JP2023106052A - Injection apparatus, and injection method - Google Patents

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

The present invention relates to motion control of a plasticizing screw.

A typical injection apparatus feeds a pellet-shaped raw material resin from the rear side of a cylinder, heats the raw material resin in the cylinder, and melts the raw material resin by applying a shearing force by rotating a screw. Molten resin is weighed inside the cylinder and injected from an injection nozzle provided at the front end of the cylinder into a cavity formed inside the mold.

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

In Patent Document 1, the larger the dimension of the molded product or the shorter the molding cycle time, the faster the raw material resin moves in the cylinder and the shorter the time it receives heat from the cylinder. A larger amount of heat is given to the resin from the side, that is, the side from which the raw material resin is introduced. For this reason, Patent Literature 1 discloses an example in which the temperature of the heater on the base side of the cylinder is automatically set high to prevent variations in the metering time and galling of the outer periphery of the screw. there is

WO2007/105646

The number of rotations of the screw and the back pressure that the screw receives from the molten resin during the plasticizing process are set by the operator of the injection device. However, the operator may set the screw rotation speed too high or set the screw back pressure to a low pressure near the minimum pressure. As a result, the moving speed of the resin inside the cylinder is further increased, and the time during which the resin receives heat from the cylinder is shortened. In this case, the resin cannot be sufficiently heated by the cylinder, and the mass of raw material resin, which has not been melted yet and is still hard, is pushed into the region where the groove depth is shallow, which is the compressed portion of the screw. As a result, the hard resin block acts as a wedge inside the screw groove, and the screw is strongly pressed against the inner peripheral surface of the cylinder on the opposite side where the wedge has entered. If the screw continues to rotate in this state, galling may occur on the outer peripheral surface of the screw.

Therefore, the present invention provides an injection apparatus that can prevent galling on the outer peripheral surface of the screw by avoiding setting the screw rotation speed too high or setting the screw back pressure too low. intended to

An injection device of the present invention comprises an injection unit having a cylindrical cylinder, a screw rotatably arranged in the cylinder, a rotation mechanism for rotating the screw, a control unit for controlling the operation of the rotation mechanism, Prepare.
The control unit of the present invention makes the screw rotation speed and the screw back pressure correspond to each other, and limits the setting range of one or both of the screw rotation speed and the screw back pressure in the plasticizing process.

Preferably, the control unit of the present invention specifies one or both of a back pressure lower limit, which is the lower limit of the back pressure applied to the screw, and a rotation speed upper limit, which is the upper limit of the rotation speed of the screw, as the setting range.

Preferably, the control unit of the present invention compares the input screw rotation speed setting candidate with one or more screw rotation speed ranges pre-stored in the control unit, and inputs the screw rotation speed range to the stored screw rotation speed range. If the setting rotation speed candidate is included, the back pressure lower limit value associated with the screw rotation speed range is specified as the back pressure lower limit value of the setting range, and the setting back pressure candidate smaller than the lower limit value is not accepted.

Preferably, the control unit of the present invention compares the input screw back pressure setting candidate with one or more screw back pressure value ranges pre-stored in the control unit, and compares the stored screw back pressure value ranges. , the upper limit of rotation speed associated with the range of screw back pressure values is specified as the upper limit of rotation speed of the setting range, and candidates for setting rotation speed greater than the upper limit are specified. I do not accept.

Preferably, the control unit of the present invention includes a first formula showing the correlation between the input candidate set back pressure of the screw and the lower limit value of the back pressure, and the input candidate set back pressure of the screw and the upper limit value of the rotation speed. The back pressure lower limit value and the rotation speed upper limit value are specified by one or both of the second equation showing the correlation of, and one of the set back pressure candidate smaller than the back pressure lower limit value and the set rotation speed candidate larger than the rotation speed upper limit value or Both inputs are not accepted.

Preferably, the control unit of the present invention does not accept input of one or both of a set back pressure candidate smaller than the back pressure lower limit value and a set rotation candidate larger than the rotational speed upper limit value. Prompting the input of a new set back pressure candidate, and prompting the input of a new set rotation speed candidate instead of the set rotation speed candidate are expressed.

The present invention provides an injection method in which the screw rotation speed and the screw back pressure in the plasticizing process, which are the plasticizing conditions of the injection apparatus, are made to correspond to each other to limit the setting range of the screw rotation speed or the back pressure.

In the injection device of the present invention, 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 plasticizing process is limited. As a result, according to the injection apparatus of the present invention, by avoiding setting the screw rotation speed too high or setting the screw back pressure too low, galling can be prevented from occurring on the outer peripheral surface of the screw. can be prevented.

