Injection device and injection method

Abstract

To provide an injection apparatus capable of preventing occurrence of galling on an outer circumferential surface of a screw by avoiding rotation speed of the screw being set too high, or by avoiding back pressure of the screw being set too low.SOLUTION: An injection apparatus 1 according to the present invention comprises: an injection part 30 having a cylinder-shaped cylinder 33 and a screw 31 rotatably disposed in the cylinder 33; an electric motor 23 for driving to rotate the screw 31; and a controller 40 for controlling operation of the electric motor 23. The controller 40 according to the present invention allows rotation speed of the screw and the back pressure of the screw to correspond to each other to limit setting range of one or both of the rotation speed of the screw and the back pressure of the screw in a plasticizing step.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to controlling the operation of a plasticizing screw. [Background technology]

[0002] A typical injection device supplies raw resin pellets from the rear side of a cylinder, and melts the raw resin by applying shear force through the rotation of the screw while heating the raw resin inside the cylinder. The molten resin is measured inside the cylinder and injected into a cavity formed inside a mold from an injection nozzle attached to the front end of the cylinder.

[0003] Patent Document 1 provides an injection device that can appropriately adjust the temperature profile of the cylinder based on the molded product and molding cycle time. According to Patent Document 1, it is possible to adjust the degree of heating of the molding material in the cylinder, preventing deterioration of the molding material due to heating and preventing galling.

[0004] In Patent Document 1, the larger the dimensions of the molded product or the shorter the molding cycle time, the faster the raw resin moves inside the cylinder, and the shorter the time it receives heat from the cylinder, so a larger amount of heat is given to the resin from the base side, i.e., the side where the raw resin is introduced. For this reason, Patent Document 1 shows an example in which the temperature of the heater on the base side of the cylinder is automatically set high to prevent variations in metering time and galling on the outer periphery of the screw. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2007 / 105646 Summary of the Invention [Problem to be solved by the invention]

[0006] The screw rotation speed and the back pressure the screw receives from the molten resin during the plasticization process are set by the operator of the injection machine. However, operators may set the screw rotation speed too high or the screw back pressure too low, close to the minimum pressure. This increases the resin's movement speed within the cylinder, shortening the time the resin receives heat from the cylinder. In this case, the cylinder is unable to sufficiently heat the resin, and the solid raw resin mass, which is not yet fully melted, is forced into the shallow groove, which is the compression section of the screw. This causes a wedge action of the solid resin mass inside the screw groove, forcing the screw firmly against the inner circumferential surface of the cylinder on the opposite side of the wedge. If the screw continues to rotate in this state, galling may occur on the outer circumferential surface of the screw.

[0007] Therefore, an object of the present invention is to provide an injection device that can prevent galling from occurring on the outer peripheral surface of the screw by avoiding setting the screw rotation speed too high or avoiding setting the screw back pressure too low. [Means for solving the problem]

[0008] The injection device of the present invention includes an injection unit having a cylindrical cylinder and a screw rotatably arranged in the cylinder, a rotation mechanism that rotates the screw, and a control unit that controls the operation of the rotation mechanism. The control unit of the present invention correlates the screw rotation speed and the screw back pressure with each other, and limits the setting range of one or both of the screw rotation speed and the screw back pressure in the plasticizing step.

[0009] The control unit of the present invention preferably specifies, as the set range, one or both of a back pressure lower limit value that is the lower limit of the back pressure received by the screw and a rotation speed upper limit value that is the upper limit of the rotation speed of the screw.

[0010] The control unit of the present invention preferably compares the input screw set rotation speed candidate with one or more screw rotation speed ranges pre-stored in the control unit, and if the input set rotation speed candidate is included in the stored screw rotation speed range, identifies the back pressure lower limit value associated with that screw rotation speed range as the back pressure lower limit value of the set range, and does not accept set back pressure candidates smaller than that lower limit value.

[0011] The control unit of the present invention preferably compares the input screw set back pressure candidate with one or more screw back pressure value ranges pre-stored in the control unit, and if the input set back pressure candidate is included in the stored screw back pressure value range, identifies the upper limit of the rotation speed corresponding to that screw back pressure value range as the upper limit of the rotation speed of the set range, and does not accept set rotation speed candidates greater than that upper limit.

[0012] The control unit of the present invention preferably specifies the backpressure lower limit value and the rotation speed upper limit value using one or both of a first equation showing the correlation between the input screw set backpressure candidate and the backpressure lower limit value, and a second equation showing the correlation between the input screw set backpressure candidate and the rotation speed upper limit value, and does not accept input of one or both of a set backpressure candidate smaller than the backpressure lower limit value and a set rotation speed candidate larger than the rotation speed upper limit value.

[0013] The control unit of the present invention preferably announces that it will not accept input of either or both of a set back pressure candidate that is smaller than the back pressure lower limit value and a set rotation candidate that is larger than the rotation speed upper limit value, and will prompt the user to input a new set back pressure candidate in place of the set back pressure candidate, and will prompt the user to input a new set rotation speed candidate in place of the set rotation speed candidate.

