is outside. To flow. Thereby, the outer side of the upper end edge of both side walls (20) protrudes upward, and the build-up part (25) is formed.

  In addition, while the inside of this build-up part (25) is formed in the inclined surface (23) which becomes high gradually as it goes outside, an upper end is formed in a substantially flat flat surface (24).

  In the bending step of the present embodiment, both side walls (20) on one end side of the flat blank product (12) and both sides of the rocker arm length direction of the connecting wall (30) (the direction facing the paper surface of FIG. 6). The bending punch (50) is driven in a state in which the front and rear sides are constrained by a fixed mold (not shown).

  In this embodiment, the process (bending process) of bending flat plate-shaped blank product (12) with a hole, and the process of forming a built-up part (25) on the outer side of the upper end edge in both side walls (20) ( The imposition process) constitutes the first process.

  After producing the first intermediate product (1), the first intermediate product (1) having the meat filling portion (26) on the outer side of the lower end side portions of the side walls (20) by press molding as shown in FIG. 1 (b) and FIG. Two intermediate products (2) are produced.

  That is, the upper ends of both side walls (20) in a state where the inner and outer surfaces of both side walls (20) on one end side of the first intermediate product (1) and the lower surface of the connecting wall (30) are constrained by the fixed mold (65). The flat surface (24) of the built-up portion (25) at the edge is pressed downward by the pressing punch (60). Thereby, the build-up portion (25) of the both side walls (20) is pushed downward, and the material (meat) outside the both side walls (20) plastically flows downward, so that both lower end sides of the both side walls (20) The outer side of the part, that is, the outer side of the corner part of the connecting wall (30) and the both side walls (20) is filled with the material to form the meat filling part (26).

  In addition, the lower end corner part of both side walls (20) is shape | molded from a circular arc shape to a right-angled shape by forming the meat filling part (26). Furthermore, the upper end surface of the both side walls (20) in the second intermediate product (2) is formed as a flat surface.

  Moreover, in the process of forming the meat filling part (26) of this embodiment, the rocker of both the side walls (20) on one end side and the connection wall (30) in the first intermediate product (1) as in the above bending process. A pressing punch (60) is driven in a state where both sides in the arm length direction (both front and rear sides) are restrained by a fixed mold (not shown).

  In this embodiment, a 2nd process is comprised by the process of forming the meat filling part (26).

  Here, in the bending step (first step), as shown in FIG. 1A, the inclination angle (θ) of the inclined surface (23) with respect to the inner side surface of the both side walls (20) is 22 ° to 38 °, The angle is preferably set to 25 ° to 35 °, more preferably 27 ° to 33 °. That is, when the inclination angle (θ) of the inclined surface (23) is set within the above specific range, the meat filling portion (26) can be formed accurately and accurately. In other words, if the inclination angle (θ) of the inclined surface (23) is too large, the build-up portion (25) becomes small, and it may be difficult to reliably form the meat filling portion (26) described later. . On the other hand, when the inclination angle (θ) is too small, in order to sufficiently secure the built-up portion (25), it is necessary to lengthen the inclined surface (23), which may be difficult to process. .

  The ratio (T2 / T1) of the length (T2) of the inclined surface (23) to the thickness (T1) of the side walls (20) is 4/5 to 2/3, more preferably 3/4. It is good to set to ~ 2/3. That is, when the ratio (T2 / T1) of the inclined surface (23) in the plate thickness direction is set within the specific range, the formation of the meat filling portion (26) can be performed accurately and accurately. In other words, if the ratio (T2 / T1) of the inclined surface (23) in the plate thickness direction is too large, the build-up portion (25) becomes small, and it is difficult to reliably form the meat filling portion (26) described later. There is a risk of becoming. On the contrary, if the ratio (T2 / T1) in the plate thickness direction is too small, the build-up portion (25) becomes thick, and the processing (second step) when crushing the build-up portion (25) may be difficult. Is not preferable.

