JP3313666B2 - Method and apparatus for detecting back pressure of injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a back pressure of an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, a screw or a round bar has moved,
A method of detecting the applied pressure by capturing the strain is known, for example, from Japanese Patent Application Laid-Open No. 54-145081. There, in order to increase the output, the structure to be deformed is made annular. Further, after that, in the detection of the injection pressure and the back pressure applied to the injection molding machine, there is a type in which the deformation of the cantilever is detected as a distortion and the distortion is output.

[0003]

Generally, in a hydraulic injection molding machine, a pressure control valve is dedicated to accurately control the back pressure, but the pressure is directly detected to detect the pressure. However, since the same strain sensor is used to detect the injection pressure, which has a large working range, and the back pressure in the weighing process, which normally has a working range of 1/10 or less, the same strain sensor is used. There is a problem that the detection accuracy is reduced due to the influence.

The present invention eliminates the above-mentioned problems, and directly detects a back pressure, which is a minute control range, as compared with the injection pressure setting control range, without using a hydraulic pressure or the like. Adapted to the use range of back pressure in the weighing process,
Further, it is an object of the present invention to provide a method and an apparatus for detecting a back pressure of an injection molding machine capable of increasing output with respect to applied pressure, reducing electrical amplification factor, increasing accuracy, and improving noise resistance. And

[0005]

According to the present invention, there is provided a method for detecting a back pressure of an injection molding machine, comprising the steps of: , And control in the injection / pressure -holding step is performed based on pressure detection information from the second sensor.

[2] In the back pressure detecting method for an injection molding machine according to the above [1], the first sensor has a spring member against a retreating force of the screw, and when the maximum retreating force of the screw is generated in the measuring step. A stopper for preventing plastic deformation of the spring member acts.

[3] In the back pressure detecting method for an injection molding machine according to the above [1], a minute distance sensor for detecting an amount of displacement of the spring member caused by a retreating force of a screw is used as the first sensor. It was made.

[4] In the back pressure detecting device of the injection molding machine, a first sensor for obtaining pressure detection information for performing back pressure control in the measuring process, and a control in the injection / pressure keeping process. And a second sensor for obtaining pressure detection information to be performed.

[5] In the back pressure detecting device for an injection molding machine according to the above [4], the first sensor has a spring member arranged to resist a retreating force of the screw, and The spring member is provided with a stopper for preventing plastic deformation of the spring member when a maximum retreat force is generated.

[6] In the back pressure detecting device for an injection molding machine according to the above [4], the first sensor is a minute distance sensor for detecting an amount of displacement of the spring member caused by a screw retreating force.

[7] In the back pressure detecting device for an injection molding machine according to the above [6], the minute distance sensor is a gap sensor.

[8] In the back pressure detecting device for an injection molding machine according to the above [4], the first sensor is a strain sensor for detecting a strain amount of the spring member caused by a screw retreating force.

[0013]

[9] In the back pressure detecting device for an injection molding machine according to the above [8], the strain sensor is a strain gauge stretched on a leaf spring capable of expanding a retreating force of the screw.

[10] The back pressure detecting device for an injection molding machine according to the above [4], wherein a stopper mechanism is arranged near the first sensor.

[11] The back pressure detecting device for an injection molding machine according to the above [4], wherein the first sensor detects a displacement of the spring member caused by a retreating force of a ball screw shaft. It is.

[12] In the back pressure detecting device for an injection molding machine according to the above [11], the first sensor is arranged at a rear end of the ball screw shaft.

[0017]

Embodiments of the present invention will be described below in detail.

FIG. 1 is a block diagram of a control system for an injection molding machine showing an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the injection molding machine, and FIG. 3 is a diagram showing the principle of back pressure detection.

In FIG. 1, an injection servomotor 10 rotates a ball screw 12 connected to the servomotor 10. A nut 13 is screwed into the ball screw 12, and the nut 13 can be moved forward and backward by rotating the ball screw 12. Nut 1
3 is fixed to a pusher plate 14, and the pusher plate 14 is provided movably along guide bars 15, 16 fixed to a frame (not shown). The forward / backward movement of the pusher plate 14 is transmitted to the screw 20 via the first sensor 18 and the bearing 17. Here, 19 is a second sensor attached to the pusher plate 14, and 21 is a heating cylinder. Reference numeral 1 denotes a measuring servomotor for rotating the screw 20, and reference numeral 25 denotes a position detector for detecting the position of the pusher plate 14.

