U.S. patent application number 16/295492 was filed with the patent office on 2020-05-14 for die casting machine and control method thereof.
This patent application is currently assigned to TOYO MACHINERY & METAL CO., LTD.. The applicant listed for this patent is TOYO MACHINERY & METAL CO., LTD.. Invention is credited to Fumitaka ISHIBASHI, Masaya KITA, Akihiro YAMANAKA.
Application Number | 20200147679 16/295492 |
Document ID | / |
Family ID | 67883005 |
Filed Date | 2020-05-14 |
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United States Patent
Application |
20200147679 |
Kind Code |
A1 |
ISHIBASHI; Fumitaka ; et
al. |
May 14, 2020 |
DIE CASTING MACHINE AND CONTROL METHOD THEREOF
Abstract
Provided is a die casting machine and die casting machine
control method that are able to change the operation of a plunger
at an appropriate timing. A die casting machine operates a plunger
such that the plunger moves forward, detects that molten metal
extruded from a sleeve by the forward movement of the plunger has
arrived at a cavity, determines a deceleration starting position
and a intensification starting position for changing the operation
of the plunger, using, as a reference (reference position Ls), the
position of the plunger 15 at the time when it is detected that
molten metal has arrived at the cavity, and, when the plunger moves
to the deceleration starting position and intensification starting
position, changes the operation of the plunger to operations
corresponding to the respective positions.
Inventors: |
ISHIBASHI; Fumitaka;
(Akashi-shi, JP) ; KITA; Masaya; (Akashi-shi,
JP) ; YAMANAKA; Akihiro; (Akashi-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYO MACHINERY & METAL CO., LTD. |
Akashi-shi |
|
JP |
|
|
Assignee: |
TOYO MACHINERY & METAL CO.,
LTD.
Akashi-shi
JP
|
Family ID: |
67883005 |
Appl. No.: |
16/295492 |
Filed: |
March 7, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22D 17/203 20130101;
B22D 17/2023 20130101; B22D 17/04 20130101; B22D 17/32
20130101 |
International
Class: |
B22D 17/32 20060101
B22D017/32; B22D 17/04 20060101 B22D017/04; B22D 17/20 20060101
B22D017/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 7, 2018 |
JP |
2018-041223 |
Claims
1. A die casting machine comprising: a sleeve into which molten
metal to be injected to a cavity of a mold is poured; a plunger
housed in the sleeve; an arrival detector configured to detect that
molten metal extruded from the sleeve by a forward movement of the
plunger has arrived at the cavity; an operation change position
determination unit configured to determine an operation change
position for changing an operation of the plunger, using, as a
reference, a position of the plunger at the time when the arrival
detector detects that molten metal has arrived at the cavity; and
an operation controller configured to operate the plunger such that
the plunger moves forward and to, when the plunger moves to the
operation change position, change the operation of the plunger.
2. The die casting machine of claim 1, further comprising: a piston
connected to the plunger and configured to move by hydraulic
pressure; and a cylinder housing the piston, wherein the operation
controller operates the plunger by controlling supply of hydraulic
oil to a rear oil chamber of the cylinder and discharge of
hydraulic oil from a front oil chamber of the cylinder, and the
arrival detector detects that molten metal has arrived at the
cavity, on the basis of a change in hydraulic pressure of the front
oil chamber.
3. The die casting machine of claim 1, wherein the arrival detector
detects that molten metal has arrived at the cavity, on the basis
of a change in speed of the plunger.
4. The die casting machine of claim 1, wherein the arrival detector
detects that molten metal has arrived at the cavity, within a
predetermined monitoring range set with respect to the position of
the plunger or the time during which the plunger is operating.
5. The die casting machine of claim 1, wherein the operation change
position is a deceleration starting position, and the operation
controller decelerates the plunger when the plunger moves to the
deceleration starting position.
6. The die casting machine of claim 1, wherein the operation change
position is an intensification starting position, and the operation
controller changes the operation of the plunger to an
intensification operation when the plunger moves to the
intensification position.
7. A method for controlling a die casting machine, the die casting
machine including a sleeve into which molten metal to be injected
to a cavity of a mold is poured and a plunger housed in the sleeve,
the method comprising: operating the plunger such that the plunger
moves forward; detecting that molten metal extruded from the sleeve
by a forward movement of the plunger has arrived at the cavity;
determining an operation change position for changing an operation
of the plunger, using, as a reference, a position of the plunger at
the time when it is detected that molten metal has arrived at the
cavity; and when the plunger moves to the operation change
position, changing the operation of the plunger.
