JP5773223B2 - Mold clamping device and mold clamping method - Google Patents

Description

  The present invention relates to a mold clamping technique in press molding, injection molding, die casting molding, and the like, and particularly relates to monitoring or position control of a mold when opposed molds are closest.

  A linear sensor is known as a sensor for measuring the position of a moving body. In the linear sensor, a magnetic mark in which a magnetic body and a non-magnetic body are arranged or a magnetic mark in which magnets having different polarities are arranged is provided, and a sensor head having a plurality of coils is provided. When the position of the sensor head with respect to the magnetic mark changes, the magnetic interaction between the magnetic mark and the coil changes, so that the position of the sensor head with respect to the magnetic mark can be obtained.

  Even in a mold clamping apparatus using a mold such as a press molding apparatus, an injection molding apparatus, or a die cast molding apparatus, there is a demand for accurately monitoring or controlling a relative position between upper and lower or left and right molds. And in patent document 1 (JP2007-283332A), the position of the base part of an upper metal mold | die is monitored with a linear sensor, and it feeds back to the servomotor which drives an upper metal mold | die. However, the position to be monitored is the base of the upper mold or the position of the ram shaft which is a slide mechanism. The distance between this position and the lower end of the upper mold is not constant because it is affected by the stress associated with the contact between the upper and lower molds, thermal deformation of the mold, and the like. Therefore, even if the position of the upper mold is monitored by the crank mounting position or the ram shaft mounting position, etc., in order to accurately control the position of the upper mold relative to the lower mold, in other words, the distance between the upper and lower molds. Don't be.

  The inventors have further noted that linear sensors with a long measurement range generally have low resolution. It was also noted that what needs to be monitored and controlled is the behavior of the mold itself, and monitoring the position of the sliding mechanism only indirectly monitors the behavior of the mold. Therefore, the inventor studied switching the control between another sensor such as an encoder of a servo motor and a linear sensor directly attached to the mold using a linear sensor having a short measurement range. If the control is switched discontinuously between the other sensors and the linear sensor here, a slight difference in the detected value between the sensors is fed back to the control unit as a large control error, and the servo motor control becomes unstable. Become.

JP2007-283332A

The subject of this invention is
1) Measuring the relative position between opposing molds accurately and with high resolution by minimizing the effects of stress due to mold contact, temperature changes of the mold, etc., and
2) To switch the sensor to be used smoothly during the mold stroke.

The present invention relates to at least a pair of opposed molds, a servo motor that moves at least one of the molds via a ram shaft, and a long-range linear sensor that monitors the encoder signal of the servo motor or the position of the ram shaft. And a control unit that feedback-controls the servo motor as a control input, and is directly fixed to one mold in the vicinity of the opposed part of the mold, and the opposed mold or the opposed mold By contacting a reference plate attached to the mold, a mold mounting sensor consisting of an opposing mold or a linear sensor that measures a position with reference to the reference plate is provided, together are configured to monitor the spacing between the molds, and a signal of the linear sensor signal or long range of the encoder, gold A switching means is provided for continuously switching the control input between signals from the mounting sensor, and in the mold clamping region near the mold clamping position, the servo motor is controlled by the signal from the mold mounting sensor, and the mold clamping position Servo motors are controlled by the encoder signal or long-range linear sensor signal in the remote area away from the encoder, and the encoder signal or long-range linear sensor signal is in the intermediate area between the remote area and the mold clamping area. And the signal of the mold mounting sensor are configured to continuously switch the control input, and the switching means uses the variable weight w of 0 or more and 1 or less to change the encoder signal P1 or the ram shaft. The signal of the long range linear sensor that monitors the position of the sensor and the signal P2 of the mold mounting sensor are converted to the control input P3 by P3 = P1 ・ w + P2 ・ (1-w) When the mold is outside the measurement range of the mold mounting sensor, w = 1, and when the mold is closest, W = 0. When the mold enters the measurement range of the mold mounting sensor, the weight w starts from 1. The weight w is determined so as to continuously change to zero . Fixing directly to the mold means fixing to the outer periphery of the mold, fixing to the inside of the mold, and the like. The mold clamping device is, for example, an injection molding device, a press molding device, a die cast molding device, or the like. Instead of monitoring the rotation of the servomotor shaft with an encoder, the position of the ram shaft or the like may be monitored with a long-range linear sensor.