Reference numeral 22 denotes an amplifier for amplifying a detection signal from the first sensor 18, and reference numeral 23 denotes a position detector 25.
Is an amplifier for amplifying the detection signal from the second sensor 19. The respective detection signals are input to the controller 27. The controller 27 outputs a current (torque) command corresponding to each process to the servo amplifier 24 according to the setting of the operator, and the servo amplifier 24 controls the drive current of the injection servomotor 10 to control the injection servomotor. 10, the output torque is controlled.

Further, as shown in FIG. 3, in this embodiment, since the resin supply of the screw is restricted by a mechanism that is fed by frictional force, the retreat pressure during the measurement increases only up to about 150 atm. This is a setting control range that is smaller than the injection pressure. As a practical range, the back pressure region at the time of weighing up to about 20 to 150 atm (hereinafter referred to as a weighing mode region) is detected by the first sensor 18 having high accuracy, and the back pressure at the time of weighing is controlled. Member 18D at the maximum screw retraction force
A mechanical stopper for preventing plastic deformation of the metal is applied, and the subsequent injection pressure / holding pressure (for example, 150
(3000 atm) is detected by switching to the second sensor 19 to control the injection pressure / pressure holding area (hereinafter, injection mode area). In FIG. 3, S ₁ indicates the back pressure set value, and S ₂ indicates the action point of the mechanical stopper.

Hereinafter, the operation of the control system of the injection molding machine will be described with reference to FIGS.

(1) First, information from various sensors (not shown) arranged in each part of the injection molding machine is taken into the controller 27. That is, screw position information from the position detector 25, although not shown, a resin temperature from a resin temperature sensor, a mold temperature from a mold temperature sensor, a resin pressure in a mold from a resin pressure sensor in a mold, and the like. Import (step S1).

(2) Next, based on information from various sensors,
The controller 27 determines whether or not the process is a weighing process (step S2).

(3) Next, in the case of the weighing step, information from the first sensor 18 is taken into the controller 27 (step S3).

(4) Then, based on the information from the first sensor 18, the controller 27 controls the back pressure in the measuring step (step S4). Note that this first sensor 1
In FIG. 8, fine detection is possible as shown in FIG.

(5) Next, the controller 27 determines whether or not the weighing process has been completed based on a time signal from a position sensor or a timer (step S5).

(6) Next, when the measuring step is completed, the second
The information from the sensor 19 is taken into the controller 27 (step S6). Note that the second sensor 19 performs coarser detection than the first sensor 18, and can cover detection in a wide pressure range.

(7) Then, the controller 27 controls the injection / pressure keeping process based on the information from the second sensor 19 (step S7).

FIG. 4 is a configuration diagram of a first sensor and a second sensor according to a first embodiment of the present invention.

In this embodiment, a gap sensor as a minute distance sensor capable of detecting a minute displacement of a leaf spring 18D as a spring member caused by the retreating force of the screw 20 is used as a second sensor for controlling the back pressure in the measurement mode area. Used as one sensor.

That is, as shown in FIG. 4, the first sensor 18 is provided between the bearing 17 and the pusher plate 14 and has a spring member 18D formed in a deep dish shape.
A gap sensor element 18A provided between the spring member 18D and the pusher plate 14, and a stopper surface 1 provided adjacent to the gap sensor element 18A.
8C comprises a mechanical stopper 18B provided opposite to the bottom surface of the spring member 18D.

The mechanical stopper 18B is formed so that the gap between the spring member 18D and the mechanical stopper 18B is smaller than the gap between the spring member 18D and the gap sensor element 18A.

Therefore, the displacement of the spring member 18D caused by the retreating force of the screw 20 is detected by the gap sensor element 18A as the first sensor 18 (a minute distance sensor). 18B is a mechanical stopper for stopping the end face when the screw 20 moves backward, and 18C is a stopper face.
In addition, as the minute distance sensor, an optical sensor using a laser, an eddy current sensor, a magnetic sensor, or the like can be employed in addition to the gap sensor, and a change in a minute dimension of 0.2 μm can be detected. .

