JP7421964B2 - Injection molding machine and its control method - Google Patents

Description

The present invention relates to an injection molding machine and a control method thereof.

An injection molding machine that performs injection molding using a material that is a mixture of fibers and resin is disclosed in Patent Document 1. FIG. 7 shows a part of the configuration of such an injection molding machine.

In the injection molding machine 101 shown in FIG. 7, the screw 112 is advanced so that the moving speed becomes the speed target value in the injection operation. The injection molding machine 101 measures the pressure applied to the screw 112 as the pressure applied to the resin in the heating cylinder 111 (resin pressure). The injection molding machine 101 is provided with an upper limit value of resin pressure (upper limit pressure value) in order to detect abnormalities such as nozzle clogging of the heating cylinder 111. The injection molding machine 101 limits the output of the motor that advances the screw when the resin pressure exceeds the upper pressure limit.

JP2018-012221A

When the screw 112 moves forward during the injection operation, the material S supplied from the hopper 111b to the heating cylinder 111 may be caught between the heating cylinder 111 and the screw 112, as shown in FIG. At this time, the injection molding machine 101 controls the motor to increase the force for advancing the screw 112 in order to maintain the moving speed of the screw 112. As a result, the material S sandwiched between the heating cylinder 111 and the screw 112 may be cut.

However, since a force to cut the material S is applied to the screw 112, the pressure applied to the screw 112 may temporarily increase and exceed the upper pressure limit. At this time, the injection molding machine 101 limits the output of the motor, the moving speed of the screw 112 temporarily decreases, and the pressure applied to the resin in the heating cylinder 111 also temporarily decreases. Therefore, variations may occur in the moving speed of the screw 112 and the resin pressure during the injection operation. These variations may affect the quality of the molded product.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an injection molding machine and a control method thereof that can suppress variations in screw movement speed and resin pressure during injection operation.

In order to achieve the above object, an injection molding machine according to the present invention includes a heating cylinder, a screw housed in the heating cylinder, a drive device for moving the screw back and forth, and a pressure applied to the screw. An injection molding machine comprising: a measuring device; and a control device for controlling the drive device, wherein the control device is configured such that during injection operation, a measured value of the pressure applied to the screw measured by the measuring device is a pressure upper limit. when the moving speed of the screw is equal to the target speed value, when the measured value exceeds the pressure upper limit value and the rising speed of the measured value is less than or equal to the limit determination value, The driving device is controlled so that the measured value is equal to or less than the pressure upper limit value, and when the measured value exceeds the pressure upper limit value and the rising speed of the measured value exceeds the limit judgment value, the drive device is controlled so that the measured value is equal to or lower than the pressure upper limit value, and when the measured value exceeds the pressure upper limit value and the rising speed of the measured value exceeds the limit judgment value, , the driving device is controlled so that the moving speed of the screw becomes the speed target value.

According to the present invention, variations in the moving speed of the screw and the resin pressure during the injection operation can be suppressed.

1 is a diagram showing a schematic configuration of an injection molding machine according to an embodiment of the present invention. 2 is a graph schematically showing an example of the relationship between the position of the screw, the moving speed of the screw, and the resin pressure during the injection operation in the injection molding machine of FIG. 1 (when there is no material pinching). This is a graph schematically showing an example of the relationship between the position of the screw, the moving speed of the screw, and the resin pressure during injection operation in the injection molding machine of FIG. 1. (if exceeded). This is a graph schematically showing an example of the relationship between the position of the screw, the moving speed of the screw, and the resin pressure during injection operation in the injection molding machine of FIG. 1. (if exceeded). This is a graph schematically showing an example of the relationship between the position of the screw, the moving speed of the screw, and the resin pressure during injection operation in a conventional injection molding machine. ). This is a graph schematically showing an example of the relationship between the position of the screw, the moving speed of the screw, and the resin pressure during injection operation in the injection molding machine of FIG. 1. ). 1 is a diagram showing the configuration of a conventional injection molding machine.

An injection molding machine according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

The injection molding machine of this embodiment performs injection molding using a material that is a mixture of fiber and resin. This injection molding machine performs various operations such as an injection operation, a pressure holding operation, a cooling operation (including a metering operation), and a mold opening/closing operation in an injection molding cycle.

