JPH0434929B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves heating and fluidizing a required resin material,
This invention relates to an injection molding machine that presses plastic products into a mold to form plastic products.

[Prior Art] FIG. 2 shows a conventional electric injection molding machine, which is equipped with a mold clamping device A and an injection device B.
The mold clamping device A is set up on a frame 3 with a fixed platen 1 and an end plate 2 facing each other, and a movable platen 5 is attached to a tie bar 4 installed horizontally between the fixed platen 1 and the end plate 2. is supported so that it can move back and forth. A stationary die 1a and a movable die 5a are fixedly installed on opposing surfaces of the stationary platen 1 and the movable platen 5, and a mold M is constituted by the two. A toggle mechanism 6 is disposed between the end plate 2 and the movable plate 5, and this toggle mechanism 6 is connected to a ball screw mechanism 7 disposed on the end plate 2. is driven by the mold clamping motor 11 via the timing pulley 8, timing belt 9, and timing pulley 10 to move the movable platen 5 and clamp the mold,
The mold is now being opened. The toggle mechanism 6 is configured to connect a plurality of link members 12 to increase mold clamping pressure by lever principle, and the ball screw mechanism 7 is connected to the end plate 2 via a thrust bearing 13. Combining the rotatably supported ball nut 14 and the ball screw 15, the ball nut 14 is rotated to connect the ball screw 1.
5 is moved in a straight line.

On the other hand, in the injection device B, a slide tie bar 18 is installed horizontally between a pair of support plates 16 and 17 that are erected facing each other on a pedestal 3a, and a drive plate 19 is reciprocated on this slide tie bar 18. Supported. An injection cylinder 21 equipped with a nozzle 20 and a heating device (not shown) is fixedly supported on the support plate 16 on the front side (on the mold clamping device A side).
A screw 22 is inserted into the screw 22 so as to be movable in the axial direction, and a base end 22a of the screw 22 is rotatably supported by the drive plate 19 via a thrust bearing 23. This screw 22 is connected to a screw rotation motor 2 mounted on a drive board 19.
4 through the timing pulley 25, timing belt 26, and timing pulley 27, and a ball screw mechanism 28 provided between the drive board 19 and the rear support board 17 rotates the timing pulley 29, the timing belt 30, the drive plate 19 itself is reciprocated by being driven by an injection motor 32 via a timing pulley 31, and the screw 22 is moved back and forth in the axial direction within the injection cylinder 21. In addition, mounts 3, 3
a device that moves one side of the nozzle 20 forward or backward, and an ejector device that is provided in the mold M to eject and drop the molded product (both not shown)
etc., and these devices are usually
It is driven by converting the rotation of the electric motor into linear motion by the above-mentioned ball screw mechanism.

In such an injection molding machine, a series of operations are performed, namely, an opening/closing operation of the mold M, a moving operation of the movable platen 5, a mold clamping operation, a forward movement of the nozzle 20 as an injection preliminary operation, and an operation inside the mold M. The injection operation of the resin material into the resin material, the operation of supplying the resin material in preparation for the next injection, that is, the movement of the screw 22, the operation of removing the internal pressure of the resin material in the injection cylinder 21 to prevent defective molding, the retraction operation of the nozzle 20, the mold M A series of continuous operation operations such as cooling/mold clamping sustaining (holding pressure) operations to ensure the specified molding quality, opening/closing operations of the mold M, ejector forward operation to take out the molded product, and ejector backward operation are performed continuously. I'm starting to do it more and more.

[Problems to be Solved by the Invention] Such electric injection molding machines have better control responsiveness than conventional hydraulically driven machines.
It has the advantage of being able to produce precision molded products, as well as making the work environment cleaner and saving energy. By the way, as the demand for precision molded products increases, it has become necessary to control the pressure inside the mold M with even higher precision when repeatedly molding. It is also requested to improve the To achieve this, it is necessary to perform the above-mentioned series of driving operations with higher accuracy, but the above method of converting the rotational output of the drive motor into reciprocating motion via the ball screw mechanism There is a limit to the ability to meet the above demands, as delays in operation are unavoidable due to play and friction between the screw and ball nut, vibration moment of the ball screw, and the like.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an injection molding machine that improves the response characteristics of the machine by using a linear motor as an actuator.

[Means for Solving the Problems] In order to solve the above problems, the present invention employs the following injection molding machine.

That is, a mold clamping device moves a movable platen forward and backward along tie bars relative to a fixed platen to open and close the molds attached thereto, and a mold clamping device that moves a movable platen back and forth along tie bars to open and close the molds attached thereto, and a mold clamping device that moves a movable platen back and forth along tie bars to open and close the molds attached thereto; In an injection molding machine equipped with an injection device that drives a rotatably inserted screw to supply resin to the mold, the tie bar is made of metal, and the movable platen is driven by a linear motor, The linear motor is characterized by comprising the tie bar serving as a secondary conductor and a stator provided on the movable platen passing through the tie bar.

[Function] In such an injection molding machine, the movable platen is driven directly and linearly by a linear motor without a motion conversion mechanism or deceleration mechanism, and the voltage and current of the power supply supplied to this linear motor are controlled. As a result, the position of the movable mold and screw, the driving torque, etc. are directly controlled.

Furthermore, since the tie bars also serve as secondary conductors, there is no need to separately provide a secondary conductor, which simplifies the structure and makes it possible to downsize the mold clamping device.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. Note that the same parts as in the conventional example described above have the same reference numerals, and a description thereof will be omitted.

