JPH10217297A - Pressure detection device and injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect pressure. SOLUTION: When a pressure plate 11 is allowed to advance to the left, a pusher plate 10 allows an injection screw to advance and, therefore, the molten resin in a heating cylinder is injected into the cavity of a mold from an injection nozzle. At this time, a load cell 18 is pressed to the pusher plate 10 to detect pressure. The parallelism of the pusher plate 10 and the pressure plate 11 is collapsed by the bending of a guide rod and, even if the center axis lines of them are mutually shifted, the pressure plate 11 is relatively moved with respect to the pusher plate 10 by floating gaps g1, g2 and, since the pressure plate 11 comes into contact with a connection bolt 20 and the force in the direction crossing the pressure moving direction of the pressure plate 11 is not applied to the connection bolt 20, the pressure detection accuracy of the load cell 18 is not damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pressure detector using a load cell and an injection molding machine equipped with the pressure detector.

[0002]

2. Description of the Related Art As an injection molding machine, as shown in FIG.
A front plate 31 to which a heating cylinder 32 is fixed, and a ball screw shaft 3 rotated by an electric motor (not shown)
A guide rod (tie rod) 38 is erected between the rear plate 35 on which the shaft 6 is pivotally supported, and a pusher plate 40 and a pressure plate 41 are slidably attached to the guide rod 38. The injection screw 33 inserted in the heating cylinder 32 is rotatably mounted in the circumferential direction so as to be able to advance and retreat in the direction, and is rotatable in the circumferential direction. A ball nut 44 screwed to the ball screw shaft 36 is attached to the pressing plate 41. And pusher plate 4
A load cell 48 is provided between the pressure plate 41 and the pressure plate 41 by fixing the load cell 48 to the pusher plate 40 and the pressure plate 41 with bolts 50 and 51, respectively (JP-A-2-160).
No. 23).

In this injection molding machine, a ball screw shaft 36 is rotated by an electric motor, and a ball nut 44 is used to rotate the pressing plate 4.
By pressing 1, the injection screw 33 is advanced through the load cell 48 and the pusher plate 40 to inject the resin into the cavity of the mold. At this time, since the pressure plate 41 functions as a torque receiver and removes the torque of the ball nut 44, the load cell 48 detects the pressure without being affected by the torque.

[0004]

However, in the injection molding machine having the above structure, in order to adjust the center between an injection nozzle provided at the tip of the heating cylinder 32 and a mold (not shown), the injection molding machine shown in FIG. So that the front plate 31 is
At this time, the pressure display of the load cell 48 changes. This phenomenon is not preferable because it means that the display pressure of the load cell 48 is not accurate.

[0005] The present inventors have proposed that the above phenomenon causes the injection nozzle and the center axis of the mold to be inclined, and when the injection nozzle is brought into contact with the mold with a predetermined pressing force in this state, the guide rod 38 is bent. The present inventors have found out that this is caused by the occurrence of displacement of the central axis of the pressure plate 41 and the pusher plate 40 as the pressure receiving plate, and made the present invention based on this new finding. The bending of the guide rod 38 is caused not only when the core of the injection nozzle is adjusted, but also when the core is adjusted.
It is also caused by the load of the front plate 31 and the like.

The present invention relates to a pressure detecting device and an injection molding machine which can always accurately detect pressure without being affected by the center axes of the pressure plate and the pressure receiving plate which may be displaced from each other. The purpose is to provide.

Another object of the present invention is to provide an injection molding machine capable of precisely controlling the pressure of a resin to perform precision molding. Another object of the present invention is to improve an existing one. It is to provide an easy pressure detecting device and an injection molding machine.

[0008]

To achieve at least one of the above objects, a pressure detecting device according to the present invention comprises:
In a pressure detecting device provided with a load cell between a pressure plate and a pressure receiving plate for detecting pressure by being pressed against the pressure plate by the pressure plate, the pressure plate and the pressure receiving plate are moved in the pressing direction of the pressure plate and the pressing direction. The load cell is connected to each other by a connecting means so as to be freely movable relatively in a cross direction crossing the pressure direction, and the load cell is fixed to only one of the pressing plate and the pressure receiving plate by a fixing means.

