JPH11268092A - Injection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection apparatus employing a fluid pressure drive system reducing the size and capacity of the motor and ball screw of a drive system. SOLUTION: In an injection apparatus wherein a resin material is melted to be weighed while an injection plunger screw is retracted and the injection plunger or screw is advanced to eject the molten resin, an injection fluid pressure cylinder 40 is connected to the injection plunger or screw 10 and a first fluid pressure control cylinder having a first plunger 47 driven by an electromotor is connected to the advance cylinder chamber 43 of the injection fluid pressure cylinder 40 and a second fluid pressure controlling cylinder 46 having a second plunger 52 is connected to the retraction cylinder chamber 44 of the injection fluid pressure cylinder 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection device for an injection molding machine, and more particularly to an injection device with improved fluid pressure drive control of an injection cylinder for performing an injection operation.

[0002]

2. Description of the Related Art Conventionally, as an injection device used for an injection molding machine, there is an electric injection device in addition to a hydraulic injection device. In this electric injection device, the rotational motion of the electric motor is converted into the linear motion of a screw or an injection plunger by a transmission mechanism such as a ball screw.

[0003] In this type of electric injection device, a screw or an injection plunger is driven directly by the output of the electric motor.
By controlling the speed and torque of the electric motor, it is possible to control the injection speed, the firing power, and the like. Therefore, in order to respond to various patterns of changes in the injection speed and the firing power, the motor needs to have as large a capacity as possible, and accordingly, a ball screw having a large capacity is used.

FIG. 5 shows an example of a conventional electric injection device. This motor-driven injection device is a screw-in-line type injection device, and reference numeral 10 denotes a screw. This screw 10
Is a screw that plasticizes and measures resin and also works as an injection plunger. The screw 10 is inserted into the barrel 11 so as to be rotatable and move forward and backward in the axial direction. A heater 12 for heating is provided on an outer peripheral portion of the barrel 11. The molding material resin is
It is put into the barrel 11 from a hopper 13 attached to one end of the barrel 11, and is plasticized by the rotation of the screw 10. Reference numeral 14 denotes a rotation drive unit of the screw 10. The screw 10 is connected to a drive shaft 16 via a joint 15. A drive shaft 16 is provided inside the housing 17.
, And a thrust bearing 19 for receiving a thrust load of a reaction force of the radiating power.

[0005] Reference numeral 20 denotes an electric motor for driving the drive shaft 16. A gear 21 is attached to the output shaft of the electric motor, and the gear 21 and a gear 2 attached to the drive shaft are attached.
2 are engaged. Therefore, the rotational power of the electric motor is transmitted to the drive shaft 16 via the gears 21 and 22 to rotate the screw 10.

On the other hand, as an electric drive mechanism for moving the screw 10 forward in the injection step and retracting the screw 10 in the metering step, a ball screw 24 connected to the rotary drive unit 14 is screwed to this. A nut 25 and an electric motor 26 are provided. The output shaft of the motor 26 has a gear 2
The gear 27 meshes with a gear 28 attached to the ball nut 25 side, and transmits the rotational motion of the electric motor 26 to the ball nut 25.

[0007] Such an electric injection device is of the electric linear motion type, and the ball screw 24 and the ball nut 25 are loaded with the firing power itself. For this reason, the electric motor 26
A driving torque determined by the reduction ratio of the gears 27 and 28 is applied, and the ball screw 24 and the electric motor 26 need to have a large capacity.

FIG. 6 shows a motor 30, a transmission mechanism including gears 31 and 32, a ball nut 33, and a motor 30 in order to reduce the size and capacity of each element of an electric drive mechanism for moving the screw 10 forward and backward. This is an injection device in which two sets of ball screws 34 are arranged in parallel.

[0009]

In the case of two sets of electric drive mechanisms in parallel, as in the injection apparatus shown in FIG. 6, the mechanical parallelism of each set is accurately maintained, and the drive control is completely synchronized. There is a need. However, as a practical matter, perfect synchronous operation of the two electric motors 30, 30 is difficult. For this reason, strictly unbalanced thrust is applied to the ball screws 34, 34, and the ball screws 34 are exposed to an eccentric load. Then, the amount of unbalance is gradually increased, and an excessive load is applied to one of the ball screws 34, resulting in a problem that wear is accelerated.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, in which the forward or backward movement of a screw or an injection plunger is performed by an injection hydraulic cylinder and the direction of the working fluid sent to the injection hydraulic cylinder. The present invention provides an injection device employing a new fluid pressure drive system that achieves downsizing and downsizing of a motor of a drive mechanism and a ball screw by using a servomotor to drive a plunger of a control cylinder for controlling pressure and flow rate. It is in.

