JP4431488B2 - 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.

  FIG. 10 is a cross-sectional view showing a valve mechanism in an internal combustion engine such as a vehicle. As shown in the figure, in this valve operating mechanism, the rotational movement of the cam (3) rotating in conjunction with the crankshaft (2) is applied to the valve stem (5) in the valve (4) such as an intake valve or an exhaust valve. Is provided with a rocker arm (1) for reciprocal movement.

  As shown in FIGS. 10 and 11, the rocker arm (1) includes a pair of side walls (1a) arranged in parallel and a connecting wall (1b) for connecting one end side and the other end side between the side walls. ) (1c), provided on the connecting wall (1b) on one end side, provided on the valve stem abutting portion (1d) contacting the valve stem (5), and on the connecting wall (1c) on the other end side, And a pivot engaging portion (1e) that engages with a pivot portion (6) fixed to the cylinder head. Further, the both side walls (1a) of the rocker arm (1) are provided with shaft fixing holes (1f) coaxially with each other. The shaft fixing holes (1f) are provided with support shafts (8) for the rollers (7). ) Is fixed, and the roller (7) and the cam (3) can be brought into rolling contact.

  Such a rocker arm (1) has been conventionally manufactured by forging or precision casting (lost wax). However, in recent years, as the internal combustion engine has increased in speed and output, to reduce the inertia weight, In order to reduce the weight of the rocker arm, many techniques for manufacturing the rocker arm by press working have been proposed.

  In the method of forming a rocker arm by press working, as a method for forming the shaft fixing hole (1f), generally, cutting with a drill or the like, and press punching by punching a punch for punching are employed.

  However, since cutting is less efficient than press working, the production efficiency is reduced and the cost is increased. In addition, there is a concern about adverse effects due to chips generated during cutting.

  In addition, although the press punching method can be expected to improve production efficiency, it cannot secure sufficient smoothness of the punched hole inner peripheral surface, for example, it is difficult to ensure a sufficiently wide shear surface on the hole inner peripheral surface. Thus, the hole inner peripheral surface cannot be sufficiently brought into surface contact with the support shaft (8), and the shaft holding force may be reduced.

  Therefore, as shown in Patent Documents 1 and 2 below, the applicant of the present application drives a punch for punching from both sides into both side walls of a bent product obtained by bending a flank product into a U shape. A manufacturing method has been developed in which a shaft fixing hole (1f) is formed by smoothing the inner peripheral surface of the hole by driving a shaving punch from both sides into the prepared holes on both sides and performing shaving.

In this manufacturing method, since the shaft fixing hole (1f) is formed only by pressing with a punch for punching and a shaving punch, high productivity can be obtained, and the inner peripheral surface of the hole can be obtained by shaving. Can be finished smoothly, and sufficient shaft holding force can be secured.
Japanese Patent No. 3497368 Japanese Patent No. 3582977

  By the way, in the manufacturing method of the rocker arm shown in the above-mentioned Patent Documents 1 and 2, since a punch for punching and a punch for shaving are driven from both sides of the workpiece, the scraps and shavings are removed from the die placed inside the workpiece. Remains. To remove this debris, a special operation such as removing the debris by opening the die hole by relatively moving the punch and die after removing the work is required. A lot of time is spent on the operation, the processing time becomes long, and it is difficult to further improve the production efficiency.

  An object of the present invention is to provide a method for manufacturing a rocker arm that can solve the above-described problems of the prior art and further improve the production efficiency.

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

[1] A step of obtaining a flat plate product with a pilot hole having a pilot hole for a roller support shaft fixing hole;
The flat plate-like product with the lower hole is bent to have a pair of side walls arranged in parallel and a connecting wall connecting the both side walls, and the lower hole is arranged on the pair of both side walls. Obtaining a bent product with prepared holes;
A sizing punch having a tapered push-opening portion at the distal end, the proximal end side of the push-opening portion having a larger diameter than the lower hole, and the distal end having a smaller diameter than the lower hole. And a step of plastically flowing the inner peripheral portion of the lower hole by the push-opening portion to finish the inner peripheral surface and forming a roller support shaft fixing hole.

[2] The step of forming the roller support shaft fixing hole includes:
The sizing punches are arranged on the outer side walls of the bent product with the prepared holes so as to face each other on the same axis, respectively.
2. The method for manufacturing a rocker arm according to claim 1, wherein the sizing punches on both sides are simultaneously penetrated into the lower holes on both side walls to finish the lower holes on both sides simultaneously.