As shown in FIG. 1, the injection molding machine 1 includes an injection device 10 and a control device 30.

The injection device 10 includes a heating cylinder 11, a screw 12, a metering servo motor 13, a metering timing belt 14, a metering pulley 15, an injection servo motor 16, an injection timing belt 17, and a ball screw mechanism. 18, a measuring encoder 19, an injection encoder 20, and a load cell 21 as a measuring device.

The heating cylinder 11 is formed into a cylindrical shape. The heating cylinder 11 is equipped with a heater (not shown) on its outer peripheral surface. The heating cylinder 11 is provided with a nozzle 11a at one end, and a hopper 11b near the other end. The hopper 11b supplies the heating cylinder 11 with a material in which fibers such as glass fibers and carbon fibers are mixed with resin. Note that the fibers and resin may be supplied to the heating cylinder 11 from separate locations. The screw 12 is housed within the heating cylinder 11 so as to be rotatable and movable in the front and rear directions. In this specification, the nozzle 11a side of the heating cylinder 11 in FIG. 1 is referred to as the front side, and the opposite side is referred to as the rear side.

The metering servo motor 13 is a drive device that rotates the screw 12. The rotation of the output pulley 13a of the metering servo motor 13 is transmitted to the metering pulley 15 via the metering timing belt 14. The metering pulley 15 is coaxially fixed to the screw 12. The rotation of the metering pulley 15 causes the screw 12 to rotate about its axis.

The injection servo motor 16 is a drive device that moves the screw 12 forward and backward. The rotation of an output pulley 16a of the injection servo motor 16 is transmitted via an injection timing belt 17 to an injection pulley 18b coaxially fixed to a screw shaft 18a of a ball screw mechanism 18. The rotation of the injection pulley 18b causes the screw shaft 18a to rotate about the shaft. As the screw shaft 18a rotates, the nut portion 18c of the ball screw mechanism 18 screwed onto the screw shaft 18a moves in the axial direction (that is, in the front-rear direction). As the nut portion 18c moves, the screw 12 connected to the nut portion 18c is moved in the front-rear direction.

The metering encoder 19 measures the rotational position of the metering servo motor 13 and outputs it as a rotational position output A1. The control unit 33 of the control device 30 obtains the rotational speed R of the screw 12 based on this rotational position output A1.

The injection encoder 20 measures the rotational position of the injection servo motor 16 and outputs it as a rotational position output A2. Based on this rotational position output A2, the control unit 33 of the control device 30 acquires the position L and the moving speed V of the screw 12 in the longitudinal direction.

The load cell 21 measures the pressure applied to the screw 12 and outputs it as a pressure output A3. The control unit 33 of the control device 30 acquires the pressure applied to the screw 12 based on this pressure output A3. The measured value of the pressure of the screw 12 indicates the pressure applied to the resin stored in the space E in front of the screw 12 in the heating cylinder 11 (hereinafter simply referred to as "resin pressure P"). The control unit 33 also obtains the rate of increase Vp of the resin pressure P. The rising speed Vp is the amount of increase in the resin pressure P per unit time (Vp=ΔP/Δt).

The control device 30 includes a setting storage section 31, a display operation section 32, a control section 33, a metering servo amplifier 34, and an injection servo amplifier 35.

The setting storage unit 31 is configured to include, for example, a rewritable storage medium such as a hard disk device and a nonvolatile memory. The setting storage section 31 stores condition values for various operations included in the injection molding cycle.

The setting storage unit 31 stores, for example, an injection start position Ls and a speed target value Vs. The injection start position Ls is the position of the screw 12 at the start of the injection operation. The speed target value Vs is a target value of the moving speed V of the screw 12 during the injection operation.

The setting storage section 31 stores a pressure upper limit value Ps that is the upper limit value of the resin pressure P in the injection operation. The pressure upper limit value Ps is set, for example, based on the rated output of the injection servo motor 16 (for example, 90% of the rated output).

The setting storage unit 31 stores a limit determination value Vps of the rising speed Vp of the resin pressure P in the injection operation and a pressure permissible period Tps. The limit determination value Vps is based on the rising speed Vp of the resin pressure P when the material is actually sandwiched between the heating cylinder 11 and the screw 12 during the injection operation, that is, when the material is pinched (for example, (a little lower than the rising speed Vp). The pressure permissible period Tps is set based on a temporary rise period of the resin pressure P when the material is caught (for example, a period slightly longer than the rise period).

