JPH01180728A - Forming method for bossed member - Google Patents

Abstract

PURPOSE:To form the boss member having specified thickness and height by pushing a punch after forming the circumference of a prepd. hole in a truncated conical shape by approaching the punch with pressurizing the prepd. hole between die and plate presser by piercing it on a plate-like blank stock. CONSTITUTION:The plate-like blank stock B piercing a prepd. hole at the center part is set between a die 3 and plate presser 2. It is then pressurized by a hydraulic cylinder 6 toward the center from the plural directions at the outside of the blank stock. A plastic deformation is then started by the lift of the stress near the prepd. hole, propagated in the outside direction of the blank stock B in order and the inner part stress becomes in a balanced state. When a punch 1 is approached to the die 3, it is deformed in the truncated conical shape with the corner round part of the punch 1 and die 3 as a contact point. At the initial stage when this trucated conical part is formed the prepd. hole diameter is changed to a contracting trend and the material of sufficient volume is fed from the circumference to this truncated conical part. Thereafter, with further push-in of the punch 1 the punch 1 is slided at the inner side of the trucated conical part, the spreading formation of the prepd. hole is executed and the boss having specified thickness and height is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a member with a boss, in particular, a method for forming a member with a boss by pressing a boss having a thickness and height sufficient to transmit torque. Concerning a method of molding.

[Prior Art] In general, a member with a boss that can withstand torque transmission has a boss part G on a blank material B having an outer diameter Do and a plate thickness t, as shown in FIG.
(Final outer diameter of the bossed member: D) When forming the boss part G, the thickness tb should be as thick as possible within the thickness of the blank material B, and the height h should be as high as possible. This is often desired. .

This is to ensure the torque resistance strength of splines formed on the boss part G/inner diameter part G, etc. of the bossed member, and to ensure the torque resistance strength of the spline formed on the boss part G/inner diameter part G,
This is to minimize the axial runout in No. 3.

The following methods are known as conventional methods for forming such bossed members.

The first method is the so-called burring process, in which the 1θ
As shown in FIG.
This is a method of enlarging the hole using a punch whose outer diameter is the inner diameter of the boss d2.

However, this method has a hole expansion rate (=((12-d
Since there is a limit value of t)/dt), it is often impossible to obtain a boss portion with both thickness and height that can sufficiently withstand torque transmission.

Therefore, as a second method, as shown in Fig. 1θ (b), the drawing process is repeated several times on the plate blank material B while ensuring an appropriate drawing ratio until the boss inner diameter dimension d2 is obtained (step (1) ) or 7)) to form the ceiling and punch out the ceiling (step (8)), or as a third method, as shown in Figure 10(C), the same method as the second method is used. Drawing process was performed multiple times (steps (1) to 7))
After that, drill a pilot hole with a diameter smaller than the inner diameter of the boss (step (8)).
A method of enlarging the hole (step (9)) is used.

[Problems to be Solved by the Invention] However, in such conventional methods, the first method is not sufficient because there is a limit to the wall thickness and height of the boss portion due to the limit due to the hole expansion rate as described above.

Although the second and third methods can form the boss portion G with a predetermined thickness and height, they require many drawing steps. In other words, since tensile stress is applied to the material during the drawing process, it is important to draw the material while minimizing the reduction in wall thickness caused by this, and it is necessary to set the drawing process with sufficient margin for the drawing limit of the material. It is from.

Performing drawing in multiple stages like this requires a large number of press molds with slightly different mold shapes, which increases the cost of manufacturing the molds and requires multiple steps in the production process, which causes an increase in costs. . Furthermore, unevenness (die marks) in the thickness of the plate were created on the flange due to the multi-step drawing process, which inevitably resulted in a decrease in surface accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a bossed member that eliminates the problems of the conventional methods and can form a bossed member with excellent surface accuracy at low cost.

[Means for Solving the Problems] In order to achieve the above object, in a first embodiment of the present invention, a pilot hole is bored in the center of a metal plate blank, and the plate blank is connected to a die. Place the punch between the presser and the plate presser, apply pressure from the outside to the center of the plate-shaped blank material with the pressurizing means, bring the punch closer to the die, form the area around the lower flame into a truncated conical shape, and then press the punch further. , the boss portion is formed by hole expansion molding.

