JP2002067118A - Pressure detector of molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce detection error of a pressure to be applied to a member to be driven forward or backward such as a screw or the like as much as possible. SOLUTION: In a molding machine having a load cell unit mounted at the member to be forward or backward driven to detect a pressure to be applied to the member to be driven at the member to be driven and forward or backward driven by a drive source, an amplifier for amplifying an output of a stress detecting element, an A-D converter for converting an analog output signal of the amplifier into a digital signal and a serial communication means for sending an output signal from the converter as a serial data signal are arranged so as to be integral with a holder of a stress detecting element in the cell unit, and the signal from the communication means is sent to a controller provided in the molding machine.

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 in a molding machine such as an injection molding machine or a die casting machine, and more particularly to a driven member driven forward and backward by a driving source, for example, a screw of an injection molding machine. The present invention relates to a pressure detection device for detecting an applied pressure.

[0002]

2. Description of the Related Art An electric machine using an electric servomotor as a drive source of an injection molding machine or the like has recently become widespread.
By the way, in the injection molding machine of the in-line screw type, detecting the pressure applied to the screw,
It is essential for controlling the injection pressure during the injection stroke and the back pressure during the metering stroke. Therefore, in the electric in-line screw injection molding machine, pressure (load) is detected between the screw holder that holds the base end of the screw and the linear moving body of the ball screw mechanism that converts the rotational motion into linear motion. It is a common practice to sandwich a load cell unit for use and to detect the pressure applied to the screw by the load cell unit. The load cell unit includes a strain gauge as a stress detection element, a cylindrical detection element holder having the strain gauge adhered to an inner peripheral surface thereof, and the like, and the strain cell is disposed integrally with the detection element holder. And an amplifier for amplifying the output of the gauge.

FIG. 4 is a diagram showing a conventional load cell unit and a control device of an injection molding machine to which the output of the load cell unit is supplied. In FIG.
1 is a load cell unit arranged at the above-mentioned position, 5
2 is a strain gauge for detecting pressure (load), 53 is an amplifier for amplifying the output of the strain gauge, 54 is a control device disposed in the main housing below the injection molding machine, and 55 is a load cell unit 51 and a control device. 54, an amplifier for amplifying the output from the load cell unit 51, and 57 an amplifier 5
An A / D converter 58 converts an analog signal output from 6 into a digital signal, and 58 is a CPU that controls the overall control device and stores the output of the A / D converter 57 in a RAM (not shown).

In the configuration shown in FIG. 4, a detection output of a strain gauge 52 is amplified by an amplifier 53,
The digital signal is sent to an amplifier 56 through an A / D converter 57 and converted into a digital signal in an A / D converter 57. The signal converted into a digital signal is appropriately converted as needed, and is used as injection pressure control and metering control as detected pressure data (actually measured pressure data).

[0005]

In the prior art shown in FIG. 4, the load cell unit 51 and the control device 54 are connected by a cable 55, and the GND level, which is the reference point of the electric signal, is set to 51, At first glance, it seems to be the same level at 54, but actually, due to the impedance and noise of the cable 55, a potential difference of milliV level is generated at the GND at the points A and B in FIG. In this case, the potential difference fluctuates. For this reason, an error occurs in the pressure signal sent to the control device 54, and the control of the resin pressure on the screw tip side during the weighing operation detects a very small pressure. In the production of molded articles, etc., it becomes a hindrance factor for improving the quality of molded articles.

[0006] The present invention has been made in view of the above points,
An object of the present invention is to reduce a detection error of a pressure applied to a driven member driven forward and backward such as a screw as much as possible.

[0007]

In order to achieve the above object, the present invention provides a load cell unit for detecting a pressure applied to a driven member driven forward and backward by a driving source. In the mounted molding machine,
An amplifier for amplifying the output of the stress detection element so as to be integrated with a holder of the stress detection element in the load cell unit, an A / D converter for converting an analog output signal of the amplifier into a digital signal, and an A / D converter Serial communication means for transmitting an output signal from the converter as a serial data signal is provided, and the serial data signal from the serial communication means is transmitted to a control device provided in the molding machine.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a main configuration of an injection system mechanism in an inline screw type injection molding machine according to one embodiment of the present invention, and FIG. 2 is a side view of a load cell unit in FIG.

