JP2015205474A - Clamping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a plurality of servo motors and move a moving mold while maintaining a posture.
[Configuration] A plurality of ram shafts are attached to a moving mold of a mold clamping device, a servo motor is provided for each ram shaft, and the plurality of servo motors move the moving mold so as to contact a fixed mold. A distance sensor for measuring the distance between the moving mold and the fixed mold is provided for each ram axis, eliminating errors between the target position of the moving mold and the actual position of the moving mold along the ram axis. Thus, the first control amount common to the plurality of servo motors is generated. A second control amount for each servo motor is generated so as to eliminate the inclination of the moving mold with respect to the ram shaft, and the first control amount and the second control amount for each sensor are added to obtain a servo. A control amount for each motor is generated.
[Selection] Figure 2

Description

  The present invention relates to a mold clamping device such as a press molding device, an injection molding device, and a die cast molding device, and more particularly to a mold clamping device including a plurality of servo motors.

  The inventor examined keeping the bottom surface of the upper mold horizontal with respect to the mold clamping device that drives the ram shaft by a plurality of servo motors. If there are a plurality of servo motors, it is necessary to use a plurality of sensors, and there is a problem of what signals are measured by the sensors and how the signals are combined.

  Related prior art is shown. Patent Document 1 (JP2006-75864A) describes that, with respect to a four-axis mold clamping device, four servo motors are controlled by respective encoders, and a delay relative to other axes is corrected. However, since a ram shaft or the like is interposed between the servo motor and the mold, there is an error between the encoder signal and the height of the mold bottom. If control is performed so as to eliminate the delay, other servo motors are controlled in accordance with the servo motor that is most advanced, and the load on the other servo motors that are delayed increases.

  In Patent Document 2 (JP2007-283332A), the height of the upper mold is monitored by a linear sensor and fed back to a servo motor. However, the monitoring position is the base of the upper mold or the ram shaft. The distance between this position and the bottom surface of the upper mold is not constant because it is affected by thermal deformation of the mold.

JP2006-75864A JP2007-283332A

  An object of the present invention is to use a plurality of servo motors and move a moving mold while maintaining a posture.

The present invention provides a mold clamping device in which a plurality of ram shafts are attached to a movable mold, a servo motor is provided for each ram axis, and the movable mold is moved by the plurality of servo motors so as to contact the fixed mold.
A plurality of distance sensors for measuring the distance between the moving mold and the fixed mold are provided in the same number as the number of ram shafts.
From the signals of multiple interval sensors,
In order to eliminate the error between the target position of the moving mold and the actual position of the moving mold along the ram axis, a first control amount common to the plurality of servo motors is generated,
In order to eliminate the inclination of the moving mold with respect to the ram axis, a second control amount for each servo motor is generated,
In addition, control means for generating a control amount for each servo motor by adding the first control amount and the second control amount for each sensor is provided.

  The actual position of the moving mold is, for example, the center position of the moving mold, and the distance sensor measures the distance between the moving mold and the fixed mold. The position of the encoder or moving mold is fixed using the fixed mold. It does not include sensors that measure without being. The first control amount is obtained by, for example, solving the equation of the contact surface of the moving mold with the fixed mold, and more simply, from the average value of the signals of a plurality of distance sensors, the moving mold along the ram axis. Find and generate the actual position of the mold. The second control amount is generated, for example, by calculating the inclination of the moving mold with respect to the ram axis from the equation of the contact surface with respect to the moving mold, and more easily eliminating the variation in the signals of the plurality of interval sensors. Let A control amount for each servo motor is obtained by adding the second control amount to the first control amount. Thus, the moving mold can be moved according to the transition of the target position while maintaining the posture of the moving mold, that is, while keeping the contact surface of the moving mold perpendicular to the ram axis.

Preferably, the control means is
A first control amount is generated so as to eliminate an error between a target position of the moving mold along the ram axis and an average value of intervals obtained by a plurality of interval sensors;
The second control amount is generated so as to eliminate the deviation between the average value and the interval obtained by the individual interval sensor.

  The average value of the interval obtained by the interval sensor indicates the center position of the contact surface in the moving mold. Therefore, by comparing this value with the target position, a first control amount for making the position of the moving mold coincide with the target position can be obtained. Further, when the second control amount is generated so as to eliminate the deviation from the average value, that is, the deviation of the measured value of the interval between the interval sensors, the posture of the moving mold can be maintained.

  The average value for generating the first control amount is not limited to the simple average, but may be a weighted average, the position of the center of the moving mold obtained from the signal of the interval sensor, or the like. The deviation for generating the second control amount is not limited to the deviation from the average value, and may be a deviation between signals of the interval sensor.