Description
TECHNICAL FIELD
[0001] The present invention relates to a die casting machine and a
method for controlling a die casting machine.
BACKGROUND ART
[0002] Japanese Unexamined Patent Application Publication No.
2008-126294 discloses a conventional die casting machine. This die
casting machine has a low-speed injection process and high-speed
injection process, in which injection operations are performed, and
an intensification process, in which an intensification operation
is performed. The die casting machine changes the low-speed
injection process to the high-speed injection process at the timing
when the forward movement position of an injection plunger has
moved forward by a distance set in the low-speed injection process.
Upon detecting that the injection plunger has moved to a
predetermined forward movement position, the die casting machine
changes speed feedback control along the position axis to pressure
feedback control along the time axis.
SUMMARY OF INVENTION
[0003] The above die casting machine injects molten metal poured
into a sleeve, into a cavity of molds using a plunger so that the
cavity is filled with the molten metal. However, if the molten
metal overflows the sleeve for some reason or adheres to the inside
of a ladle when poured into the sleeve, the amount of molten metal
in the sleeve varies. Accordingly, if the operation of the plunger
is changed using, as a reference, the absolute position of the
plunger with the amount of molten metal varying, the amount of
molten metal in the cavity also varies. That is, the operation of
the plunger may be changed at an inappropriate timing, resulting in
destabilization of the quality of the molded product.
[0004] In view of the foregoing, an object of the present invention
is to provide a die casting machine and die casting machine control
method that are able to change the operation of a plunger at an
appropriate timing.
[0005] To achieve the above object, a die casting machine according
to an aspect of the present invention includes a sleeve into which
molten metal to be injected to a cavity of a mold is poured, a
plunger housed in the sleeve, an arrival detector configured to
detect that molten metal extruded from the sleeve by a forward
movement of the plunger has arrived at the cavity, an operation
change position determination unit configured to determine an
operation change position for changing an operation of the plunger,
using, as a reference, a position of the plunger at the time when
the arrival detector detects that molten metal has arrived at the
cavity, and an operation controller configured to operate the
plunger such that the plunger moves forward and to, when the
plunger moves to the operation change position, change the
operation of the plunger.
[0006] Preferably, the die casting machine of the present invention
further includes a piston connected to the plunger and configured
to move by hydraulic pressure and a cylinder housing the piston,
the operation controller operates the plunger by controlling supply
of hydraulic oil to a rear oil chamber of the cylinder and
discharge of hydraulic oil from a front oil chamber of the
cylinder, and the arrival detector detects that molten metal has
arrived at the cavity, on the basis of a change in hydraulic
pressure of the front oil chamber.
[0007] In the present invention, the arrival detector preferably
detects that molten metal has arrived at the cavity, on the basis
of a change in speed of the plunger.
[0008] In the present invention, the arrival detector preferably
detects that molten metal has arrived at the cavity, within a
predetermined monitoring range set with respect to the position of
the plunger or the time during which the plunger is operating.
[0009] In the present invention, preferably, the operation change
position is a deceleration starting position, and the operation
controller decelerates the plunger when the plunger moves to the
deceleration starting position.
[0010] In the present invention, preferably, the operation change
position is an intensification starting position, and the operation
controller changes the operation of the plunger to an
intensification operation when the plunger moves to the
intensification position.
[0011] To achieve the above object, another aspect of the present
invention provides a method for controlling a die casting machine,
the die casting machine including a sleeve into which molten metal
to be injected to a cavity of a mold is poured and a plunger housed
in the sleeve. The method includes operating the plunger such that
the plunger moves forward, detecting that molten metal extruded
from the sleeve by a forward movement of the plunger has arrived at
the cavity, determining an operation change position for changing
an operation of the plunger, using, as a reference, a position of
the plunger at the time when it is detected that molten metal has
arrived at the cavity, and when the plunger moves to the operation
change position, changing the operation of the plunger.