  In the present invention, the distance between opposing molds, that is, the position of the other mold with reference to one mold is measured by a sensor directly fixed to the mold at the position of the mold. For this reason, unlike the servo motor encoder and the linear sensor that monitors the position of the ram shaft, the distance between the molds can be measured accurately. Since measurement is performed at the position of the mold, even if the mold is deformed due to stress between the molds, or even if the mold is thermally deformed due to temperature fluctuation, heat generated by mold clamping, etc. Can be measured. Further, since the sensor only needs to be able to measure the interval in the vicinity of the section where the mold is closest, the sensor can be a high resolution sensor with a short measurement range. When the distance between the molds is measured, it can be fed back to the servo motor, or it can be determined whether or not the mold clamping device needs maintenance.

Further, the present invention provides a mold clamping method for moving at least one of opposing molds while feedback controlling the servo motor by a signal of a servo motor encoder or a long range linear sensor for monitoring the position of the ram shaft. In
Directly fixed to one mold near the opposed part of the mold and contacted with the opposed mold or the reference plate attached to the opposed mold, so that the opposed mold or the reference plate is used as a reference. A mold mounting sensor consisting of a linear sensor for measuring the position to be provided, and monitoring the interval between the molds by the signal of the mold mounting sensor,
By the switching means, the control input is continuously switched between the encoder signal or the long-range linear sensor signal and the mold mounting sensor signal,
In the mold clamping area near the mold clamping position, the servo motor is controlled by the signal from the mold mounting sensor.
In the remote area away from the mold clamping position, the servo motor is controlled by the encoder signal or the long-range linear sensor signal,
In the intermediate region between the remote region and the mold clamping region, the control input is continuously switched between the encoder signal or the long-range linear sensor signal and the mold mounting sensor signal,
The switching means controls the signal P1 of the encoder or the signal of the long range linear sensor that monitors the position of the ram shaft and the signal P2 of the mold mounting sensor with a variable weight w ranging from 0 to 1. Convert to input P3 by P3 = P1 ・ w + P2 ・ (1-w), w = 1 in the section outside the measuring range of the mold mounting sensor, W = 0 in the section where the mold is closest, and mold mounting The weight w is determined so that the weight w continuously changes from 1 to 0 when the mold enters the measurement range of the sensor for use .

When the servomotor is fed back using the signal from the mold mounting sensor, the problem is that the measurement range is short. Therefore, in the present invention, in a section outside the measurement range of the mold mounting sensor, a signal from the servo motor encoder or the like is used as a control input, and control is performed between the signal from the mold mounting sensor and the signal from the encoder or the like. Switches input continuously. Then, even if the control input is switched, control disturbance does not occur. Note that the control when the molds are returned and moved away from each other does not affect the accuracy of mold clamping. Therefore, the weight w may be fixed to 1, for example, at the time of return. In this specification, the description regarding the mold clamping device is also applied to the mold clamping method as it is.

In this invention, the switching means uses a variable weight w between 0 and 1 to change the signal P1 of the encoder or the signal of the long range linear sensor for monitoring the position of the ram shaft and the signal P2 of the mold mounting sensor. , Converted to control input P3 by P3 = P1 · w + P2 · (1-w), w = 1 in the section outside the measurement range of the mold mounting sensor, W = 0 in the section closest to the mold, When the mold enters the measurement range of the mold mounting sensor, the weight w continuously changes from 1 to 0. Therefore , the control input can be easily and smoothly switched between the encoder or the like and the mold mounting sensor.

