U.S. patent application number 14/409241 was filed with the patent office on 2015-06-18 for injection apparatus.
This patent application is currently assigned to KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. The applicant listed for this patent is KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. Invention is credited to Kazuki Funahashi, Kazuyuki Yamaguchi.
Application Number | 20150165522 14/409241 |
Document ID | / |
Family ID | 49768574 |
Filed Date | 2015-06-18 |
United States Patent
Application |
20150165522 |
Kind Code |
A1 |
Yamaguchi; Kazuyuki ; et
al. |
June 18, 2015 |
INJECTION APPARATUS
Abstract
In an injection apparatus, a first cylinder and second cylinder
for driving an injection cylinder connected to an injection plunger
are connected in parallel with each other with respect to the
injection cylinder. A piston of the first cylinder and a piston of
the second cylinder are synchronously driven by driving means. A
directional control valve and flow rate adjustment circuit are
provided between one end of the injection cylinder and one end of
the first cylinder.
Inventors: |
Yamaguchi; Kazuyuki; (Aichi,
JP) ; Funahashi; Kazuki; (Aichi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOYOTA JIDOSHOKKI |
Kariya-shi, Aichi |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOYOTA
JIDOSHOKKI
Kariya-shi, Aichi
JP
|
Family ID: |
49768574 |
Appl. No.: |
14/409241 |
Filed: |
May 30, 2013 |
PCT Filed: |
May 30, 2013 |
PCT NO: |
PCT/JP2013/065009 |
371 Date: |
December 18, 2014 |
Current U.S.
Class: |
164/149 |
Current CPC
Class: |
B29C 45/82 20130101;
B22D 17/32 20130101; B22D 17/2038 20130101; B22D 17/10 20130101;
B29C 45/531 20130101; B22D 17/203 20130101; B22D 21/007
20130101 |
International
Class: |
B22D 17/20 20060101
B22D017/20; B22D 21/00 20060101 B22D021/00; B22D 17/32 20060101
B22D017/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2012 |
JP |
2012-139271 |
Claims
1. An injection apparatus, comprising: an injection cylinder
driving an injection plunger to inject a molding material; a first
cylinder connected to the injection cylinder, the first cylinder
feeding hydraulic oil to the injection cylinder and draining
hydraulic oil therefrom; a second cylinder connected to the
injection cylinder in parallel with the first cylinder, the second
cylinder feeding hydraulic oil to the injection cylinder and
draining hydraulic oil therefrom; a single unit of driving means
for reciprocatingly driving a piston of the first cylinder and a
piston of the second cylinder; a directional control valve provided
between one end of the injection cylinder and one end of the first
cylinder, the directional control valve allowing a flow of
hydraulic oil from the first cylinder toward the injection cylinder
but cutting off the flow of hydraulic oil from the injection
cylinder toward the first cylinder; flow rate adjustment means
provided between the directional control valve and the first
cylinder, the flow rate adjustment means being for adjusting a flow
rate of hydraulic oil between the one end of the first cylinder and
the one end of the injection cylinder, and wherein the driving
means drives the piston of the first cylinder and the piston of the
second cylinder in synchronization with each other.
2. The injection apparatus according to claim 1, wherein the flow
rate adjustment means includes: a buffer tank capable of
temporarily storing hydraulic oil; a pilot switching valve capable
of discharging to the buffer tank the hydraulic oil present between
the directional control valve and the first cylinder; and a
replenishment control valve supplying the hydraulic oil in the
buffer tank between the directional control valve and the first
cylinder when there is insufficient hydraulic oil between the
directional control valve and the first cylinder.
3. The injection apparatus according to claim 1, wherein a cylinder
diameter of the first cylinder is greater than that of the second
cylinder.
Description
TECHNICAL FIELD
[0001] The present invention relates to an injection apparatus.
