JP2003231154A - Injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection device with a simplified constitution of a control system for driving a plurality of linear motors, in an injection device which directly drives an injection screw by a plurality of linear motors. <P>SOLUTION: This injection device comprises a heating barrel equipped with a nozzle at the tip, an injection screw to inject a molten molding material accumulated in the heating barrel from the nozzle by moving the injection screw forward, a plurality of electrically independent linear motors LM1 to LM4 to move the injection screw forward/backward, a single linear scale 90 to detect the positions of the injection screw and a plurality of the linear motors, and a control device 100 to drive a plurality of the linear motors, based on information on the positions of the linear motors detected by the linear scale 90. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection device using a linear motor as a drive source for an injection screw.

[0002]

2. Description of the Related Art An injection device of an injection molding machine advances an injection screw in a heating barrel in which a molding material is melted and accumulated,
The molding material is injected from the nozzle at the tip of the heating barrel. As a driving method of this injection screw, for example, a method of directly driving by a linear motor is known. Directly driving the injection screw with a linear motor is superior to other drive systems in terms of efficiency, durability, responsiveness, and the like. However, the output of the linear motor is relatively small. For this reason, an injection device has been proposed that realizes a large output by using a plurality of linear motors.

[0003]

By the way, when a plurality of linear motors are used in an injection device, it is necessary to detect the position and speed of each linear motor by a linear scale and control each linear motor. There was a disadvantage that the system became complicated. In addition, if each linear motor is equipped with a linear scale, the injection device becomes larger,
There was also the disadvantage of increased costs. On the other hand, depending on the molding conditions, the required output may be obtained without using all of the plurality of linear motors. In such a case, using all the linear motors has the disadvantage of increasing power consumption. Also existed.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a control system for driving a plurality of linear motors in an injection device in which an injection screw is directly driven by a plurality of linear motors. An object of the present invention is to provide an injection device having a simplified structure. Another object of the present invention is to provide an injection device capable of saving power and capable of precisely controlling the propulsive force of an injection screw.

[0005]

SUMMARY OF THE INVENTION The present invention is an injection device of an injection molding machine for injecting and filling a molding material into a mold,
A heating barrel having a nozzle at its tip, an injection screw that is inserted into the heating barrel and injects the molding material melted and accumulated in the heating barrel from the nozzle by forward movement, and is commonly connected to the injection screw, Based on a plurality of electrically independent linear motors that move the injection screw forward and backward, a single linear scale that detects the positions of the screws and the plurality of linear motors, and position information that the linear scale detects. , And control means for driving the plurality of linear motors.

[0006] Preferably, the control means is a minimum of the plurality of linear motors required to satisfy the propulsive force of the injection screw required for filling the mold with the molding material and maintaining the pressure. Select a linear motor and drive and control only the selected linear motor.

In the present invention, the injection screw is commonly connected to a plurality of linear motors, and the propulsive force of this injection screw is the sum of the propulsive forces of the respective linear motors. The positions of the injection screw and each linear motor are detected by a single linear scale, and each linear motor is drive-controlled by the control means based on the position information detected by this single linear scale. Further, the position information of the injection screw is also acquired by the single linear scale described above.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 is a diagram showing an example of a basic configuration of an injection molding machine to which the injection device of the present invention is applied. Injection molding machine 1 shown in FIG.
Is a mold clamping device 3 installed on the base 2 and an injection device 4
Has 0 and.

The mold clamping device 3 includes a support plate 4, a moving plate 5,
It has a movable die 80 fixed to the movable platen 5, a fixed platen 6, a fixed die 81 fixed to the fixed platen 6, and a toggle mechanism 8 connecting the support platen 4 and the movable platen 5.

The support board 4 is provided on the base 2 so that its position can be adjusted, and is connected to the fixed board 6 via a movable die 5 by four tie bars 7 arranged in the horizontal direction. The tie bar 7 is inserted into a through hole (not shown) formed in the moving platen 5. The support board 4 is connected to the moving board 5 by a toggle mechanism 8. The toggle mechanism 8 has a plurality of links 8a, 8b, 8c and a crosshead 8d. One end of the link 8a is rotatably connected to the support board 4, and the other end is rotatably connected to one ends of the links 8b and 8c. The other end of the link 8b is rotatably connected to the movable platen 5. The other end of the link 8c is rotatably connected to the crosshead 8d.