  Furthermore, the ratio (H2 / H1) of the height direction length (H2) of the inclined surface (23) to the inner surface height (H1) of both side walls (20) is 1/3 to 1/2, more preferably 1. It is better to set to /2.5 to 1 / 2.3. That is, when the ratio (H2 / H1) of the inclined surface (23) in the height direction is set within the specific range, the meat filling portion (26) can be formed accurately and accurately. In other words, if the ratio (H2 / H1) in the height direction of the inclined surface (23) is too long, the build-up portion (25) becomes long, and the stroke for crushing the build-up portion (25) becomes long. , Processing may be difficult. Conversely, if the ratio in the height direction (H2 / H1) is too short, the build-up portion (25) becomes thick and short, which may make it difficult to reliably form the meat filling portion (26). Absent.

  After the production of the second intermediate product (2), the first intermediate product (2) having the rough molding wall portions (27) on both sides of the one end side connection wall (30) is formed by press molding as shown in FIG. 1 (c) and FIGS. Three intermediate products (3) are produced.

  That is, a cutting punch (71) is formed on both sides of the tip, and a V-groove (72) is formed between the both cutting protrusions (71). 70) is prepared. As will be described in detail later, the width (S2) of the cutting punch (70) is formed larger than the interval (S1) between the side walls (20).

  The lower surface of the connecting wall (30) in a state where the inner and outer surfaces of the both side walls (20) on one end side of the second intermediate product (2) and the upper surface of the connecting wall (30) are constrained by the fixed mold (75). On the side, a cutting punch (70) is driven from the lower side, and the inside of the meat filling part (26) on both sides of the lower surface of the connecting wall (30) is cut by the cutting protrusion (71). . As a result, the intermediate portion of the connecting wall (30) is recessed upward, and the meat filling portions (26) on both sides protrude relatively downward, so that the meat filling portions (26) on both sides become rough forming walls. Part (27) is formed.

  In this embodiment, the outer surface of the rough molding wall part (27) and the outer surface of both side walls (20) are formed on the same plane (the same plane).

  Moreover, in the notch process which forms the rough shaping | molding wall part (27) of this embodiment, both the side wall (20) and the connection wall (1) of the one end side in a 2nd intermediate product (2) like the said 1st, 2 processes. On both sides (front and rear sides) of the rocker arm length direction 30), the cutting punch (70) is driven in a state of being restrained by a fixed mold (not shown).

  In this embodiment, a 3rd process is comprised by the cutting process which forms the rough shaping | molding wall part (27).

  After producing the third intermediate product (3), as shown in FIGS. 1 (d) and 12, finish processing is performed by press molding to produce the rocker arm (10).

  That is, a finishing punch (80) corresponding to the outer surface shape of the valve stem abutting surface (30a) between the valve stem guide wall (35) and the guide wall (35) is prepared. The lower surface of the connecting wall (30) in a state where the inner and outer surfaces of both side walls (20) on one end of the third intermediate product (3) and the upper surface of the connecting wall (30) are constrained by the fixed mold (85). On the side, a finishing punch (70) is driven from the lower side to finish the rough forming wall portion (27) as a valve stem guide wall (35), and the valve stem guide wall ( 35) is finished as a valve stem contact surface (30a).

  As a result, as shown in FIGS. 1D and 2, a rocker arm (10) having one end formed in a desired shape (H-shaped cross section) is produced.

  In the step of finishing the valve stem guide wall (35) of the present embodiment, both the side walls (20) on one end side and the connecting wall (30) in the third intermediate product (3), as in the first to third steps. The finishing punch (80) is driven in both sides (both front and rear sides) in the rocker arm length direction of) in a state of being constituted by a fixed mold (not shown).

  In the present embodiment, the fourth step is constituted by the step of performing the finishing process.

  As described above, according to the method for manufacturing a rocker arm of the present embodiment, the embedding portion (25) formed on the outer side of the upper edge of the both side walls (20) is driven from above with the pressing punch (60). Then, the material on the outside of the both side walls (20) is plastically flowed downward to form the meat filling portions (26) on both sides at the lower end of the both side walls (20), and then the punch for cutting (70 ) And the finishing punch (80) to form the meat filling portion (26) as the valve stem guide wall (35), the pressing direction is specified in the vertical direction. Therefore, processing can be performed smoothly, the processing speed can be improved, and productivity can be improved.

  Furthermore, in the present embodiment, since the mold only needs to be movable in the vertical direction, production facilities such as a die set can be simplified, reduced in size and weight, and cost can be reduced.

