JP3145678B2 - Electric 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 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, filled into a cavity space of a mold, and cooled in the cavity space. After solidification, the mold is opened and the molded product is taken out.

The injection molding machine has a mold clamping device and an injection device. The mold clamping device has a fixed platen and a movable platen, and a mold clamping cylinder moves the movable platen forward and backward to move 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, and FIG. 3 is an enlarged view of a main part of the 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. And
A hopper 21b 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 rotatably supported by the support member 5. Is done.

[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. The injection device frame 4 has 2
The guide bars 24 are provided, and the support members 5 are slidably supported by the respective guide bars 24. A ball screw shaft 8 is rotatably supported by the injection device frame 4 in parallel with a screw 20 via a bearing (not shown), and a rear end of the ball screw shaft 8 is connected to a timing belt 7b via a timing belt 7b. The ball screw shaft 8 can be rotated by driving the second servo motor 9 and connected to the second servo motor 9. The front end of the ball screw shaft 8 is
The ball nut 5a fixed to the rotation support plate 5b of the support member 5 is screwed.

Accordingly, by driving the second servomotor 9 and rotating the ball screw shaft 8 via the timing belt 7b, the ball nut 5a can be moved in the axial direction, and the screw 20 can be moved forward and backward.
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 21b is heated and melted in the heating cylinder 21, and is stored (stored) in front of the screw 20 (left side in the figure) as the screw 20 retreats.

Next, in the injection step, the injection nozzle 21a is pressed against a mold (not shown), the second servomotor 9 is driven, and the ball screw shaft 8 is rotated via the timing belt 7b. At this time, the bolt and nut 5a and the rotation support plate 5b are moved with the rotation of the ball screw shaft 8 to advance the screw 20, so that the resin accumulated in front of the screw 20 is injected from the injection nozzle 21a. Is done.

In the injection step, the injection device 2
Is detected, and the pressure of the resin charged into the cavity space (not shown) is controlled based on the detected output. Therefore, usually, as shown in FIG.
A load meter 25 is provided between the ball nut 5a and the rotation support plate 5b.

[0009]

However, in the injection device of the conventional electric injection molding machine, since the timing belts 7a and 7b are used, not only noise is generated at the time of driving, but also noise is generated. , Screw 2
Since the first servomotor 6 and the second servomotor 9 are not arranged on the 0 axis, the size of the injection device 2 is increased. Further, since the timing belts 7a and 7b are worn, not only is maintenance and management troublesome, but also the timing belt 7
Due to the elasticity of a and 7b, the control accuracy of the speed, the position and the like is reduced.

To solve this problem, an in-line type injection device having a built-in servomotor is conceivable. However, if the servomotor is to be built-in, a ball nut will be incorporated in the servomotor. As a result, the load meter arranged adjacent to the ball nut will also be incorporated into the servomotor, which not only reduces the work of mounting the load meter and the wiring process, but also reduces maintenance and management. It gets annoying.

The present invention provides an electric injection molding machine which solves the problems of the conventional electric injection molding machine, improves the assemblability of the load cell, and simplifies maintenance and management. The purpose is to do.

[0012]

For this purpose, in the electric injection molding machine according to the present invention, a heating cylinder, a screw disposed in the heating cylinder so as to be able to advance and retreat and rotate freely, and the heating cylinder are provided. A drive unit case connected to the rear of the cylinder, a stator fixed to the drive unit case, an injection motor consisting of a rotor connected to the screw, and a ball screw disposed on the same axis as the rotor A movement direction conversion means for converting the rotational movement of the rotor into a linear movement, and a movement direction conversion means for converting the rotational movement of the rotor into a linear movement; A load cell for detecting a thrust force.

In another electric injection molding machine of the present invention,
Further, there is provided a thrust bearing that rotatably supports the rotor with respect to the drive unit case and receives the thrust force. The load meter detects a thrust force received by the thrust bearing.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a main part of an electric injection molding machine according to an embodiment of the present invention.
FIG. 5 is an explanatory view of setting a zero point of the load cell according to the embodiment of the present invention, and FIG. 5 is a schematic view of an electric injection molding machine according to the embodiment of the present invention. In FIG. 4, the horizontal axis represents time t.
And the emission power F is plotted on the vertical axis.

