JP2000246773A - Resin pressure detector for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a detecting accuracy of a resin pressure. SOLUTION: A strain measuring sensor 25 measures a strain of a tie bar 3 in an axial direction, and is formed in a semicircular shape, and attached to an outer peripheral surface of a uniform section sufficiently separated from threaded parts 3a, 3b of both ends of the bar 3 by a bolt or the like around the bar 3. A controller 28 calculates a resin pressure based on an output signal of the sensor 25 in injecting and metering steps. Thus, the resin pressure can be accurately detected without influence of the clamping degree of a mounting nut 7 engaged with the shaft member such as a tie bar or the like to clamp a rear plate 4 at a shaft member or a heat of a heating cylinder 1. Since it is not necessary to drill the shaft member without lowering strength of the shaft member, the resin pressure detector having excellent durability can be inexpensively manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting resin pressure during injection and metering of an injection molding machine.

[0002]

2. Description of the Related Art As a resin pressure detecting device of an injection molding machine, the one shown in FIGS. 5 to 8 is known. The resin pressure detecting device of these injection molding machines will be described. The resin pressure detecting device of the injection molding machine shown in FIG. 5 is composed of a fixed plate 52 provided with a heating cylinder 51 and a pusher plate 59 provided rotatably with an injection screw 58. Are attached via a tie bar 53, and a pusher plate 59 and a rear plate 54 fixed to a rear end of the tie bar 53 by a nut 57.
Then, an axial tensile load is applied to the tie bar 53, and the pusher plate 52 is moved together with the injection screw 58 into the tie bar 53.
In the injection molding machine provided with an injection driving device 73 for moving the molten resin in the heating cylinder 51 forward into the molding cavity of the mold (not shown) by moving the resin along the rear plate 5
4 and a nut 57, a load cell 75 is provided.
To detect the resin pressure (Japanese Patent No. 2667521). The injection driving device 73
Is the ball nut 6 fixed to the pusher plate 59
And a rear plate 5 screwed into the ball nut 63.
4 comprises a ball screw shaft 66 rotatably attached to the motor 4 and a motor 68 (FIG. 8) for rotating the ball screw shaft 66.

The resin pressure detecting device of the injection molding machine shown in FIG.
5 shows another example of the resin pressure detecting device of FIG.
A load cell 75 composed of a strain gauge is provided on the end face of the thread portion of No. 3.
The structure is such that a bolt 80 in which a is embedded is embedded and fixed. The resin pressure detecting device of the injection molding machine of FIG. 7 is another example of the resin pressure detecting device of FIG. 5, and has a structure in which a load meter 75b made of a piezoelectric element is embedded in the end surface of the screw portion of the tie bar 53. .

The resin pressure detecting device of the injection molding machine shown in FIG.
The heating cylinder 51 is slidably attached to the fixing plate 52 back and forth and fixed via a load cell 85, and the resin pressure and the nozzle touch pressure are detected by the load cell 85 (Japanese Patent No. 2649111). In addition,
The same members as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

[0005]

The resin pressure detecting devices shown in FIGS. 5 to 8 have the following problems. (Resin pressure detecting device in FIG. 5) Even when no resin pressure is applied when the nut 57 for tightening the tie bar 53 is tightened, a compressive load is already applied to the load meter 75.
It is not possible to distinguish between the resin pressure and the tightening force of the nut 57. Even if the load at the time when the nut 57 is tightened is reset to 0, the tightening force of the nut 57 may change during use, and accurate measurement cannot be performed. In addition, since the load meter 75 needs to have a large capacity to which the tightening force of the nut 57 is applied, measurement cannot be performed with fine precision.

[0006] Both of the resin pressure detectors shown in FIGS. 6 and 7 need to be provided with a screw hole or a measurement hole at the rear end of the tie bar 53. The effective area must be reduced. Further, since the screw hole and the measurement hole cannot be made too deep in processing, the tensile load is measured in the vicinity of the end face of the tie bar 53. However, the shaft shape of this portion is not uniform because a step or a screw is provided on the outer periphery. Therefore, it is difficult to create a conversion formula for converting a measured value into a load.