  Moreover, in this embodiment, since the inner side of the build-up part (25) is formed in the inclined surface (23) which becomes high gradually as it goes outside, the meat | flesh at the time of pushing down the build-up part (25) downward The amount of fluid increases at the outer side than at the inner side, and the meat filling portion (26) can be reliably formed on the outer side of the both side portions of the lower end of the both side walls (20). Accordingly, the processing accuracy is improved, and the quality of the rocker arm (10) as a manufactured product can be improved.

  In this embodiment, the cutting punch (70) and the finishing punch (80) are driven from the lower side of the connecting wall (30), and the valve stem guide walls (35) are formed on both sides of the connecting wall (30). Compared to the conventional manufacturing method in which the valve stem guide walls are pushed inward from both sides, the interval between the valve stem guide walls (35) is not limited and is not restricted. The distance between the walls (35) and the size of the valve stem contact surface (30a) between the guide walls can be freely adjusted. Therefore, the degree of freedom in design increases and versatility can be improved.

  Further, in the present embodiment, the flat blank product (11) is bent, and at the same time, the inner side of the upper end edges of the side walls (20) is subjected to an imposition process to form the built-up portion (25). Therefore, the number of processes can be reduced compared to the case where the bending process and the imposition process are performed separately, and the production efficiency can be improved and the cost can be reduced.

  Further, in the present embodiment, as shown in FIG. 11, from one cutting protrusion (71) to the other cutting protrusion (71) in the cutting punch (70) used in the third step. (Punch width S2) is set to be larger than the interval (S1) between the side walls (20), so that cracking occurs when cutting is performed by the cutting punch (70). It can be effectively prevented.

  That is, if the width (S2) of the cutting punch (70) is set equal to the interval (S1) between the side walls (20), the cutting position by the cutting punch (70) and the both side walls (20) Therefore, when the cutting punch (70) is driven, shear stress concentrates on the portion corresponding to the cutting position of the connecting wall (30), and a crack may occur. is there.

  When the width (S2) of the cutting punch (70) is set to be smaller than the interval (S1) between the side walls (20), the cutting position and the inner side surface position of the side walls (20) coincide. Therefore, although the occurrence of cracks due to concentration of shear stress can be prevented, the dimension between the incision positions, that is, the width between the valve stem guide walls (35) becomes narrow, and a sufficiently large valve stem contact surface (30a ) May be difficult to secure.

  On the other hand, in this embodiment, since the width (S2) of the cutting punch (70) is set larger than the interval (S1) between the side walls (20), the occurrence of cracks due to the concentration of shear stress. The width between the valve stem guide walls (35) can be widened, and a sufficiently large valve stem contact surface (30a) can be formed, producing a high quality rocker arm (10). can do.

  Specifically, the ratio (S2 / S1) of the width (S2) of the cutting punch (70) to the interval (S1) between the side walls (20) is 1.1 to 1.5, preferably 1.2 to 1. .4 should be set.

  Furthermore, in this embodiment, at the time of bending as the first step, the work (upper edge of both side walls) is clamped between the inner surface of the fixed mold (55) and the imposition portion (52) of the punch (50). Since the inclined surface (23) is formed while the upper edges of both side walls are extended without difficulty, for example, in the state of a flat steel plate, the corner portion is simply crushed to form the inclined surface. In comparison, the formation of the inclined surface (23), that is, the formation of the built-up portion (25) can be performed smoothly, and the production efficiency can be further improved.

  In the present embodiment, a bending / imposition process (first process) for manufacturing the first intermediate product (1), a meat filling part forming process (second process) for manufacturing the second intermediate product (2), When the third intermediate product (3) is manufactured (third step) and the finishing step (fourth step), the connecting wall (30) on one end side and both side walls of the intermediate products (1) to (3) (20) Since both sides (front and rear sides) of the rocker arm length direction of the connecting wall are constrained, the material can be prevented from flowing in the front-rear direction when the punch is driven, and the material can be accurately flowed in the vertical direction. be able to. Accordingly, the molding process can be performed accurately and accurately, and the quality of the rocker arm (10) as a manufactured product can be further improved.