BACKGROUND ART
[0002] Injection apparatuses are known as an apparatus that injects
a molding material into a mold and fills the mold with the molding
material to form a desired product. As in the injection apparatus
disclosed in Patent Document 1, for example, recent injection
apparatuses apply actuating force to an injection cylinder by using
an electric motor. The injection apparatus of Patent Document 1
includes an injection cylinder device for actuating an injection
plunger to inject a molding material into a mold, and a conversion
cylinder device for supplying hydraulic oil to the injection
cylinder device. In the injection apparatus of Patent Document 1,
an electric motor is used as the driving source to drive the
conversion piston of the conversion cylinder device when supplying
the hydraulic oil to the injection cylinder. In the injection
apparatus of Patent Document 1, therefore, the driving force of the
electric motor actuates the conversion piston of the conversion
cylinder device to supply the hydraulic oil to the injection
cylinder device, and then the supplied hydraulic oil actuates the
injection piston of the injection cylinder device in the direction
in which the molding material is to be injected.
PRIOR ART DOCUMENT
Patent Document
[0003] Patent Document 1: Japanese Patent Application Laid Open No.
2010-115683
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0004] However, an injection apparatus is generally actuated in
three steps: a low-speed step, a high-speed step, and a pressure
increasing step. In each of these steps, the injection piston is
actuated at a desired speed to apply a desired pressure to a
molding material inside a cavity. Therefore, actuating the
operating cylinder by the driving force of the electric motor, as
in the injection apparatus of Patent Document 1, enables more
accurate control of the operating quantity of the injection
cylinder than when actuating the operating cylinder by only
controlling the flow rate of the hydraulic oil by means of a
hydraulic pump or the like. However, since the injection apparatus
of Patent Document 1 uses different driving means between the speed
control steps and the pressure control step of the above steps,
driving means are required for the above control steps
respectively. This not only increases the number of parts of the
injection apparatus but also makes the structure of the injection
apparatus complicated and large.
[0005] The present invention was conceived in view of the foregoing
problems, and an object of the present invention is to provide an
injection apparatus capable of realizing high injection speed and
high injection pressure by means of a single unit of driving
means.
Means for Solving the Problem
[0006] In order to solve the above problem, the present invention
includes: an injection cylinder that drives an injection plunger to
inject a molding material; a first cylinder that is connected to
the injection cylinder and feeds hydraulic oil to the injection
cylinder and drains hydraulic oil from the injection cylinder; a
second cylinder that is connected to the injection cylinder in
parallel with the first cylinder and feeds hydraulic oil to the
injection cylinder and drains hydraulic oil from the injection
cylinder; a single unit of driving means for reciprocatingly
driving a piston of the first cylinder and a piston of the second
cylinder; a directional control valve that is provided between one
end of the injection cylinder and one end of the first cylinder and
allows a flow of hydraulic oil from the first cylinder toward the
injection cylinder but cuts off the flow of hydraulic oil from the
injection cylinder toward the first cylinder; and flow rate
adjustment means that is provided between the directional control
valve and the first cylinder and that is for adjusting a flow rate
of hydraulic oil between the one end of the first cylinder and the
one end of the injection cylinder, wherein the driving means drives
the piston of the first cylinder and the piston of the second
cylinder in synchronization with each other.
Advantageous Effect of the Invention
[0007] The present invention can provide an injection apparatus
capable of realizing high injection speed and high injection
pressure by means of a single unit of driving means.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 This drawing shows a circuit diagram of an injection
apparatus of the present invention.
MODE FOR CARRYING OUT THE INVENTION
[0009] An injection apparatus according to an embodiment of the
present invention is described hereinafter.
[0010] A die-casting machine functioning as an injection apparatus
is an apparatus for injecting a metallic material (e.g., aluminum)
as a molten molding material into a cavity that is formed by a
fixed mold and movable mold configuring a mold, and then filling
the cavity with the metallic molding material. The molding material
that is injected into the mold is solidified and then demolded,
resulting in a desired molded article. Referring to FIG. 1, a
die-casting machine 100 includes an injection cylinder 1. The
injection cylinder 1 is a cylinder for injection-driving an
injection plunger to force, into the cavity, the metallic material
that is supplied to an injection sleeve communicated to the cavity.
