JP2002120266A - Molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding machine having a position detecting unit which dispenses with battery backup and can output an absolute value of an object of measurement with high accuracy. SOLUTION: The molding machine is equipped with a reciprocating member which is driven to move forward and backward in the axial direction and sensor units which detect the position of the reciprocating member and send detection outputs to a host control device. Each sensor unit has a magnetostrictive linear type position detecting sensor for detecting the position of the reciprocating member, a signal processing circuit which processes an output of the magnetostrictive linear type position detecting sensor and generates an absolute position signal and a serial communication means which outputs the absolute position signal outputted from the signal processing circuit, as a serial signal, to the host control device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding machine such as an injection molding machine or a die casting machine, and more particularly, to a position of a reciprocating member which moves in an axial direction such as a movable die plate, an eject plate and a screw in the molding machine. The present invention relates to a technique relating to a means for detecting.

[0002]

2. Description of the Related Art In a molding machine such as an injection molding machine or a die casting machine, detection of the position of a reciprocating member such as a movable die plate, an eject plate or a screw is a prerequisite for control. Position detecting means for detecting the position of the reciprocating member moving in the direction is provided.

The position detecting means is desirably a sensor for measuring an absolute position. As the absolute position measuring sensor, (1) a potentiometer and (2) an absolute type rotary pulse encoder which directly outputs an absolute position are considered. However, the potentiometer of (1) is not suitable for feedback control of an electric molding machine because it is difficult to increase the accuracy in terms of the circuit configuration, and the absolute type rotary pulse encoder of (2) has a high rotational speed. If the model changes and the distance to be measured changes greatly, there may be cases where it cannot be used. Therefore, in this type of molding machine, (3) an incremental rotary encoder is used, and the internal data is held by a holding circuit backed up by a battery. It has been common practice to use it as an (absolute value) measurement sensor.

FIG. 3 is a block diagram showing the configuration of a sensor unit using the above-described incremental type rotary pulse encoder (3) and a host controller. 3, reference numeral 51 denotes a sensor unit; 52, an incremental pulse encoder; and 53, a pulse encoder 52.
Signal processing circuit for appropriately calculating and converting the output of
Is a data holding circuit for updating and holding accumulated data from a given reference value (reference position), and 55 is a battery for backing up the data holding circuit 54 as a battery. Also, 61 is a higher-level control device, 62 is a counter circuit,
63 is an arithmetic control circuit.

[0005] The pulse encoder 52 is attached to a rotary shaft or the like that receives an output of an electric servomotor for linearly driving the reciprocating member. A signal processing circuit 53 sends the output of the pulse encoder 52 to a data holding circuit 54. Calculation and conversion processing is performed with reference to the held contents to generate a position data signal, which is sent to the counter circuit 62 of the host controller 61. The arithmetic control circuit 63 recognizes the position of the reciprocating member to be measured based on the output from the counter circuit 62, and executes a predetermined molding operation control based on this.

[0006]

However, in the prior art shown in FIG. 3, since the data holding circuit 54 is backed up by the battery 55, the data cannot be held when the battery 55 runs out. Cannot output. In addition, since the incremental rotary pulse encoder 52 is used, pulse jumps are generated due to vibration, impact, and the like, and the pulse jumps are accumulated as they are. Also, if there is a transmission accuracy error in the rotation transmission system, the accuracy of position detection of the reciprocating member to be measured deteriorates. Furthermore, in the host control device 61, it is necessary to provide a plurality of counter circuits 62 corresponding to the individual sensor units 51, and there is a problem that the circuit configuration cannot be simplified.