(Resin Pressure Detector in FIG. 8) Since the load cell 85 is in contact with the heating cylinder 51 and heat is transmitted to the load cell 85, accurate measurement cannot be performed due to the influence of heat. Further, it is necessary to use a load cell 85 of a special shape having a hole in the center, which increases the cost. This point is equivalent to the load cell 75 in FIG.
The same applies to

[0008] The present invention has been made in view of the above,
An object of the present invention is to provide a resin pressure detecting device of an injection molding machine that can accurately detect a resin pressure. Another object of the present invention is to provide a resin pressure detecting device for an injection molding machine, which does not need to reduce the strength of shaft members such as tie bars and ball screw shafts. Another object of the present invention is to provide a resin pressure detecting device for an injection molding machine which is inexpensive.

[0009]

In order to achieve at least one of the above-mentioned objects, according to the first aspect of the present invention, a pusher plate having an injection screw rotatably mounted on a fixed plate having a heating cylinder is provided. Attached via a shaft member, an axial tensile load is applied to the shaft member to the pusher plate, and the pusher plate advances with the injection screw to inject the molten resin in the heating cylinder into the mold cavity of the mold. In an injection molding machine provided with an injection drive device to be driven, a distortion measuring sensor is attached to the outer peripheral surface of the shaft member.

In this means, the injection driving device is operated to advance the injection screw together with the pusher plate,
In the injection step of injecting the molten resin in the heating cylinder, a tensile load is applied to the shaft member by a reaction force that advances the injection screw. The strain measurement sensor detects the strain of the shaft member due to the tensile load, that is, the resin pressure. Also, in the measuring step of rotating the injection screw and retreating while melting the resin, the back pressure applies a tensile load to the shaft member in the same manner as described above, and the strain measurement sensor detects distortion of the shaft member due to the tensile load. . The strain measurement sensor is preferably attached to a uniform cross-section where a screw or the like sufficiently separated from both ends of the shaft member is not formed.

In the resin pressure detecting device for an injection molding machine according to the present invention, the strain measuring sensor has a semicircular shape and can be attached to the shaft member with a bolt or a magnet.
Claim 3). With this configuration, attachment and detachment of the strain measurement sensor to and from the shaft member are simple, and maintenance is easy.

Further, in the resin pressure detecting device for an injection molding machine according to the present invention, the strain measuring sensor can be attached to the shaft member with an adhesive. With this configuration, the strain measurement sensor can be firmly and easily integrated with the shaft member.

In the resin pressure detecting device for an injection molding machine according to any one of claims 1 to 4, the shaft member is integrally connected to the fixed plate and the rear plate, and the pusher plate is movable back and forth. The tie bar may be supported and provided (claim 5), and the shaft member may be a ball screw shaft screwed into a rotatable ball nut and spanned between the fixed plate and the pusher plate. (Claim 6). In any case, a tie bar or a ball screw shaft is effectively used. The latter ball screw shaft is usually configured such that the rear end is screwed into a ball nut rotatably mounted on the pusher plate and the front end is fixed to the fixed plate, but is rotatably mounted on the fixed plate. In some cases, the front end is screwed into the ball nut, and the rear end is fixed to the pusher plate.

[0014]

Embodiments of the present invention will be described with reference to the accompanying drawings. 1 and 2 show an embodiment of a resin pressure detecting device for an injection molding machine according to the present invention, and reference numeral 1 denotes a heating cylinder. The heating cylinder 1 is horizontally fixed to the center of a fixed plate (front plate) 2 so as to protrude forward (same and leftward).

A rear plate 4 is attached to the fixed plate 2 by a pair of left and right tie bars (shaft members) 3. Each tie bar 3 is attached to the fixed plate 2 and the rear plate 4 in parallel with each other by tightening attachment nuts 6 and 7 screwed to the screw portions 3a and 3b at both ends, and integrally connects them. A pusher plate 9 having an injection screw 8 is supported by the tie bars 3 and 3 so as to be movable back and forth. The injection screw 8 is attached to the pusher plate 9 by a bearing 10 with its tip inserted into the heating cylinder 1, and is rotated in the circumferential direction by a screw servomotor (not shown). .

The rear plate 4 has a pair of left and right hollow shafts 1.
1 are rotatably mounted by bearings 12 and each hollow shaft 11
A ball nut 13 is fixed to a front end portion of the motor, and a driven pulley 14 is fixed to a rear end portion of the motor. The pusher plate 9 has a pair of left and right ball screw shafts 16.
However, the rear part is screwed into the ball nut 13 and fixed respectively. Note that the outer diameter of the ball screw shaft 16 is smaller than the inner diameter of the hollow shaft 11.

