JP2761442B2 - Injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine, and more particularly to an injection molding machine having a screw driving device capable of controlling the back pressure of an injection screw with high accuracy and stability.

[0002]

BACKGROUND ART Conventionally, in molding resin products, etc.,
A screw is provided inside the heating cylinder, and based on the rotation of the screw around the axis and the movement in the axial direction, the injection material introduced into the heating cylinder is fluidized, measured, and further measured. 2. Description of the Related Art Inline screw-type injection molding machines for injection-filling a predetermined mold through a tip nozzle of a heating cylinder are widely used.

[0003] Conventionally, as a screw driving device in such an injection molding machine, a driving device for rotating the screw around the axis and a driving device for moving the screw in the axial direction are separately provided. However, in recent years, Japanese Patent Application Laid-Open No. 59-2827 discloses a first power transmission system in which the rotational driving force of a single rotational driving means is applied as a rotational force around the axis of a screw. A mechanism and a second power transmission mechanism that acts as a moving force in the axial direction of the screw with a feed screw action, and transmits a driving force on a power transmission path in the first and second power transmission mechanisms. There has been proposed a screw drive device having a structure in which first and second clutch means for intermittent connection are provided, respectively.

According to the screw driving device having such a structure,
By selectively operating the first and second clutch means, it is possible to selectively perform rotation driving around the axis of the screw and movement driving in the axial direction with one rotation driving means. There is, therefore, a single screw operation control system, which makes it possible to reduce the size and cost of the control device, and in turn, the screw drive device.

[0005] In such a screw drive device, the screw is rotated around the axis to guide the injection material supplied into the heating cylinder while plasticizing the injection material, and to store the injection material. In the so-called plasticizing / metering process, in which the injection material is metered based on the retreat amount of the injection screw retracted by the pressure of the injection material stored in the screw, the driving force of the rotary drive means is moved in the axial direction of the screw with a feed screw action. A mechanical braking means capable of exerting an appropriate braking force is provided on a power transmission path of the second power transmission mechanism exerting as a moving force of the screw to provide a resistance to the axial movement of the screw. I was getting back pressure.

However, since such mechanical braking means obtains a braking force by dynamic frictional force due to sliding or the like, it is difficult to control and stabilize the back pressure in the screw with high accuracy. there were. Therefore, as described above, in the conventional screw driving device, the back pressure of the screw at the time of injection molding tends to be unstable, so that the injection amount becomes unstable or bubbles are mixed in the injection material. As a result, defective products such as burns and chips are easily generated in the molded products, and a stable molding operation cannot be expected.

[0007]

Here, the present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to solve the problem by using a single rotary drive means to rotate a screw around its axis. It is an object of the present invention to improve the control accuracy of the screw back pressure in an injection molding machine provided with a screw drive device that selectively performs the movement drive in the axial direction.

[0008]

According to the present invention, there is provided a drive unit having an output shaft that can be rotated around one axis, and (b) a rotation drive force of the drive unit. A first power transmission mechanism for transmitting to a screw inserted and arranged in the heating cylinder to rotate the screw about an axis; and (c) provided on a power transmission path of the first power transmission mechanism. And (d) supporting the rotational driving force of the driving means such that the screw is rotatable around the axis and relatively immovable in the axial direction. A second power transmission mechanism that transmits the screw to the support member by a feed screw action and moves the screw in the axial direction via the support member; and (e) power in the second power transmission mechanism. Transmission A heating cylinder into which the screw is inserted and the screw, wherein the screw is inserted into the injection molding machine including a second clutch means provided on a road for interrupting transmission of rotational driving force. A hydraulic cylinder is provided on one side of the supporting member for supporting the hydraulic cylinder, and a piston rod of a piston which is slid in the hydraulic cylinder is connected to either the other side of the heating cylinder and the supporting member. By providing a relief valve on a line through which pressure oil discharged from the hydraulic cylinder is guided when the piston rod moves with respect to the hydraulic cylinder, the sliding resistance of the piston rod based on the pressure induced in the hydraulic cylinder is reduced. An injection molding machine characterized in that it acts as the back pressure of the screw, That.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of an injection molding machine having a structure according to the present invention. In this figure, reference numeral 10 denotes a main body frame of the injection molding machine, which is not shown, but is close to a mold clamping device (not shown) by a slide base laid on a bed of the injection molding machine as is known. It is movably supported in the separation direction.