In addition, in the second embodiment of the present invention, a pilot hole is bored in the center of the metal plate blank material, the plate blank material is set between the outer die and the plate holder, and the outer side of the plate blank material is The punch was brought closer to the die while applying pressure from the center toward the center, forming the area around the prepared hole into a truncated cone shape, and then pushing the punch to expand the hole, and then forming the hole inside the outer die. It is characterized in that the boss portion is formed by pushing the inner die in a direction opposite to the pushing direction of the punch.

[Function] According to the first embodiment of the present invention, first, a plate-shaped blank material with a pilot hole bored in the center is set between a die and a plate holder.

Then, when pressure is applied to the blank material from a plurality of outer directions toward the center by a pressurizing means, the corresponding stress in the vicinity of the pilot hole portion of the blank material increases, causing the region around the pilot hole portion to yield and start plastic deformation. Then, this plastic deformation sequentially propagates toward the outside of the blank material, and the internal stress becomes balanced in a predetermined state corresponding to the inside/outside diameter ratio of the blank material and the pressing force from the outside.

When the punch approaches the die under such a compressive stress field, the area around the prepared hole in the blank material deforms into a truncated conical shape with the rounded corners of the punch and the rounded corners of the die as contact points. Then, the stress state that was balanced under the pilot hole diameter of the initial blank material is
The stress state changes to the same as when a hollow hole corresponding to the size of the rounded corner of the die is virtually created, and the flow of the material, which was balanced near the periphery of the die space, to the truncated cone-shaped part is promoted. Ru.

In the initial process of forming this truncated conical part, the diameter of the initial pilot hole tends to decrease, and a sufficient volume of material is supplied to this truncated conical part from the surrounding area. after that,
As the punch is further pushed in, the rounded corner of the punch slides inside the truncated conical part to enlarge the prepared hole, forming a boss with a predetermined thickness and height, and forming a boss around the boss. is thickened.

According to the second embodiment of the present invention, first, a plate-shaped blank material with a pilot hole bored in the center is set between the outer die and the plate holder.

Then, when pressure is applied by the pressure means from the outer periphery of the blank material toward the center, plastic deformation sequentially propagates toward the outside of the blank material as described in the first embodiment.

When the punch is brought close to the die in this state, since the inner diameter of the die is large, the punch is deformed into a truncated conical shape with a larger bottom diameter than that obtained in the first form.

Then, material flows from the periphery into this truncated conical part more effectively than in the first form.

After that, as the punch is pushed in further, the pilot hole is expanded in the same way, and then, while continuing to apply pressure from the periphery, the inner die provided inside the outer die is moved in the direction in which the punch is pushed. When pushed in the opposite direction, a boss having a predetermined thickness between the outside diameter of the bunch and the inside diameter of the inner die and a height higher than that obtained in the first form is formed, and the area around the boss also increases. thickened.

As described above, according to the present invention, a boss portion having a predetermined thickness and height is formed substantially in the car manufacturing process, and the thickness of the surrounding portion of the boss is increased, thereby reducing costs and improving the surface accuracy of the flange. This makes it possible to obtain a boss-attached member in which the base of the boss is well-reinforced.

[Example 1] Examples of the present invention will be described below with reference to the accompanying drawings.

First, an example of a press mold for carrying out the present invention will be described in the first example.
This will be explained based on the diagram.

1 is a punch and is fixed to a ram (not shown). This punch 1 deforms the blank material B into a truncated cone shape, and has a rounded corner radius rp that contributes to controlling the flow direction of the material and an outer diameter that has the role of determining the inner diameter of the final boss. It has a diameter.

The preferable value is /2≧rp>Dp/3, and punch pressure P is applied to punch 1.

Reference numeral 2 denotes a plate holder, which has a through hole 2A through which the punch 1 passes, and is supported by a ram (not shown) so as to be vertically movable separately from the punch 1 by a pressure mechanism such as a hydraulic cylinder. This effectively transmits the pressurizing force to the vicinity of the central lower hole due to the blank material being pressurized and compressed from the outside, and also prevents buckling of the blank material B while allowing the plate thickness to increase. It has the role of adding pressure PC to a certain extent.

3 is a die fixed on the bed 5 together with the die holder 4, and has a corner radius rd which becomes a bending starting point for the deformation of the blank material B into a truncated conical shape and is a main element for promoting material flow; It has an inner diameter Dd which ultimately plays the role of giving the outer shape of the boss.

