JP3421763B2 - Pressure detection device and 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 a pressure detecting device using a load cell and an injection molding machine equipped with the pressure detecting device.

[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 installed between a rear plate 35 on which 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 into the heating cylinder 32 is mounted rotatably in the circumferential direction so as to be movable back and forth in the direction and rotatable in the circumferential direction, and the pressure plate 41 is attached to the ball nut 44 screwed to the ball screw shaft 36. Attached, pusher plate 4 again
It is known that the load cell 48 is provided between the 0 and the pressure plate 41 by being fixed 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, the ball screw shaft 36 is rotated by an electric motor and the pressure plate 4 is rotated by a ball nut 44.
By pushing 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-mentioned structure, the core of the injection nozzle provided at the tip of the heating cylinder 32 and the mold (not shown) is adjusted as shown in FIG. The front plate 31 and the jack bolt 6
Although it is lifted at 0 for adjustment, a phenomenon in which the pressure display of the load cell 48 changes occurs at this time. This phenomenon is not preferable because it means that the display pressure of the load cell 48 is not accurate.

According to the proposer of the present invention, the above phenomenon causes the center axes of the injection nozzle and 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 bends. The present invention has been made based on this new finding. The present invention is based on this new finding and has found out that it is caused by the deviation of the central axis of the pressure plate 41 and the pusher plate 40 as the pressure receiving plate. The deflection of the guide rod 38 is not limited to when the core of the injection nozzle is adjusted,
It is also generated by the load of the front plate 31 and the like.

According to the present invention, there is provided a pressure detecting device and an injection molding machine which can always detect pressure accurately without being affected by the center axes of the pressure plate and the pressure receiving plate which are deviated 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 resin to perform precision molding, and another object of the present invention is to improve the existing one. An object is to provide an easy pressure detection device and an injection molding machine.

[0008]

In order to achieve at least one of the above objects, a pressure detecting device according to the present invention comprises:
Between the pressure plate and the pressure receiving plate, that the pressure sensing device a load cell is provided for detecting the pressure is pressed against the pressure receiving plate by a pressure plate, the pressure plate and the pressure receiving plate, they
Connecting hands attached to one of them and the other of them
The pressure plate is connected to each other by the connecting means so that only the gap between the pressure plate and the pressure plate is relatively movable in the pressure direction of the pressure plate and the direction intersecting the pressure direction. The load cell is fixed to only one of the pressure 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. The pressure plate and the pressure receiving plate may be supported by the guide rod so as to be slidable in the pressure direction of the pressure plate.

Further, in the injection molding machine according to the present invention, an injection screw is inserted into a heating cylinder movably in the axial direction and rotatably in the circumferential direction on a pressure receiving plate supported by a guide rod of the pressure detecting device. Is attached rotatably in the circumferential direction with the axial direction aligned with the pressing direction of the pressing plate, and the pressing plate is connected to injection driving means for advancing and retracting the pressing plate in the axial direction of the injection screw. .

In the above-mentioned injection molding machine, the injection driving means can be composed of 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 installed between the front plate to which the heating cylinder is fixed and the rear plate to which the injection driving means is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described based on examples with reference to the drawings. 1 and 2 show an embodiment of the present invention, in which reference numeral 1 is 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 rotatably supported by bearings held by the rear plate 5, and the bearings are held by a flange 7. Guide rods (tie rods) 8 are installed between the front plate 1 and the rear plate 5 to integrally connect the plates 1 and 5. And
A pusher plate 10 is slidably supported by the guide rods 8 and 8 between the front plate 1 and the rear plate 5, and a pressure plate 11 is guided 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 rotatably mounted on the pusher plate 10 in the circumferential direction, and is rotated by a rotation driving electric motor (not shown) via a transmission mechanism 13 such as a pulley. As is well known, the injection screw 3 is rotated by a rotation driving electric motor and moves backward in FIG. 1 to melt and knead the resin in the heating cylinder 2 to measure the resin, and by the pusher plate 10 in a rotation stopped state. It is moved forward to the left in FIG. 1 and the above-mentioned measuring resin is injected from the injection nozzle into the cavity of the mold.

