JPH11151736A - Injection device of motor-driven injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate maintenance and control, to enhance the control accuracy of a speed, a position or the like and to easily control a motor. SOLUTION: An injection device has a metering motor 44, the injection motor 45 arranged on the same axis as the metering motor 44, the hollow rotor shaft fixed to the rotor 49 of the injection motor 45, the screw allowed to advance and retreat accompanied by the driving of the injection motor 45 and rotated accompanied by the driving of the motor 44, the ball screw shaft 65 integrally connected to the rotor shaft and the encoder detecting the rotation of the ball screw shaft 65. In this case, since it is unnecessary to use a timing belt in order to allow the screw to advance and retreat or to rotate the same, maintenance and control become easy and the control accuracy of a speed, a position or the like can be enhanced.

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 electric injection molding machine.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, a resin heated and melted in a heating cylinder is injected at a high pressure to fill a cavity space of a mold.
Cooling and solidifying in the cavity space,
The mold is opened and the molded product is taken out.

The injection molding machine has a mold clamping device and an injection device, and the mold clamping device includes a fixed platen and a movable platen, and a mold clamping cylinder moves the movable platen forward and backward to move the mold toward and away from the mold. It has become. On the other hand, the injection device includes a heating cylinder for heating and melting the resin supplied from the hopper, and an injection nozzle for injecting the melted resin, and a screw is disposed in the heating cylinder so as to be able to move forward and backward. The resin can be injected by moving the screw forward, and can be measured by moving the screw backward.

Meanwhile, there has been provided an electric injection molding machine using an electric motor for moving the injection device forward and backward and for moving the screw forward and backward. FIG. 2 is a schematic view of an injection device in a conventional electric injection molding machine. In the figure, reference numeral 2 denotes an injection device, and 4 denotes an injection device frame. A heating cylinder 21 is fixed in front of the injection device frame 4 (to the left in the figure), and an injection nozzle 21a is arranged at the tip of the heating cylinder 21. Is established. A hopper 21 b is provided in the heating cylinder 21, and a screw 20 is provided in the heating cylinder 21 so as to be able to advance and retreat and rotate freely, and the rear end of the screw 20 is rotated by the support member 5. Freely supported.

[0005] A first servomotor 6 is attached to the support member 5, and the rotation of the first servomotor 6 is transmitted to the screw 20 via a timing belt 7a. In addition, the injection device frame 4 includes:
The screw shaft 8 is rotatably supported in parallel with the screw 20, and the screw shaft 8 is connected to the second servomotor 9. That is, the rear end of the screw shaft 8 is connected to the second servomotor 9 via the timing belt 7b.
The screw shaft 8 can be rotated by the servo motor 9. The front end of the screw shaft 8 is screwed with a nut 5 a fixed to the support member 5. Therefore, by driving the second servomotor 9 and rotating the screw shaft 8 via the timing belt 7b,
The nut 5a can be moved in the axial direction.

Next, the operation of the injection device 2 having the above configuration will be described. First, in the measuring step, the first servomotor 6 is driven, the screw 20 is rotated via the timing belt 7a, and the screw 20 is retracted to a predetermined position. At this time, the resin supplied from the hopper 21 b is heated and melted in the heating cylinder 21, and the screw 20
Is stored in front of (left side in the figure).

Next, in the injection step, the injection nozzle 21a is pressed against a mold (not shown), the second servomotor 9 is driven, and the screw shaft 8 is driven via the timing belt 7b.
To rotate. At this time, the support member 5 is moved with the rotation of the screw shaft 8 and advances the screw 20, so that the resin stored in front of the screw 20 is injected from the injection nozzle 21a.

FIG. 3 is a schematic view of another injection device in a conventional electric injection molding machine. In the figure, 2 is an injection device,
Reference numeral 4 denotes an injection device frame. A heating cylinder 21 is fixed in front of the injection device frame 4 (to the left in the drawing), and an injection nozzle (not shown) is provided at a tip of the heating cylinder 21. A screw 20 is disposed inside the heating cylinder 21 so as to be able to advance and retreat and rotate freely. A ball screw 31 is formed at the rear end of the screw 20, and a spline 32 is formed at the rear end of the ball screw 31. Is done.