[0014] The present invention provides an injection method in which the screw rotation speed and screw back pressure in the plasticization step, which are the plasticization conditions of the injection device, are made to correspond to each other, thereby limiting the setting range of the screw rotation speed or back pressure. [Effects of the Invention]

[0015] The injection device of the present invention corresponds the screw rotation speed and the screw back pressure to each other, and limits the setting range of one or both of the screw rotation speed and the screw back pressure in the plasticization process. As a result, the injection device of the present invention can prevent the occurrence of galling on the outer peripheral surface of the screw by avoiding setting the screw rotation speed too high or the screw back pressure too low. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a side view showing a schematic configuration of an injection device according to an embodiment of the present invention. [Figure 2] The data stored in the memory unit of the injection device in Figure 1 are shown, where (a) shows the screw rotation speed range during the plasticization process and the corresponding lower limit of the back pressure, and (b) shows the back pressure range during the plasticization process and the corresponding upper limit of the screw rotation speed. [Figure 3] FIG. 2 is a flow chart showing an example of a procedure from when the set rotation speed and set back pressure in the injection device of FIG. 1 are determined, to when the screw starts to rotate, and until the plasticization step begins. [Figure 4] 4 is a flowchart showing an example of a procedure for determining a candidate set rotation speed (SR0) in the flowchart of FIG. 3. FIG. [Figure 5] FIG. 4 is a flowchart showing an example of a procedure for determining a set back pressure candidate (BP0) in the flowchart of FIG. 3. [Figure 6] 2 shows examples of displays on the display unit of the control unit in FIG. 1, where (a) is an example of a display screen that prompts input of a candidate set rotation speed (SR0) and a candidate set back pressure (BP0), and (b) is an example of a display screen that is displayed when the input candidate set rotation speed (SR0) is inappropriate. [Figure 7] 10A and 10B are diagrams illustrating how the molten resin pushes the screw toward the rear end in the plasticization process of the in-line injection device. [Figure 8] 10A and 10B are diagrams illustrating another force exerted by molten resin on the screw in the rear end direction in the plasticization process of the in-line injection device. [Figure 9]FIG. 2 is a side view showing a schematic configuration of an injection device to which the present embodiment is referred. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The injection unit 1 is combined with a mold clamping unit (not shown) to form an injection molding machine. The following steps are performed in order to obtain a molded product using the injection unit 1. The injection unit 1 according to this embodiment limits one or both of the setting ranges of the screw rotation speed and the screw back pressure in the following plasticization step. Clamping process: The movable and fixed molds that make up the clamping process are closed and clamped under high pressure. Plasticization process: The resin pellets are heated and melted inside the cylinder to plasticize them. Injection process: The plasticized molten resin is injected into the cavity formed by the movable and fixed molds, filling it. Pressure holding process: Pressure is applied to the molten resin filled in the cavity until it cools and solidifies. Mold opening process: The mold is opened. Removal process: The molded product that has cooled and solidified in the cavity is removed.

[0018] [Overall configuration of injection unit 1: Figure 1] 1, the injection device 1 includes a support unit 10, a drive unit 20 that is supported by the support unit 10 and that drives the forward and backward movement of the screw 31 and the rotation of the screw 31, and an injection unit 30 that includes the screw 31 and is involved in injecting the resin. The injection device 1 also includes a control unit 40 that controls the operation of the injection device 1. During the plasticization process, the injection device 1 can prevent galling from occurring on the outer peripheral surface 31S of the screw 31 by using the control unit 40 to limit the setting ranges for one or both of the screw rotation speed and the screw back pressure.

[0019] In the injection device 1, the side marked with F in Fig. 1 is defined as the front, and the side marked with B is defined as the rear. The definitions of the front F and the rear B include relative meanings. Furthermore, with respect to the injection device 1, a width direction W, a longitudinal direction L, and a vertical direction H are defined as shown in FIG.

[0020] [Support part 10: Figure 1] As shown in FIG. 1, the support unit 10 includes a bed 11 extending from the front F to the rear B, and a pair of guide rails 13 provided on the bed 11 on the rear B side of the bed 11. The pair of guide rails 13 are fixed onto the bed 11 with a gap between them in the width direction W. A movable housing 21 of a drive unit 20 (described later) is placed on the guide rails 13 so as to be slidable from the front F to the rear B and from the rear B to the front F. In this embodiment, as long as the movable housing 21 can be moved back and forth in the front-to-rear direction, the means for achieving this is not limited to the guide rails 13. As one example, a guide groove or guide wall can be provided at the position where the guide rails 13 are to be provided, and rollers or sliding plates that run along this guide can be provided on the movable housing 21.

[0021] [Drive unit 20: Figure 1] Next, the driving unit 20 will be described. As shown in FIG. 1, the drive unit 20 includes a movable housing 21 supported so as to be movable in the front-rear direction along the guide rail 13, and an electric motor 23 supported on the rear side B of the movable housing 21.