[0007] The present invention has been made in view of the above points,
It is an object of the present invention to provide a molding machine having a position detection unit capable of outputting an absolute value of an object to be measured with high accuracy and requiring no battery backup.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a reciprocating member which is driven forward and backward to move in an axial direction, and detects the position of the reciprocating member to control the detection output. In a molding machine having a sensor unit for sending to a device, the sensor unit processes a magnetostrictive linear position detection sensor for detecting a position of a reciprocating member and an output of the magnetostrictive linear position sensor. And a serial communication means for outputting the absolute position signal output from the signal processing circuit as a serial signal to the host controller.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a sensor unit for position detection and a host control device in an injection molding machine according to one embodiment of the present invention. In the present embodiment, three sensor units are provided for detecting the position of the screw, detecting the position of the movable die plate, and detecting the position of the eject member.

In FIG. 1, reference numeral 1 denotes a sensor unit for detecting a position, 2 denotes a magnetostrictive linear position detecting sensor, and 3 denotes an absolute position by appropriately calculating and converting the output of the magnetostrictive linear position detecting sensor 2. A signal processing circuit that outputs (distance) data and controls the operation of the magnetostrictive linear position detection sensor 2 is a serial communication unit that transmits and receives serial communication data. Reference numeral 11 denotes a host controller, 12 denotes serial communication means for transmitting and receiving serial communication data, and 13 denotes an arithmetic control circuit.

The serial communication means 12 of the host controller 11
Each serial communication means 4 of the three sensor units 1
Are connected by a daisy chain connection format,
Under the communication control management by the arithmetic and control circuit 13, the serial communication means 12 of the host control device 11 communicates with the serial communication means 4 of each sensor unit 1 in a time-division manner and individually according to a predetermined serial communication protocol. It is supposed to do.

In the present embodiment, a start / stop signal for instructing start / end of measurement is sent from the host control device 11 to the sensor unit 1 together with an identification signal for specifying the specific sensor unit 1. When the sensor unit 1 specified by the identification number receives the start signal, the signal processing circuit 3 causes the magnetostrictive linear position detection sensor 2 to start a measurement operation. The signal processing circuit 3 appropriately calculates and converts the output of the magnetostrictive linear position detection sensor 2 to calculate an absolute position of a reciprocating member (for example, a movable die plate) to be measured. The identification signal is added to the data indicating the absolute position, and the data is transmitted as serial communication data from the serial communication means 4 to the serial communication means 12 of the host controller 11. After confirming that the data has been received normally, the host controller 11 sends a stop signal to the sensor unit 1 together with the identification signal. The arithmetic and control circuit 13 takes in the absolute position data of the reciprocating member to be measured received from the sensor unit 1, and executes a predetermined molding operation control based on the data.

FIG. 2 is a diagram for explaining the detection principle of the magnetostrictive linear position detection sensor 2. As shown in FIG. The magnetostrictive linear position detection sensor 2 used in the present invention performs position detection using ultrasonic vibration propagating at a constant speed in a solid. Specifically, an interaction between an external magnetic field 22 generated from the external magnet 21 and a magnetic field 25 caused by a pulse current applied to a coil wire 24 passing through the waveguide 23 causes a so-called Wiedemann effect (strong). Due to the twisting phenomenon that occurs when a current is passed in the axial direction of the cylinder of a magnetic material and a magnetic field is applied in parallel to it (ie, the composition of the magnetic field by the pulse current and the external magnetic field gives a helical magnetic field, and the magnetization by this Due to the phenomenon of torsion caused by magnetostriction accompanying the external magnet 21)
A torsion mode ultrasonic vibration pulse is induced in the waveguide 23 at the position where the ultrasonic wave is located, and the position (distance) is detected using the ultrasonic vibration pulse. That is, since the ultrasonic vibration pulse propagates through the waveguide 23 at a constant speed, the ultrasonic vibration detecting unit 26 starts from the time when the ultrasonic vibration is generated (in other words, the timing when the driving pulse is supplied to the coil wire 24). The distance between the external magnet 21 and the ultrasonic vibration detecting section 26, which is proportional to this time, is detected by knowing the elapsed time until the timing at which the reception pulse is detected. In the present invention, a magnetostrictive linear position detection sensor 2 based on the above-described operation principle is used.
The external magnet 21 is attached to the reciprocating member to be measured directly or via an appropriate fixture, and the waveguide 23 having the coil wire 24 built therein and the ultrasonic vibration detecting unit 26 are It is arranged to be fixed.