The setting storage unit 31 stores a pressure holding target value Ph which is a target value of the resin pressure P in the pressure holding operation. The holding pressure target value Ph is appropriately set according to the configuration of the injection molding machine 1, the shape of the molded product, the type of resin, etc.

The setting storage unit 31 stores a correction determination value Vph of the rising speed Vp of the resin pressure P in the pressure holding operation and a fluctuation restriction period Tph. The corrected judgment value Vph is based on the rate of rise Vp of the resin pressure P when the material is actually sandwiched between the heating cylinder 11 and the screw 12 during the pressure holding operation (for example, if the rate is slightly lower than the rate of rise Vp). ) is set. The fluctuation restriction period Tph is based on a temporary rise period of the resin pressure P when the material is actually sandwiched between the heating cylinder 11 and the screw 12 during the pressure holding operation (for example, a period slightly longer than the rise period). ) is set.

The display operation unit 32 includes a display unit 32a configured with a flat panel display such as a liquid crystal display or an organic EL display, and a touch panel and hardware keys arranged over the display surface of the display unit 32a. 32b. The display/operation unit 32 is used to check the status of the injection molding machine 1 and input various operations. The display operation section 32 is also used for storing condition values in the setting storage section 31.

The control unit 33 is composed of a microcomputer or the like. The control unit 33 generates control signals in various operations, outputs the control signals to the metering servo amplifier 34 and the injection servo amplifier 35, and controls the metering servo motor 13 and the injection servo motor 16. The control unit 33 also generates control signals to control a mold opening/closing mechanism (not shown).

In the various operations described above, the control unit 33 outputs the rotational position output A1 of the metering encoder 19, the rotational position output A2 of the injection encoder 20, the pressure output A3 of the load cell 21, and the condition value stored in the setting storage unit 31. Based on the above, the rotational speed R, moving speed V and position L of the screw 12, as well as the resin pressure P, are adjusted.

Next, an example of operations performed by the injection molding machine 1 described above in an injection molding cycle will be described.

In the injection molding cycle, the control unit 33 injects the resin stored in the front space E in the heating cylinder 11 into the mold by advancing the screw 12 (injection operation). Following the injection operation, the control unit 33 maintains the pressure of the resin accumulated in the front space E by adjusting the position of the screw 12 in the front-rear direction (pressure-holding operation). Following the pressure holding operation, the resin in the mold is solidified (cooling operation). During the cooling operation, the control unit 33 performs a metering operation to measure and store resin in the front space E. Following the cooling operation, the control unit 33 opens the mold using a mold opening/closing mechanism (not shown), takes out the molded product, and then closes the mold (mold opening/closing operation).

The operation (control method) of the control section 33 in the injection operation will be explained in detail.

In the injection operation, the control unit 33 controls the injection servo motor 16 based on the rotational position output A2 of the injection encoder 20 so that the screw 12 at the injection start position Ls moves toward position 0 at the speed target value Vs. Feedback control (for example, PID control) is performed. At this time, the control unit 33 acquires the resin pressure P (measured value of the pressure applied to the screw 12) and the rising speed Vp of the resin pressure P based on the pressure output A3 of the load cell 21.

In the injection operation, when the resin pressure P is lower than the upper pressure limit Ps (P≦Ps), the control unit 33 performs feedback control of the injection servo motor 16 so that the moving speed V of the screw 12 becomes the speed target value Vs. conduct. In the following description, this feedback control will simply be referred to as "feedback control based on the moving speed V."

In the injection operation, when the resin pressure P exceeds the pressure upper limit Ps and the rising speed Vp when the resin pressure P exceeds the pressure upper limit Ps is less than or equal to the limit judgment value Vps (P>Ps and Vp≦Vps), the injection servo motor 16 is controlled so that the resin pressure P becomes the pressure upper limit value Ps, giving priority to feedback control based on the moving speed V. In the following description, this control will simply be referred to as "control based on resin pressure P." In this control, the output of the injection servo motor 16 is limited so that the resin pressure P becomes the pressure upper limit value Ps (or a value equal to or lower than the pressure upper limit value Ps). In order to balance the resin pressure P, the moving speed V decreases below the speed target value Vs. Thereafter, when the pressure applied to the screw 12 decreases and the moving speed V returns to the speed target value Vs in balance with the resin pressure P, the feedback control based on the moving speed V is returned to. Note that the above-mentioned "when the resin pressure P exceeds the pressure upper limit Ps" includes not only the literal timing but also the timing shifted from the timing by about the measurement time interval of the resin pressure P.