The material flow rate is determined by the die corner end dimension Da' (= D
d+2rd), so it is necessary to appropriately determine the diradius d.

It is necessary that this preferable value satisfies rd≧t and is within a range allowed for the final shape of the bossed member.

Similarly, a plurality of hydraulic cylinders 6 are arranged and fixed on the bed 5 at equal intervals radially around the punch 1 for generating the horizontal pressing force Ph, and have a piston 6A. Let Ph be the total horizontal pressing force in multiple directions.

A pressure plate 7 is slidable on the die holder 4, is pressed by the piston 6A, and is movable eight times in the center direction between the temporary presser 2 and the die 3. It can add force.

Note that 8 is a knockout that is movable up and down to hold the positioning nest pin 9 so as to be movable up and down, and also to discharge the molded product.

The pressing force of each of the above-mentioned pressing means is selected appropriately depending on the type of blank material B, etc., but in general, when the punch pressing force PP is 1, the temporary press pressing force PC is 3 to 7, and the total horizontal pressing force Ph It is preferable to set the latter significantly larger at a ratio of 10 to 15.

Next, the process of forming the bossed member will be explained based on FIG. 2.

First, as shown in Figure 2(a), make a pilot hole B0 in the center.
The blank material B having been drilled therein moves upward and its prepared hole B0 is engaged with the nest pin 9 which is in a stationary state. This time is the start of the molding process and is marked as time ○. Next, the blank material B is placed on the die 3 by the downward movement of the knockout 8 and the nest bin 9, and the pressure plate 7 starts moving toward the center at time t1, as shown in FIG. 2(b). The blank material B is positioned by coming into contact with the outer end of the blank material B (time t2). During this time, the punch 1 continues to descend at high speed together with the temporary presser 2, and at time t3, as shown in FIG. Immediately before contact, the lowering speed of the punch 1 is switched to low speed.

At time t4, the blank material B is set between the die 3 and the temporary presser 2 (see FIG. 2(d)).
and FIG. 1(a)) are obtained.

Then, at time t4, high pressure is applied to the hydraulic cylinder 6, and application of a load higher than the compression yield point to the blank material B via the pressure plate 7 is started. While being continuously pressurized by the pressure plate 7, the punch 1 descends at a low speed to contact the blank material B to form a truncated cone, and then continues to descend to form a boss portion. During this time, temporary presser 2
moves upward while applying pressure to absorb the increase in the thickness of the blank material B (the temporary holding stroke shown in the second figure is shown with the tip of the punch 1 as the zero reference).

The forming process of this boss portion is shown in FIG. 1(b), and the forming mechanism will be described later.

The forming of the boss part is completed at time t when the punch 1 reaches the bottom dead center (see FIG. 2(e) and FIG. 1(C)), and after a predetermined time, at t6, the pressurizing plate 7 starts to move backward, then at time t, punch 1 and knockout 8 start moving upward, and at time t8, their speed is increased to discharge the molded product.

Here, the mechanism of forming the boss portion will be explained in detail with reference to FIG.

In FIG. 3(a), the outer diameter d0. Plate thickness t, prepared hole diameter d.

When a horizontal pressing force Ph greater than the compressive yield point is applied from the outer edge of the blank material B toward the center via the pressure plate 7, the pilot hole B of the blank material B is first applied.

The equivalent stress near the hole 80 increases, and the area around the prepared hole 80 yields and starts plastic deformation. Then, this plastic deformation gradually propagates outward while causing work hardening, and the internal stress becomes balanced (see FIG. 3(a)).

Under such a compressive stress field, when the punch 1 having the punch radius rp is lowered, the pilot hole B of the blank material B is formed.

As shown in Fig. 3(b), the peripheral area is the corner rounded corner (diameter r) of the upper surface of the die 3 (diameter 0.1').
=D1+2r, 1) Deforms into a truncated conical shape with X as the starting point.

Then, the stress state that was balanced under the pilot hole diameter d1 of the initial blank material B is approximated as if a medium flame was created in the blank material B with a diameter equal to the rounded corner dimension described above. changes to the stress state. This change in the stress state promotes the flow of the material that was balanced near the outer periphery of the diameter Dd' of the die 3 into the frusto-conical portion. In this case, Figure 3 (
The material inflow progresses in the truncated cone forming state shown in b), and the initial prepared hole diameter is 6. is reduced in diameter dI'. And Figure 3 (c
This diameter reduction action continues until the predetermined height of the truncated cone shown in ) is reached, and in this process most of the volume of material has been inflowed.