The injection plunger is connected to a tip end of a piston rod 1Pa
of a piston 1P in the injection cylinder 1. A acceleration cylinder
2 as the first cylinder and a booster cylinder 3 as the second
cylinder, which feed and drain hydraulic oil as an incompressible
fluid (fluid), are connected to the injection cylinder 1 via
piping. A bottom chamber 2B of the acceleration cylinder 2 is
connected to a bottom chamber 1B of the injection cylinder 1.
Furthermore, a bottom chamber 3B of the booster cylinder 3 is
connected to the bottom chamber 1B of the injection cylinder 1 in
parallel with the bottom chamber 2B of the acceleration cylinder 2.
In the present embodiment, the stroke of a piston 2P of the
acceleration cylinder 2 and the stroke of a piston 3P of the
booster cylinder 3 are set at the same length. The diameter D2 of
the acceleration cylinder 2 is set to be greater than the diameter
D3 of the booster cylinder 3. The piston 2P of the acceleration
cylinder 2 is connected to a nut 12 via the rod chamber 2R. The
piston 3P of the booster cylinder 3 is connected to the nut 12 via
the rod chamber 3R. A ball screw 11 is fitted into the nut 12. The
ball screw 11 can freely be rotated by a motor 10. In the present
embodiment, a servomotor is used as the motor 10. The ball screw 11
and the nut 12 configure a ball screw mechanism. The nut 12 is
configured to move in the right-left direction on FIG. 1 as the
ball screw 11 rotates. The piston 2P and the piston 3P can be
freely reciprocated in the acceleration cylinder 2 and the booster
cylinder 3 respectively by the nut 12. In the present embodiment,
the piston 2P and the piston 3P are connected to the nut 12 in such
a manner as to synchronously move by the same moving quantity when
the nut 12 moves. Further, in the present embodiment, the motor 10,
the ball screw 11 and the nut 12 configure a driving means. The
driving means in the present embodiment is a single unit.
[0011] A pilot operated check valve 4 as a directional control
valve is provided on the pipe between the bottom chamber 1B located
at one end of the injection cylinder 1 and the bottom chamber 2B
located at one end of the acceleration cylinder 2. The pilot
operated check valve 4 allows hydraulic oil to flow from the bottom
chamber 2B of the acceleration cylinder 2 toward the bottom chamber
1B of the injection cylinder 1. The pilot operated check valve 4
also cuts off the flow of the hydraulic oil from the bottom chamber
1B to the bottom chamber 2B. Note that a pilot conduit 4P is
connected to the pilot operated check valve 4 in the present
embodiment. The pilot conduit 4P is a conduit for introducing
pressure in the pipe, which connects the rod chamber 1R of the
injection cylinder 1 to a feed/discharge mechanism 20 (to be
described hereinafter), to the pilot operated check valve 4. Thus,
when the pilot pressure is applied from the pilot conduit 4P to the
pilot operated check valve 4, the pilot operated check valve 4 can
be opened to allow the flow of the hydraulic oil from the bottom
chamber 1B to the bottom chamber 2B. A flow rate adjustment circuit
5 as the flow rate adjustment means is provided between the pilot
operated check valve 4 and the bottom chamber 2B of the
acceleration cylinder 2. The flow rate adjustment circuit 5 is
provided with a buffer tank 15, a pilot switching valve 16 and a
check valve 6. The buffer tank 15 temporarily stores enough
hydraulic oil to adjust any excess and deficiency of hydraulic oil
in the acceleration cylinder 2. The check valve 6 is provided on a
pipe that extends from the buffer tank 15 to the pipe between the
pilot operated check valve 4 and the bottom chamber 2B of the
acceleration cylinder 2. The check valve 6 cuts off the flow of
hydraulic oil from the pipe between the pilot operated check valve
4 and the bottom chamber 2B of the acceleration cylinder 2 to the
buffer tank 15. Also, the check valve 6 allows the hydraulic oil to
flow from the buffer tank 15 to the pipe between the pilot operated
check valve 4 and the bottom chamber 2B of the acceleration
cylinder 2. The check valve 6 is a hydraulic oil replenishment
control valve for appropriately supplying the hydraulic oil of the
buffer tank between the pilot operated check valve 4 and the bottom
chamber 2B of the acceleration cylinder 2 when the hydraulic oil
between the pilot operated check valve 4 and the bottom chamber 2B
of the acceleration cylinder 2 becomes insufficient. The pilot
switching valve 16 is provided on a pipe that extends from the pipe
between the pilot operated check valve 4 and the bottom chamber 2B
of the acceleration cylinder 2 to the buffer tank 15. The pilot
switching valve 16 is a valve for switching between a communicated
state and a cut off state of the flow of hydraulic oil from the
pipe between the pilot operated check valve 4 and the bottom
chamber 2B of the acceleration cylinder 2 to the buffer tank 15.