In the injection operation, the control unit 33 controls the control unit 33 to determine whether the resin pressure P exceeds the pressure upper limit Ps and the rising speed Vp when the resin pressure P exceeds the pressure upper limit Ps exceeds the limit determination value Vps (P> Ps and Vp>Vps), and feedback control based on the moving speed V is performed over the pressure permissible period Tps. Specifically, the control unit 33 assumes that the resin pressure P is the pressure upper limit value Ps over the pressure permissible period Tps (P=Ps). Thereby, the control unit 33 performs feedback control based on the moving speed V over the pressure permissible period Tps, as in the case where the resin pressure P is equal to or less than the pressure upper limit value Ps (P≦Ps).

FIGS. 2 to 6 schematically show examples of the relationship between the screw position L, the screw moving speed V, and the resin pressure P during the injection operation. In FIGS. 2 to 6, when the injection operation is started, feedback control based on the moving speed V is performed. The resin pressure P increases while changing so that as the position L of the screw approaches the position 0, the slope (rising speed Vp) gradually decreases. 2 to 6, solid lines indicate the moving speed V and resin pressure P acquired by the control unit 33, and dashed lines indicate control based on the resin pressure P when the resin pressure P exceeds the upper pressure limit Ps. The resin pressure P is shown in the case where feedback control based on the moving speed V is performed as it is.

FIG. 2 shows a case in which the material is not caught between the heating cylinder 11 and the screw 12 in the injection molding machine 1, and the resin pressure P remains below the upper pressure limit Ps (when there is no material caught). In this case, the control unit 33 performs feedback control based on the moving speed V until the end of the injection operation. The resin pressure P changes so as to approach the pressure upper limit Ps while gradually decreasing the slope (increase rate Vp).

FIG. 3 shows a case where the material is not caught between the heating cylinder 11 and the screw 12 in the injection molding machine 1, but the resin pressure P exceeds the upper pressure limit Ps due to the high viscosity of the resin ( (The case where the resin pressure P gradually exceeds the pressure upper limit Ps without material being caught) is shown. In this case, the rising speed Vp when the resin pressure P exceeds the pressure upper limit value Ps is relatively low, and the rising speed Vp is equal to or lower than the limit determination value Vps. Therefore, when the resin pressure P exceeds the pressure upper limit Ps, the control unit 33 performs control based on the resin pressure P with priority over feedback control based on the moving speed V. In the example shown in FIG. 3, after the resin pressure P exceeds the pressure upper limit Ps, the resin pressure P remains at the pressure upper limit Ps, and the moving speed V of the screw 12 becomes lower than the speed target value Vs.

FIG. 4 shows a case where the material is caught between the heating cylinder 11 and the screw 12 in the injection molding machine 1, and the resin pressure P exceeds the upper pressure limit Ps (the resin pressure P suddenly increases due to the material being caught). (when the pressure exceeds the upper limit Ps). In this case, the rising speed Vp when the resin pressure P exceeds the pressure upper limit value Ps is relatively high, and the rising speed Vp exceeds the limit determination value Vps. Therefore, the control unit 33 considers that the resin pressure P has been at the pressure upper limit Ps for the pressure permissible period Tps from the time when the resin pressure P exceeds the pressure upper limit Ps. Thereby, the control unit 33 continues to perform feedback control based on the moving speed V over the pressure permissible period Tps, and the moving speed V of the screw 12 is maintained at the speed target value Vs. Then, when the pressure permissible period Tps has elapsed, the resin pressure P becomes equal to or less than the pressure upper limit value Ps, and feedback control based on the moving speed V is subsequently performed. Note that if the resin pressure P does not decrease below the pressure upper limit after the pressure permissible period Tps has elapsed, control based on the resin pressure P as shown in FIG. 3 is performed according to the rising speed Vp (Vp≦Vps). Also, control is performed when an abnormality occurs (Vp>Vps) as shown in FIG.

