JP6222740B2 - Injection device and injection control method thereof - Google Patents

Description

  The present invention relates to an injection device of various injection molding machines such as a plastic injection molding machine and a light metal injection molding machine that obtains a molded product by injection filling a molding material such as resin and metal into a mold, and an injection control method thereof. In particular, the present invention relates to an injection control method for a filling process in which the injection speed is controlled with priority.

  In general, an injection molding machine has a mold clamping device and an injection device. The mold clamping device opens and closes and molds the mold, and the molding material that can flow with the injection device is placed in the cavity space in the mold. The product part is injected and filled through a flow path such as a sprue part, a runner part, and a gate part, and a molding material is solidified in a mold to obtain a molded product having a desired shape. The injection molding machine, for example, in one molding cycle, moves the movable mold toward the fixed mold and closes the mold, closes the mold, clamps the mold, and measures the flow. An injection process for injecting and filling the moldable material into the mold, a solidifying process for solidifying the moldable material in the mold (for example, a cooling process), a mold opening process for opening the mold, and A take-out process (for example, an extrusion process) for taking out a molded product from the mold is sequentially performed, and after the solidification process is started and before the injection process is started, melting and mixing are performed according to the molding material. And a weighing step for weighing the molding material in a flowable state (for example, in the case of a thermoplastic resin material, a plasticizing weighing step) is simultaneously performed. Also, the molding material used includes various molding materials such as a thermoplastic resin material, a thermosetting resin material, a metal material, and a liquid resin material.

  For example, an injection device of a plastic injection molding machine that injection-molds a thermoplastic resin material is an in-line screw type injection device that plasticizes and melts a resin material and injection-fills the molten resin with a single in-line screw. It is roughly classified into a screw pre-plastic injection device in which a plasticizing unit for plasticizing and melting a resin material with a plasticizing screw and an injection unit for injecting and filling the molten resin with an injection plunger are separately provided. In the present specification, the in-line screw and the injection plunger are collectively referred to as “injection shaft”. The screw preplar type injection device does not need to have a check ring for backflow prevention on the injection shaft, so there is no variation in the measurement of the molten resin due to a delay in closing the ring, and the measurement accuracy is good.

  An injection device of such an injection molding machine includes an injection cylinder, an injection shaft that moves forward and backward in a cylinder hole of the injection cylinder, an injection nozzle that communicates with the cylinder hole and is fixed to the front portion of the injection cylinder, An injection chamber formed in front of the tip end surface of the injection shaft in the cylinder hole, an injection shaft drive device composed of an actuator such as electric or hydraulic that moves the injection shaft forward and backward, and injection control for controlling the injection shaft drive device An injection shaft position detection device that detects the position where the injection shaft moves forward and backward and outputs it to the injection control device, and detects the pressure of the molten resin supplied and stored in the injection chamber of the injection cylinder An injection pressure detecting device for outputting to the device. Therefore, in the injection apparatus, the molten resin is stored while being measured in the injection chamber so that the injection shaft is retracted in the plasticizing and measuring process, and then the injection shaft is advanced and pushed out in the injection process. Injection filling from the nozzle into the mold.

  The injection process is generally divided into a filling process and a pressure-holding process. In the filling process, after most of the molten resin required for one molding is filled in the mold, A gate adjacent to the product part of the cavity space in the mold, as well as filling the molten resin that is insufficient in the mold, including heat shrinkage caused by cooling of the molten resin filled in the mold A holding pressure is applied to the molten resin in the mold until part of the molten resin is solidified to prevent backflow. When the injection shaft that advances in the filling process reaches a predetermined VP switching position, the filling process is switched to the pressure holding process.

  In the filling process of the injection process, a reproducible injection speed so that the amount of molten resin flowing into the mold is approximately the same for each molding cycle with respect to the time elapsed from the start of the filling process. Control is often given priority. The injection speed can be determined by, for example, detecting the distance that the injection axis moves for each predetermined sampling period using an injection axis position detection device and dividing the distance detected for each sampling period by the time of the sampling period. Calculated as the actual speed. In the injection control device, the injection axis is determined according to the difference between the actual value of the injection speed calculated from the output from the injection axis position detection device and the setting value of the injection speed stored in advance in the set value storage unit for each sampling period. A command value for controlling the drive device is calculated, the command value is output to the injection shaft drive device, and feedback control is performed so that the actually measured value of the injection speed becomes the set value. The injection shaft driving device controlled with priority on the injection speed generates an injection pressure that resists the pressure received from the molding material filled in the mold at the desired injection speed.

  In the filling process in which feedback control is performed at the injection speed, the injection pressure required to generate the desired injection speed within the range of pressure that does not exceed the preset upper limit pressure without basically controlling by the injection pressure. When the injection pressure detection device tries to output the injection pressure exceeding the preset upper limit pressure, the output is limited to the upper limit pressure. The injection pressure exceeding the pressure is not output. Note that when an injection pressure exceeding the upper limit pressure is required, a desired injection speed cannot be generated.