An injection servomotor 18 is fixed to the rear plate 4 by a bracket 19. A drive pulley 20 is attached to the output shaft of the injection servomotor 18, and an endless timing belt 21 is wound around the drive pulley 20 and the driven pulleys 14, 14.
In this configuration, when the injection servomotor 18 is operated, the ball nuts 13 rotate, and the ball screw shafts 16 move according to the rotation direction to move the pusher plate 9 forward or backward.

As will be understood from the above description, the ball nut 13 and the ball screw shaft 16 constitute a screw mechanism for changing a rotary motion into a linear motion, and the screw mechanism, the injection servomotor 18, the timing belt 21 and the like. Constitutes an injection driving device 23 that advances the injection screw 8 together with the pusher plate 9 to inject the molten resin in the heating cylinder 1 into the molding cavity of the mold.

Reference numeral 25 denotes a strain measurement sensor (combination cylindrical type axial sensor). The strain measurement sensor 25 measures the axial strain of the tie bar 3 and has a semicircular shape. Surrounded by bolts 26 and nuts 27. A control device 28 is connected to the strain measurement sensor 25 via a wiring 29.

The controller 28 calculates the following equation (1) based on the output signal of the strain measuring sensor 25 to determine the resin pressure P in the injection step and the metering step. P = nAεE / S (1) where A: cross-sectional area of tie bar 3 ε: axial strain of tie bar 3 E: Young's modulus of tie bar 3 S: cross-sectional area of injection screw 8 n: number of tie bars 3 (FIG. In the case of 1, n = 2)

Next, the operation of the resin pressure detecting device of the injection molding machine having the above configuration will be described. In the weighing process,
As is well known, while rotating the injection screw 8 to melt the resin in the heating cylinder 1, the injection screw 8 is gradually retracted at a predetermined back pressure, and the molten resin is measured at the front end of the injection screw 8. At this time, as the injection screw 8 is retracted, the rear plate 4 is pushed rearward via the ball screw shaft 16 and the like, so that the tie bars 3, 3 receive a tensile load. The strain measurement sensor 25 measures the strain of the tie bar 3 caused by the tensile load and outputs the measured strain to the control device 28. The control device 28 calculates the resin pressure based on the output signal.

In the injection step, as is well known, the injection screw 8 is moved forward by the operation of the injection driving device 23. At this time, the tie bar 3 is driven by the reaction force that advances the ball screw shaft 16 by the rotation of the ball nut 13.
Is subjected to a tensile load. Also in this case, the strain measurement sensor 25 measures the strain of the tie bar 3, and the control device 28 calculates the resin pressure based on the output signal of the strain measurement sensor 25.

As described above, the present resin pressure detecting device detects the resin pressure from the distortion of the outer peripheral surface of the uniform cross section sufficiently separated from both ends of the tie bar 3, and therefore differs from the conventional detecting device. It is not necessary to form a hole in the end face of the tie bar 3, and it is possible to easily and accurately detect the resin pressure of the injection molding machine without affecting the measured value by the tightening of the mounting nuts 6 and 7 at both ends. Can be. Further, the strength of the tie bar 3 does not need to be reduced by the drilling.

FIG. 3 shows a second embodiment of the present invention.
In the case of this device, the strain measurement sensor 25 is attached to the tie bar 3 by the magnet 31,
5 is very easy to attach and detach. Therefore, the strain measuring sensor 25 of this mounting type can be temporarily used as a second resin pressure sensor for checking an existing resin pressure detecting device. The other structure of the resin pressure detecting device, that is, the structure of the injection device is the same as the detecting device of FIG.

FIG. 4 shows a third embodiment of the present invention.
In the case of this device, the strain measurement sensor 25 is attached to the outer peripheral surface of the tie bar 3 with the adhesive 32, and the strain of the tie bar 3 in the axial direction can be measured. The other structure of this detecting device is the same as that of the device shown in FIG.