Figure 5 shows a case where, in a conventional injection molding machine, the material is caught between the heating cylinder and the screw, and the resin pressure P exceeds the pressure upper limit Ps (the material is caught, the resin pressure P suddenly increases, and the pressure exceeds the upper limit Ps). In this case, the conventional injection molding machine performs control based on the resin pressure P with priority over feedback control based on the moving speed V. In the example shown in FIG. 5, after the resin pressure P exceeds the pressure upper limit Ps, the output of the injection servo motor 16 is temporarily limited, the resin pressure P reaches the pressure upper limit Ps, and the moving speed V of the screw 12 temporarily becomes lower than the target speed value Vs. Therefore, the pressure applied to the resin stored in the front space E within the heating cylinder 11 is temporarily reduced.

FIG. 6 shows a case where the resin pressure P suddenly rises to exceed the pressure upper limit Ps due to some cause in the injection molding machine 1 (a case where the resin pressure P rapidly rises and exceeds the pressure upper limit Ps due to an abnormality occurrence). shows. In this case, the rising speed Vp when the resin pressure P exceeds the pressure upper limit value Ps is relatively high, and the rising speed Vp exceeds the limit determination value Vps. Therefore, similarly to the case shown in FIG. 4, the control unit 33 considers that the resin pressure P has been at the pressure upper limit Ps for the pressure permissible period Tps from the time when the resin pressure P exceeds the pressure upper limit Ps. Thereby, the control unit 33 continues to perform feedback control based on the moving speed V over the pressure permissible period Tps, and the moving speed V of the screw 12 is maintained at the speed target value Vs. Then, when the resin pressure P exceeds the pressure upper limit Ps and the rising speed Vp exceeds the limit determination value Vps after the pressure permissible period Tps has elapsed, the control unit 33 determines that an abnormality has occurred and controls the injection servo motor 16 is stopped. In the injection molding machine 1, an abnormal stop judgment value Pe higher than the upper pressure limit Ps is stored in the setting storage section 31, and when the resin pressure P exceeds the abnormal stop judgment value Pe, the control section 33 The injection servo motor 16 may be stopped.

Next, the operation (control method) of the control section 33 during the pressure holding operation will be described in detail.

In the pressure holding operation, the control unit 33 acquires the resin pressure P and the rising speed Vp of the resin pressure P based on the pressure output A3 of the load cell 21. Then, the control unit 33 performs feedback control on the injection servo motor 16 so that the screw 12 moves forward or backward so that the resin pressure P reaches the target holding pressure value Ph.

In the pressure holding operation, when the resin pressure P is smaller than the target holding pressure value Ph (P<Ph), in order to increase the resin pressure P, the control unit 33 activates the injection servo motor 16 so that the screw 12 moves forward. Feedback control.

When the resin pressure P exceeds the holding pressure target value Ph due to the advancement of the screw 12, and the rising speed Vp when the resin pressure P exceeds the holding pressure target value Ph is equal to or less than the corrected judgment value Vph (P>Ph and Vp≦Vph), the control unit 33 performs feedback control on the injection servo motor 16 so that the screw 12 stops or moves backward in order to reduce the resin pressure P. Note that the above-mentioned "when the resin pressure P exceeds the holding pressure target value Ph" includes not only the literal timing but also the timing shifted from the timing by about the measurement time interval of the resin pressure P.

When the resin pressure P exceeds the holding pressure target value Ph due to the advancement of the screw 12, and the rising speed Vp when the resin pressure P exceeds the holding pressure target value Ph exceeds the corrected judgment value Vph, the corrected measured value The corrected resin pressure Pa is obtained. Then, the control unit 33 performs feedback control of the injection servo motor 16 using the corrected resin pressure Pa as the resin pressure P over the fluctuation restriction period Tph. By doing so, even if the resin pressure P suddenly increases, the fluctuations in the resin pressure P can be slowed down and feedback control can be performed.

The control unit 33 obtains the corrected resin pressure Pa using the following methods (a) to (c).

(a) The control unit 33 obtains the resin pressure P when the rising speed Vp exceeds the correction determination value Vph as the corrected resin pressure Pa.

