JPH0548733B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a nozzle touch control device for an injection molding machine. In particular, it relates to a nozzle touch control device of the type that uses force from a drive source to move the injection unit via a spring to bring the nozzle into contact with the mold, and controls the pressure force of the nozzle against the mold by the amount of expansion and contraction of the spring. .

Prior Art The nozzle touch mechanism in conventional injection molding machines uses a hydraulic cylinder to press the nozzle against the mold using hydraulic pressure. Then, the nozzle was always pressed against the mold at a constant pressure to perform injection. Also, a method has been proposed in which the nozzle touch mechanism is driven by a motor (Japanese Patent Application No. 148220/1982, Japanese Patent Application No. 148221). In this method, the driving force of the motor is transmitted to the injection unit via a spring to press the nozzle against the mold, and even after the nozzle touches the mold, the motor is driven and the spring is activated so that the injection unit continues to move forward. By compressing or elongating the spring by a certain amount, the elastic repulsion force of the spring is used to press the nozzle against the mold at a certain pressure.

Problems to be Solved by the Invention In the nozzle touch mechanism in which the ejection unit is moved by the motor via a spring and the nozzle is pressed and held against the mold by the elastic repulsive force of the spring, the nozzle is attached to the mold. Since the force to press and hold the nozzle is due to the force generated by the amount of compression or expansion of the spring, the force to press and hold this nozzle against the mold can be controlled by detecting the amount of compression or expansion of the spring.
The pressing force was controlled by stopping and holding the injection unit at a set position.

Therefore, when driving the motor to advance the injection unit (move toward the mold), if the injection unit is moved forward at a fast speed, even after the detector detects the set spring compression or expansion amount, the detector and other controls Due to a delay in the means or the inertia of the injection unit, etc., the injection unit may stop at a position that has advanced too far, and the nozzle may press the mold with a pressure higher than the set pressure. In such a case, an excessive load is applied to the fixed plate to which the mold is fixed, causing problems such as bending of the fixed plate. Therefore, if the forward speed of the injection unit is slowed down, it will take more time and the effect will deteriorate.

Also, when a sprue break is performed during the injection cycle to remove the nozzle from the mold, and then the nozzle is pressed against the mold again, the spring may become too compressed or overstretched due to static friction at the moment the injection unit is moved forward. If the pressure is too high, the detector will activate and stop the motor, and the pressure of the nozzle against the mold may be insufficient, or the nozzle may not contact the mold, causing the injection unit to stop and start injection. There was also the problem of doing so.

SUMMARY OF THE INVENTION The present invention has been proposed in order to solve the above-mentioned problems, and it is an object of the present invention to provide a nozzle touch control device that can constantly generate and maintain a set pressing force of a nozzle against a mold.

Means for Solving the Problems In order to solve the above problems, the present invention provides two sensors for detecting the amount of compression or extension of the spring, and the motor is operated at high speed until the first sensor outputs a detected output. A control means is provided which drives the motor at a low speed after the first sensor outputs a detection output, and stops driving the motor upon receiving the detection output from the second sensor.

Operation The motor is driven at high speed and the injection unit is moved to the mold side via the spring. When the nozzle comes into contact with the mold and the spring starts to compress or expand, the first sensor detects this and the above-mentioned The control means receives the detection output from the first sensor and switches the motor to low speed drive. Then, when the spring is further compressed or expanded and the pressure with which the nozzle presses the mold becomes the set pressure, the second sensor outputs a detection output and drives the motor. Then, the nozzle is pressed against the mold at the set pressure and held.

Embodiment FIG. 1 is a schematic diagram of an embodiment of the present invention, and FIG. 2 shows the main parts of the nozzle touch mechanism when the injection unit is removed from FIG. 1.