[0012] According to the present invention, the plunger is operated
such that the plunger moves forward, it is detected that the molten
metal extruded from the sleeve by the forward movement of the
plunger has arrived at the cavity of the mold, the operation change
position for changing the operation of the plunger is determined
using, as a reference, the position of the plunger at the time when
it is detected* that the molten metal has arrived at the cavity,
and the operation of the plunger is changed when the plunger moves
to the operation change position. Since the volume of the cavity is
constant, the amount of molten metal to be extruded after the
molten metal has arrived at the cavity is also predetermined. For
this reason, the position of the plunger at the time when the
molten metal has arrived at the cavity is defined as the reference
position, and the operation change position corresponding to the
volume of the cavity is determined relative to the reference
position. Thus, the operation of the plunger can be changed at an
appropriate timing regardless of variations in the amount of molten
metal in the sleeve. As a result, the quality of the product can be
effectively stabilized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a drawing showing a schematic configuration of a
die casting machine according to an embodiment of the present
invention;
[0014] FIG. 2 is a sectional view of a die plate and its vicinity
of the die casting machine in FIG. 1;
[0015] FIG. 3 is a diagram showing function blocks of a controller
of the die casting machine in FIG. 1;
[0016] FIG. 4 is a flowchart showing an example of a process
according to the present invention performed by the controller in
FIG. 3;
[0017] FIG. 5 is an enlarged sectional view of a cavity and its
vicinity of molds and is a drawing showing a state in which molten
metal has been poured into a sleeve;
[0018] FIG. 6 is an enlarged sectional view of the cavity and its
vicinity of the molds and is a drawing showing a state in which a
plunger has moved to a high-speed forward movement starting
position;
[0019] FIG. 7 is an enlarged sectional view of the cavity and its
vicinity of the molds and is a drawing showing a state in which the
molten metal has arrived at the cavity;
[0020] FIG. 8 is an enlarged sectional view of the cavity and its
vicinity of the molds and is a drawing showing a state in which the
plunger has moved to a deceleration starting position;
[0021] FIG. 9 is an enlarged sectional view of the cavity and its
vicinity of the molds and is a drawing showing a state in which the
plunger has moved to an intensification starting position;
[0022] FIG. 10 is a graph showing an example of changes in the
hydraulic pressures of front and rear oil chambers of a cylinder
and changes in the speed of the plunger in injection process and an
intensification process (a configuration that detects the molten
metal has arrived at the cavity, on the basis of a change in the
hydraulic pressure of the front oil chamber); and
[0023] FIG. 11 is a graph showing an example of changes in the
hydraulic pressures of the front and rear oil chambers of the
cylinder and changes in the speed of the plunger in the injection
process and intensification process (a configuration that detects
the molten metal has arrived at the cavity, on the basis of a
change in the speed of the plunger).
DESCRIPTION OF EMBODIMENTS
[0024] Now, a die casting machine according to an embodiment of the
present invention will be described with reference to FIGS. 1 to
10.
[0025] FIG. 1 is a drawing showing a schematic configuration of the
die casting machine according to the embodiment of the present
invention. FIG. 2 is a sectional view of a die plate and its
vicinity of the die casting machine in FIG. 1. FIG. 3 is a diagram
showing function blocks of a controller of the die casting machine
in FIG. 1. FIG. 4 is a flowchart showing an example of a process
according to the present invention performed by the controller in
FIG. 3. FIGS. 5 to 9 are enlarged sectional views of a cavity and
its vicinity of molds and are drawings showing (1) a state in which
molten metal has been poured into a sleeve, (2) a state in which a
plunger has moved to a high-speed forward movement starting
position, (3) a state in which the molten metal has arrived at the
cavity, (4) a state in which the plunger has moved to a
deceleration starting position, and (5) a state in which the
plunger has moved to an intensification starting position,
respectively. FIG. 10 is a graph schematically showing an example
of changes in the hydraulic pressures of front and rear oil
chambers of a cylinder and changes in the speed of the plunger in
injection process and an intensification process (a configuration
that detects the molten metal has arrived at the cavity, on the
basis of a change in the hydraulic pressure of the front oil
chamber). In the present specification, the left side of FIGS. 1,
2, and 5 to 9 is defined as the front side, and the right side
thereof is defined as the rear side.