The crosshead 8d is connected to the linear drive shaft 16. The linear drive shaft 16 is connected to a linear motor 15 provided on the back side of the support board 4, and is linearly moved by the linear motor 15 in the mold opening / closing directions indicated by arrows A1 and A2. When the linear motion shaft 16 moves in the mold opening direction indicated by the arrow A1, the links 8a, 8b, 8c are interlocked, and the movable platen 5 moves along the tie bar 7 in the mold opening direction A1. Linear axis 1
When 6 moves in the mold closing direction indicated by arrow A2, link 8
The a, 8b, and 8c are interlocked, the movable platen 5 moves in the mold closing direction A2, and the movable mold 80 and the fixed mold 81 are closed. When the linear motion shaft 16 further moves in the mold closing direction A2 from the state where the movable mold 80 and the fixed mold 81 are closed, the toggle mechanism 8 self-locks, and the movable mold 80 and the fixed mold 81.
The mold is clamped.

Screws (not shown) are formed at the ends of the four tie bars 7 on the side of the support board 4, and a nut (not shown) with which the screws of the tie bars 7 are screwed is rotatably provided on the support board 4. Has been. These nuts can be rotated synchronously by a mold thickness adjusting motor 18 fixed to the support board 4 via a gear train 19 provided on the back surface side of the support board 4. By controlling the amount of rotation of the die thickness adjusting motor 18, the die opening / closing directions A1 and A of the support board 4 are controlled.
2 position adjustment is possible. The position of the support board 4 is
Mold opening / closing directions A1 and A of the movable mold 80 and the fixed mold 81
According to the thickness of 2, the toggle mechanism 8 is adjusted so as to obtain a desired mold clamping force when the toggle mechanism 8 self-locks.

The movable platen 5 is provided so as to be movable along the tie bar 7 and holds a movable mold 80. On the back side of the movable platen 5, a linear motor 10 for driving an extrusion pin 11 provided so as to project on the mold surface of the movable mold 80.
Is provided. The push-out pin 11 is provided to push out the molded product molded in the cavity C formed between the movable mold 80 and the fixed mold 81 from the movable mold 80.

The fixed platen 6 is fixed on the base 2 and holds a fixed mold 81 so as to face the movable mold 80. An injection device 40 is arranged on the back side of the stationary platen 6.

The injection device 40 has a heating barrel 50 having a nozzle 51 for injecting a molding material at its tip, an injection screw 53 inserted in the heating barrel 50, and a measuring motor 46 for rotating the injection screw 53. And a drive unit 60 for directly moving the injection screw 53 in the directions indicated by arrows B1 and B2.

The heating barrel 50 is fixed on the movable table 41 and moves together with the movable table 41 in the horizontal direction indicated by arrows C1 and C2. A heater 52 is provided on the outer peripheral portion of the heating barrel 50, and the heating barrel 50 heats the heating barrel 50 to a predetermined temperature. A hopper 56 for containing a molding material is fixed to the heating barrel 50, and the molding material made of a resin material housed in the hopper 56 is supplied into the heating barrel 50.

The movable base 41 is provided on the base 2 so as to be movable in the horizontal direction indicated by arrows C1 and C2. A screw shaft 49 rotatably supported on the base 2 is screwed to a connecting member 41 a fixed to the movable base 41. Nozzle touch geared motor 4 is provided at one end of screw shaft 49.
8 is connected. Geared motor 4 for nozzle touch
By driving and controlling 8, the movable table 41 is moved, and the heating barrel 50 is moved and positioned in the horizontal directions C1 and C2. Thereby, the nozzle 51 of the heating barrel 50 comes into contact with the back surface of the fixed mold 6 and the fixed mold 6 of the nozzle 51.
Retreat from the back of the.

The injection screw 53 is inserted into the heating barrel 50, and its rear end is connected to the output shaft 61 of the drive unit 60 via the rotary joint 48. The output shaft 61 linearly moves in the linear movement directions B1 and B2 as described later. Also,
A spline 47 is formed on the rear end side of the injection screw 53, and the pulley 44 is fitted to the spline 47. Further, a load cell 120 is provided between the rotary joint 48 and the output shaft 61. The load cell 120 detects the propulsive force of the output shaft 61 and outputs the detection signal 1
20s is output to the control device mentioned later.

