JPH05154882A - Injection methcanism of motor-operated molding machine - Google Patents

Abstract

PURPOSE:To improve a transmission efficiency by a method wherein rotation of a servomotor is converted to a linear motion through a screw shaft for moving a screw, and the screw shaft is placed on the axis of the screw. CONSTITUTION:A screw 20 in an injection heating cylinder 21 is held by a holding member 25, which can move forward and backward, through an extension shaft 26 provided at the rear end of the screw 20. A screw shaft 30 rotating at a fixed position is screwed into a screw accepting member 27 provided on the screw holding member 25. The rotational motion of the screw shaft 30 is converted to a linear motion through the screw shaft 30 and the screw accepting member 27. The screw holding member 25 is moved forward together with the screw 20. As a rotational drive source of the screw shaft 30 and the screw 20, a servo motor 35 is used. A space 25a is formed in a center of the screw holding member 25. The screw shaft 30 screwed into the screw accepting member 27 is disposed on the axis of the screw 20 and contained in the space 25a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mechanism of an electric molding machine for molding synthetic resin using an electric motor as a drive source, and more particularly to an in-line screw injection mechanism having an injection screw in an injection heating cylinder. ..

[0002]

2. Description of the Related Art As an injection mechanism of an electric molding machine, a plunger type mechanism described in Japanese Utility Model Publication No. 39-10424 is known.

In this injection mechanism, a sliding plate is supported by a pair of tie bars, and a rear end of a plunger is attached to the front surface of the sliding plate, while an axial key groove is formed in the shaft portion on the rear surface of the sliding plate. A screw shaft having is rotatably connected, a pulley rotating at a fixed position is screwed to the screw shaft, and a worm wheel is meshed with a shaft portion via a key,
The rotation of the shaft is blocked by the worm wheel, and then the pulley is rotated by the electric motor to change the rotational movement into the linear movement of the screw shaft to move the plunger forward or backward.

[0004]

In such a plunger type injection mechanism, since the plunger is moved forward together with the screw shaft for injection, a rotation resistance member such as a key and a worm wheel for preventing rotation of the screw shaft, A resistance machine that gives rotation resistance to the worm wheel is required, and since the rotation movement of the pulley by the electric motor is converted into the linear movement of the screw shaft by the key and key groove while giving rotation resistance to the screw shaft, Since the resistance is large and the transmission efficiency is extremely poor, a high-output electric motor is required.

Further, a commonly used ordinary electric motor has a difficulty in starting, stopping, and rapid acceleration / deceleration control of the electric motor, and torque control is also difficult, and a wide range from low speed to rated speed is controlled with high accuracy. For this reason, it was difficult to use as a drive source for an in-line screw type injection mechanism that requires high-speed response.

Further, unlike the plunger type, the in-line screw type requires a measuring step of plasticizing the material resin by controlling the back pressure while rotating the screw. When the screw is rotated to plasticize the material resin after the injection is completed, the screw moves backward due to the pressure of the molten resin extruded from the screw into the front part of the injection heating cylinder.

During this backward movement, in order to enhance the plasticizing and kneading effects of the material resin, and to release the volatile components and air in the material to the rear of the screw, back pressure is applied to the screw to control the backward movement. ..

Since this back pressure control is performed with high precision only by the smooth backward movement of the screw, the compression by the forward movement of the plunger and the heater
It is extremely difficult to adopt the above-mentioned injection mechanism for the plunger type, which sequentially plasticizes the material resin in the heating cylinder, to the injection mechanism of the in-line screw type, and therefore, the injection mechanism of the in-line screw type in which the drive source is an electric motor is used. As for the injection mechanism, solving the problems of the electric motor and the problem of transmission to the screw has been a problem.

The present invention was conceived in order to solve the above problems, and an object thereof is to convert the rotational motion of an electric motor into a linear motion by a screw shaft to move the screw forward. It is an object of the present invention to provide a new injection mechanism of an electric molding machine that enables smooth movement of a screw and uses an electric motor having a high responsiveness to enable injection molding with high molding accuracy.

Further, according to the present invention, even if the screw shaft is used as the forward moving means of the screw, the injection mechanism of the new electric molding machine can be made compact and the transmission efficiency can be further enhanced. It is also provided.