[0026] As shown in FIG. 1, a die casting machine 1 according to the
present embodiment includes a piston 11 that moves by hydraulic
pressure and a cylinder 12 that houses the piston 11 such that the
piston 11 can move in the front-rear direction. The cylinder 12 has
a rear oil chamber 13 and a front oil chamber 14 separated by the
piston 11. A plunger 15 is connected to the piston 11. The plunger
15 includes a rod 16 that extends forward from the front surface
11a of the piston 11 and a plunger tip 17 disposed on an end of the
rod 16. The plunger 15 is inserted into a sleeve 33 (FIG. 2) of a
fixed die plate 31 so as to be able to move back and forth.
[0027] A drive transmission plate 18 is disposed behind the
cylinder 12. The drive transmission plate 18 is moved back and
forth by an electric servo motor 19 and a drive transmission
mechanism 20 including a drive transmission gear, a ball screw
mechanism, and the like. Once it is moved forward, the drive
transmission plate presses and moves forward the cylinder 12. The
drive transmission plate 18, electric servo motor 19, and drive
transmission mechanism 20 form a motor-driven intensification
mechanism. Instead of such a motor-driven intensification
mechanism, there may be used a hydraulic intensification mechanism
that presses and moves forward the cylinder 12 by hydraulic
pressure.
[0028] The die casting machine 1 includes an accumulator 21 serving
as an hydraulic pressure supplier that supplies hydraulic oil to
the rear oil chamber 13 of the cylinder 12. The accumulator 21 and
the rear oil chamber 13 of the cylinder 12 are connected through an
oil passage a. A supply valve 22 is disposed on the oil passage a.
The supply valve 22 establishes and blocks communication between
the accumulator 21 and rear oil chamber 13. In the present
embodiment, the supply valve 22 consists of an electromagnetic
valve that drives a valve using a solenoid. The supply valve 22 may
be a valve of a type other than an electromagnetic valve, for
example, one that drives a valve using a motor.
[0029] The front oil chamber 14 of the cylinder 12 and a tank 23
that stores hydraulic oil are connected through an oil passage b. A
servo valve 24 is disposed on the oil passage b. The servo valve 24
adjusts the amount of hydraulic oil discharged from the front oil
chamber 14 to the tank 23, on the basis of the degree of opening.
In the present embodiment, the speed at which the plunger 15 moves
forward, or the like is controlled by adjusting the amount of
hydraulic oil discharged from the front oil chamber 14 using the
servo valve 24 (meter-out control) Note that the supply valve 22
may be a servo valve and the speed at which the plunger 15 moves
forward, or the like may be controlled by adjusting the amount of
hydraulic oil supplied from the accumulator 21 to the rear oil
chamber 13 using the servo valve (meter-in control).
[0030] The die casting machine 1 also includes an hydraulic
pressure sensor 25 that outputs a signal corresponding to the
hydraulic pressure Pf of the front oil chamber 14 of the cylinder
12 and a position sensor 26 that outputs a signal corresponding to
the position L of the plunger 15. The position sensor 26 may be a
known position sensor, such as optical, magnetic, or
magnetostriction type.
[0031] As shown in FIG. 2, the die casting machine also 1 includes
a fixed die plate 31 having a fixed mold K1 mounted thereon and a
movable die plate 32 having a moving mold K2 mounted thereon. The
fixed die plate 31 includes the cylindrical sleeve 33 that
communicates with an runner R of the fixed mold K1. The sleeve 33
has an inlet 34 formed in an upper portion thereof, and molten
metal M is poured into the sleeve 33 through the inlet 34 using a
ladle (not shown). The die casting machine 1 opens and closes the
fixed mold K1 and moving mold K2 by moving the movable die plate 32
back and forth with respect to the fixed die plate 31 using a mold
closure drive unit (not shown).
[0032] The closed fixed mold K1 and moving mold K2 form therewithin
the runner R communicating with the sleeve 33, a cavity C
communicating with the runner R, and an overflow portion
communicating with the cavity C. The cavity C-side end of the
runner R has smaller diameters at positions closer to the cavity C
and communicates with a gate G open to the cavity C. Thus, the
molten metal M passes through the gate G when flowing from the
runner R into the cavity C, increasing the flow resistance
thereof.