It is a side view showing a schematic structure of an injection device concerning an embodiment of the present invention. FIG. 1 shows the data stored in the storage unit of the injection device of FIG. The range of the back pressure during the curing process and the upper limit of the screw rotation speed corresponding to the range are shown. 1. It is a flowchart which shows an example of the procedure until the set rotation speed and set back pressure in the injection apparatus of FIG. 1 are decided, rotation of a screw is started, and a plasticizing process is started. FIG. 4 is a flow diagram showing an example of a procedure for determining a set rotational speed candidate (SR0) in the flow diagram of FIG. 3; FIG. 4 is a flow chart showing an example of a procedure for determining a setting back pressure candidate (BP0) in the flow chart of FIG. 3; Shown are examples of display on the display unit of the control unit in FIG. It is an example of the display screen when the setting rotation speed candidate (SR0) is inappropriate. FIG. 5 is a view for explaining how the screw is pushed toward the rear end by molten resin in the plasticizing process of the in-line injection device. FIG. 7 is a diagram illustrating another force that pushes the screw toward the rear end by the molten resin in the plasticizing process of the in-line injection device. It is a side view showing a schematic structure of an injection device referred to about this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The injection device 1 constitutes an injection molding machine by being combined with a mold clamping device (not shown). In order to obtain a molded product using the injection device 1, the following steps are performed in order. The injection apparatus 1 according to the present embodiment limits one or both of the setting range of the screw rotation speed and the setting range of the screw back pressure in the following plasticizing process.
Mold clamping process: The movable mold and fixed mold that constitute the mold clamping process are closed and clamped at high pressure.
Plasticization process: The resin pellets are heated and melted inside the cylinder to be plasticized.
Injection process: The plasticized molten resin is injected and filled into the cavity formed by the movable mold and the fixed mold.
Holding pressure step: Continue applying pressure to the molten resin until the molten resin filled in the cavity is cooled and solidified.
Mold opening process: Open the mold.
Taking out process: Take out the molded product that has been cooled and solidified in the cavity.

[Overall Configuration of Injection Device 1: Fig. 1]
As shown in FIG. 1, the injection device 1 includes a support portion 10, a drive portion 20 supported by the support portion 10 and responsible for moving the screw 31 in the front-rear direction and rotating the screw 31, and the screw 31. and an injection part 30 involved in the injection of the The injection device 1 also includes a control section 40 that controls the operation of the injection device 1 . In the plasticizing process, the injection device 1 can prevent galling of the outer peripheral surface 31S of the screw 31 by limiting the setting range of one or both of the screw rotation speed and the screw back pressure by the control unit 40. .

In the injection device 1, the side marked with F in FIG. 1 is defined as the front side, and the side marked with B is defined as the rear side. This definition of front F and rear B is intended to have a relative meaning.
Further, the width direction W, the longitudinal direction L and the vertical direction H of the injection device 1 are defined as shown in FIG.

[Support portion 10: FIG. 1]
As shown in FIG. 1, the support portion 10 includes a bed 11 extending from the front F toward the rear B, and a pair of guide rails 13 provided on the bed 11 and on the rear B side of the bed 11. Prepare.
A pair of guide rails 13 are fixed on the bed 11 with a gap in the width direction W therebetween. A moving housing 21 of a drive unit 20, which will be described later, is slidably placed on the guide rail 13 from the front F to the rear B and from the rear B to the front F. As shown in FIG. Note that, in the present embodiment, the means is not limited to the guide rails 13 as long as the reciprocating movement of the moving housing 21 in the front-rear direction can be achieved. As an example, a guide groove or a guide wall can be provided at the position where the guide rail 13 is provided, and the moving housing 21 can be provided with rollers or sliding plates that travel along this guide.

[Driver 20: FIG. 1]
Next, the driving section 20 will be described.
As shown in FIG. 1 , the drive unit 20 includes a movable housing 21 supported to be movable in the front-rear direction along the guide rails 13 and an electric motor 23 supported at the rear B of the movable housing 21 .