The contact surface between the other of the pressure plate and the pressure receiving plate and the load cell can be formed in a convex arc shape. Further, the pressure plate and the pressure receiving plate are preferably supported by a guide rod so as to be slidable in the pressure direction of the pressure plate.

The injection molding machine according to the present invention is characterized in that the injection screw is inserted into the heating cylinder so as to be able to advance and retreat in the axial direction and to rotate in the circumferential direction on the pressure receiving plate supported by the guide rod of the pressure detecting device. Is mounted so as to be rotatable in the circumferential direction with the axial direction coinciding with the pressing direction of the pressing plate, and that the pressing plate is connected to injection driving means for moving the pressing plate in the axial direction of the injection screw. .

In the above-described injection molding machine, the injection driving means can be constituted by a screw mechanism for converting a rotary motion into a linear motion, and an electric motor for operating the screw mechanism. Further, the guide rod can be provided between the front plate to which the heating cylinder is fixed and the rear plate provided with the injection driving means.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings. 1 and 2 show an embodiment of the present invention. In the drawings, reference numeral 1 denotes a front plate. A heating cylinder 2 is attached to the front plate 1, and an injection screw 3 is inserted into the heating cylinder 2 so as to be movable in the axial direction and rotatable in the circumferential direction.

Reference numeral 5 denotes a rear plate, on which a pair of ball screw shafts 6 are supported by bearings held by the rear plate 5, and the bearings are pressed by flanges 7. Guide rods (tie rods) 8, 8 are provided between the front plate 1 and the rear plate 5, and integrally connect the plates 1, 5. And
A pusher plate 10 is provided between the front plate 1 and the rear plate 5 so as to be slidably supported by the guide rods 8, 8, and a pressure plate 11 is provided between the rear plate 5 and the pusher plate 10. It is slidably supported on the rods 8, 8. The front plate 1, the rear plate 5, the pusher plate 10, and the pressure plate 11 are parallel to each other.

The injection screw 3 is attached to the pusher plate 10 so as to be rotatable in the circumferential direction, and is rotated by a rotation driving motor (not shown) via a transmission mechanism 13 such as a pulley. As is well known, the injection screw 3 is rotated by an electric motor for rotation drive and melted and kneaded in the heating cylinder 2 while being receded to the right in FIG. In FIG. 1, the weighing resin is moved forward to the left to inject the above-described resin into the cavity of the mold from the injection nozzle.

The pressing plate 11 has a ball nut 1
4 and 14 are attached and screwed to each ball screw shaft 6. The ball screw shaft 6 and the ball nut 14 constitute a screw mechanism for converting a rotary motion into a linear motion, and the ball screw shaft 6 is rotated by a motor 15 such as a servo motor via a transmission mechanism 16 such as a pulley. The pressure plate 11 is moved left and right in FIG. Screw mechanism and electric motor 1
Reference numeral 5 denotes an injection driving unit.

A load cell 18 is detachably fixed to a center portion of the pusher plate 10 on the side of the pressing plate 11 with fixing bolts 19. The load cell 18 detects a pressure, and has a screw hole 18a at a center position. Load cell 1
8, a head (stopper) 20b is provided at one end of the shaft portion 20a.
Connection bolt 20 having a screw 20c formed at the other end, respectively.
Is inserted from the rear plate 5 side into a through hole 11a formed in the center of the pressure plate 11, and a screw 20c is screwed into the screw hole 1.
8a. The connecting bolt 20 has its central axis aligned with the central axis of the injection screw 3, and is perpendicular to the pusher plate 10 and the load cell 18.

Here, the size relationship between the through hole 11a and the connecting bolt 20 will be described. The outer diameter of the shaft portion 20a of the connecting bolt 20 is made smaller than the inner diameter of the through hole 11a.
The outer diameter of the head 20b is made larger than the inner diameter of the through hole 11a, and the length of the shaft portion 20a is made larger than the length of the through hole 11a.

Accordingly, the pressure plate 11 is moved relative to the pusher plate 10 by a difference (gap g1) between the length of the shaft portion 20a of the connecting bolt 20 and the through hole 11a in the direction in which the pressure plate 11 is pressed by the ball screw shaft 6. Relatively free to move,
Further, it is relatively free to move in a cross direction orthogonal to the above-described pressing direction by a difference (gap g2) between the outer diameter of the shaft portion 20a and the inner diameter of the through hole 11a. The contact surfaces 11b and 18b of the pressure plate 11 and the load cell 18 are flat on a surface orthogonal to the center axis of the connecting bolt 20.