FIG. 1 shows an embodiment of the present invention, in which the toggle mechanism is removed from the mold clamping device A, and a cylindrical stator 42 is fixed around the through hole through which the tie bar 4 passes through the movable platen 5. , tie bar 4
becomes the secondary conductor 41 and the mold clamping linear motor 43
is configured. In addition, in the injection device B, the upper slide tie bar 18 is connected to the secondary conductor 44.
A cylindrical stator 45 is fixedly installed at a position on the drive board 19 that is fitted onto the secondary conductor 44, and the two constitute an injection linear motor 46.

As the above-mentioned linear motors 43 and 46, linear induction motors, linear direct current motors, etc. are used that take advantage of their respective characteristics. Also,
A position detector that detects the position of the movable platen 5 or the drive platen 19, and a pressure detector that directly or indirectly detects the pressure of the resin in the mold M are attached, and furthermore, the detection of these detectors The difference between the value and the preset position and pressure setting values is detected, and a control signal is sent to the control mechanism (consisting of a direction/speed command section, a torque limiter, etc.) of the linear motors 43 and 46 according to the detected value. A control device is provided for generating. An example of the above-mentioned pressure detector is one in which a load cell is attached to the base end 22a of the screw 22 to detect the distortion of the base end and to detect the reaction force applied to the screw 22.

Next, the operation of the injection molding machine configured as described above will be described.

First, before operating the injection molding machine, various speed, position, and pressure settings are input into the control device. Next, an injection molding process is performed continuously, and one cycle of the process will be described.

When the mold closing start time of one injection molding process comes, the control device generates a drive signal for the mold clamping linear motor 43, and sets the mold protection section (area) to low speed and low pressure in order to protect the mold M. The mold is closed by moving the movable mold 5a by controlling the speed and torque limiter so that the mold closes.

Next, a torque limiter signal corresponding to the mold clamping force is sent to the control device to tighten and hold the movable mold 5a and fixed frame 1a with a constant pressure, and the injection linear motor 4
6 to transfer the resin material in the injection tube 21 to the mold M.
eject into. After that, the base end 2 of the screw 22
The difference between the measured value of the pressure detector provided at 2a and the pressure set value inputted in advance to the control device is detected, and the injection linear motor 46 is driven in accordance with the detected value to control the holding pressure. A signal is generated. In this case, there are two methods: one is to keep the speed command value constant and send a control signal to the torque limiter to specify the torque, and the other is to keep the torque constant and specify the speed command value for control. Next, the screw rotation motor 24 is driven, and the next material is supplied into the injection tube 21. At this time, when the scheduled completion of solidification is reached, the mold clamping linear motor 43 is reversed to open the mold using the same control method as that used during pressure holding, thereby completing one cycle of the process.

As is clear from the above explanation of the structure and operation, in such an injection molding machine, the driving sources are linear motors 43 and 46, so transmission mechanisms such as a timing pool and a timing belt,
Also, there is no need for a mechanism for converting rotational motion into linear motion, and delays in operation are reduced in control. Therefore, the pressure inside the mold M during cooling, which greatly affects the quality of the molded product, can be controlled with high precision, and the process progresses smoothly and molding efficiency is improved.

In addition, the tie bars 4 and 18 are connected to the secondary conductors 41 and 44.
Since it also serves as a secondary conductor, there is no need to separately provide a secondary conductor, the structure is simplified, and the mold clamping device can be made smaller.

In the above description, a pressure detector for detecting the holding pressure is provided at the screw base end 22a, and the injection linear motor 46 is controlled while feeding back the detected value to the control device, which is a so-called closed control. Alternatively, an open control method may be used in which the voltage and current values to the torque limiter of the control mechanism of the injection linear motor 46 at each stage are appropriately determined in advance, and the control is performed only according to the determined values, without providing a pressure detector. good.

[Effects of the Invention] As detailed above, according to the present invention, there is provided a mold clamping device that moves a movable platen forward and backward along tie bars with respect to a fixed platen to open and close a mold attached to the movable platen, and the above-mentioned mold clamping device. , an injection molding machine equipped with an injection device that supplies resin to the mold by driving a screw inserted in an injection cylinder provided on one side of the mold clamping device so as to be freely forward and backward and rotatable; In addition to being made of metal, the movable platen is driven by a linear motor, and the linear motor is composed of the tie bar serving as a secondary conductor and a stator provided on the movable platen that allows the tie bar to pass through. Therefore, the movable platen is driven directly and linearly by a linear motor without a motion conversion mechanism or deceleration mechanism, and by controlling the voltage and current of the power supply supplied to this linear motor, the position of the movable die and screw can be controlled. Drive torque etc. are directly controlled, and unlike conventional electric injection molding machines, there is no need to convert the rotational output of the drive motor into reciprocating motion via a ball screw mechanism. The control response is improved, the pressure inside the mold can be controlled with high precision, and high-quality molded products can be obtained.

In addition, since the tie bars also serve as secondary conductors, there is no need to provide a separate secondary conductor, making it possible to downsize the mold clamping device, which has excellent effects such as lower manufacturing costs and easier maintenance. be able to.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention;
FIG. 2 is a diagram showing a conventional example. 1a... Fixed type, 5a... Movable type, 21... Injection tube, 22... Screw, 43... Linear motor for mold clamping, 46... Linear motor for injection, M...
Mold.

Claims (1)

[Scope of Claims] 1. A mold clamping device that moves a movable platen forward and backward along tie bars with respect to a fixed platen to open and close molds attached to the movable platen, and an injection device provided on one side of the mold clamping device. In an injection molding machine equipped with an injection device that supplies resin to the mold by driving a screw inserted into the cylinder so as to be freely rotatable and move forward and backward, the tie bar is made of metal, and the movable platen is linear. An injection molding machine driven by a motor, wherein the linear motor includes the tie bar serving as a secondary conductor, and a stator provided on the movable platen that passes through the tie bar.