1 is an injection unit, 2 is a heating cylinder, 3 is a nozzle provided at the tip of the heating cylinder, 4 is a fixed plate to which a mold is attached, 5 is an extruder base that slides on a rail 6, and the extruder The injection unit 1 is fixed on the base. 7 is a transmission mechanism fixed to the fixed platen 4, 8
1 is a motor; 9 is a ball screw rotatably driven by the motor 8 through a transmission mechanism 7;
0 is a ball nut screwed into the ball screw, 1 is a first plate fixed to the ball nut 10, and 12 is a second plate fixed to the shafts 14, 14 fixed to the first plate 11. The shafts 14, 14 pass through holes 33 provided at the bent and raised ends of the extruder base 5, and
2 and the end of the extruder base 5 is a spring 1.
3 and 13 are provided. Further, the extruder base 5 is provided with a sensor mounting plate 37, and the sensor mounting plate 37 has first and second sensors such as two proximity switches.
sensors S1 and S2 are provided, and the first plate 1
1 position is detected. In addition, 3
4, 35, and 36 are holes through which ball screws are respectively provided in the first plate 11, the end of the extruder base 5, and the second plate 12;
26 is driven by a transmission device 7 and a ball screw 9
15 is the base of the injection molding machine. Reference numeral 20 is a control device for controlling the injection molding machine, such as a numerical control device, and only the parts related to the present invention are described, and 21 is a microprocessor (hereinafter referred to as
22 stores the control program
A memory consisting of ROM and RAM for temporary storage of data, etc.; 23 is a manual input device 24 for inputting various commands, setting values, etc.; an input/output circuit; the motor 8 is driven through the input/output 24; The motor driving force circuit 26 to control, the first and second sensors S1,
Connected to S2. And these CPU21,
Memory 22, manual input device 23, input/output circuit 24
are connected by bus 25.

The nozzle touch mechanism according to the present invention having the above-mentioned structure has almost the same structure as the nozzle touch mechanism described in the above-mentioned Japanese Patent Application No. 148220/1980, etc., but the first and second sensors S1, S2 The difference is that there are two. and,,
The arrangement positions of the first and second sensors S1 and S2 are the first and second sensors.
The sensor S1 is arranged at such a position that the first sensor S1 detects the first plate 11 when the injection unit 1 moves forward, the nozzle 3 comes into contact with the mold, and the spring 13 is slightly compressed. The second sensor S2 is arranged at a position where the nozzle 3 is pressed against the mold and the amount of compression of the spring 13 equal to the set pressure is obtained.

Therefore, to outline the operation of this nozzle touch mechanism, the motor 8 is driven to rotate in the forward direction, and the rotation shaft 26
When the rotary shaft 26 rotates forward, the ball screw 9 rotates forward, and the ball nut 10 screwed into the ball screw 9 moves forward (see FIGS. 1 and 2).
right side in the figure), and as a result, the first plate 11 fixed to the ball nut 10 also moves forward, and the shafts 14, 14 fixed to the first plate 11 also move forward.
4 is also moved forward, and the second plate is fixed to
The plate 12 presses the springs 13, 13 and presses the end of the extruder base 5 via the springs 13, 13, so the extruder base 5 slides on the rail 6 and The fixed injection unit 1 is advanced to bring the nozzle 3 into contact with the mold. Even if the nozzle 3 contacts the mold, if the motor 8 is further driven, the ball nut 10 and the first and second plates 11 and 12 will move forward even though the extruder base 5 is stopped. Therefore, first, the first sensor S1
detects the plate of the motor 8 and outputs the detection output.
drive at a low rotational speed. On the other hand, the springs 13, 13 are compressed by the second plate 12, and the reaction force due to this compression is transmitted to the extruder base 5, and becomes a force for pressing the nozzle 3 against the mold. Then, the second sensor S2 detects the first plate, and the drive of the motor 8 is stopped based on this signal. That is, the amount of compression of the springs 13, 13 is detected by the sensor 37, and when the appropriate amount of compression, that is, the appropriate pressing force is reached, the second sensor
S2 detects the first plate 11 and stops the motor 8.

Although the above-mentioned operation is performed, the conventional technology described in the above-mentioned Japanese Patent Application No. 148220/1983 is only provided with the second sensor S2, and if the driving speed of the motor 8 is fast, Even if the second sensor S2 detects the first plate, due to the delay until the motor 8 stops, excessive pressure may be applied to the mold from the nozzle 3, or the nozzle 3 may be pressed against the mold after sprue break. When spring 1 due to static friction
3 and 13 are compressed and the nozzle 3 comes into contact with the mold, the second sensor S2 detects the first plate and stops driving the motor 8. The present invention is an improvement on this point, and the operation of the above embodiment of the present invention will be explained below with reference to the operation flowchart of FIG.