The pilot switching valve 16 is normally biased to its cut off
position by a spring. A pilot conduit 16P is connected to the pilot
switching valve 16. The pilot conduit 16P is a conduit for
introducing, to the pilot switching valve 16, pressure in the pipe
located between the bottom chamber 1B of the injection cylinder 1
and the pilot operated check valve 4 and bottom chamber 3B of the
booster cylinder 3. The pilot switching valve 16 is switched when
the pilot pressure introduced from the pilot conduit 16P becomes
greater than the biasing force of the spring. The pilot switching
valve 16 discharges the hydraulic oil to the buffer tank 15 when
switched to the communicated state. In the present embodiment, the
pilot pressure is set at a value smaller than the maximum pressure
that can be applied by the acceleration cylinder 2 and the booster
cylinder 3.
[0012] The feed/discharge mechanism 20 is connected to the rod
chamber 1R of the injection cylinder 1. The feed/discharge
mechanism 20 is a hydraulic circuit for feeding the hydraulic oil
to the rod chamber 1R and discharging the hydraulic oil from the
rod chamber 1R. The feed/discharge mechanism 20 is configured by an
electromagnetic switching valve 21, a hydraulic pump 22, and a
hydraulic oil tank 25. The electromagnetic switching valve 21
switches the condition of the pipe connecting the rod chamber 1R of
the injection cylinder 1 and the hydraulic oil tank 25 to each
other. The hydraulic pump 22 is provided on the pipe between the
electromagnetic switching valve 21 and the hydraulic oil tank 25.
The hydraulic pump 22 is a pump for supplying the hydraulic oil in
the hydraulic oil tank 25 to the rod chamber 1R of the injection
cylinder 1.
[0013] The actions of the present embodiment are described
next.
[0014] The injection apparatus 100 drives the injection cylinder in
order to inject a molding material by means of the injection
plunger. In so doing, the injection apparatus 100 supplies the
hydraulic oil to the bottom chamber 1B of the injection cylinder 1
in order to expand the bottom chamber 1B by moving the piston 1P of
the injection cylinder 1. The injection apparatus 100 first drives
the motor 10 to rotate the ball screw 11. Consequently, the nut 12
fitted onto the ball screw 11 is moved toward the left side on FIG.