Preferably, the control unit converts the error between the command position and the control input into a speed command, and converts the error between the speed command and the rate of change of the encoder signal per time into a current command. Speed control means, and the control based on the integral value of the error between the command position and the control input is not performed. In this way, since the speed control loop can be controlled by the signal of the encoder that can obtain a signal in a short cycle, the speed can be accurately controlled even if the cycle in which the signal is obtained from the sensor is long.

Preferably, the mold mounting sensor includes a magnetic rod provided with a magnetic mark and advanced / retracted by an opposing mold, a sensor head for measuring the advance / retreat position of the magnetic rod, and the magnetic rod toward the ram axis side. It has a stopper that determines the movement limit and an elastic body that urges the magnetic rod toward the ram shaft. The magnetic rod is configured to move along the ram axis in contact with an opposing mold or the reference plate, and the magnetic rod is attached in advance to the ram axis side by an elastic body at a position fixed by a stopper. By being biased, the vibration of the magnetic rod due to the contact with the contact member is damped. In this way, it is possible to accurately measure the distance between the molds by reducing the amplitude of the sensor signal.

Block diagram showing an injection molding apparatus of an embodiment The figure which shows the control part of the servomotor in an Example The figure which shows the linear sensor in an Example 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. Vertical section showing the linear sensor in the optimum embodiment The figure explaining the damping of the vibration of the linear sensor in the optimum embodiment Plan view showing mounting of linear sensor to lower mold in optimum embodiment Characteristic chart showing mold position and motor end position in the optimum embodiment Characteristic diagram showing mold position and motor end position in the conventional 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.

Basic Embodiment FIGS. 1 to 4 show a basic embodiment and its characteristics. FIG. 1 shows an injection molding apparatus 2 according to an embodiment. An upper mold 4 is a movable mold that moves up and down by a ram shaft (diver) 12, and a movable mold 8 for injecting synthetic resin by injection molding is set. Has been. A fixed mold 10 for injecting synthetic resin is set in the fixed lower mold 6. The upper mold 4 is guided by, for example, four guide pins 11, and moves up and down via the ram shaft 12 by a crank mechanism 14 and a servo motor 16. 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. The dies 4 and 6 may be arranged on the left and right instead of the upper and lower sides to face each other. Moreover, it is good also as a press molding apparatus except the injection apparatus 18, and also it is good also as a die-cast molding apparatus. A toggle mechanism or the like may be used instead of the crank mechanism 14, or the crank mechanism 14 or the like may not be provided.

  The control unit 20 feedback-controls the servo motor 16 based on signals from the encoder and the die mounting linear sensor 22. A mold mounting linear sensor 22 is fixed to the upper part of the lower mold 6, and the distance from the reference plate 24 of the mold mounting linear sensor fixed to the lower part of the upper mold 4 is measured. For example, one pair, two pairs, or four pairs of combinations of the die mounting linear sensor 22 and the reference plate 24 are provided. In the embodiment, one pair is provided on each of the four circumferences of the molds 4 and 6. The mold mounting linear sensor 22 and the reference plate 24 are fixed in the vicinity of the opposing portions of the molds 4 and 6, and the actual distance between the molds 4 and 6 is measured by the mold mounting linear sensor 22. The strain gauge 26 corrects the signal of the die mounting linear sensor 22 by detecting strain due to contact of the dies 4 and 6, but the strain gauge 26 may not be provided.