[0022] The movable housing 21 is movable from the front F to the rear B and from the rear B to the front F along the guide rail 13 by, for example, a piston-cylinder mechanism (not shown). The movable housing 21 accommodates therein a transmission mechanism such as a gear train and bearings that transmits the rotational motion of the electric motor 23 to the screw 31. A load cell (not shown) is interposed between the screw shaft 31B of the screw 31 and the movable housing 21, and is capable of detecting the load that the screw 31 receives in the axial direction. The back pressure of the screw 31 during the plasticizing process is controlled based on the load detected by the load cell. The electric motor 23 is rotated in response to instructions from the control unit 40. Although an electric motor 23 is used here, other rotary drive sources capable of outputting rotary drive force, such as a hydraulic motor, can also be used. Also, here, a gear train that transmits the rotational motion of the electric motor 23 to the screw 31 is built into the movable housing 21, but instead of building the gear train into the movable housing 21, it is also possible to provide it as a separate reducer outside the movable housing 21. In this case, the reducer can be a known reducer such as a pulley and belt, a parallel shaft gear reducer, a helical reducer, a bevel gear reducer, or a hypoid reducer.

[0023] [Injection section 30: Figure 1] 1, the injection unit 30 includes a screw 31, a cylindrical cylinder 33 that surrounds almost the entire area of ​​the screw 31 in the longitudinal direction L, and an injection nozzle 35 provided at the front end of the cylinder 33. The injection unit 30 also includes a support body 36 that supports the cylinder 33 at the rear B, and a raw material hopper 38 supported by the support body 36. 1, the support body 36 is provided with a passage 37 along the vertical direction H through which solid resin, which is a raw material for injection molding, passes, and a raw material hopper 38 connected to the passage 37. The passage 37 penetrates from the upper surface of the support body 36 to the cylinder gripping hole 36A, and is connected to an inlet 34 of the cylinder 33, which will be described later. Therefore, the raw material resin to be charged passes through the passage 37 and the inlet 34 and is supplied to the interior of the cylinder 33 around the screw 101.

[0024] The screw 31 includes a main body 31A having a spiral groove formed on its outer periphery, and a screw shaft 31B connected to the rear end of the main body 31A. The screw shaft 31B of the screw 31 is supported inside the movable housing 21 so that a rotational driving force from the electric motor 23 can be transmitted thereto. In the screw 31, the top surfaces of the flight crests that form the spiral grooves form the outer peripheral surface 31S of the screw 31.

[0025] The cylinder 33 is fixed to the support body 36 by being fitted into a cylinder gripping hole 36A of the support body 36. An inlet 34 is formed in the cylinder 33 for introducing raw material made of solid resin, which is the raw material for injection molding. The inlet 34 penetrates the inside and outside of the cylinder 33. The inlet 34 communicates with a passage 37 formed in the support body 36. The cylinder 33 also has a discharge port at its front end through which the resin melted by the screw 31 inside the cylinder 33 is discharged to the outside. The screw 31 housed inside the cylinder 33 can reciprocate in the front-rear direction and rotate inside the cylinder 33 . An electric wire heater (not shown), such as a band heater or cartridge heater, is provided around the cylinder 33, and the raw resin inside the cylinder 33 is heated by supplying electricity to the electric wire heater from a power source (not shown).

[0026] The injection nozzle 35 is fixed to the front end of the cylinder 33. Since the position of the cylinder 33 is fixed, the position of the injection nozzle 35 is also fixed. The injection nozzle 35 has an injection hole 35A provided at its front end and a resin passage 35B connected to the injection hole 35A. The molten resin plasticized and measured by the screw 31 passes through the resin passage 35B and the injection hole 35A and is injected into a mold cavity of a mold clamping device (not shown).

[0027] [Control unit 40: Figure 1] The control unit 40 controls the operation of the elements of the drive unit 20, such as the electric motor 23. In addition, the control unit 40 specifies a backpressure lower limit value corresponding to the candidate set screw rotation speed input by the operator, and specifies an upper limit screw rotation speed value corresponding to the candidate set screw backpressure input by the operator. The specification of the backpressure lower limit value and the upper limit screw rotation speed value will be described in detail later, but is performed by comparing pre-stored screw backpressure lower limit data with the candidate set rotation speed, and by comparing pre-stored screw rotation speed upper limit data with the candidate set backpressure.

[0028] The control unit 40 includes an input / output unit 41 that inputs and outputs signals, a calculation unit 43 that performs calculation processing, a memory unit 45 that stores data, and an input / display unit 47 that displays a setting screen, etc. The relationship between the input / output unit 41 to the input / display unit 47 and the determination of the back pressure lower limit value and the determination of the rotation speed upper limit value will be described below. The input / output unit 41 provides the calculation unit 43 with candidate set rotation speeds and candidate set back pressures input by the operator via the input / display unit 47. The input / output unit 41 also receives from the calculation unit 43 the results of a comparison between the back pressure lower limit value data and the candidate set rotation speeds, and a comparison between the upper rotation speed value data and the candidate set back pressures, and provides these results to the input / display unit 47. The calculation unit 43 receives candidate set rotation speeds and candidate set back pressures input by the operator from the input / output unit 41. The calculation unit 43 compares the back pressure lower limit data with the candidate set rotation speeds, and the upper rotation speed data with the candidate set back pressures, and provides the results to the input / output unit 41. These comparisons will be described in detail later.