The movable housing 21 is movable from the front F toward the rear B and from the rear B toward the front F along the guide rail 13 by, for example, a piston-cylinder mechanism (not shown).
The moving housing 21 accommodates therein a transmission mechanism such as a gear train and bearings for transmitting 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 moving housing 21 to detect the load applied to the screw 31 in the axial direction. The back pressure of the screw 31 in the plasticizing process is controlled based on the load detected by the load cell.
The electric motor 23 is rotated by an instruction from the controller 40 . Although the electric motor 23 is used here, it is also possible to use other rotary drive sources capable of outputting a rotary drive force, such as hydraulic motors. Further, here, the gear train for transmitting the rotary motion of the electric motor 23 to the screw 31 is built in the moving housing 21, but the gear train is not built in the moving housing 21, but an individual reduction gear is provided outside the moving housing 21. It can also be prepared as In this case, the speed reducer can be a known speed reducer such as a pulley and belt, a parallel shaft gear speed reducer, a helical speed reducer, a bevel gear speed reducer, or a hypoid speed reducer.

[Injection part 30: FIG. 1]
As shown in FIG. 1 , the injection section 30 includes a screw 31 , a cylindrical cylinder 33 surrounding substantially the entire length 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 section 30 also includes a support 36 that supports the cylinder 33 at the rear B, and a raw material hopper 38 that is supported by the support 36 .
As shown in FIG. 1, the support 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 36 to the cylinder gripping hole 36A, and communicates with the inlet 34 of the cylinder 33, which will be described later. Therefore, the raw material resin to be charged is supplied to the inside of the cylinder 33 and around the screw 101 through the passage 37 and the inlet 34 .

The screw 31 includes a main body 31A having a helical groove formed on its outer circumference, and a screw shaft 31B connected to the rear end of the main body 31A. A screw shaft 31B of the screw 31 is supported inside the moving housing 21 so that the rotational driving force from the electric motor 23 can be transmitted.
In the screw 31 , the top surface of the flight crest forming the spiral groove constitutes the outer peripheral surface 31</b>S of the screw 31 .

The cylinder 33 is fixed to the support 36 by being fitted into the cylinder gripping hole 36A of the support 36 .
The cylinder 33 is formed with an inlet 34 into which a raw material made of solid resin, which is a raw material for injection molding, is introduced. The inlet 34 extends through the inside and outside of the cylinder 33 . Input port 34 communicates with passage 37 formed in support 36 .
Further, the cylinder 33 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 .
A heating wire heater such as a band heater and a cartridge heater (not shown) is provided around the cylinder 33. By supplying power to the heating wire heater from a power source (not shown), the raw material resin inside the cylinder 33 is heated. to heat.

An 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 includes an injection hole 35A provided at its front end, and a resin passage 35B communicating with the injection hole 35A. The molten resin plasticized and weighed by the screw 31 is injected into a mold cavity of a mold clamping device (not shown) through a resin passage 35B and an injection hole 35A.

[Control unit 40: FIG. 1]
The control unit 40 controls the operation of elements of the drive unit 20 such as the electric motor 23 .
In addition to this, the control unit 40 specifies the lower limit value of the back pressure corresponding to the set rotation speed candidate of the screw input by the operator, and rotates the screw according to the set back pressure candidate of the screw input by the operator. Identify numerical limits. Details of the back pressure lower limit value and the rotation speed upper limit value will be specified later. This is done by comparing the rotational speed upper limit data and the set back pressure candidate.

The control unit 40 includes an input/output unit 41 for inputting and outputting signals, an arithmetic unit 43 for arithmetic processing, a storage unit 45 for storing data, and an input/display unit 47 for displaying setting screens and the like. ing. Regarding the input/output unit 41 to the input/display unit 47, the relationship with specifying the back pressure lower limit value and the relationship with specifying the rotational speed upper limit value will be described below.
The input/output unit 41 provides the calculation unit 43 with setting rotation speed candidates and setting back pressure candidates input by the operator via the input/display unit 47 . In addition, the input/output unit 41 receives from the calculation unit 43 the results of comparison between the back pressure lower limit value data and the setting rotation speed candidate and the rotation speed upper limit value data and the setting back pressure candidate from the calculation unit 43. It is received and provided to the input/display unit 47 .
The calculation unit 43 receives from the input/output unit 41 the set rotational speed candidate and the set back pressure candidate input by the operator. The calculation unit 43 compares the back pressure lower limit value data and the set rotation speed candidate, and the rotation speed upper limit data and the set back pressure candidate, and provides the input/output unit 41 with the results. These comparisons will be described later in detail.

The storage unit 45 stores back pressure lower limit value data and rotational speed upper limit value data. An example of back pressure lower limit data and rotation speed upper limit data is shown in FIG. Details of FIG. 2 will be described later.
The input/display unit 47 displays a screen for the operator to input the set rotational speed and the set back pressure. An example of this screen is shown in FIG. 6(a). The input/display unit 47 also displays the result 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 comparison result between the rotation speed upper limit data and the set back pressure candidate. An example of the comparison result is shown in FIG. 6(b). Details of FIGS. 6A and 6B will be described later.