[0033] The die casting machine 1 also includes a controller 40 that
controls the overall operation. The controller 40 includes, for
example, a microcomputer for built-in devices that includes a CPU,
a ROM, a RAM, an EEPROM, and I/O interfaces. The controller 40
controls the operation of the accumulator 21, supply valve 22, and
servo valve 24. The controller 40 also detects the hydraulic
pressure Pf of the front oil chamber 14 on the basis of a signal
outputted from the hydraulic pressure sensor 25. The controller 40
also detects the position L and the speed V of the plunger 15 on
the basis of a signal outputted from the position sensor 26. The
controller 40 also controls the operation of the drive units in the
process, such as a mold closing process, a metal pouring process,
injection process (low-speed injection process and high-speed
injection process), an intensification process, a mold opening
process, and a product ejection process.
[0034] The CPU of the controller 40 functions as a hydraulic
pressure detector 41, a position/speed detector 42, an arrival
detector 43, an operation change position determination unit 44,
and an operation controller 45 by executing a control program
stored in the ROM.
[0035] The hydraulic pressure detector 41 detects the hydraulic
pressure Pf of the front oil chamber 14 on the basis of a signal
outputted from the hydraulic pressure sensor 25. The position/speed
detector 42 detects the position L and speed V of the plunger 15 on
the basis of a signal outputted from the position sensor 26.
[0036] The arrival detector 43 detects that the molten metal M has
arrived at the cavity C (that is, the top of the molten metal M has
passed through the gate G) by the forward movement of the plunger
15.
[0037] Specifically, the arrival detector 43 monitors the hydraulic
pressure Pf of the front oil chamber 14 detected by the hydraulic
pressure detector 41 while the position L of the plunger 15 is in a
predetermined monitoring range Lw. The monitoring range Lw is set
according to the system or molds, for example, is set to a range
from a position (starting position La) ahead of a position L0 (not
shown) by A mm, the position L0 being a position in which the
plunger 15 starts to move forward, to a position (ending position
Lb) ahead of the starting position La by B mm. Note that the
monitoring range Lw does not have to be set. When the arrival
detector 43 detects that the hydraulic pressure Pf of the front oil
chamber 14 has become a lower value than the no-load-time hydraulic
pressure P0 of the front oil chamber 14 by a predetermined
percentage .alpha. (Pf.ltoreq.P0.times.(1-.alpha.),
0<.alpha.<100%, e.g., .alpha.=20%) or more, it determines
that the molten metal M has arrived at the cavity C. The reason is
as follows: when the top of the molten metal M passes through the
gate G, the flow resistance increases and thus a load (pressure) is
applied to the plunger 15; and the hydraulic pressure Pf of the
front oil chamber 14 is reduced so that the hydraulic pressure Pf
and the hydraulic pressure Pb of the rear oil chamber 13 are
balanced in the load-applied plunger 15.
[0038] Instead of setting the monitoring range Lw with respect to
the position of the plunger 15, the arrival detector 43 may set a
monitoring range Tw with respect to the time T during which the
plunger 15 is operating. The monitoring range Tw is set according
to the system or mold, for example, is set to D sec (until a time
Tb) after a time Ta when C sec elapses after a reference time TO
when the plunger 15 starts to move forward in the low-speed
injection process. As seen above, the monitoring range Lw or
monitoring range Tw in which the hydraulic pressure Pf of the front
oil chamber 14 is monitored is set with respect to the position L
of the plunger 15 or the time during which the plunger 15 is
operating. Thus, the hydraulic pressure Pf can be monitored while
limiting the range to the position or time in which the hydraulic
pressure Pf of the front oil chamber 14 is reduced with a high
probability. As a result, the arrival detector 43 can be prevented
from falsely detecting that the molten metal M has arrived at the
cavity C.
[0039] The no-load-time hydraulic pressure P0 of the front oil
chamber 14 is calculated on the basis of the hydraulic pressure set
for the accumulator 21. The hydraulic pressure Pb of the rear oil
chamber 13 communicating with the accumulator 21 is set to the same
hydraulic pressure as that set for the accumulator 21. The
no-load-time hydraulic pressure P0 of the front oil chamber 14,
which is that when no load is being applied to the plunger 15, can
be calculated by multiplying the hydraulic pressure Pb of the rear
oil chamber 13 by the area ratio between the rear surface 11b and
front surface 11a of the piston 11 [no-load-time hydraulic pressure
P0 of front oil chamber 14=hydraulic pressure Pb of rear oil
chamber 13.times.(area Sb of rear surface 11b/area Sa of front
surface 11a of piston 11)].