[0029] The storage unit 45 stores back pressure lower limit data and rotation speed upper limit data. An example of the back pressure lower limit data and rotation speed upper limit data is shown in Fig. 2. Fig. 2 will be described in detail later. The input / display unit 47 displays a screen on which the operator inputs the set rotation speed and set back pressure. An example of this screen is shown in FIG. 6(a). The input / display unit 47 also displays the results of comparison between the back pressure lower limit value data received from the input / output unit 41 and the set rotation speed candidate, and the results of comparison between the rotation speed upper limit value data and the set back pressure candidate. An example of the comparison results is shown in FIG. 6(b). FIGS. 6(a) and 6(b) will be described in detail later.

[0030] [Data stored in the memory unit: Figure 2] FIG. 2 shows data stored in the storage unit 45 of the injection device of FIG. 1, where (a) shows back pressure lower limit data and (b) shows rotation speed upper limit data. In the back pressure lower limit data in FIG. 2(a), for example, the screw rotation speed range is divided into four ranges, and a back pressure lower limit value corresponds to each of the four ranges. For example, if the screw rotation speed is greater than 0 and is equal to or less than SR1, the back pressure lower limit value corresponds to the minimum value (BPmin) in the specifications of the injection device 1. The minimum value (BPmin) is, for example, 0 (zero) Pa. Also, if the screw rotation speed is greater than SR2 and is equal to or less than SR3, the back pressure lower limit value corresponds to BPb. In FIG. 2(a), BPmin <BPa<BPb<BPcである。

[0031] Here, if SR4 in Fig. 2(a) is the maximum screw rotation speed (100%) in the injection unit 1 and the maximum screw rotation speed is divided into four equal parts, Fig. 2(a) can be interpreted as follows: The same applies to the upper limit value data of the rotation speed shown in Fig. 2(b). If 0% < candidate set speed ≦ 25%, the back pressure lower limit corresponds to the minimum specification value. If 25% < candidate set speed ≦ 50%, back pressure BPa corresponds. If 50% < candidate set speed ≦ 75%, back pressure BPb corresponds. If 75% < candidate set speed ≦ 100%, back pressure BPc corresponds.

[0032] FIG. 2(a) and the above example of the four equal divisions show that the higher the set rotation speed of the screw 31, the higher the lower limit value of the back pressure that can be set. This is intended to prevent the back pressure that can be set from being set low when the screw rotation speed is high. The four equal divisions are merely an example, and it may be divided into fewer or more divisions than four. Also, the divisions are not limited to being equal like the four equal divisions, and can also be divided unevenly. This also applies to the rotational speed upper limit value data in FIG. 2(b).

[0033] The rotational speed upper limit value data in FIG. 2(b) divides the range of the back pressure received by the screw into four as an example, and the upper limit value of the rotational speed of the screw corresponds to each of the four ranges. For example, if the screw back pressure exceeds 0 and is at a pressure of BP1 or less, the rotational speed upper limit value corresponds to the rotational speed SRx. Also, if the screw back pressure exceeds BP2 and is at a pressure of BP3 or less, the rotational speed SRb corresponds. In FIG. 2(b), SRx < SRa < SRb < SRc. At this time, if the pressure BP4 is the maximum value of the back pressure in the injection device 1, the rotational speed SRc can be the maximum value of the screw rotational speed in the injection device 1.

[0034] The example of the four equal divisions in FIG. 2(b) shows that the lower the screw back pressure, the lower the upper limit value of the rotational speed that can be set. This is intended to prevent the rotational speed from being set high when the screw back pressure is low.

[0035] [Procedures until the start of the plasticization process: FIGS. 3, 4, 5, 6] Next, the procedures until the set rotational speed and the set back pressure are determined and the rotation of the screw starts and the plasticization process begins will be described with reference to FIGS. 3 to 6. This procedure is executed when the operator inputs the set rotational speed candidate and the set back pressure candidate to the input / output unit 47, and the arithmetic unit 43 reads out the back pressure lower limit value data and the rotational speed upper limit value data from the storage unit 45.

[0036] [Reception of the set rotational speed and the set back pressure: FIGS. 3, 6] A series of procedures is started when the calculation unit 43 receives the candidate set rotation speed SR0 and candidate set back pressure BP0 input by the operator to the input / display unit 47 (FIG. 3, S101). 6(a) shows an example of an input screen for the candidate set rotation speed SR0 and candidate set back pressure BP0. This input screen is displayed on the input / display unit 47. This input screen has a rotation speed input field 47A where the operator inputs the candidate set rotation speed SR0, and a back pressure input field 47B where the operator inputs the candidate set back pressure BP0, and the operator inputs the candidate set rotation speed SR0 and candidate set back pressure BP0 via a keyboard (not shown). This input screen is provided with a message field 47C that prompts the user to input the set rotation speed and set back pressure, and displays an evaluation of the input set rotation speed and set back pressure.