The second sensor 19 for performing normal injection / holding pressure control includes a pusher plate 14.
Attach a strain gauge to the pusher plate 14
You can see the distortion. Further, other various sensors may be used.

Here, assuming that the back pressure is F, the displacement of the spring member is (L ₀ -L), and the spring constant is k, F = k · (L ₀ -L).

With this configuration, the back pressure control in the weighing mode area is performed based on the information from the first sensor 18, and the subsequent injection / pressure control is performed based on the information from the second sensor 19. Done.

FIG. 5 is a configuration diagram of a first sensor and a second sensor according to a second embodiment of the present invention.

In this embodiment, a strain sensor (strain gauge) mechanically devised so as to detect a minute displacement of the spring member caused by the retreating force of the screw is used to control the back pressure in the measurement mode area. Used as a sensor.

That is, as shown in FIG.
0, the minute displacement of the spring member 18E due to the retreat force is a leaf spring 18 as a spring member as the first sensor 18.
E can be detected by a strain gauge 18F attached to E. Reference numeral 18G is a mechanical stopper for preventing the plastic deformation of the spring member when the screw maximum retreat force occurs in the measuring step.

The second sensor 19 for performing normal injection / holding pressure control includes a pusher plate 14.
A strain gauge 19A can be attached to the pusher plate 14 so that the strain of the pusher plate 14 can be observed. Also,
It may be used in other various sensors.

With this configuration, the back pressure control in the weighing mode area is performed based on the information from the first sensor 18, and the subsequent injection and pressure control is performed based on the information from the second sensor 19. Done.

Hereinafter, specific control of the injection molding machine will be described.

FIG. 6 is a block diagram of a drive unit of an injection molding machine showing a specific example of the present invention.

As shown in this figure, a servomotor 101 for measurement is arranged at the front part of the drive unit case A, and a servomotor 110 for injection is arranged at the rear part at the same axis. The measuring servomotor 101 includes a stator 102 fixed to the front frame B, and a rotor 103 disposed on the inner peripheral side of the stator 102. The injection servomotor 110 is a stator 11 fixed to the rear frame C.
1 and a rotor 112 disposed on the inner peripheral side of the stator 111.

The rotor 103 is rotatably supported by the drive unit case A, and a hollow first rotor shaft 104 is fitted and fixed to the rotor 103, and the first rotor shaft 104 is driven via a bearing. It is supported by the case A. A spline nut 105 is fixed to the inner periphery of the front end of the first rotor shaft 104, the spline nut 105 and the spline shaft 106 are spline-connected, and a screw (not shown) is fixed to the front end of the spline shaft 106.

Therefore, the rotation of the rotor 103 is transmitted to the screw via the first rotor shaft 104, the spline nut 105, and the spline shaft 106. Further, since the spline nut 105 and the spline shaft 106 are spline-connected, the spline shaft 106 can be retreated relatively to the spline nut 105.

An annular bearing retainer 114 is fixed to the rear end of the second rotor shaft 113, and a ball screw shaft 115 is fitted and fixed to the inner periphery of the bearing retainer 114. The ball screw shaft 115 is rotatably supported by the drive unit case A. That is, the ball screw shaft 115 is supported by the bearing via the annular bearing retainer 114.

On the other hand, the rotor 112 is also a driving case A
, And a hollow second rotor shaft 113 is fitted and fixed to the rotor 112, and the second rotor shaft 113 is attached to the annular bearing retainer 1.
14, and is supported by the drive unit case A.

A ball nut 116 is provided inside the second rotor shaft 113 so as to be able to advance and retreat, and is screwed with a ball screw shaft 115. Therefore, the rotation of the rotor 112 is transmitted to the ball screw shaft 115 via the second rotor shaft 113 and the annular bearing retainer 114 to move the ball nut 116 forward and backward. At this time, the spline shaft 109 is fixed to the front end of the ball nut 116 so that the ball nut 116 does not rotate together with the ball screw shaft 115, and the spline nut 121 and the spline shaft 109 fixed to the center support D are splined. Be linked.