FIG. 2 shows the control unit 20 of the servo motor 16. The command generator 30 outputs a position command P0 according to the operation pattern of the upper mold 4. 31 and 32 are differentiators, 33 and 34 are amplifiers, 35 is a current amplifier, and the current amplifier 35 is controlled so that the drive current of the servo motor 16 matches the target value. The servo motor 16 includes an encoder 36 and feeds back the amount of change of the encoder signal per time to the subtractor 32 as a speed signal v. Further, for example, the position signals of the four die mounting linear sensors 22 are averaged by the adder 38 and output to the adder 40. When there is one die mounting linear sensor 22, the adder 38 is unnecessary. The signal of the die mounting linear sensor 22 is aligned with the signal of the encoder 36 by subtracting an offset corresponding to the distance from the axis of the servo motor 16 to the reference plate 24. The adder 40 averages the signal from the encoder 36 and the signal from the adder 38 on the side of the die mounting linear sensor 22 according to the variable weight w input from the command generator 30. The weight w is 0 or more and 1 or less. The weight of the signal P1 from the encoder 36 is w, the weight of the signal P2 from the adder 38 is (1-w),
P3 = P1 ・ w ＋ P2 ・ (1-w) (1)
The position signal P3 is obtained from equation (1). In order to generate the weight w, any one of the signals P1, P2, and P3 is input to the command generator 30, and the command generator 30 stores w for the values of these signals.

  The differentiator 31 outputs the difference between the position command P0 and the position signal P3 as a position error, and the amplifier 33 multiplies the position error by the control constant Kp and inputs it to the differencer 32 as a speed command v0. The subtractor 32 outputs the difference between the speed command v0 and the speed signal v consisting of the rate of change of the signal of the encoder 36 as a speed error, the amplifier 34 multiplies the control constant Kv to the speed error, and the current amplifier 35 as a current command. Output to. As described above, in the speed control loop constituted by the differencer 32, the amplifier 34, etc., the speed signal v from the encoder 36 is used, and in the position control loop constituted by the differencer 31, the amplifier 33, etc., the encoder The position signal P3 generated so that the signal P1 of 36 and the signal P2 of the linear sensor 22 for mold attachment are smoothly switched by the adder 40 is used. The signal of the strain gauge 26 represents the stress accompanying the contact between the upper and lower molds and is input to the command generator 30 in order to correct the influence of the mounting position of the mold mounting linear sensor 22.

  FIG. 3 shows the arrangement of the die mounting linear sensor 22 and the like. A reference plate 24 and a die mounting linear sensor 22 are arranged in the vicinity of the opposing portions of the dies 4 and 6. Note that the mold mounting linear sensor 22 may be disposed on the upper mold 4 side, and the reference plate 24 may be disposed on the lower mold 6 side. The die mounting linear sensor 22 includes a case 42 and a magnetic rod 44 that can be moved up and down, and the magnetic rod 44 includes a magnetic mark (not shown) for one period to a plurality of periods. A magnetic rod reference plate 45 is fixed to the tip of the magnetic rod 44, and the opposing surfaces of the reference plates 24 and 45 are referred to as reference surfaces 46 and 47, respectively. The magnetic rod 44 can freely move up and down in FIG. 3 in the case 42, is urged in advance in the protruding direction by an elastic body 49 and stoppers 49a and 49b, and a sensor head 48 including four or more coils of magnetic marks. To detect. An alternating current is applied to the coil of the sensor head 48, and an impedance change due to the interaction with the magnetic mark is detected as a phase with the magnetic mark as a reference. The magnetic rod 44 is provided with a magnetic mark in a range of a length of, for example, about several millimeters, and this defines a measurement range of the die mounting linear sensor 22. Although the mold mounting linear sensor 22 has a measurement range on the minus side of the mold clamping position, the upper mold stops at the mold clamping position and the mechanical stop state is entered. Further, in a section where the position of the upper mold cannot be detected beyond the measurement range of the mold mounting linear sensor 22, the encoder signal or the signal of a long range linear sensor (not shown) for monitoring the position of the ram shaft 12 is used. Control the servo motor.

  FIG. 4 shows the weight w on the encoder signal, and the weight on the linear sensor signal is (1-w). When the linear sensor cannot detect the position of the upper mold, w is 1, and when the linear sensor is able to detect the position of the upper mold, the weight w is 0 in the section near the lowermost end of the upper mold stroke. As shown in 1) of FIG. 4, the weight w is continuously changed from 1 to 0. For this reason, in the section using the encoder signal, the servomotor is controlled by the rotation angle of the servomotor shaft, and in the section using the linear sensor signal, the servomotor is controlled by the interval between the upper mold and the lower mold. Even when the upper mold reaches the lowermost end, the rotation angle of the motor shaft is not constant due to deformation of the mold due to compressive stress, etc., and vibrates finely as shown in 2) of FIG.