1, more specifically, is moved to approach the acceleration
cylinder 2 and the booster cylinder 3. When the nut 12 is moved,
the pistons 2P and 3P connected to the nut 12 are moved within the
acceleration cylinder 2 and booster cylinder 3, respectively. The
pistons 2P and 3P are driven in synchronization with each other and
moved an equal distance. When the piston 2P is moved in
acceleration cylinder 2, the hydraulic oil in the bottom chamber 2B
of the acceleration cylinder 2 is supplied toward the injection
cylinder 1. The hydraulic oil discharged from the bottom chamber 2B
passes through the pilot operated check valve 4 and flows to the
bottom chamber 1B of the injection cylinder 1. At this moment, the
hydraulic oil discharged from the bottom chamber 2B does not flow
to the flow rate adjustment circuit 5. In the flow rate adjustment
circuit 5, the pilot switching valve 16 is biased to its cut off
position by the spring. In addition, the check valve 6 cuts off the
flow of the hydraulic oil from the bottom chamber 2B to the buffer
tank 15. When the piston 3P is moved in the booster cylinder 3, the
hydraulic oil in the bottom chamber 3B of the booster cylinder 3 is
supplied toward the injection cylinder 1. The hydraulic oil
discharged from the bottom chamber 3B flows to the bottom chamber
1B of the injection cylinder 1 together with the hydraulic oil
discharged from the bottom chamber 2B of the acceleration cylinder
2. Here, the feed/discharge mechanism 20 causes the electromagnetic
switching valve 21 to communicate the rod chamber 1R with the
hydraulic oil tank 25 so that the hydraulic oil in the rod chamber
1R can be discharged to the hydraulic oil tank 25. In the injection
cylinder 1, the hydraulic oil is supplied from both the
acceleration cylinder 2 and the booster cylinder 3 to the bottom
chamber 1B, and the hydraulic oil of the rod chamber 1R is
discharged to the hydraulic oil tank 25, thereby moving the piston
1P at high speed. As a result, the injection plunger is
injection-driven at high speed.
[0015] The cavity becomes filled with the molding material as the
injection of the molding material at high speed is implemented by
the injection cylinder 1 and the injection plunger. Once the cavity
becomes filled with the molding material, resistance against the
direction in which the piston 1P moves occurs in the injection
plunger and the injection cylinder 1. Consequently, the pressure of
the hydraulic oil in the bottom chamber 1B of the injection
cylinder 1 is increased by the hydraulic oil supplied from the
acceleration cylinder 2 and the booster cylinder 3. The injection
apparatus 100 continues to drive the motor 10 to continuously
supply the injection cylinder 1 with the hydraulic oil from the
acceleration cylinder 2 and the booster cylinder 3. The pressure
within the pilot conduit 16P is increased as the pressure within
the bottom chamber 1B is increased. When the pressure within the
pilot conduit 16P exceeds a predetermined value, the pilot
switching valve 16 switches from the cut off position to the
communicating position. Then, the hydraulic oil discharged from the
bottom chamber 2B of the acceleration cylinder 2 is caused to flow
and discharged to the buffer tank 15 via the pilot switching valve
16, because the pressure of the hydraulic oil between the bottom
chamber 1B of the injection cylinder 1 and the pilot operated check
valve 4 becomes higher than the buffer tank 15. On the other hand,
the hydraulic oil supplied from the bottom chamber 3B of the
booster cylinder 3 pressurizes the hydraulic oil within the bottom
chamber 1B of the injection cylinder 1. The molding material within
the cavity therefore continues to be pressurized. Moreover, the
hydraulic oil supplied from the bottom chamber 3B is prevented by
the pilot operated check valve 4 from flowing to the buffer tank
15. In the injection cylinder 1, when the pressure within the
bottom chamber 1B becomes equal to or greater than the pilot
pressure of the pilot switching valve 16, only the hydraulic oil of
the booster cylinder 3 is supplied to the bottom chamber 1B. This
makes the supply of hydraulic oil thereto lower than when the
hydraulic oil is supplied from the acceleration cylinder 2 and the
booster cylinder 3. In the injection cylinder 1, high pressure is
applied to the piston 1P by the hydraulic oil from the booster
cylinder 3. The injection cylinder 1 and injection plunger then
gradually apply pressure into the cavity. Consequently, the
pressure within the cavity is increased. This pressure increasing
step pressurizes and forms the molding material in the cavity.
[0016] The resistance applied from the cavity to the injection
plunger and injection cylinder 1 increases as the injection plunger
and injection cylinder 1 use the hydraulic oil from the booster
cylinder 3 to increase the pressure within the cavity.