The injection unit frame 4 is provided with an injection through-type motor 34 corresponding to the ball screw 31. A ball screw nut 37 and the injection through-type motor 34 are fixed, and the spline A metering penetrating motor 35 is provided corresponding to 32, and the spline nut 38 and the metering penetrating motor 35 are fixed. An NC controller 39 is connected to the injection penetrating motor 34 and the metering penetrating motor 35, and the NC controller 39 is controlled to select the injection penetrating motor 34 and the metering penetrating motor 35. Injection and metering can be carried out by rotating them appropriately. That is, in the measuring process, the spline 32, the ball screw 31, and the screw 20 rotate to perform the measurement by rotating the penetrating motor 35 for measurement and simultaneously rotating the penetrating motor 34 for injection at the same rotational speed. Will be At this time, by adjusting the supply of electric power to the injection penetrating motor 34, the difference between the rotation speed of the ball screw nut 37 and the rotation speed of the spline nut 38 allows the screw 2 to rotate.
0 is retracted, and back pressure control at the time of weighing can be performed.

Further, in the injection step, when the injection penetrating motor 34 is rotated to prevent the metering penetrating motor 35 from rotating, the ball screw 31 is advanced by the rotation of the ball screw nut 37. As a result, screw 2
Zero is also advanced and injection is performed.

[0011]

However, in the injection device of the conventional electric injection molding machine, the timing belts 7a and 7b are used in the case of the injection device shown in FIG. Will occur.
In addition, since the timing belts 7a and 7b wear, maintenance and management are troublesome, and the elasticity of the timing belts 7a and 7b lowers the control accuracy of speed, position, and the like.

On the other hand, in the case of the injection device shown in FIG. 3, a ball screw 31 and a spline 32 are integrated, and a ball screw nut 37 screwed with the ball screw 31 is rotated by an injection penetrating motor 34 so that the spline The spline nut 38, which is spline-coupled to the spline nut 32,
5 rotates. Then, for example, when measuring, the back pressure is applied to the screw 20 by increasing the rotation speed of the injection penetration motor 34 and decreasing the rotation speed of the measurement penetration motor 35. Therefore, it is necessary to operate the penetrating motor 35 for measurement and the penetrating motor 34 for injection in synchronization, and it is difficult to control the penetrating motor 35 for measurement and the penetrating motor 34 for injection, and the accuracy of back pressure control is high. Will decrease.

The present invention solves the problems of the injection device of the conventional electric injection molding machine, which facilitates maintenance and management, improves control accuracy of speed, position, etc., and facilitates the motor. An object of the present invention is to provide an injection device of an electric injection molding machine that can be controlled.

[0014]

For this purpose, an injection device for an electric injection molding machine according to the present invention comprises a measuring motor,
An injection motor disposed on the same axis as the weighing motor, a hollow rotor shaft fixed to a rotor of the injection motor, and an advancing / retreating device driven by the injection motor; A screw that is rotated with the driving of the motor for use, a ball screw shaft integrally connected to the rotor shaft, and an encoder that detects rotation of the ball screw shaft.

[0015] In another injection device for an electric injection molding machine according to the present invention, there is further provided a ball nut screwed with the ball screw shaft and advanced and retracted with the rotation of the ball screw shaft.
A spline nut connected to the rotor shaft of the measuring motor; and a spline shaft spline-connected to the spline nut and rotatably supported by the ball nut.

Then, the spline shaft and the screw are connected.

[0017]

According to the present invention, as described above, in the injection device of the electric injection molding machine, the measuring motor, the injection motor disposed on the same axis as the measuring motor, the injection motor, A hollow rotor shaft fixed to a motor rotor,
A screw that is moved forward and backward with the drive of the injection motor, and is rotated with the drive of the metering motor, a ball screw shaft integrally connected to the rotor shaft, and a rotation of the ball screw shaft. And an encoder for detecting.

In this case, in the injection step, when the injection motor is driven to rotate the rotor, the rotation of the rotor is transmitted to the rotor shaft, and the ball screw shaft integrally connected to the rotor shaft rotates. , The screw is advanced. As a result, the resin stored in front of the screw is injected from the injection nozzle. Next, in the measuring step, when the measuring motor is driven, the screw is rotated. At this time, the injection motor is rotated in a direction to retract the screw while controlling the back pressure of the measured resin.