(b) The control unit 33 sets the resin pressure P when the rising speed Vp exceeds the corrected judgment value Vph as the reference measured value Pc, and adds a coefficient smaller than 1 to the difference value obtained by subtracting the reference measured value Pc from the resin pressure P. For example, a value obtained by multiplying the reference measured value Pc by a factor of 0.2 to 0.8) is obtained as the corrected resin pressure Pa.
(c) The control unit 33 outputs the holding pressure target value Ph as the corrected resin pressure Pa.

In a conventional injection molding machine, when the material is caught between the heating cylinder 11 and the screw 12 when the screw 12 is moved forward during the pressure holding operation, a force in the backward direction acts on the screw 12, causing the resin pressure P to increase. It may rise rapidly. Therefore, even though the pressure applied to the resin in the front space E inside the heating cylinder 11 has not increased, feedback control is performed to lower the resin pressure P. As a result, the front space E inside the heating cylinder 11 The pressure applied to the resin temporarily decreases. In the injection molding machine 1 of this embodiment, the control described above is performed, so even if the material is caught between the heating cylinder 11 and the screw 12 when the screw 12 is advanced during the pressure holding operation, the resin Feedback control can be performed by slowing down fluctuations in pressure P.

As explained above, the injection molding machine 1 includes a heating cylinder 11, a screw 12 housed in the heating cylinder 11, an injection servo motor 16 that moves the screw 12 back and forth, and a pressure applied to the screw 12 (resin pressure It has a load cell 21 that measures P) and a control device 30 that controls the injection servo motor 16. In the injection operation, the control device 30 controls the injection servo motor 16 so that the moving speed V of the screw 12 becomes the speed target value Vs when the resin pressure P measured by the load cell 21 is equal to or lower than the pressure upper limit value Ps. . In the injection operation, when the resin pressure P exceeds the pressure upper limit Ps and the rising speed Vp of the resin pressure P is less than or equal to the limit determination value Vps, the control device 30 performs injection so that the resin pressure P becomes equal to or less than the pressure upper limit Ps. control the servo motor 16 for use. Then, in the injection operation, when the resin pressure P exceeds the upper pressure limit Ps and the rising speed Vp of the resin pressure P exceeds the limit determination value Vps, the control device 30 controls the moving speed of the screw 12 over the pressure permissible period Tps. The injection servo motor 16 is controlled so that V becomes the speed target value Vs. By doing this, when the material is sandwiched between the heating cylinder 11 and the screw 12, the control device 30 allows the moving speed V of the screw 12 to be increased without limiting the output of the injection servo motor 16. The injection servo motor 16 is controlled to reach the target value Vs. Therefore, the injection molding machine 1 can suppress a temporary decrease in the moving speed V of the screw 12 during the injection operation, and the pressure applied to the resin stored in the front space E in the heating cylinder 11 is temporarily decreased. can be restrained from doing so.

Further, in the injection operation, when the resin pressure P exceeds the pressure upper limit value Ps and the rate of rise Vp of the resin pressure P exceeds the limit determination value Vps, the control device 30 controls the resin pressure It is assumed that the upper limit value Ps has been reached, and the injection servo motor 16 is controlled. By doing so, the injection molding machine 1 can suppress a temporary decrease in the moving speed V of the screw 12 during the injection operation with a simple process, and the It is possible to suppress a temporary decrease in the pressure applied to the resin.

Furthermore, in the pressure holding operation, the control device 30 controls the injection servo motor 16 so that the resin pressure P becomes the pressure holding target value Ph. In the pressure holding operation, when the resin pressure P exceeds the holding pressure target value Ph and the rising speed Vp of the resin pressure P exceeds the correction judgment value Vph, the control device 30 adjusts the corrected resin pressure Pa over the fluctuation restriction period Tph. The injection servo motor 16 is controlled using the resin pressure P. (a) The control device 30 acquires the resin pressure P when the rising speed Vp of the resin pressure P exceeds the correction determination value Vph as the corrected resin pressure Pa. Or (b) the control device 30 sets the resin pressure P when the rising speed Vp of the resin pressure P exceeds the correction judgment value Vph as the reference measurement value Pc, and calculates the difference obtained by subtracting the reference measurement value Pc from the resin pressure P. A value obtained by multiplying the value by a coefficient smaller than 1 and adding it to the reference measured value Pc is obtained as the corrected resin pressure Pa. Alternatively, (c) the control device 30 obtains the holding pressure target value Ph as the corrected resin pressure Pa. By doing so, the injection molding machine 1 can maintain the resin pressure P even if the resin pressure P suddenly increases due to the material being sandwiched between the heating cylinder 11 and the screw 12 during the pressure holding operation. Feedback control can be performed by dampening fluctuations. Therefore, inappropriate feedback control can be suppressed.