[0011]

In order to achieve the above object, the present invention provides a method of melting a resin material and measuring a molten resin while retreating an injection plunger or a screw.
In an injection apparatus for injecting molten resin by advancing the injection plunger or screw, an injection fluid pressure cylinder is connected to the injection plunger or screw, and a first motor driven plunger is connected to a forward cylinder chamber of the injection fluid pressure cylinder. And a second fluid pressure control cylinder having a motor driven second plunger is connected to the retraction cylinder chamber of the injection fluid pressure cylinder. It is assumed that.

According to the present invention, in the present invention, the first fluid pressure control cylinder includes a first ball screw connected to the first plunger, and a first servomotor for driving the first ball screw to rotate. A second ball screw connected to a second plunger, the second fluid pressure control cylinder;
A second servomotor that rotationally drives the second hole screw, so that when one of the plungers is in the most advanced position, the other is in the most retracted position.

Further, according to the present invention, the first servomotor and the second servomotor are operated independently or both simultaneously, and the first plunger and the second plunger are advanced and retracted in opposite directions to each other. The pressure cylinder is provided with fluid pressure control means for controlling the flow rate and pressure of the working fluid and for supplying and discharging the working fluid.

The fluid pressure control means includes a first pressure detecting means for detecting a pressure of a working fluid in a forward cylinder chamber of the injection fluid pressure cylinder, and an operation of a retreating cylinder chamber of the ejection fluid pressure cylinder. A second pressure detecting means for detecting a pressure of the fluid, a means for setting a target value of a pressure in a forward cylinder chamber or a retreating cylinder chamber of the injection hydraulic cylinder, respectively, the first pressure detecting means or the first pressure detecting means. (2) The detected pressure fed back from the pressure detecting means is compared with a target value, and the first servo motor and the second servo motor are adjusted so that the pressure of the working fluid in the forward cylinder chamber or the backward cylinder chamber of the injection fluid pressure cylinder becomes the target value. 2 Simultaneously control the speed of the servomotor or feed back the pressure of the working fluid in the cylinder chamber in which the target value is set from the pressure detecting means, and check the pressure. As a value consists of a servo control means for controlling the speed of the first or second servo motor,
The pressure and flow rate of the working fluid supplied to and discharged from the injection fluid pressure cylinder are accurately feedback controlled through the operation of the servomotor.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the injection device according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing the configuration of the injection device according to the present embodiment. In this injection device, the same components as those of the conventional injection device shown in FIGS. 5 and 6 are denoted by the same reference numerals.

The screw 10 is a screw that plasticizes and measures the resin and also functions as an injection plunger. The screw 10 is inserted into the barrel 11 so as to be rotatable and move forward and backward in the axial direction. A heater 12 for heating is provided on an outer peripheral portion of the barrel 11. The resin of the molding material is put into the barrel 11 from a hopper 13 attached to one end of the barrel 11, and is plasticized by the rotation of the screw 10.

Reference numeral 14 denotes a rotation drive unit of the screw 10.
The screw 10 is connected to a drive shaft 16 via a joint 15. Inside the housing 17, a radial bearing 18 that rotatably supports the drive shaft 16 and a thrust bearing 19 that receives a thrust load of a reaction force of the radiation output are built in.

Reference numeral 20 denotes an electric motor for driving the drive shaft 16. A gear 21 is attached to the output shaft of the electric motor, and the gear 21 and a gear 2 attached to the drive shaft are attached.
2 are engaged. Therefore, the rotational power of the electric motor is transmitted to the drive shaft 16 via the gears 21 and 22 to rotate the screw 10.

