JPH0353049B2 - - Google Patents

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 bossed member capable of withstanding torque transmission is formed by attaching a boss portion _G (final outer diameter of the bossed member: D ), it is often desired that the thickness t _b of the boss portion G be as thick as possible within the plate thickness t of the blank material B, and that the height h be as high as possible. .

This is to ensure the torque resistance strength of the splines formed on the inner diameter portion G _i of the boss portion G of the boss member, and to minimize the axial deflection at the outer circumferential portion B _S .

The conventional method of forming such a bossed member is as follows:
The following are known.

The first method is a so-called burring process, in which a boss with an inner diameter d ₂ is formed in the center as shown in Fig. 10a.
In this method, a hole is expanded using a punch whose outer diameter is the boss inner diameter dimension _d2 on a plate-shaped blank material B in which a pilot hole B0 with a diameter _d1 smaller _than that is bored.

However, this method has a hole expansion rate (=(d ₂
Since there is a limit value of -d ₁ )/d ₁ ), it is often impossible to obtain a boss with both thickness and height that can sufficiently withstand torque transmission.

Therefore, as a second method, as shown in FIG. 10b, the drawing process is repeated several times on the plate-shaped blank B while ensuring an appropriate drawing ratio until the boss inner diameter dimension d ₂ 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 10c,
The drawing process was performed multiple times in the same manner as in
After (1) to (7)), a method is used in which a pilot hole with a diameter smaller than the inner diameter of the boss is bored (step (8)) and the hole is enlarged (step (9)).

[Problems to be solved by the invention] However, in such conventional methods,
As mentioned above, the first method is not sufficient because there is a limit to the wall thickness and height of the boss due to the hole expansion rate.

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 the drawing process in multiple stages in this way requires a large number of press molds with slightly different mold shapes, which increases the manufacturing cost of the molds and also requires multiple steps in the production process, causing an increase in costs. In addition, due to the multi-step drawing process, irregularities (die marks) in the plate thickness were created on the flange portion, and a decrease in surface accuracy was unavoidable.

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 punch, a plate holder through which the punch passes, a die, and a Using a press mold having a pressure means for applying pressure,
A method for forming a member with a boss, the method comprises: drilling a pilot hole in the center of a metal plate blank; and inserting the plate blank between the die and the plate holder. The plate blank is set in a state that allows pressure to be applied in the direction toward the center of the prepared hole, and the plate-shaped blank is pressed from the outside toward the center of the prepared hole by the pressurizing means to a pressure equal to or higher than the compressive yield point of the plate-shaped blank. The boss portion is formed by pressurizing with a pressure of , and while continuing the pressurization, a punch is pushed in with a punch pressure smaller than the pressure.

Further, in a second embodiment of the present invention, a press includes a punch, a plate holder through which the punch passes, a die including inner and outer dies, and a pressurizing means for pressurizing in a direction toward the center of the punch. A method of forming a member with a boss using a mold, the method comprising: drilling a pilot hole in the center of a metal plate-shaped blank; and inserting the plate-shaped blank between the outer die and the plate holder. is set in a state that allows pressure to be applied in a direction toward the center of the prepared hole of the plate-shaped blank, and the plate-shaped blank is moved from the outside toward the center of the prepared hole by the pressurizing means. Applying pressure with a pressure equal to or higher than the compressive yield point of the blank material, pushing a punch with a punch pressure smaller than the pressure while continuing the pressurization, and further pushing the inner die in a direction opposite to the pushing direction of the punch, A feature is that a boss portion is formed.

[Function] According to the first embodiment of the present invention, first, a plate-shaped blank material with a prepared hole bored in the center allows pressurization in a direction toward the center of the prepared hole between the die and the plate holder. It is set as possible.

When this blank material is pressurized from multiple directions on the outside toward the center of the prepared hole using a pressurizing means with a pressure greater than the compressive yield point of the plate-shaped blank material, the equivalent stress in the vicinity of the prepared hole portion of the blank material increases. As a result, the area around the pilot hole yields and plastic deformation begins. and,
This plastic deformation successively 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 applied 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 diameter of the prepared hole in the initial blank material changes to a stress state similar to that in which a hole corresponding to the diameter of the die corner end is virtually created, and the die space becomes smaller. The flow of material that was balanced near the periphery into the frusto-cone is promoted.