[0040] The operation change position determination unit 44
determines the deceleration starting position L2 and
intensification starting position L3 for changing the operation of
the plunger 15, using, as a reference, the position L of the
plunger 15 at the time when the arrival detector 43 detects that
the molten metal M has arrived at the cavity C. The deceleration
starting position L2 and intensification starting position L3 are
operation change positions.
[0041] Specifically, when the arrival detector 43 detects that the
molten metal M has arrived at the cavity C, the operation change
position determination unit 44 acquires the position L (i.e., the
reference position Ls) of the plunger 15 detected by the
position/speed detector 42 at that time (time Ts). Then, on the
basis of the inner diameter of the sleeve 33, the volume of the
cavity C, and the like, the operation change position determination
unit 44 determines the deceleration starting position L2 and the
intensification starting position L3 relative to the reference
position Ls, the deceleration starting position L2 being a position
in which the plunger 15 is decelerated in the high-speed injection
process, the intensification starting position L3 being a position
in which speed control over the operation of the plunger 15 is
changed to pressure control and a intensification operation is
started.
[0042] The deceleration starting position L2 is, for example, a
position in which the entire cavity C is filled with the molten
metal M. If the amount of molten metal M extruded from the sleeve
33 becomes equal to the volume of the cavity C when the plunger 15
moves from the reference position Ls by the distance D2, the
deceleration starting position L2 is set to a position ahead of the
reference position Ls by the distance D2.
[0043] The intensification starting position L3 is, for example, a
position in which the entire cavity C and overflow portion O are
filled with the molten metal M. If the amount of molten metal M
extruded from the sleeve 33 becomes equal to the total volume of
the cavity C and overflow portion O when the plunger 15 moves from
the reference position Ls by the distance D3, the intensification
starting position L3 is set to a position ahead of the reference
position Ls by the distance D3.
[0044] The operation controller 45 operates the plunger 15 such
that the plunger 15 moves forward. Also, when the plunger 15 moves
to the high-speed forward movement starting position L1,
deceleration starting position L2, or intensification starting
position L3, the operation controller 45 changes the operation of
the plunger 15 to an operation corresponding to that position. The
high-speed forward movement starting position L1 is preset.
[0045] Specifically, the operation controller 45 operates the
plunger 15 by setting the hydraulic pressure of the accumulator 21,
opening the supply valve 22, and adjusting the degree of opening of
the servo valve 24 to control the supply of the hydraulic oil to
the rear oil chamber 13 of the cylinder 12 and the discharge of the
hydraulic oil from the front oil chamber 14 of the cylinder 12.
[0046] As a series of product molding operations, the die casting
machine 1 first closes the fixed mold K1 and moving mold K2 by
driving the movable die plate 32 (mold closing process). Then, the
molten metal M is poured into the sleeve 33 of the fixed die plate
31 (metal pouring process). Then, the die casting machine 1 moves
the piston 11 forward by increasing the hydraulic pressure of the
hydraulic oil in the accumulator 21, opening the supply valve 22 to
supply the hydraulic oil to the rear oil chamber 13 of the cylinder
12, and opening the servo valve 24 to discharge the hydraulic oil
from the front oil chamber 14. At this time, the die casting
machine 1 adjusts the amount of hydraulic oil to be discharged, on
the basis of the degree of opening of the servo valve 24, moves the
piston 11 forward at low speed and then at high speed, injects the
molten metal M from the sleeve 33 into the cavity C using the
plunger 15 so that the cavity is filled with the molten metal
(low-speed injection process, high-speed injection process). The
die casting machine 1 also presses the cylinder 12 (i.e., piston
11) by driving the electric servo motor to move the drive
transmission plate 18 forward (intensification process). The die
casting machine 1 then opens the fixed mold K1 and moving mold K2
by driving the movable die plate 32 (mold opening process) and
ejects a product from the cavity C (product ejection process).
[0047] Next, as a method for controlling the die casting machine 1
of the present embodiment, an example of a process according to the
present invention performed by the controller 40 will be described
with reference to a flowchart of FIG. 4 and FIGS. 5 to 10. This
process is performed in the low-speed injection process and
high-speed injection process.