  For example, Patent Document 1 discloses a feedback control device for an injection molding machine that performs feedback control by a PID (comparison / integration / differentiation) operation.

Japanese Patent Publication No. 08-015751

  However, in the conventional filling process, even if feedback control is performed based on the injection speed, the measured value of the injection speed is measured as the filling operation proceeds in the process from before the completion of the filling process to the completion of the process. Cannot reach the set value, and the measured value of the injection speed is decelerated from the set value.

  This is because, for example, if a thermoplastic resin is used in the cavity space in the mold, the viscosity gradually increases due to temperature change in the process of filling the molding material into the cavity space. As the mold is deprived of heat in order from the filled molding material, the viscosity gradually increases and the resistance when the molding material flows through the cavity space gradually increases, so the molding material becomes the mold. This is because it gradually becomes difficult to flow in the cavity space as the inside is filled. In addition, generally, the cavity space in the mold is connected in the order of the sprue part, the runner part, the gate part, and the product part, and the molding material is formed to have a relatively larger cross-sectional area than the others. Flow through the sprue part and runner part in turn, then flow through the gate part with a small cross-sectional area so as to narrow the flow path, and finally flow into the product part formed in a complicated shape. Tends to increase in the second half of the filling process, and gradually flows through the cavity space as the molding material is filled into the mold. This is also due to the tendency to become difficult to perform. Furthermore, the conventional feedback control calculates the command value based on the difference between the measured value of the injection speed and the set value, that is, the injection shaft drive after the measured value of the injection speed deviates from the set value. This is also caused by controlling the apparatus to accelerate or decelerate the actual injection speed so that the actual value of the injection speed becomes the set value. Further, in the conventional feedback control based on the PID operation, the calculation of the proportional (P) operation is generally calculated by multiplying the difference between the actually measured injection speed and the set value by a gain coefficient. Therefore, compared with the rapid acceleration of injection speed per unit time immediately after the start of the filling process, the deceleration per unit time due to the viscosity of the molding material, etc., that is, the measured value of injection speed per unit time Since the difference between the set value and the set value is relatively small, the actual injection speed may not be able to follow the set value depending on the magnitude of the gain coefficient.

  Therefore, during the period from the completion of the filling process to the completion of the process, the actual injection speed is easy to decelerate and difficult to accelerate. Here, for example, if the gain coefficient of the proportional (P) operation in the PID operation of the feedback control is increased, the acceleration per unit time of the injection shaft driving device is increased as compared with the case where the gain coefficient is small. In other words, it is possible to obtain a high response characteristic, and the period during which the actual measured value of the injection speed can follow the set value can be extended from before the completion of the filling process to the completion of the process. However, overshooting due to the fact that the response characteristic of the injection speed to be controlled becomes excessive and the rise of the measured value of the injection speed is too sharp during a period when the actual injection speed is not easy to decelerate and difficult to accelerate. In some cases, control could become unstable, causing oscillation.

  The decrease in the injection speed before the completion of the filling process means that the injection speed of the molding material flowing to the end of the cavity space in the mold becomes slow, and the time from the start to the completion of the process becomes long. For example, if the molding material is a thermoplastic resin, the molten resin filled in the mold is deprived of heat by the mold over time, the temperature decreases, and the viscosity further increases, and the filling process Even if the pressure holding process is performed after that, the molten resin is less likely to fill up to the corner of the product in the cavity space, causing short shots, or the ends of the molten resin that have entered the cavity space Can be one of the causes of forming defects such as generating weld lines without being sufficiently bonded.

  Therefore, in the injection apparatus and the injection control method of the present invention, in the filling process in which feedback control is performed at the injection speed, the measured value of the injection speed follows the set value immediately before the completion of the filling process under stable feedback control. It is an object of the present invention to shorten a period during which the vehicle stalls without making it possible to prevent molding defects such as short shots and weld lines.

In the injection control method for an injection device according to the present invention, an injection step of injecting and filling the molding material supplied and stored in the injection cylinder by moving the injection shaft in the injection cylinder forward and backward by the injection shaft driving device. among calculates a command value of the basic for controlling the injection drive unit based on the difference between the measured values of the injection speed to be sequentially detected with a set value of the injection speed which is stored in advance, the basic In the injection control method of the injection apparatus in which the filling step is performed by feedback control of the injection speed based on the command value of the injection shaft, the latest measured value of the latest injection pressure sequentially detected in the filling step And controlling the injection shaft driving device with a final command value obtained by adding a value calculated based on a difference between the measured value of the injection pressure and at least one previous injection pressure to the basic command value. You .

In the injection control method for an injection device according to the present invention, an injection step of injecting and filling the molding material supplied and stored in the injection cylinder by moving the injection shaft in the injection cylinder forward and backward by the injection shaft driving device. among calculates a command value of the basic for controlling the injection drive unit based on the difference between the measured values of the injection speed to be sequentially detected with a set value of the injection speed which is stored in advance, the basic In the injection control method of the injection apparatus in which the filling step is performed by feedback control of the injection speed based on the command value of the injection shaft, the latest measured value of the latest injection pressure sequentially detected in the filling step And controlling the injection shaft drive device with a final command value obtained by adding a value calculated on the basis of a difference between an average value of the actual measurement values of the plurality of injection pressures detected before and the basic command value. Features To.