On the other hand, the measuring motor 4 is provided on the drive unit 60 side.
6 is fixed, and the pulley 45 is fixed to the output shaft of the measuring motor 46. Pulley 45 and pulley 44
A timing belt 43 is wound between and.
By driving and controlling the measuring motor 46, the rotation of the measuring motor 46 is transmitted to the injection screw 53 via the pulleys 45 and 44, and the injection screw 53 rotates.
By the rotation of the injection screw 53, the molding material supplied from the hopper 56 is melted while being conveyed toward the nozzle 51 side of the heating barrel 50, and the molding material of an amount corresponding to the rotation amount of the injection screw 53 is heated. Accumulated at the tip.

The drive unit 60 is fixed on the movable base 41 and is provided with a plurality of linear motors for linearly moving the output shaft 61. Further, the scale 91 of the linear scale 90 is fixed to the output shaft 61 of the drive unit 60, and the scale head 9 of the linear scale 90 is mounted on the movable base 41.
2 is fixed to face the scale 91.

In the linear scale 90, the scale head 92 detects the amount of movement of the linear scale 90 which moves together with the output shaft 61. The detection signal 90s is output to each driver described later.

2 is a sectional view showing the structure of the drive unit 60, and FIG. 3 is a sectional view taken along the line AA shown in FIG. The drive unit 60 shown in FIGS. 2 and 3 includes a plate-shaped movable member 68, a plurality (two) of magnets 67 fixed to the upper and lower surfaces of the movable member 68, and a case facing each magnet 67. Multiple (4) coils 6 provided above and below 63
6 and. A plurality (four) of linear motors LM1 to LM4 that are electrically independent of each other are configured by the plurality of magnets 67 and the plurality of coils 66 facing them.

The output shaft 61 is connected to one end of the movable member 68, and as shown in FIG. 3, a linear guide 70 supported by support members 71 fixed to both sides of the case 63.
It is movably held along the axial direction of the output shaft 61. The movable member 68 is formed of a lightweight non-magnetic material such as an aluminum alloy.

The plurality of coils 66 are held by a plurality of coil holders 65 fixed to the upper surface and the lower surface of the case 63, respectively. These coils 66 are composed of three-phase windings, and three-phase AC power is independently supplied from a driver described later. Further, the coils 66 fixed to the upper surface and the lower surface of the case 63 are arranged at symmetrical positions with the movable member 68 in between, and are arranged along the linear movement directions B1 and B2 of the movable member 68.

The plurality of magnets 67 are fixed to the upper surface and the lower surface of the movable member 68 so as to face the coil 66, and the N pole and the S pole are alternately arranged along the linear movement directions B1 and B2 of the movable member 68. It is arranged to be. Further, the plurality of magnets 67 are arranged symmetrically with the movable member 68 interposed therebetween.

In the drive unit 60 having the above structure, the movable member 6 is provided between the coil 66 and the magnet 67 by appropriately supplying electric power to the coils 66 of the linear motors LM1 to LM4.
Propulsive force is generated to move 8 in the linear movement directions B1 and B2. The propulsive force acting on the movable member 68 is the total of the propulsive forces generated by the linear motors LM1 to LM4. By driving each of the linear motors LM1 to LM4, the output shaft 61 moves linearly, and the injection screw 53 connected to the output shaft 61 is driven.

FIG. 4 is a diagram showing a hardware configuration of a control system for driving the linear motors LM1 to LM4 of the injection device 40 having the above configuration. As shown in FIG. 4, the control system of the linear motors LM1 to LM4 includes a plurality of linear motors LM.
A plurality of (four) drivers 105 to 108 respectively connected to 1 to LM4 and a control device 100 connected to the drivers 105 to 108 are included.

The control device 100 includes a processor 101,
It has a ROM 102, a RAM 103, and an input / output unit 104. The ROM 102 is connected to the processor 101 by a bus and stores a system program for controlling the control device 100 as a whole. The processor 101 executes these programs.