Then, with respect to the main body frame 10,
A heating cylinder 14 having a nozzle 12 at the tip is fixedly mounted. The heating cylinder 14
Is heated to an appropriate temperature by known heater means. Further, the main body frame 10 is provided with a material supply path 16 that penetrates the wall of the heating cylinder 14 and opens on the upper surface, and a hopper (not shown) is attached to the material supply path 16. It has become. Then, from inside the hopper, through the material supply path 16,
Injection material is supplied into the heating cylinder 14.

Further, an injection screw 18 is inserted and arranged inside the heating cylinder 14. The injection screw 18 is attached to a sub-frame 30 via a thrust bearing 20 and radial bearings 22 and 24 at a base-side end protruding from the heating cylinder 14. It is supported so as to be rotatable around and immovable in the axial direction. The sub-frame 30 is supported by a guide mechanism (not shown) provided on the main body frame 10 so as to be movable toward and away from the main body frame 10 in a direction parallel to the moving direction of the main body frame 10. ing. That is, the injection screw 18 is displaced in the axial direction with respect to the heating cylinder 14 by the movement of the sub-frame 30 in the approaching / separating direction with respect to the main body frame 10.

One end of a support member 26 for supporting the injection screw 18 in the axial direction via a thrust bearing 20 is connected to a load cell 28 which is a strain gauge type pressure detector fixed to a sub-frame 30. It is mounted by screwing, so that an axial load applied to the injection screw 18 can be measured. Then, from the output of the load cell 28, the injection pressure, the injection holding pressure, and the back pressure can be detected.

Further, a rotary encoder 32 is mounted on the main body frame 10, and the main body frame 1
The rotary encoder 32 is driven via the rack and pinion mechanism 35 when the sub-frame 30 is relatively moved with respect to 0. The rotary encoder 32 can detect the position of the sub-frame 30 relative to the main body frame 10, and thus the position of the injection screw 18 in the heating cylinder 14.

On the other hand, a reciprocally rotatable servomotor 34 is fixedly mounted on the main body frame 10 with its output shaft 36 positioned parallel to the moving direction of the main body frame 10. Further, the main frame 10 is provided with a first drive shaft 38 having a spline groove provided on the outer peripheral surface thereof.
The sub-frame 30 is attached so as to be able to rotate around the axis and to be immovable in the direction of the axis in a state where the sub-frame 30 extends parallel to the moving direction of the sub-frame 30 toward the zero side. Furthermore, a spline nut 4 that is rotatably mounted on the sub-frame 30 and cannot move in the axial direction with respect to the first drive shaft.
2 is assembled by being spline-fitted so as to be relatively displaceable in the axial direction and relatively non-rotatable about the axis.

Further, a cam clutch 40 is mounted on a support portion of the first drive shaft 38 supported by the main body frame 10. The cam clutch 40 allows the rotation of the first drive shaft 38 in only one direction.

The first drive shaft 38 is connected to the output shaft 36 of the servo motor 34 via pulleys 44 and 46 and a toothed belt 48, while the spline nut 42 is connected to pulleys 50 and 52. And toothed belt 54
Is connected to the injection screw 18. Then, by this, the rotational driving force of the servo motor 34 is transmitted to the injection screw 18 via the first drive shaft 38, so that the injection screw 18 is driven to rotate. is there.

In this embodiment, the cam clutch 4
At 0, the rotation direction of the first drive shaft 38 is limited to only one direction, so that the rotation of the injection screw 18 is allowed only in the forward direction in which the injection material is sent forward in the heating cylinder 14. That can be
The reversal is prevented. Further, as is apparent from the above description, in the present embodiment, the first drive shaft 38 and the spline nut 42, the pulleys 44 and 46, the toothed belt 48, and the pulleys 50 and 52 and the toothed belt 54 Is configured.