Reference numeral 40 denotes a hydraulic cylinder for injection, and in this embodiment, a hydraulic cylinder using hydraulic oil as a working fluid. A piston 41 is slidably fitted to the injection hydraulic cylinder 40, and the piston rod 42 is
Is connected to the rotation drive unit 14. The cylinder chamber of the injection hydraulic cylinder 40 is divided by a piston 41 into a cylinder chamber 43 on the head side and a cylinder chamber 44 on the rod side. In the present embodiment, the cylinder chamber 4 on the head side
Reference numeral 3 denotes a cylinder chamber for moving the screw 10 forward (forward side), and the cylinder chamber 44 on the rod side
Is the cylinder chamber for retracting (retracting side).

The hydraulic cylinder 40 for injection may be assembled in such a manner that the head side of the cylinder body is connected to the rotary drive unit 14. In this case, the rod-side cylinder chamber 44 becomes the forward cylinder chamber, and the head-side cylinder chamber 43 becomes the backward cylinder chamber.

Reference numeral 45 denotes a first hydraulic control cylinder connected to a port of the head side cylinder chamber 43 of the injection hydraulic cylinder 40. 46 is an injection hydraulic cylinder 4
This is a second hydraulic control cylinder connected to the port of the No. 0 rod side cylinder chamber 44.

A first plunger 47 is slidably fitted to a first hydraulic control cylinder 45 for supplying and discharging hydraulic oil to and from the cylinder chamber 43 on the head side of the injection hydraulic cylinder 40. The first plunger 47 has a shaft hole in which a female screw is formed, and a first ball screw 48 is screwed into the shaft hole. The first ball screw 48 is driven to rotate by a first servomotor 50, and is connected to a drive shaft of the first servomotor 50 via a coupling 51.

On the other hand, the second hydraulic control cylinder 46 for supplying and discharging hydraulic oil to and from the cylinder chamber 44 on the rod side of the injection hydraulic cylinder 40 has the same cylinder diameter as the first hydraulic control cylinder 45 in this embodiment. And a cylinder having a cylinder stroke, but may be cylinders of different sizes. A second ball screw 53 is screwed into a shaft hole of the second plunger 52. The second ball screw 53 is connected to a drive shaft of a second servomotor 54 via a coupling 55.

In this embodiment, the rotary motion transmitted from the first servomotor 50 and the second servomotor 54 is directly converted into linear motion by the first ball screw 48 and the second ball screw 53, respectively, and the first plunger 47 is rotated. , The second plunger 52, but a linear motion may be transmitted between the ball screws 48, 53 and the plungers 47, 52 via another transmission element.

As described above, the injection hydraulic cylinder 40 includes:
The first hydraulic control cylinder 45 or the second hydraulic control cylinder 46 is directly used without using a hydraulic circuit including a hydraulic pump, a directional control valve, a pressure control valve, a flow control valve, and the like as in a conventional hydraulic unit. The pressurized oil pressurized by is supplied. When the screw 10 is advanced, the first servomotor 50 advances the first plunger 47 and sends the pressure oil to the head side cylinder chamber 43, and the second servomotor 54 retreats the second plunger 52, and the rod The pressure oil in the side cylinder chamber 44 is discharged. The screw 10 can also be moved forward by operating the first servomotor 50 alone without operating the second servomotor 54. In this case, since the second servomotor 54 is in a free state in which no torque is generated, the second plunger 52 is pushed backward by the hydraulic oil returned from the rod-side cylinder chamber 44 to the second hydraulic control cylinder 46 and retreats. It is supposed to. When the screw 10 is moved backward, an operation opposite to that of the forward movement is performed.

The firing force depends on the capacity of the injection hydraulic cylinder 40. However, since the pressurized oil is directly pressurized by the first plunger 47 and the second plunger 52, a force is applied to the ratio between the pressure receiving area of the piston 41 and the pressure receiving area of the plunger. Is enlarged, so that the first plunger 47 and the second plunger 52 having a smaller diameter than the piston diameter of the injection hydraulic cylinder 40 can be used. In that case, an appropriate diameter may be selected with respect to the piston diameter of the injection hydraulic cylinder 40 in relation to the required firing power.

In FIG. 1, there are a first plunger 47 and a second plunger 52 at positions where the injection operation is started.
That is, when the first plunger 47 is at the rearmost position, the second plunger 52 is at the most advanced position. Also,
Conversely, in the weighing step, the first plunger 47 is at the most advanced position, and the second plunger 52 is at the most retracted position. The first plunger 47 and the second plunger 52 are configured to move in opposite directions through each process, such that if one advances, the other retreats.