Such a magnetostrictive linear position detection sensor 2
Is used, it is possible to detect the position of the reciprocating member to be measured with an absolute value with high accuracy without the need for a battery backup. In addition, since linear position detection is performed, there is no restriction on the number of rotations unlike an absolute type rotation pulse encoder, and a rotation pulse that detects the number of rotations of a rotation shaft that receives the output of an electric servomotor. Unlike the encoder, the position of the reciprocating member to be measured can be directly and accurately detected without being affected by the transmission accuracy error of the rotation transmission system. For this reason,
The rotation of the electric servomotor for opening and closing the mold is transmitted to the toggle link mechanism via the rotation-to-linear motion conversion mechanism, so that the movable die plate is driven back and forth, without the effect of the rotation transmission error and the toggle link. Without considering the input / output distance change characteristic inherent to the mechanism,
The position of the movable die plate can be directly and accurately detected.

In the present embodiment having the above-described configuration, since the magnetostrictive linear position detection sensor that does not require battery backup is used as the position sensor, the object to be measured moves when the power is turned off or the wiring is cut. However, accurate position detection data can be obtained immediately when the power is turned on or wiring is repaired.In addition, since linear position detection is used, there is no restriction on the number of rotations unlike the absolute type rotary pulse encoder, and rotation transmission is possible. The position of the reciprocating member to be measured can be directly and accurately detected without being affected by the transmission accuracy error of the system. Also, since serial communication is used, the number of wires is smaller than that of parallel communication, and a simple general-purpose communication protocol and communication interface can be used. Furthermore, even when a plurality of sensor units 1 are connected to the host controller, the host controller 1
Since only one serial communication means 12 needs to be provided in one, the load on the circuit scale is reduced.

[0016]

As described above, according to the present invention, it is possible to output an absolute value with high accuracy without the need for a battery backup, and to limit the number of rotations as in an absolute type rotary pulse encoder. A molding machine having a position detection unit that is not affected by transmission accuracy errors of the rotation transmission system can be realized. Further, since the transmission and reception of signals between the detection unit and the higher-level control device are performed by serial communication, the number of wirings can be reduced, and a simple general-purpose communication protocol and communication interface can be used. Furthermore, even when a plurality of sensor units are connected to the host controller, the host controller only needs to be provided with one serial communication unit, so that the load on the circuit scale is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a position detection sensor unit and a host control device in an injection molding machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a detection principle of a magnetostrictive linear position detection sensor used in an embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a sensor unit for position detection and a host control device according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor unit 2 Magnetostrictive linear position detection sensor 3 Signal processing circuit 4 Serial communication means 11 Host controller 12 Serial communication means 13 Operation control circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01D 5/48 G01D 5/48 A G08C 15/00 G08C 15/00 Z F term (Reference) 2F063 AA02 BA21 CA14 DA05 EA02 GA56 KA01 KA03 2F068 AA02 CC04 FF03 FF12 FF25 GG02 2F073 AA21 AB02 AB03 BB04 BC01 CC01 CC12 DD05 DE13 GG01 2F077 AA24 AA49 CC02 MM03 PP18 QQ15 TT78 WW08 4F206 AP067 JA07 JP13

Claims (2)

[Claims] 1. A molding machine comprising: a reciprocating member which is driven forward and backward to move in an axial direction; and a sensor unit which detects a position of the reciprocating member and sends a detection output to a host controller. A unit configured to detect a position of the reciprocating member; a magnetostrictive linear position detection sensor; a signal processing circuit configured to process an output of the magnetostrictive linear position detection sensor to generate an absolute position signal; A serial communication means for outputting an absolute position signal output from the processing circuit as a serial signal to the host controller. 2. The molding machine according to claim 1, wherein each serial communication unit of the plurality of sensor units is daisy-chain connected to the serial communication unit of the host control device.