[0011]

According to the features of the present invention according to the above object, there is provided a screw in an injection heating cylinder having an extension shaft at a rear end thereof, and the extension shaft having a transmission member for screw rotation.
A screw holding member that holds the screw rotatably via the extension shaft and that moves back and forth together with the screw is screwed into a screw receiving member provided on the screw holding member, and the rotational movement is converted into a linear movement by the screw receiving member. A screw shaft in a fixed position for converting and moving the screw holding member forward together with the screw,
In an injection mechanism that uses a servomotor as a drive source of a screw shaft and a transmission member for rotating a screw, a central portion of the screw holding member is formed in a void, and the extension shaft is provided in front of the void through a member. The screw receiving member is rotatably connected, and the screw receiving member is fixed to the rear portion of the space, and the screw shaft is positioned on the axis of the screw by screwing the screw receiving member and the screw shaft, and the screw holding member. It will be housed in.

[0012]

[Operation] In the above configuration, when the servomotor rotates normally, the screw shaft screwed with the screw receiving member on the screw holding member side rotates. Since this screw shaft is located on the axis of the screw and does not move in the axial direction, the screw holding member side moves forward, whereby the screw moves forward in the injection heating cylinder to perform injection.

Further, when the servomotor is rotated in the reverse direction and the rotation is transmitted to the screw via the rotation transmission member, the screw rotates to plasticize the material resin, and the resin feed pressure causes the screw to retreat. Works. This retreating force acts on the screw shaft via the screw holding member, whereby the screw shaft rotates in the direction opposite to that in the forward movement, so that the screw moves smoothly backward together with the screw holding member.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, 1 is a mold clamping mechanism and 2 is an injection mechanism. The mold clamping mechanism 1 has a tie bar 12 installed on a pair of fixed plates 10 and 11 on the machine base 3, and a movable plate 13 movably attached to the tie bar 12.

Molds 14 and 14 are provided on the opposing surfaces of the fixed plate 11 and the movable plate 13, respectively, and a screw shaft 15 for opening and closing the mold is provided on the opposite surface of the movable plate 13 in a protruding manner. I am doing it. This screw shaft 15 is screwed into a rotary plate 16 rotatably mounted on the other fixed plate 10 and
A gear 17 is attached to the mold 17 and constitutes a mold opening / closing device in which the screw shaft 15 moves together with the movable plate 13 by a screw lead when the rotary plate 16 rotates together with the gear 17.

The injection mechanism 2 has an injection heating cylinder 21 in which the screw 20 is housed, and a movable housing 22 on the machine base which also holds the injection heating cylinder 21. Inside the housing 22, a rear end portion of the screw 20 and a screw holding member 25 are slidably accommodated only in the front-rear direction.

At the rear end of the screw 20, an extension shaft 26 provided with a transmission member for screw rotation by a gear 24 is continuously provided, and the end portion of the extension shaft 26 is held by the member 23 to hold the screw. It is rotatably connected to the member 25.

The central portion of the screw holding member 25 is formed in an axially long space 25a with both ends open, the member 23 is provided in the front part of the space 25a, and a nut-shaped screw is provided in the rear part. The receiving member 27 is fixed and fitted to the screw holding member side.

A screw shaft 30 at a fixed position, which is rotatably held by the casing wall portion 22a, is screwed into the screw receiving member 27. As a result, the screw shaft 30 is attached to the screw 2
It is located on the axis 0 and is housed inside the screw holding member 25.

The screw shaft 30 has a casing wall 22a.
The shaft 29 held by the shaft 29 has a rotation transmission member by a gear 28, and a back pressure control brake 31 fixed to the housing wall 22a is connected to the outer end of the shaft 29. The brake 31 has a hysteris brake inside.

Reference numeral 32 denotes a transmission shaft on the side of the mold clamping mechanism, which is rotatably supported by the lower portions of the fixed plates 10 and 11 and which is in close proximity to the fixed plate 10 and meshes with the gear 17 to form a transmission gear 33.
At the outer end and a key or spline at the inner end.

Reference numeral 34 is a transmission shaft on the injection mechanism side which is supported in the lower portion of the housing 22, and 35 is a servomotor having a tachometer generator 35a. The servo motor 35 is attached to the housing 22 by a connecting member 22b and is provided inside the machine base 3 so as to move together with the housing 22.

The rotational force of the servomotor 35 is transmitted to the transmission shaft 34 by the drive belt 36, and the transmission shaft 34 is rotated. Further, a joint 37 for connecting the transmission shaft 32 on the mold clamping mechanism side is connected to the inner end of the transmission shaft 34 via an electromagnetically actuated clutch mechanism 38 so as to be freely contactable and separable. This joint 37 is rotatable and slidable so that the housing 2
2 and a cylinder 37a which is integrally formed at the outer end of the shaft and has a key groove or spline inside which receives the inner end of the transmission shaft 32. An electromagnetically-actuated mold clamping force retainer 39 is provided.