[0048] As shown in FIG. 5, after the molten metal is poured into
the sleeve 33 in the metal pouring process, the controller 40
starts the low-speed injection process to operate the plunger such
that the plunger moves forward at low speed (S110). Specifically,
the controller 40 increases the pressure of the hydraulic oil in
the accumulator 21 by setting the hydraulic pressure of the
accumulator 21, then supplies the hydraulic oil to the rear oil
chamber 13 of the cylinder 12 by opening the supply valve 22, and
then discharges the hydraulic oil from the front oil chamber 14 by
adjusting the degree of opening of the servo valve 24, Thus, the
plunger 15 connected to the piston 11 moves forward from the
position L0 as the starting point at low speed (e.g., 0.5
m/sec).
[0049] The controller 40 then waits until the plunger 15 moves to
the high-speed forward movement starting position L1 (N in S120).
When the plunger 15 moves to the high-speed forward movement
starting position L1, as shown in FIG. 6 (Y in S120), the
controller 40 starts the high-speed injection process to operate
the plunger such that the plunger moves forward at high speed
(S130). Specifically, the controller 40 increases the amount of
hydraulic oil to be discharged, by increasing the degree of opening
of the servo valve 24. Thus, the plunger 15 connected to the piston
11 moves forward at high speed (e.g., 2 m/sec).
[0050] The controller 40 then waits until the position of the
plunger 15 moves to the predetermined monitoring range Lw (N in
S140). When the plunger 15 moves to the starting position La of the
monitoring range Lw (Y in S140), the controller 40 monitors the
hydraulic pressure Pf of the front oil chamber 14 on the basis of a
signal outputted by the hydraulic pressure sensor 25 until the
plunger 15 moves to the ending position Lb of the monitoring range
Lw (S150).
[0051] The controller 40 then detects that the molten metal M
extruded from the sleeve 33 by the forward movement of the plunger
15 has arrived at the cavity (S160). Specifically, the controller
40 waits until the hydraulic pressure Pf of the front oil chamber
14 becomes a lower value than the no-load-time hydraulic pressure
P0 by the predetermined percentage .alpha. or more (N in S160).
When the hydraulic pressure Pf of the front oil chamber 14 becomes
a lower value than the no-load-time hydraulic pressure P0 by the
predetermined percentage .alpha. or more
(Pf.ltoreq.P0.times.(1-.alpha.), Y in S160), as shown in the graph
of FIG. 10, the controller 40 determines the then (time Ts)
position L of the plunger 15 as the reference position Ls, as shown
in FIG. 7. The controller 40 also determines a position ahead of
the reference position Ls by the deceleration starting distance D2
as the deceleration starting position L2 and a position ahead of
the reference position Ls by the intensification starting distance
D3 as the intensification starting position L3 (S170).
[0052] The controller 40 then waits until the plunger 15 moves to
the deceleration starting position L2 (N in S180). When the plunger
15 moves to the deceleration starting position L2, as shown in FIG.
8 (Y in S180), the controller 40 decelerates the plunger 15 (S190).
Specifically, the controller 40 reduces the amount of hydraulic oil
to be discharged, by reducing the degree of opening of the servo
valve 24. Thus, the controller 40 decelerates the plunger 15
connected to the piston 11.
[0053] The controller 40 then waits until the plunger 15 moves to
the intensification starting position L3 (N in S120). When the
plunger moves to the intensification starting position L3, as shown
in FIG. 9 (Y in S200), the controller 40 changes the operation of
the plunger from the injection operation to a intensification
operation (S210). Specifically, the controller 40 operates the
cylinder 12 such that the cylinder 12 moves forward, using the
motor-driven intensification mechanism (drive transmission plate
18, electric servo motor 19, and drive transmission mechanism 20)
and changes the speed feedback control along the position axis
(speed control) to pressure feedback control along the time axis
(pressure control). Thus, the controller 40 changes the operation
of the plunger 15 from the injection operation to a intensification
operation and starts the intensification operation, ending the
process of the flowchart. Thereafter, the controller 40 performs
the operations in the intensification process, mold opening
process, and product ejection process.