  In the injection control method for an injection device according to the present invention, the feedback control may be one of control having only proportional control (P control only), or integral control and differential control in addition to the proportional control ( It may be a control having PI control or PD control) or both (PID control).

In the injection device of the present invention, an injection cylinder that stores a molding material, an injection shaft that moves at least in and out of the injection cylinder, an injection shaft driving device that moves the injection shaft back and forth, and a position of the injection shaft are detected. An injection shaft position detection device, an injection pressure detection device for detecting the pressure of the molding material in the injection cylinder, and a molding material supplied and stored in the injection cylinder are injected into the mold by moving the injection shaft. As the filling step of the filling step of filling, the injection shaft position detecting device when the injection shaft is moved and the set value of the injection speed composed of the moving speed of the injection shaft with respect to the position of the injection shaft stored in advance. The actual value of the injection speed consisting of the actual movement speed of the injection shaft, which is sequentially calculated based on the position of the injection shaft detected sequentially at the time and the movement time of the injection shaft timed at that time And it calculates a command value of the basis for controlling the injection shaft drive unit based on the difference between the measured values of the injection speed by controlling the injection shaft drive unit based on the command value of the basic When performing feedback control to follow the set value of the injection speed, it is detected at least one time before the latest measured value of the latest injection pressure sequentially detected from the injection pressure detector while the injection shaft is moving. An injection control device that outputs a final command value obtained by adding a value calculated based on a difference between the actual injection pressure value and the basic command value to the injection shaft driving device. To do.

In the injection device of the present invention, an injection cylinder that stores a molding material, an injection shaft that moves at least in and out of the injection cylinder, an injection shaft driving device that moves the injection shaft back and forth, and a position of the injection shaft are detected. An injection shaft position detection device, an injection pressure detection device for detecting the pressure of the molding material in the injection cylinder, and a molding material supplied and stored in the injection cylinder are injected into the mold by moving the injection shaft. As the filling step of the filling step of filling, the injection shaft position detecting device when the injection shaft is moved and the set value of the injection speed composed of the moving speed of the injection shaft with respect to the position of the injection shaft stored in advance. The actual value of the injection speed consisting of the actual movement speed of the injection shaft, which is sequentially calculated based on the position of the injection shaft detected sequentially at the time and the movement time of the injection shaft timed at that time And it calculates a command value of the basis for controlling the injection shaft drive unit based on the difference between the measured values of the injection speed by controlling the injection shaft drive unit based on the command value of the basic When performing feedback control to follow the set value of the injection speed, the latest measured value of the latest injection pressure sequentially detected from the injection pressure detection device while the injection shaft is moving, and the value detected before that An injection control device that outputs a final command value obtained by adding a value calculated based on a difference between an average value of measured values of a plurality of injection pressures to the basic command value to the injection shaft driving device; It is characterized by having.

  In the injection apparatus of the present invention, the feedback control is either a control having only proportional control (P control only) or one of integral control and differential control in addition to the proportional control (PI control or PD control). Control) or control having both of them (PID control).

  According to the injection device and the injection control method of the present invention, in the filling process in which feedback control is performed at the injection speed, only when the injection pressure change is detected and the injection pressure changes, a value corresponding to the change is obtained by feedback control. By adding to the calculated command value, it is possible to suppress the actual value of the injection speed from decelerating without following the set value from before the completion of the filling process under stable feedback control. In addition, molding defects such as short shots and weld lines can be prevented.

It is a block diagram which shows the embodiment of the injection apparatus of this invention, and its injection control method. Each measured waveform showing the injection speed, injection pressure, and command value based on the position of the injection shaft after the molding material becomes difficult to flow before the filling step in the injection device and the injection control method of the present invention and the prior art is completed. It is the main part of the graph shown in contrast with the past. It is a graph which shows each measured waveform which shows the injection speed and injection pressure of a filling process in the injection device of the present invention and a prior art, and its injection control method based on the position of an injection axis in contrast with the past. It is a graph which shows each measured waveform which shows injection speed and injection pressure of a filling process in an injection device of the present invention and a prior art, and its injection control method based on time in comparison with the past. It is the schematic which shows the injection apparatus of this invention by making a screw prep plastic type injection apparatus into an example.

  First, a conventionally known portion of the injection apparatus will be briefly described with reference to a schematic diagram shown in FIG. 5 by taking a screw pre-plastic injection apparatus for injection molding a thermoplastic resin material as an example.