[3] The sizing punch is formed such that an outer peripheral surface of the push-open portion is a tapered working surface,
3. The method for manufacturing a rocker arm according to item 1 or 2, wherein an inclination angle of the working surface with respect to the axis is set to 10 to 50 ° on one side.

[4] In the step of forming the roller support shaft fixing hole,
4. The method for producing a rocker arm according to any one of items 1 to 3, wherein the inner peripheral portion of the lower hole is plastically flowed from the shear region of the lower hole to the fracture region.

  [5] A rocker arm manufactured by the manufacturing method according to any one of items 1 to 4.

  [6] The rocker arm according to [5], wherein a smooth surface in a wider range than the shear surface of the lower hole is provided on the inner peripheral surface of the shaft fixing hole.

  According to the manufacturing method of the rocker arm of the invention [1], since it can be manufactured only by pressing such as punching, bending, and sizing, high productivity can be obtained and the inner peripheral surface of the hole can be obtained by sizing. Smooth finishing can be achieved and sufficient shaft holding force can be secured.

  Further, in the present invention, the drilling of the prepared hole is performed on a flat product such as a blank product, so that the removal process of the punched residue can be performed by a normal press operation without requiring a special operation. In addition, since the sizing punch is inserted into the lower hole and the lower hole is finished by plastic working, it is possible to prevent the occurrence of shavings during the machining. In this way, in the drilling process and the pilot hole finishing process, no special operation by special debris removal is required, and the process can be performed smoothly and the productivity can be improved. In particular, in the present invention, no special operation is required in all other processes, including drilling and pilot hole finishing, and it can be performed by normal pressing. A press machine can be constructed, automation in a series of press processes from blanking to hole finishing can be achieved, and productivity can be significantly improved.

  Furthermore, since the present invention finishes the inner peripheral surface by plastic processing of the inner peripheral portion of the lower hole by penetrating the sizing punch into the lower hole, the load applied to the punch as compared with the case of driving the shaving punch Can be reduced, and early wear deterioration can be prevented. Therefore, it is possible to extend the punch life, reduce maintenance and inspection work, and reduce running costs.

  Further, since no scraps such as scraps are generated during the finishing process of the prepared hole, it is possible to reliably prevent defects due to the generation or scattering of scraps such as the generation of scratches due to the adhesion of the scraps.

  In the present invention, when the flat plate product is bent after the formation of the lower hole, the lower hole may be misaligned. Even if this misalignment occurs, the sizing punch is inserted into the lower hole. As a result, the hole position can be corrected simultaneously with the finishing of the prepared hole, and high positional accuracy can be maintained.

  According to the rocker arm manufacturing method of the invention [2], the positional deviation between the pilot holes on both sides can be reliably corrected, the phase difference can be eliminated, and the positional accuracy of the pilot holes can be further improved. . In addition, since the pressure from the sizing punch is equally applied to the bent product from both sides, it is possible to reliably prevent defects that cause harmful deformation due to the punch driving pressure, and to achieve high quality. Can be maintained.

  According to the method for manufacturing a rocker arm of the invention [3], the plastic flow of the inner peripheral portion of the lower hole can be performed more smoothly, and the above effect can be obtained more reliably.

  According to the method for manufacturing a rocker arm of the invention [4], the smooth surface on the inner peripheral surface of the shaft fixing hole can be secured more widely, and the shaft holding force can be further improved.

  According to the inventions [5] and [6], it is possible to provide a rocker arm having the above effects.

  Hereinafter, the manufacturing method of the rocker arm which is an embodiment of the present invention is explained in detail based on a drawing.

  In this production method, first, as shown in FIG. 1A, a predetermined area of a steel plate as an original plate is punched out to obtain a flat blank product (11) having a shape in which both sides protrude in an arc shape.

  Next, as shown in FIG. 1 (b), a punch for punching is punched into the flat blank product (11) to punch out an intermediate region of the flat blank product (11) to form a drum-shaped central hole ( 15) and punching out predetermined regions on both sides to form circular prepared holes (21), respectively, to obtain a flat blank product (12) with prepared holes.

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

  The blanking process for punching the original plate, the drilling process for the central hole (15), the drilling process for the lower hole (21), 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.

  When a chamfered portion is formed on the peripheral edge of the opening end of the lower hole (21), a surface pressing portion is provided on the outer periphery of the base end side of the punch for forming the lower hole, At the same time, the chamfered portion may be formed by pushing the opening peripheral edge portion of the lower hole with the surface pressing portion.