Next, the operation of the injection molding machine having the above configuration will be described. When the electric motor 15 is operated to advance the pressure plate 11 by the screw mechanism, the pusher plate 10 is pushed by the pressure plate 11 via the load cell 18 to advance the injection screw 3, so that the molten resin in the heating cylinder 2 is injected. It is injected from the nozzle into the mold cavity. At this time, the load cell 18 is pressed against the pusher plate 10 to detect the pressure.

Even if the pusher plate 10 and the pressing plate 11 are displaced in parallel due to bending of the guide rods 8 and 8 and their center axes are shifted from each other, the pressing plate 11 is moved by the above-mentioned floating gaps g1 and g2. Can move freely relative to the pusher plate 10 and the pressure plate 11
Does not touch the connecting bolt 20 and applies a force to the connecting bolt 20 in a direction intersecting with the pressing movement direction of the pressing plate 11, so that the pressure detection accuracy of the load cell 18 is not impaired.

When the ball screw shaft 6 is rotated in the reverse direction by the electric motor 15, the pressure plate 11 retreats to the right in FIG. 1 and touches the head 20b of the connecting bolt 20, pulling the bolt 20 to the right. The pusher plate 10 and the injection screw 3 retreat.

The load cell 18 detects the back pressure of the pusher plate 10 which is retracted by the injection screw 3 in the resin measuring step. However, at this time, the adverse effect due to the bending of the guide rod 8 and the like is prevented as described above. , Pressure detection accuracy is kept high. During resin injection, the pusher plate 10 serves as a pressure receiving plate for pressure detection. During the measuring process, the pusher plate 10 serves as a pressing plate and the pressing plate 11 serves as a pressure receiving plate.

FIG. 3 shows another embodiment of the present invention. Reference numeral 23 denotes a contact bolt (contact member). The contact bolt 23 has an arc-shaped or hemispherical (hereinafter, an arc shape including both) contact surface 23b that contacts the flat contact surface 11b of the pressing plate 11 at a line or a point, and has a male screw 23a. Screw hole 1
8a and fixed to the load cell 18 by screwing. The contact bolt 23 is detachable from and adjustable on the load cell 18.

The connecting bolt 20 is inserted into the through hole 11a of the pressing plate 11 and is directly screwed to the pusher plate 10. As shown in FIGS. Free play. The length of the shaft portion 20a of the connecting bolt 20 is larger than the interval between the rear surface on the right side of the pusher plate 10 and the rear surface of the pressure plate 11 in a parallel state where the contact surfaces 23b and 11b are in contact with each other. . The pair of connecting bolts 20 are arranged symmetrically with respect to the center axis of the pusher plate 10. The structure of the other parts of the injection molding machine is the same as that of FIG.

In the pressure detecting device shown in FIG. 3, even if the pusher plate 10 and the pressing plate 11 are collimated for some reason, the contact surfaces 11b and 23b contact each other at a line or a point and the load cell 18 Since pressure is applied to the center, pressure detection accuracy is kept higher.

In the present invention, the load cell 18 shown in FIG.
Can be removed from the pusher plate 10 and fixed to the pressure plate 11 by connecting the connecting bolt 20 to the pusher plate 10.
And can be screwed to the pressure plate 11. In the former case, the pusher plate 10 is provided with a contact surface, and in the latter case, the pusher plate 10 is provided with a through hole. Further, the contact surface 23b of the contact bolt 23 can be flattened, and the other contact surface that contacts the contact bolt 23 can be formed in an arc shape. The fixing bolt 19 constitutes a fixing means, and the connecting bolt 20 constitutes a connecting means. However, any of them can be variously changed and is not limited to the one shown in the figure.

Although the illustrated injection molding machine is of an electric type, the present invention can also be applied to a hydraulic injection molding machine using a hydraulic cylinder or a hydraulic motor for various driving sources. Further, the pressure detecting device of the present invention can be applied to other than an injection molding machine.

The pressure detecting device of the present invention can easily improve the conventional pressure detecting device. For example, in the case of the pressure detecting device shown in FIG. It is only necessary to increase the diameter of the through hole 41a. The bolt 50 side may be configured as described above.