  In the injection apparatus 1 shown in FIG. 5, a plasticizing unit 2 that plasticizes and melts a resin material 8 that is a molding material, and a molten resin material 8 (hereinafter referred to as a molten resin 8) in a mold 10. An injection unit 3 for injection filling toward the cavity space 11 is provided separately, and these are connected by a connecting member 4 having a communication path 4 a for the molten resin 8. The communication path 4a can be opened and closed by a backflow prevention device 4b such as an on-off valve. A heater (not shown) may be wound around the plasticizing cylinder 20, the injection cylinder 30, the injection nozzle 32, and the connecting member 4. The mold 10 is mounted on a mold clamping device (not shown). In addition, the mold 10 may be provided with a pipe through which a medium flows in order to adjust the temperature (not shown). The cavity space 11 in the mold 10 shown in FIG. 5 includes a sprue portion 11a, a runner portion 11b, a gate portion 11c, and a product portion 11d in this order from the injection nozzle 32 of the injection cylinder 30.

  The plasticizing unit 2 includes at least a plasticizing cylinder 20, a plasticizing screw 21 in the plasticizing cylinder 20, and a rotation drive device 22 that rotates the plasticizing screw 21. A hopper 7 for supplying the resin material 8 is attached to the plasticizing cylinder 20.

  The injection unit 3 includes an injection cylinder 30, an injection nozzle 32 fixed to the front end of the injection cylinder 30, an injection plunger 31 serving as an injection shaft 31 that advances and retreats within the injection cylinder 30, and an injection shaft drive device that advances and retracts the injection plunger 31. 50, an injection shaft position detecting device 61 for detecting the position of the injection plunger 31, an injection pressure detecting device 62 for detecting the pressure of the molding material 8 in the injection cylinder 30, and an injection for controlling the injection shaft driving device 50. And at least a control device 60. The injection shaft driving device 50 of the injection unit 3 shown in FIG. 5 shows an example of a configuration that enables the injection filling with high response at high speed by including the accumulator 58 and the servo valve 52.

  The injection shaft driving device 50 includes a hydraulic cylinder 51 including a piston 51a and a cylinder 51b, a servo valve 52, a hydraulic supply source 53, and an oil tank 59. The hydraulic supply source 53 is connected to a hydraulic pump 54, a pump motor 55 that drives the hydraulic pump 54, a filter 56 connected to the suction side of the hydraulic pump 54, and a discharge side of the hydraulic pump 54, and its discharge direction. A check valve 57 that allows only the flow of the gas, and an accumulator 58 connected to the discharge side of the check valve 57. In the injection shaft drive device 50 that drives the injection plunger 31 with the hydraulic cylinder 51, an accumulator 58 is provided in addition to the hydraulic pump 54 as the hydraulic supply source 53, and the hydraulic oil stored in the accumulator 58 in a large amount at a high pressure is collected at once. In addition to driving the injection plunger 31 at high speed, the servo valve 52 is disposed between the accumulator 58 and the hydraulic cylinder 51, and the hydraulic oil to the hydraulic cylinder 51 is controlled by controlling the drive of the servo valve 52. The injection plunger 31 can be driven with high response and high precision by adjusting the supply amount and supply direction.

  The servo valve 52 is a 4-port servo valve 52 having A, B, P, and T ports. The A port is connected to the rear oil chamber 51d (piston head side oil chamber) of the hydraulic cylinder 51, and the B port is connected to the front. Connected to the oil chamber 51 c (piston rod side oil chamber), the P port is connected to the accumulator 58, and the T port is connected to the oil tank 59. Although not shown in the drawings, the 4-port servo valve 52 has a cylindrical sleeve formed with A, B, P, and T ports. A spool that is displaced in the axial direction is accommodated in the A, B, P, and T ports. By moving the port, the connection between the ports is switched, the opening degree of each port (hereinafter referred to as the spool opening degree) is varied to adjust the flow rate, and the opening of each port is closed to open the port. It is designed to shut off. The spool opening is controlled so as to be directly proportional to the voltage value that is output from the injection control device 60 and that is a command signal (hereinafter referred to as a command value Qr) that is input to the command value input unit 52a of the 4-port servo valve 52. The Depending on the configuration of the injection device 1, the spool opening may be controlled to be directly proportional to the current value, not the voltage value.

  For example, in the 4-port servo valve shown in FIG. 5, when the voltage value that is the command value Qr is zero, the spool is in a neutral position, that is, in a state where all the ports are shut off, the voltage value is a positive value. When the P port is connected to the A port, the hydraulic oil is supplied from the hydraulic supply source 53 to the rear oil chamber 51d of the hydraulic cylinder 51, and the T port is connected to the B port of the front oil chamber 51c of the hydraulic cylinder 51. When the hydraulic oil is returned to the oil tank 59 and the voltage value is a negative value, the T port is connected to the B port, and the hydraulic oil is supplied from the hydraulic supply source 53 to the front oil chamber 51c of the hydraulic cylinder 51. At the same time, the T port is connected to the A port, and the hydraulic oil in the rear oil chamber 51 d of the hydraulic cylinder 51 is returned to the oil tank 59. For example, the spool opening degree is set so that the flow rate of hydraulic oil per unit time flowing from the hydraulic supply source 53 to the rear oil chamber 51d from the hydraulic cylinder 51 increases as the voltage value serving as the command value increases from zero to the positive direction. And the speed at which the injection plunger 31 moves, that is, the injection speed V increases. Incidentally, the unit time that flows from the hydraulic supply source 53 to the front oil chamber 51c of the hydraulic cylinder 51 as the voltage value that becomes the command value Qr decreases in the negative direction from zero, that is, as the absolute value of the negative voltage value increases. The spool opening increases so that the flow rate of the working hydraulic fluid increases, the retraction speed of the injection plunger 31 increases, and the high-pressure hydraulic fluid in the rear oil chamber 51d of the hydraulic cylinder 51 is discharged at high speed after injection filling. It also becomes. Note that the neutral position of the spool is not always zero as in the present embodiment, and may be on either the positive or negative side of the voltage value. Further, the direction in which the spool moves with respect to the positive or negative voltage value may be opposite to that of the present embodiment.