The first servomotor 50 and the second servomotor 54 for driving the first plunger 47 and the second plunger 52 are controlled at the same time or one of them, and the pressure of the pressure oil supplied to the injection hydraulic cylinder 40 is controlled. FIG. 2 shows a block diagram of hydraulic control for controlling the flow rate and the direction.

In FIG. 2, reference numeral 60 denotes an arithmetic unit of the numerical controller. The arithmetic unit 60 calculates a speed command from a speed program P predetermined for a pattern of a change in the injection speed. In this case, the injection speed, that is, the forward speed of the screw 10 is the same as the moving speed of the piston 41 of the hydraulic cylinder 40 for injection. Injection speed and first moving forward
The moving speed of the plunger 47 is in a relationship inversely proportional to the ratio of the pressure receiving area of the piston 41 in the head-side cylinder chamber 43 to the pressure receiving area of the first plunger 47. Further, the injection speed and the moving speed of the retreating second plunger 52 are in inverse proportion to the ratio of the pressure receiving area of the piston 41 in the rod side cylinder chamber 44 to the pressure receiving area of the second plunger 52. The injection speed is controlled by the injection hydraulic cylinder 40.
When the injection speed is determined, the forward speed of the first plunger 47 and the retreat speed of the second plunger 52 are also determined.
0, the speed command to be given to the second servomotor 54 is also uniquely determined. The speed program P is set in advance in accordance with such a relationship and the injection conditions for each product, and is input to the numerical controller.

The speed command calculated by the arithmetic unit 60 is distributed and input to servo controllers 61 and 62 for controlling the first servomotor 50 and the second servomotor 54, respectively. The servo controllers 61 and 62 give torque commands so that the speeds fed back from the first servomotor 50 and the second servomotor 54 match the speed commands, respectively.

When the second servomotor 54 is not operated and no torque is applied, the speed program P gives only the first servomotor 50 a speed command corresponding to the injection speed.

On the other hand, the injection hydraulic cylinder 40 has a pressure detector 64 for detecting the pressure of the pressure oil in the cylinder chamber 43 on the head side and a pressure detector for detecting the pressure of the pressure oil in the cylinder chamber 44 on the rod side. A pressure control loop is provided in which outputs are fed back and compared with target pressure values set by the pressure setting devices 66 and 67, respectively. The deviation between the detected value of the pressure and the target value is added to the speed command to correct the speed command.

Hereinafter, while relating to the operation of the injection device,
The details of the hydraulic control will be described. FIG. 3 is a diagram showing the relationship between the position of the screw 10 and the pressure of the injection cylinder 40. In FIG. 3, Pa indicates the pressure of the pressure oil in the head side cylinder chamber 43 of the injection cylinder 40.
b indicates the pressure of the pressure oil in the rod-side cylinder 44. FIG.
As shown in (a), in the injection step, when only the first hydraulic control cylinder 45 is driven by the first servomotor 50 to advance the screw 10, the pressure Pa of the head-side cylinder chamber 43 becomes equal to the injection pressure. , And the pressure in the rod-side cylinder chamber 44 is not controlled, so the target value is not set.

Based on the speed program P, the arithmetic unit 6
0 is the servo controller 61 of the first servomotor 50
Is given a predetermined speed command.
Is not given a speed command so as to rotate in a torque-free state.

When the first plunger 47 is driven forward by the first servomotor 50, the hydraulic oil in the first hydraulic control cylinder 45 is pressurized, and this hydraulic oil is released from the head side cylinder of the injection cylinder 40. The screw 10 is supplied to the chamber 43 and moves forward. On the other hand, the hydraulic oil in the rod-side cylinder chamber 44 is discharged to the second hydraulic control cylinder 46,
Along with this, the second plunger 52 reversely rotates the second servomotor 54, which is freely rotatable with zero torque. Thus, the screw 10 injects the resin into the mold using the force of the pressure Pa of the head-side cylinder chamber 43 acting on the pressure-receiving area of the piston 41 on the head side as a radiation output.