As the punch 1 subsequently descends, the rounded corner of the punch 1 slides inside the truncated conical part, causing the initial pilot hole diameter d to change.

Instead, move on to expanding the hole in which hole (3rd step).
(See figure (d)). From this state, further material flows into the interior due to the frictional force with the blank material B as the punch 1 descends as shown in FIG. A boss having a thickness regulated by the inner diameter Dd of the die 3 is formed.

In these processes, the blank outer diameter d is reduced by horizontal pressing force.

Naturally, the diameter will be reduced, so this reduction in diameter must be accounted for in the required size of the product.

In this way, a boss with a predetermined thickness and height can be produced in one process without being constrained by the volume supply to the boss part in burring process, and without being subject to process constraints due to the breaking limit in drawing process. I can do it.

This is significantly different from the forming mechanism in the conventional method of performing deep drawing while applying pressure from the outer periphery of the flange, as disclosed in Japanese Patent Application Laid-open Nos. 57-168730 and 59-73129.

That is, all of the above-mentioned known methods attempt to improve the drawing limit to some extent by applying additional pressure from the outer periphery of the flange against the shrinkage resistance of the flange outer periphery during drawing.

The forming limit of drawing processing is determined by the force that can be transmitted by the material to the forming wall under tensile stress, with respect to the shrinkage resistance, bending resistance, and frictional resistance of the flange and die shoulder. We are merely trying to improve its communicability by reducing some of it.

On the other hand, the method of the present invention, as described above, applies horizontal pressure from the circumferential direction to the compressive yield point or higher to allow the material to flow while allowing the thickness of the flange to increase. The molding limit is not influenced by the properties. As a result, it is possible to easily form a workpiece material, such as 545C (JIS standard), which is generally said to be difficult to draw.

Next, an example in which a bossed member is formed using a woodworking method will be described.

FIG. 4 shows a blank material B as an example of the material. Plate thickness t = 4.5 mm, material 5PltC (tensile strength T,
-33 g/mm2) blank material B has a roughly triangular outer diameter, six strip-like arms extending radially from the center, and a prepared hole B in the center. It is formed by punching out a material plate to have the following.

The six arms are long arms (distance from the center of the engineering center to the outer edge! 1dO
L/2, width Wt) B+ and short arm (same (dos/2
.

Widths Is ) B and 3 are alternately arranged at 60° intervals. A notch B is formed at the intersection of the multiple arms. This was molded using the method described above. however,
As for the horizontal pressing force, pressure was applied at three locations on the long arm B and at 23 locations on the short arm B (the total sum of the pressing forces was as described above).

As a result, as shown in Figure 5, the plate thickness tc at the base of the boss is about 1.2 times the plate thickness t of the blank material B, and the volume vI forming the boss part is the volume v0 formed by general burring.
A bossed member was obtained which was significantly improved by about 1.7 times.

Next, as an example of processing other materials, a difficult-to-process material 545G (tensile strength T
Processing was carried out on s-50Kg/mm.

In this case, each pressing force was approximately 1.5 times that of the previous example to create a ground-like shape. As a result, a bossed member substantially the same as the previous example was obtained.

Next, an example of a press mold used in the second embodiment of the present invention will be explained with reference to FIG. For ease of understanding, parts that are the same as those in the press die explained in FIG.
This is because it has a two-division configuration with aDdB and radius rlB.

This example shows how to form the truncated cone in the previous example.
By increasing the inner diameter DdA of the die 3A, material flow toward the truncated cone is more effectively generated by horizontal pressure, and a higher boss shape is created.

To explain the molding process, Fig. 6(a) and (b)
) is the same as in FIGS. 1(a) and 1(b) above, but in this example, the bending starting point of the truncated cone is at the outer die 3A.
The corners are rounded, and the effect of a larger horizontal pressing force is exerted, resulting in a large volumetric flow. and,
As the bunch 1 is further lowered as shown in FIG. 6(C), the hole of the truncated conical head is expanded.