[Data stored in storage unit: Fig. 2]
FIG. 2 shows data stored in the storage unit 45 of the injection apparatus of FIG. 1, where (a) shows back pressure lower limit data and (b) shows rotation speed upper limit data.
The back pressure lower limit value data of FIG. 2(a) divides the screw rotation speed range into four ranges as an example, and the back pressure lower limit value corresponds to each of the four ranges. For example, if the screw rotation speed exceeds 0 and is equal to or lower than SR1, the lower limit of the back pressure corresponds to the minimum value (BPmin) in the specifications of the injection device 1 . The minimum value (BPmin) is 0 (zero) Pa, for example. Further, when the screw rotation speed exceeds SR2 and is equal to or lower than SR3, BPb corresponds to the back pressure lower limit. In FIG. 2A, BPmin<BPa<BPb<BPc.

Here, SR4 in FIG. 2(a) is the maximum value (100%) of the screw rotation speed in the injection device 1, and if the maximum value of the screw rotation speed is divided into four equal parts, FIG. can catch. The same applies to the rotational speed upper limit data shown in FIG. 2(b).
When 0% < Candidate set rotation speed ≤ 25%, the back pressure lower limit value corresponds to the specification lowest value.
When 25%<set rotation speed candidate≦50%, the back pressure BPa corresponds.
If 50%<set rotation speed candidate≦75%, the back pressure BPb corresponds.
When 75%<set rotation speed candidate ≤100%, the back pressure BPc corresponds.

FIG. 2(a) and the example of 4 equal divisions above show that the lower limit of the back pressure that can be set increases as the set number of rotations of the screw 31 increases. This is intended to make it impossible to set a lower back pressure as the number of screw revolutions increases. The division into four equal parts is only an example, and divisions into less than four equal parts or more than four equal parts may be used. Also, divisions are not limited to equal divisions such as four equal divisions, but may be divided into unequal divisions. can. This also applies to the rotational speed upper limit data in FIG. 2(b).

The rotation speed upper limit data in FIG. 2(b) divides the range of the back pressure that the screw receives into four ranges, for example, and the screw rotation speed upper limit corresponds to each of the four ranges. For example, if the screw back pressure exceeds 0 and is equal to or lower than BP1, the rotational speed upper limit corresponds to the rotational speed SRx. Further, if the screw back pressure exceeds BP2 and is equal to or lower than BP3, the rotational speed SRb corresponds. In FIG. 2B, 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. FIG.

The example of 4 equal divisions in FIG. 2(b) shows that the lower the screw back pressure, the lower the upper limit of the rotational speed that can be set. This is intended to make it impossible to set the rotational speed higher as the screw back pressure is lower.

[Procedure until the plasticization process starts: Figures 3, 4, 5, and 6]
Next, the procedure until the set rotational speed and set back pressure are determined, the rotation of the screw is started, and the plasticizing process is started will be described with reference to FIGS. 3 to 6. FIG. In this procedure, in response to the operator inputting a setting rotation speed candidate and a setting back pressure candidate to the input/display unit 47, the calculation unit 43 retrieves back pressure lower limit value data and rotation speed upper limit data from the storage unit 45. read and executed.

[Receipt of set rotation speed and set back pressure: Figures 3 and 6]
A series of procedures is started when the calculation unit 43 accepts the setting rotation speed candidate SR0 and the setting back pressure candidate BP0 input by the operator to the input/display unit 47 (S101 in FIG. 3).
An example of an input screen for setting rotation speed candidate SR0 and setting back pressure candidate BP0 is shown in FIG. 6(a). This input screen is displayed on the input/display section 47 . This input screen includes a rotation speed input field 47A in which the operator inputs a setting rotation speed candidate SR0, and a back pressure input field 47B in which the operator inputs a setting back pressure candidate BP0. The operator inputs a setting rotational speed candidate SR0 and a setting back pressure candidate BP0 via a keyboard.
This input screen is provided with a message field 47C for prompting the input of the set rotation speed and the set back pressure and for displaying that the input set rotation speed and set back pressure are to be evaluated.