  Next, as shown in FIG. 1 (c), a bent product (13) with a pilot hole is formed by bending the flat blank product (12) with a pilot hole into a U-shape (reverse U-shape). obtain.

  This bent product (13) has a pair of side walls (20) parallel to each other and one end side connecting wall (as a valve stem abutting portion) that connects between the upper ends of one end portions of both side walls (20). 30) and the other end side connection wall (40) which connects between the upper ends of the other end portions of both side walls (20) and has a pivot engaging recess (41).

  Next, on both side walls (20) of the bent product (13) thus obtained, a sizing device (50) described in detail below is used to finish the lower hole (21), and the roller support shaft fixing hole (25). ).

  As shown in FIG. 2, the sizing apparatus (50) has a base (51) on which the width corresponds to the width between the side walls of the bent product (13). There is provided a sizing die (52) set to. The die (52) is configured such that the folded product (13) can be installed by fitting the folded product (13) so that both side walls (20) are arranged on both sides.

  In the sizing die (52), punch through holes (53) are formed in the width direction (down hole axial direction) corresponding to the lower holes (21) in the both side walls (21) of the bent product (13). It is formed to penetrate.

  In the sizing apparatus (50), a punch support base (55) is disposed on both sides of the base (51), and a sizing punch (60) is provided on each punch support base (55). It is slidably supported along the axial direction via (57). Both punches (60) are arranged in a state in which their axial centers coincide with the through holes (53) of the sizing die (52).

  Further, on both sides of the punch support base (55), an elevating drive body (58) that can be driven up and down is disposed. A cam surface (58a) provided on the lower end side of the elevating drive body (58), and a punch A cam surface (57a) provided on the base end side of the support member (57) is slidably disposed. Then, when the lifting drive bodies (58) on both sides are lowered, both sizing punches (60) are advanced along the axial direction and inserted into the die hole (53) of the sizing die (52) from both sides. It is comprised so that.

  As shown in FIG. 3, the sizing punch (60) used in the present embodiment is provided with a push-open portion (61) formed in a tapered shape at the tip. The push-out portion (61) has a distal end (62) having a smaller diameter than the lower hole (21) and a proximal end (63) having a larger diameter than the lower hole (21). The outer peripheral surface is formed as a tapered working surface (61a).

  Further, the base end side portion of the punch (60) with respect to the push-open portion (61) is formed as a hole finishing portion (65) having the same outer diameter as that of a shaft fixing hole (25) described later. .

  In order to perform the finishing process on the prepared hole (21) of the bent product (13) by the sizing apparatus (50) having the above-described configuration, as described above, the sizing die (52 ), The lift drive bodies (58) on both sides are simultaneously lowered and both punches (60) are advanced. As a result, both punches (60) penetrate the both lower holes (21), and the inner peripheral surface of the hole is finished to form the shaft fixing hole (25).

  Here, the behavior of the inner peripheral portion of the lower hole when the sizing punch (60) is driven into the lower hole (21) will be described in detail. First, in the state before the sizing finish on the inner peripheral surface of the lower hole (21), a smooth shear region (22a) is formed on the insertion side (one end side) of the punch for punching as shown in FIGS. At the same time, a rough fracture region (22b) is formed on the punch exit side (the other end side) that is wider in the outer diameter direction than the shear surface region (22a). A chamfered portion (21a) is formed on the opening peripheral edge portion on one end side of the lower hole (21).

  When the sizing punch (60) is advanced into the prepared hole (21) in this state, the punch (60) is first inserted into the prepared hole (21) as shown in FIG. 60), the portion (meat) of the shear region (22a) in the inner periphery of the lower hole is pushed in by the push-opening portion acting surface (61a). As shown in FIG. 6 (b), the portion (inner peripheral portion) of the shear region (22a) undergoes plastic flow by the pressing, and the plastic flow portion (23) becomes as shown in FIG. 6 (c) and FIG. It moves to the fracture | rupture area | region (22b) in a pilot hole inner peripheral surface. Further, when the finishing portion (65) of the punch (60) passes through the lower hole (21), the outer peripheral surface (finishing surface 65a) of the finishing portion (65) is changed from one end side to the other end side on the inner peripheral surface of the lower hole. A wide portion is then finished to a smooth surface to form the shaft fixing hole (25).

