Title: Die forming method for forming female screw
Abstract: A molten magnesium material is filled into a product section of a die. The molten magnesium material is cooled and solidified in the die, so that a molded product is formed. Subsequently, a thread-shaped pin is rotated, so that a female-thread forming section is drawn from the female-thread section of the molded product while the female-thread forming section is rotated. Thus, the female-thread section can be formed when the molded product is formed. A magnesium-alloy material is not apt to stick to a steel material used in the die compared with an aluminum-alloy material, so that the female-thread section can be steadily formed.
Patent Number: 7,007,736 Issued on 03/07/2006 to Suzuki, et al.
| Inventors:
|
Suzuki; Hideyuki (Kariya, JP);
Kayano; Hisashi (Toyoake, JP);
Sato; Koichiro (Kariya, JP)
|
| Assignee:
|
Denso Corporation (Kariya, JP)
|
| Appl. No.:
|
751656 |
| Filed:
|
January 6, 2004 |
Foreign Application Priority Data
| Jan 09, 2003[JP] | 2003-003580 |
| Current U.S. Class: |
164/132; 164/348 |
| Current Intern'l Class: |
B22D 17/22 (20060101) |
| Field of Search: |
164/132,113,348
|
References Cited [Referenced By]
U.S. Patent Documents
| 5501266 | Mar., 1996 | Wang et al.
| |
| 6460602 | Oct., 2002 | Kubota et al.
| |
| 6634412 | Oct., 2003 | Murray et al.
| |
| 6745821 | Jun., 2004 | Wilson.
| |
| 2001/0023720 | Sep., 2001 | Ohori et al.
| |
| Foreign Patent Documents |
| U-S62-7275/9 | May., 1987 | JP.
| |
| A-H02-187243 | Jul., 1990 | JP.
| |
| A-H04-5206/6 | Feb., 1992 | JP.
| |
| A-H07-112265 | May., 1995 | JP.
| |
| A-H08-309505 | Nov., 1996 | JP.
| |
| A-H09-1314 | Jan., 1997 | JP.
| |
| 10-113758 | May., 1998 | JP.
| |
| A-H10-146666 | Jun., 1998 | JP.
| |
| A-H10-202353 | Aug., 1998 | JP.
| |
Primary Examiner: Tran; Len
Attorney, Agent or Firm: Posz Law Group, PLC
Claims
What is claimed is:
1. A die forming method for forming a molded product having a female-thread section comprising:
a filling process in which a fluidic material is filled into a die including
a core pin having a screw-shaped portion, which is made of a steel material, shaped
in correspondence with the female-thread section;
a solidification process in which the fluidic material filled in the filling
process is cooled and solidified to form the molded product; and
a thread-drawing process in which the screw-shaped portion of the core pin is
drawn while being rotated from the molded product after the solidification process,
wherein the fluidic material filled in the filling process is a magnesium-alloy material,
wherein a plurality of molded products are formed over a plurality of times; and
wherein a temperature of the core pin is adjusted to be at a substantially same
pre-heating temperature when the thread-drawing process is performed for the plurality
of times.
2. The die forming method according to claim 1, wherein:
the core pin has a surface on which an inert material layer is formed; and
the inert material layer has low reactivity with respect to the fluidic material.
3. The die forming method according to claim 1, further comprising an application
process, in which mold lubricant is applied to a surface of the core pin, in advance
of the filling process.
4. The die forming method according to claim 1, further comprising a cooling
process, in which the core pin is cooled, in advance of the filling process.
5. The die forming method according to claim 4, wherein the core pin is cooled
to be below 300° C. in the cooling process.
6. The die forming method according to claim 4, wherein the cooling process includes
discharging fluid to the core pin so that the core pin is cooled in the cooling process.