Consequently, the resistance is transmitted from the bottom chamber
1B of the injection cylinder 1 to the booster cylinder 3 and acts
as a load resistance onto the motor 10 via the nut 12 and the ball
screw 11. A load torque of the motor 10 is monitored in the
injection apparatus 100. When the load torque of the motor 10
becomes equal to or greater than a predetermined value, it is
determined that the process of filling the cavity with the molding
material is completed. Further, the injection apparatus 100
continues to drive the motor 10 to continuously apply pressure to
the molding material in the cavity with a predetermined torque.
Thereafter, when the molding material becomes solidified, the
injection apparatus 100 stops the motor 10. After the molding
material has solidified, the injection apparatus 100 determines
that the molding process is completed. Further, the injection
apparatus 100 then takes out the molded article. At this moment,
when separating the movable mold from the fixed mold, the injection
apparatus 100 drives the motor 10 to apply a load to a part of the
molded article in order to push the molded article out of the fixed
mold. The molded article is demolded from the fixed mold in this
manner.
[0017] Next, the injection apparatus 100 drives the motor to rotate
reversely. The injection apparatus 100 then retracts the injection
plunger and the injection cylinder 1. As a result of reversely
rotating the motor 10, the piston 2P of the acceleration cylinder 2
and the piston 3P of the booster cylinder 3 are moved in the
opposite direction by the ball screw 11 and the nut 12.
Consequently, in the acceleration cylinder 2, the rod chamber 2R is
reduced in size and the bottom chamber 2B is increased. At the same
time, in the booster cylinder 3, the rod chamber 3R is reduced in
size and the bottom chamber 3B is increased. The injection
apparatus 100 drives the hydraulic pump 22 of the feed/discharge
mechanism 20 to pour hydraulic oil into the rod chamber 1R of the
injection cylinder 1. When the hydraulic oil is supplied to the rod
chamber 1R and the bottom chambers 2B and 3B of the acceleration
cylinder 2 and booster cylinder 3 are increased in size, the
hydraulic oil flows out of the bottom chamber 1B of the injection
cylinder 1. At this moment, the pilot operated check valve 4 is
opened in response to the application of the pilot pressure through
the pilot conduit 4P, allowing the hydraulic oil to flow from the
bottom chamber 1B to the bottom chamber 2B. As a result, the amount
of hydraulic oil in the rod chamber 1R of the injection cylinder is
increased, while the amount of hydraulic oil in the bottom chamber
1B is decreased, thereby moving the piston 1P. Subsequently, the
injection cylinder 1 and the injection plunger are retracted. Once
the injection plunger and the injection cylinder 1 are retracted to
predetermined positions, the hydraulic oil no longer flows out of
the bottom chamber 1B of the injection cylinder 1. At this moment,
the piston 2P of the acceleration cylinder 2 and the piston 3P of
the booster cylinder 3 are not yet returned to predetermined
positions and therefore continue to return to the predetermined
positions. The shortage of hydraulic oil which occurs due to the
size increase of the bottom chambers 2B and 3B is replenished with
the hydraulic oil from the buffer tank 15 via the check valve 6.
Once the piston 2P of the acceleration cylinder 2 and the piston 3P
of the booster cylinder 3 are retracted to the predetermined
positions, one cycle of injection molding is ended.
[0018] The injection apparatus 100 of the present embodiment has
the following effects.
[0019] (1) In the injection apparatus 100 of the present
embodiment, the acceleration cylinder 2 and the booster cylinder 3
are disposed in parallel with each other with respect to the
injection cylinder 1. The acceleration cylinder 2 and the booster
cylinder 3 are driven synchronously by the motor 10, the ball screw
11 and the nut 12. Thus, the driving means comprising the single
motor 10, ball screw 11 and nut 12 can realize high injection speed
and injection pressure.
[0020] (2) The driving means of the injection apparatus 100 is a
single structure comprising the motor 10, the ball screw 11 and the
nut 12. Compared to a construction in which the acceleration
cylinder 2 and the booster cylinder 3 are driven by a plurality of
driving means, the construction of the present embodiment can
reduce the number of parts and the cost of the injection apparatus
100. In addition, since only the single-structured driving means
need be provided in the injection apparatus 100, reduction in the
space for and the size of the injection apparatus 100 can be
accomplished.