  Thus, by finishing the lower hole (21) by plastic flow of the meat in the inner peripheral portion of the hole, a wide range of smooth surfaces is formed on the inner peripheral surface of the shaft fixing hole (25).

  Before sizing, for example, as shown in FIG. 7, even if the axial centers (L) do not coincide with each other in the lower holes (21) on both sides of the bent product (13), there is a sizing. When the sizing punches (60) are pierced from both sides by machining, the hole positions on both sides are corrected as shown in FIG. 8, and the shaft fixing holes (25) on both sides are aligned with each other's axis (L). Arranged to match exactly.

  After the sizing process is completed, a process such as a grooving process of the valve stem contact groove is performed to manufacture the rocker arm (10).

  As described above, according to the method of manufacturing the rocker arm of the present embodiment, only the punching process such as outer diameter punching and punching, bending process, and pressing process such as sizing process are used. Therefore, there is no need to perform any machining such as low-efficiency reamer processing or cutting, thereby improving production efficiency and reducing costs.

  Since the shaft fixing hole (25) is formed by sizing the lower hole (21), a wide range of smooth surfaces is formed on the inner peripheral surface of the shaft fixing hole (25). Therefore, the hole inner peripheral surface can be brought into surface contact with the support shaft in a wide range, and a sufficient shaft holding force can be obtained.

  Furthermore, in this embodiment, the sizing punch (60) penetrates the lower hole (21) to plastically flow the inner peripheral portion of the lower hole to finish the shaft fixing hole (25). In other words, since the inner peripheral surface of the lower hole is plastically processed by the working surface (61a) of the punch (60), the sizing is different from that in which the inner peripheral portion of the hole is scraped off by a sharp edge portion such as a shaving punch. A large load is not concentrated on the working surface (61a) of the punch (60) and the service life can be greatly increased. Accordingly, it is possible to reduce the number of punch replacement operations, and not only greatly reduce the running cost, but also reduce the burden of maintenance and inspection operations, so that maintenance can be easily performed.

  Here, in this embodiment, the correction allowance (the amount of plastic flow) of the prepared hole (21) will be described. The margin for correction of the lower hole (21) corresponds to the difference in diameter with respect to the punch for forming the lower hole in the sizing punch (60). As shown in FIG. ).

  In this embodiment, the one-side diameter expansion amount (X) is set to 1 to 10%, more preferably 5 to 10%, with respect to the wall thickness (T) of the side wall (21) of the rocker arm (10). Is good. That is, when this amount of diameter expansion is set within the above range, the amount of plastic flow in the hole inner periphery during sizing can be adjusted to an appropriate amount, and a desired wide smooth surface can be formed on the inner surface of the finished hole. And a sufficient shaft holding force can be obtained.

  In other words, when the amount of diameter expansion (X) is too small, the plastic flow amount in the hole inner peripheral portion is reduced, and the fracture region (22b) remains largely, and a wide smooth surface is formed on the hole inner peripheral surface. It cannot be formed, and it may be difficult to obtain a sufficient shaft holding force. When the diameter expansion amount (X) is too large, the plastic flow amount increases, and the plastic flow portion bulges on the inner surface of both side walls of the rocker arm (10) and bulges in both side walls (21). There is a risk that problems such as contact with a roller installed on the machine may occur.

  In the present embodiment, the inclination angle (θ) of the action surface (61a) of the outer peripheral surface of the push-out portion in the sizing punch (60) is set to 10 to 50 ° (10 to 50 ° on one side) with respect to the axis. It is good to set it at 12-40 °, more preferably 15-30 °.

  That is, when this inclination angle (θ) is set within the above range, the plastic flow in the inner periphery of the hole can be performed reliably and smoothly, and a desired hole finishing process can be performed.

  In other words, when the inclination angle (θ) is set to be excessively large, the plastic flow of the inner peripheral portion of the hole cannot be reliably performed, and shearing or fracture occurs, and a desired finishing process can be performed. There is a fear that it cannot be done. On the other hand, if the inclination angle (θ) is set too small, the axial length of the working surface (61a) becomes excessively long, and there is a risk that problems such as the need to increase the punch stroke may occur.

  On the other hand, in the manufacturing method of the present embodiment, when finishing the shaft fixing hole (25), the sizing punch (60) is pushed through the lower hole (21) to finish the inner peripheral surface of the lower hole by plastic flow of meat. Therefore, unlike the case where, for example, a shaving punch is driven and the inner peripheral surface of the prepared hole is scraped off, no shavings are generated. Therefore, it is not necessary to remove the scraps and the like in the die hole (53) of the sizing die (52) after passing through the sizing punch (60), so that the waste removal step can be omitted, and the work is further increased accordingly. Can be improved.