Preferably, the interval sensor includes a magnetic rod having a magnetic mark and capable of moving back and forth, a sensor head for measuring a forward / backward position of the magnetic rod, a stopper for determining a movement limit of the magnetic rod, and the magnetic rod on the stopper side. A linear sensor having an elastic body biased toward the
A contact member for moving the magnetic rod in contact with the magnetic rod;
The linear sensor is attached to one of the movable mold and the fixed mold, and the contact member is attached to the other of the movable mold and the fixed mold so as to face each other.

  In this way, the distance between the moving mold and the fixed mold can be accurately measured, and a linear sensor having a short measurement range but high resolution can be used.

Preferably, a long range linear sensor for measuring the position of the moving mold without depending on the fixed mold, or an encoder for each servo motor is further provided.
The distance sensor can be measured with the distance between the moving mold and the fixed mold below a predetermined value.
If the distance between the moving mold and the fixed mold exceeds the specified value, control the multiple servo motors with a long-range linear sensor or encoder. If the distance between the moving mold and the fixed mold is less than the specified value The control of the plurality of servo motors is switched from the control by the long range linear sensor or the encoder to the control by the plurality of interval sensors while continuously changing the control weight by the interval sensor. For example, only one long-range linear sensor may be provided.

  In this way, control is performed by a long range linear sensor or encoder until the moving mold approaches the fixed mold, and when the moving mold approaches the fixed mold, the control can be switched to the interval sensor. Further, the control can be switched continuously and smoothly. In particular, even if the signals do not match between the encoder or the long-range linear sensor and the interval sensor, an excessive control amount does not occur.

  Particularly preferably, before the moving mold comes into contact with the fixed mold, the target position of the moving mold is temporarily fixed and the control by the second control amount is continued. Therefore, before the moving mold contacts the fixed mold, the contact surface of the moving mold is surely perpendicular to the ram axis. Next, the target position of the moving mold is changed so that the moving mold contacts the fixed mold. For example, the mold clamping device is an injection molding device, and when the target position of the moving mold is once fixed, resin filling is started. In this way, molding by the compression molding method can be performed accurately.

Block diagram showing an injection molding apparatus of an embodiment Bottom view showing the bottom surface of the upper mold in the embodiment The figure which shows attachment of the linear sensor in an Example Cross section of the linear sensor in the embodiment Block diagram showing the control system of the servo motor in the embodiment In the waveform diagram of the example, 1) shows the weight of the encoder signal and the linear sensor signal, and 2) shows the angular velocity of the motor. The flowchart which shows the control algorithm of the servomotor in an Example

  In the following, an optimum embodiment for carrying out the present invention will be shown. The scope of the present invention should be determined according to the understanding of those skilled in the art based on the description of the scope of the claims, taking into account the description of the specification and well-known techniques in this field.

  1 to 7 show an embodiment and its operation. FIG. 1 shows an injection molding apparatus 2 according to an embodiment. An upper mold (moving mold) 4 is a mold that moves up and down by, for example, four ram shafts (divers) 12, and injects a synthetic resin by injection molding. The internal mold 8 is set. An inner mold 10 for injecting synthetic resin is set in the lower mold (fixed mold) 6. The upper mold 4 is guided by, for example, four guide pins 11 and moves up and down via the four ram shafts 12 by the four crank mechanisms 14 and the four servo motors M1 to M4. The lower mold 6 is connected to an injection device 18 having a screw pump, a plunger, and the like, and injects synthetic resin into the chamber between the molds 8 and 10. In addition, except the injection device 18, it may be a press molding device, and may be a die-cast molding device. Instead of the crank mechanism 14, a toggle mechanism or the like may be used, or the crank mechanism 14 or the like may be omitted and the servo motors M1 to M4 may be driven by a ball screw. Further, the movable mold 4 may be moved horizontally toward the fixed mold 6 by the ram shaft 12.

  The control unit 20 feedback-controls the servo motors M1 to M4 with signals from the encoder and linear sensors (interval sensors) S1 to S4. Linear sensors S <b> 1 to S <b> 4 are fixed to the upper part of the lower mold 6, and the distance from the reference plate (contact member) 24 fixed to the lower part of the upper mold 4 is measured. A combination of the linear sensors S1 to S4 and the reference plate 24 is provided for each of the servo motors M1 to M4. In the embodiment, one set is provided on each of the four circumferences of the molds 4 and 6. The linear sensors S1 to S4 and the reference plate 24 are fixed near the opposing portions of the molds 4 and 6, and the actual distance between the molds 4 and 6 is measured by the linear sensors S1 to S4.