In another injection device for an electric injection molding machine according to the present invention, there is further provided a ball nut screwed with the ball screw shaft and advanced and retracted with the rotation of the ball screw shaft.
A spline nut connected to the rotor shaft of the measuring motor; and a spline shaft spline-connected to the spline nut and rotatably supported by the ball nut.

Then, the spline shaft and the screw are connected. In this case, in the injection step, when the injection motor is driven to rotate the rotor, the rotation of the rotor is transmitted to the ball screw shaft via the rotor shaft. Then, thrust is generated in the ball nut by the rotation of the ball screw shaft, and the ball nut is advanced.

At this time, the weighing motor is not driven and is in a stopped state. Therefore, the spline shaft is advanced without rotating, and advances the screw. As a result, the resin stored in front of the screw is injected from the injection nozzle. Next, in the measuring step, when the measuring motor is driven, the rotation is transmitted to the spline shaft. Then, the rotation of the spline shaft is transmitted to the screw, and the screw is rotated. At this time, the injection motor is rotated in a direction to retract the screw while controlling the back pressure of the measured resin.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a driving unit of an injection device according to an embodiment of the present invention, and FIG. 4 is an exploded view of a driving unit of the injection device according to the embodiment of the present invention. In the figure, 1
Reference numeral 1 denotes a drive unit case, and the drive unit case 11 is fixed to the rear of the heating cylinder 12 (to the right in FIG. 1).
The drive unit case 11 includes a front cover 13, a front support 14, a center support 15, and a rear support 1.
6, the rear cover 17, the front frame 41 and the rear frame 42. The front cover 13 and the front support 14 are fixed by bolts 18, and the rear support 16 and the rear cover 17 are fixed by bolts 19.

A metering motor 44 is provided at a front portion of the drive unit case 11 and an injection motor 45 is provided at a rear portion thereof on the same axis. The metering motor 44 includes a stator 46 fixed to the front frame 41,
And an injection motor 45 includes a stator 48 fixed to the rear frame 42, and a rotor 49 disposed on the inner peripheral side of the stator 48. Become.

The rotor 47 is rotatably supported by the drive case 11. For this purpose, a hollow first rotor shaft 56 is fitted and fixed to the rotor 47, and the front end of the first rotor shaft 56 is attached to the front support 14 by the bearing 51, and the rear end is attached to the center support 15 by the bearing 52. Supported.

On the other hand, the rotor 49 is also connected to the drive unit case 11.
Is rotatably supported with respect to. Therefore, the rotor 4
9, a hollow second rotor shaft 57 is fitted and fixed, and the front end of the second rotor shaft 57 is
The center support 15 and the rear end of the bearing 54
Supported by the rear support 16. By the way, in the measuring motor 44, by supplying a current of a predetermined frequency to the stator 46, a screw (not shown) can be moved backward while rotating. To this end, a spline nut 62 is fixed to the inner periphery of the front end of the first rotor shaft 56, and the spline nut 62
And the spline shaft 63 are spline-connected, and the screw is fixed to the front end of the spline shaft 63. Therefore, the rotation of the rotor 47 is controlled by the first rotor shaft 56,
The power is transmitted to the screw via the spline nut 62 and the spline shaft 63. Further, since the spline nut 62 and the spline shaft 63 are spline-connected,
The spline shaft 63 can be retracted relatively to the spline nut 62.

On the other hand, in the injection motor 45, by supplying a current of a predetermined frequency to the stator 48, the screw can be advanced. Therefore, an annular bearing retainer 64 is fixed to the rear end of the second rotor shaft 57, and a ball screw shaft 65 is fitted and fixed to the inner periphery of the bearing retainer 64. The ball screw shaft 65 is rotatably supported by the drive unit case 11. That is, the ball screw shaft 65 is connected to the bearing 6 via the bearing retainer 64.
6, and is supported by the rear cover 17 by a bearing 67 disposed rearward of the bearing 66 (to the right in FIG. 1).