  In particular, as shown in the above-mentioned conventional Patent Documents 1 and 2 (Patent Nos. 3558277 and 3558277), the press work that requires scrap removal such as a shaving punch and a punch for punching from both sides of the work is low-efficiency. It is difficult to expect improvement in production efficiency. That is, in press working that requires removal of debris, special operations such as removing the debris by opening the die hole by relatively moving the punch and die to remove the shaving residue remaining in the die. Although necessary, a lot of time is spent on special operations such as die movement, so that the processing time becomes long. For this reason, when pressing with special operations following press operations with normal operations such as bending and flat plate punching, the work is stagnated in press processing with special operations, so both press processing must be performed continuously. Is difficult. Therefore, it is not possible to construct a transfer press machine by combining press working with special operation and press working in normal operation, which may cause a reduction in production efficiency. Furthermore, a special structure is required for performing a special operation, and the cost may increase accordingly.

  On the other hand, in the manufacturing method of this embodiment, the sizing process does not generate a scrap by simply passing the sizing punch (60) through the prepared hole (21) of the bent product (13). There is no need to remove it. Therefore, in this embodiment, since it can be configured only by a normal operation press work that does not require a special operation such as moving the die for debris removal, it is possible to construct a transfer press machine that links all the press work, Automation in a series of press processing from blank processing to hole finishing can be achieved, and productivity can be significantly improved. Further, it is not necessary to perform a special operation, a special structure for performing the operation is unnecessary, and the cost can be reduced.

  For reference, in the shaving process in which punches are driven from both sides as shown in Patent Documents 1 and 2, the processing capability (processing speed) is about 10 per minute, whereas in the sizing process of this embodiment, 1 A processing capability of about 60 pieces per minute can be obtained, and a processing capability comparable to that of normal press processing that does not require special operations such as debris removal can be obtained.

  Further, in the sizing process, the sizing punches (60) on both sides coaxially disposed in the both side lower holes (21) of the bent product (13) are simultaneously penetrated to finish the lower holes (21) simultaneously on both sides. Therefore, the finishing holes (shaft fixing holes 25) on both sides can be accurately arranged on the same axis, and the quality can be further improved. In particular, when the flat blank product (12) is bent after the formation of the lower hole as in this embodiment, the axis (L) of the lower holes (21) on both sides does not exactly match as shown in FIG. Although there may be some positional deviation, even if this positional deviation occurs, the hole position can be corrected simultaneously with plastic working by penetrating the sizing punch (60) from both sides as shown in FIG. The shaft fixing holes (25) on both sides can be arranged on the same axis with the axial centers (L) accurately aligned with each other, and high positional accuracy can be obtained.

  In addition, in this embodiment, since the pressure when penetrating the sizing punch (60) is equally applied from both sides to the folded product (13), harmful deformation occurs due to the punch driving pressure. Such problems can be reliably prevented, and high quality can be maintained.

  In the above-described embodiment, the chamfer surface (C surface) -shaped sizing punch (60) in which the action surface (61a) is formed in a linear cross section is used. However, the present invention is not limited to this. As shown in FIG. 9 (a), a sizing punch (60) having an R surface shape in which the working surface (61a) is formed in an arcuate cross section may be used. A sizing punch formed by a composite surface such as the above may be used.

  Further, in the present invention, in order to reduce the contact pressure between the punch and the inner peripheral surface of the hole when the sizing punch is pierced, as shown in FIG. A sizing punch (60) having a small (rear side) diameter may be used.

<Example 1>
A bent product (13) with a pilot hole was produced based on the manufacturing method of the rocker arm of the above embodiment. The side wall plate thickness (wall thickness) of the bent product (13) is 3.2 mm, and the diameter of the lower hole (21) (outer diameter of the punch for punching) is 8.40 mm. In the bent product (13), about 50% of the inner peripheral surface of the lower hole (21) along the axial direction was a shear region, and the remaining region was a fracture region.

  Next, this bent product (13) was finished with the inner peripheral surface of the lower hole (13) by using the same sizing apparatus (50) as in the above embodiment to form the shaft fixing hole (25). At this time, as the sizing punch (60), the outer diameter of the finishing portion (65) (diameter of the shaft fixing hole) is 8.70 mm, the one-side diameter expansion amount with respect to the wall thickness is 9%, and the outer peripheral surface of the expanded portion (working surface) 61a) having an inclination angle (θ) of 46 ° was used.