Further, on the power transmission path of the first power transmission mechanism, a first drive shaft 38 and a pulley 46 are provided.
, A first electromagnetic clutch 56 is interposed. The connection and disconnection of the first electromagnetic clutch 56 causes the first drive shaft 38 of the rotational driving force of the servomotor 34 to rotate.
Communication can be interrupted.

On the other hand, on the both sides of the body frame 10 with the heating cylinder 14 interposed therebetween, second drive shafts 58 each having a ball screw groove formed on the outer peripheral surface thereof are moved toward the sub-frame 30 side. The sub-frame 30 is mounted so as to be rotatable around the axis and immovable in the axis direction in a state of extending in the direction of movement of the sub-frame 30. Furthermore, a ball screw nut 60 fixedly attached to the subframe 30 is screwed to the second drive shaft.

The second drive shafts 58, 58
Are connected to the output shaft 36 of the servomotor 34 via pulleys 62 and 64 and a toothed belt 66. Thus, the rotational driving force of the servo motor 34 is transmitted to the second drive shaft 58, whereby the screw lead of the ball screw mechanism including the second drive shaft 58 and the ball screw nut 60 is formed. The sub-frame 30 is displaced in the approaching / separating direction with respect to the main body frame 10 based on the screw feed action by the above, and the injection screw 18 moves forward and backward in the axial direction with respect to the heating cylinder 14. You will be swayed. As is apparent from the above description, in the present embodiment, the second drive shaft 58, the ball screw nut 60, the pulleys 62 and 64, and the toothed belt 66 constitute a second power transmission mechanism. .

Further, the output shaft 36 of the servomotor 34 is provided on the power transmission path of the second power transmission mechanism.
Between the second electromagnetic clutch 68 and the pulley 62.
Is interposed. Then, the second electromagnetic clutch 6
By the connection and disconnection of 8, the transmission of the rotational driving force of the servo motor 34 to the second drive shaft 58 can be intermittently performed.

Further, hydraulic cylinders 70 are fixedly mounted on the main body frame 10 on both sides of the heating cylinder 14, respectively. These hydraulic cylinders 7
0, 70, the pistons 72, 72 are attached to the main body frame 10 in the cylinder in such a manner that the pistons 72, 72 are slid in parallel to the moving direction of the sub-frame 30, and the piston rod 74,
Each 74 extends toward the sub-frame 30 and is fixedly attached to the sub-frame 30. Thereby, each of these hydraulic cylinders 70
, The sub-frame 3 for the body frame 10
When the injection screw 18 moves relative to the heating cylinder 14 in the axial direction with respect to the relative displacement of 0, the piston 72 slides in the cylinder.

In each of the hydraulic cylinders 70, an oil supply / discharge line for the front cylinder chamber 76 and an oil supply / discharge line for the rear cylinder chamber 78 are connected via a first check valve 80. The first check valve 80 allows only the flow of oil from the front cylinder chamber 76 to the rear cylinder chamber 78. Further, an oil supply / discharge line for the front cylinder chamber 76 is connected to an oil tank 84 via a solenoid valve 82, and when the solenoid valve 82 is excited, the oil is supplied into the front cylinder chamber 76. The supply of oil from the oil tank 84 is allowed.

On the other hand, an oil supply / discharge line for the rear cylinder chamber 78 is formed by two parallel lines, a line provided with a second check valve 86 and a line provided with a relief valve 88. It is connected to an oil tank 84. The supply of oil into the rear cylinder chamber 78 is always allowed by the line on the second check valve 86 side, while the rear cylinder chamber 78 is supplied.
The discharge of oil from inside can be permitted by the line on the side of the relief valve 88 only when the oil pressure in the rear cylinder chamber 78 reaches a set value or more.

In the hydraulic cylinder 70, when the piston rod 74 moves in the projecting direction, the oil pressure in the rear cylinder chamber 78 is increased by the relief valve 88, so that the piston 72 A predetermined sliding resistance can be exerted.