  The injection control device 60 is connected to the command value input part 52a of the 4-port servo valve 52 on the output side, and the pressure in the rear oil chamber 51d of the hydraulic cylinder 51, that is, the injection plunger 31 gives the molten resin 8 to the input side. An injection pressure detection device 62 for detecting an actual measurement value of the injection pressure P is connected. The injection pressure detecting device 62 includes a load cell sandwiched between the injection plunger 31 and the piston rod, a pressure center attached to the tip of the injection plunger 31, or a pressure center attached to a part of a cavity space in a mold such as a sprue. Etc. An injection shaft position detection device 61 that detects an actual measurement value of the position S of the injection plunger 31 is connected to the input side of the injection control device 60. The injection shaft position detecting device 61 can employ various position detecting sensors such as a linear encoder. Here, what is expressed as the position S of the injection shaft 31 is the tip position S of the injection plunger 31 that becomes the injection shaft 31 in a strict sense. The actual measurement value of the injection speed V is sampled by the injection control device 60 that inputs the actual measurement value of the position S sequentially sent from the injection shaft position detection device 61 that detects the forward movement position S of the injection plunger 31 at every predetermined sampling period. It may be detected by a method of converting from the distance moved by the injection plunger 31 at the time t of the cycle to the speed data V. The injection control device 60 may be incorporated in a part of the function of a controller (not shown) that controls various controls of the injection molding machine including the injection device 1. The injection control device may also control the pressure holding process in addition to controlling the filling process of the injection process.

  In the injection device 1 as described above, the injection control device 60 sends the command value input unit 52a of the 4-port servo valve 52 to the command value input unit 52a based on various molding conditions including the set values such as the injection speed V or the injection pressure P set by the operator. The command value Qr is output, the injection plunger 31 is driven via the 4-port servo valve 52, that is, the position in the sleeve of the spool is adjusted by feedback control, and the molten resin 8 is moved into the cavity space 11 in the mold 10. Injection filling. The command value output from the injection control device 60 may be input to the command value input unit 52a of the 4-port servo valve 52 via a D / A converter or a driver circuit (not shown), or the command value input unit 52a. May include a D / A converter and a driver circuit (not shown).

  Next, a general injection control method of the injection apparatus 1 will be described. In the injection control method, the injection process includes a filling process and a pressure holding process, and the drive of the injection plunger 31 is controlled via the servo mechanism by the feedback control described above in each process. In the injection process, the injection speed V is controlled mainly with respect to the position S of the injection plunger 31 in the filling process, and the holding pressure is controlled with respect to the pressure holding time in the pressure holding process that continues across the VP switching position or VP switching time. doing. In the filling process, feedback control is performed based on the injection speed V. In the pressure holding process, feedback control is performed based on the holding pressure. In the feedback control, for example, a conventionally known PID operation, P operation, PI operation, and PD operation are performed.

  From here, the configuration of the injection device 1 and the injection control method of the injection device 1 according to the present invention will be described by taking the embodiment shown in FIGS. 1 to 4 as an example.

  As in the embodiment shown in the block diagram of FIG. 1 and the graph of FIG. 2, the injection control device of the injection device 1 of the present invention has n = 0, 1, 2 every sampling period t in the filling step of the injection step. 3,..., N, an actual injection velocity value Vr (n) obtained by converting actual position data Sr (n) of the injection plunger 31 detected by the injection shaft position detector 61 into velocity data, and a set value. The basic command value Qf (n) is obtained by performing feedback control based on the calculation based on the PID operation in the PID control unit 60a based on the difference between the injection speed set value Vs (n) stored in the storage unit 60b. Further, the latest measured value Pr (n) of the latest injection pressure P sequentially detected by the injection pressure detecting device 62 and the immediately previous value detected immediately before and stored in the measured value storage unit 60c. Measured value Pr (n-1) Difference Δp (n) = Δp1, Δp2, Δp3,..., Δp11, Δp12, Δp13,..., Δp (n) q (n) = q1, q2, q3,. ..., Q11, q12, q13,..., Q (n) are added to output a final command value Qr (n) = Qf (n) + q (n) to control the injection shaft driving device. Note that ΔP is preferably the difference between the latest measured value Pr (n) of the latest injection pressure detected in the same filling step and the measured value Pr (n−1) of the previous injection pressure. Detected in the same filling process, such as the difference between the latest measured value Pr (n) of the latest injection pressure detected in the same filling process and the actual measured value Pr (n-2) of the previous injection pressure. It may be a difference between the latest measured value Pr (n) of the latest injection pressure and the actually measured value Pr (nm) of the injection pressure detected m times before. ΔP is the latest measured value Pr (n) of the latest injection pressure detected in the same filling process and the measured value of the injection pressure detected before the latest measured value Pr (n) of the latest injection pressure. It may be a difference from an average value obtained by averaging a plurality of times of Pr (n−m). For example, the latest measured value Pr (n) of the latest injection pressure detected in the same filling process and the latest injection An average value (= Pr (n−m) of a plurality of injection pressure actual values Pr (n−1), Pr (n−2),..., Pr (n−m) detected before the actual pressure value Pr (n). (Pr (n-1) + Pr (n-2) +... + Pr (nm)) / m).