The mold clamping force retainer 39 is composed of a braking plate fixed to the housing wall and an electromagnet which is keyed to the shaft so as to be movable in the axial direction. The electromagnet is excited to act as the braking plate. They are connected to each other and hold the mold clamping force through the transmission shaft 32.

A transmission gear 40 is provided on the transmission shaft 34 together with an electromagnetically actuated clutch mechanism 40a, and meshes with the gear 28 for rotating the screw shaft. Reference numeral 41 is a transmission gear provided on the transmission shaft 34 together with an electromagnetically actuated clutch mechanism 41a, and meshes with the gear 24 for screw rotation.

Next, the operation of the molding machine using the servo motor 35 as a drive source will be described. While the transmission shafts 32 and 34 are connected by the clutch mechanism 38, the servo motor 35
Rotate forward. At this time, on the injection mechanism 2 side, the transmission gears 40, 41 are kept free by the operation of the clutch mechanisms 40a, 41a.

The rotary disk 16 is rotated by the transmission shaft 34, the transmission gear 33 and the gear 17, and the screw shaft 15 is sent out. As a result, the movable platen 13 moves forward to move the molds 14, 1
4 closes.

When the movable platen 10 is stopped by closing the mold, a large torque is generated and the current increases. At this time, the set torque is compared with the detected current, and when a coincidence confirmation signal is generated, the mold clamping force holder 39 is excited and the transmission shaft 32 is fixed to the brake housing side. By fixing the transmission shaft 32, the movable platen 13 maintains the mold clamping state.

In this state, the rotating force acts on the transmission shaft 32, so that following the excitation of the mold clamping force retainer 39, the clutch mechanism 38 is electrically opened to disconnect the transmission shaft 34.

Following the above operation, on the injection mechanism 2 side,
In response to the command, the clutch mechanism 40a in the free state is activated to connect the transmission shaft 34 and the transmission gear 40. As a result, the rotational force of the servomotor 35 is transmitted to the screw shaft 30 via the transmission gear 40 and the gear 28 for rotating the screw shaft.

Since the screw shaft 30 only rotates at a fixed position by the gear 28, the screw receiving member 27 on the screw holding member side screwed with the screw shaft 30 feeds the screw shaft in the axial direction. Then, the rotational movement by the servomotor is converted into the linear movement for moving the screw holding member 25 forward.

Since the extension shaft 26 at the rear end of the screw is connected to the screw holding member 25, the screw 20 also moves forward together and injects the measured material resin into the injection heating cylinder at the front of the screw. ..

When the injection is completed, the servomotor 35 is stopped by the command, and at the same time, the clutch mechanism 40a is operated in the original free state to cut off the transmission of the rotational force to the gear 28 for rotating the screw shaft. Following this operation, the clutch mechanism 41a in the free state is operated to connect the transmission shaft 34 and the transmission gear 41.

Then, when the servo motor 35 is rotated in the reverse direction,
The rotational force is transmitted to the screw 30 via the transmission gear 41 and the gear 24 for rotating the screw, and the screw 30
Rotates to feed the material resin from the hopper to the front of the screw.

The rotation of the screw 20 plasticizes the material resin to form a molten resin, which is measured in the front portion of the injection heating cylinder 21. Further, the resin pressure in the injection heating cylinder causes a backward force of the screw 20. This retracting force is concentrated on the screw receiving member 27 integrated with the screw holding member 25, and acts on the screw shaft 30 on the same axis as the screw 20, so that the screw shaft 30 moves smoothly in the opposite direction to the screw forward direction. It does not prevent the screw 20 from moving backward.

When the reverse rotation of the screw shaft 30 is braked by the brake device 31, the screw 20 moves backward while resisting the finger pressure, and a proper back pressure is measured there.

After the measurement, on the mold clamping mechanism 1 side, the mold clamping force holder 39 is released, and the clutch mechanism 38 is operated to connect the transmission shaft 32 to the transmission shaft 34 again, and the servo motor 35.
The reverse rotation force of is transmitted to the turntable 16. As a result, the screw shaft 15 on the mold clamping side moves backward while rotating backward to open the mold.