[0029]

As described above, the pressure detecting device according to the present invention has a load detecting device in which a load cell is provided between a pressurizing plate and a pressure receiving plate to detect a pressure by being pressed against the pressure receiving plate by the pressurizing plate. In the apparatus, the pressure plate and the pressure receiving plate are connected to each other by a connecting means so as to be relatively freely movable in a pressing direction of the pressure plate and a cross direction intersecting the pressure direction. Since the load cell is fixed to only one of them by the fixing means, the pressure can be accurately detected even if the center axes of the pressure plate and the pressure receiving plate are shifted from each other.

When the contact surface between the other of the pressure plate and the pressure receiving plate and the load cell is formed in a convex arc shape, the pressure can be detected more accurately. The pressure plate and pressure plate are supported by guide rods slidably in the pressure direction of the pressure plate, and even when the pressure plate is moved by the ball nut of the screw mechanism, the torque applied to the pressure plate is removed to reduce the pressure. It is possible to detect correctly.

The injection molding machine according to the present invention is characterized in that the injection screw is inserted into the heating cylinder so as to be able to advance and retreat in the axial direction and to rotate in the circumferential direction on the pressure receiving plate supported by the guide rod of the pressure detecting device. Is rotatably mounted in the circumferential direction with the axial direction coinciding with the pressing direction of the pressing plate.
Since the injection driving means for moving the pressure plate forward and backward in the axial direction of the injection screw is connected, the injection pressure and back pressure of the resin can be accurately controlled to perform precision molding.

If the injection drive means is provided with a screw mechanism for converting a rotary motion into a linear motion and an electric motor for operating the screw mechanism, the injection drive means can be applied to an electric injection molding machine. Further, when the guide rod is constructed between the front plate to which the heating cylinder is fixed and the rear plate provided with the injection driving means, the tie rods of the front plate and the rear plate are also used as the guide rod. Which is reasonable.

[Brief description of the drawings]

FIG. 1 is a partially broken plan view showing one embodiment of an injection molding machine according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a sectional view of a main part of another embodiment.

FIG. 4 is a sectional view of a conventional injection molding machine.

FIG. 5 is a diagram illustrating a work of adjusting a core of an injection nozzle.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Front plate 2 Heating cylinder 3 Injection screw 5 Rear plate 6 Ball screw shaft (screw mechanism) 8 Guide rod (tie rod) 10 Pusher plate (pressure receiving plate) 11 Pressure plate 11b Contact surface 14 Ball nut (screw mechanism) 15 Motor 18 Load cell 18b Contact surface 19 Fixing bolt (fixing means) 20 Connection bolt (Connection means) 23 Contact bolt 23b Contact surface

Claims (6)

[Claims] In a pressure detecting device provided with a load cell between a pressure plate and a pressure receiving plate for detecting pressure by being pressed against the pressure plate by the pressure plate, the pressure plate and the pressure receiving plate are connected to each other by a pressure plate. It is connected by a connecting means so as to be relatively free to move in a pressure direction and an intersecting direction intersecting the pressing direction, and that the load cell is fixed to only one of the pressing plate and the pressure receiving plate by fixing means. Characteristic pressure detecting device. 2. The contact surface between the other of the pressure plate and the pressure receiving plate and the load cell is formed in a convex arc shape.
The pressure detection device as described in the above. 3. The pressure detecting device according to claim 1, wherein the pressure plate and the pressure receiving plate are supported by a guide rod so as to be slidable in a pressure direction of the pressure plate. 4. An injection screw inserted in the heating cylinder so as to be able to advance and retreat in the axial direction and to be rotatable in the circumferential direction on the pressure receiving plate according to claim 3, so that the axial direction matches the pressing direction of the pressing plate. An injection molding machine, which is rotatably mounted in a direction, and is connected to an injection driving means for moving the pressure plate in the axial direction of the injection screw to the pressure plate. 5. The injection molding machine according to claim 4, wherein said injection driving means includes a screw mechanism for converting a rotary motion into a linear motion, and an electric motor for operating said screw mechanism. 6. The injection molding machine according to claim 4, wherein the guide rod is provided between a front plate to which the heating cylinder is fixed and a rear plate provided with injection driving means. .