[Specification of back pressure lower limit and rotation speed upper limit: Figs. 3, 4, and 5]
When receiving the setting rotation speed candidate SR0 and the setting back pressure candidate PB0, the calculation unit 43 compares the back pressure lower limit value data stored in advance in the storage unit 45 with the setting rotation speed candidate SR0. By comparing the upper limit value data and the set back pressure candidate PB0, the back pressure lower limit value BPLL and the rotational speed upper limit value SRUL are specified (S103 in FIG. 3).
A series of procedures for comparing the back pressure lower limit value data and the set rotation speed candidate SR0 and a sequence of procedures for comparing the rotation speed upper limit data and the set back pressure candidate PB0 are shown in FIGS. 4 and 5, respectively. will be explained in order.

[Comparison of back pressure lower limit data and set rotation speed: Fig. 4]
3. When the rotational speed setting candidate SR0 is input in step S101 of FIG. 4 are compared according to the procedure shown in FIG.
The calculation unit 43 first determines whether or not the set rotational speed candidate SR0 satisfies 0<SR0≦SR1 (range 1a) (S121). If the setting rotation speed candidate SR0 satisfies 0<SR0≦SR1 (S121 Yes), the minimum back pressure value BPmin is specified as the setting back pressure BP based on the back pressure lower limit value data (S123).
If the rotation speed candidate SR0 does not satisfy 0<SR0≤SR1 (S121 No), it is determined whether the rotation speed candidate SR0 satisfies SR1<SR0≤SR2 (range 2a) (S125). If the setting rotational speed candidate SR0 satisfies SR1<SR0≦SR2 (S125 Yes), the back pressure BPa is specified as the setting back pressure BP based on the back pressure lower limit value data (S127).

If the rotation speed candidate SR0 does not satisfy SR1<SR0≤SR2 (S125 No), it is determined whether the rotation speed candidate SR0 satisfies SR2<SR0≤SR3 (3a range) (S129). If the setting rotation speed candidate SR0 satisfies SR2<SR0≦SR3 (S129 Yes), the back pressure BPb is identified as the setting back pressure BP based on the back pressure lower limit value data (S131). If the setting rotation speed candidate SR0 does not satisfy SR2<SR0≦SR3 (S129 No), the back pressure BPc is specified as the setting back pressure BP based on the back pressure lower limit value data (S133).

The back pressure BPmin, the back pressure BPa, the back pressure BPb, and the back pressure BPc specified as the set back pressure BP as described above are hereinafter collectively referred to as the back pressure lower limit value BPLL.
Further, in the procedure described above, as an example, the 1a range, the 2a range, and the 3a range are compared in the order of the set rotation speed candidate SR0, but this order may be changed. The 2a-th range and the 1a-th range may be compared with the set rotation speed candidate SR0 in that order. The comparison between the rotation speed upper limit data and the setting back pressure candidate PB0 is not limited to the order of the 1b range, the 2b range and the 3b range. Here, the comparison between the back pressure lower limit value data and the set rotation speed candidate will be explained first, and then the rotation speed upper limit data and the set back pressure candidate will be explained. The comparison may be performed in reverse order, or may be performed simultaneously.

[Comparison of upper limit data of rotation speed and set back pressure: Fig. 5]
When the set back pressure candidate BP0 is input in step S101 of FIG. 3, the calculation unit 43 compares the rotational speed upper limit data read from the storage unit 45 with the set back pressure candidate BP0 in the procedure shown in FIG. .
The calculation unit 43 first determines whether or not the set back pressure candidate BP0 satisfies 0<BP0≤BP1 (1b range) (S141). If the setting back pressure candidate BP0 satisfies 0<BP0≦BP1 (S141 Yes), the rotation speed SRx is identified as the setting rotation speed candidate SR based on the rotation speed upper limit data (S143).
If the set back pressure candidate BP0 does not satisfy 0<BP0≤BP1 (S141 No), it is determined whether or not the set back pressure candidate BP0 satisfies BP1<BP0≤BP2 (second b range) (S145). If the set back pressure candidate BP0 satisfies BP1<BP0≦BP2 (S145 Yes), the rotational speed SRa is identified as the set rotational speed SR based on the rotational speed upper limit data (S147).

If the set back pressure candidate BP0 does not satisfy BP1<BP0≦BP2 (S145 No), it is determined whether or not the set back pressure candidate BP0 satisfies BP2<BP0≦BP3 (3b range) (S149). If the set back pressure 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 back pressure 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).

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

[Evaluation of back pressure lower limit BPLL and rotational speed upper limit SRUL: Fig. 3]
When the back pressure lower limit BPLL and the rotation speed upper limit SRUL are specified, the set back pressure candidate BP0 or the set rotation speed candidate SR0 for the back pressure lower limit BPLL and the rotation speed upper limit SRUL are evaluated as follows. .
That is, it is determined whether or not the set back pressure candidate BP0 exceeds the back pressure lower limit BPLL (S105), and it is determined whether or not the set rotation speed candidate SR0 is smaller than the rotation speed upper limit SRUL ( S107).