In FIG. 5, reference numeral 12 denotes a heating cylinder, and an injection nozzle 12a is provided at the tip (left side in the figure) of the heating cylinder 12. A screw 22 is provided in the heating cylinder 12 so as to be able to advance and retreat and rotate freely. The screw 22 has a screw head 22a at the front end, extends rearward (to the right in the drawing) in the heating cylinder 12, and is connected to the drive unit 31 at the rear end. A spiral flight 23 is formed around the screw 22, and a groove 2 is formed between the flights 23.
6 are formed.

A hopper (not shown) is provided at the rear of the heating cylinder 12 so that pellet resin can be supplied into the heating cylinder 12 from the hopper. Then, at the time of the weighing step, when the driving unit 31 is driven to retract while rotating the screw 22, the pellet-shaped resin in the hopper is
It falls, enters the heating cylinder 12, and is advanced in the groove 26.

A heater (not shown) is provided around the heating cylinder 12 so that the heating cylinder 12 can be heated by the heater and the resin in the groove 26 can be melted. Therefore, when the screw 22 is retracted to a predetermined position while rotating, one shot of the melted resin is accumulated in front of the screw head 22a.

Next, in the injection step, when the driving unit 31 is driven to advance the screw 22 without rotating, the resin stored in front of the screw head 21 is injected from the injection nozzle 12a, It is filled in a cavity space of a mold (not shown). Reference numeral 11 denotes a drive unit case surrounding the drive unit 31, and the drive unit case 11 is fixed to the rear of the heating cylinder 12. The drive unit case 11 includes a front support 14, a center support 15, a rear support 16, and the front support 14.
Front frame 4 connecting the center support 15 with the
1 and a rear frame 42 connecting the center support 15 and the rear support 16 to each other.

A metering motor 44 is provided at the front of the drive unit case 11 and an injection motor 45 is provided at the rear of the drive unit case 11 on the same axis. The metering motor 44 includes a stator 46 fixed to the front frame 41,
And a rotor 47 provided on the inner peripheral side of the stator 46. On the other hand, the injection motor 45
2 and a rotor 49 disposed on the inner circumferential side of the stator 48.

The rotor 47 of the weighing motor 44 is rotatably supported by the drive unit case 11. To this end, a hollow first rotor shaft 56 is fitted and fixed to the rotor 47, and the first rotor shaft 56 is fixed.
The front end of the front support 14 is
The rear end of the center support 15
Respectively supported.

On the other hand, the rotor 49 of the injection motor 45
Is also rotatably supported by the drive unit case 11. Therefore, the hollow second rotor shaft 57 is attached to the rotor 49.
The front end of the second rotor shaft 57 is fixed to the center support 15 by a bearing 53, and the rear end of the second rotor shaft 57 is fixed to a bearing 54 through an annular connection flange 64.
Respectively supported by the rear support 16. The connecting flange 64 is connected to the second rotor shaft 57.
Fixed to the rear end.

By supplying a current having a predetermined frequency to the stator 46 of the metering motor 44, the screw 22 can be rotated backward while rotating. Therefore, the first rotor shaft 5
The first spline nut 62 is fixed to the front end of the first spline shaft 6, the first spline nut 62 and the first spline shaft 63 are spline-connected, and the screw 22 is fixed to the front end of the first spline shaft 63. In this case, the relative movement in the rotation direction is restricted by the first spline nut 62 and the first spline shaft 63, and the relative movement in the axial direction is allowed. The first spline shaft 63 has a length corresponding to the stroke of the screw 22.

Therefore, when the metering motor 44 is driven to rotate the rotor 47, the rotation of the rotor 47 is controlled by the first rotor shaft 56, the first spline nut 6
The rotation is transmitted to the screw 22 via the second and first spline shafts 63 and rotates the screw 22. The resin moves forward while the resin is melted in the groove 26, and the screw 2 is moved by the back pressure generated as the resin advances.
2 is retracted.