The pressure 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 that converts a rotational movement into a linear movement. An electric motor 15 such as a servomotor rotates the ball screw shaft 6 through a transmission mechanism 16 such as a pulley. The pressure plate 11 is moved back and forth in FIG. Screw mechanism and electric motor 1
Reference numeral 5 constitutes injection driving means.

A load cell 18 is detachably fixed to a central portion of the pusher plate 10 on the pressure plate 11 side by a fixing bolt 19. The load cell 18 detects pressure, and has a screw hole 18a at the center position. Load cell 1
8, a head (stopper) 20b is provided at one end of the shaft portion 20a,
Connecting bolts 20 each having a screw 20c formed at the other end
Is inserted from the rear plate 5 side into a through hole 11a formed in the central portion of the pressure plate 11, and the screw 20c is screwed into the screw hole 1
It is attached by screwing to 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 larger than the inner diameter of the through hole 11a, and the length of the shaft portion 20a is larger than the length of the through hole 11a.

Therefore, the pressure plate 11 is moved relative to the pusher plate 10 by the difference in length (gap g1) between the shaft portion 20a of the connecting bolt 20 and the through hole 11a in the pressing direction of the pressure plate 11 by the ball screw shaft 6. It is relatively free to move,
Further, only the difference (gap g2) between the outer diameter of the shaft portion 20a and the inner diameter of the through hole 11a is relatively free to move in the intersecting direction orthogonal to the pressing direction. The contact surfaces 11b and 18b of the pressure plate 11 and the load cell 18 are made flat on a surface orthogonal to the central axis of the connecting bolt 20.

Next, the operation of the injection molding machine having the above structure will be described. When the electric motor 15 is operated to move the pressure plate 11 forward by the screw mechanism, the pusher plate 10 is pushed by the pressure plate 11 via the load cell 18 to move the injection screw 3 forward, 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 pressure plate 11 are broken in parallel due to the bending of the guide rods 8 and the center axes of the pusher plate 10 and the pressure plate 11 are deviated from each other, the pressure plates 11 are moved by the above-mentioned floating gaps g1 and g2. Is movable relative to the pusher plate 10, and the pressure plate 11
Does not touch the connecting bolt 20 to apply a force to the connecting bolt 20 in a direction intersecting the pressing movement direction of the pressure 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 to pull the bolt 20 to the right. The pusher plate 10 and the injection screw 3 retract.

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, but even at this time, the adverse effect due to the bending of the guide rod 8 and the like is prevented as in the above. , The pressure detection accuracy is kept high. It should be noted that the pusher plate 10 serves as a pressure receiving plate for pressure detection during resin injection, and the pusher plate 10 serves as a pressure plate and the pressure plate 11 serves as a pressure receiving plate during the weighing process.

FIG. 3 shows another embodiment of the present invention, in which reference numeral 23 is a contact bolt (contact member). The contact bolt 23 has an arc-shaped or hemispherical contact surface 23b (hereinafter, both arc-shaped including both) that contacts the flat contact surface 11b of the pressure plate 11 at a line or a point, and has a male screw 23a. Screw hole 1
It is fixed to the load cell 18 by being screwed onto 8a. The contact bolt 23 is attachable to and detachable from the load cell 18 and adjustable.

Further, the connecting bolt 20 is inserted into the through hole 11a of the pressure plate 11 and directly screwed to the pusher plate 10, so that the pressure plate 11 is opposed to the pusher plate 10 in the same manner as in FIGS. 1 and 2. Free movement. The length of the shaft portion 20a of the connecting bolt 20 is larger than the distance 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 in which 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 central 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 of FIG. 3, even if the pusher plate 10 and the pressure plate 11 are not parallel to each other for some reason, the contact surfaces 11b and 23b contact each other at a line or a point so that the load cell 18 is always in contact. Since the pressure is applied to the center, the pressure detection accuracy is kept higher.

In the present invention, the load cell 18 of FIG.
It is also possible to remove the connecting bolt 20 from the pusher plate 10 and fix it to the pressure plate 11.
It can also be detached from and screwed to the pressure plate 11. It goes without saying that the contact surface is provided on the pusher plate 10 in the former case, and the through hole is provided in the pusher plate 10 in the latter case. Further, the contact surface 23b of the contact bolt 23 may be flattened, and the other contact surface contacting with this may be arcuate. Although the fixing bolt 19 constitutes a fixing means and the connecting bolt 20 constitutes a connecting means, any of them can be variously modified and the invention is not limited to the one shown in the drawing.