If the set back pressure candidate BP0 does not exceed the back pressure lower limit value BPLL, that is, if the set back pressure candidate BP0 is equal to or less than the back pressure lower limit value BPLL (S105 No), the input of the set back pressure candidate BP0 is not accepted and the back pressure A display prompting the operator to re-enter the set back pressure candidate BP0 below the pressure lower limit BPLL is displayed on the input/display unit 47 (S106).
Further, if the setting rotation speed candidate SR0 is not smaller than the rotation speed upper limit value SRUL, that is, if the setting rotation speed candidate SR0 is equal to or greater than the rotation speed upper limit value SRUL (S107 No), the input of the setting rotation speed candidate SR0 is not accepted. A display prompting the operator to re-input a set rotation speed candidate SR0 that is equal to or lower than the rotation speed upper limit value SRUL is displayed on the input/display unit 47 (S108). An example of this display is shown in FIG. 6(b). That is, since the rotation speed candidate SR0 entered in the message field 47C of the input/display unit 47 is inappropriate, a message prompting the user to enter a new rotation speed candidate SR0 is displayed. Here, the message is visually expressed in the message field 47C of the input/display unit 47, but the message can also be expressed by voice or other means.

If the set back pressure candidate BP0 exceeds the back pressure lower limit BPLL (S105 Yes) and the set rotation speed candidate SR0 is smaller than the rotation speed upper limit SRUL (S107 Yes), the set back pressure candidate BP0 and the set rotation The number candidate SR0 is determined as a set value (S109). Then, the control unit 40 performs the plasticizing process by controlling the rotation of the screw 31 in accordance with the set back pressure candidate BP0 and the set rotation speed candidate SR0.

[effect]
The injection device 1 described above is effective in preventing galling of the outer peripheral surface 31S of the screw 31 as described below.
The outermost circumference of the screw 31 is a spiral thread 31T, and the contact portion between the screw 31 and the cylinder 33 is the outer peripheral surface 31S of the screw thread 31T. The inner peripheral surface 33S of 33 slides on the spiral surface. At this time, since the molten resin enters between the outer peripheral surface 31S and the inner peripheral surface 33S in the plasticizing process, sliding resistance (frictional resistance) is generated due to the viscosity of the molten resin on the spiral surface that is the sliding surface. . Then, the thread 31T of the screw 31 tries to move along the spiral, that is, the screw 31 moves forward and backward in the same way as the male screw moves in the direction of the rotation axis relative to the female screw when it rotates.

As shown in FIGS. 7(a) and 7(b), in the in-line injection apparatus, the molten resin MP pushed forward of the screw 31 in the plasticizing process pushes the screw 31 backward B with a force PR causes the screw 31 to retreat.
However, in addition to the force of the molten resin MP pushed forward F from the screw 31 pushing the screw 31 toward the rear B, a thrust toward the rear B of the screw 31 is generated. Specifically, the thread 31T of the screw 31 of the injection device is generally a right-hand thread, and when the screw 31 rotates in the plasticizing process (when the screw 31 rotates to send the resin toward the tip), it rotates counterclockwise (the screw 31 counterclockwise when viewed from the rear end side), the state is the same as when a normal screw is removed (loosen). Therefore, as shown in FIGS. 8(a) and 8(b), the frictional force generated by the sliding between the outer peripheral surface 31S and the inner peripheral surface 33S of the screw 31 in the plasticizing process produces a thrust force ST to the rearward B of the screw 31. become. Hereinafter, this phenomenon will be referred to as "screw phenomenon".

The frictional force caused by the sliding between the outer peripheral surface 31S of the screw thread 31T and the inner peripheral surface 33S of the cylinder 33 due to the rotation of the screw 31 in the plasticizing process is caused by the viscosity of the molten resin MP. The viscosity of a certain molten resin MP is proportional to the shear rate (sliding rate) due to the shear applied to the molten resin MP. At this time, 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 outer peripheral speed). increases and the sliding resistance increases. This means that the rotational force of the screw 31 does not escape due to the deformation of the molten resin MP as the screw rotational speed increases, and is converted into thrust in the axial direction. For this reason, the thrust ST to 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 the front F of the screw 31 .