[0038]

As described above, according to the present invention, the screw in the injection heating cylinder having the extension shaft at the rear end and the transmission member for rotating the screw on the extension shaft and the screw via the extension shaft are provided. A screw holding member that rotatably holds and moves back and forth together with a screw and a screw receiving member provided on the screw holding member are screwed together, and the rotational movement is converted into a linear movement by the screw receiving member to form a screw holding member. An injection mechanism is composed of a fixed-position screw shaft that moves forward together with the screw, and a servomotor that serves as a drive source for the screw shaft and a transmission member for rotating the screw, and the central portion of the screw holding member is vacant. The screw shaft is formed and the extension shaft is rotatably connected to the front part of the space through a member, and the screw receiving member is fixed to the rear part of the space, and the screw receiving member and the screw shaft are connected to each other. By screwing, the screw Since the shaft is located on the axis of the screw and housed in the screw holding member, the following effects are achieved.

Since the screw holding member side is moved forward by the screw shaft in the fixed position, GD ² can be made smaller as compared with the case where the screw receiving member side is rotated, which allows precise injection control and metering control with high response. Is possible.

Since the screw shaft in the fixed position moves forward on the screw holding member side, the rotation preventing member for the screw shaft, which is indispensable for the plunger type injection mechanism moving forward on the screw shaft side, is unnecessary, and the screw by the rotation preventing member is not necessary. Since the rotation resistance of the shaft is also eliminated, the transmission efficiency is significantly improved, and the screw shaft rotates smoothly.

The screw holding member which can move forward and backward and the screw shaft are connected to each other by screwing the screw receiving member and the screw shaft, and the backward force of the screw applied to the screw holding member is concentrated on the screw receiving member. Therefore, the reverse force of the screw shaft smoothly occurs due to the retracting force, and even when the screw is retracted by the finger pressure when measuring the material,
Since the resistance by the screw shaft is extremely small, the back pressure control by the rotation control of the screw shaft can be easily performed.

The servomotor can perform not only start, stop, rapid acceleration / deceleration control, but also torque control and speed control over a wide range from low speed to rated speed with high accuracy and high response, and rotation of the screw by the servomotor. Since it is possible to meet the requirements of high load durability when measuring materials and highly accurate adjustment characteristics, the drive source is an electric motor in combination with the good transmission efficiency of the screw shaft. However, as a result of achieving highly accurate and stable plasticization measurement, it is possible to form a molded product with extremely high molding accuracy.

Since the screw and the screw shaft are on the same axis, even if the screw and the screw shaft are connected to each other through the screw holding member, the forward force with respect to the screw and the backward force with respect to the screw shaft may be biased. In addition, the screw shaft does not rotate smoothly, which causes the backward movement of the screw.

Since the central portion of the screw holding member is formed in the empty space to accommodate the screw shaft, the length of the injection drive unit can be shortened by the amount of accommodation of the screw shaft, and the screw shaft is rotated, so that the screw shaft is rotated. Since it is not necessary to increase the length of the extra length and the length of the screw shaft can be shortened accordingly, the injection mechanism can be made compact.

[Brief description of drawings]

FIG. 1 schematically shows an embodiment of an injection mechanism of an electric molding machine according to the present invention, and is a side view in which the injection mechanism is longitudinally cut.

[Explanation of symbols]

 1 Clamping Mechanism 2 Injection Mechanism 20 Screw 21 Injection Heating Tube 22 Housing 22a Housing Wall 23 Member 24 Screw Rotation Gear 25 Screw Holding Member 25a Void 26 Extension Shaft 27 Screw Receiving Member 28 Screw Shaft Rotation Gear 29 Screw Shaft part 30 Screw shaft 34 Transmission shaft 35 Servo motor 40 Screw shaft rotation side transmission gear 40a Clutch mechanism 41 Screw rotation side transmission gear 41a Clutch mechanism

Claims (1)

[Claims] A screw in an injection heating cylinder that has an extension shaft at the rear end and a transmission member for screw rotation on the extension shaft, and a screw that rotatably holds through the extension shaft and that moves forward and backward together with the screw. A member and a screw shaft at a fixed position for screwing together with a screw receiving member provided on the screw holding member, converting rotational movement into linear movement by the screw receiving member, and moving the screw holding member forward together with the screw. In an injection mechanism that uses a servomotor as a driving source for a screw shaft and a screw rotation transmission member, a central portion of the screw holding member is formed in a void, and the extension shaft is provided in front of the void through a member. The screw holding member is rotatably connected, and the screw receiving member is fixed to the rear portion of the space, and the screw shaft is positioned on the axis of the screw by screwing the screw receiving member and the screw shaft together. Injection mechanism of an electric molding machine, characterized in that accommodated composed.