  For example, in the embodiment of FIG. 1, the command value Qr (n) = Qf (n) + k · (Pr (n) −Pr (n−1)) = Qf (n) + k · Δp (n) = Qf ( n) + q (n). Here, in the embodiment of FIG. 1, the above-mentioned value q (n) is calculated by multiplying Δp (n) by a constant k (the above-mentioned value q (n) = k · Δp ( n)). If the basic command value Qf (n) calculated from the PID control unit 60a is converted into a voltage value, for example, it is used to convert the magnitude of Δp (n) based on the injection pressure P into a voltage value. Moreover, it is also used to adjust the response characteristic of the command value Qr (n) per unit time based on Δp (n), and it is preferable to adjust appropriately. Further, the conversion and adjustment are not limited to the constant k, and conversion and adjustment may be performed by substituting Δp (n) into a predetermined function.

  In the injection device and the injection control method of the present invention, for example, the injection speed set value Vs (n) from the start of the filling process (measurement completion position) to the completion of the filling process (VP switching position or VP switching time). As shown in FIG. 2 to FIG. 4 with a constant value), conventionally, the measured value Va (n) of the injection speed can follow the set value Vs (n) from before the filling process until the completion of the process. Even in a section where the vehicle is decelerating without delay, in the present invention, the actually measured value Vr (n) of the injection speed can be made to follow the set value Vs (n) and decelerate without being able to follow the set value Vs (n). Can be shortened.

  In the graph shown in FIG. 2, in the embodiment where the actual measured value Va of the conventional injection speed starts to decelerate before the completion of the filling process, the measured value Vr of the injection speed follows the set value Vs in the embodiment of the present invention. FIG. 6 is a graph showing a state in which deceleration is possible, and for a part of the position S of the injection shaft 31, the injection speed setting value Vs, the conventional injection speed actual measurement value Va (dashed line), and the injection in the present invention Actual measurement value Vr (solid line), conventional injection pressure measurement value Pa (one-dot chain line), actual injection pressure measurement value (solid line) in the present invention, conventional command value Qa (one-dot chain line), command value Qr of the present invention (Solid line) and basic command value Qf (dotted line) in the PID operation of the present invention are shown. In the graph shown in FIG. 2, the horizontal axis is the position S of the injection shaft 31, and the conventional graph and the graph of the present invention are contrasted, and the measured value Va of the injection speed cannot follow the set value Vs and decelerate. In comparison with the graph of the present invention, since the distance of the ejection axis 31 that can move at the same sampling period t is shorter than that of the graph of the present invention, the conventional graph is shifted from the conventional sampling period t and the present invention. .

  In the graphs shown in FIGS. 3 and 4, from the start of the filling process (measurement completion position) to the completion of the filling process (VP switching position or VP switching time), FIG. 3 shows the position S of the injection shaft 31. In FIG. 4, the horizontal axis represents the time T, the injection speed setting value Vs, the conventional injection speed measurement value Va (dashed line), the injection speed measurement value Vr (solid line) in the present invention, and the conventional injection pressure. The actual measurement value Pa (one-dot chain line) and the actual measurement value (solid line) of the injection pressure in the present invention are shown. For example, in the case of the present invention, the period during which the actual measured value Vr of the injection speed decelerates without following the set value Vs is shorter than in the conventional case, so that the time from the start to the completion of the filling process as shown in FIG. Since the elapsed time from the start of the filling process is shorter than the conventional case even at the same position S of the injection shaft 31 as shown in FIG. 3, the molding material is shorter than the conventional case. The increase in the viscosity is small, and the injection pressure Pr of the present invention is kept smaller than the conventional injection pressure Pa.