  When the size of the smooth region of the inner peripheral surface of the shaft fixing hole in the rocker arm (10) obtained in this way was measured, 80% of the region along the axial direction could be secured as the smooth region.

<Example 2>
Side wall plate thickness 4.0mm, pilot hole diameter 9.0mm, 40% of the inner peripheral surface of the lower hole is 5% on one side of the expanded product (13) with the lower hole in the shear region, outer peripheral surface of the expanded portion A rocker arm was produced in the same manner as described above except that a sizing punch (60) having an inclination angle (θ) of (61a) of 38 ° was used.

  In this rocker arm, 75% of the inner peripheral surface of the shaft fixing hole could be secured as a smooth region.

<Example 3>
Side wall plate thickness 2.3 mm, pilot hole diameter 7.1 mm, 50% of the inner peripheral surface of the lower hole is 2% larger than the bent product (13) with the lower hole in the shear region, outer peripheral surface of the expanded portion A rocker arm was produced in the same manner as described above except that a sizing punch (60) having an inclination angle (θ) of (61a) of 30 ° was used.

  In this rocker arm, 70% of the inner peripheral surface of the shaft fixing hole could be secured as a smooth region.

It is a perspective view which shows the processed product in each process step in the manufacturing method of the rocker arm which is embodiment of this invention, Comprising: The figure (a) is a perspective view which shows a flat blank product, The figure (b) is bottom. The perspective view which shows the flat blank product with a hole, the figure (c) is a perspective view which shows the bent product with a lower hole, The figure (d) is a perspective view which shows a rocker arm. It is a front view which shows the sizing processing apparatus employ | adopted for the manufacturing method of embodiment. It is sectional drawing which shows the state just before penetrating a sizing punch in a pilot hole in the manufacturing method of embodiment. It is sectional drawing which shows the state immediately after penetrating the sizing punch in the pilot hole in the manufacturing method of embodiment. It is sectional drawing which shows the relationship between a pilot hole and the sizing punch in the manufacturing method of embodiment. It is sectional drawing which shows the state of the inner periphery part of the pilot hole by the sizing process in the manufacturing method of embodiment, Comprising: The same figure (a) is sectional drawing of the state immediately after punch penetration start, The figure (b) is punch punching FIG. 4C is a cross-sectional view immediately after completion of punch penetration. It is sectional drawing which shows the positional relationship of the pilot holes of both sides before the sizing process in the manufacturing method of embodiment. It is sectional drawing which shows the positional relationship of the pilot holes of both sides after the sizing process in the manufacturing method of embodiment. FIG. 4A is a side view showing a sizing punch that can be used as a first modification of the present invention, and FIG. 4B is a side view showing a sizing punch that can be used as a second modification. It is sectional drawing which shows the valve mechanism of the internal combustion engine in a vehicle. It is a figure which shows the conventional rocker arm, Comprising: The figure (a) is sectional drawing, The figure (b) is a top view.

Explanation of symbols

10 ... Rocker arm 12 ... Flat blank product with pilot hole (Flat plate product with pilot hole)
13 ... Folded product with lower hole 20 ... Both side walls 21 ... Lower hole 25 ... Shaft fixing hole 30, 40 ... Connecting wall 60 ... Sizing punch 61 ... Push-out part 65 ... Finishing part

Claims (1)

A step of obtaining a flat plate product with a pilot hole having a pilot hole for a roller support shaft fixing hole by driving a punch for punching;
The flat plate-like product with the lower hole is bent to have a pair of side walls arranged in parallel and a connecting wall connecting the both side walls, and the lower hole is arranged on the pair of both side walls. Obtaining a bent product with a prepared hole;
A sizing punch having a tapered push-opening portion at the distal end, the proximal end side of the push-opening portion having a larger diameter than the lower hole, and the distal end having a smaller diameter than the lower hole. The portion of the shear region in the inner periphery of the lower hole is plastically flowed by the push-out portion, and the plastic flow portion is moved to the fracture region in the inner peripheral portion of the lower hole to finish the inner peripheral surface. , look-containing and forming a roller support shaft fixing hole,
The method for manufacturing a rocker arm, wherein the sizing punch has a one-side diameter expansion amount of 1 to 10% of the thickness of the side wall with respect to the punch for punching .

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