  In the above embodiment, the bending process and the imposition process are performed simultaneously. However, the present invention is not limited to this, and in the present invention, the bending process and the imposition process may be performed separately. .

In the manufacturing method of one Embodiment of this invention, it is a front view of the valve stem contact | abutting side edge part in the intermediate product for every process stage, Comprising: The figure (a) is a front view just after a bending process, The figure (b) The front view immediately after formation of the meat filling portion, FIG. 6C is a front view immediately after the cutting process, and FIG. It is a perspective view which shows the rocker arm obtained by the manufacturing method of embodiment. It is a perspective view which shows the flat blank product as a product in the middle of the manufacturing method of embodiment. It is a perspective view which shows the flat blank product with a hole as a product in the middle of the manufacturing method of embodiment. It is a perspective view which shows the intermediate product immediately after the bending process of embodiment. It is front sectional drawing which shows the valve stem contact side edge part of the intermediate product in the bending process of embodiment. It is front sectional drawing which expands and shows the principal part of the valve stem contact side edge part of the intermediate product in the bending process of embodiment. It is front sectional drawing which expands and shows the principal part of the valve stem contact side edge part of the intermediate product during formation of the meat filling part of embodiment. It is front sectional drawing which shows the valve stem contact | abutting side edge part of the intermediate product in the incision process of embodiment. It is front sectional drawing which expands and shows the principal part of the valve stem contact side edge part of the intermediate product in the cutting process of embodiment. It is front sectional drawing which shows the valve stem contact side edge part of the intermediate product immediately after the incision process of embodiment. It is front sectional drawing which expands and shows the principal part of the valve stem contact side edge part of the intermediate product in the finishing process of embodiment.

Explanation of symbols

1-3. First to third intermediate products 10 ... Rocker arms 11, 12 ... Flat blank products (flat products)
20 ... Both side walls 22 ... Inner corner part 23 ... Inclined surface 25 ... Overlaying part 26 ... Meat filling part 27 ... Rough forming wall part 30 ... One end side connection wall 30a ... Valve stem contact surface 35 ... Valve stem guide wall 60 ... Indentation punch (Indentation type)
70 ... Punch for cutting (cutting type)
80 ... Finishing punch (finishing mold)

Claims (5)

Both side walls extending in a predetermined direction and arranged in parallel, and one end side connecting walls that connect lower portions on one end side in the longitudinal direction of both side walls, projecting upward at the outer side at the upper edge of the both side walls A first step of obtaining a first intermediate product provided with a built-up portion in
By pushing the build-up portion of the first intermediate product downward with a pressing mold and causing the outer portions of both side walls to plastically flow downward, the meat filling portions are respectively formed on the outer sides of the lower end side portions of the both side walls. A second step of obtaining a second intermediate product;
A third intermediate product in which the meat filling portions on both sides are respectively formed on the rough forming wall portion by cutting the inside of the meat filling portion on both sides of the one end side connecting wall of the second intermediate product from the lower side by a cutting die. A third step of obtaining
By forming the one end side connecting wall of the third intermediate product with a finishing die, the rough forming wall portions on both sides are formed on the valve stem guide wall, and the valve stem contact surface is formed between the valve stem guide walls. And a fourth step of obtaining a formed rocker arm.   The method for manufacturing a rocker arm according to claim 1, wherein an inclined surface that gradually increases toward the outside is formed on the inner side of the built-up portion at the upper edge of both side walls of the first intermediate product. In the first step, the flat plate product is bent into a U shape to form both side walls on both sides of the one end side connecting wall, and the upper end edges of the both side walls are constrained on the outer side surfaces of the both side walls. And pressing the inner corner part in to project the outer part upwardly projecting to form the build-up part, and
The rocker arm manufacturing method according to claim 1 or 2, wherein the bending step and the imposition step are performed simultaneously.   The method for manufacturing a rocker arm according to any one of claims 1 to 3, wherein a width of the cutting die is set larger than a distance between the side walls.   5. The method according to claim 1, wherein at least one of the first to fourth steps is performed while restraining both sides in the longitudinal direction of the rocker arm on the one end side connecting wall and the both side walls. Method of manufacturing rocker arm.

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