  The final command value Qr shown in FIG. 2 is, for example, when the timing of the sampling period t after the injection pressure Pr rises, at the injection pressure p11 at that time and the sampling period t immediately before that. A difference Δp11 (= p11−p10) from the previous injection pressure p10 is calculated, and a value q11 (= k · Δp11) obtained by multiplying the difference Δp11 by a constant k is calculated and calculated from the PID control unit 60a. A final command value Qr11 (= Qf11 + q11) is calculated by adding the value q11 to the basic command value Qf11. Therefore, the injection shaft driving device 50 is controlled by the command value Qr11 output from the injection control device, and does not decelerate the actual measured value Vr of the injection speed compared to the actual measured value Va of the conventional injection speed. It is possible to follow the set value Vs. Next, when the timing of the sampling period t comes again, a difference Δp12 (= p12−p11) between the injection pressure p12 at that time and the immediately preceding injection pressure p11 in the immediately preceding sampling period t is calculated. A value q12 (= k · Δp12) obtained by multiplying the difference Δp12 by a constant k is calculated, and a final command value Qr12 (= Qf12 + q12) obtained by adding the value q12 to the basic command value Qf12 calculated from the PID control unit 60a is calculated. Has been. Therefore, the injection shaft driving device 50 is controlled by the command value Qr12 output from the injection control device 60 from the state of the actual measured value Vr of the injection speed larger than the actual measured value Va of the conventional injection speed. It is possible to accelerate the injection speed actual measurement value Vr to be larger than the speed actual measurement value Va so as to follow the injection speed setting value Vs. Next, when the timing of the sampling cycle t comes again, a difference Δp13 (= p13−p12) between the injection pressure p13 at that time and the immediately preceding injection pressure p11 in the immediately preceding sampling cycle t is calculated. A value q13 (= k · Δp13) obtained by multiplying the difference Δp13 by a constant k is calculated, and a final command value Qr13 (= Qf13 + q13) obtained by adding the value q13 to the basic command value Qf13 calculated from the PID control unit 60a is calculated. Has been. The injection shaft driving device 50 is controlled by the command value Qr13 output from the injection control device 60 from the state of the actual measured value Vr of the injection speed larger than the actual measured value Va of the conventional injection speed. The actually measured value Vr can be made to follow the set value Vs of the injection speed without decelerating compared to the conventional measured value Va of the injection speed. Here, even if the conventional command value Qa is larger than the final command value Qr of the present invention, the actual measured value Va of the conventional injection speed that has been greatly decelerated from the set value Vs of the injection speed is set as the injection speed. It does not lead to a large acceleration to the value Vs.

  In the injection device 1 and the injection control method thereof according to the present invention, in particular, it is detected by the increase in the injection pressure Pr that the molten resin 8 starts to hardly flow from before the completion of the filling step, and at a predetermined sampling cycle t every n. As the amount by which the injection pressure Pr rises, that is, the amount by which the driving force of the injection shaft driving device 50 necessary for maintaining the measured value Vr of the injection speed at the set value Vs becomes larger than the driving force so far, Δp By using the command value Qr (n) which is added by the value q (n) calculated based on (n) and becomes larger than the basic command value Qf (n) in the conventional PID operation, for example, It becomes possible to open the spool opening of the servo valve 52 larger than before, and it is possible to suppress the deceleration of the actually measured value Vr of the injection speed.

  Further, in the present invention, since the actual value Pr of the injection pressure starts to rise before the filling process, the actual value Vr of the injection speed follows the set value Vs for a while without decelerating. However, the filling process can be advanced while the viscosity of the molten resin 8 is small, and the higher the speed before the acceleration of the injection speed is, the more difficult it is to slow down. Compared with the conventional feedback control that decelerates from the value Vs, the injection device 1 and the injection control method of the present invention can make the actually measured value Vr of the injection speed follow the set value Vs. Note that the timing at which the measured value Pr of the injection pressure increases is not necessarily from before the completion of the filling process to the completion of the process, but Δp with the increase in the measured value Pr of the injection pressure at other times is compared. Therefore, the influence on the feedback control is small. Further, if the measured value Pr of the injection pressure does not change and is maintained at a constant pressure, ΔP becomes zero, and the final command value Qr becomes the basic command value Qf in the PID control unit 60a.

  INDUSTRIAL APPLICABILITY The present invention can be used for an injection device of various injection molding machines such as a plastic injection molding machine and a light metal injection molding machine that obtain a molded product by injecting and filling a molding material such as resin and metal into a mold and an injection control method thereof. In particular, the present invention can be used for an injection control method in a filling process in which the injection speed in the injection process is controlled with priority. According to the present invention, molding defects such as short shots and weld lines can be prevented, contributing to the development of injection molding machines and injection molding techniques.