[0054] As seen above, the die casting machine 1 according to the
present embodiment operates the plunger 15 such that the plunger 15
moves forward, detects that the molten metal M extruded from the
sleeve 33 by the forward movement of the plunger 15 has arrived at
the cavity C, determines the deceleration starting position L2 and
intensification starting position L3 for changing the operation of
the plunger 15, using, as a reference, the position L (reference
position Ls) of the plunger 15 at the time when it is detected that
the molten metal M has arrived at the cavity C, and, when the
plunger 15 moves to the deceleration starting position L2 or
intensification starting position L3, changes the operation of the
plunger 15 to an operation corresponding to that position. Since
the volume of the cavity C is constant, the amount of molten metal
M to be extruded after the molten metal M has arrived at the cavity
C is also predetermined. For this reason, the die casting machine 1
determines the position L of the plunger 15 at the time when the
molten metal has arrived at the cavity C, as the reference position
Ls and determines the deceleration starting position L2 and
intensification starting position L3 relative to the reference
position Ls, in accordance with the volume of the cavity C. Thus,
the die casting machine 1 is able to change the operation of the
plunger 15 at an appropriate timing regardless of variations in the
amount of molten metal M in the sleeve 33 and thus to effectively
stabilize the quality of the product.
[0055] The die casting machine 1 includes the piston 11 that is
connected to the plunger 15 and operates by hydraulic pressure and
the cylinder 12 housing the piston 11. The operation controller 45
of the controller 40 operates the plunger 15 by controlling the
supply of the hydraulic oil to the rear oil chamber 13 of the
cylinder 12 and the discharge of the hydraulic oil from the front
oil chamber 14 of the cylinder 12. The arrival detector 43 of the
controller 40 detects that the molten metal M has arrived at the
cavity C, on the basis of a change in the hydraulic pressure of the
front oil chamber 14. Using such a relatively simple configuration,
the die casting machine 1 is able to accurately detect that the
molten metal M has arrived at the cavity C.
[0056] The arrival detector 43 detects that the molten metal M has
arrived at the cavity C, in the monitoring range Lw set with
respect to the position L of the plunger 15. By doing so, a
position range of the plunger 15 in which the molten metal M is
predicted to arrive at the cavity C is set as the monitoring range
Lw considering variations in the amount of molten metal M in the
sleeve 33. Thus, it is possible to increase the accuracy with which
it is detected that the molten metal M has arrived at the cavity
C.
[0057] When the plunger 15 moves to the deceleration starting
position L2, the operation controller 45 decelerates the plunger
15; when the plunger 15 moves to the intensification starting
position L3, the operation controller 45 changes the operation of
the plunger 15 to an intensification operation. As seen above, the
operation controller 45 is able to change the operation of the
plunger 15 to the deceleration operation or intensification
operation at an appropriate timing.
[0058] While, in the above embodiment, when the arrival detector 43
detects that the hydraulic pressure Pf of the front oil chamber 14
has become a lower value than the no-load-time hydraulic pressure
P0 of the front oil chamber 14 by the predetermined percentage
.alpha. or more, it detects that the molten metal M has arrived at
the cavity C, this configuration does not have to be used. For
example, the arrival detector 43 may detect that the molten metal M
has arrived at the cavity C, on the basis of a change in the speed
of the plunger 15. Specifically, as schematically shown in FIG. 11,
when the arrival detector 43 detects that the speed V of the
plunger 15 becomes a lower value than the target speed V0 by a
predetermined percentage .beta. or more
(V.ltoreq.V0.times.(1-.beta.), 0<.beta.<100%), it may detect
that the molten metal M has arrived at the cavity C. The reason is
as follows: when the top of the molten metal M passes through the
gate G, the flow resistance increases and thus a load (pressure) is
applied to the plunger 15; and the hydraulic pressure Pf of the
front oil chamber 14 is reduced so that the hydraulic pressure Pf
and the hydraulic pressure Pb of the rear oil chamber 13 are
balanced in the load-applied plunger 15, resulting in a reduction
in the speed of the plunger 15. Such a configuration also produces
advantageous effects similar to those of the die casting machine 1
of the above embodiment. The configuration in which the arrival
detector 43 detects that the molten metal M has arrived at the
cavity C may be any configuration without departing from the scope
of the present invention.
[0059] While, in the above embodiment, the injection operation is
performed by hydraulic pressure and the intensification operation
is performed by the electric motor, the present invention may be
applied to any other configuration, such as one in which the
injection operation and the intensification operation are performed
by hydraulic pressure or one in which the injection operation and
intensification operation are performed by an electric motor.
[0060] While the embodiment of the present invention has been
described, the present invention is not limited thereto. Addition
or deletion of components or a design change on the above
embodiment made by those skilled in the art as appropriate and
appropriate combinations of the features of the embodiment are also
included in the present invention without departing from the scope
of the present invention.
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