Although the embodiments of the present invention have been described above, the present invention is not limited to these examples. Those skilled in the art can implement the present invention in various other ways without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 1... Injection molding machine, 10... Injection device, 11... Heating cylinder, 11a... Nozzle, 11b... Hopper, 12... Screw, 13... Servo motor for measuring, 13a... Output pulley, 14... Timing belt for measuring, 15... Measuring Pulley, 16... Injection servo motor, 16a... Output pulley, 17... Injection timing belt, 18... Ball screw mechanism, 18a... Screw shaft, 18b... Injection pulley, 18c... Nut portion, 19... Measuring encoder, 20... Encoder for injection, 21...Load cell, 30...Control device, 32...Display/operation section, 32a...Display section, 32b...Operation section, 33...Control section, 34...Servo amplifier for measurement, 35...Servo amplifier for injection, Ls... Injection start position, P...resin pressure, Ps...pressure upper limit value, Ph...pressure holding target value, Vp...rising speed, Vps...limitation judgment value, Vph...correction judgment value, V...movement speed, Vs...speed target value, Tps...Pressure permissible period, Tph...Fluctuation restriction period

Claims (4)

An injection device comprising a heating cylinder, a screw housed in the heating cylinder, a drive device for moving the screw back and forth, a measuring device for measuring the pressure applied to the screw, and a control device for controlling the drive device. A molding machine,
In the injection operation, the control device includes:
When the measured value of the pressure applied to the screw measured by the measuring device is below the upper pressure limit, controlling the drive device so that the moving speed of the screw becomes a speed target value,
When the measured value exceeds the pressure upper limit value and the rate of increase of the measured value is less than or equal to a limit determination value, controlling the drive device so that the measured value becomes less than or equal to the pressure upper limit value;
When the measured value exceeds the pressure upper limit value and the rising speed of the measured value exceeds a limit determination value, the drive device is controlled so that the moving speed of the screw becomes the speed target value over a pressure permissible period. An injection molding machine characterized by: In the injection operation, when the measured value exceeds the pressure upper limit value and the rate of rise of the measured value exceeds the limit determination value, the control device controls the control device such that the measured value remains at the pressure upper limit value for a pressure permissible period. The injection molding machine according to claim 1, wherein the drive device is controlled based on the assumption that In the pressure holding operation, the control device includes:
controlling the drive device so that the measured value becomes a holding pressure target value;
When the measured value exceeds the holding pressure target value and the rate of increase of the measured value exceeds a corrected judgment value, the corrected measured value is used as the measured value to control the drive device over a fluctuation restriction period;
The control device includes:
(a) acquiring the measured value when the rising speed of the measured value exceeds the corrected judgment value as the corrected measured value, or
(b) The measured value obtained when the rising speed of the measured value exceeds the corrected judgment value is set as the reference measured value, and the difference obtained by subtracting the reference measured value from the measured value is multiplied by a coefficient smaller than 1. obtain a value obtained by adding the value added to the reference measurement value as the corrected measurement value, or
(c) The injection molding machine according to claim 1 or 2, wherein the holding pressure target value is acquired as the corrected measured value. A method for controlling an injection molding machine including a heating cylinder, a screw housed in the heating cylinder, and a measuring device for measuring pressure applied to the screw, the method comprising:
In the injection operation,
When the measured value of the pressure applied to the screw measured by the measuring device is below the upper pressure limit, the screw is advanced so that the moving speed of the screw becomes a speed target value,
When the measured value exceeds the pressure upper limit and the rate of increase of the measured value is less than or equal to the limit determination value, advance the screw so that the measured value becomes less than or equal to the pressure upper limit;
When the measured value exceeds the pressure upper limit value and the rising speed of the measured value exceeds a limit determination value, the screw is advanced so that the moving speed of the screw becomes the speed target value over a pressure permissible period. A method for controlling an injection molding machine, characterized in that:

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