The RAM 103 is connected to the processor 101 by a bus and stores various data necessary for controlling the control device 100, a program for controlling the injection device 40, and the like. The processor 101 reads various kinds of data from the RAM 103 and sends various kinds of data to the RAM 1
Write to 03. Further, the processor 101 executes a program for controlling the injection device 40.

The input / output unit 104 includes the processor 101, the drivers 105 to 108, and the load cell 120 described above.
Connected to. The input / output unit 104 is the processor 10
The positions of the linear motors LM1 to LM4 sent from
A control command for controlling the speed or the propulsive force is output to each driver 105-108. The input / output unit 104 receives the detection signal 120s of the load cell 120 and outputs it to the processor 101. Thereby, the control device 10
0 can acquire the propulsive force acting on the output shaft 61 of the injection device 40. The input / output unit 104 includes the detection signal 90s of the linear scale 90 and the linear motors LM1 to LM4.
Various state quantities of the linear motors LM1 to LM4, such as the drive current of the above, are input from the drivers 105 to 108, and these state quantities are output to the processor 101. Thereby, the control device 100 can acquire various information such as the position, speed, and propulsive force of each of the linear motors LM1 to LM4.

The drivers 105 to 108 are connected to the linear motors LM1 to LM4, respectively. The detection signal 90s of the linear scale 90 described above is input to each of the drivers 105 to 108 via the distributor 110. Further, control commands for controlling the positions, speeds, or propulsive forces of the linear motors LM1 to LM4 are input to the drivers 105 to 108, respectively, and the input / output unit 1 of the control device 100.
It is input from 04 respectively.

Here, FIG. 5 shows the drivers 105 to 108.
It is a figure which shows an example of a structure of the control system of FIG. As shown in FIG. 5, the control system of each of the drivers 105 to 108 includes a current loop, a speed loop, and a position loop. The position control unit 201, the speed control unit 202, the current control unit 203,
It has a power conversion unit 204 and a speed conversion unit 205.

The position controller 201 includes a position command Pref as a control command input from the controller 100 and the injection screw 53 (movable member 6) detected by the linear scale 90.
8) A deviation from the position information P is calculated, and the deviation is subjected to, for example, a proportional operation to output the speed command Vref to the speed control unit 202.

The speed control unit 202 receives the speed command Vref from the position control unit 201 and the speed information V from the speed conversion unit 205, calculates the deviation between the speed command Vref and the speed information V, and For example, proportional and integral operations are performed to obtain a current command Iref, which is output to the current control unit 203. The speed conversion unit 205 calculates the difference value per unit time of the pulse signals sequentially output from the linear scale 90 and converts the difference value into the speed V.

The current control unit 203 receives the current command Iref from the speed control unit 202 and the position information P from the linear scale 90. Further, the current control unit 203 is provided with the current sensor Ct provided in two phases (U phase and V phase) of the three phase windings of the coil 66 of the connected linear motor LM.
The current values Iu and Iv detected by are input. The current control unit 203 uses the current command Iref and the current values Iu, Iu.
Based on the position information P from v and the linear scale 90, the drive signal 20 that drives the switching element of the power conversion unit 204 so that the power factor of the linear motor LM becomes 1.
3s is generated and output to the power conversion unit 204.

The power conversion section 204 is composed of, for example, a converter section and an inverter section. The converter section rectifies and smoothes the alternating current supplied from the power source and converts it into direct current. The inverter section has a plurality of switching elements such as transistors, and these switching elements are driven by the drive signal 203s to convert the direct current supplied from the converter section into a three-phase alternating current, and the three-phase of the linear motor LM. It is supplied to the coil 66 composed of a winding. This allows
The linear motor LM generates propulsive force.

The control device 100 controls the position and speed of the linear motor LM by appropriately giving the position command Pref to each of the drivers 105 to 108 having the above-mentioned configuration.
Further, the control device 100 controls the position command Pref and the speed command V
The force control of the linear motor LM is performed by appropriately converting and adding the force command to the ref or the current command Iref.

Next, an example of injection control by the control device 100 of the injection device 40 having the above structure will be described. In general, injection control in an injection molding machine includes a filling step of filling the resin in the cavity C and a pressure holding step of compensating for shrinkage of the resin filled in the cavity C due to cooling. Prior to the filling process, first, the injection screw 53
By the rotation of, the molding material accommodated in the hopper 56 is supplied into the heating barrel 50, and the molding material is melted by the heating of the heater 52 and is accumulated on the front end side of the heating barrel 50. As the accumulated amount increases, The injection screw 53 retracts to a predetermined position.