That is, when a continuous molding operation is performed by the injection molding machine having such a structure,
As is known, after the previous molding operation is performed, first, the second electromagnetic clutch 68 is disengaged, the first electromagnetic clutch 56 is connected, the servo motor 34 is rotated, and the injection screw 18 is rotated about the axis. The plasticizing and metering process of the injection material supplied from the material supply path 16 and guided to the front in the heating cylinder 14 is performed by the rotational driving. At this time, since the relative displacement of the sub-frame 30 with respect to the main body frame 10 is allowed by the second drive shaft 58 being idled via the ball screw nut 60, the front When the pressure of the stored injection material is applied in the axial direction of the injection screw 18, the injection screw 18 is retracted in the axial direction with its rotation.

Then, based on the amount of retreat of the injection screw 18 with respect to the heating cylinder 14 measured by the rotary encoder 32, after it is detected that a predetermined amount of injection material has been stored in front of the injection screw 18, Disconnect the first electromagnetic clutch 56, connect the second electromagnetic clutch,
The servo motor 34 is rotated and the subframe 30 is rotated.
Is moved closer to the main body frame 10 to drive the injection screw 18 in the heating cylinder 14 forward in the axial direction, thereby performing an injection step. That is, thereby, the injection material stored in the heating cylinder 14 is extruded by the injection screw 18 and injected and filled into the molding cavity of the mold (not shown).

In such an injection molding operation,
In the screw drive device having the structure as described above,
As the sub-frame 30 approaches and separates from the main body frame 10, the piston rod 74 is moved relative to each hydraulic cylinder 70 in and out of the hydraulic cylinder 70.

In the injection step, the sub-frame 30 is moved in the approaching direction with respect to the main body frame 10, and the piston rod 74 is moved in the direction of entering the hydraulic cylinder 70.
From the front cylinder chamber 76 to the rear cylinder chamber 78
Since the flow of oil into the inside is allowed through the first check valve 80, the movement of the injection screw 18 in the axial direction is hardly affected by the resistance of the hydraulic cylinder 70. In addition, between the front cylinder chamber 76 and the rear cylinder chamber 78 of the hydraulic cylinder 70, the piston 7
Although a relative difference occurs in the volume change amount caused when the 2 moves, surplus oil resulting from the difference in the volume change amount is discharged to the oil tank 84 through the relief valve 88. . At the time of such discharge, the set pressure of the relief valve 88 may be reduced.

On the other hand, in the plasticizing and measuring step, the sub-frame 30 is moved in the direction away from the main body frame 10 and the piston rod 74 is moved in the direction protruding from the inside of the hydraulic cylinder 70. When the solenoid valve 82 is excited, the oil is sucked into the front cylinder chamber 76 without load, but the oil is discharged from the rear cylinder chamber 78 through the relief valve 88. Therefore, the oil pressure in the rear cylinder chamber 78 is raised by the relief valve 88 and maintained at a constant value, and the projecting direction of the piston rod 74 is determined based on the oil pressure in the rear cylinder chamber 78. A predetermined resistance force is exerted on the movement to.

The movement resistance of the piston rod 74 exerted by the hydraulic cylinder 70 can exert a predetermined resistance on the movement of the sub-frame 30 in the direction away from the main body frame 10. Based on the resistance, a pressing force against the axial rearward displacement of the injection screw 18, that is, a back pressure (back pressure) can be effectively exerted.

The resistance force exerted on the piston rod 74 of the hydraulic cylinder 70, that is, the rear cylinder chamber 7
Since the oil pressure in 8 can be maintained at a predetermined set value with sufficient accuracy by the relief valve 88, an extremely stable back pressure can be obtained.
The control accuracy and stability can be dramatically improved as compared with the conventional method of obtaining a back pressure by mechanical braking means.

Furthermore, the hydraulic cylinder 70 in the present embodiment can employ a sufficiently small hydraulic cylinder as compared with the injection cylinder used in a normal hydraulic drive type injection device. Relief valve 88
From the point where it becomes possible to set the set pressure of
Due to the structure of the relief valve, there is an advantage that its operation is stabilized and the back pressure control can be more stably achieved.

Further, in the screw driving device according to the present embodiment, the injection screw 18 can be rotated only in the direction in which the injection material is fed forward by the cam clutch 40 mounted on the first drive shaft 38. Since the reverse rotation of the injection screw 18 in the injection step is prevented, the effect of stabilizing the injection resin amount and the like can be achieved.