7. The die forming method according to claim 6, wherein the fluid is mold lubricant.
8. The die forming method according to claim 1, wherein:
a temperature of a cavity defined in the die is detected by a temperature detecting
means, wherein the product is molded in the cavity; and
a temperature of a vicinity of the cavity including the female-thread forming
section is controlled by a temperature control means, wherein the temperature control
means is energized and heated based on a detection signal of the temperature detecting
means, so that the vicinity is controlled at a predetermined temperature at least
in advance of the filling process.
9. The die forming method according to claim 8, wherein the temperature control
means is a heater.
10. The die forming method according to claim 8, wherein the temperature detecting
means is a thermocouple.
11. The die forming method according to claim 1, wherein:
a temperature of a cavity defined in the die is detected by a temperature detecting
means, wherein the product is molded in the cavity; and
a heat medium is circulated inside a heat medium piping defined in the die, to
heat the cavity, so that the temperature of the cavity is controlled at a predetermined
temperature at least in advance of the filling process.
12. A die forming method for forming a molded product having a female-thread
section, the die forming method comprising:
filling a fluidic material into a die in a filling process, the die including
a core pin having a screw-shaped portion;
cooling and solidifying the fluidic material filled in the filling process to
form the molded product in a solidification process; and
drawing the screw-shaped portion of the core pin while being rotated from the
molded product in a thread-drawing process,
wherein:
a temperature of the core pin is adjusted at a predetermined pre-heated temperature
in at least a beginning of the thread-drawing process; and
the predetermined temperature of the core pin is substantially same for a plurality
of times of forming a respective plurality of molded products.
13. The die forming method according to claim 12, further comprising:
detecting a temperature of a cavity defined in the die and providing a detection
signal responsive thereto; and
energizing a temperature control means to be heated responsive to the detection
signal, so that a vicinity of the cavity including the female-thread forming section
is controlled at the predetermined temperature at least in advance of the filling process.
14. The die forming method according to claim 12, further comprising:
detecting a temperature of a cavity defined in the die; and
circulating a heat medium inside a heat medium piping defined in the die, to
heat the cavity of the die at least in advance of the filling process.
15. A die forming method for forming a molded product having a female-thread
section, the die forming method comprising:
lubricating a core pin in a lubricating process;
applying lubricant over a female-thread forming section in the lubricating process;
filling a fluidic material into a die in a filling process, the die including
a core pin having a screw-shaped portion;
cooling and solidifying the fluidic material filled in the filling process to
form the molded product in a solidification process; and
drawing the screw-shaped portion of the core pin while being rotated from the
molded product in a thread-drawing process,
wherein:
the core pin and the female-thread forming section are cooled, so that a temperature
of the core pin and the female-thread forming section becomes below 300° C.
in the lubricating process.
16. The die forming method according to claim 15, wherein:
the temperature of the core pin is adjusted at a predetermined temperature in
at least a beginning of the thread-drawing process; and
the predetermined temperature of the core pin is substantially same for a plurality
of times of forming a respective plurality of molded products.
Description
CROSS REFERENCE TO RELATED APPLICATION
This application is based on Japanese Patent Application No. 2003-3580 filed
on Jan. 9, 2003, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a molding method for molding a product which
has a female screw section.
2. Description of Related Art
Conventionally, a component is die-cast of an aluminum alloy, and
subsequently machining work (i.e., tapping) is performed to the component, so that
a connecting component having a female screw is manufactured.
According to JP-A-2-187243, a core pin is provided in a casting die. A
molten metallic material is filled into the molding die, and the filled metal is
cooled. Subsequently, the core pin is drawn while being rotated, after the filled
metal is solidified, so that a component with a female screw can be integrally
formed when the component is formed by die-casting.
However, in this case, if an aluminum-alloy material is used as a casting
material, the aluminum alloy is apt to stick to the core pin. Accordingly, the
threads may be broken when the core pin is rotated and drawn. Therefore, it is
hard to stably form the female screw in the component. On the contrary, if the
female screw is tapped in the die-cast component made of aluminum-alloy material,
manufacturing process becomes complicated.
SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the present invention to
provide a die forming method, which can stably form a female screw with a simple
manufacturing process.
A die forming method in the present invention is for forming a molded product
having
a female-thread section. The die forming method includes a filling process, a solidification
process, and a thread-drawing process.
In the filling process, a molten material or a semiliquid material is filled
into
a die including a core pin for forming a female-thread section. In the solidification
process, the molten material or the semiliquid material filled in the filling process
is cooled and solidified to form a molded product. In the thread-drawing process,
the core pin is drawn while being rotated from the molded product after the solidification
process. The molten material or the semiliquid material filled in the filling process
is a magnesium-alloy material.
A magnesium-alloy material has a characteristic which is not apt to stick to
the
die including the core pin, compared with an aluminum-alloy material. Therefore,
the product having the female-thread section can be integrally formed, when the
product is formed using the die including the core pin. Thus, the female-thread
section can be stably formed without complicated forming process.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present invention
will become more apparent from the following detailed description made with reference
to the accompanying drawings. In the drawings:
FIG. 1 is a schematic cross-sectional view showing a die according to a first
embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view showing a molded product;
FIG. 3 is a schematic cross-sectional view showing an application process of
mold lubricant in a forming process of the molded product;
FIG. 4 is a schematic cross-sectional view showing a clamped die after the application
process of mold lubricant;
FIG. 5 is a schematic cross-sectional view showing a filling process of a magnesium-alloy
material and a solidification process;
FIG. 6 is a schematic cross-sectional view showing a drawing process of a screw
section from a female thread forming section;
FIG. 7 is a schematic cross-sectional view showing an opened die after finishing
the drawing process of the screw section;
FIG. 8 is a schematic cross-sectional view showing an opened die after finishing
the drawing process of the screw section;
FIG. 9 is a schematic cross-sectional view showing a state before a cooling
process; and
FIG. 10 is a schematic cross-sectional view showing the cooling process.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[First Embodiment]
As shown in FIG. 1, a die
1 is used for injection molding of a molten
metallic
material or a semiliquid metallic material (a magnesium alloy material in this
embodiment). The die
1 is constructed with a fixed die
11 and a movable
die
12. Both dies
11,
12 are made of steel material. A sprue
2 is defined in the fixed die
11. A runner
3 is connected
with a lower end section of the sprue
2. A product section
5 is formed
on the end of the runner
3 through the gate
4.
An inline-type screw injection molding apparatus (not shown) is used in this
embodiment,
for example. In the injection molding apparatus, a nozzle section is located in
an end section of an outer cover of a screw. The nozzle section fits in the opening
section of the sprue
2 of the die
1, when injection molding is performed.
The sprue
2 and the runner
3 construct a supplying passage for supplying
a metallic material into the product section
5 in the die
1.
Ejector pins
21 are provided in the movable die
12. The ejector
pins
12 move to the right in FIG. 1, so that a solidified metallic material,
which is formed in the product section
5 and the supplying passage, can
be removed from the movable die
12.
As shown in FIG. 2, a molded product
50 is constructed with a flat-shaped
plate section
51 and a cylindrical section
52, which perpendicularly
extends from the plane of the plate section
51. A female thread
53
is formed in the inner periphery of the cylindrical section
52.
Referring back to FIG. 1, a screw-shaped pin (core pin)
30 is partially
received in a sliding hole
24 of the movable die
12. The screw-shaped
pin
30 has a female-thread forming section (screw-shaped portion)
31
on its end section, which is located on the right side in FIG. 1. The female-thread
forming section
31 can slide in the sliding hole
24, so as to project
into the product section
5. The female-thread forming section
31
is formed in a male-screw shape, so as to correspond to the female thread
53
of the molded product
50. The screw-shaped pin
30 is made of a steel
material. The surface of the female-thread forming section
31 is coated
with a ceramic material, so that a ceramic material layer (inert material layer)
is formed. The ceramic material has a low reactivity with respect to a magnesium
alloy material.