From this state, the process proceeds to the filling process, and the control device 1
00, the control command for advancing the injection screw 53 in the direction of the arrow B1 shown in FIG.
Are output respectively. Each driver 105-10
The control command to 8 is the same control command. The control command is a command for controlling the linear motors LM1 to LM4 so that the speed of the injection screw 53 becomes a preset speed according to the position of the injection screw 53. A control command is input to each of the drivers 105 to 108, and a detection signal 90s of the linear scale 90 distributed by the distributor 110 is input.

Based on the control command and the detection signal 90s of the linear scale 90, each of the drivers 105 to 108 generates a three-phase AC for driving the corresponding linear motor LM1 to LM4. At this time, each driver 105-1
08 has the same control command and the same detection signal 90s.
Is input, the propulsive forces generated by the linear motors LM1 to LM4 are synchronized with each other and are substantially the same. Therefore, the injection screw 53 commonly connected to these linear motors LM1 to LM4 is
It moves forward with the combined force of the propulsive forces generated in LM4.
By moving the injection screw 53 forward, the heating barrel 50
The molten molding material filled in is injected into the cavity C,
Is filled.

When the filling of the molding material into the cavity C is completed, the pressure holding process is switched to. In the pressure holding process,
From the control device 100 to each driver 10 so that the propulsive force of the linear motors LM1 to LM4 becomes a preset propulsive force.
The same control command is given to 5 to 108. As a result, the molding material filled in the cavity C is held for a predetermined time by the pressure generated by the combined force of the propulsive forces of the linear motors LM1 to LM4. After that, the mold in the mold clamped state is opened, and the molded product is pushed out of the mold by the extrusion pin 11 to complete the molding.

As described above, according to this embodiment, the plurality of linear motors LM1 to LM4 commonly connected to the injection screw 53 of the injection device 40 are controlled by using the detection signal 90s of the common linear scale 90. Therefore, the control system of the injection device 40 can be simplified and the injection screw 53 can be reliably operated. Further, according to the present embodiment, by the single linear scale 90,
It is possible to simultaneously control a plurality of linear motors LM1 to LM4 and obtain position information and speed information of the injection screw 53 necessary for injection control from the linear scale 90.

Second Embodiment In the above-described first embodiment, the control device 100 gives the same control command to each driver 105 to 108 to simultaneously drive a plurality of linear motors LM1 to LM4, and a plurality of the linear motors LM1 to LM4 are simultaneously driven. The case where the injection screw 53 is driven by a propulsive force that is a combination of the propulsive forces generated by the linear motors LM1 to LM4 has been described. By the way, the propulsive force of the injection screw 53 required in the filling step and the pressure holding step is determined by the molding conditions such as the injection speed and the injection pressure determined according to the molded product. Therefore, the necessary propulsive force of the injection screw 53 may be obtained without using all the linear motors LM1 to LM4.

When all the linear motors LM1 to LM4 are used and the required propulsive force of the injection screw 53 is obtained, the disadvantage of using all the linear motors LM1 to LM4 is that power consumption increases. Exists.

The resolution of each propulsive force generated by the linear motors LM1 to LM4 is mainly determined by the resolution of the current sensor Ct described in the above-described first embodiment. For example, the maximum propulsive force that can be generated by each linear motor LM1 to LM4 is 100 N, and the control resolution is 1%.
Then, the resolution of the propulsive force of each linear motor LM1 to LM4 is 1N. On the other hand, the resolution of the propulsive force acting on the injection screw 53 is 4N. Therefore, the larger the number of linear motors used, the coarser the resolution becomes, and the more difficult the precise control of the propulsion force becomes. Further, it is difficult to control the injection speed smoothly unless the propulsion force is precisely controlled.

In the present embodiment, the structure of an injection device which can save power and can precisely control the propulsive force of the injection screw 53 will be described. The basic configuration of the injection device according to the present embodiment is the same as the injection device according to the first embodiment described above, and only the injection control program stored in the RAM 103 of the control device 100 is different.