[0037] [Identifying the lower limit of back pressure and the upper limit of rotation speed: Figures 3, 4, and 5] When the calculation unit 43 receives the set rotation speed candidate SR0 and the set back pressure candidate PB0, it compares the magnitude of the set rotation speed candidate SR0 with the back pressure lower limit data stored in advance in the storage unit 45, and also compares the magnitude of the set back pressure candidate PB0 with the rotation speed upper limit data, thereby determining the back pressure lower limit BPLL and the rotation speed upper limit SRUL (FIG. 3, S103). A series of steps for comparing the magnitudes of the back pressure lower limit data and the set rotation speed candidate SR0 and a series of steps for comparing the magnitudes of the rotation speed upper limit data and the set back pressure candidate PB0 will be described in order with reference to FIGS. 4 and 5, respectively.

[0038] [Comparison of back pressure lower limit data and set rotation speed: Figure 4] When the set rotation speed candidate SR0 is input in step S101 of FIG. 3, the calculation unit 43 compares the back pressure lower limit value data shown in FIG. 2(a) read from the storage unit 45 with the set rotation speed candidate SR0 in the procedure shown in FIG. 4. The calculation unit 43 first determines whether the set rotation speed candidate SR0 satisfies 0 < SR0 ≤ SR1 (the first a range) (S121). If the set rotation speed candidate SR0 satisfies 0 < SR0 ≤ SR1 (S121 Yes), the minimum value BPmin of the back pressure is specified as the set back pressure BP based on the back pressure lower limit value data (S123). If the set rotation speed candidate SR0 does not satisfy 0 < SR0 ≤ SR1 (S121 No), it is determined whether the set rotation speed candidate SR0 satisfies SR1 < SR0 ≤ SR2 (the second a range) (S125). If the set rotation speed candidate SR0 satisfies SR1 < SR0 ≤ SR2 (S125 Yes), the back pressure BPa is specified as the set back pressure BP based on the back pressure lower limit value data (S127).

[0039] If the set rotation speed candidate SR0 does not satisfy SR1 < SR0 ≤ SR2 (S125 No), it is determined whether the set rotation speed candidate SR0 satisfies SR2 < SR0 ≤ SR3 (the third a range) (S129). If the set rotation speed candidate SR0 satisfies SR2 < SR0 ≤ SR3 (S129 Yes), the back pressure BPb is specified as the set back pressure BP based on the back pressure lower limit value data (S131). If the set rotation speed candidate SR0 does not satisfy SR2 < SR0 ≤ SR3 (S129 No), the back pressure BPc is specified as the set back pressure BP based on the back pressure lower limit value data (S133).

[0040] The back pressures BPmin, BPa, BPb, and BPc specified as the set back pressure BP as described above are collectively referred to as the back pressure lower limit value BPLL hereinafter. Also, in the procedure described above, as an example, the candidate set rotation speed SR0 was compared in the order of the first a range, the second a range, and the third a range. However, this order may be changed. For example, the candidate set rotation speed SR0 may be compared in the order of the third a range, the second a range, and the first a range. Also, in the comparison between the next rotation speed upper limit value data and the candidate set back pressure PB0, it is not limited to the order of the first b range, the second b range, and the third b range. Further, here, the comparison between the back pressure lower limit value data and the candidate set rotation speed was first described, and then the comparison between the rotation speed upper limit value data and the candidate set back pressure was described. However, this order is also arbitrary, and the comparison may be made in the reverse order or simultaneously.

[0041] [Comparison between Rotation Speed Upper Limit Value Data and Set Back Pressure: Figure 5] When the candidate set back pressure BP0 is input in step S101 of FIG. 3, the arithmetic unit 43 compares the rotation speed upper limit value data read from the storage unit 45 with the candidate set back pressure BP0 in the procedure shown in FIG. 5. First, the arithmetic unit 43 determines whether the candidate set back pressure BP0 satisfies 0 < BP0 ≤ BP1 (the first b range) (S141). If the candidate set back pressure BP0 satisfies 0 < BP0 ≤ BP1 (S141 Yes), the rotation speed SRx is specified as the candidate set rotation speed SR based on the rotation speed upper limit value data (S143). If the candidate set back pressure BP0 does not satisfy 0 < BP0 ≤ BP1 (S141 No), it is determined whether the candidate set back pressure BP0 satisfies BP1 < BP0 ≤ BP2 (the second b range) (S145). If the candidate set back pressure BP0 satisfies BP1 < BP0 ≤ BP2 (S145 Yes), the rotation speed SRa is specified as the set rotation speed SR based on the rotation speed upper limit value data (S147).

[0042] If the set backpressure candidate BP0 does not satisfy BP1 < BP0 ≤ BP2 (S145 No), it is determined whether the set backpressure candidate BP0 satisfies BP2 < BP0 ≤ BP3 (the third b range) (S149). If the set backpressure candidate BP0 satisfies BP2 < BP0 ≤ BP3 (S149 Yes), the rotational speed SRb is specified as the set rotational speed SR based on the rotational speed upper limit value data (S151). If the set backpressure candidate BP0 does not satisfy BP2 < BP0 ≤ BP3 (S149 No), the rotational speed SRc is specified as the set rotational speed SR based on the rotational speed upper limit value data (S153).