The strain measuring sensor 25 shown in FIGS. 2 and 3 may have a structure in which a main body of the strain measuring sensor is integrally attached to an inner peripheral surface of a semicircular mounting member. The structure of the injection device of the injection molding machine to which the present invention is applied is not limited to the injection device shown in FIG. 1, and is arbitrary. For example, a ball screw shaft (shaft member) is screwed into a rotatable ball nut. The present invention can also be applied to an injection device installed between the fixed plate and the pusher plate 9. The injection device has a ball screw shaft fixed to the fixed plate 2 and a ball nut rotatably mounted on the pusher plate 9, and a ball screw shaft fixed to the pusher plate 9 and the ball nut fixed to the fixed plate 2. 2 is rotatably mounted, but both can be implemented.

In the resin pressure detecting device shown in FIG. 1, the strain measuring sensor 25 is attached to only one tie bar 3, but as shown by a two-dot chain line in FIG. Each of the measurement sensors 25 can be attached. The resin pressure in this case is two strain measurement sensors 2
Needless to say, the sum of the resin pressure of No. 5 is obtained. Thus, the total number of the shaft members 3 and the number of the shaft members 3 to which the strain measurement sensors 25 are attached are both arbitrary.

[0028]

As described above, according to the first aspect of the present invention, the tightening condition of the mounting nut screwed to the shaft member such as the tie bar and fixing the rear plate to the shaft member, and the heating cylinder The resin pressure can be accurately detected without being affected by heat. Further, since it is not necessary to form a hole in the shaft member and the strength of the shaft member does not need to be reduced, a resin pressure detecting device having excellent durability can be manufactured at low cost.

In the resin pressure detecting device for an injection molding machine according to the present invention, when the strain measuring sensor is formed in a semicircular shape and is attached to the shaft member with a bolt or a magnet, the mounting and dismounting of the strain measuring sensor with respect to the shaft member. Simplifies assembly and saves time for assembly and maintenance. In addition, when the strain measurement sensor is configured to be attached to the shaft member with an adhesive, attachment of the strain measurement sensor is further facilitated,
In addition, the strain measurement sensor can be firmly integrated with the shaft member to improve the detection accuracy.

[Brief description of the drawings]

FIG. 1 is a partially broken plan view showing a first embodiment of a resin pressure detecting device for an injection molding machine according to the present invention.

FIG. 2 is a cross-sectional view taken along a line (II-II) in FIG.

FIG. 3 is a sectional view of a main part showing a second embodiment of the present invention.

FIG. 4 is a sectional view of a main part showing a third embodiment of the present invention.

FIG. 5 is a partially broken plan view of a conventional resin pressure detecting device of an injection molding machine.

FIG. 6 is a sectional view showing a modified example of the resin pressure detecting device of FIG.

FIG. 7 is a sectional view showing another modified example of the resin pressure detecting device of FIG.

FIG. 8 is a diagram of another conventional resin pressure detecting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Fixing plate 3 Tie bar (shaft member) 4 Rear plate 8 Injection screw 9 Pusher plate 18 Injection servomotor 23 Injection drive 25 Strain measurement sensor 31 Magnet 32 Adhesive

Claims (6)

[Claims] 1. A pusher plate rotatably provided with an injection screw is mounted on a fixed plate provided with a heating cylinder via a shaft member, and an axial tensile load is applied to the pusher plate on the shaft member. The injection molding machine provided with an injection drive device for advancing the pusher plate together with the injection screw and injecting the molten resin in the heating cylinder into the molding cavity of the mold, wherein a distortion measuring sensor is provided on the outer peripheral surface of the shaft member. A resin pressure detecting device for an injection molding machine, wherein a resin is attached. 2. The strain measuring sensor according to claim 1, wherein the strain measuring sensor has a semicircular shape and is attached to the shaft member with bolts.
A resin pressure detecting device for an injection molding machine as described in the above. 3. The resin pressure detecting device for an injection molding machine according to claim 1, wherein the strain measuring sensor has a semicircular shape and is attached to the shaft member with a magnet. 4. The resin pressure detecting device for an injection molding machine according to claim 1, wherein the strain measuring sensor is attached to the shaft member with an adhesive. 5. The shaft member according to claim 1, wherein the shaft member is a tie bar provided integrally with the fixed plate and the rear plate, and supporting the pusher plate movably back and forth. A resin pressure detecting device for an injection molding machine according to any one of the preceding claims. 6. The ball screw shaft according to claim 1, wherein the shaft member is screwed to a rotatable ball nut and is provided between the fixed plate and the pusher plate.
5. The resin pressure detecting device for an injection molding machine according to any one of items 4 to 4.