The injection control in the injection device according to this embodiment will be described below. As described in the above-described embodiment, the injection control in the injection molding machine includes a filling step of filling the resin in the cavity C and a pressure holding step that serves to compensate the shrinkage of the resin filled in the cavity C due to cooling. To be done. Specifically, for example, as shown in FIG. 6, in the filling step, the injection speed of the resin by the injection device 40 is controlled so as to have a preset speed waveform SV. In this filling step, speed control is performed to switch the speed of the injection screw 53 depending on the position of the injection screw 53. On the other hand, in the pressure-holding process, pressure control is performed so that the injection pressure has a preset pressure waveform SP. In this pressure holding step, force control of the injection screw 53 (linear motor) is required. The set speed waveform SV and the set pressure waveform SP are merely examples, and these are variously determined according to the molding conditions of the molded product.

When the set speed waveform SV and the set pressure waveform SP as shown in FIG. 6 are given, the set speed waveform SV
The required propulsive force of the injection screw 53 can be roughly estimated from the set pressure waveform SP. In the present embodiment, the necessary propulsive force of the injection screw 53 is calculated from the preset speed waveform SV and the preset pressure waveform SP given in advance according to the molding conditions,
Select the number of linear motors required to generate the calculated propulsive force and the linear motors to use.

Hereinafter, an example of a specific injection control procedure of this embodiment will be described with reference to the flowcharts shown in FIGS. 7 and 8. 7 is a flowchart showing an example of a processing procedure of the control device 100 before performing the injection control, and FIG. 8 is a flowchart showing an example of a processing procedure at the time of injection control. As shown in FIG. 7, first, the propulsive force NFA required for the injection screw 53 in the filling process is determined based on the set speed data in the filling process input to the control device 100 (step S1). This propulsive force NFA can be determined, for example, from information such as maximum acceleration obtained from set speed data.

Next, the propulsive force NFB required for the injection screw 53 in the pressure maintaining process is determined based on the set pressure data in the pressure maintaining process input to the control device 100 (step S2). This propulsion force NFB is, for example,
It can be determined from information such as the maximum pressure obtained from the set pressure data.

Then, the number Na of linear motors required in the filling process is determined based on the determined propulsive force NFA (step S3). The required number Na of linear motors is the required number Na of linear motors satisfying the following equation (1), where Fm is the maximum propulsive force of each linear motor LM1 to LM4.

[0052] NFA / Fm <x <NFA / Fm + 1 (1)

Next, based on the determined propulsive force NFB, the number Nb of linear motors required in the pressure holding step is determined (step S4). The required number Nb of linear motors is the required number Nb of linear motors that is an integer x that satisfies the following equation (2).

[0054] NFB / Fm <x <NFB / Fm + 1 (2)

After determining the numbers Na and Nb of the linear motors required in the filling process and the pressure maintaining process, the linear motors actually driven in the filling process and the pressure maintaining process are selected from the linear motors LM1 to LM4 (step S).
5). It is preferable to select a linear motor having a positional relationship in which the force acting on the injection screw 53 is as biased as possible when the injection screw 53 is driven.
For example, select linear motors that are arranged as symmetrically as possible. By the above procedure, the linear motor used in the filling process and the pressure holding process is determined.

Next, a processing procedure at the time of injection control will be described. When the injection control is started, the control device 100 drives the linear motor selected in the filling process by the above process (step S10) and controls the speed of the injection screw 53 (step S11).

After starting the speed control of the injection screw 53, the control device 100 determines the timing of switching from the filling process to the pressure holding process (step S12). The switching timing is determined, for example, based on the position of the injection screw 53, the time from the start of injection, the injection pressure, or the pressure in the cavity C.

When the control device 100 detects the timing of switching to the pressure-holding process, it drives the linear motor selected in the pressure-holding process by the above process (step S13) and controls the force of the injection screw 53 (step S13). Step S14). At this time, for example, when the number of linear motors required for the pressure holding process is larger than the number of linear motors required for the filling process, a new linear motor is added in addition to the linear motor that was driven in the filling process. Driven. Further, if the number of linear motors required for the filling process and the pressure holding process is the same, the linear motors that were driven in the filling process are continuously driven in the pressure holding process. Further, when the number of linear motors required for the pressure maintaining process is smaller than the number of linear motors required for the filling process, the driving of one of the linear motors driven in the filling process is stopped.