Optimum Embodiment FIGS. 5 to 8 show the optimum embodiment and its characteristics, and are the same as the basic embodiment of FIGS. FIG. 5 shows a cross section of the linear sensor 50, 51 is a metal case, and a movable magnetic rod 44 is provided with a magnetic mark comprising a magnetic body 52 and a non-magnetic body 53, and a sensor head having 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 with each other on the left and right in the drawing. Slide. 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 side, the connecting member 55 is positioned by the stopper 56 due to the urging by the elastic body 49, and the stroke of the magnetic rod 44 is about 10 mm, for example. Within this stroke range, the distance between the upper and lower molds is measured, and at the beginning of the stroke, the encoder signal and the linear sensor 50 signal are weighted and averaged and fed back to the servo motor. Descent to the lowest point and perform injection molding, die casting, press molding, etc.

  If the magnetic rod 44 is suddenly urged to the right side of the figure by the upper die, the magnetic rod 44 may move independently from the reference plate on the upper die side. Such vibration makes the control of the servo motor unstable. On the other hand, by using the elastic body 49 and the stopper 56 and strongly urging the magnetic rod 44 from the beginning toward the reference plate 45 side, the deceleration (absolute value of acceleration) of the magnetic rod 44 is increased to the upper part. Make it larger than the mold deceleration. Then vibration does not occur. Also, even if vibration occurs, it occurs only at the beginning of the stroke. If the encoder signal and the linear sensor 50 signal are averaged and used, the influence of vibration can be reduced. Such a mechanism is shown in FIG.

  FIG. 6 shows the position and speed of the upper mold 4 near the lowest point P of the upper mold, and the locus 60 represents the position and speed of the upper mold 4. Further, the locus is shown in the chain line 62 in the upper right circle, assuming that the magnetic rod 44 of the linear sensor moves away from the upper mold. Assuming that the magnetic rod 44 moves independently of the upper mold 4, the deceleration a is proportional to the elastic constant of the elastic body 49, and increases when the elastic body 49 is compressed by the stopper 56. When the deceleration of the upper mold 4 is b, when the deceleration a of the magnetic rod 44 is larger than the deceleration b of the upper mold, the magnetic rod is pressed against the upper mold by the elastic body and does not vibrate. Therefore, the vibration of the magnetic rod 44 can be prevented by selecting the elastic constant of the elastic body 49 and the position of the stopper 56. Since the deceleration a of the magnetic rod increases as it approaches the lowest point, the possibility that the magnetic rod trajectory 62 is separated from the trajectory 60 of the upper die is limited to the initial stroke. At the beginning of the stroke, speed control is performed using both the encoder and the linear sensor. Therefore, even if vibration of the magnetic rod 44 occurs, the speed control is small.

  FIG. 7 shows attachment of the linear sensor 50 to the lower mold 6. Linear sensors 50 are fixed at, for example, four locations around the chamber 70 that performs injection molding, die casting molding, press molding, and the like. Therefore, the relative position between the upper and lower molds can be accurately measured without being affected by the stress associated with the contact between the upper and lower molds 4 and 6 and the temperature change of the lower mold 6. Further, since the linear sensors 50 are arranged at a plurality of positions around the chamber 70, it is possible to accurately measure the average value and the deviation of the relative positions between the molds. It should be noted that the upper mold may be provided with the reference plate 24, or the upper mold itself may be used as the reference plate without providing the reference plate 24.