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. Thereafter, as the punch is pushed in further, the rounded corner of the punch slides inside the truncated conical part, enlarging the pilot hole, forming a boss with a predetermined thickness and height, and forming the boss. The peripheral area 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 punches were pushed in further,
Similarly, the prepared hole is expanded and formed, and when the inner die provided inside the outer die is pushed in the opposite direction to the pushing direction of the punch while continuing to apply pressure from the periphery, the punch outer diameter A boss having a predetermined thickness and a height higher than that obtained in the first embodiment is formed at the inner diameter of the inner die, and the thickness of the boss periphery is also increased.

As described above, according to the present invention, a boss portion having a predetermined thickness and height is formed in a substantially single process, and the thickness of the surrounding portion of the boss is increased, thereby reducing costs and improving the surface accuracy of the flange. A boss-attached member with a well-reinforced boss base can be obtained.

[Examples] 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 explained based on FIG. 1.

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 the role of determining the corner radius r _P that contributes to controlling the flow direction of the material and the final boss inner diameter dimension. It has an outer diameter D _P. Its preferred value is D _P /2≧r _P >D _P /3, and punch pressure P _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 able to move up and down separately from the punch 1 by means of 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 P _C to a certain extent.

3 is a die fixed on the bed 5 together with the die holder 4, and the corner radius (die radius) r _d serves as a bending starting point for the deformation of the blank material B into a truncated conical shape and is a main factor in promoting material flow.
and the inner diameter, which ultimately plays the role of giving the outer shape of the boss.
D has _d .

The material flow rate is the die corner end dimension D _d ′ (= D _d
+2r _d ), so the diradius
It is necessary to appropriately define r _d .

This preferable value must satisfy r _d ≧t and be within a range allowed for the final shape of the bossed member.

Similarly, 6 is a plurality of hydraulic cylinders arranged and fixed radially at equal intervals on the bed 5 with the punch 1 as the center, for generating horizontal pressing force P _h ;
It has a piston 6A. Let P _h 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 in the center direction between the plate holder 2 and the die 3, and is capable of applying a force higher than the compressive yield point of the blank material B from the outside. can be added.

Note that the reference numeral 8 designates a knock-out which 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 the blank material B.
It should be selected appropriately depending on the type of plate, etc., but in general, when the punch pressure P _P is 1, the plate press force P _C is 3 to 7,
The total horizontal pressing force P _h is preferably set at a ratio of 10 to 15, with the latter being significantly larger.

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

First, as shown in Figure 2a, make a pilot hole in the center.
The blank material B with the B ₀ drilled therein moves upward and its prepared hole B ₀ is engaged with the nest pin 9 which is in a stationary state. This time is the start of the molding process and the time
Let t be ₀ . Next, the blank material B is placed on the die 3 by the downward movement of the knockout 8 and the nest pin 9, and the pressure plate 7 starts moving toward the center at time _t1 , and the blank material B is placed on the die 3 as shown in FIG. 2b. The blank material B is positioned by coming into contact with the outer end of the material B (time t ₂ ). During this time, the punch 1 continues to descend at high speed together with the presser foot 2, and at time t ₃
As shown in Figure 2c, the knockout 8
is further moved downward, and immediately before the plate holder 2 contacts the blank material B, the lowering speed of the punch 1 is switched to a low speed.

Thus, at time _t4 , a state is obtained in which the blank material B is set between the die 3 and the plate holder 2 (see FIG. 2d and FIG. 1a).

At this time _t4 , the hydraulic cylinder 6
A high pressure is applied to the blank material B via the pressure plate 7, and a load exceeding its compressive yield point is started to be applied. While continuing to be pressurized by the pressure plate 7, the punch 1 is lowered at a low speed to press the blank material B.
It abuts to form a truncated cone and continues to descend, forming a boss. During this time, the plate holder 2 moves upward while applying pressure to absorb the increase in the thickness of the blank material B (the plate holder stroke shown in the second figure is the same as that of the punch 1).
(The tip is shown as the zero reference).