A screw section
32 is formed in the screw-shaped pin
30 on the
left
side end section in FIG. 1. The screw section
32 has a male screw, which
has a same screw pitch as a screw pitch of the female-thread forming section
31.
The screw section
32 is screwed into a female screw formed in a guide section
22, which is provided in the movable die
12. The screw section
32
is slid while being rotated in the guide section
22. Therefore, the screw-shaped
pin
30 is rotated, so that the female-thread forming section
31 can
be slid into the product section
5. The female-thread forming section
31
can also be slid out of the product section
5. A gear
33 is provided
on the right side of the screw section
32 of the screw-shaped pin
30
in FIG. 1. The gear
33 engages with a gear
23a which is coupled
with a driving motor
23. Driving force of the driving motor
32 is
transmitted by the gears
23a and
33, so that the screw-shaped
pin
30 is rotated.
A fluid passage
25 is defined in the movable die
12, and communicated
with the sliding hole
24 on the downstream side end of the fluid passage
25. A fluid nozzle
26 is provided on the upstream side end of the
fluid passage
25, so that fluid can be discharged into the fluid passage
25. The fluid is mold lubricant.
A heater (temperature control means)
27 is provided in the movable die
12
for controlling temperature vicinity of the product section
5 of the movable
die
12. A temperature sensor (temperature detecting means)
28 detects
temperature of the product section
5 of the movable die
12. A thermocouple
is used for the temperature sensor
28. The heater
27 is energized
and heated based on the detection signal of the temperature sensor
28, so
that vicinity of the product section
5 including the female-thread forming
section
31 of the die
1 is controlled at a predetermined temperature.
As shown in FIG. 3, the die
1 is opened and separated into the fixed die
11 and the movable die
12 in the beginning of a forming process of
the molded product
50. An application nozzle
40 is located between
the fixed die
11 and the movable die
12 for applying mold lubricant.
Mold lubricant is applied to the inside plane of the product section
5 or
the like. Water-soluble mold lubricant is applied from the application nozzle
40,
however oil-based mold lubricant or the like can be applied from the application
nozzle
40. In this state, the screw-shaped pin
30 is slid to the
right in FIG. 3,
80 that the female-thread forming section
31 is
projected into the product section
5.
Next, as shown in FIG. 4, the movable die
12 is moved, so that the fixed
die
11 and the movable die
12 (i.e., die
1) are clamped together
after application of mold lubricant. The nozzle section (not shown) of the injection
molding apparatus (injection unit) is connected with the upstream side end of the
sprue
2, after clamping the die
1.
As shown in FIG. 5, a molten magnesium alloy material is injected from the nozzle
section of the injection unit (not shown) into the product section
5 through
the sprue
2, the runner
3, and gate section
4, so that the
inside space of the product section
5 is filled with molten magnesium alloy.
The molten magnesium alloy material is heated at 600° C., and injected at
2 m/sec (screw speed of the injection unit),
60 that the product section
5 of the die
1 is filled with the magnesium alloy material. For example,
alloy number AZ91D is used for the magnesium-alloy material in this embodiment.
The injection material can be a semiliquid material, such as alloy number AZ91D
heated between 560° C. and 570° C. Here, the semiliquid material partially
includes solid state portions. The material can be AM50A, AM60B, or the like. Namely,
a molten material and a semiliquid material (i.e., fluidic material) can be used
for the die forming method in the present embodiment.
When molten-state magnesium-alloy material is filled into the product section
5, the die
1 removes heat from the magnesium-alloy material, so that
the magnesium ally material is cooled and solidified. Thus, the molded product
50 (FIG. 2) is formed in the product section
5 of the die
1.
The female screw section
31 is drawn while being rotated from the molded
product
50 after the magnesium-alloy material is cooled to a predetermined
temperature and solidified.