A bearing box 107 is fixed to the front end of the spline shaft 109. A thrust bearing 108 is provided in front of the bearing box 107, and a bearing 117 is provided in the rear. Therefore, the spline shaft 106 is rotatably supported by the spline shaft 109 and the ball nut 116 by the thrust bearing 108 and the bearing 117.

The rear end of the ball screw shaft 115 has a first bearing via a bearing 121 as shown in FIG. 4 or FIG.
Sensors 118 are arranged. In other words, a minute distance sensor (a gap sensor, an optical sensor using a laser, an eddy current sensor) that detects the amount of displacement of the spring member due to the retreating force of the ball screw shaft caused by the retreating force of the screw, and the amount of strain of the spring member Can be used.

In the vicinity of the first sensor 118, although not shown here, a mechanism for preventing plastic deformation of the spring member when a maximum screw retreat force occurs in the measuring step as shown in FIG. 4 or FIG. A strategic stopper is arranged.

Further, behind or near the first sensor 118, the ball screw shaft 11 as shown in FIG.
5 can be used for control in the injection / pressure-holding mode region by arranging a second sensor 119 capable of detecting the retreating force.

Further, at the rear end of the ball screw shaft 115, an absolute value pulse encoder 120 for measuring the position of the ball screw shaft 115 is arranged.

With this configuration, in the measuring step, when a current is supplied to the stator 102 of the measuring servomotor 101, the rotor 103 is rotated, and the rotation of the rotor 103 is controlled by the first rotor shaft 104 and the spline nut 105. Is transmitted to the spline shaft 106 via the. The rotation of the spline shaft 106 is transmitted to the screw, and the screw can be retracted while rotating. At this time, the injection servomotor 110 rotates the screw in the backward direction while controlling the back pressure of the measured resin.

In the injection step, when a current is supplied to the stator 111 of the injection servomotor 110, the rotor 112 is rotated, and the rotation of the rotor 112
Rotor shaft 113 and annular bearing retainer 1
The power is transmitted to the ball screw shaft 115 via the control unit 14. The rotation of the ball screw shaft 115 generates a thrust on the ball nut 116, and the ball nut 116 moves forward. At this time, the weighing servomotor 101 is not operated,
The rotor 103 is in a stopped state. Therefore, the spline shaft 106 disposed in front of the ball nut 116 is advanced without rotating, and advances the screw. As a result, the resin stored in front of the screw can be injected from an injection nozzle (not shown).

Further, as shown in each of the above embodiments, the first
Since the stopper mechanism is arranged near the sensor, a compact configuration can be achieved.

FIG. 7 is a block diagram of a drive unit of an injection molding machine showing another embodiment of the present invention.

In this embodiment, the bearing retainer 11 is provided behind the annular bearing retainer 114.
4, a spring member (not shown, see 18D and 18E in FIGS. 4 and 5) which is displaced by a retreating force, and a first sensor 201 for detecting a displacement amount of the spring member are arranged. Further, a second sensor 202 is arranged behind or near the spring member. In principle, the structure as shown in FIGS. 4 and 5 is changed to a tubular shape. That is, the ball screw shaft 11 is located at the center.
It is necessary to secure a space for penetrating through 5.
In other respects, it is the same as shown in FIG.
The same reference numerals are given and their description is omitted.

With this configuration, it is possible to configure a compact built-in injection molding machine in which the first and second sensors are completely incorporated in the injection molding machine.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0063]

As described above, according to the present invention, the following effects can be obtained.

(A) In comparison with the injection pressure setting control range,
The back pressure in the weighing process, which is a minute setting control range, is directly detected by a dedicated first sensor without using an oil pressure or the like, and the detection range is adapted to the use range of the back pressure in the weighing process, and The output with respect to the applied pressure is increased, the electrical amplification factor is reduced, the accuracy can be increased, and the noise resistance can be improved. In addition, in the injection / pressure keeping process, the second sensor performs coarser detection than the first sensor, and can cover a wide pressure range.

(B) Since the stopper for preventing the plastic deformation of the spring member is applied when the maximum screw retraction force occurs in the measuring step, the plastic deformation of the spring member can be prevented.

(C) Since the stopper mechanism is arranged near the first sensor, a compact configuration can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a control system of an injection molding machine showing an embodiment of the present invention.