In the mold, there is resistance to resin flow,
The load on the screw 10 varies. This change in load also causes a change in the pressure of the pressure oil in the head side cylinder chamber 43 of the injection hydraulic cylinder 40. The pressure of the pressure oil in the head-side cylinder chamber 43 is detected by a pressure detector 64. Then, the detected pressure is fed back, and the detected pressure is compared with a set value Pa set by the pressure setter 66. The deviation is added to the speed command,
When the detected pressure is higher than the set value, the servo controller 61 reduces the magnitude of the torque command input given to the first servomotor 50. As a result, the torque is reduced, and the pressure of the pressure oil in the head-side cylinder chamber 43 is controlled to decrease to the target value Pa. On the other hand, when the detected pressure is lower than the target value Pa, the speed control of the first servomotor 50 is continued without changing the speed command.

Next, in the injection step, when the first servomotor 50 and the second servomotor 54 are driven together to advance the screw 10, as shown in FIG.
The pressure of the pressure oil in the head side cylinder chamber 43 of the injection hydraulic cylinder 40 is set to Pa, and the pressure of the pressure oil in the rod side cylinder chamber 44 is set to Pb.

In the same manner as described above, the first servomotor 50 advances the first plunger 47, and the second servomotor 54 retracts the second plunger 52. Then, the pressure in the cylinder chamber 43 on the head side to which the pressure oil is supplied from the first hydraulic control cylinder 45 is controlled so as not to exceed the pressure target value Pa in the same manner as described above. The pressure in the rod-side cylinder chamber 44 from which the pressure oil is discharged to the second hydraulic control cylinder 46 is feedback-controlled so as to match the negative target pressure Pb.

As described above, the second plunger 52 is retracted by the second servomotor 54 to move the rod-side cylinder chamber 4
By keeping the pressure at 4 negative, the first servo motor 5
In addition to 0, the second servomotor 54 can also bear the load of the radiation output.

The load sharing ratio is determined by the target pressure Pa and P
Since the ratio is b, the load can be equally divided by setting the absolute value to one-to-one. Further, as described above, the pressure in the rod-side cylinder chamber 44 is set to the negative pressure, and the load can be shared by the first servomotor 50 and the second servomotor 54 according to the magnitude of the set value of the target pressure. Means that the servomotors 50 and 54 can be reduced in capacity. Further, it is not necessary to synchronize the operations of the two servomotors strictly, and it is only necessary to operate the two servomotors so as to coincide with the respective target pressures. Can be eliminated.

As described above, the servo motor 5 in the injection process
Although the pressure control of the injection hydraulic cylinder 40 by 0 and 54 has been simplified, the relationship with the injection speed will now be described with reference to FIG.

FIG. 4 is a diagram showing a change in the injection pressure P when the screw 10 is advanced while performing injection while controlling the injection speed to change stepwise as indicated by Vp. In the actual injection process, an injection operation is required so that the injection speed changes as indicated by Vp. A speed program P is created in accordance with such an injection speed pattern and input to the arithmetic unit 60. The arithmetic unit 60 gives speed commands for realizing the change of the injection speed as shown by the curve Vp to both the first servomotor 50 and the second servomotor 54 from this speed program, and the first plunger 47 and The moving speed of the second plunger 52, that is, the first
The flow rate of the hydraulic oil sent from the hydraulic control cylinder 45 to the injection hydraulic cylinder 40 and the flow rate of the hydraulic oil returned to the second hydraulic control cylinder 46 are controlled (when operating only the first servomotor, the first hydraulic pressure is used). The flow rate of the pressure oil sent from the control cylinder 45 to the head side cylinder chamber 43 of the injection hydraulic cylinder 40 is controlled.).

The change in the flow resistance of the resin accompanying the change in the injection speed causes a pressure loss or the like, and the injection pressure actually applied to the resin by the screw 10 changes as indicated by P. During this time, in order for the first servo motor 50 and the second servo motor 54 to equally share the load of the radiation output, the first servo motor 50 and the second servo motor 54 commanded by the speed command Vp must What is necessary is just to control so that an absolute value may become equal.

When the resin is injected by changing the injection speed in accordance with the quality requirements of the molded article, the control of the pressure cannot be followed due to a sudden increase in the flow resistance and other loads. The injection pressure may suddenly increase at x1. If this situation is left unchecked, the servo motor 50,
Since an abnormal load is applied to the pressure 54, the pressure in the head-side cylinder chamber 43, whose pressure increases due to a sudden increase in the load, does not exceed the maximum pressure so that the pressure does not exceed the maximum pressure as follows. Load can be prevented.