[0043] The rotational speeds SRx, SRa, SRb, and SRc specified as the set rotational speed SR as described above are collectively referred to as the rotational speed upper limit value SRUL hereinafter.

[0044] [Evaluation of the backpressure lower limit value BPLL and the rotational speed upper limit value SRUL: FIG. 3] When the backpressure lower limit value BPLL and the rotational speed upper limit value SRUL are specified, the evaluation of the set backpressure candidate BP0 or the set rotational speed candidate SR0 with respect to the backpressure lower limit value BPLL and the rotational speed upper limit value SRUL is performed as follows. That is, it is determined whether the set backpressure candidate BP0 exceeds the backpressure lower limit value BPLL (S105), and it is determined whether the set rotational speed candidate SR0 is smaller than the rotational speed upper limit value SRUL (S107).

[0045] If the set backpressure candidate BP0 does not exceed the backpressure lower limit value BPLL, that is, if the set backpressure candidate BP0 is less than or equal to the backpressure lower limit value BPLL (S105 No), a display prompting the operator not to accept the input of the set backpressure candidate BP0 and to re-enter the set backpressure candidate BP0 less than or equal to the backpressure lower limit value BPLL is made on the input / output display unit 47 (S106). Furthermore, if the set rotation speed candidate SR0 is not smaller than the rotation speed upper limit SRUL, i.e., if the set rotation speed candidate SR0 is equal to or greater than the rotation speed upper limit SRUL (No in S107), a message is displayed on the input / display unit 47 urging the operator to not accept the input of the set rotation speed candidate SR0 and to re-input a set rotation speed candidate SR0 that is equal to or less than the rotation speed upper limit SRUL (S108). An example of this display is shown in FIG. 6(b). That is, because the set rotation speed candidate SR0 input in the message field 47C of the input / display unit 47 is inappropriate, a message is displayed urging the operator to input a new set rotation speed candidate SR0. Here, the message is displayed visually in the message field 47C of the input / display unit 47, but this message can also be displayed audibly or by other means.

[0046] If the set back pressure candidate BP0 exceeds the back pressure lower limit BPLL (Yes in S105) and the set rotation speed candidate SR0 is smaller than the rotation speed upper limit SRUL (Yes in S107), the set back pressure candidate BP0 and the set rotation speed candidate SR0 are established as set values ​​(S109). Then, the control unit 40 executes the plasticizing process by controlling the screw 31 to rotate in accordance with the established set back pressure candidate BP0 and set rotation speed candidate SR0.

[0047] [effect] The injection device 1 described above is effective in preventing galling of the outer peripheral surface 31S of the screw 31, as will be described below. The screw 31 has a helical thread 31T at its outermost periphery, and the contact point between the screw 31 and the cylinder 33 is the outer peripheral surface 31S of the thread 31T. Therefore, when the screw 31 rotates, the outer peripheral surface 31S of the thread 31T and the inner peripheral surface 33S of the cylinder 33 slide on the helical surface. At this time, since molten resin enters between the outer peripheral surface 31S and the inner peripheral surface 33S during the plasticization process, sliding resistance (friction resistance) is generated on the helical surface, which is the sliding surface, due to the viscosity of the molten resin. As a result, the thread 31T of the screw 31 tries to move along the helix. In other words, the screw 31 moves back and forth in the same way that a male screw moves in the direction of the rotation axis relative to a female screw when it rotates.

[0048] In an in-line injection device, as shown in Figures 7(a) and (b), the molten resin MP is forced forward of the screw 31 during the plasticization process, and the screw 31 retreats due to a force PR that pushes the screw 31 toward the rear B. However, in addition to the force of the molten resin MP being forced forward F by the screw 31 pushing the screw 31 toward the rear B, a thrust force toward the rear B of the screw 31 is also generated. Specifically, the threads 31T of the screw 31 of an injection device are generally right-handed, and when the screw 31 rotates in the plasticization process (when the screw 31 rotates to send the resin toward the tip), it rotates left-handed (counterclockwise when viewed from the rear end of the screw 31), which is the same as when a normal screw is removed (loosened). Therefore, as shown in Figures 8(a) and 8(b), the friction force caused by the sliding between the outer peripheral surface 31S and the inner peripheral surface 33S of the screw 31 during the plasticization process becomes a thrust force ST toward the rear B of the screw 31. Hereinafter, this phenomenon will be referred to as the "screw phenomenon."

[0049] The frictional force caused by the sliding between the outer peripheral surface 31S of the thread 31T and the inner peripheral surface 33S of the cylinder 33 due to the screw rotation during the plasticization process is due to the viscosity of the molten resin MP. However, the viscosity of the molten resin MP, which is a non-Newtonian fluid, is proportional to the shear rate (sliding speed) due to the shear applied to the molten resin MP. Since the shear rate applied to the molten resin MP between the outer peripheral surface 31S and the inner peripheral surface 33S is the screw rotation speed (screw peripheral speed), the higher the screw rotation speed, the greater the viscosity of the molten resin MP at the thread 31T and the greater the sliding resistance. This means that the rotational force of the screw 31 is converted into axial thrust rather than being lost through deformation of the molten resin MP as the screw rotation speed increases. Therefore, the thrust force ST toward the rear B of the screw due to the screw phenomenon increases, and the screw 31 may retreat even if there is no molten resin MP in front F of the screw 31.