A ball nut 69 is provided inside the second rotor shaft 57 so as to be able to advance and retreat.
And screwed. Therefore, the rotation of the rotor 49 is transmitted to the ball screw shaft 65 via the second rotor shaft 57 and the bearing retainer 64 to move the ball nut 69 forward and backward. At this time, a spline shaft 71 is fixed to the front end of the ball nut 69 so that the ball nut 69 does not rotate together with the ball screw shaft 65, and a spline nut 76 fixed to the center support 15.
And the spline shaft 71 are spline-connected.

A bearing box 72 is fixed to the front end of the spline shaft 71, and a thrust bearing 73 is provided in the bearing box 72 at the front and a bearing 74 at the rear. Therefore, the spline shaft 63 is connected to the spline shaft 71 and the ball nut 69 by the thrust bearing 73 and the bearing 74.
Is rotatably supported with respect to. 85 is an absolute value pulse encoder, 86 is the absolute value pulse encoder 85
It is a bracket that supports.

Next, the operation of the driving unit of the injection device having the above-described configuration will be described. First, in the injection process, when a current is supplied to the stator 48 of the injection motor 45, the rotor 4
9 is rotated, and the rotation of the rotor 49 is transmitted to the ball screw shaft 65 via the second rotor shaft 57 and the bearing retainer 64. And, the ball screw shaft 65
A thrust is generated in the ball nut 69 by the rotation of the ball nut 69, and the ball nut 69 is advanced.

At this time, the metering motor 44 is not operated, and the rotor 47 is in a stopped state. Therefore, the spline shaft 63 disposed in front of the ball nut 69 is
The screw is advanced without rotating, and the screw is advanced. As a result, the resin stored in front of the screw can be injected from an injection nozzle (not shown).

Next, in the measuring step, the measuring motor 4
When a current is supplied to the stator 46, the rotor 47 is rotated, and the rotation of the rotor 47 is controlled by the spline shaft 6
3 is transmitted. Then, the rotation of the spline shaft 63 is transmitted to the screw, and the screw can be rotated and retracted. At this time, the injection motor 4
5 is rotated in a direction to retract the screw while controlling the back pressure of the resin to be measured.

As described above, since there is no need to use a timing belt for moving the screw forward and backward, and rotating the screw, no noise is generated at the time of driving, maintenance and management are easy, and speed, position, etc. Control accuracy can be improved. Since the spline shaft 63 and the ball nut 69 can be relatively rotated by the thrust bearing 73 and the bearing 74, it is necessary to drive the measuring motor 44 and the injection motor 45 in synchronization. Therefore, the control of the weighing motor 44 and the injection motor 45 is facilitated.

As shown in FIG. 4, the driving portion of the injection device having the above-described structure can be separated into a motor assembly 81 and a driving shaft assembly 82. In this case, the motor assembly 81 includes the front support 14, the center support 15, the rear support 16, and the front frame 4.
1, a rear frame 42, a measuring motor 44, an injection motor 45, a first rotor shaft 56, a second rotor shaft 57, a spline nut 62, a spline nut 76, and the like. The drive shaft assembly 82 includes a spline shaft 63, a bearing retainer 64, and a ball screw shaft 6.
5, a ball nut 69, a spline shaft 71, a bearing box 72 and the like.

Therefore, after the motor assembly 81 and the drive shaft assembly 82 are separately formed, the measuring motor 44 and the injection motor 4 of the motor assembly 81 are formed.
5 can be driven to check the operation of each unit. Thereafter, the drive shaft assembly 82 is inserted, the front cover 13 and the rear cover 17 are fixed, and the operation of the drive unit can be checked.

Further, the motor assembly 81 and the drive shaft assembly 82 can be separately maintained and managed. When the second rotor shaft 57 is rotated by driving the injection motor 45 in the injection step, the ball screw shaft 65 rotates. However, the absolute rotation position of the ball screw shaft 65 is determined by the absolute value pulse. Encoder 8
5 can be detected. For this purpose, a bracket 86 is fixed to the rear cover 17, and an absolute value pulse encoder 85 is attached to the bracket 86 by the ball screw shaft 6.
5 and is disposed so as to face the end.