In this case, the output of the pressure detector 64 for detecting the pressure of the head-side cylinder chamber 43 is fed back to the arithmetic unit 60 via the comparison unit 70. This comparison unit 7
At 0, the set value Ps set by the maximum pressure setting device 71 for setting the maximum pressure is compared with the detected pressure Pa, and the pressure rise is monitored. If the detected pressure Pa suddenly increases and reaches the set value Ps, the arithmetic unit 60 outputs a speed command to decrease the speed to the servo controller 61 of the first servomotor 50 based on the comparison result. As a result, the forward speed of the first plunger 48 decreases, and the injection speed decreases, for example, as indicated by Vp1 in FIG. 4, so that an increase in pressure can be prevented.

Another method may be as follows.
That is, when the detected pressure Pa sharply increases and reaches the set value Ps, the arithmetic unit 60 determines, based on the comparison result, the reverse speed commanded by the speed program P to the servo controller 62 of the second servomotor 54. Regardless, the speed command for forcibly retracting the second plunger 52 at a high speed may be given. Further, the above-described control of the speed command may be performed simultaneously for both the first servomotor 50 and the second servomotor 54.

Next, the operation in the measuring step will be described. When the injection step is completed, the process proceeds to the step of plasticizing and measuring the resin material to be injected in the next molding cycle. In this measuring step, the screw 10 is rotated by the electric motor 20, and the resin material transferred through the spiral groove of the screw 10 is melted by the heating of the heater 12 and the shear energy received from the rotating screw 10. Screw 10
Receiving the pressure of the molten resin sent to the tip of
0 retreats.

While the screw 10 is retracted, the pressure of the pressure oil in the head side cylinder chamber 43 of the hydraulic cylinder 40 for injection is set to Pa, as shown in FIG. Then, this is applied to the screw 10 as back pressure.

In this measuring step, the second servomotor 54
Make sure to rotate without torque without driving,
A first speed command is given to the first servomotor 50 to rotate it. While the screw 10 is retracted, the detected pressure of the head side cylinder chamber 43 is fed back, and a speed command is given to the servo controller 61 so that the detected pressure matches the target pressure Pa.
Outputs a torque command to the first servomotor 50 so as to match the target pressure. Thus, the first plunger 4
7, the pressure oil is discharged to the first hydraulic control cylinder 45, but the pressure is maintained at the set value Pa in the head side cylinder chamber 43, and this pressure acts on the screw 10 as a back pressure.

On the other hand, in the rod side cylinder chamber 44, the pressure is reduced by the retreat of the piston 41, so that the hydraulic oil in the second hydraulic control cylinder 46 is sucked into the rod side cylinder chamber 44, whereby the second plunger 52 Moves forward.

Although the present invention has been described above with reference to the embodiment in which the present invention is applied to a screw-in-line type injection device, it is connected to an injection fluid pressure cylinder like a screw prepura type or a plunger type injection device. The present invention can be similarly applied to an injection device of a type in which a molten resin is injected by moving the injection plunger forward.

[0052]

As is apparent from the above description, according to the present invention, the following effects can be obtained. The working fluid of the injection fluid pressure cylinder is supplied by a fluid pressure control cylinder that directly pressurizes with an electrically driven plunger, so by selecting an appropriate small plunger diameter, the driving mechanism of the plunger can be reduced in size. It can be made compact by using an existing hydraulic injection device.

Further, servo motors are used as the motors for driving the plungers, and the flow rates and pressures of the working fluid supplied to the injection fluid pressure cylinder can be easily and accurately controlled by interlocking the servo motors. Further, since the load of the ejection force applied to the screw or the injection plunger can be shared by the servo motor, a large-capacity servo motor is not required together with the selection of the plunger diameter.

In addition, the load share ratio can be changed in accordance with the magnitude of the negative pressure in the cylinder chamber on the retreating side, and the pressure of the working fluid supplied and discharged by the control object to and from the injection fluid pressure cylinder can be controlled.
Because the flow rate is used, strictly synchronous operation of the two servomotors is not required compared to a mechanism that uses mechanical drive transmission in parallel, and errors are absorbed in the pressure feedback control loop, causing abnormalities in the ball screw. It is possible to avoid accelerated wear due to excessive overload. In addition, it is easy to control the pressure so as not to exceed the maximum pressure in order to prevent a sudden increase in pressure due to a change in load.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an injection device according to the present invention.