In FIG. 1, 1 is a holding block, and 2 is
A rotating body rotatably held by the holding block 1;
Is a pulley that rotates integrally with the rotating body 2, 4 is an injection servomotor that rotates the pulley 3 via a timing belt 5, 6 is a ball screw mechanism that converts rotary motion into linear motion, 7 is a rotating body A screw shaft 8 of the ball screw mechanism 6 that rotates integrally with the nut 2; a nut body 8 of the ball screw mechanism 6 that linearly moves on the screw shaft 7 by rotation of the screw shaft 7;
Reference numeral 9 denotes a moving block that is guided by a plurality of guide bars 10 and can move forward and backward. Reference numeral 11 denotes a screw holder that is rotatably held by the moving block 9 and is driven to rotate by a measuring servomotor (not shown). The base end of the screw is fixed to the screw holder 12, and the main part of the screw is disposed in a heating cylinder (not shown).

In FIGS. 1 and 2, reference numeral 13 denotes a load cell unit for detecting the pressure applied to the screw 12. Reference numeral 14 denotes a stress detecting element holding cylinder of the load cell unit 13 having a strain gauge (stress detecting element) attached to the inner or outer peripheral surface thereof. The nut body 8 is held so as to be sandwiched between the end face of the body 8 and the end face of the screw holding body 11, and the axial movement of the nut body 8 is transferred via the stress detecting element holding cylinder 14 to the screw holding body 11. (That is, the screw 12). Reference numeral 15 denotes a box integrally attached to the lower part of the outer peripheral surface of the stress detecting element holding cylinder 14.
5, an amplifier, an A / D converter, an arithmetic control unit, and a serial communication unit are built in.
5, a cable (not shown) connected to the connection portion 15a is connected to an input portion of a control device disposed in a main housing below the injection molding machine.

In the configuration shown in FIG. 1, during the weighing process, the screw 12 is rotated in a predetermined direction together with the screw holder 11 by the rotation of a weighing servomotor (not shown). The resin pellets charged into the heating cylinder begin to be transferred to the screw tip side by the screw feeding action. At this time, the resin is transferred while being kneaded and plasticized by the heating by the heating cylinder and the shear heating action by the rotation of the screw, and the molten resin is fed to the screw tip side.
Then, as the molten resin is stored on the tip side of the screw 12, the screw 12 retreats while the back pressure is controlled by the injection motor 4, and one shot of the molten resin is stored on the tip side of the screw 12. At this time, the rotation of the weighing servomotor is stopped, and the weighing process ends.
During the injection stroke, the rotation of the injection motor 4 causes
Through the timing belt 5, the pulley 3, the rotating body 2, the ball screw mechanism 6, the stress detecting element holding cylinder 14, and the screw holding body 11, the screw 12 is rapidly driven forward, and the molten resin accumulated on the screw tip side is It is injected and filled into a mold (not shown) (primary injection in the injection process),
The holding force is applied to the resin in the mold by the driving force of the injection motor 4 (holding pressure in the injection stroke).

The pressure applied to the screw 12 is detected by the load cell unit 13 for the back pressure control at the time of the weighing process or the injection pressure control at the time of the injection process. Sent to

FIG. 3 is a block diagram showing the load cell unit 13 and the control device. In the figure, 1
Reference numeral 6 denotes a strain gauge adhered to the peripheral surface of the stress detection element holding cylinder 14, reference numeral 17 denotes an amplifier that amplifies the detection output of the strain gauge 16, and reference numeral 18 denotes an A / A that converts an analog signal output from the amplifier 17 into a digital signal. A D converter 19; an arithmetic control unit 19 for controlling the load cell unit 13; and 20 a serial communication unit (serial I / O) for transmitting an output signal of the A / D converter 18 as a serial data signal.
O), the amplifier 17, the A / D converter 18, the arithmetic control unit 19, and the serial communication means 20 are arranged in the box 15. The arithmetic control unit 19 controls each unit in the load cell unit 13 to perform control of detection and A / D conversion, control of communication with the outside, and the like. It performs unit conversion processing and the like according to the mounting unit to be mounted.