  FIG. 8 shows the control result in the optimum embodiment, and FIG. 9 shows the control result in the conventional example in which the servomotor is controlled only by the encoder signal. The motor end position in the figure represents the signal of the encoder, and here, the result in the section near the lowest end in the stroke of the upper mold is shown. In the embodiment, at the mold clamping position, the distance between the upper and lower molds including the disturbance of the system can be controlled with an error of less than 3 μm. The measurement error of the linear sensor can be about ± 1 μm, for example. Also, the position at the motor end is not constant due to stress caused by contact with the mold. In the embodiment, feedback control is performed with a signal from the linear sensor so as to correct deformation due to stress, thermal deformation, and the like. Therefore, if the lower end position of the upper mold is made constant, the position of the motor end is not constant. On the other hand, in the conventional example, the position of the motor end is constant, and the lower end position of the upper mold is unstable.

The embodiment has the following characteristics.
1) Measure the actual distance between the molds 4 and 6 using the mold mounting linear sensors 22 and 50 and the reference plate 24 in the vicinity of the opposing portions of the upper and lower molds 4 and 6.
2) Measure the distance between the dies 4 and 6 with high positional resolution using the die mounting linear sensors 22 and 50 having a short measurement range.
3) In a section outside the measurement range of the die mounting linear sensors 22 and 50, the signal of the encoder 36 is used and the signal weight w of the encoder 36 and the weight (1-w) of the signal of the linear sensor are added by the adder 40. Is continuously changed, so that the disturbance of the control accompanying the switching of the sensor does not occur.
4) Configure multiple feedback control loops to control speed as a minor loop for position control and to control torque (current) as a minor loop for speed control.
5) When switching between the feedback signal encoder and the linear sensor, the control loop is switched to change only the feedback signal. For this reason, it is preferable to match the signal responsiveness, minimum resolution, and the like by preprocessing between the encoder and the linear sensor. In addition, the parameters for specifying the position and the servo parameters such as loop gain use the same numerical value even when the feedback signal is switched.
6) The magnetic rod 44 is biased in advance to the movable upper mold side by the elastic body 49 and the stopper 56, and the deceleration when the magnetic rod 44 moves independently from the upper mold side is Increase the deceleration of the upper mold. Then, since the magnetic rod 44 cannot move away from the upper mold side, the behavior of the die to be accurately measured, that is, the behavior of the magnetic rod 44 and the behavior of the linear sensor can be matched in time.
7) The region in which the magnetic rod 44 moves independently from the upper die is such that the reference plate 45 of the magnetic rod is not in contact with the reference plate 24 of the die mounting linear sensor, and both reference plates are It is limited to the initial stroke of the magnetic rod 44 after contact. In this region, since the speed control is performed using both the encoder signal and the linear sensor signal, even if vibration of the magnetic rod 44 occurs, the influence can be reduced on the control side.
8) When a plurality of linear sensors 50 and the like are arranged in the lower mold 6 fixed around the chamber 70 as shown in FIG. 7, the relative positions of the upper and lower molds can be measured accurately. In particular, since measurement is performed inside the mold and in the vicinity of the chamber, deformation due to contact with the mold, deformation due to temperature deformation of the mold, and the like do not cause errors. It is also possible to measure the deviation of the positions of the upper and lower molds.
9) When mold clamping is finished, cut the torque output from the control loop or limit to low torque to prevent abnormal heat generation of the motor.

2 Injection molding apparatus 4 Upper mold 6 Lower mold 8 Moving mold 10 Fixed mold 11 Guide pin 12 Ram shaft 14 Crank mechanism 16 Servo motor 18 Injection apparatus 20 Control unit 22, 50 Linear sensor 24 for mold installation Mold Reference plate 26 of linear sensor for mounting Strain gauge 30 Command generators 31 and 32 Difference units 33 and 34 Amplifier 35 Current amplifier 36 Encoder 38 and 40 Adders 42 and 51 Case 44 Magnetic rod 45 Reference rod 46 of magnetic rod 47 Reference surface 48 Sensor head 49 Elastic body 54 Sliding member 55 Connecting member 56 Stopper 57 Groove 60, 62 Trajectory 70 Chamber

Claims (4)