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

The forming of the boss portion ends at time _t5 when the punch 1 reaches the bottom dead center (Fig. 2 e and Fig. 1 c).
After a predetermined time, the pressure plate 7 first starts to move backward at t ₆ , and then at t ₇ , the punch 1 and the knockout 8 start to move upward, and the time
At t ₈ , the speed is increased and the molded product is discharged.

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

In Fig. 3a, a horizontal pressing force equal to or higher than the compressive yield point is applied from the outer end of the blank material B having an outer diameter d ₀ , a plate thickness t, and a prepared hole diameter d _i toward the center via the pressure plate 7.
When P _h is applied, first the pilot hole B ₀ of the blank material B is
The equivalent stress near the hole B ₀ increases, and the area around the prepared hole B 0 yields and starts plastic deformation. This plastic deformation gradually propagates outward while causing work hardening, until the internal stress is balanced (see Figure 3a).

Under such a compressive stress field, the punch radius
When the _{punch 1} with _a diameter _r ′=D _d +2r _d ) It transforms into a truncated conical shape with X as the starting point.

Then, the stress state that was balanced under the initial hole diameter d _i of blank material B changes as if it were
The stress state changes to an approximate state when a hollow hole with a diameter D _d ', which is the corner round stop dimension, is created. This change in the stress state promotes the flow of the material that was balanced near the outer periphery of the diameter D _d ' of the die 3 into the frusto-conical section. In this case, the material inflow progresses in the truncated cone forming state shown in Figure 3b, and the initial pilot hole diameter
d _i is reduced in diameter by d _i ′. This diameter-reducing action continues until the truncated cone reaches a predetermined height as shown in FIG.

As the punch 1 subsequently descends, the rounded corner of the punch 1 slides inside the truncated cone, and the initial pilot hole diameter d _i
The process moves on to hole expansion forming into a hole with a larger diameter d _i '' (see Figure 3 d). From this state, due to the frictional force with the blank material B as the punch 1 descends as shown in Figure 3 e, Further internal inflow of material occurs, and finally, at a predetermined height, the outer diameter D _P of punch 1 and the inner diameter of die 3
A boss with a thickness regulated by D _d is formed.

In these processes, the outer diameter d ₀ of the blank naturally decreases due to the horizontal pressing force, so this reduction 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 rupture limit in drawing process. I can do it.

This is greatly 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 JP-A-57-168730 or JP-A-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 for the flange, die shoulder, shrinkage resistance, bending resistance, and frictional resistance. 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 generally said that drawing is difficult, for example.
Work materials such as S45C (JIS standard) can also be easily formed.

Next, an example in which a bossed member was formed using this construction method will be described.

FIG. 4 shows a blank material B as an example of the material. Plate thickness t = 4.5 mm, material SPHC (tensile strength T _s =
Blank material B of 33Kg/mm ² ) has an approximately triangular outer diameter shape, and is punched out from a material plate to have six strip-like arms extending radially from the center and a prepared hole _B0 in the center. It is formed by

The six arms are the long arm (distance from the center of the pilot hole to the outer edge d _OL /2, width W _L ) B ₁ and the short arm (also d _OS /2,
Width Ws) B ₂ are arranged alternately in groups of 3 at 60° intervals. A notch _B3 is formed at the intersection of each arm. This was molded using the method described above. However, as for the horizontal pressing force, three places on the long arm _B1 and three places on the short arm _B2 were applied with different systems of pressing force (the sum of the pressing forces is as described above).

As a result, as shown in Figure 5, the plate thickness at the base of the boss t _C
was approximately 1.2 times the plate thickness t of the blank material B, and a bossed member was obtained in which the volume V ₁ forming the boss portion was approximately 1.7 times the volume V ₀ formed by general burring processing, which was greatly improved.

Next, as an example of processing another material, a difficult-to-process material S45C (tensile strength T _S =50 Kg/mm ² ) having the same shape and the same thickness as that shown in FIG. 4 was processed.

In this case, each pressure force was set to about 1.5 times that of the previous example, and the processing was performed in the same manner. 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 state of the present invention will be explained with reference to FIG. For ease of understanding, the same parts as those in the press mold explained in Fig. 1 are given the same reference numerals, and to explain the differences, the die is divided into an outer die 3A (inner diameter D _d A, die radius r _d A) and an inner die. 3B (inner diameter D _d B, diameter radius r _d B).