[0050] Even if there is no molten resin MP in front of the screw 31 F due to the screw phenomenon, when the screw 31 retreats, a gap G is generated in front of the screw 31 F, and the flow resistance of the screw 31 discharging the molten resin MP becomes extremely small. This means that there is no or only small back pressure against the molten resin MP being sent forward F around the screw 31. As a result, the speed at which the molten resin around the screw 31 is sent forward F increases, and the time for the molten resin MP to receive heat from the cylinder 33 becomes shorter.

[0051] The injection device 1 controls the screw 31 to suppress retraction by increasing the back pressure lower limit as the screw rotation speed increases, so that even at high screw rotation speeds, it is possible to prevent or suppress the generation of voids G in front of the screw 31 due to the screw phenomenon. This prevents the speed at which the molten resin voids MP around the screw 31 are sent forward F from becoming excessively high, shortening the time for the molten resin MP to receive heat from the cylinder 33. Therefore, the resin sent to the compression section of the screw 31 is sufficiently soft and deformable. This prevents hard resin lumps from creating a wedge effect inside the screw groove, preventing galling on the outer peripheral surface 31S of the screw 31.

[0052] The above describes the injection device 1 according to a preferred embodiment of the present invention. However, in addition to the above, it is possible to select and / or change the configurations described in the above embodiment or to change them to other configurations as appropriate, as long as they do not deviate from the gist of the present invention.

[0053] [Multi-stage switching] The injection device 1 can be provided with a function that allows the back pressure to be switched between multiple stages based on the position of the screw 31. In this injection device 1, a back pressure lower limit value is applied to the set back pressure at each stage. In other words, if the screw rotation speed is not switched between multiple stages during the plasticization process, the set back pressure lower limit value can be the same for all stages of switching based on the screw position. Furthermore, if the screw rotation speed is switched between different stages during the plasticization process, a back pressure lower limit value corresponding to each stage of switching the screw rotation speed can be applied. The present invention defines a lower limit for the set back pressure, and simply prevents the back pressure from being set below the lower limit. Therefore, the operator can set the same back pressure lower limit as long as it exceeds the lower limit, even in the case of a back pressure that can be switched in multiple stages, or can set different back pressure lower limit values.

[0054] [Change setting value] When an injection molding operation is in progress and the screw rotation speed and back pressure have already been set, an operator may input a change to the screw rotation speed or screw back pressure value. In this case, the control unit 40 determines whether the screw rotation speed range and back pressure lower limit value described above are both satisfied, and if not, a message is displayed as shown in Figure 6(b) and the injection unit 1 is not operated, i.e., an interlock is performed. Even if the operator inputs changes while the injection unit 1 is running, they are not reflected in the operation of the molding machine during operation, and are reflected as actual operating conditions in the next molding cycle. Therefore, the operator may input changes before the injection unit 1 is started or during operation.

[0055] [Determine the lower back pressure limit using any formula] The correspondence between the screw rotation speed and the back pressure lower limit value may be calculated by using pre-stored back pressure lower limit value data as described above, or by using any mathematical formula with the screw rotation speed as a variable. For example, if the screw rotation speed candidate SR0 (%) and the back pressure lower limit value BPX (%) are taken as the screw rotation speed candidate, and the back pressure lower limit value PBX is to be calculated linearly with respect to the screw rotation speed candidate SR0, the following first formula can be used. BPX(%)=SR0(%) × C1 … 1st formula C1: Arbitrary proportionality constant

[0056] Similarly, for example, if the screw back pressure lower limit candidate BP0 (%) and the set rotation speed SRX (%) are taken as the back pressure lower limit candidate BP0, and the set rotation speed SRX is to be calculated linearly with respect to the back pressure lower limit candidate BP0, the following second equation can be used. SRX(%)=BP0(%) × C2 … 2nd formula C2: Arbitrary proportionality constant

[0057] [Consideration of other conditions] When selecting the lower limit of the back pressure or the upper limit of the rotational speed, the setting state of the electric heater of each cylinder 33 and the molding cycle time can be further taken into consideration. For example, this occurs when the temperature setting of the electric wire heater on the base side of the cylinder 33 is high, or when the molding cycle time is long, particularly when the screw is stopped for a long time from the completion of plasticization to the start of plasticization in the next shot. In this way, when there is sufficient time for the resin to receive heat from the cylinder 33, the lower limit of the back pressure may be lowered or the upper limit of the screw rotation speed may be raised.

[0058] [Utilization of AI] Artificial intelligence (AI) may also be utilized for the control unit 40 described above. That is, the type of molding defect, the rate of occurrence, the degree of molding defect, and the like are linked to the molding conditions and converted into data. The AI ​​learns this data, and if the AI ​​determines that the candidate screw rotation speed settings or candidate back pressure settings input by the molding operator into the control unit 40 are likely to cause molding defects, it displays a message to that effect on the input / display unit 47. In addition, the AI ​​may display candidate screw rotation speed settings or candidate back pressure settings that it determines are least likely to cause molding defects, and may further limit the range of screw rotation speeds or back pressures that can be set and input.