FIG. 2 is an operation flowchart of the injection molding machine showing the embodiment of the present invention.

FIG. 3 is a diagram showing the principle of back pressure detection according to the present invention.

FIG. 4 is a configuration diagram of a first sensor and a second sensor according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram of a first sensor and a second sensor according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a drive unit of an injection molding machine showing a specific example of the present invention.

FIG. 7 is a configuration diagram of a drive unit of an injection molding machine showing another specific example of the present invention.

[Explanation of symbols]

1,101 Servo motor for measuring 10,110 Servo motor for injection 12 Ball screw 13 Nut 14 Pusher plate 15,16 Guide bar 17 Bearing 18 First sensor 18A, 118B for back pressure control in measuring process Gap sensor element 18B , 18G Mechanical stopper 18C Stopper surface 18D, 18E Leaf spring (spring member) 18F, 19A Strain gauge 19 Second pressure for pressure control in injection / pressure keeping process
Sensor 20 screw 21 heating cylinder 22, 23, 26 amplifier 24 servo amplifier 25 position detector 27 controller A drive unit case B front frame C rear frame D center support 102, 111 stator 103, 112 rotor 104 first rotor shaft 105, 121 Spline nut 106, 109 Spline shaft 107 Bearing box 108 Thrust bearing 113 Second rotor shaft 114 Annular bearing retainer 115 Ball screw shaft 116 Ball nut 117 Bearing 118, 201 First sensor 119, 202 Second sensor 120 Absolute value Pulse encoder

Claims (12)

(57) [Claims] 1. A method for detecting a back pressure of an injection molding machine, comprising the steps of: (a) controlling a back pressure in a weighing step from a first sensor;
Performed on the basis of the pressure detection information, (b) back pressure detecting method of an injection molding machine and performing control in an injection-pressure-holding step on the basis of the pressure detection information from the second sensor. 2. The back pressure detecting method for an injection molding machine according to claim 1, wherein the first sensor has a spring member that resists a retreating force of the screw, and the first sensor generates the maximum retreating force of the screw in a measuring step. A method for detecting a back pressure of an injection molding machine, wherein a stopper for preventing plastic deformation of a spring member is operated. 3. A back pressure detecting method for an injection molding machine according to claim 1, wherein a minute distance sensor for detecting a displacement amount of said spring member caused by a retreating force of a screw is used as said first sensor. Back-pressure detection method of an injection molding machine. 4. A back pressure detecting device for an injection molding machine, comprising: (a) a first sensor for obtaining pressure detection information for performing back pressure control in a measuring step; and (b) injection / holding pressure. Pressure detection for controlling the process
A back pressure detecting device for an injection molding machine, comprising: a second sensor for obtaining output information. 5. The back pressure detecting device for an injection molding machine according to claim 4, wherein the first sensor has a spring member arranged to oppose a retreating force of the screw, and a maximum retreat of the screw in the measuring step. A back pressure detecting device for an injection molding machine, comprising a stopper for preventing plastic deformation of the spring member when a force is generated. 6. A back pressure detecting device for an injection molding machine according to claim 4, wherein said first sensor is a minute distance sensor for detecting a displacement of said spring member caused by a screw retreating force. Back pressure detecting device of an injection molding machine. 7. The back pressure detecting device for an injection molding machine according to claim 6, wherein said minute distance sensor is a gap sensor. 8. The back pressure detecting device for an injection molding machine according to claim 4, wherein the first sensor is a strain sensor for detecting a strain amount of the spring member caused by a screw retreating force. Pressure detection device for injection molding machines. 9. A back pressure detecting device for an injection molding machine according to claim 8, wherein said strain sensor is a strain gauge stretched on a leaf spring capable of expanding a screw retreating force. Back pressure detector. 10. The back pressure detecting device for an injection molding machine according to claim 4, wherein a stopper mechanism is disposed near the first sensor. 11. A back pressure detecting device for an injection molding machine according to claim 4, wherein said first sensor detects a displacement of said spring member caused by a retreat force of a ball screw shaft. Back pressure detector for molding machines. 12. A back pressure detecting device for an injection molding machine according to claim 11, wherein said first sensor is disposed at a rear end of said ball screw shaft. .