In this example, when forming the truncated conical shape in the previous example, by increasing the inner diameter D _d A of the die 3A, material flow into the truncated conical shape by horizontal pressure is more effectively generated. This creates a higher boss shape.

To explain the forming process, the steps in FIGS. 6a and 6b are the same as those in FIGS. The effect of a larger horizontal pressing force is exerted, and a large volumetric flow is generated. Then, as shown in FIG. 6c, when the punch 1 is further lowered, 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 D _P , Inner die inner diameter D _d
A higher boss is formed with a thickness regulated by B. In this example, a blank material with the same shape and material (SPHC) as the previous example and a plate thickness of t = 4.7 mm is used.
Processing was carried out under the same pressure conditions as in the first example. When the pressing force P _P of the punch 1 was set to 1, the pressing force P _u of the inner die 3B was set to 5 for molding.

As a result, as shown in Fig. 7, the plate thickness t _C at the base of the boss is approximately 1.6 times the plate thickness t of the blank material B, and the volume V ₂ forming the boss portion becomes the volume V formed by general burring. A material with a boss was obtained that was dramatically improved by approximately 2.8 times that of ₀ .

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. 8a, b and c, circular blanks Ba, irregularly shaped blanks Bb and blanks with escape holes Bc can be used.

In the case of the irregularly shaped blank material Bb, half of the inscribed circle diameter d ₀ ' of the notch c between the arms corresponds to the distance between the blank material and the center of the prepared hole B ₀ to the outer end,
The amount of material flowing into the die can be dramatically increased compared to circular blank material Ba, and a higher and thicker boss can be obtained.

A similar effect can be obtained by drilling a hole H in a circular blank material, and in this case, the diameter of the inscribed circle to the hole H corresponds to d ₀ '.

Furthermore, in the case of a circular blank material, the same effect can be obtained by locally enlarging the distance from the plate holding die instead of using 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 addition, in the above example, the horizontal pressing force P _h was applied from 6 directions radially toward the center of the prepared hole, but
This may be done from a plurality of other directions, and if the outer periphery of the blank material is circular, pressure may be applied evenly from the periphery by hydraulic pressure, or it may be done 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 drawings]

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, and 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 sectional view comparing the main part of the blank material and the boss portion obtained above, and FIG. 6 is a 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 cross-sectional view comparing the main part of the blank material and the boss portion obtained above, and 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... Board presser, 3... Die, 6
... Hydraulic cylinder, 7 ... Pressure plate, 8 ...
Knock out, 9...Nest pin, B...Blank material, G...Boss part.

Claims (1)

[Claims] 1. Molding a member with a boss using a press mold having a punch, a plate holder through which the punch passes, a die, and a pressure means for applying pressure in a direction toward the center of the punch. The method includes: drilling a pilot hole in the center of a metal plate blank, and moving the plate blank between the die and the plate holder toward the center of the pilot hole in the plate blank. The plate-shaped blank is set in a state that allows pressure in the direction, and the plate-shaped blank is pressed from the outside toward the center of the prepared hole by the pressing means with a pressure equal to or higher than the compressive yield point of the plate-shaped blank. A method for forming a member with a boss, characterized in that the boss part is formed by pressing a punch with a punch pressure smaller than the pressing force while continuing the pressing force. 2. A member with a boss is made using a press mold having a punch, a plate holder through which the punch passes, a die having inner and outer dies, and a pressure means for applying pressure in a direction toward the center of the punch. A method of forming a metal plate blank material, wherein a prepared hole is bored in the center of a metal plate blank material, and the plate blank material is placed between the outer die and the plate holder at the center of the prepared hole of the plate blank material. The plate-shaped blank is set in a state that allows pressure to be applied in a direction toward the plate-shaped blank, and the plate-shaped blank is applied with a pressure equal to or higher than the compressive yield point of the plate-shaped blank by the pressurizing means from the outside toward the center of the prepared hole. and pressurize the punch with pressure, continue pressing the punch with a punch pressure smaller than the pressurizing force, and further push the inner die in a direction opposite to the pushing direction of the punch to form the boss portion. Characteristic method of forming bossed parts.