In this state, when the inner die 3B is raised while continuing the horizontal pressing force, the material supplied to the truncated conical part is supplied to the inside of the boss without being pushed back outside, and the punch outer diameter DP, The thickness is regulated by the inner diameter of the inner die and B.
A higher boss was formed. Pressure force pp of punch 1 is 1
In this case, the pressing force Pu of the inner die 3B was set to 5 and molding was performed.

As a result, as shown in FIG. 7, the plate thickness te at the base of the boss is approximately 1.6 times the plate thickness t of the blank material B, and the volume v2 forming the boss is the volume v0 formed by general burring. A bossed member was obtained which was dramatically improved by about 2.8 times.

Next, FIG. 8 shows an example of the shape of a blank material used to obtain a bossed member obtained by the method of the present invention. As shown in FIGS. 8(a), (b) and (C), a circular blank material 8a, an irregularly shaped blank material Bb, and a blank material with escape holes Bc can be used.

In the case of irregularly shaped blank material Bb, half of the inscribed circle diameter d0' of the notch C between the arms is substantially the pilot hole B of the blank material.
This corresponds to the distance from the zero center to the outer edge, and the amount of material flowing into the die can be dramatically increased compared to the circular blank material Ba, making it possible to obtain a higher and thicker boss portion.

A similar effect can be obtained by drilling an escape hole H in a circular blank material, and in this case, the diameter d0' of the inscribed circle to the escape hole corresponds.

Further, in the case of a circular blank material, the same effect can be obtained by locally increasing the distance between the temporary presser and the die, in addition to the above-mentioned escape hole.

In the above embodiments, for convenience, the press molds have been described in terms of vertically oriented press dies, but it goes without saying that the press dies can also be oriented horizontally or upside down by slightly changing the detailed structure.

In the above example, if the hole is circular with the center of the prepared hole, the horizontal pressing force ph may be applied evenly from the periphery by hydraulic pressure, or may be applied by mechanical means other than hydraulic pressure.

[Effects of the Invention] As is clear from the above description, according to the first embodiment of the method of the present invention, the bossed member having a predetermined thickness and height with excellent surface accuracy can be formed at low cost because it can be formed in a single step. can be obtained.

Further, according to the second embodiment of the method of the present invention, a bossed member having a predetermined thickness similar to that described above and a higher height can be obtained in a single step or in two steps.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a press mold used in the first embodiment of the present invention, and a diagram explaining the process, and FIG. 2 is a process explanatory diagram showing an example of the first embodiment of the present invention. and an operation timing diagram; FIG. 3 is a diagram showing a process for explaining the boss forming mechanism; FIG. 4 is a plan view showing a blank material when forming a member with a boss using the method of the present invention. , FIG. 5 is a cross-sectional view comparing the main part of the blank material and the boss portion obtained above, and FIG. 6 is a cross-sectional view showing an example of a press mold used in the second embodiment of the present invention, and its process. FIG. 7 is a sectional view comparing the main part of the blank material and the boss portion obtained by the above, FIG. 8 is a plan view showing an example of the shape of the blank material used in the method of the present invention, The left side is a view showing before molding, the right side is a view after molding, FIG. 9 is a sectional view showing the general shape of a bossed member, and FIG. 10 is a sectional view showing a conventional method of forming a bossed member. 1... Punch, 2... Temporary presser, 3... Die, 6... Hydraulic cylinder, 7... Pressure plate, 8... Knockout, 9... Nest bin, B... Blank material, G...boss part. Figure 5 Figure 7

Claims (1)

[Claims] 1) Drill a pilot hole in the center of a metal plate blank, set the plate blank between a die and a plate holder, and drill from the outside of the plate blank. The punch was brought closer to the die while applying pressure toward the center using a pressure means, the area around the pilot hole was formed into a truncated conical shape, and the punch was further pushed in to expand the hole and form a boss portion. A method for forming a member with a boss, characterized by: 2) Drill a pilot hole in the center of the metal plate blank, set the plate blank between the outer die and the plate holder, and machine the plate blank from the outside toward the center. The punch is brought close to the die while being pressurized by a pressure means, the area around the prepared hole is formed into a truncated conical shape, the punch is further pushed in to enlarge the hole, and then the inner die provided inside the outer die is punched. A method for forming a member with a boss, characterized in that the boss is formed by pushing in a direction opposite to the pushing direction of the boss.