Although the embodiment of the present invention has been described above in detail, this is a literal example, and the present invention is not construed as being limited to such a specific example.

For example, the servo motor 34 for driving the injection screw 18 can be fixed to the sub-frame 30 side, so that the first power transmission mechanism has a simpler structure. be able to.

As a driving means of the injection screw,
The servo motor is not limited to the illustrated one.

Furthermore, while the hydraulic cylinder 70 is fixedly mounted on the sub-frame 30 side and the piston rod 74 is connected to the main frame 10, a hydraulic cylinder mechanism is provided between the main frame 10 and the sub-frame 30. May be attached.

Further, the number of hydraulic cylinders is not limited, and one or three or more hydraulic cylinders can be provided.

The oil circuit in such a hydraulic cylinder mechanism is not limited to the one described in the above embodiment, but may exert a back pressure on the injection screw in the plasticizing and measuring process of the injection material. Any direction may be used as long as a predetermined hydraulic pressure is exerted on the piston by the relief valve.

In addition, although not enumerated one by one, the present invention
Based on the knowledge of those skilled in the art, various changes, modifications, improvements and the like can be implemented in an embodiment,
It goes without saying that any of such embodiments are included in the scope of the present invention unless departing from the spirit of the present invention.

[0043]

As described above, in the injection molding machine having the structure according to the present invention, the back pressure of the screw can be obtained based on the hydraulic pressure in the hydraulic cylinder. The control accuracy of the back pressure and its stabilization can be dramatically improved, compared to the structure that obtains the screw back pressure by the conventional mechanical braking means, because it can be set by the relief valve. It has become.

Further, in the injection molding machine according to the present invention, both rotation around the axis of the screw and movement in the direction of the axis are performed by one driving device, and the screw is driven by the hydraulic cylinder. Since there is no need to perform the operation, a small hydraulic cylinder can be used, whereby the set pressure of the relief valve is set to be high, and the operation of the relief valve is further stabilized. It is also possible.

[Brief description of the drawings]

FIG. 1 is an explanatory plan view showing an embodiment of a screw drive device in an injection molding machine having a structure according to the present invention.

[Brief description of reference numerals]

10: Body frame 14: Heating cylinder 18: Injection screw 30: Sub-frame 34: Servo motor 38: First drive shaft 42: Spline nut 44, 46: Pulley 48: Toothed belt 50, 52: Pulley 54: Toothed Belt 56: first electromagnetic clutch 58: second drive shaft 60: ball screw nut 62, 64: pulley 66: toothed belt 68: second electromagnetic clutch 70: hydraulic cylinder 72: piston 74: piston rod 88: Relief valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45/03-45/13 B29C 45/46-45/63 B29C 45 / 70,45 / 76-45 / 82

Claims (1)

(57) [Claims] 1. A driving means having an output shaft rotated about one axis, and a rotational driving force of the driving means is transmitted to a screw inserted and arranged in a heating cylinder, and the screw is rotated about an axis. A first power transmission mechanism for rotating, a first clutch means provided on a power transmission path in the first power transmission mechanism for interrupting transmission of rotational driving force, and a rotational driving force of the driving means. By transmitting the screw with a feed screw action to a supporting member that supports the screw so as to be rotatable about the axis and relatively unmovable in the axial direction, the screw is axially moved through the supporting member. A second power transmission mechanism for moving, and a second clutch means provided on a power transmission path in the second power transmission mechanism for interrupting transmission of rotational driving force. In the injection molding machine including the screw driving device, a hydraulic cylinder is provided on one of a heating cylinder into which the screw is inserted and a supporting member supporting the screw, and the hydraulic cylinder slides in the hydraulic cylinder. The piston rod of the piston to be squeezed is connected to either the other side of the heating cylinder and the supporting member, and a line on which pressure oil discharged from the hydraulic cylinder is guided when the piston rod moves with respect to the hydraulic cylinder. By providing a relief valve,
An injection molding machine characterized in that a sliding resistance of the piston rod based on a pressure generated in the hydraulic cylinder is applied as a back pressure of the screw.