At this time, since the first spline nut 62 and the first spline shaft 63 are spline-connected to each other to constitute the rotation transmitting means, the first spline shaft 63 is relatively positioned with respect to the first spline nut 62. Retracted. On the other hand, in the injection motor 45, the stator 4
By supplying a current of a predetermined frequency to the screw 8, the screw 22 can be advanced. For this purpose, a connecting flange 64 is fixed to the rear end of the second rotor shaft 57, and a ball screw shaft 65 is fitted into the inner periphery of the connecting flange 64, and is prevented from rotating by a key 64a. The ball screw shaft 65 is connected to the drive unit case 1.
1 is supported rotatably. That is, the ball screw shaft 65 is connected to the bearing 54 via the connection flange 64.
The thrust bearing 66 supports the rear support 16 with an angular bearing 67 disposed rearward (rightward in FIG. 5) of the thrust bearing 66.

A ball nut 69 is provided inside the second rotor shaft 57 so as to be able to advance and retreat.
9 and the ball screw shaft 65 are screwed together to constitute a movement direction converting means. Therefore, the rotation of the rotor 49 is transmitted to the ball screw shaft 65 via the second rotor shaft 57 and the connection flange 64, and the rotational motion is converted into a linear motion, and the ball nut 69 moves forward and backward. At this time, a second 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 second spline nut 76 fixed to the center support 15. And the second spline shaft 71 are spline-connected. In this case, the relative movement in the rotation direction is restricted by the second spline nut 76 and the second spline shaft 71, and the relative movement in the axial direction is allowed. The second spline shaft 71 has a length corresponding to the stroke of the screw 22.

A bearing box 72 is fixed to the front end of the second spline shaft 71, and a thrust bearing 73 is provided in the bearing box 72 at the front.
A bearing 74 is provided rearward. In this case, the bearing box 72 restricts relative movement in the axial direction and allows relative movement in the rotation direction.
Therefore, the first spline shaft 63 is rotatably supported by the thrust bearing 73 and the bearing 74 with respect to the second spline shaft 71 and the ball nut 69.

Next, the operation of the driving unit 31 of the injection device having the above-described configuration will be described. First, in the injection step, when a current is supplied to the stator 48 of the injection motor 45, the rotor 49 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 connection flange 64. Then, the ball screw shaft 65 is rotated. At this time, since the second spline nut 76 fixed to the center support 15 and the second spline shaft 71 are spline-connected, the ball nut 69 does not rotate. Therefore, a thrust is generated in the ball nut 69, and the ball nut 69 is advanced.

During this time, the metering motor 44 is not driven, and the rotor 47 is stopped. Therefore, the first spline shaft 63 disposed in front of the ball nut 69
Is advanced without rotating, the screw 2
Advance 2 In this manner, the rotational motion generated by the injection motor 45 is converted into a linear motion by the ball screw shaft 65 and the ball nut 69. As a result, the resin stored in front of the screw 22 can be injected from the injection nozzle 12a.

Next, in the measuring step, the measuring motor 4
When the current is supplied to the stator 46 of the fourth spline, the rotor 47 is rotated, and the rotation of the rotor 47 is transmitted to the first spline shaft 63 via the first rotor shaft 56 and the first spline nut 62, and the first spline The shaft 63 is rotated. Then, the rotation of the first spline shaft 63 is transmitted to the screw 22, and the screw 22 is rotated. Along with this, the resin advances in the groove 26 while being melted, and the screw 22 is retracted by the back pressure generated as the resin advances.

At this time, since the first spline nut 62 and the first spline shaft 63 are spline-connected, the first spline shaft 63 is relatively retracted with respect to the first spline nut 62. As described above, since there is no need to use a timing belt to move the screw 22 forward or backward, or to rotate the screw 22, no noise is generated during driving, maintenance and management are easy, and control of speed, position, etc. Accuracy can be improved.

By the way, in the injection step, the screw 22 is pushed by the resin stored in front of the screw head 22a.
Receives a reaction force corresponding to the load. The reaction force is received by the thrust bearing 66 from the ball screw shaft 65 via the connection flange 64. Therefore, the reaction force received by the thrust bearing 66, that is, the thrust force can be detected as the firing force. For this purpose, an annular load cell 78 is fixed to the rear end surface of the rear support 16 by a bolt 79 as shown in FIG.

At the inner peripheral edge of the front end face of the load cell 78,
An annular pressing portion 80 protruding forward is formed, and when the load meter 78 is fixed to the rear end surface of the rear support 16, the pressing portion 80 is pressed against a ring 81, and the ring 81 is pressed. The thrust bearing 66 is supported by way of this, and the thrust bearing 66 is positioned. Therefore, the load meter 78 not only detects the thrust force received by the thrust bearing 66 but also supports the thrust bearing 66 as a support member.