First, the CPU 21 determines whether a forward command for the injection unit 1 has been issued (step 101), and if so, determines whether the second sensor S2 is already on (step 102). If so, it means that the nozzle is in contact with the mold and is pressing with the set pressing force, so this nozzle touch process ends. If the second sensor S2 is not on, then it is determined whether the first sensor S1 is on (step 103). If the first sensor S1 is not turned on (the nozzle 3 is detached from the mold), the CPU 21 drives the motor drive circuit via the input/output circuit 24 to drive the motor 8 at the set high speed. (Step 104), then it is determined whether a forward command has been issued again (Step 105), and if so, the process from Step 103 onward is performed again in the first step.
Repeat until sensor S1 turns on. In addition,
If there is no forward command in step 105, the drive of the motor 8 is stopped to stop the forward movement of the injection unit 1 (step 106), and the process returns to step 101 again. The first and second plates 11 and 12 are advanced through the ball screw 9 and the ball nut 10 by high-speed driving of the motor 8, and the extruder base 5 is advanced through the spring 13 to advance the injection unit 1. When the nozzle 3 comes into contact with the mold and the injection unit 1 and extruder base 5 stop moving forward, the first and second plates 11 and 12 move forward while compressing the springs 13 and 13. , which causes the first sensor S1
detects the first plate 11 and outputs an output (step 103), the CPU 21 drives the motor 8 at a set low speed rotation (step 107). As a result, the first and second plates 11 and 12 continue to move forward at low speed while compressing the spring 13. meanwhile,
The CPU 21 determines whether or not the second sensor S2 is turned on (step 108), and if it is not turned on, determines whether a forward command is issued (step 109), and if it is, the process proceeds to step 103. The following process is repeated, and since the first sensor S1 is already on, the first and second plates are advanced at low speed and the spring 13 is continued to be compressed as described above. (In addition,
If the forward command is not issued in step 109, the drive of the motor 8 is stopped (step 110), and the step
Return to 101. ). Then, when the second sensor S2 is turned on, that is, the spring 13 is compressed, and the first and second plates 11 and 12 move forward to a position where the second sensor S2 detects the first plate 11.
The repulsive force generated by the compression of the spring 13 is applied to the nozzle 3.
When the mold is pressed with the set pressure, the CPU 21 stops driving the motor 8 and starts the timer T (step 111). and,
When timer T passes the set time (step
112), this nozzle touch process ends, and the process moves to the next sequence process. In addition, steps 111 and 112
The process of waiting until the time set by the timer T has elapsed after stopping the motor 8 is provided to wait for the nozzle 3 to be positioned at an appropriate position on the sprue bush of the mold.

In the above embodiment, the spring 13 is compressed so that the nozzle 3 presses against the mold, but the spring is expanded and its pulling force is used to press the nozzle 3 against the mold. It's okay.

Effects of the Invention As described above, two sensors are provided to detect the amount of compression or expansion of the spring, and the motor 8 is driven at high speed to advance the injection unit 1 until the first sensor S1 is activated. After the sensor S1 of No. 1 is activated (after the nozzle 3 contacts the mold), the injection unit is advanced at low speed, and when the pressing force of the nozzle 3 against the mold reaches the set value, that is, the spring When the compression amount or expansion amount reaches the set value and the second sensor S2 is activated, the motor drive is stopped and the nozzle is pressed and held against the mold by the repulsive force or tensile force generated from the spring. Therefore, the operation of the nozzle touch is sped up, and the rotation speed of the motor is slow near the set pressure, so there is a delay from the detection of the set pressure, inertia, etc. from the nozzle to the mold or fixed plate. No excessive force is applied. In addition, when performing a nozzle touch after a sprue break, the first sensor is activated and the motor is driven at a low speed after that, so when the movement changes from static friction to dynamic friction at the start of driving, the spring expands and contracts instantaneously. Even if the first sensor operates, the second sensor does not operate, so the motor stops without the nozzle contacting the mold or reaching the set pressing force, and the next injection stroke etc. There will be no transition to .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is a plan view showing essential parts of a nozzle touch mechanism in the embodiment, and FIG. 3 is a flowchart of operation processing of the embodiment. DESCRIPTION OF SYMBOLS 1...Injection unit, 3...Nozzle, 5...Extruder base,...Motor, 9...Ball screw, 10...Ball nut, 11...First plate, 12...Second plate, 13...Spring, S1...
First sensor, S2...second sensor.

Claims (1)

[Scope of Claims] 1. In a nozzle touch control device in which the driving force of a motor is transmitted to an injection unit via a spring to move the injection unit and press a nozzle against a mold, the amount of compression or expansion of the spring is The motor is driven at high speed until a detection output is received from the first sensor, and when the detection output is output from the first sensor, the motor is driven at low speed. A nozzle touch control device, comprising: a control means for driving the motor and stopping the driving of the motor when a detection output is output from the second sensor. 2. The nozzle touch control device according to claim 1, wherein the control means outputs a nozzle touch end signal after a certain period of time after receiving the detection output from the second sensor and stopping the motor.