  FIG. 2 shows the bottom surface of the upper mold 4, O is the center of the upper mold 4, guide pins 11 are provided in four directions, and a reference plate 24 is attached to the side surface of the upper mold 4. Signals from the linear sensors corresponding to the respective reference plates 24 are a to d.

  FIG. 3 shows the arrangement and the like of the linear sensors S1 to S4. The reference plate 24 and the linear sensors S1 to S4 are arranged in the vicinity of the facing portions of the molds 4 and 6. The linear sensors S1 to S4 may be disposed on the upper mold 4 side, and the reference plate 24 may be disposed on the lower mold 6 side.

  FIG. 4 shows a cross section of the linear sensor 50. Reference numeral 42 denotes a metal case. The movable magnetic rod 44 is provided with a magnetic mark composed of a magnetic body 52 and a nonmagnetic body 53, and includes a plurality of coils. 48 is penetrated. A sliding member 54 that slides along the groove 57 of the case 51 and the magnetic rod 44 are fixed to the reference plate 45, and the reference plate 45, the magnetic rod 44, and the sliding member 54 are integrated into the left and right of FIG. Slide to.

  The magnetic rod 44 and the sliding member 54 are connected by a connecting member 55 and are urged toward the reference plate 45 side on the left side of the drawing by an elastic body 49. Until the reference plate 45 is pressed from the upper mold 4 side, the connecting member 55 is positioned by the stopper 56 because of the urging by the elastic body 49. The stroke (measurement range) of the magnetic rod 44 is, for example, about 10 mm. The linear sensors S1 to S4 are calibrated such that the height is 0 when the upper and lower molds 4 and 6 are in contact with each other.

  The linear sensors S1 to S4 also have a measurement range on the minus side of the mold clamping position, but the upper mold 4 stops at the mold clamping position, so the minus range is not measured. In a section in which the position of the upper mold 4 cannot be detected by the linear sensors S1 to S4, the servo motor M1 is transmitted by the encoder signals E1 to E4 or the signal of a long range linear sensor (not shown) for monitoring the position of the ram shaft 12. Control M4.

  FIG. 5 shows a control system for the servo motors M1 to M4. An adder 30 multiplies the signals from the encoders E1 to E4 by a weight, and multiplies the signals a to d from the linear sensors S1 to S4 by a weight (1-w) and adds them. The signals from the four adders 30 are input to the adder 32 and the average value is output. This is the height of the center O of the bottom surface of the upper mold 4. In the subtractor 34, the difference between the target height and the height of the center O obtained by the adder 32 is obtained, and this is used as the first control amount. Note that the average value obtained by the adder 32 is not limited to a simple average, and can be obtained from four sensors and appropriate as the height of the center O, for example, a weighted average of signals of four sensors. Good.

  The deviation between the height of the center O and the signals a to d of the individual linear sensors S1 to S4 represents the inclination of the bottom surface of the upper mold 4 from the horizontal plane. Therefore, when the second control amount is generated by the subtractor 36 so as to eliminate this change, and the first control amount and the second control amount are added by the adder 38, the control amounts of the servo motors M1 to M4 are obtained. It is done. Preferably, the gain for the second control amount is made larger than the gain for the first control amount, and the bottom of the upper mold 4 is kept horizontal, and the height of the upper mold matches the target height. Takes precedence over.

  The servo mechanism 40 controls the servo motors M1 to M4 using the control amount input from the adder 38 as the position control amount and the rate of change of the signals of the encoders E1 to E4 as the speed loop control amount.

  Instead of using the height of the center O of the upper mold 4 and the deviation from the height of the center O, the equation of the bottom surface of the upper mold 4 is obtained, the inclination of the bottom surface is eliminated, and the center O is in a predetermined pattern. You may control so that it may descend | fall. Since there are four sensors in the embodiment, the plane equation can be obtained more accurately than in the case of three sensors. However, the control is almost the same whether the equation of the bottom surface is used or the height of the center O and the deviation from the height of the center O are used.

  FIG. 6 shows the weight w and the average angular velocity of the four servo motors. In a range where the distance between the upper mold 4 and the lower mold 6 cannot be measured by the linear sensors S1 to S4, the weight w to the signal of the encoders E1 to E4 or the long range linear sensor is 1, and the signal from the linear sensors S1 to S4 When w is obtained, w is gradually brought closer to 0, and control from the encoders E1 to E4 or the long-range linear sensor is switched to control by the linear sensors S1 to S4.