At least the vicinity of the product section
5 of the die
1 is
temperature-controlled
at a predetermined temperature by the heater
27 and the temperature sensor
28 before the molten magnesium alloy material is filled. The predetermined
temperature is 200° C., for example. A molten magnesium-alloy material is
filled into the die
1, so that temperature of the die
1 is once quickly
increased. Subsequently, temperature of the die
1 decreases to the predetermined
temperature (200° C. in this embodiment). Temperature of the die
1
is measured by the temperature sensor
28 while the die
1 is cooled
down. The female-thread forming section
31 is drawn while being rotated
from the molded product
50 after the temperature of the die
1 is
decreased to the predetermined temperature.
The driving motor
23 drives the screw-shaped pin
30 via the engaged
gears
23a,
33. As shown in FIG. 6, the screw-shaped pin
30
is rotated, so that the screw-shaped pin
30 is moved to left in FIG. 6 by
a rotation-sliding mechanism, which is constructed with the guide section
22
and the screw section
32. The screw pitch of the rotation-sliding mechanism
is the same as the screw pitch of the female-thread forming section
31.
Therefore, the female-thread forming section
31 is drawn to left in FIG.
6, while being rotated along the female thread
53 formed in the solidified
molded product
50.
As shown in FIG. 7, the movable die
12 is moved so that the die
1
is opened after the female-thread forming section
31 is completely drawn
from the molded product
50 (i.e., product section
5). As shown in
FIG. 8, the ejector pins
21 are moved to right in FIG. 6, so that the molded
product
50 and a solidified member molded in the supplying passage are removed
from the movable die
12.
The solidified member molded in the supplying passage is cut at a position corresponding
to the gate section
4, and removed from the molded product
50. Thus,
the molded product
50 having the female thread
53 (FIG. 2) is obtained.
The position of the screw-shaped pin
30 and the ejector pins
21 are
reset to an initial position as shown in FIG. 3 after removing the molded product
50 or the like. Subsequently, the die
1 is used in the next molding process.
Preferably, when the above forming cycle is repeated, forming process
condition is uniformed in the substantially same condition. Especially, it is preferable
that the starting temperature of the drawing of the thread-shaped pin
30
is uniformly adjusted. According to the forming process in this embodiment, the
female-thread forming section
31 is used for drawing the thread-shaped pin
30 from the molded product
50. The female-thread forming section
31 is commonly used for plural forming processes. Namely, the dimension
of the female-thread forming section
31 can be uniformed for plural forming
processes. Accordingly, variation can be decreased in the dimension of the female
thread
53 among plural molded products
50.
Here, an application process is shown in FIG. 3. A filling process is shown
in FIG. 5. The filled metallic material shown in FIG. 5 is cooled and solidified
in a solidification process. A thread-drawing process is shown in FIG. 6.
When the above forming process is repeated, a cooling process is performed in
advance of the filling process. The thread-shaped pin
30 is cooled in the
cooling process. In the above forming cycle, the thread-shaped pin
30 is
in the position shown in FIG. 9, and closes the downstream end of the fluid passage
25 in the sliding hole
24 in the processes shown in FIGS. 3 to 5.
Subsequently, as shown in FIG. 10, the downstream end of the fluid passage
25
is opened to the sliding hole
24 after the thread-shaped pin
30 is
drawn and the molded product
50 is removed. The downstream end of the fluid
passage
25 is communicated with the product section
5 and the exterior
of the product section
5 through a thread section of the female-thread forming
section
31. Liquid-form mold lubricant is discharged from the fluid nozzle
26, and flows along the thread section of the female-thread forming section
31. Thus, the mold lubricant is applied over the female-thread forming section
31 while cooling the female-thread forming section
31. Therefore,
the female forming section
31 can be easily cooled.