When the screw 31 retreats even if there is no molten resin MP in front F of the screw 31 due to the screw phenomenon, a gap G is generated in front F of the screw 31, so that the screw 31 discharges the molten resin MP. Resistance becomes extremely small. This means that there is no or little back pressure against sending the molten resin MP forward F around the screw 31 . For this reason, the speed at which the molten resin around the screw 31 is sent forward F increases, and the time during which the molten resin MP receives heat from the cylinder 33 is shortened.

The injection device 1 increases the lower limit of the back pressure as the screw rotation speed increases to suppress the retraction of the screw 31. Therefore, even when the screw rotation speed is high, a gap G is formed in front of the screw 31 due to the screw phenomenon. can prevent or suppress the occurrence of As a result, it is possible to prevent a phenomenon in which the speed at which the molten resin gap MP around the screw 31 is sent forward F becomes excessively high, and the time during which the molten resin MP receives heat from the cylinder 33 is shortened. The resin fed into the compression portion of the screw 31 is in a sufficiently soft and deformable state. As a result, the lump of hard resin does not produce a wedging effect inside the screw groove, so galling of the outer peripheral surface 31S of the screw 31 can be prevented.

The injection device 1 according to the preferred embodiment of the present invention has been described above. It is possible to

[Multi-stage switching]
The injection device 1 can be provided with a function capable of switching the back pressure in a plurality of stages based on the position of the screw 31 . In this injection device 1, the back pressure lower limit value is applied to the set back pressure at each stage. That is, if the screw rotation speed is not switched in a plurality of stages in the plasticizing process, the lower limit value of the set back pressure can be set to the same value in the switching of the plurality of stages based on the screw position. Further, when the screw rotation speed is switched to a plurality of different steps in the plasticizing process, the back pressure lower limit corresponding to each switching step of the screw rotation speed can be applied.
In addition, the present invention defines the lower limit of the set back pressure, and simply prevents the setting of the back pressure below the lower limit. It is also possible to set the same back pressure lower limit value even in the case of back pressures that are different from each other, and it is also possible to set different back pressure lower limit values.

[Change set value]
When an injection molding operation is performed and the screw rotation speed and the back pressure are already set, the operator may input to change the screw rotation speed or the screw back pressure value. In this case, the control unit 40 determines whether both the screw rotation speed range and the back pressure lower limit are satisfied, and if they are not satisfied, a message is displayed as shown in FIG. 6(b). At the same time, the operation of the injection device 1 can be disabled, that is, an interlock can be provided.
Even if the input of the change by the operator is set while the injection device 1 is in operation, it is not reflected in the operation of the molding machine during operation, and is reflected as the actual operating conditions only after the next molding cycle. is. Therefore, the input of the change by the operator may be before the injection apparatus 1 is operated or during the operation.

[Specification of back pressure lower limit value by arbitrary formula]
Regarding the correspondence between the screw rotation speed and the back pressure lower limit value, in addition to using the back pressure lower limit value data stored in advance as described above, the back pressure lower limit value can be calculated by an arbitrary formula using the screw rotation speed as a variable. good.
For example, if the set rotation speed candidate SR0 (%) and the back pressure lower limit value of the screw are set to BPX (%), and the back pressure lower limit value PBX is determined linearly with respect to the set rotation speed candidate SR0, the following equation 1 can be used.
BPX (%) = SR0 (%) × C1 ... Formula 1 C1: Arbitrary proportionality constant

Similarly, for example, assuming that the back pressure lower limit value candidate BP0 (%) and the set rotation speed SRX (%) of the screw, and the set rotation speed SRX is determined linearly with respect to the back pressure lower limit value candidate BP0, the following Equation 2 can be used.
SRX (%) = BP0 (%) × C2 … Second formula C2: Arbitrary proportionality constant

[Consideration of other conditions]
In selecting the back pressure lower limit value or the rotation speed upper limit value, the setting state of each electric heating wire heater of the cylinder 33 and the molding cycle time can be taken into consideration.
For example, if the setting temperature of the heating wire heater on the base side of the cylinder 33 is high, or if the molding cycle time is long, the screw is stopped for a long time from the completion of plasticization to the start of plasticization of the next shot. is the case. Thus, when the resin has enough time to receive the heat from the cylinder 33, the back pressure lower limit value may be lowered or the screw rotation number upper limit value may be increased.