  When the distance between the upper and lower molds 4 and 6 reaches a predetermined value such as 100 μm, the target height is temporarily fixed. At this time, the control by the second control amount for leveling the bottom surface of the upper mold 4 is continued by setting the signal deviation between the linear sensors S1 to S4 to zero. Then, while the target height is fixed, resin filling (injection) is started, and air is expelled from the chamber between the molds 8 and 10. As a result, even in a thin chamber, air can be surely expelled. While continuing the resin filling, the upper mold is further lowered until the target height becomes 0 (the upper and lower molds 4 and 6 are in contact). During this time, if a predetermined amount of resin is filled, the filling is stopped. In this way, the upper mold 4 can be lowered while keeping the bottom surface horizontal.

  FIG. 7 shows control by the linear sensors S1 to S4. In step 71, the average value f of the signals of the four linear sensors is obtained. In step 72, control signals g1 to g4 are generated so as to eliminate the deviation from the average value f. In step 73, a control signal h is generated so as to eliminate an error between the target height z and the signal f. In step 74, the servo motor M1 is controlled by (h + g1), the servo motor M2 is controlled by (h + g2), the servo motor M3 is controlled by (h + g3), and the servo motor M4 is controlled by (h + g4). The speed loop of each servo motor is controlled by the signals from the encoders E1 to E4 (step 75).

2 Injection molding equipment 4 Upper mold (moving mold)
6 Lower mold (fixed mold)
8, 10 Internal mold 11 Guide pin 12 Ram shaft 14 Crank mechanism 18 Injection device 20 Control unit (control means)
24 Reference plate (contact member)
30, 32, 38 Adder 36 Differentiator 40 Servo mechanism 42 Case 44 Magnetic rod 45 Reference rods 46 and 47 of magnetic rod Reference surface 48 Sensor head 49 Elastic body 54 Sliding member 55 Connecting member 56 Stopper 57 Groove

O Center a to d Sensor signal E1 to E4 Encoder M1 to M4 Servo motor S1 to S4 Linear sensor (Spacing sensor)

Claims (6)

In a mold clamping device in which a plurality of ram shafts are attached to a moving mold, a servo motor is provided for each ram shaft, and the moving mold is moved to come into contact with a fixed mold by a plurality of servo motors.
A plurality of distance sensors for measuring the distance between the moving mold and the fixed mold are provided in the same number as the number of ram shafts.
From the signals of multiple interval sensors,
In order to eliminate the error between the target position of the moving mold and the actual position of the moving mold along the ram axis, a first control amount common to the plurality of servo motors is generated,
A second control amount for each servo motor is generated so as to eliminate the inclination of the moving mold with respect to the ram axis,
A mold clamping apparatus comprising: a control unit that generates a control amount for each servo motor by adding the first control amount and the second control amount for each sensor. The control means
A first control amount is generated so as to eliminate an error between a target position of the moving mold along the ram axis and an average value of intervals obtained by a plurality of interval sensors;
2. The mold clamping device according to claim 1, wherein the second control amount is generated so as to eliminate a deviation between the average value and an interval obtained by an individual interval sensor. The distance sensor includes a magnetic rod having a magnetic mark, which is movable back and forth, a sensor head that measures the advancing / retreating position of the magnetic rod, a stopper that determines the movement limit of the magnetic rod, and the magnetic rod to the stopper side. A linear sensor having an urging elastic body;
A contact member that contacts the magnetic rod and moves the magnetic rod;
The linear sensor is attached to one of the movable mold and the fixed mold, and the contact member is attached to the other of the movable mold and the fixed mold so as to face each other. 2 mold clamping device. A long-range linear sensor that measures the position of the moving mold without depending on the fixed mold, or an encoder for each servo motor is further provided.
The distance sensor can freely measure the distance between the moving mold and the fixed mold below a predetermined value,
When the distance between the moving mold and the fixed mold exceeds a predetermined value, the control means controls a plurality of servo motors with a long-range linear sensor or encoder so that the distance between the moving mold and the fixed mold is predetermined. If the value is less than or equal to the value, it is configured to switch the control of multiple servo motors while continuously changing the control weight of the interval sensor from the control by the long range linear sensor or encoder to the control by the multiple interval sensors. The mold clamping device according to any one of claims 1 to 3, wherein the mold clamping device is provided.   The control means temporarily fixes the target position of the moving mold before the moving mold contacts the fixed mold and continues the control by the second control amount, and then the moving mold becomes the fixed mold. The mold clamping device according to any one of claims 1 to 4, wherein the mold clamping device is configured to change a target position of the moving mold so as to come into contact with each other.   6. The mold clamping apparatus according to claim 5, wherein the mold clamping apparatus is an injection molding apparatus, and is configured to start filling of the resin once the target position of the movable mold is fixed.

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