[0021] (3) The injection apparatus 100 is provided with the flow
rate adjustment circuit 5. The flow of the hydraulic oil in the
acceleration cylinder 2 can be easily switched by the flow rate
adjustment circuit 5.
[0022] (4) The flow rate adjustment circuit 5 comprises the buffer
tank 15, the check valve 6 and the pilot switching valve 16. The
pilot switching valve 16 can be freely switched by means of the
pilot pressure. Therefore, it is not necessary to provide the flow
rate adjustment circuit 5 with new driving means, providing a
simple structure of the flow rate adjustment circuit 5.
[0023] (5) The diameter D2 of the acceleration cylinder 2 is set to
be greater than the diameter D3 of the booster cylinder 3.
Therefore, when driving the injection cylinder 1, high-speed drive
of the injection cylinder 1 can be accomplished by supplying a
larger amount of hydraulic oil by using the piston 2P of the
acceleration cylinder 2 with the larger diameter D2. In addition,
the diameter D3 of the booster cylinder 3 for applying a necessary
pressure to the injection cylinder 1 by means of the booster
cylinder 3 can be set without consideration of the diameter D2 of
the acceleration cylinder 2.
[0024] The present invention is not limited to the foregoing
embodiment. Modifications of the present invention are described
hereinbelow. [0025] The acceleration cylinder 2 and the booster
cylinder 3 according to the embodiment employ different diameters
and the same manner stroke but are not limited to such
construction. The size of each cylinder can be changed as
appropriate. For instance, the diameter D2 of the acceleration
cylinder 2 and the diameter D3 of the booster cylinder 3 may be
equal to each other. The diameter D2 may be smaller than the
diameter D3. It is preferred that the diameters of the pistons 2P
and 3P be set appropriately in accordance with the diameter D1 of
the piston 1P of the injection cylinder 1. [0026] The flow rate
adjustment circuit 5 is not limited to the construction described
in the embodiment. For example, an electromagnetic switching valve
may be used in place of the pilot switching valve 16. Further, the
above construction may have a construction where the position of
the injection cylinder 1 is detected with a limit switch or the
like and the switching valve is switched at a predetermined
position of the injection cylinder 1. Furthermore, the above
construction may have a construction where an encoder or the like
is provided in the motor 10 and the switching valve is switched
based on the driving amount of the motor 10 or the like. Also, a
switching valve may be used in place of the check valve 6. Further,
a hydraulic pump, etc., may be provided to adjust the flow rate of
the hydraulic oil. [0027] The driving means according to the
embodiment is not limited to the structure of a ball screw. The
construction of the driving means may be changed as appropriate as
long as it can synchronously drive the piston 2P of the
acceleration cylinder 2 and the piston 3P of the booster cylinder 3
by means of the motor 10. [0028] The rod chamber 1R of the
injection cylinder 1, the rod chamber 2R of the acceleration
cylinder 2 and the rod chamber 3R of the booster cylinder 3 may be
configured so that hydraulic oil is fed into and discharged from
their interiors.
EXPLANATION OF REFERENCE NUMERALS
[0029] 1 Injection cylinder, 1B Bottom chamber, 1P Piston, 1Pa
Piston rod, 1R Rod chamber, 2 Acceleration cylinder, 2B Bottom
chamber, 2P Piston, 2R Rod chamber, 3 Booster cylinder, 3B Bottom
chamber, 3P Piston, 3R Rod chamber, 4 Pilot operated check valve,
4P Pilot conduit, 5 Flow rate adjustment circuit, 6 Check valve, 10
Motor, 11 Ball screw, 12 Nut, 15 Buffer tank, 16 Pilot switching
valve, 16P Pilot conduit, 100 Die-casting machine (injection
apparatus).
* * * * *