Although the injection molding machine shown in the figure is of an electric type, the present invention can also be applied to a hydraulic injection molding machine using hydraulic cylinders and hydraulic motors for various drive sources. Further, the pressure detection device of the present invention can be applied to other than the injection molding machine.

In the pressure detecting device of the present invention, it is easy to improve the conventional pressure detecting device. For example, in the case of the pressure detecting device of FIG. 4, the bolt 51 is replaced with a long shaft portion and the pressure plate 41 is used. 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, in the pressure detecting device according to the present invention, the pressure detecting device is provided with the load cell between the pressure plate and the pressure receiving plate, which is pressed against the pressure receiving plate by the pressure plate to detect the pressure. In the device, the pressure plate and the pressure receiving plate are attached to one of them and the other of them.
By a gap between the vignetting the coupling means, it freely relative floating in a direction crossing the pressure direction and pressurizing direction of the pressure plate
As described above, the load cells are connected to each other by the connecting means, and the load cell is fixed to only one of the pressure plate and the pressure receiving plate by the fixing means. Even if there is a deviation from each other, the pressure can be accurately detected.

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. Even if the pressure plate and pressure receiving plate are slidably supported by the guide rod in the pressure direction of the pressure plate and the pressure plate is moved by the ball nut of the screw mechanism, the pressure applied to the pressure plate is removed by removing the torque applied It becomes possible to detect correctly.

Further, in the injection molding machine according to the present invention, an injection screw is inserted into a heating cylinder movably in the axial direction and rotatably in the circumferential direction on a pressure receiving plate supported by a guide rod of the pressure detecting device. Is attached rotatably in the circumferential direction with the axial direction aligned with the pressure direction of the pressure plate, and on the pressure 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 the back pressure of the resin can be accurately controlled to perform precision molding.

If the injection driving 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, it can be applied to an electric injection molding machine. Further, when the guide rod is constructed so as to be installed between the front plate to which the heating cylinder is fixed and the rear plate provided with the injection drive means, the guide rod may serve as the tie rod of the front plate and the rear plate. And is rational.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view showing an 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 portion of another embodiment.

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

FIG. 5 is a diagram for explaining the core adjustment work of the injection nozzle.

[Explanation 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 Plate) 11 Pressure Plate 11b Abutment Surface 14 Ball Nut (Screw Mechanism) 15 Electric Motor 18 Load cell 18b Contact surface 19 Fixing bolt (fixing means) 20 Connecting bolt (connecting means) 23 Contact bolt 23b Contact surface

Claims (6)

(57) [Claims] Between 1. A pressing plate and the pressure receiving plate, that the pressure sensing device a load cell is provided for detecting the pressure is pressed against the pressure receiving plate by a pressure plate, said pressure plate and the pressure receiving plate, of which Mounted on one and the other of them
By a gap between the vignetting the coupling means, it freely relative floating in a direction crossing the pressure direction and pressurizing direction of the pressure plate
As described above, the pressure detecting device is connected to each other by the connecting means, and the load cell is fixed to only one of the pressure plate and the pressure receiving plate by the fixing means. 2. The contact surface between the other of the pressure plate and the pressure receiving plate and the load cell has a convex arc shape.
The pressure detection device described. 3. The pressure detecting device according to claim 1, wherein the pressure plate and the pressure receiving plate are slidably supported by the guide rod in the pressure direction of the pressure plate. 4. An injection screw, which is inserted into the pressure receiving plate according to claim 3 so as to be capable of advancing and retreating in the axial direction and rotatable in the circumferential direction, has its axial direction aligned with the pressing direction of the pressing plate. An injection molding machine, which is mounted rotatably in a direction, and to which a pressure plate is connected with injection drive means for moving the pressure plate forward and backward in the axial direction of the injection screw. 5. The injection molding machine according to claim 4, wherein the injection driving means includes a screw mechanism that converts a rotational movement into a linear movement, and an electric motor that operates the screw mechanism. 6. The injection molding machine according to claim 4, wherein the guide rod is installed between a front plate to which the heating cylinder is fixed and a rear plate provided with injection driving means. .