The thread-shaped pin
30 is an individual component with respect to the
movable die
12. Temperature of the female-thread forming section
31
of the thread-shaped pin
30 is apt to be increased. However, the female-thread
forming section
31 can be steadily cooled, so that temperature of the female-thread
forming section
31 becomes low, for example 200° C. Therefore, reactivity
can be decreased between the female-thread forming section
31 and a molten
magnesium alloy material after the filling process. The applied mold lubricant
decreases friction between the female-thread forming section
31 and the
female thread
53 of the molded product
50 in the thread-drawing process,
so that the molded product
50 can be easily removed from the die
1.
The mold lubricant is applied to the inner plane of the sliding hole
24,
so that lubrication between the sliding hole
24 and the thread-shaped pin
30 can be maintained.
The above process is the cooling process perform d in advance of the filling
process. Preferably, the cooling temperature is set below 300° C. The inventors
confirmed that sticking between the female-thread forming section
31 and
the female thread
53 is not apt to occur in the case that the cooling temperature
is below 300° C., compared with the case that the cooling temperature is above
300° C.
In the above construction and the forming process, a molten magnesium-alloy material
is filled into the die I in the filling process. A magnesium-alloy material has
a characteristic, such that the magnesium-alloy material is not apt to stick to
a steel material compared with an aluminum-alloy material or the like. The steel
material is generally used for a die. Therefore, a magnesium-alloy material is
not apt to stick to the die
1, especially the female-thread forming section
31 of the thread-shaped pin
30.
A magnesium-alloy material, such as AZ91D or the like, includes several percent
of aluminum for enhancing corrosion resistance and strength. However, the ceramic
material layer is formed on the surface of the female-thread forming section
31.
Besides, mold lubricant is applied to the inside plane of the product section
5,
especially the female-thread forming section
31, in advance of the filling
process. Therefore, even if aluminum material, which is apt to stick to a steel
material, is included in the magnesium-alloy material, contact can be prevented
between the die material (i.e., the steel material) and the aluminum material included
in the magnesium alloy material.
The female-thread forming section
31 is steadily cooled in the cooling
process, in advance of the filling process. Therefore, even if the aluminum material
included in the magnesium alloy material contacts the die material of the female-thread
forming section
31, sticking is not apt to occur.
Thus, it is not necessary to individually form the female thread
53
of the molded product
50 in another process, such as a machining work process.
Besides, the female-thread section
53 can be steadily formed when the molded
product
50 is formed.
Conventionally, similar product is molded of resin, and a female
screw section is formed as a connecting section at the same time. However, it is
difficult to secure connecting strength in this resinous molding. Otherwise, insert
molding process or press insertion process is used when high strength is required
for the connecting section. Here, a metallic part having a female thread is inserted
by a molding material, such as resin, in the insert molding process. A metallic
part having a female thread is press-inserted into a component in the press-insertion
process. However, both the insert molding process and the press insertion process
have complicated processes. On the contrary, in this embodiment, a female screw
can be steadily formed without complicated process. Accordingly, the process in
this embodiment is significantly effective in cost reduction or the like.
[Other Embodiment]
The fluid, which is discharged from the fluid-nozzle
26, is not limited
to mold lubricant. Other fluid, which cools the female-thread forming section
31,
can be substituted for the mold lubricant. Antifriction can be used for cooling
and lubricating. Air, especially cooled air, or water can be used for cooling,
for example.
The temperature control means is not limited to the heater
27. A heat
medium piping can be provided in the die
1, for example. In detail, heat
medium, such as oil, air, and water is circulated inside the heat medium piping,
so that the die
1 is heated, and temperature of the die
1 is controlled.
The die-opening force can be converted into a rotational force using a specific
mechanism,
60 that the die can be opened while drawing the thread-shaped section.
A thixotropic molding, in which semiliquid state magnesium alloy is injection-molded,
can be used for the forming process. Die-casting, squeeze casting, low-pressure
casting, gravity casting, and the like can be also used for the forming process.
As long as the forming process uses a die, the present invention can be used.
Various modifications and alternation may be made to the above embodiments
without departing from the spirit of the present invention.
*