Therefore, the absolute value pulse encoder 85
The position of the ball nut 69 is calculated based on the rotation absolute position signal (absolute signal) output by the controller and the lead of the ball screw shaft 65 (the amount of advance of the ball nut 69 per rotation), and the position control of the screw is performed. It can be performed. In this case, if there is play (backlash) between the ball screw shaft 65 and the ball nut 69,
A deviation occurs between the actual position of the ball nut 69 and the position obtained by the calculation. However, the ball screw shaft 6
By using a preload ball screw device as 5, the deviation can be almost eliminated. As described above, since the power transmission mechanism is not interposed between the rotor 49 and the ball screw shaft 65, the position of the ball nut 69 can be accurately detected.

When a servo motor is used as the injection motor 45, an absolute value pulse encoder 85 for motor control is provided, and the number of rotations, pulses, etc. of the rotor 49 detected by the absolute value pulse encoder 85 are determined. Feedback is performed to control the position and speed of the screw. In this embodiment, the rotor 4
9 and the ball screw shaft 65 are connected via the second rotor shaft 57 and the bearing retainer 64,
There is no deviation between the rotation speed of the rotor 49 and the rotation speed of the ball screw shaft 65. Therefore, the rotation signal (incremental signal) of the ball screw shaft 65 is transmitted to the injection motor 45.
Can be used for the control of

As described above, not only the position of the ball nut 69 can be detected by the absolute value pulse encoder 85, but also the position control and speed control of the screw can be performed. Therefore, there is no need to provide an encoder for driving the injection motor 45, so that the cost can be reduced. It should be noted that the present invention is not limited to the above-described embodiments, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0039]

As described above in detail, according to the present invention, in the injection apparatus of the electric injection molding machine, the measuring motor and the injection motor arranged on the same axis as the measuring motor are provided. A motor, a hollow rotor shaft fixed to a rotor of the injection motor, a screw that is moved forward and backward with the drive of the injection motor, and is rotated with the drive of the weighing motor, and the rotor shaft. A ball screw shaft integrally connected to the motor, and an encoder for detecting rotation of the ball screw shaft.

In this case, there is no need to use a timing belt to move the screw forward or backward, or to rotate the screw.
Management becomes easy, and control accuracy of speed, position, and the like can be improved. In addition, since the rotation of the ball screw shaft is detected by the encoder, position control, speed control, and the like of the screw can be easily performed. Therefore, there is no need to provide an encoder for driving the injection motor, so that the cost of the injection device can be reduced.

In another injection device for an electric injection molding machine according to the present invention, a ball nut screwed into the ball screw shaft and advanced and retracted with the rotation of the ball screw shaft is further provided.
A spline nut connected to the rotor shaft of the measuring motor; and a spline shaft spline-connected to the spline nut and rotatably supported by the ball nut.

Then, the spline shaft and the screw are connected. In this case, since the spline shaft and the ball nut can rotate relative to each other, it is not necessary to drive the measuring motor and the injection motor in synchronization with each other,
The metering motor and the injection motor can be easily controlled.

[Brief description of the drawings]

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

FIG. 2 is a schematic view of an injection device in a conventional electric injection molding machine.

FIG. 3 is a schematic view of another injection device in a conventional electric injection molding machine.

FIG. 4 is an exploded view of a driving unit of the injection device according to the embodiment of the present invention.

[Explanation of symbols]

 44 Metering motor 45 Injection motor 47, 49 Rotor 56 First rotor shaft 57 Second rotor shaft 62 Spline nut 63 Spline shaft 65 Ball screw shaft 69 Ball nut 85 Absolute value pulse encoder

Claims (2)

[Claims] (A) a measuring motor; and (b) an injection motor arranged on the same axis as the measuring motor.
(C) a hollow rotor shaft fixed to a rotor of the injection motor; and (d) a screw that is moved forward and backward with the drive of the injection motor and rotated with the drive of the metering motor. An injection device for an electric injection molding machine, comprising: (e) a ball screw shaft integrally connected to the rotor shaft; and (f) an encoder for detecting rotation of the ball screw shaft. 2. A ball nut screwed into the ball screw shaft and moved forward and backward with the rotation of the ball screw shaft; and (b) a spline nut connected to a rotor shaft of the weighing motor. (C) having a spline shaft spline-connected to the spline nut and rotatably supported by the ball nut;
The injection device for an electric injection molding machine according to claim 1, wherein (d) the spline shaft and the screw are connected.