Reference numeral 21 denotes a control device provided in the main housing below the injection molding machine. The connection portion 21a for the load cell of the control device 21 and the connection portion 15a of the load cell unit 13 are transmitted. Cable 30
Interconnected by Although shown in a simplified manner in FIG. 3, the transmission cable 30 transmits a detection signal based on serial data from the load cell unit 13 to the control device 21, and supplies and starts power from the control device 21 to the load cell unit 13. Transmission of a control signal such as / stop is performed.

In the control device 21,
Reference numeral 22 denotes a serial communication unit (serial I / O) that performs serial communication with the serial communication unit 20, 23 denotes a CPU that controls the overall control of the control device 21, and 24 denotes an R that reads and writes various data and also functions as a work area.
AM and 25 are ROMs storing main programs and the like, 2
Reference numeral 6 denotes a serial I / O interface for controlling output to various actuators and display devices and input control from a keyboard device or the like; 27, a driver unit connected to the serial I / O interface 24; It is a connector part to be connected to.

In the configuration shown in FIG. 3, when a start signal is transmitted from the control device 21 side, the arithmetic and control unit 19 controls each unit in the load cell unit 13 and outputs the detection output of the strain gauge 16 to the amplifier 17. Then, the digital signal is converted into a digital signal by the A / D converter 18, further converted into serial data by the serial communication means 20, and a detection signal based on the serial data signal is transmitted through the transmission cable 30. From the load cell unit 13 to the control device 21
Is transmitted to the serial communication means 22. The control device 21 appropriately converts the pressure detection signal based on the input serial data signal as necessary,
It is stored in a predetermined area of the AM 24 and is used as detected pressure data (actually measured pressure data) in injection control and metering control.

As described above, in the present embodiment, the pressure detection signal output from the load cell unit 13 to the control device 20 is transmitted as digitized serial data. As a result, there is no possibility that an error occurs in pressure detection, and the pressure detection accuracy is improved. Therefore, the variation in resin density is reduced as much as possible, and the quality of molded products is improved. Further, since the serial communication is controlled, the number of signal lines can be reduced, and the noise immunity can be improved.

In the above-described embodiment, the detection of the pressure applied to the screw is taken as an example. However, the detection of the pressure applied to other members driven forward and backward in the molding machine (for example, the detection of the clamping force) is also applicable. The present invention is applicable.

[0019]

As described above, according to the present invention, the detection error of the pressure applied to the driven member driven forward and backward such as the screw can be reduced as much as possible.
It is possible to improve the quality of molded products.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a main configuration of an injection mechanism in an inline screw injection molding machine according to an embodiment of the present invention.

FIG. 2 is a side view of the load cell unit in FIG.

FIG. 3 is a block diagram showing a load cell unit and a control device according to an embodiment of the present invention.

FIG. 4 is an explanatory view showing a load cell unit and a control device according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Holding block 2 Rotating body 3 Pulley 4 Injection servomotor 5 Timing belt 6 Ball screw mechanism 7 Screw shaft 8 Nut body 9 Moving block 10 Guide bar 11 Screw holder 12 Screw 13 Load cell unit 14 Stress detection element holding cylinder 15 Box Reference Signs List 16 strain gauge 17 amplifier 18 A / D converter 19 arithmetic control unit 20 serial communication means 21 control device 22 serial communication means 23 CPU 24 RAM 25 ROM 26 serial I / O interface 27 driver unit 28 connector unit 30 transmission cable

Claims (2)

[Claims] 1. A molding machine in which a load cell unit for detecting a pressure applied to a driven member is attached to a driven member that is driven forward and backward by a driving source, wherein a holder for a stress detection element in the load cell unit is provided. An amplifier for amplifying the output of the stress detection element, an A / D converter for converting an analog output signal of the amplifier into a digital signal, and serializing an output signal from the A / D converter. A pressure detecting device for a molding machine, comprising: serial communication means for transmitting as a data signal; and transmitting a serial data signal from the serial communication means to a control device provided in the molding machine. 2. The inline screw injection molding machine according to claim 1, wherein a screw holding body holding a base end side of the screw in the in-line screw type injection molding machine and a linear moving body of a ball screw mechanism that converts a rotational motion into a linear motion. The amplifier, the A / D converter, and the serial communication means are arranged in a box which holds the holder of the stress detecting element and is integrally attached to the outer peripheral surface side of the holder. Pressure detection device of the molding machine.