When the pressure holding process is completed (step S1
5) Stop driving the linear motor to complete the injection process.

As described above, according to the present embodiment, by selecting the linear motor required for the filling step and the pressure holding step among the plurality of linear motors LM1 to LM4 based on the propulsive force, the minimum required Only a number of linear motors can be used. As a result, it is not necessary to drive all the linear motors at all times, and it is possible to save power. Further, according to the present embodiment, since only the minimum number of linear motors required for the filling process and the pressure holding process are used, when the injection screw 53 requires only a relatively small propulsive force, It is possible to precisely control the propulsive force without the resolution of the propulsive force becoming coarse. Further, according to this embodiment, when a new linear motor is added at the time of switching from the filling process to the pressure holding process, or when the driving of the extra linear motor is stopped, each linear motor LM1 is
Since ~ LM4 is controlled based on the same linear scale 90, addition or deletion of a linear motor accompanying switching from the filling process to the pressure holding process can be performed relatively smoothly.

The present invention is not limited to the above embodiments. In the above-described second embodiment, the maximum propulsive force required for the filling process and the pressure holding process is automatically determined, but it may be configured to be input by the operator before injection, for example.

[0062]

According to the present invention, it is possible to simplify the structure of a control system for driving a plurality of linear motors in an injection device in which an injection screw is directly driven by a plurality of linear motors. Further, according to the present invention, in an injection device in which the injection screw is directly driven by a plurality of linear motors,
It enables power saving and precise control of the propulsion force of the injection screw.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a basic configuration of an injection molding machine to which an injection device of the present invention is applied.

FIG. 2 is a cross-sectional view showing the structure of a drive unit 60.

3 is a cross-sectional view of the drive unit 60 shown in FIG. 2 taken along the line AA.

FIG. 4 is a diagram showing a hardware configuration of a control system that drives linear motors LM1 to LM4 of an injection device 40.

FIG. 5 is a functional block diagram showing an example of a configuration of a control system of drivers 105 to 108.

FIG. 6 is a graph for explaining a filling step and a pressure holding step.

FIG. 7 is a flowchart showing an example of a processing procedure of the control device 100 before performing injection control.

FIG. 8 is a flowchart showing an example of a processing procedure at the time of injection control.

[Explanation of symbols]

1 ... Injection molding machine 2 ... Base 3 ... Mold clamping device 4 ... Support board 5 ... Moving board 6 ... Fixed board 7 ... Tie bar 8 ... Toggle mechanism 80 ... Moving mold 81 ... Fixed mold 40 ... Injection device 51 ... Nozzle 50 ... Heating barrel 53 ... Injection screw 46 ... Metering motor 56 ... Hopper 60 ... Drive unit LM1 to LM4 ... Linear motor 90 ... Linear scale 100 ... Control device 120 ... Load cell

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuyoshi Kido             2068 Ooka, Numazu City, Shizuoka Prefecture Toshiba Machine Co., Ltd.             In the company (72) Inventor Harumichi Tokuyama             2068 Ooka, Numazu City, Shizuoka Prefecture Toshiba Machine Co., Ltd.             In the company F-term (reference) 4F206 AP062 AR012 AR024 AR092                       JA07 JL02 JM04 JT02 JT03                       JT21 JT32 JT37 JT40

Claims (2)

[Claims] 1. An injection device of an injection molding machine for injecting and filling a molding material into a mold, comprising: a heating barrel having a nozzle at its tip; and a heating accumulation inserted in the heating barrel and accumulated in the heating barrel. An injection screw for ejecting the formed molding material from the nozzle by moving forward, a plurality of electrically independent linear motors connected in common with the injection screw and moving the injection screw forward and backward, the injection screw and the An injection device comprising: a single linear scale that detects the positions of a plurality of linear motors; and control means that drives the plurality of linear motors based on position information detected by the linear scales. 2. The minimum linear motor required to satisfy the propulsive force of the injection screw, which is necessary for filling the mold with the molding material and maintaining the pressure, among the plurality of linear motors. 2. The injection apparatus according to claim 1, wherein is selected to drive and control only the selected linear motor.