[0059] [Application to extrusion molding machines] Also known is an injection device in which a screw 101 is rotatably disposed inside a cylindrical plunger 103 inserted into a plunger barrel 105 as shown in Figure 9, and molten resin material is supplied and metered into the plunger barrel 105 by rotation of the screw 101, and the plunger 103 and the screw 101 are advanced relative to the plunger barrel 105 to inject the molten resin material inside the plunger barrel 105. In this case, a reducer 107 for rotating the screw 101 is known to be driven by an electric motor or a hydraulic motor via a known reducer such as a pulley and belt, a parallel shaft gear reducer, a helical reducer, a bevel gear reducer, or a hypoid reducer.

[0060] In the injection unit shown in FIG. 9, the screw 101 is fixed in the screw axial direction relative to the plunger barrel 105, similar to the structure of an extruder. Therefore, no gap is generated ahead of the screw 101 due to the screw effect of the screw 101. However, the screw in an actual extruder generally rotates faster than the screw in the injection unit of an injection molding machine. When the screw in the injection unit of an extruder rotates at high speed, the transport speed of the resin in the cylinder increases, similar to when the screw phenomenon occurs. Therefore, the back pressure lower limit limit of the present invention is also effective in the injection unit of an extruder. [Explanation of symbols]

[0061] 1 Injection device 10 Support part 11 beds 13 Guide rail 20 Drive unit 21 Mobile Housing 23 Electric motor 30 Injection part 31 screw 31A main body 31B screw shaft 31S outer surface 31T thread 33 cylinders 33S Inner surface 34 Inlet 35 Injection nozzle 35A injection hole 35B Resin passage 36 Support 36A Cylinder gripping hole 37 Passage 38 Raw material hopper 38 40 Control Unit 41 Input / output section 43 Arithmetic section 45 Storage section 47 Input and display section 47A RPM input field 47B Back pressure input field 47C Message field

Claims

1. an injection unit having a cylindrical cylinder and a screw rotatably disposed in the cylinder; a rotation mechanism that rotates the screw; a control unit that controls the operation of the rotation mechanism, The control unit The screw rotation speed and the screw back pressure are made to correspond to each other, and the setting range of one or both of the screw rotation speed and the screw back pressure in the plasticization process is set as follows: The higher the set rotation speed of the screw, the higher the settable back pressure lower limit value is limited; An injection apparatus characterized in that the lower the set back pressure of the screw, the lower the set upper limit value of the rotation speed.

2. The control unit The set range is: Specify one or both of a back pressure lower limit value, which is the lower limit of the back pressure received by the screw, and a rotation speed upper limit value, which is the upper limit of the rotation speed of the screw. The injection device according to claim 1 .

3. The control unit The input candidate set rotation speed of the screw is compared with one or more screw rotation speed ranges stored in advance in the control unit, When the stored screw rotation speed range includes the set rotation speed candidate to be input, The back pressure lower limit value corresponding to the screw rotation speed range is identified as the back pressure lower limit value of the set range, and input of a set back pressure candidate smaller than the lower limit value is not accepted. The injection device according to claim 2 .

4. The control unit The input screw back pressure candidate is compared with one or more screw back pressure value ranges previously stored in the control unit, When the stored screw back pressure value range includes the set back pressure candidate to be input, The rotation speed upper limit value corresponding to the screw back pressure value range is specified as the rotation speed upper limit value of the setting range, and input of a set rotation speed candidate greater than the upper limit value is not accepted. The injection device according to claim 2 or 3.

5. The control unit Identifying one or both of the back pressure lower limit value and the rotation speed upper limit value by one or both of a first formula indicating the correlation between the input candidate set rotation speed of the screw and the back pressure lower limit value, and a second formula indicating the correlation between the input candidate set back pressure of the screw and the rotation speed upper limit value, The input of one or both of the candidate set back pressure that is smaller than the lower limit back pressure value and the candidate set rotation speed that is larger than the upper limit rotation speed value is not accepted. The injection device according to claim 2 .

6. The control unit The set back pressure candidate is smaller than the back pressure lower limit value and the set back pressure candidate is larger than the rotation speed upper limit value. Not accepting input of one or both of the rotation speed settings. Prompting the user to input a new candidate set back pressure in place of the candidate set back pressure; and Indicating that the user is prompted to input a new candidate set rotation speed in place of the candidate set rotation speed; The injection device according to any one of claims 3 to 5.

7. The screw rotation speed and screw back pressure in the plasticization process, which are the plasticization conditions of the injection device, are made to correspond to each other, and the setting range of the screw rotation speed or back pressure is determined. The higher the set rotation speed of the screw, the higher the settable back pressure lower limit value is limited; The lower the set back pressure of the screw, the lower the set upper limit of the rotation speed. An injection method characterized by:

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