As described above, since the load meter 78 is fixed to the rear end surface of the rear support 16, the work of mounting the load meter 78, the wiring process, and the like are facilitated, and the assemblability is improved. In addition, maintenance and management can be simplified. Further, since not only the firing force can be detected by the load meter 78 but also the thrust bearing 66 can be supported, the ball nut 69
Can be stably supported, and the positional accuracy of the screw 22 can be increased.

Usually, it is necessary to apply a preload to the thrust bearing 66 and the angular bearing 67. To this end, a screw portion 69a is formed at the rear end of the ball nut 69, and the bearing nut 83 is tightened to the screw portion 69a with a predetermined torque, so that the thrust bearing 66 and the angular bearing 6 are formed.
7 is pre-loaded. Therefore, since the preload applied to the thrust bearing 66 can be detected by the load meter 78, it is easy to tighten the bearing nut 83 while monitoring the output of the load meter 78, and to manage the preload amount.

However, in this case, since the thrust bearing 66 and the load meter 78 are in contact with each other, the load meter 78
The preload is also applied, and the zero point shifts. In FIG. 4, the solid line L1 shows the transition of the original emission power F, and the broken line L2
Indicates the transition of the apparent firing power F. As shown in the figure,
An emission power F larger by the amount of deviation ΔF is detected.

Therefore, a control device (not shown) performs calibration in the pressure control during the injection process and resets the zero point. It should be noted that the present invention is not limited to the above-described embodiment, 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.

[0037]

As described above in detail, according to the present invention, in an electric injection molding machine, a heating cylinder and a screw provided in the heating cylinder so as to be able to advance and retreat and rotate freely. A driving unit case connected to the rear of the heating cylinder, a stator fixed to the driving unit case, and an injection motor including a rotor connected to the screw, and disposed on the same axis as the rotor. A movement direction converting means for converting the rotational movement of the rotor into a linear movement, and a movement direction converting means for converting the rotational movement of the rotor into a linear movement. A load cell for detecting the generated thrust force.

In this case, when the injection motor is driven to rotate the rotor, the rotational motion of the rotor is converted into a linear motion by the motion direction converting means. At this time, the thrust force generated on the ball screw shaft is detected by the load meter. Therefore, since the firing force can be detected by the load meter, the positional accuracy of the screw can be increased.

In another electric injection molding machine of the present invention,
Further, there is provided a thrust bearing that rotatably supports the rotor with respect to the drive unit case and receives the thrust force. The load meter detects a thrust force received by the thrust bearing.

In this case, since the load meter pushes the thrust bearing, the load meter can support the thrust bearing. Therefore, the movement direction changing means can be stably supported.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an electric injection molding machine 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 an enlarged view of a main part of an injection device in a conventional electric injection molding machine.

FIG. 4 is an explanatory diagram of setting a zero point of the load cell according to the embodiment of the present invention.

FIG. 5 is a schematic view of an electric injection molding machine according to an embodiment of the present invention.

[Explanation of symbols]

 11 Drive part case 46, 48 Stator 47, 49 Rotor 65 Ball screw shaft 66 Thrust bearing 69 Ball nut 78 Load cell

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/17 B29C 45/46-45/52 B29C 45/57-45/58 B29C 45/76-45 / 77

Claims (2)

(57) [Claims] (A) a heating cylinder; and (b) a movable and retractable inside the heating cylinder.
A screw rotatably disposed; and (c) a drive cable connected to the rear of the heating cylinder.
Graphics and stator fixed in (d) of the drive unit case, and the
Injection motor consisting of a rotor connected to a screw
If, (e) consists of the rotor and the same axis disposed a ball screw shaft and the ball nut on a motion direction converting means for converting rotational motion to linear motion of the rotor, in (f) the drive unit case mounted, motor-driven injection molding machine, characterized in that it comprises a load cell for detecting the thrust force generated on the ball screw shaft due to the conversion by the motion direction converting means. Wherein (a) rotatably supporting said rotor with respect to said drive unit case, which has a thrust bearing for receiving the thrust force, (b) thrust the load meter that is received by the thrust bearing The electric injection molding machine according to claim 1, wherein the electric injection molding machine detects the condition.