FIG. 2 is a block diagram of control for controlling a pressure, a flow rate, and the like of a working fluid supplied to an injection fluid pressure cylinder of the injection device according to the present invention.

FIG. 3 is a diagram showing a relationship between a screw position and a set pressure of an injection fluid pressure cylinder.

FIG. 4 is a diagram showing a change in screw position and speed and a change in injection pressure in an injection step.

FIG. 5 is a sectional view showing a configuration of a conventional electric injection device.

FIG. 6 is a sectional view showing the configuration of another example of a conventional electric injection device.

[Explanation of symbols]

 Reference Signs List 10 screw 11 barrel 12 heater 13 hopper 14 rotation drive unit 16 drive shaft 20 motor 40 injection hydraulic (fluid pressure) cylinder 41 piston 43 forward cylinder chamber 44 retreat cylinder chamber 45 first hydraulic (fluid pressure) control cylinder 46 Second hydraulic (fluid pressure) control cylinder 47 First plunger 48 First ball screw 50 First servo motor 52 Second plunger 53 Second ball screw 54 Second servo motor

Claims (7)

[Claims] 1. An injection device for melting a resin material, measuring the molten resin while retreating an injection plunger or a screw, and advancing the injection plunger or the screw to inject the molten resin. A fluid pressure cylinder is connected, a first fluid pressure control cylinder having a first plunger driven by an electric motor is connected to a forward cylinder chamber of the ejection fluid pressure cylinder, and a retreat side of the ejection fluid pressure cylinder is connected to the fluid pressure cylinder. An injection device, wherein a second fluid pressure control cylinder having a second plunger driven by an electric motor is connected to the cylinder chamber. 2. The first hydraulic pressure control cylinder includes a first ball screw connected to the first plunger, and a first servomotor that drives the first ball screw to rotate. The control cylinder includes a second ball screw connected to the second plunger, and a second servomotor that rotationally drives the second hole screw. When one of the plungers is at the most advanced position, the other of the other cylinder is connected to the second cylinder screw. 2. The injection device according to claim 1, wherein the plunger is at a rearmost position. 3. The first servomotor and the second servomotor are operated independently, or both are operated simultaneously.
3. The injection according to claim 2, wherein the plunger and the second plunger advance and retreat in directions opposite to each other, and the injection fluid pressure cylinder includes a fluid pressure control unit that controls a flow rate and a pressure of the working fluid to supply and discharge the fluid. apparatus. 4. The fluid pressure control means includes: first pressure detection means for detecting a pressure of working fluid in a forward cylinder chamber of the injection fluid pressure cylinder; and a retraction cylinder chamber of the ejection fluid pressure cylinder. Second pressure detecting means for detecting the pressure of the working fluid, and means for setting target values of the pressures of the forward cylinder chamber and the retreat cylinder chamber of the injection fluid pressure cylinder, respectively, and the first pressure detecting means. Alternatively, the detected pressure fed back from the second pressure detecting means is compared with a target value, and the first servo motor is driven so that the pressure of the working fluid in the forward cylinder chamber or the backward cylinder chamber of the injection fluid pressure cylinder becomes the target value. And the speed of the second servomotor are controlled at the same time, or the pressure of the working fluid in the cylinder chamber in which the target value is set is fed back from the pressure detecting means so that the pressure becomes the target value. The injection apparatus according to claim 3, further comprising: servo control means for controlling a speed of the first or second servo motor so as to obtain a value. 5. In the injection step, the servo control means operates only the first servo motor to control the pressure of the forward cylinder chamber of the injection fluid pressure cylinder to a target value. The injection device according to claim 4, wherein 6. In the injection step, the pressure in the retraction cylinder chamber of the injection fluid pressure cylinder is set to a negative pressure, and the servo control means performs injection in accordance with the magnitude of the negative pressure in the retraction cylinder chamber. 5. The injection device according to claim 4, wherein the pressures in both cylinder chambers are simultaneously controlled so that the output load is shared by the first servomotor and the second servomotor. 7. A first servomotor or a second servomotor, respectively, so that the pressure of the working fluid in the forward cylinder chamber of the injection fluid pressure cylinder does not exceed a preset maximum pressure. 5. The injection device according to claim 4, further comprising an overload prevention unit that simultaneously controls the operation of the injection device.