At least a pair of opposed molds, a servo motor that moves at least one of the molds via a ram shaft, and a long range linear sensor that monitors the encoder signal of the servo motor or the position of the ram shaft In a mold clamping device including a control unit that feedback-controls a servo motor using a signal as a control input,
Directly fixed to one mold near the opposed part of the mold and contacted with the opposed mold or the reference plate attached to the opposed mold, so that the opposed mold or the reference plate is used as a reference. A mold mounting sensor comprising a linear sensor for measuring the position is provided, and the distance between the molds is monitored by a signal from the mold mounting sensor .
A switching means for continuously switching the control input between the encoder signal or the long-range linear sensor signal and the mold mounting sensor signal;
In the mold clamping area near the mold clamping position, the servo motor is controlled by the signal from the mold mounting sensor.
In the remote area away from the mold clamping position, the servo motor is controlled by the encoder signal or the long-range linear sensor signal,
In the intermediate area between the remote area and the mold clamping area, the control input is continuously switched between the encoder signal or the long range linear sensor signal and the mold mounting sensor signal. ,
The switching means controls the signal P1 of the encoder or the signal of the long range linear sensor that monitors the position of the ram shaft and the signal P2 of the mold mounting sensor with a variable weight w ranging from 0 to 1. Convert to input P3 by P3 = P1 ・ w + P2 ・ (1-w), w = 1 in the section outside the measuring range of the mold mounting sensor, W = 0 in the section where the mold is closest, and mold mounting A mold clamping device , wherein the weight w is determined so that the weight w continuously changes from 1 to 0 when the mold enters the measurement range of the sensor for use . The controller is
Position control means for converting an error between the command position and the control input into a speed command;
Speed control means for converting the error in the speed command and the rate of change per time of the signal of the encoder to the current command, comprising the city,
2. The mold clamping apparatus according to claim 1, wherein the mold clamping apparatus is configured not to perform control based on an integral value of an error between the command position and the control input . The mold mounting sensor includes a magnetic rod provided with a magnetic mark and advanced / retracted by an opposing mold, a sensor head for measuring the advance / retreat position of the magnetic rod, and a limit of movement of the magnetic rod toward the ram axis. And an elastic body that urges the magnetic rod toward the ram shaft side ,
The magnetic rod is configured to move along a ram axis in contact with an opposing mold or the reference plate,
When the magnetic rod is biased in advance by the elastic body toward the ram axis at a position fixed by the stopper, the vibration of the magnetic rod due to contact with the contact member is damped. The mold clamping device according to claim 1 or 2 , characterized by the above-mentioned. In the mold clamping method of moving at least one of the opposing molds while feedback controlling the servo motor by a signal of a servo motor encoder or a signal of a long range linear sensor that monitors the position of the ram shaft,
Directly fixed to one mold near the opposed part of the mold and contacted with the opposed mold or the reference plate attached to the opposed mold, so that the opposed mold or the reference plate is used as a reference. A mold mounting sensor consisting of a linear sensor for measuring the position to be provided, and monitoring the interval between the molds by the signal of the mold mounting sensor,
By the switching means, the control input is continuously switched between the encoder signal or the long-range linear sensor signal and the mold mounting sensor signal,
In the mold clamping area near the mold clamping position, the servo motor is controlled by the signal from the mold mounting sensor.
In the remote area away from the mold clamping position, the servo motor is controlled by the encoder signal or the long-range linear sensor signal,
In the intermediate region between the remote region and the mold clamping region, the control input is continuously switched between the encoder signal or the long-range linear sensor signal and the mold mounting sensor signal,
The switching means controls the signal P1 of the encoder or the signal of the long range linear sensor that monitors the position of the ram shaft and the signal P2 of the mold mounting sensor with a variable weight w ranging from 0 to 1. Convert to input P3 by P3 = P1 ・ w + P2 ・ (1-w), w = 1 in the section outside the measuring range of the mold mounting sensor, W = 0 in the section where the mold is closest, and mold mounting A mold clamping method , wherein the weight w is determined so that the weight w continuously changes from 1 to 0 when the mold enters the measurement range of the sensor for use .

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