[Utilization of AI]
Further, artificial intelligence (AI) may be utilized for the control unit 40 described above. In other words, the types of molding defects, the rate of occurrence, the degree of molding defects, and the like for molding conditions are linked and converted into data. The data is learned by AI, and when the AI determines that the set screw rotation speed candidate and the set back pressure candidate input by the molding operator to the control unit 40 are highly likely to cause molding defects, the input/display unit 47 display a message to that effect. In addition, it displays candidate rotation speed settings or candidate back pressure settings for which the AI has determined that molding defects are unlikely to occur. may be restricted.

[Application to extruder]
Further, for example, a screw 101 is rotatably arranged in a cylindrical plunger 103 inserted into a plunger barrel 105 as shown in FIG. Also known is an injection device that advances a plunger 103 and a screw 101 with respect to a plunger barrel 105 to inject molten resin material in the plunger barrel 105 . Further, in this case, the speed reducer 107 for the rotation of the screw 101 is an electric motor or a hydraulic drive through a known speed reducer such as a pulley and belt, a parallel shaft gear speed reducer, a helical speed reducer, a bevel gear speed reducer, and a hypoid speed reducer. An example of driving by a motor is known.

In the injection device shown in FIG. 9, the screw 101 is fixed to the plunger barrel 105 in the axial direction of the screw. does not occur. However, the screw in the actual extruder generally rotates at a higher speed than the screw in the injection device of the injection molding machine. When the screw of the injection device in the extruder is rotated at a high speed, the resin conveying speed in the cylinder becomes high as in the case of the occurrence of the screw phenomenon. Therefore, the restriction of the lower limit of the back pressure in the present invention is also effective in the injection device of the extruder.

1 injection device 10 support portion 11 bed 13 guide rail 20 driving portion 21 moving housing 23 electric motor 30 injection portion 31 screw 31A main body 31B screw shaft 31S outer peripheral surface 31T screw thread 33 cylinder 33S inner peripheral surface 34 inlet 35 injection nozzle 35A injection Hole 35B Resin passage 36 Support 36A Cylinder gripping hole 37 Passage 38 Material hopper 38
40 control unit 41 input/output unit 43 calculation unit 45 storage unit 47 input/display unit 47A rotation speed input field 47B back pressure input field 47C message field

Claims (7)

an injection section having a cylindrical cylinder and a screw rotatably arranged in the cylinder;
a rotating mechanism for rotating the screw;
A control unit that controls the operation of the rotation mechanism,
The control unit
Restricting the setting range of one or both of the screw rotation speed and the screw back pressure in the plasticizing process by matching the screw rotation speed and the screw back pressure with each other;
An injection device characterized by:
The control unit
As the setting range,
specifying one or both of a back pressure lower limit, which is the lower limit of the back pressure to which the screw receives, and a rotational speed upper limit, which is the upper limit of the rotational speed of the screw;
The injection device according to claim 1.
The control unit
Comparing the input setting screw rotation speed candidate with a single or multiple screw rotation speed range stored in advance in the control unit,
When the setting rotation speed candidate to be input is included in the stored screw rotation speed range,
specifying the back pressure lower limit value associated with the screw rotation speed range as the back pressure lower limit value of the setting range, and rejecting input of setting back pressure candidates smaller than the lower limit value;
3. The injection device according to claim 2.
The control unit
Comparing the input set back pressure candidate for the screw with one or more screw back pressure value ranges pre-stored in the control unit,
When the setting back pressure candidate to be input is included in the stored screw back pressure value range,
specifying the rotational speed upper limit value associated with the screw back pressure value range as the rotational speed upper limit value in the setting range, and not accepting input of a setting rotational speed candidate greater than the upper limit value;
The injection device according to claim 2 or 3.
The control unit
Formula 1 showing the correlation between the input screw set rotation speed candidate and the lower limit of back pressure, and Equation 2 showing the correlation between the input screw set back pressure candidate and the rotation speed upper limit. specifying one or both of the back pressure lower limit value and the rotational speed upper limit value by one or both;
input of one or both of the set back pressure candidate smaller than the back pressure lower limit value and the set rotation speed candidate larger than the rotation speed upper limit value not accepted;
3. The injection device according to claim 2.
The control unit
rejecting input of one or both of the set back pressure candidate smaller than the back pressure lower limit value and the set rotation speed candidate larger than the rotation speed upper limit value;
Prompting input of a new set back pressure candidate instead of the set back pressure candidate; and
Prompt to input a new set rotation speed candidate instead of the set rotation speed candidate,
The injection device according to any one of claims 3 to 5.
Limiting the setting range of the screw rotation speed or the back pressure by matching the screw rotation speed and the screw back pressure in the plasticizing process, which are the plasticization conditions of the injection device.
An injection method characterized by:

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