DESCRIPTION OF SYMBOLS 1 Injection apparatus 2 Plasticization unit 3 Injection unit 4 Connecting member 4a Communication path 4b Backflow prevention apparatus 7 Hopper 8 Molding material 10 Mold 11 Cavity space 11a Sprue part 11b Runner part 11c Gate part 11d Product part 20 Plasticizing cylinder 21 Plasticization Screw 22 Rotation drive device 30 Injection cylinder 31 Injection plunger (injection shaft)
32 Injection nozzle 50 Injection shaft drive device 51 Hydraulic cylinder 51a Piston 51b Cylinder 51c Front oil chamber 51d Rear oil chamber 52 Servo valve 52a Command value input unit 53 Hydraulic supply source 54 Hydraulic pump 55 Pump motor 56 Filter 57 Check valve 58 Accumulator 59 Oil tank 60 Injection control device 60a PID control unit 60b Set value storage unit 60c Actual measurement value storage unit 61 Injection shaft position detection device 62 Injection pressure detection device

Claims (6)

The injection speed stored in advance during the injection process of injecting and filling the molding material supplied and stored in the injection cylinder by moving the injection shaft in the injection cylinder forward and backward by the injection shaft driving device The basic command value for controlling the injection driving device is calculated based on the difference between the set value of the injection value and the actually measured value of the injection speed that is sequentially detected, and the moving speed of the injection shaft is calculated based on the basic command value. In an injection control method of an injection device in which a filling step is performed by feedback control of the injection speed consisting of:
A value calculated based on the difference between the latest measured value of the injection pressure sequentially detected in the filling step and the measured value of the injection pressure detected at least one time before is added to the basic command value. An injection control method for an injection device, wherein the injection shaft drive device is controlled with a final command value. The injection speed stored in advance during the injection process of injecting and filling the molding material supplied and stored in the injection cylinder by moving the injection shaft in the injection cylinder forward and backward by the injection shaft driving device The basic command value for controlling the injection driving device is calculated based on the difference between the set value of the injection value and the actually measured value of the injection speed that is sequentially detected, and the moving speed of the injection shaft is calculated based on the basic command value. In an injection control method of an injection device in which a filling step is performed by feedback control of the injection speed consisting of:
A value calculated based on the difference between the latest measured value of the latest injection pressure sequentially detected in the filling step and the average value of the actually measured values of a plurality of injection pressures detected before that is used as the basic command value. An injection control method for an injection device, wherein the injection shaft drive device is controlled by a final command value added.   The feedback control is control having only proportional control (P control only), or one of integral control and differential control (PI control or PD control) or both (PID control) in addition to the proportional control. The injection control method for an injection apparatus according to claim 1, wherein the injection control method includes: An injection cylinder for storing the molding material;
An injection shaft that moves forward and backward at least in the injection cylinder;
An injection shaft driving device for moving the injection shaft forward and backward, and
An injection axis position detection device for detecting the position of the injection axis;
An injection pressure detecting device for detecting the pressure of the molding material in the injection cylinder;
The injection shaft with respect to the position of the injection shaft stored in advance as a filling step of the injection step of injecting and filling the mold with the molding material supplied and stored in the injection cylinder by moving the injection shaft Sequentially based on the set value of the injection speed composed of the moving speed of the injection shaft, the position of the injection shaft sequentially detected by the injection shaft position detecting device when the injection shaft moves, and the movement time of the injection shaft timed at that time and calculates a command value of the basis for controlling the injection shaft drive unit based on the difference between the actual measured value of the injection speed comprising a moving speed of the injection axis is calculated, the command value of the basic Based on the control of the injection pressure detecting device while the injection shaft is moving, feedback control is performed to control the injection shaft driving device to cause the measured value of the injection velocity to follow the set value of the injection velocity. Sequentially detected by the final command value a value calculated based on the difference was added to the command value of the basic between the latest measured values and the measured values of the injection pressure detected in the at least one previous injection pressure An injection control device for outputting to the injection shaft driving device;
An injection apparatus characterized by having at least. An injection cylinder for storing the molding material;
An injection shaft that moves forward and backward at least in the injection cylinder;
An injection shaft driving device for moving the injection shaft forward and backward, and
An injection axis position detection device for detecting the position of the injection axis;
An injection pressure detecting device for detecting the pressure of the molding material in the injection cylinder;
The injection shaft with respect to the position of the injection shaft stored in advance as a filling step of the injection step of injecting and filling the mold with the molding material supplied and stored in the injection cylinder by moving the injection shaft Sequentially based on the set value of the injection speed composed of the moving speed of the injection shaft, the position of the injection shaft sequentially detected by the injection shaft position detecting device when the injection shaft moves, and the movement time of the injection shaft timed at that time and calculates a command value of the basis for controlling the injection shaft drive unit based on the difference between the actual measured value of the injection speed comprising a moving speed of the injection axis is calculated, the command value of the basic Based on the control of the injection pressure detecting device while the injection shaft is moving, feedback control is performed to control the injection shaft driving device to cause the measured value of the injection velocity to follow the set value of the injection velocity. The measured values of the latest injection pressure being sequentially detected, adding a value calculated based on the difference between the average value of measured values of a plurality of injection pressure that were detected before the command value of the basic final An injection control device that outputs the command value to the injection shaft drive device;
An injection apparatus characterized by having at least.   The feedback control is a control having only proportional control (P control only), or a control having one or both of integral control and differential control (PI control or PD control) in addition to the proportional control (PI control or PD control). 6. The injection apparatus according to claim 4, wherein the injection apparatus is PID control.

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